QST 1928-09: Vol 12 Iss 9

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eae Pas JAN 9 406 - * kaa SI "Wes DEVOTED ENTIRELY TO MATEUR, ADIO LEAGUE INC. . gs Une boxes. re best et 750 tapped tht 1 E. P Sold wards. ion, 9 rmer, ) volts ampli- , Box —— you've AHU, watt oO 7% 2V-16 20 to y 160 y one erials range, Ham onths, upply choke ; Tobe nteed ‘ville, ywing eters, bilier 1SOrs, drich many ; and Ohio. used. tube Ham W rite yet? satis- “isely vorth - full . GE ning ipere .002, Pure Send 1, 35 tting 55.10, ecto- 5.50, inum 5000 stals SEPTEMBER 1928

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| Precision... Vv FOR THE AMATEUR TO<) Frequency standardization and the development of frequency standards been a work of primary importance to the General Radio Company since its indation. Paralleling the precision standards designed for commercial labora- ies, low-priced instruments have been constantly produced to meet the in- easingly rigid requirements of amateur radio. Three types of meters are now vailable for specific uses in the Amateur spectrum. TYPE 558 AMATEUR BAND WAVEMETER The type 558 wavemeter is specific- ally designed for the new internation- al amateur wavelength bands. The coils cover only the wavelength bands actually assigned for amateur use. This feature permits spreading each band over the entire condenser scale, resulting in great accuracy of setting. The guaranteed precision of this in- trument is 0.25°:, the same as that of the Type 224 Precision wavemeter costing ten times as much. Coils are provided for the 5, 10, 20, 40 and 80 meter bands. Mounted calibration charts are supplied with the instru- ment, TYPE 558 WAVEMETER PUNO ccoss wseeee $20.00 AMATEUR WAVEMETER wavemeter covers a con- m 14 to 220 meters which f the bands open to Ama- is the experimental and mmercial bands. The great- instrument does not per- accuracy of calibration as the 558, the calibration 4 mounted calibration / AMATEUR WAVEMETER oe ‘ $15.00 METER WAVEMETER vavemeter covers only the 6.5 meters and is de- those experimenters who xtensively in this region to f other bands. The ac- bration is 1% A mounted supplied with each in- 8 WAVEMETER $8.00 GENERAL RADIO Write for new Bulletin No. 930 with direct to consumer prices You will find many items of interest. State St., Cambridge, Mass. 274 Brannan St., San Francisco, Calif.

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1.00 Jhe Official Organ of the ARRL a VOLUME XII SEPTEMBER 1928 NUMBER 9 Editorials ° . : , . ‘ ‘ ; ° ‘ , . ° . ° ‘ 7 Standard Frequency Transmissions from 9XL ‘ ‘ , ‘ , . ‘ ‘ S The Oscillator-Amplifier Transmitter ; . , : : : . Ross A. Hull 9 Radiovision , : . ‘ : , , . : Thornton P. Dewhirst 15 We Ought to Talk Frequency . . A , . ‘ 4 . ‘ " , ‘ 19 Hiram Opportunity Percy Maxim 24 Pacific Division Convention . : ‘ : . ‘ ‘ . . : . : 24 Adapting Medium and High-Powered Self-Excited Transmitters to 1929 Service , . . . ° . Ross A. Hull 25 The UX-860 . , ‘ ; ‘ . . . » % Harold P. Westman 31 The Zepp The Fifth Age . ‘ ' ‘ ‘ ‘ ° ° ° . ° . W. A. Adams 37 James J. Lamb Synchronism . ; ‘ , : ‘ . - P . ‘ C. Francis Jenkins 38 Remodeling the Traffic Tuner for 1929 . ° ° ° ; Harold P. Westman 39 Washington Developments . . ° ° ° . ° ' , . . ; 43 Experimenters’ Section ‘ ° ° ° ° ° ° ° * : . . . 46 Mica Condensers for High Frequency . : ‘ i : ‘ Arthur M. Troaner i7 Election Notices [: oe oD Calls Heard News Correspondence Book Reviews Financial Statement Indiana Central Division Convention . ° . ° ° ° ° . ° ° ‘ 80 England Ad New Division Convention Ham QRAs QST is published monthly by The American Radio Relay League, Inc., at Hartford, Conn., U. S. A. Additional entry as second-class matter, acceptable at s~ecial rate of postage provided for above, at Springfield, Mass.,. authorized Sevtember 17, 1924. | | Official Organ of the A.R.R.L. and the International Amateur Radio Union ‘ Kenneth B. Warner (Secretary, A.R.R.L.), F. Cheyney Beekley, } Editor-in-Chief and Business Manager Managing Edito- and Advertising Manager . Harold P. Westman, Ross A. Hull, David H. Houghton, Technical Editor Associate Technical Editor Circulation Manager Subscription rate in United States and Possessions, Canada, and all countriesin the American Fostal Union, $2.50 per year, postpaid. Single copies, 25 cents. Foreign countries notin American Postal Union, $3.00 per year, postpaid. Remittances should be by international! postal or express money order or bank draft negotiable in the U. S. and for an equivalent amount in U. S. funds. Entered as second-class matter May 29,1919, at the post office at Hartford, Connecticut, under the act of March 3, 1879. Accept- ance for mailing at special rate of postage provided for in section 1103, Act of October 3. 1917, authorized September 9, 1922. | | | Copyright 1928 by the American Radio Relay League, Inc.. Title registered at United States Patent Office. Member of the Radio Magazine Publishers’ Association.

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The American Radio Relay League The American Radio Relay League, Inc., is a non-commercial association of radio amateurs, bonded for the promotion of interest in amateur radio communication and experimentation, for the relay- ing of messages by radio, for the advancement of the radio art and of the public welfare, for the representation of the radio amateur in legislative matters, and for the maintenance of fraternalism and a high standard of conduct. It is an incorporated association without capital stock, chartered under the laws of Connecticut. Its affairs are governed by a Board of Directors, elected every two years by the general membership. The officers are elected or appointed by the Directors. The League is non- commercial and no one commercially engaged in the manufacture, sale or rental of radio apparatus is eligible to membership on its board. _ “Of, by and for the amateur”, it numbers within its ranks prac- tically every worth-while amateur in the world and has a history of glorious achievement as the standard-bearer in amateur affairs. Inquiries regarding membership are solicited. A bona fide in- terest in amateur radio is the only essential qualification; ownership of a transmitting station and knowledge of the code are not prere- quisite. Correspondence should be addressed to the Secretary. DIRECTORS ’ President Dakota Division Pacific Division IRAM PERCY MAXIM Cc. M. JANSKY, JR. ALLEN H. BABCOCK Drawer 2102, b llec. Eng., U. of M., 65 Market St., Hartford, Conn. Minneapolis, Minn. Southern Pacific Co., oe San Francisco Delta Division Vice-President BENJ. F. PAINTER a HARLES H. STEWA 424 Hamilton Nat’] Bank Bldg., ae es .—_— Chattanooga, Tenn. W. TREDWAY GRAVELY Hudson Division Danville, Va. dian General Manager B+ LAWRENCE J. DUNN gee 480 East 19th St. . oo tes 4. H. K. RUSSELL : ° Rocky Mountain Division 5 Mail Bidg., Brooklyn, N. Y. PAUL M. SEGAL Toronto, Ont. Midwest Division Box 1771 PORTER H. QUINBY Denver, Colo. 817 Lauderman Building, a itlantic Division St. Louis, Mo. Southeastern ~~~ EUGENE oe i Yr F. DOB { gy By — oe New England ere c 4 pad s Wey Co., State College, Pa. DR. ELLIOTT A. WHIT 245 Spring St., N. W., , Dartmouth College, Sioke Gin Hanover, N. H. sc att ‘ Central Division Northwestern Division West Gulf Division CLYDE E. DARR K. W. WEINGARTEN FRANK M. CORL Hill Ave., Highland Park, $219 No. 24th St., 2515 Catherine St., Detroit, Mich. Tacoma, Wash. Dallas, Tex. OFFICERS President ... ‘ H1rRAM Percy Maxim, Hartford,Conn. Vice-President . . . . . . CHAS. H. Stewart, St. David’s, Pa. Secretary ... . . « KENNETH B. WARNER, Hartford, Conn. Treasurer . . . . . . . ARTHUR A. HEBERT, Hartford, Conn. Communications Manager . . F. Epwarp HANpy, Hartford, Conn. \LL GENERAL CORRESPONDENCE TO THE EXECUTIVE HEADQUARTERS AT HARTFORD, CONN

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EDITORIALS N the spring of 1927 the Radio Division, Department of Commerce, abandoned the issuing of Amateur Fxtra First Grade Radio Operator Licenses because of the ap- parent lack of amateur interest. In the several years that this type of licenses was available only about 150 of them were is- sued. Immediately it was abandoned, great disappointment was expressed by amateurs, and during the year the feeling grew in amateur circles that we had not properly appreciated this recognition of the amateur by the Department and that we desired its reinstatement. By the time our Board met this spring there was a definite desire in amateur ranks to secure its restoration, and our Board accordingly petitioned the Radio Division. Now we are happy to announce that this grade of license has been reinsti- tuted, new blanks have been engraved, and all of the offices of the Radio Division throughout the country are prepared to issue them to amateur applicants. The offering of this superior grade of amateur operator’s license is a stimulus to amateur proficiency and achievement, and something in which great pride can be taken by the holder. In earlier days the quite capable amateur could establish his pro- ficiency by taking out a commercial license but there is to-day such a great difference between amateur equipment and commer- cial equipment, because of the now vast dif- ference in wavelengths and methods, that it is only infrequently that an amateur is able to pass the commercial examination, and only after special study for that purpose. And even then it does not indicate particu- larly his greater proficiency as an amateur. The new form of “ticket”, on the brown form, is distinctively an amateur license, and the providing of it by the Division is a pretty recognition of amateur radio. To be eligible for this examination the applicant must have had at least two years’ experience as a radio operator and must not have been penalized for violation of the radio laws— his record with the Radio Division must be clean. A speed of not less than 20 words per minute in Continental Morse receiving and transmitting must be attained, the same speed as for a commercial license. A special examination broader in scope than the regular amateur examination is given, with the requirement of 750%, as a passing mark. We wanted this grade of license restored. It has been done. It is now distinctly up to us to “patronize” it. Every amateur who can meet the requirements ought to undertake to possess himself of one of these licenses at the earliest possible date. It be- comes the distinguishing mark of the superior amateur. The Radio Division itself, and the military branches which offer ap- pointments to amateurs, will inevitably recognize it as such. It is a spur to indi- vidual achievement, something of which we may rightfully be proud. Let us show our appreciation of the Division’s kindness in restoring this special grade of license by giving them lots of “customers”. HIS business of monitoring all trans- missions from an amateur station, as is consistently recommended in Mr. Hull’s series of transmitting articles, is a most useful and valuable idea. It is nothing short of strange that we went so many years without doing it. Its necessity is now perfectly apparent. Most amateurs go along for years listen- ing to every signal in the world except those from their own transmitter, which should be the first ones they listen to! This failure undoubtedly is responsible for the poor notes one hears on the air. It may be demon- strated easily to anyone’s satisfaction that it is not possible to adjust any transmitter correctly, however good it is, by the use of meters alone. Adjustments for satisfac- tory output and for good efficiency are by no means sufficient, for in spite of these a good transmitter may still put out a signal of poor tone, chirping and creeping, infested with key clicks, and sensitive to every slight movement of the antenna. Yet all of these weaknesses are disclosed instantly by monitoring the transmission, so that one may know exactly what the signal sounds like to the distant station. When a monitor is used it becomes unnecessary to solicit numerous signal reports and attempt to secure some intelligent mean by discounting the over-enthusiastic ones and bolstering the ultra-conservative. What a _ tremendous amount of time and effort this saves, and what a vast amount of unnecessary inter- ference it removes from the air! The only thing a distant receiver can report to the operator of a monitored transmitter which the latter does not already know about his signals is their audibility at the receiving station. The 1929 station whose signal goes bad in quality or whose frequency begins to crawl, will be completely out of luck, lost in the méleé. Monitoring prevents this, for it is instantly known to the transmitting opera-

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ry amateur who desires to be suc- 1929 must arrange to monitor his etter from Mr. Shaw, published in month’s “Correspondence,” raises interesting points. In addition ng us new technical difficulties, the M Convention presents us with difications in operating procedure h several sets of entirely new ab- Like the rest of the convention, me effective on January lst. In ues QST will present all of this in- which has an amateur application. anges in operating procedure itself l and of course will be handled by unications Section in its codifica- ir Rules & Regulations. Then there ypler and much more sensible set y signals, a brand new and much tensive set of “Q” signals, and a xtensive list of one-, two- and three- bbreviations. All of these have internationally agreed and they ng upon all classes of stations, so must adopt them and become with them and drop our old ab- s at the end of this year. » stations are neither stations of ervice” nor of the “mobile serv- T 9 Standard Frequency Trans- missions from 9XL ~~ ION 9XL is a special station, com- ms ng one of the three portions of “Cold wcco— WI at ted as Medal Station”, Anoka, Minnesota. WCCO a broadcast station, 9XL a standard frequency station and a general amateur station, the ransmitters having independent and antennas but a common ipply. Through arrangements K. V. R. Lansingh of the Official ength Station Committee of the renters’ Section, A. R. R. L., 9XL is 1 on schedules regularly announced The work of operating the sta- lone without charge by Chief Oper- gh S. McCartney with the assist- Lyall K. Smith and Ivan H. Ander- n the staff of WCCO. no guarantee of accuracy is made ratis service, it is the aim of the maintain an accuracy of 1/10 of h is materially better than can be most frequency meters. The fre- are measured by means of stand- hich have been especially standard- T Ost SEPTEMBER, 1928 ice”. They are separately provided for as one of the classes of private experiment stations, and they have their own privileges and restrictions in the convention. All of this will be much better understood by studying a complete copy of the convention, which also includes, of course, all, of the abbreviations and tables mentioned. Really a copy should be in every amateur “shack.” A copy of the English translation of the document, known as “International Radio- telegraph Convention, Together With General Regulations and Supplementary Regulations Attached Thereto,” may be ob- tained from the Superintendent of Docu- ments, Government Printing Office, Wash- ington, for twenty-five cents. The prefix for a general call to all sta- tions has been changed from “QST” to “CQ” and the former is now a blank in the inter- national list of “Q” signals. That doesn’t mean that QST is going to change its name, though. If some uncomplimentary meaning had been assigned the letters “QST”, such as “You interfere with me—get out,” we might have to. But now that QST is left blank in the international list, it becomes exclusively the name of a good amateur magazine. x. B. W. ized for this purpose by the Bureau of Standards. A small percentage of tone modulation is employed so that the signal is distinctive and more quickly recognizable. The fact that this service has been ren- dered in the past is no guarantee of its continuing indefinitely in the future. It depends upon whether the response re- ceived seems to warrant the amount of work and expense involved in maintaining this free service to all amateurs. If you take advantage of this service, please ac- knowledge that you are doing so by noti- fying the Experimenters’ Section, A.R.R.L., 1711 Park Street, Hartford, Conn. You may use ordinary stationery or special! blanks that may be obtained from the above address. A goodly number of these blanks has been gathered and as the num- ber grows we will gradually gain a unique and accurate record of transmission phenomena possit'e with no other station. SCHEDULES (Figures are frequencies in MEGA- CYCLES per second; approximate wave- length is given in parentheses.) (Continued on Page 32)

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1928 or as iment lleges Ll of d by ntion, f the eally ack.” f the adio- With ntary e ob- Jocu- J ash- sta- ‘CQ” nter- esn’t ame, ning such ? we left ymes iteur W. of ition ‘tive ren- its It of ling you oti- SEPTEMBER, 1928 OST © The Oscillator-Amplifier Transmitter A Practical Study of Its Suitability for 1929 Operation By Ross A. Hull* 1929 service. in the August, QST. mitters. tion. Here is a real “1929 transmitter.""—Editor. The first activities on the A.R.R.L. Technical Development Program, in the examination of 1929 difficulties, have been studies of the possible methods of adapting present-day transmitters for The first resulting article, reporting the work on self-excited transmitters, appeared The second phase of the work has been on master-oscillator-amplifier trans- In this article Mr. Hull, the director of the program, presents the results of this examina- URING the last two years, in par- ticular, master-oscillator-amplifier transmitters have been given bril- liant and comprehensive treatment in QST. A study of the articles included in the appended bibliography would pro- vide the amateur not only with a splendid idea of the op- that could be expected under normal con- ditions. These are the matters, therefore, to which we will give our attention. “OSCILLATOR-OSCILLATOR” TRANSMITTER We recall, five or six years ago, the con- struction of an elaborate master-oscillator- amplifier trans- eration of these circuits, but also with com- plete construc- tional details of several types of practical trans- mitters. In view of the existence of this material, we do not pro- pose to treat mitter. We knew that such a transmitter would give steady signals of splendid char- acter, and as a result we were not surprised to obtain some ex- cellent reports during the first the history of few QSO’s. We the circuits, the recall as_ well, theory of their however, that operation or shortly after- even the rea- 4 LOW-POWERED OSCILLATOR-AMPLIFIER TRANS- wards, the sons behind MITTER WITH A “1929 TYPE” PERFORMANCE transmitter was their peculiar ef- fectiveness, un- less such treat- ment is involved in the consid- eration of their application to the solution of next year’s problems. The objectives in our examination of ma@ster-oscillator-amplifier transmitters were to study the conventional circuits; to build one into a transmitter in the way that the average amateur would build it; to tune it with the care that the average amateur would take, and then to measure its performance. In this way we hoped to be able to gain some idea of the relative desirability of oscillator-amplifier and self- excited circuits in a general way. Our ob- jectives included also the construction of a somewhat refined transmitter; the pre- cise tuning of its circuits, and the measure- ment of what would then be something ap- proaching the best possible performance Editor, QST. In charge aluminum frequency will *Assoclate Technical A.R.R.L. Technical Development Program. The frequency being set by a High-C oscillator i container, and _ the remain practically amplifier operated well below its rating. within the Started up with amplifier being accurately the oscillator neutralized, the antenna can be shaken to the ground and the accidentally dis- constant. Differing from connected Be- crystal-control practice, the oscillator is a tube similar to the . hold! The an- tenna current was there just the same. Eventually, we were able to tune the thing properly but we were surprised to find that with the slightest misadjustment the performance would drop to that of a self-excited transmitter. Since that time, the development of effective neutralizing systems has. simplified the tuning business very greatly. It must be understood at the start that even in these enlightened days the use of a master-os- cillator-amplifier transmitter does not spell the end of swinging and creeping fre- quencies—that its use does not in any way eliminate the necessity of careful and ex- act tuning. The first transmitter built in the Lab- oratory for this study consisted of a UX- 171 oscillator using the Colpitts circuit, and supplied from 135 volts of “B” bat-

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ing a UX-210 amplifier powered )-vyolt generator. It was, as our ob- lictated, tuned without any particular oscillator was tuned to take 30 the amplifier bias was adjusted plate current of 70 m.a. was ob- normal operation. The amplifier : 7Sv. “HY > THE CIRCUIT USED FOR PRELIMINARY EXPERIMENT { the fixed condensers Cl and C2 in the High-C oscil- Their use was avoided in nd transmitter by the employment of the Hartley cir- Additional turns outside the amplifier nk were found necessary to make the neutralizing con- effective and for this reason the simple neutralizing hown in Fig. 2 was adopted. The grid leak Ri in = bias battery proved dangerous in practice, the om- ste current rising te enormous values when the oscil- detuned or when the amplifier grid excitation was re- k caused serious creeping. the oscillator. some other manner. tralized with its plate supply dis- by adjusting the neutraliz- nser until no energy could be OST an average transmitter, SEPTEMBER, 1928 switched on the “Growler” and listened. To our surprise we found that the note was poor, that the frequency was creeping bad- ly and that it responded to even slight vibration of the antenna. Further tuning adjustment was made with some consider- able improvement in performance but it was not found possible to obtain the same efficiency in the amplifier as that obtained in the self-excited oscil- lator described in last month’s QST. Plotting of the antenna-tuning-vs.- frequency characteristics showed that it was considerably better than that of the self-excited trans- mitter but on the other hand the plate-voltage-vs.-frequency curve was extremely poor. An increase of the oscillator plate voltage to 300 resulted in an enormous im- provement of the amplifier eff- ciency and measurement showed us that we had far surpassed the self-excited set in this regard. Un- der these conditions, however, the frequency creep was as much as 10 ke. per minute and the oscillator was therefore run alone until the cause of the trouble was found. A process of elimination placed the responsibility on the small fixed “bridge” condensers used across’. the oscillator inductance, which apparently were heating sufficiently to change their a ae | Wives THE TRANSMITTER WITH THE OSCILLATOR SHIELD REMOVED Mounted on an aluminum disk is the Hartley oscillator with a High-C tank. it fits the aluminum kettle. is mounted alongside the oscillator and between it and the antenna tuning unit. Over The amplifier unit, with a relatively Low-C plate tank, Glass rods are used to support the amplifier plate coil and the antenna coil, coupling be- tween them being varied by sliding the latter along the rods. The neutralizing con- denser—probably the most important control in the transmitter—is mounted between the oscillator and amplifier tuning condensers. the amplifier tank with an indi- wavemeter. At this time, we capacity appreciably. The replacement of these condensers with others of the air- a | roe mm | te Om Oe GTA ect Dm ct eee = @ at at as ete Ge a® atc at ot, tit» tip ii. ge pe

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ed. To e was z bad- slight uning isider- out it same ; that oscil- QST, g-vVs.- 10owed better rans- d the curve rease re to ; im- effi- owed 1 the Un- , the us 10 lator | the tL & the SEPTEMBER, 1928 dielectric type or the change to a Hartley circuit, fitted with an ordinary variable condenser, immediately reduced the creep- age to a low figure. The use of a UX-210 in place of the UX-171 resulted in still further improvement. MORE TROUBLES Other weaknesses in the performance were frequency wobbles due to vibration of the inductances and wiring, and violent frequency swings resulting from movements of the operator in the vicinity of the set. All of these matters were given consid- eration in the design and construc- tion of the second master-oscil- lator-amplifier transmitter pic- tured and described on these pages. Summing up our experiences we decided that the term, “master-os- cillator-amplifier” is not the synonym for constant frequency that it is so often thought to be —that the system is capable of producing extremely satisfactory FIG. 2. THE Ost 11 plugs and sockets shown in the photo- graphs. The amplifier, consisting of another UX- 210 arranged in a conventional circuit, was mounted with its associate apparatus in a group just clear of the oscillator. In the plate circuit of this tube a High-C tank was avoided in order to permit a high de- gree of efficiency without the necessity of any particular refinement of its construc- UX 210 v7 + 7 5¥ ~45V¥ +BiAS CIRCUIT OF THE TRANSMITTER ILLUS- TRATED ON THESE PAGES fixed the ntly heir of ir- signals, but that tuning plays just Cl, as much or more of a part than in the case of self-excited outfits. In the second transmitter, a UX-210 was used as the oscillator in a Hartley circuit, so avoiding the necessity of fixed “bridge” condensers. The mounting of the inductance and the wiring were made more substantial and the unit was assembled on an alumi- num disk over which an ordinary aluminum kettle could be inverted. The shield, so provided, was not intended to prevent undesired couplings between the oscillator and amplifier but merely to avoid the frequency changes due to body capacity variations. It proved thoroughly effective for this pur- pose though drill holes around the THE OSCILLATOR TANK A High-C tank was used for the oscilla- tor, the values of inductance and capacity being of the order of those found desirable in our previous study of self-excited oscil- The low power of the oscillator, induct- outside diameter copper With input power to the oscilla- tor of 10 or 12 watts it was not found neces- sary to use heavier conductor or more ef- fective contact than that provided by the lators. however, made it possible to use ances of 3/16” tubing. it was found necessary to bottom and at the top to provide ventilation. fore these holes were drilled serious fre- quency creeping was caused by the heating of the apparatus within the kettle. C2—500-uufd. receiver type variable condensers. C3—350-pufd. ditto. Ci—50-uufd. midget condenser. C5—2000-ppfd. fixed by-pass condenser. C6—1000-y.pfd. filament by-pass cordensers. C7—250-upufd. coupling condenser. C8—250-uufd. fixed oscillator grid condenser. C9—1000 unfd. oscillator stopping condenser. Ri—Center tap resistors—50-or 100-ohm resistors or Christmas tree lamps. R2—100-watt, 10,000-ohm grid leak used to drop plate voltage for oscillator. R.F.C.—Three sections each of 50 turns of 30 gauge d.c.c. wire wound in %” plots in a 1” former and connected in series. The usual tubular chokes should be equally satisfactory. Li, L2 and L3 are illustrated and described elsewhere. Various keying methods were used satisfactorily though their relative effectiveness has not, as yet, been studied. For the time being, we suggest that one of the many effective schemes which has been described in QST be employed. The adjustment of the grid clip GC will not be found critical. Satisfactory operation prob- ably will be obtained with one-quarter of the total turns between GC and the plate but experiment with other adjustments is desirable. tion. In the case of a correctly neutralized d amplifier tube, slight changes in the tube eh constants due to changes in the load or heating of the tube should have negligible effect on its performance and it is on ac- count of this fact that a High-C amplifier plate tank is not particularly desirable. With amplifier plate inductances of the sizes shown in the photograph, the tank currents were not high enough to justify the use of heavier conductor than that used in the oscillator, nor the use of more elab- orate connectors. In the antenna circuit, still lower currents are found and the same conductor was entirely suitable. In this second transmitter, a change was made in the neutralizing method (as can be seen by a comparison of Figs. 1 and 2) since it was found possible in the second method to avoid the necessity of turns ad- ditional to those included in the tank cir-

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This change, of course, considerably 1 the arrangement of the _ tank. ruction of the transmitter is quite in all other respects and it OSE-UP”" OF THE OSCILLATOR UNIT t of the tube is the grid leak and the grid from which the combined connecting strip mount is run to the variable condenser. A rrangement is used on the plate side of the the right side of the tube is the plate r.f. The filament by-pass condensers can be seen on the tube base in the immediate fore- be necessary to add to the in- 1 provided by the illustrations and ULTIMATE PERFORMANCE it that the transmitter is a dizzy mtraption but we must say that rmance was something very close lea of perfection, as soon as we tered its tuning. It could be left vith an automatic key for a couple (monitored with a crystal oscilla- thout a frequency drift of any seri- portion; it could have its plate (both oscillator and amplifier) with a frequency change that just observable; it could be | over” with both hands without r noticing it; it could give us a usical d.c. note” with the simplest formed so splendidly, as a matter that we dreamed that night of a 1 with master-oscillator-amplifier tters and Bourne acoustic filters. was a world of bliss! cannot leave those statements lacing in juxtaposition the claims ng is even more important in mas- r-amplifier transmitters than lf-excited sets and that the use of OST SEPTEMBER, 1928 a monitor or “Growler” for the work is of equivalent consequence. THE TUNING PROCESS In tuning the oscillator the same proce- dure will apply as that outlined for any self-excited transmitter. In tuning this os- cillator with the aid of a monitor, we found it desirable to do the work with the plate supply filter disconnected. In this way it was more readily possible to decide upon THE AMPLIFIER UNIT IN GREATER DETAIL The height not being limited by any shield, the tube, in this case, is mounted in a convenient position on brackets extending from the tuning condenser. Un- der the tube base is the plate circuit by-pass condenser and dropped from it is the filament by-pass unit. Pro- jecting to the left of the tube is the grid coupling condenser in the lead from the oscillator. the adjustments giving the cleanest note than when a well-filtered plate supply was used. In the adjustment of this particular transmitter, the generator was run with- out any filter and the adjustment was con- sidered satisfactory when the modulation of the note due to plate supply ripple had been reduced to the point where it could just be detected. While tuning the oscillator, it is well to have the grid lead to the amplifier attached, but the amplifier should be run with its plate supply disconnected, Just as soon as the oscillator has been adjusted to give the cleanest and steadiest signal on the re- quired frequency, with the input at about 10 watts, the preliminary neutralizing can then be undertaken. For this work, a two- turn coil connected to a flash lamp bulb should be coupled closely to the amplifier plate coil, and with the neutralizing con- denser set at zero, the plate tuning con- denser rotated until the maximum indica- tion is obtained in the bulb. At this stage,

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1928 k is of proce- or any shis os- } found > plate way it » upon note was ilar ith- on- . of rad uld to ed, its he re- ut SEPTEMBER, 1928 the neutralizing condenser should be ad- justed until no such indication is obtained even after a slight readjustment has been made with the amplifier plate tuning con- denser. The plate voltage to the ampli- fier can now be connected (the grid bias being at about 45 volts) and slight retun- ing of the amplifier plate tank can be made to reduce the amplifier plate current to the lowest value. Antenna coupling and tun- ing can now be effected, keeping in mind the fact that antenna coupling still plays the same important part in master-oscilla- tor-amplifier transmitters as far as_ ef- ficiency is concerned, and that it still has some influence over the performance as far as frequency stability is concerned. In short, when the coupling has been adjusted until maximum antenna or feeder current has been obtained, the coupling should be backed off until the antenna current is 7 FREQUENCY (Ke) -_ 40 4s rc) ss 60 ANTENNA TUNING (Scale Divisions) SHOWING THE EXTREME IMPORTANCE OF PRECISE NEUTRALIZATION In taking these curves the neutralizing capacity Cn was set at various values, denoted ,for convenience, by the dial readings. At each adjustment the An- tenna-tuning-vs.- Frequency curve was plotted. It can be seen from curves Cn 27 or Cn 32 that misad- justments of two or three degrees on a 500 ppufd. con- denser can lower the performance almost to that ef a self-excited transmitter. The correct adjustment in this particular case was somewhere between 29 and 30 degrees. With Cn at 29 the frequency swing was slightly upward while at 30 it was downward. If Cn could have been adjusted to about 29.3 the fre- quence change caused by tuning the’ antenna through resonance probably would have been not more than a few cycles and antenna swinging would then have had practically no influence on the frequency. FIG. 3. about 85% of its former value. Unlike the self-excited transmitters no noticeable im- provement was effected by detuning the antenna and any sacrifice of antenna cur- OST 13 rent other than that resulting from the loose coupling was not considered neces- sary. If the tuning has been followed in the monitor, the signal will probably be clean julia CS cr e e" OSCILLATOR, AMPLIFIER AND ANTENNA COILS FOR FOUR BANDS Made of 3/16” outside diameter copper tubing and wound by hand on a piece of iron pipe these coils serve for the four bands from 3,500 to 14,400 ke. in this particular transmitter. In a transmitter ar- ranged differently some changes in the dimensions given may be necessary. Coils Aa and Ao are the amplifier and oscillator coils for the 3,500 kc. band. They have an internal diameter of 2%”. Coils Ba and Bo are for the 7000 ke. band, Ca and Co for 14000 ke., and Da, Do for 28,000 ke. For the last three bands the coils are wound to have an inside diameter of 154”. Coil E is used in the antenna cir- cuit for 3500 ke., F for 7000 and 14000 ke. and G for 28000 ke. The number of turns used can seen on the illustration. Coil H, fitted with a flash-lamp bulb, is that used for the preliminary neutralizing process. o- 4 ¥ and extremely steady, but attention should be reverted to the neutralizing condenser for final adjustment. By listening to the trans- mitter with little or no plate-supply filter a magnificinet final adjustment of neutral- izing can be made. As the attainment of complete neutralization is approached, the character of the note will improve greatly, and at the exact point of neutralization it will be far superior to that obtained on either side. The point at which the note clears is, indeed, so well defined that we are now of the opinion that much more exact adjustment of neutralizing can be obtained by checking with the monitor than with any method so far attempted. We admit, however, that the method previous- ly mentioned (or a similar one) is indis- pensable in providing the approximate ad- justment, since the monitor method can be put into use only when the transmitter is operating in a somewhat normal fashion. In all of our experimental work we found

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tha of ¢ cal gre In this set tank quen a con ly h ward tween desira appr given whict amp! with scribed mit matt tain inv justifi opera Frequen apacity nenemes swing was upward. ser setting one degree higher, resonance clear- then passed and the frequency swing was down- t appears from the curves that a setting be- 0 and n the August QST. on of the performance of the two trans- compar ent-day adjustment of neutralizing was me importance . In every case, it aid without exaggeration, a 10-de- vement of the 50-uufd. neutralizing ANTENNA CURRENT (AMPS) ao 4s 50 3s 60 65 ANTENNA TUNING (Seale Divisrons) *RAPHICAL INDICATION THAT DETUN- ING OF THE AMPLIFIER PLATE TANK ACTUALLY IMPAIRS PERFORMANCE ase the amplifier plate tank capacity Ca was various values and an Antenna-tuning-vs.- curve plotted for each. In Curve A the was slightly below that required for at the oscillator frequency, and the fre- In Curve B, taken with 51 degrees would have produced that condition in which antenna tuning has no effect on frequency. The dark curve is denote the antenna tuning adjustment at antenna circuit was in resonance with the plate tank. The dashed curve C was taken low-powered self-excited transmitter de- It is given te provide a * spelled the difference between a a 1929 type signal. NSMITTERS OF HIGHER POWER the time set apart for this study master-oscillator-amplifier ters did not permit the construc- a higher-powered transmitter, we no reason why the same general uld not hold good. The choice of llator and amplifier tubes will be a f greatest importance for it is cer- our minds, that the complications |! in a master oscillator will not be unless the input of the oscillator, ne at normal efficiency, is at least OST SEPTEMBER, 1928 one sixth of the ampliefir input—the two tubes working on the same frequency—and unless the oscillator is being run well un- der its rating. This means that a UV- 203-A or a UX-852 would be the only tubes suited for use as an oscillator controlling a tube of the latter type, while a UX-852 would be required to control a UV-204-A. It is not claimed, of course, that these com- binations alone would prove satisfactory. It is merely suggested that under average conditions they would be very desirable. In case this statement of master-oscilla- tor and amplifier ratings would not appear to be checked by general crystal-control practice, it might be well to explain that conditions in the two instances are not by any means parallel. In the crystal-con- trol transmitter the work of the oscillator is merely to supply sufficient excitation for the succeeding amplifier tube. In the case of the master oscillator (the term is used on account of its convenience but they are really both master oscillators) its work is to supply the amplifier excitation in a sim- ilar manner but to do the work without changing its frequency in accordance with any minor fluctuations of the load on it. In the crystal oscillator the crystal takes care of any such changes but in the master oscillator a stable frequency can _ be ob- tained in a practical manner only by mak- ing the energy drawn from it for amplifier excitation a fraction of the total radio fre- quency energy being developed. We like the master-oscillator-amplifier transmitter. Its complications are minor; its tuning is straightforward; its perform- ance, we’ll tell the cross-eyed world is well- nigh supreme. a 7 = Recent QST articles treating the Oscil- lator-Amplifier Transmitter: Master Oscillators and Power Amplifiers (Kruse) March, 1927 A Constant Frequency (Hoffman) July, 1927 A Low-Power Master-Oscillator Trans- mitter (Dudley) Feb., 1928 Keying Master-Oscillator Circuits (Dud- ley) April, 1928 Transmitter BUX THE ONLY U.S HAM WHO NEVER HRD A FOREIGN STATION

Page 13

two ~and un- UV. ubes lling -852 A. It -om- Ory. rage illa- year trol that ; by con- ator for ‘ase ised are t is im- out rith it. kes ter ob- ak- ier re- ier oT; s}]- SEPTEMBER, 1928 OST Radiovision By Thornton P. Dewhirst’ F LATE there has been considerable publicity concerning radiovision or television and the reception of such signals by the amateur and experi- menter. There has been but little informa- tion in a form suitable for the amateur and it is the object of this article to give some pointers on the problem and show some of the limitations of the art in its existing state. First of all, do not expect too much from your radiovision investment. A picture of only slight detail is possible when recep- tion is to be accomplished on the present broadcast set and the transmitter is to stay within the ordinary assigned channels of today. The use of present-day channels limits the number of lines drawn per pic- ture to approximately 24. This means that the bust of a single person is about the limit of recognizable reproduction in half tone work and that possibly two moving figures in silhouette may be accomplished at the most. However, let us go into de- tail about the apparatus proper and return to this phase of the subject when we have acquired a little more data concerning the methods of transmission and reception. By means of a revolving disc at the transmitter, the object is scanned by a spot of light, the reflection of which is picked up by a bank of photo-electric cells and these electrical impulses so generated are used to modulate the carrier wave. At the receiving end we have another disc re- volving in synchronism and the radio signal is employed to illuminate a lamp which is viewed through the disc. The number of holes in the disc will determine the number of lines per picture and the speed of the disc will determine the number of pictures trans- mitted each second; both of these factors are set by the transmitter. In the case of the 24-line picture as trans- mitted by WGY, there is not much that need be said. These pictures may be re- ceived on the standard broadcast receiver providing a good audio-frequency amplifier is being used and the radio frequency end is such that the full 10-kce. band is passed. For reception of the 48-line pictures, the story is quite a bit different. Unless your present receiver uses a tuned r.f. amplifier with separate controls for each stage, and the audio amplifier will pass an extremely wide range of frequencies, it will be neces- sary to use a specially constructed set. Let us take the case of a 24-line picture. *Radio Consultant, 4909 7th Street, N. W.. Washington, D. C. Consider that each line is divided up into 24 separate elementary portions which means that for the whole picture we have 24 x 24 or 576 elementary areas that are being scanned by the beam of light. Now, if 20 pictures are being sent each second, each elementary area giving a_ large change in illumination compared with its 2 of ytd Hs bf ~- A Hel 2000-5000 ohms a lamp 150,000 onms Jafaefala 300 to 450 volts. +180 FIG. 1 immediate neighbors, the maximum fre- quency being transmitted will be 576 x 20 = 11,520 impulses per second. These im- pulses are uni-directional and two pulses would be equivalent to one cycle, which means that the equivalent frequency is half of this value or 5,760 cycles per second. In actual transmission of half tones, the change of illumination will not occur abruptly nor will there be a change for each elementary area. This results in the highest frequency being still further low- ered so that if the amplifier will pass fre- quencies up to 5000 cycles, it will be satis- factory for the job. When silhouettes are being transmitted, the changes in illumina- tion are apt to be more rapid and abrupt, resulting in a larger band of frequencies that must be passed by the system. To compensate for this, when receiving (or transmitting) silhouettes, the amplifier does not have to have as excellent frequency response characteristics as when half tones are being received, because in sil- houettes we are interested in but two values of illumination, light and dark; whereas in half tones, the various shades between these values must be considered. A 36-line picture sent 10 times per sec- ond will require a band but slightly wider than the 24-line, 20-per-second transmis- sion. However, since the number of times a second a picture must be repeated in order that the phenomenon of persistence of vision be obtained is also a function of the intensity of the illumination, it can be appreciated that in order to obtain a steady smooth image using the above speed, a light source of considerable intrinsic bril- liancy will be required. The stronger the

Page 14

4] fewer pictures per second neces- ybtain persistence of vision provid- peed is not reduced to a point ker is introduced. About 15 pic- r second is the slowest speed ad- line picture sent 15 times per second uire about 20 kes. for each side about four present-day channels. work, receivers must differ con- y from those employed for present- ideast reception. One stunt is to r channels for this transmission, the picture up into four parts, which is handled by a separate tter and receiver. type of audio amplifier for the | be a resistance-coupled affair. High of the “240 type” may be em- nd the plate resistors should be of 150,000 ohms (somewhere between and 250,000 ohms will be about he coupling condenser around .1 ufd. grid leak, % megohms. These last CA changed somewhat although it remembered that as the coupling is made larger, the grid leak must be reduced. If the con- too small, the low frequencies will mplified while if it is too large, the have to be reduced to a point amplification of all frequencies 1 or the tube blocks. About 180 f B-battery will be needed for the tage of resistance-coupled amplifi- -" then depend only upon the amount output signal is approximately s out of phase in relation to the al. The number of stages needed ecessary but also upon the fact image is to be a positive and not tive one. Whether there shall be even number of stages will de- n whether the transmission is of or positive picture. When the number of stages has been found en transmission so that the pic- ved is a positive one, additional ist be added in pairs so as to re- phase relation. The grid bias adjusted with care. When re- alf tone pictures, adjust as for rnals while if silhouettes are to ed, the bias should be slightly in- of the grid bias method of de- to be recommended in preference and condenser system. While ivity will be reduced, the amount tion will also be reduced, resulting atisfactory operation. Changing type of detection to the other cause a shift in the phase rela- e output. An r.f. choke may be tween the plate circuit of the de- OST SEPTEMBER, 1928 tector and the grid circuit of the first am- plifier to prevent the r.f. that gets by the ao from loading up the audio ampli- er. The neon lamp should have a plate or target that is as large as the picture we wish to reproduce. This is necessary since we want to look directly at the lamp through the holes in the disc. The use of small lamps is not recommended as there is considerable improvement in the use of a lamp with a plate or target of ample proportions (about 1% inches square). These may be readily obtained and are well worth the additional expense entailed. It is connected in the plate circuit of the last stage of the amplifier. This stage may consist of a 210 or a pair of 171’s in paral- lel. See Figure 1. The resistance of the lamp before it is ignited is infinite but after it has been ig- nited, its resistance is quite low, varying from several thousand to ten or twenty thousand ohms depending upon the amount of current passing through it. The volt- age drop across the lamp is constant, its resistance varying in inverse proportion to the current flowing through it while the illumination is proportional to the current flow. In testing a lamp by connecting it across a battery, a.c. line, etcetera, it is essential that a resistance of a few thou- sand ohms be connected in the circuit or the target is liable to volatilize and render the lamp inoperative for this particular type of work. The resistor will control the amount of current that can flow and pre- vent this sort of breakdown. The radio frequency amplifier offers more of a problem than does the audio system. When the width of the side bands is not much greater than the present day broad- cast channels, it is possible to take a tuned radio frequency amplifier (the stages being tunable separately) and by adjusting the circuits slightly off tune with each other, the width of the band can be increased al- though the gain is reduced. A step further in this line is the method described by Dr. F. K. Vreeland in his paper which appeared in the March, 1928, issue of the Proceedings of the Institute of Radio Engineers. He uses two tuned circuits loosely coupled by either an in- ductance or capacitance so as to resolve all the resonance curves into one with flat top and steep sides. It is in effect an ad- justable band-pass filter. Such filters may be used either before or after the untuned amplifier stages or they may be employed as the coupling devices between the am- plifier tubes. One may also use a double-detection re- ceiver (superhet) and insert a fixed band- pass filter between the first detector and first intermediate frequency amplifier or ee -_ Lh shhh te nh ona at a

Page 15

SEPTEMBER, 1928 the filter may be inserted somewhere be- tween that point and the second detector. Synchronization is a problem of consid- erable magnitude and has not been solved to date. There have been many solutions offered but in the majority of cases, they have been too expensive for general adap- tion. Present practise is to use a series or shunt wound motor and by means of a resistor in the field circuit or in series with the line, adjust the speed to the desired value. To determine the required speed, multi- ply the number of pictures per second by sixty, the product being in r.p.m. If you already have a revolution counter it will help you arrive at approximately the cor- rect speed although if you have not one, it is not necessary to get one as after several trials you will find the approximate settings of the resistors for a given speed. Assum- ing everything else in working shape, as you approach the correct speed, the image will appear, although in distorted shape. If the image is continuously traveling up or down it indicates that either the speed is incorrect or not constant. If the image remains stationary but is not properly framed, the receiving disc is out of phase with the transmitting disc. This may be corrected by moving the lamp to a different part of the disc, dropping the motor speed a fraction of a revolution if possible or rotating the field of the motor. The size of the disc depends upon the number of holes and the width of the pic- ture. The distance between the outermost hole and the center may be calculated by the following: distance = number of holes X width of picture 2x height of picture size of holes = number of holes For best results the size of the picture should be determined by the size of the target in the neon lamp. Assuming a 1% inch square target, a 24-line picture re- quires a disc with a radius of approximately six inches while a 48-line picture would call for a twelve inch radius. In laying out the spiral one can make use of a piece of drill rod or dowell, the circumference of which is the same as the height of the picture. By placing it at the center of the disc with a piece of string or wire tied firmly to it, a marker fastened to this string about 4%” from the edge of the disc will inscribe the desired spiral as it is rotated about the center. In speaking of the spiral one might refer to the dis- OST 17 tance between holes as the separation of the holes and the height of the picture or distance between the first line and the last line as the offset of the spiral. When using the disc method of trans- mission very little in the way of refinement seems possible due to the huge size of the dise if better pictures are to be achieved. Mechanical improvements must be made osputds : iL , i oF i 5 Megs low mu s tube L tT FIG. 2 and one method patented by Ramsey is to continue the spiral on around gradually approaching the center of the disc. Each complete turn of the spiral has its own lamp which in turn is operated from a separate transmitting channel or a switch is provided to light the individual lamps in succession. This produces a larger pic- ture than a given disc could normally ac- commodate. If the spiral is of two com- plete turns, the separation of the holes will be twice the spiral offset and two lamps will be needed. The switching de- vice causes irregularities in contact which is important in half tone work and the sparking produced causes radio interference to the receiver. This may be partially reduced by switching ahead of the output tube and providing an output tube for each lamp. Jenkins uses a number of helices drilled in a cylinder, each helix being illuminated by an individual target in a multi-target lamp similar to the manner in which Ram- sey illuminates several spirals on a disc. Jenkins places the multi-target lamp at the center of the cylinder and by the use of quartz rods conducts the light to the periphery of the cylinder with very little loss. The individual targets of the lamp are small and thus a given amount of energy will produce a large amount of illumination. It is confronted with the same drawbacks as regards switching as is the Ramsey system. Ramsey’s method produced a gradual narrowing of the width of the image as the spiral approaches the center of the disc while the other produces a fading out of the image at the edges. The first may be corrected by proper framing and pro- viding that care is exercised at the trans- mitter, no distortion will be caused. In

Page 16

te% wil on one Wat 94 } gt Vi nder e P.E. where the voltage is just below the area method, a lens will correct fficulty to some extent. lise can be used for both transmit- | receiving at the same time by ling the spiral a quarter turn more. i-line picture, lay out six more ——+1) Neon lamp er the full spiral has been made the 48-line disc there should be additional holes. The picture is to eived one quarter of the circumfer- ym the point where it is transmit- photo-electric cell (abbreviated 2 light source and a few more stages plification will be needed. The num- eded will depend upon the number to the picture and the intensity of t source. At least a 500-watt lamp light should be employed. The arc t be run from an alternating cur- irce as the variations due to the a.c. 60 cycles) which are relatively slow dulate the signal and cause trouble. nnections to the P.E. cell are n Fig. 2. The resistance in series cell will vary between three and It has been found advisable low mu tube as the input tube > be followed by high mu tubes in of the amplifier. It would per- best to start with silhouettes since cell may be adjusted at a ausing the cell to glow when the t light is on it for the longest time For half tone work, the cell worked down on its characteristic here a linear relationship exists be- umination and response. Under ynditions more amplification will be Figure 3 shows the general ar- for transmitting and receiving ame dise. Try placing a key, small r, fingers, etcetera in the lighted see the outline of these objects in ving area. Next, a photographic ferably a positive, may be tried. this has grown to be “old stuff” n try putting the signal on a carrier e picked up at a distance. With the cture the transmitter may be any ne set. However, it must be good ost SEPTEMBER, 1928 and there should be no a.c. hum in the car- rier and the complete audio spectrum to about 5000 cycles should be transmitted without much distortion. Few of the pres- ent-day amateur phones will pass this test and the first step toward this type of trans- mission should be a thorough housecleaning of the phone set. It is useless to attempt the work with a poor transmitter. The disc with the extra holes may be used and the receiving area employed for monitoring the signal. After you have done satisfactory work with the 24-line pictures, you can try transmitting a 36- or 48-line one. This transmission and reception prob- lem should keep you employed for some time. The use of the cathode ray tube for the receiver is worthy of consideration since it opens up the possibility of real radio- vision. In this tube, a stream of electrons may be moved in two directions at right angles to each other by means of either an electric field or a magnetic field. The win- dow of the tube is covered with a fluores- cent material and the electrons upon strik- ing it cause it to glow. By means of proper values of current or voltage and frequency, the small spot of light can be made to completely cover the window. For radiovision work, the use of a material for coating the window that was not only flourescent (emits light when exposed to certain rays) but also continues to glow for a short period after the ray has been removed would be of material assistance. This will help in causing the vision to per- sist and thus give the effect of greater il- lumination as far as this characteristic is concerned. Radiovision for the home is still in the very distant future and this constant hood- winking of the public should cease. The ra- dio industry will benefit enormously when it does. When the elementary area used to build up our picture bears the same proportion to the whole picture that the individual particles of the emulsion of the moving picture bears to the total number of par- ticles in the exposure and some method of transmitting each of the individual parts with ease and the problem of synchronism has been completely and simply solved, radiovision will be ready for the public. Today it is merely a plaything for the amateur and experimenter. It is an in- teresting field of experiment but one should not expect too much from his present day equipment. : trays A certain ingenious fifth district amateur has trained his parrot to yell “CQ”. He had an automatic CQ disk for his telegrapb transmitter but his ‘phone set was wanting ee mm et en ee tO Ot OO Set OR

Page 17

1928 ie car- um to mitted _~ipres- is test trans- aning tempt ay be d for done tures, 8-line prob- some r the since adio- trons right r an win- ores- trik- of and 1 be For for only 1 to rlow een nce. er- - il- » is the od- ra- 1 it ild ion ual ng ar- of rts 7m od, ic. he n- ld iy a ie » i SEPTEMBER, 1928 OST 19 We Ought to Talk Frequency The Reasons Why, Including a Look at Our 1929 Bands spoke in terms of kilocycles instead of wavelength in meters. All of the rest of the world has changed. By the terms of the Washington Convention of 1927 the primary standard in all assignments to radio stations is to be frequency, and it will be in terms of frequency that all of our amateur assignments are made. The term wavelength is such an inconvenient one, and so far-fetched as far as concerns the physical appearance of anything in a station, that it seems the sooner we forget all about it the easier it will be for us to figure things out. Electricity in general got off on the wrong foot a good many years ago when it started talking about a current flowing from positive to negative, only to discover in more recent years that the motion which occurs is that of electrons moving from what we call negative to what we call positive. Everybody knows how much trouble that dual conception has |: is time that amateur radio thought and caused. It seems to us that this business of wavelength in meters is equally left- handed. There are a number of excellent reasons why the International Radiotelegraph Con- ference decided to express its allocations in terms of frequency instead of wavelength, and numerous very excellent reasons why we amateurs must now convert ourselves into thinking in terms of kilocycles. Let us examine a few of these reasons. In the first place, talk about wavelength is “the bunk” because it is a thing that cannot very well be measured. When we talk about the length of our radiated waves we mean, for example, that if we had an oscillator going at about 7,500,000 cycles per second, and coupled to an antenna, and then if, Joshua-like, we could command those waves to stand still, and then if we could see them, and then if we had a nice steel tape-line whose accuracy we could rely ab- solutely upon, and then if we measured these waves and found that it were 131 feet and 3 inches from a point in one wave to exactly a similar point in another wave, then our transmitter would be operating upon ap- proximately 40 meters! Now we can’t see the waves, and we can’t stop them and have the same conditions that apply when they are radiating, and we can’t rely too much upon our measuring sticks. The one thing that the world does have absolutely ac- curately is time, and it also has the ability to count, and the one thing which may be said with precision about our circuit is the number of times per second which it oscil- Is it not ridiculous that we continue lates. to talk in terms evolved from as far around the bush as wavelength in meters? It is perfectly easy to think in terms of frequency and to see why this is logical. Consider the simple oscillating circuit of Figure 1 and imagine that the condenser, C, has been charged by impressing a voltage across it. Seeking to equalize the difference =~ Cc L aS L L c ~S FIG.1 FIG.2 FIG.3 in potential between the condenser plates, a current starts to flow, say in the direction of the heavy arrow. This current has to thread its way through the inductance, L, in which process it encounters electrical inertia because the inductance tends to pre- vent the flow of the current by taking up on power in the form of an electromagnetic field. Eventually all the power in the cir- cuit exists in the form of these electromag- negtic lines of force around the coil, instead of in the form of electrostatic lines of force in the condenser, as had been the case an instant before, and current flow ceases. But when the current through the coil ceases, the field around it collapses and the energy is returned to the circuit to proceed and charge the condenser, and in fact this same quality of inertia in the inductance now gives the current a “push,” so that the condenser in- stead of merely having its charge neutral- ized, is now charged in the reverse of its original direction. The current now starts back in the direction of the light arrow and the same performance occurs again, this action continuing until the power is re- duced below a certain critical value by losses from heating or radiation. This is simply the customary story of oscillation in an LC circuit, as is related in any radio textbook. Now the one thing which is perfectly obvious about this procedure is that if the inductance L is a large inductance like that in Figure 2 it will take the current a longer time to thread its way through the circuit, and if the capacity C, as in Figure 2, is a large condenser, it will take a longer time for it to become charged. “Electricity” having a constant velocity, it is immediately apparent that this circut is going to take a longer time to go through one coniplete

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elocity, divided by the OST nditions (a cycle) than a circuit like , in which both the inductance L e capacity C are small. We have said past that the circuit of Figure 2 has r wavelength in meters than that of } but we don’t actually know how s this left-handed measurement * particular accuracy and the chief we do know about Figure 2 is takes longer to oscillate, has a time-constant, oscillates more slow- lower frequency in cycles per We can measure that because, from y, we know exactly how long a Is it not easier to deal with the rect and obvious feature in the cir- rapidity with which it goes through ; consider another example of the bility of attempting to deal in meters elength. We say that the velocity waves is 300,000 kilometers per the same as that of light. Obviously frequency, give the wavelength. Our circuit ‘illated 7,500,000 times per second ut to have a wavelength of exactly rs. And this is dead right if we know velocity is 300,000 kilometers per Unfortunately we don’t know any- * the sort, even though that figure is cited for this purpose. As a f fact, that figure is known to be t incorrect and the latest scientific s attribute to this figure the value 10 kilometers per second. Our wave- w turns out to be 39.98 meters! right? Unfortunately we don’t Some day science will set a still irate figure for the velocity of our and then we will have still another ment for our wavelength. All we can ’ is that it is impossible for many t dark reasons to give a wavelength y but that we are able to state our with precision. For this reason ns of the world have now agreed operating privilege to all radio vill be stated primarily in terms of , the approximate wavelength in » be stated as a secondary value, the frequency to be hewn to the letting the meters fall where they other reasons why the term- - wavelength is outgrown for us Some of our 1929 bands are only r so wide and any attempt to wavelength within such bands is 1 meaningless unless it is carried ten-thousandth part of a meter. r to talk whole numbers in fre- We know that we must learn greater for next year and that we must recognize and discriminate be- juency differences of, say, 10,000 SEPTEMBER, 1928 cycles (10 kilocycles) in our 40-meter band. Yet how can we deal in meters of wavelength with the two frequencies 7250 kilocycles and 7260 kilocycles when we think of them as being exactly the same thing, namely, “right around 41.3 meters”? Answer: we can’t! One more reason. Any intelligent ex- amination of the capabilities of our various bands involves consideration of the number of stations which each will accommodate, which number varies with the frequency and in each case is to be expressed only in terms of width of channels, which again must be related to some percentage of the frequency. More about this later. For these various reasons it is apparent that we amateurs ought now to abandon our outgrown wavelength nomenclature and get on the band-wagon and talk frequency. The standard way of doing this is to speak in terms of kilocycles per second, common- ly called just kilocycles, and abbreviated “ke.” A kilocycle is a thousand cycles, which is to say that the actual frequency of an oscillator is to be divided by 1,000 to give the frequency in kilocycles. For example, our 40-meter oscillator which we said oscil- lated 7,500,000 times per second has a fre- quency of 7,500 kilocycles per second or 7500 ke. QST is going to lead the way in this. Frankly, we find ourselves unable to ex- press 1929 thoughts lucidly in terms of wave- lengths and we know that all of us simply must get around to talking frequency to be able to deal intelligently with next year’s activities. QST therefore is going to talk frequency. We will follow such references with the approximate wavelength in meters, in parentheses, the wavelength being based on the velocity 300,000 kilometers per second. Since frequency is the primary standard and wavelength at best an approximation, the basing of the wavelength exprassion on 300,000 is near enough accurate and ever so much more convenient than the figure 299,820. That also is exactly the practice of the International Radiotelegraph Conven- tion and of our own Federal Radio Commis- sion and Radio Division, Department of Commerce. For the small sum of 5c (stamps not accepted) the Superintendent of Docu- ments, Government Printing Office, Wash- ington, will send you a copy of the “Kilo- cycle-Meter Convention Table,” based on the figure 300,000, which was published on March Ist of this year. It is a large card, 13” by 23”, containing 60 columns of figures, and its examination will provide a profit- able pastime for nights when static is bad. The Headquarters “gang” is now pretty generally thinking and talking in terms of kilocyecles and we find it much more under- standable and easy to deal with. The story is told that one of the later members of the Federal Radio Commission did not a. a_i

Page 19

- band, length es and em as “right can’t! it ex- arious imber odate, y and terms ist be lency. arent indon e and ency. peak mon- lated trhich f an give nple, seil- fre- 1 or this. ex- ave- ply » be ar’s talk Ices ers, sed ynd. and the ver ure ‘ice en- is- ps u- lo- he on - Ss, it- ty of r- rT ot SEPTEMBER, 1928 know much about technical radio and, shortly before some extensive hearings were held, received some elementary instruction in the basic theory. Of course it was all in terms of kilocycles. At the hearings one of the speakers referred frequently to wavelength Ost 21 each station might be permitted to deviate a certain small percentage on either side of its assigned frequency. Suppose the de- viation is 0.1 percent; then let us assume that, in the commercial bands, there should be a space of one kilocycle on either side of AMATEUR FREQUENCY BANDS assigned by The Washington Convention of 1927 . , _ | Harmonic fami Kilocycles Width in Assignment Approx. Meters | Meters on basis | £o7,£23*S5?.2),.6 | Amateur Kilocycles on basis factor3| factor 2.998 Kilocycles| Met Purpose Amateur, Mobi/e, : 1715-2000 | 285 | ‘point-to-point 150 —175 |149.9-174.8 | 1775 |168.92| Domestic 3500-4000 | 500 ” ” 715 -85.7 | 74.96-85.66 | 3550 | 84.46 ” — ] _ + 7000-7300 | 300 | Amateur fxclusively | 41.1-42.9 | 41.07 - 42.83 | T100 [42.23 hight 14,000-14,400 | 400 " " 20.83-21.43 | 20.82-21.42 |14,200] 21.11 ~~ 28000-30,000 | 2000 |Amoteurd Experimental | 10.00- 10.11 | 9.99 -10.71 |28,400 |10.56 | Experimental 56,000-60,000 | 4000 ” ” 5.00-5.36 | 4.997-5.354 |56,800] 5.28 ” FIG. 4 in meters. “What does he mean, wave-_ this signal, to minimize the possibilities of length?”, said the member, leaning over to- wards a friend. “I never heard of it. Why doesn’t he talk kilocycles ?” How much happier we’d all be if we had never heard of meters! A LOOK AT OUR 1929 BANDS Let us now examine the bands which will be available for amateur radio after the end of this year. Figure 4 shows the assign- ments, the width of each band in kilocycles, and the approximate location of each band in terms of wavelength in meters. From this table, which band would you say was the “widest”? If we speak in terms of the number of stations which can be accommodated in any band we get quite a jolt when we discover that neither that band 4,000 kc. wide nor the one 2,000 kc. wide is the “widest.” Even the best ad- justed station occupies a little slice out of the spectrum and this “slice” is to be ex- pressed as a percentage of its operating fre- quency, so that as we get into a higher- frequency band we find that the width of the channel required for a single station is greater, and that a wider band will not necessarily accommodate more stations. Let us make some attempt to determine this “channel width.” The Navy Department has calculated it out for the Federal Radio Commission on the basis of the 1929 assign- ments. It commences by assuming that interference. Understand that we amateurs aren’t going to observe individual channets within our bands, but a consideration of the subject is useful in establishing the relative widths of our different bands. We find that on the basis just suggested the separation between channels in our “160-meter” band is 5.71 ke., 9.5 ke. in our “80-meter” band, 16.3 ke. in our “40-meter” band, 30.4 ke. in our “20-meter” band, and 60 ke. and 118 ke., respectively, in our two highest-fre- quency bands. It is apparent that we need some new scale if we are to have an accurate gauge of the number of stations which can be accommodated in our various 1929 bands. This is supplied in Figure 5, which takes ac- count of the fact that at double the fre- quency a signal occupies double the room in the spectrum. Now we are able to gauge the relative widths of our bands. We find that the “5-meter” and “10-meter” bands are the same in practical width, that the “20-meter” and “40-meter” bands are narrower than this but that our “80- meter” band is double this in width, and that our low-frequency band is our widest in point of number of stations that may be accom- modated. , In Figure 5 the “40-meter, 20-meter and ° 5-meter” bands are shown extended by dotted lines to the extreme right-hand edge of the drawing. These are the former widths of

Page 20

the nds, the territory which we are authorized to occupy during 1928, and thus lrawing shows graphically the extent of on which our Commission is r commercial assignments. The Ost SEPTEMBER, 1928 international agreement is that it is avail- able for mobile, point-to-point and amateur services, but the present disposition of our our s at the Washington conference. Commission is to make no assignment in Th a harmonic relation in this draw- it other than amateur, considering the ex- ing Any point on one line is the second tent to which our high-frequency alloca- har of the point on the line immediately tions have been clipped. We use the band abo the fourth harmonic of the corres- chiefly for telephony, to which it is open por point on the second line above it, throughout its extent. It is an excellent etc our 1928 assignments were atrue’' short-distance telegraphy band and our har family, each higher-frequency Communications Department is planning ban ng of twice the width in kilocycles the expansion of this work as a beginner’s of t sand which preceded it but each wave. It will probably also be available capable of accommodating the same number’ soon for television and picture transmis- of stz 1s, and with the additional feature, sion experiments. It is to be noted that ba n the motto of the Third National the portion 1715-1750 ke. has no harmonic Ra onference that “Everybody should relation to any of our other bands. The eat wn hash,” that the harmonics of frequency in this band which is the center BAND KILOCYCLES “160 -MET ‘80-METER” ‘4O-METER"| (sat rr ten. ————— ~~ Bi aernimietennier cmbateteietate aheamadeteabeieig: 1O-METER I ‘SMETER 999%%j-----7- tc Seooe | 60000 — 64000 -—Center of harmonic family SHOWING RELATIVE WIDTHS OF 1929 AMATEUR BANDS FIG. 5 an r transmission could fall only of the harmonically-related portion is 1775 with higher-frequency amateur band. kc, Onl ll portions of our 1929 bands are 3500-ke. band, This is our well-known har ly related to all of the others. “80-meter” band, 3500 to 4,000 kc. (85.7 to Th of the harmonic portion is shown 175 meters). This band remains the same in fig in Figure 4 and is illustrated by in 1929 as it is today. That is fortunate the line in Figure 5. From this it for us, for this is our traffic wave, the ma} en that if one wishes to have a_ heart of our Communications Department, cry hich, by harmonics, is capable of the backbone of the League. Most of our wol every amateur band, the crystal organized operating activities take place on sho a frequency between 1750 ke. it, and by far the bulk of our domestic and ke. (166.7-171.4 meters); or, if communications. The Navy rates it as the eter” band is not desired, be- containing 52 commercial channels. The twee! ke. and 3600 ke. (83.3-85.7 me- harmonic center is at 3550 ke. Telephony ter is permitted between 3500 and 3550 ke. (85.7 v geht now with profit look a little and 84.5 meters). The international m ully at each of our bands. agreement on this band is also that it is hand. This band actually runs’ available for amateur, mobile, and fixed fro to 2,000 ke. (175 to 150 meters). services. But the Federal Radio Commis- It about 60 commercial channels _ sion, impressed with the necessity for our retaining it if our organized communica- tion is not to perish, has decided that no

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128 ail- eur our ex- ca- and pen ent our ing r’s ble is- nat nic ‘he ter ou Sconewe TWO O O&O a, i, re aa | SEPTEMBER, 1928 commercial mobile or fixed assignments will be made therein in this country. We re- tain in this band our old arrangement of the last several years with the govern- ment services, whereby we share this band with low-power Army, mobile stations working in daylight hours during the field training season, and with Naval aircraft while operating off-shore. The President has assigned to the Navy sixteen frequen- cies within this band for the use of Naval aircraft. The Navy has used frequencies here for many years and has not bothered us, so there is no reason to suspect that this means any additional inconvenience for us. 7000-ke. band. This is our million-dol- lar band, the center of the rumpus at Wash- ington last fall, the one where we acquired the heartache and lost our shirt to Europe and Canada. Originally 7,000 to 8,000 kc., it will read next year 7,000 to 7,300 kc. (42.86 to 41.1 meters), with its harmonic center at 7,100 kc. It contains 18 commer- cial channels, viewed with envy and cupid- ity by a crass and vulgar commercial world. It is our chief international night band, and is open only to amateur teleg- raphy. Considering that we have nearly adequate privileges for domestic communi- cation in the 3500-kc. band and are handi- capped chiefly in our international] bands, the League has proposed to the amateur societies of the world that the 7000-7300- ke. band be used in intra-continent work only for distances in excess of 1500 miles and that an informal and unofficial sub-div- ision of the band be made for international working, whereunder amateurs of the United States would confine their transmis- sions to the portion from 7,000 to 7,150 kc., the remainder being partitioned amongst other groups of nations. This proposal is still pending. 14,000-ke. band. This band, once our joy and pride, extending from 14,000 to 16,000 ke. but never extensively occupied and held by amateurs, now reads 14,000 to 14,400 kc. (21.48 to 20.83 meters). Containing 13 commercial channels, it is our narrowest band in effective width, and as such dic- tates the center of the harmonically re- lated portions of all of the bands, its center of course being at 14,200 ke. This is our daylight DX band, also used for super-DX at night. It is open only to telegraphy. In the same fashion as suggested for the 7,000 ke. band, the League has proposed the informal sub-division of this band amongst the amateur societies of the world, under which plan North American ama- teurs would confine their emissions to the portion 14,000-14,200 ke. This too is still pending. 28,000-ke. band. This is a new band ex- tending from 28,000 to 30,000 ke. (10.71 to Ost 23 10 meters) Although 2,000 kilocycles wide this band contains but 33 commercial chan- nels and is therefore only of half the ef- fective size of our “80-meter” band and just slightly larger than our “40-meter” and “20-meter” bands combined. The “har- monic center” is at 28,400 ke. The high- est frequency regarded as being of com- mercial value is about 23,000 kc, and the value of this band is therefore questionable. Early experimenting has been fruitful, however, even over moderate distances, so that there is excellent reason for hoping that we shall be able to make this band of practical value to us before long. The international assignment is to “amateur and experimental,” so that we may expect experiment stations of all descriptions to roam this band with us. 56,000-ke. band. This is what is left of the old “5-meter” band, now extending from 56,000 to 60,000 ke. (5.36 to 5 meters) and with its harmonic center at 56,800 kc. This also is “amateur and experimental” and perhaps a better term for it would be ama- teur experimental, as it has not yet been developed for practical communication. Much work has been done on it, by Kruse, Phelps, Douglass, Jones and others, and oc- casionally good signals have been heard at decent distances but with no reliability. This band and the 28,000 ke band are heav- en for the experimenter, to whom we must look for methods which will eventually make them useful. 34 channels. The en- tire band is open for telephony work as well as telegraphy, and probably will be made available for amateur television and picture-transmission work. As we conclude this informal analysis of our 1929 bands it seems all the more dem- onstrated to us that any proper apprecia- tion of what we have and what we are doing next year must be in terms of fre- quency, —K.B.W. Errata The following corrections should be made in the Bourne article on Acoustic Wave Filters in August QST: p. 25, second paragraph, first sentence, should read “. ‘ and attenuates cur- rents of all other frequencies.” p. 26, next to last paragraph, last sen- tence, should read “. ... we have attenua- tion from 0 up to f; and from fs on up, ” p. 27, third paragraph, for “diameter” read “distance.”

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SEPTEMBER, 1928 Opportunity By Hiram Percy Maxim, President, American Radio Relay League Vhen I was a very small boy my father and I used to ponder at length over oblem: Is it the salt fish that makes the ocean salt, or is it the ocean t makes the salt fish salt? T} I eur Radio has made us? \mateur Radio is one of the amazing products of this century. Where be- has an amateur group been dep before has an amateur group every kind of an exploring expedition that starts out? Where before has amateur group been depended upon by a great railroad system for its com- nications in time of emergency? Where before has an amateur group been nded upon to carry a message from the President of the United States to lorer in the polar regions? And where before has an amateur group led in an important field of scientific research? answer is: Nowhere. And hence the question: Is there something Amateur Radio that carries us amateurs along with it and makes us t we are, or is it we amateurs who have made Amateur Radio the wonder- ng it has become? lieve it is we amateurs. We built up a splendid organization, which gave tremendous advantage of being nstead of a disorderly mob. we never otherwise would have nd all the OPPORTUNITIES have not passed. Radio telegraphy brought leasting. The latter brought the e amateur moving pictures came along. They have brought that latest el, full natural colored amateur motion pictures. Commercial full natural 1 motion pictures will quickly come from these, and full natural colored . And then will come radio television in ng moving pictures will follow it natural colors. teurs are to have golden OPPO wonder which of us, obscure to-day, are to shine with the lustre of a ibergh tomorrow. keep everlastingly at it, fellows. ere is a somewhat similar problem to-day but there is no joker in it. Is ateur Radio what we amateurs have made it, or are we amateurs what ended upon in great public emergencies? been depended upon for communications able to work as an efficiently coordinated And this brought us OPPORTUNITIES, had. talking moving picture. And then mean- RTUNITIES in all of them. And it leads wh cific Division Convention 1d, California, October 11-12-13 lows, the 9th annual convention Pacific Division is to be held Key Route Inn, 22nd & Broad- d, on the above dates and some has been prepared. No dry talks, but of course there will be The big motto is a good time one with trips to Idora Park, rides on all concessions will be ming, roller skating, etc., on one the next day at Lakeside Park pienie lunch will be served and umber of stunts will take place. A special trip will be made to San Fran- cisco where the gang there will entertain the delegates. The committee in charge is working hard to outclass all previous conventions but we will need your attendance to do this. Come one, come all—every one will be welcome. Write S. G. Culver, the convention secre- tary, Box 549, Oakland, Calif., that you will be present. . Strays "$) Perhaps the simplest way to get a good musical note would be to paint the set with phonograph records dissolved in alcohol. —6BWS —

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SEPTEMBER, 1928 OST 25 Adapting Medium and High-Powered Self- Excited Transmitters for 1929 Service Some Design, Constructional and Tuning Considerations Involved By Ross A. Hull* As a sequel to “Overhauling the Transmitter for 1929,” which appeared in the August QST, this article treats the particular modifications which are desirable in transmitters of medium or high power. It is assumed that the reader will have made a detailed study of the preceding article. If this is not so, a complete understanding of the present outline will be impossible.—Editor. O one will deny the existence of a belief, among radio amateurs, that a transmitter assembled neatly be- hind a shining panel and equipped with a fine array of meters and control knobs never works quite so well as did the same apparatus in its early life, spread in wild confusion across a table top. Nor can sadly as the power was raised. For a week or more, the Laboratory was filled with odors of burning bakelite, hard rubber and wood, and at times whiffs of smoke drifted lazily across the tables—but in the end our pulse had returned to normal, for we had found that even 250-watt self-excited trans- mitters can be made to behave in a 1929 ONE TYPICAL HIGH-POWERED SELF-EXCITED TRANSMITTER WITH A “1929 TYPE” PERFORMANCE Heavily built with conductors, resistors, condensers, transformers and chokes of ample pro- portions, provided with High-C grid and plate tanks, and tuned with extreme care, this trans- mitter behaved admirably both in the Laboratory and when later operated under average conditions. In two evenings, when five countries were “worked”, the reports—whether we be- lieved them or not—were all “d.c. crystal-control”’. it be denied that there exists an equally fallacious belief to the effect that the circuits and values of a successful low-powered transmitter will not provide an equivalent performance when high power is used. We had built low-powered transmitters which provided a “1929 performance” but there was too much of the radio amateur in our make-up to allow us to approach the appli- cation of the same ideas to high-powered work without considerable concern. There was, it seems, that inborn fear that the per- formance of our transmitters would drop *Associate Technical Editor, QST. In charge A.R.R.L. Technical Development Program. manner with just the same treatment we had given the low-powered set. The treatment, as we explained last month, consisted of installing High-C tun- ing circuits, making all conductors, conden- sers, resistors, transformers and chokes of ample proportions, and tuning with ex- treme care to keep the grid excitation at the most desirable value, the antenna coup- ling at the lowest practical point and the antenna detuned on the particular side of resonance which provided the cleanest signal. The only serious problem, of course, was that involved in the use of the High-C circuits which we had found so effective

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w-powered transmitters. Calcula- wed us that we could expect tank of the order of 18 amperes if we the capacity-inductance ratios of powered sets, and much experi- rk preceded the construction of La Cs %,

UV-204a 1. ¥ L

0000

OST

SEPTEMBER, 1928 cannot be followed in any self-excited trans- mitter if a 1929-type performance is to be expected. The circuit used is the tuned-grid tuned- plate, selected on account of its mechanical suitability for use with a long tube having its grid terminal at one end and its plate at the other. Other cir- cuits could have been used but L; with this particular tube they C3 would not have permitted the same simplicity of layout or di- rectness of wiring. = —

sCr Lis VW Cs RL R, | SS dk . 7 a pe ; Or ik, , J | Suvac -HY

+ 20009 OC 1. THE CIRCUIT OF THE TRANSMITTER ILLUSTRATED 140-upfd. jensers, (40-unfd. variable condensers uning condensers used to provide adjustable apacity for the High-C circuits. : or 250-upnfd. tuning condensers. uifd. fixed by-pass condenser -unfd. fixed grid condenser 00-upfd. by-pass olt rating). fixed filament 0-ohm center tap resistors. A center-tapped filament Leaks rated at 75 watts or less usually will heat appreciably and cause ransformer can be used instead. Heavy duty 10,000-ohm grid leak. requency creeping. 160 turns of 26 gauge D.C.C. wire on a %” diameter orm ireult was used can be used. in which the losses were low be justified without question by vement in performance. \ TYPICAL TRANSMITTER transmitter, built at the comple- experimental work to provide a ample of the manner in which the rh-powered transmitter should be re- m r 1929, is that illustrated in these pag We will first describe it in detail an n proceed to a discussion of the man- ner which the same principles could be ap] transmitters of other types. \ UV-204-A tube was selected for use in th mple” transmitter since it is the lars readily available to the amateur and the tube most suited for use in a l rpe high-powered outfit. A great 1 teurs attempt to build a success- f wered transmitter by using a UXx-S§ r similar tube running at four or five its rated power but there is not the rhtest question that this procedure variable antenna or feeder tuning con- connected across the (5,000-volt rating). (5,000-volt rating). condensers his in the transmitter under discussion reference te the Hartley or Colpitts merely because of articular adaptability to a tube having its grid terminal me end and its plate at the other. Any one of the many factory keying methods which have been described in

TANK CONDENSERS The variable _ condensers throughout are of standard types. Many types of pie-plate, copper disk and copper tube condensers for the tank circuits were built, and still more designed, but con- siderations of compactness and simplicity invariably brought us back to the use of the standard types connected in parallel to give the necessary capacity. We admit, however, that there is a splendid field of endeavor in the evolution of cheap and effective “home-brew” fixed or adjustable tank condensers to be added in parallel with existing tuning con- densers. The most important requirements will be the use of heavy copper sheet for the plates, and pyrex glass, high quality hard rubber or well dried wood for the insulation; the use of heavily-soldered connections to all plates, and the provision of some means of halving and quar- tering the capacity so that it may still be used on the highest frequency bands. In both the grid and plate circuits of this transmitter, a Cardwell Type 199 con- denser is run in parallel with a Type 147B, the former used for tuning adjustment, hav- ing a maximum capacity of 330 pyfds., and the latter used as an adjustable lumped ca- pacity, contributing 440 pufds. The two feed- er or antenna condensers are of the Type 147B. “Double-spaced” condensers are all that are necessary for the plate tank of a tube supplied with 2000 volts when a High- C circuit is used. Where plate voltages of the order of 500-1000 are used the spacing used in good receiver-type condensers is satisfac- tory. In the grid circuit the voltages are still lower but it was still found worth-while to use “double-spacing” where the plate voltage is of the order of 2000 volts. INDUCTANCES OF UNUSUAL PROPORTIONS The grid and antenna inductances are wound with %” copper tubing, this be- ing of suitable size for the currents “lumped” (2,500

rry a. @ ats & G&G 2 oe

Page 25

‘ans- 0 be ned- 1ical ving and cir- but they the di- SEPTEMBER, 1928 flowing in the circuits in which they are connected. The plate coils, how- ever, are of much heavier construction. Our first plate tank had an inductance of the same 4” copper tubing as that for the grid and antenna coils, the temporary connections to the condensers being made with clips heavily soldered to cables of about the same diameter as the tubing. OST 27 long periods at higher power than the rating of the tube, for both of them, under such conditions, heat appreciably. Experiment with High-C circuits covering the widest practical range of values and dimensions has led us to recommend that plate and grid tanks similar to those of the transmitter under discussion be used in cases where the input power is between 100 and 400 watts. THE “250-WATT” TRANSMITTER AS SEEN FROM ABOVE At the right is the grid unit comprising the tank circuit with its two variable condensers in parallel, and the heavy duty grid leak immediately behind them, Of the four fixed condensers arranged in a group, that on the right is the grid con- denser. On the left of the group is the plate circuit by-pass condenser, the remaining two serving as the filament by-pass. On the left side of the transmitter is the High-C plate tank, with its unusually heavy inductance, and the antenna tuning unit. To the right of this plate unit the radio frequency choke can be seen. After a run of a few minutes the conductors heated to the point where solder is liquid and the whole thing fell apart. The plate coils eventually decided upon as the mean of efficiency and clumsiness are of %” tub- ing, the ends, as in the case of the other coils being sweated into copper lugs of the type used in power switchboard wiring. The plate and grid coils are attached with machine screws and wing nuts to %” wide, copper strips which serve also as the con- nectors between the two variable conden- sers. The exact arrangement of this mount- ing can be seen in the photographs. The antenna coils are mounted in a somewhat similar fashion on brackets projecting from the two series condensers. The important points to observe are that the plate and grid coils are mounted directly on the con- densers, so avoiding any long leads; that the connections between the coils and con- densers are of heavy construction with large contact areas, and that the mountings are sufficiently substantial to avoid the possi- bility of vibration of the coils unless they are actually struck. It might be admitted that even the plate and grid coils of the present transmitter could be improved upon if the transmitter were to be operated for For inputs greater than these it is sug- gested that %” outside diameter tubing or, preferably, %” wide, heavy copper strip, be used for the plate coil and %” tubing or 1%” strip for the grid. In all cases the leads to the tank condensers should be of similar conductor to that used in the inductance and some heavy clamping device should be used for the connections. Clips simply will not serve the purpose. Further comment on the constructional details of the transmitter are hardly neces- sary for the minor points can well be gleaned from a study of the circuit diagrar and the photographs. It can be said, how- ever, that it is not suggested for one moment that the transmitter represents the acme of mechanical and electrical perfection. It is presented merely as an example of the simple modifications necessary to equip the amateur transmitter with High-C tanks, mechanically rigid construction and, as the outcome, the ability to produce signals of 1929 standard when tuned correctly. REBUILDING EXISTING TRANSMITTERS In quite the majority of present-day ama- teur transmitters, complete re-construction would not be necessary in order to modify them in accordance with the ideas set out

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OST SEPTEMBER, 1928 | SE In a Hartley transmitter employ- Aside from these matters, the attainment me X-582, for instance, the only import- of a 1929 signal with the self-excited circuit kil ges might well be in the mounting’ will most certainly mean the dumping of Ing be so that its grid and plate leads_ az.c. or “self-rectified” plate supply and the rig ent to the plate tank, the addi- installation of some form of rectifier or a , generator. At the moment, sad to | relate, the only truly practical rectifier for the UX-852 or UV- 204-A is the mercury arc, but we are fortunate in being able to hint that it may not be long be- fore this condition is effectively remedied. The filter system is still to be a problem but the im- provement in the plate-voltage- . vs.-frequency characteristic af- Bm forded by the use of High-C > tanks will simplify the matter to = a considerable degree. We dis- = like the idea of talking results S and so leaving ourselves open to S misunderstanding on the part of > the more literal-minded readers, a. but in this connection we cannot z refrain from mentioning that the transmitter illustrated on these pages, supplied from a mercury are rectifier and equipped with a 2 ufd. condenser as its only filter, can produce a piercing “d.c.” note ‘ E-UP" OF THE PLATE TANK AND ANTENNA on which modulation can be de- FI TUNING UNIT tected only by the hypercritical cl mmediate foreground is the 440-yufd. variable con- observer. den viding “lumped” capacity, adjustable for the various freat bands. Behind it, and connected in parallel with it, ADJUSTING FOR A 1929 PER- th: is th vain tuning condenser. Heavy copper strip is used for " all r ions in the tank, the inductances being attached to FORMANCE th the | ank ae 4” aaene en =" wing i. ~ The tuning process for the be et feng te lah oy Sa eel cleans high-powered transmitter is similar to that described last ac second variable condenser in month for the low-powered set, the chief ec pa with the existing plate condenser, ec an provision of a new set of plate coils al v table heavy mounting and connec- be he condensers. cI I Colpitts transmitter the same process a W pply, the particularly important th point in this case being to remember that q h ge condensers” and the condenser ws joir he two coils in the “split Colpitts” D al e considered as tank condensers te al ist not only be proportioned to give a th red total capacity across the coil rn bu | be of a high grade, air dielectric m= ty 111 mica dielectric condensers could 0 | effectively in these roles. THE TYPE OF PLATE INDUCTANCE SUGGESTED | we na sas, FOR USE WITH INPUT POWERS GREATER THAN C) n all probability, the altera- 400 WATTS b ™ uld involve a general clean-up Built of %” thick copper strip %4” wide, inductances r stiffening of the antenna coil of this type proved satisfactory in the High-C plate ti - unting, and some re-rigging of tank even at the highest possible input to the tube. in +} ° 1 to avoid appreciable vibration y mene ——— a b 3%” copper — in- a > Then, it may mean installa- ee —— revealed no improvement nm per- c q ormance at would justify their use with input 1] parate filament transformer to eee Sons oy — under —— —o 5 a 1ent-volt > i i of efficiency. Rather, e scarcity and expense o e . , : } ae Seer ata eae strip, and the difficulties entailed in ane it, made u : i : - the tubing much to he preferred. 1 f filament supply if a filament r t is being used and fluctuations difference being in the observance of ex- Q treme care in avoiding contact with any

Page 27

ment reuit g of 1 the or a ad to tical UV- t we e to r be- ively m is im- age- af- rh-C r to dis- sults n to t of lers, inot the hese ury ha iter, 10te de- ical the is last lief ED AN ces ate in- er- put ns ide X- SEPTEMBER, 1928 metal part of the set. The operator can be killed suddenly and very effectively by com- ing into contact with the transmitter in the right (or wrong, if you wish) manner. In the tuned-grid tuned-plate circuit it is well first to set the plate condensers at ANTENNA CURRENT (AMPS ) FREQUENCY (*« ce) ANTENNA TUNING (Scale Divisions) FIG. 2. ANTENNA-TUNING VS. CURVES FOR THREE VALUES OF COUPLING In addition to showing a performance similar to that of the low-powered transmitter described last month, these curves provide further indication of the splendid improvement in stability afforded by loose antenna coupling. FREQUENCY ANTENNA some estimated value with the grid tank condensers at zero. Then, with the antenna coil removed, the plate voltage (reduced to about 75% of the rating of the tube) can be applied, and the grid tank capacity in- creased slowly until the plate current dips and then rises to a value about 10% higher than the minimum. At this point the fre- quency should be checked, and if it is not within the band the process should be re- peated until it is. At this stage the an- tenna coil can be coupled loosely and the antenna or feeder circuit tuned until maxi- mum current is indicated. If the plate cur- rent at this point is still below the rating of the tube, when the voltage has been in- creased to normal; the grid capacity can be increased until it has climbed to the required value, at which time the antenna tuning should be readjusted. Each change in the constants of the grid circuit will mean changes in frequency and so continual check- ing with the frequency meter will be neces- sary. The antenna coupling can now be increased until maximum antenna current is obtained and immediately it should be reduced until the antenna current is about 85%, of the maximum value. It is at this OST 29 stage that it is so essential to check the signal with a monitor or “Growler” in order to observe on which side of resonance the antenna should be detuned in order to obtain the cleanest signal and in order to permit that final polishing of all adjustments which is to mean the difference between a good 1928 and a 1929 performance. The monitor will be indispensable also in deciding upon the connections to the antenna coil. With symmetrical current-feed antenna systems the difference in note with the leads to the antenna coil connected one way or the other usually will not be marked but in the as- re ‘S MS GRID AND PLATE INDUCTANCES FOR FOUR FREQUENCY BANDS For the 3500 ke. band Ap and Ag are the coils used, Ap being 3%” inside diameter and Ag 25%”. Bp and Beg serve for the 7000 ke, band, Cp and Ce for 14000 ke., and Dp, Dg for 28000 kc. With the excep- tion of coil Ap the coils are all 2%” inside diameter. The plate coils are of %” outside diameter copper tubing, and the grid coils of %4” tubing. All of them were wound by hand on ploses of iron pipe. This procedure is possible, however, only when the tubing is of the “soft drawn” grade. eS aa z= symmetrical antenna feed systems such as the “Zeppelin,” the vertical current-feed an- tenna or the “antenna-counterpoise” ar- rangement, many adjustments can be ob- tained with which one particular connection must be observed. In the transmitter under discussion with the particular antenna used the shrill “d.c.” note gives place to a heavily modulated signal just as soon as the feeder connections are reversed. The more we tune transmitters the more convinced do we become that the amateur transmitter can be tuned about as success-

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OST by watching the meters alone as an bile can be driven in heavy traffic by ve observance of the ammeter and ° in N ANTENNA CURRENT (AMPS) w 30 40 50 60 10 ANTENNA TUNING (Scale Divisions) FI ’. PROVIDING SOME INDICATION OF THE INSTA- BILITY ACCOMPANYING LOW VALUES OF GRID EXCITATION Carves A, Al were taken with the grid condenser set at the voles wh ich gave minimum plate current. Serious frequency instability was noted and the curves could not be duplicated by rotating the antenna condenser in the opposite direction. Satis- factory stability could only be obtained by the use of extremely coupling. Curves B, Bl were taken with that value of grid excitation which gave the rated plate current for the tube under normal conditions. Much greater frequency stability is indicated and the frequency curve B could be checked and re- loose checked at any point. With still greater grid excitation curves C, Cl obtained. The rather flat frequency curve C, however, was accompanied with a considerable loss of output and serious heating of the tube. The adjustment was not one which could be used in practice. With this circuit the adjustment of grid ‘mning’ and antenna coupling are closely related. Lew or high values of grid excitation require extremely loose antenna coupling te give satisfactory frequency stability whereas, with grid e citation of a particular order, the normal antenna coup- line can be used and high efficiencies obtained. A study of the signal in the monitor can be depended apon to reveal this de- sirable value of grid excitation. t] gauge. We can see no more justifi- cat n the amateur operating his trans- mitter without being able to hear what his sig? doing than in the motorist driving hi r without the ability to see where he g In fact we can forsee the possi- bil * the introduction of another crime eur radio punishable by Wouff Hong of operating a transmitter without ring it throughout every transmis- Why, broadcasting stations are put off r for failing to do that very thing! ; Mp Strays"$5 2 Save Postage! July 1 private mailing cards, if form to standard government post- in at Why,

and wireless telephony. it is stated, Nelna has been talking to Paris, Petrograd, "Berlin and London every day for several years. What these messages are may lead to startling discoveries.” may yet be the cause of another World War. SEPTEMBER, 1928 card size, 54%” wide x 3%” high, may go thru the mails, in the United States and its possessions only, with only a 1-cent stamp affixed. When making up your QSL cards have them of the above dimensions (unless you use the government l-cent card) and you will save 1c on each card. Private mailing cards of other sizes still take 2c each. Add this latest in- formation to the rates already given on page 26 of the July, 1928, issue of QST and save yourself money. 8AA, on his new card, has re- placed all the conventional dotted lines with the statement “Believe it or not! Your ‘Pure d.c. Crystal- control signals’ pounded in here Oe iccéndheasneakone 19.. That’s one more stunt that won't be novel any more. _—e<“00—4 Undesirous of climbing the high roof of a rickety barn to unhitch his old antenna, and anxious to make room for his new one, 1BZJ hit upon the idea of shooting it down with a “22” rifle. A single shot, it is said, sufficed. YL—“And what's the furthest place you’ve ever reached with your radio?” Ham—(Wondering whether she meant transmitting or receiving.) “Elucidate”. YL—(She must have been a bit dumb.) “Never heard of it.” 1BHB, 1ARA

6BWS has built a new 5 meter transmitter. The component parts comprise a filament meter, plate meter, grid meter, antenna meter and wavemeter. [We used that this month because we are to talk fre- quencies from now on.—Editor.; ee | Special Despatch to the Toronto Globe. (Extra special we'll say) Quebec,— “Hidden in a shabby street here has been found what is described as the most power- ful radio set in America, the machine being in the possession of a 21 year-old Russian. With this set Arsene Nelna is said to have been in communication with European Capitols for the last two years. —————- radio is The powerful called a “Kolster Decremeter”, and it is the last word in telegraphy With this machine, yes. The “Kolster Decremeter”

sam © ow ascro eto an anmt aoe Oe at &

Page 29

1928 lay go and its stamp ) your above e the d you Tivate s stil] st in- ready 1928, urself high hitch is to BZJ 2 it ingle hest with she ng.) bit iter rts ate ter hat re- be. en rere ing an. for ful r”, hy ne, for SEPTEMBER, 1928 OST 31 The UX-860 A Screen-Grid Power Tube By Harold P. Westman, Technical Editor HE long line of radio tubes already available to the amateur and experi- menter has recently had a new youngster of rather husky propor- tions ushered into its m'dst under the alpha- betical-numerical cognomen of the UX-860. It being a “power” tube, there is no “CX” or Cunningham designation involved. The UX-860 is a screen version of the 852. In cases where the 3.3 uufd. grid-to- plate capacity of the 852 causes trouble, the 860 may be substituted and its reduction of this capacity to a value of .05 wufd. should be very helpful. It is designed primarily for use as a radio frequency amplifier at fre- quencies greater than 3,000 kcs. The screen- grid does away with the necessity of neutral- ization although it by no means does away with the need for proper shielding of the external circuits. While it may be used as an oscillator, it has no particular advantage over the 852 as such nor is it generally suitable for use as a modulator or audio frequency amplifier due to its high plate resistance. This tube very much resembles the 852 in appearance. It is of the T type in which the plate and grid are supported on separate stems with their leads brought out through separate seals which insure low capacity and high insulation. The filament is supported on a third stem and its leads together with the lead from the screen grid are brought out through another seal. As in the 852, the filament leads terminate in a UX base, the screen-grid being connected to the grid terminal of this base. A thoriated tungsten filament in the shape of a double helix is supported from a center rod and requires no springs. The plate is cylindrical with six fins or wings to dissipate heat. The screen is of close mesh and is interposed between the control grid and plate. It is as high as the tube and is sup- ported by collars clamped to the filament and grid stems. The filament should be operated at its rated voltage. Loss of emission may be occasioned by either overloading or under- loading the filament. Loss of emission due to reduced filament voltage is due to too low a rate of diffusion of the active material to the surface of the filament. This is ma- terially hastened by the application of abnormal plate voltage and high plate current. As with the other tubes employing thori- ated tungsten filaments, severe overload may cause a decrease in emission. Providing a large amount of gas has not been liberated, the emission may be restored by discon- necting the plate and screen-grid voltages and operating the filament at normal volt- age for ten minutes or more. The time re- quired for reactivation may be decreased by raising the filament voltage to 12 volts. The maximum plate dissipation either as an amplifier or oscillator should never ex- ceed 100 watts. This corresponds to a cherry red color of the plate. Looking at PLATE VOLTAGE FIG. 1, SHOWING THE VARIATION OF BOTH SCREEN-GRID AND PLATE CURRENT WITH CHANGES IN PLATE VOLTAGE, CONTROL GRID VOLTAGE BEING ZERO AND FILAMENT VOLTAGE, 10. the plate with the filament lighted is apt to be misleading because of the reflection of the light from the filament. It is best to turn the power supply to the tube off and note the plate color. The screen voltage may be obtained from a separate source or from the plate supply system. The use of a separate source is not only expensive but does not offer as much safety as does the second method. If the plate voltage is removed and the screen volt- age maintained, the screen current will in- crease considerably and overload that ele- ment, destroying it perhaps. On the other hand, if the screen voltage is obtained from the plate supply system, any changes in plate voltage will also result in a change in screen voltage and the ratio of the two will remain about the same, thus eliminating this danger. If a resistance of approximately 100,000 ohms be placed between the positive terminal of the plate supply and the screen, the voltage on the screen will be of a satis- factory value. When using this method of

Page 30

filament circuit should not be with the plate voltage on or the voltage will be applied to the llessly stressing the seal, etcetera. ses, the impedance between the filament must be kept low by f by-pass condensers. At no time creen dissipation exceed 10 watts the case of the plate is indi- cherry red coloring. yrmal operation, a bias of approx- 200 volts should be applied to the grid. When a leak is substituted bias, its value should be about | | ° +20 +40 CONTROL GRID vocrace EFFECT OF CONTROL GRID VOLTAGE SCREEN-GRID AND PLATE CURRENT WITH 2000 VOLTS ON THE PLATE. The value of bias is not und variations to suit particular irrangements may be made. Both 1 plate leads are in the form of two which should be twisted to- If only one of these conductors is essive heating at the seal may re- haracteristics of the tube are given voltage 10. current 3.25 amperes. lowing values are obtained with ate voltage (2000 volts) zero grid i normal screen voltage (500 volts); irrent 70 milliamperes. istance 150,000 ohms. onductance 1.35 milliamperes/volt. ation factor 200. ate direct interelectrode capacities definitions). grid (Filament and -_ grounded) 05 uufds. filament and screen 85 “ filament and screen 9.0 - perating plate voltages 1 plate voltage d.c. 2,000. volts. lulated plate voltage d.c. 3,000 volts. voltage (r.m.s.) 3,000. volts. OST SEPTEMBER, 1928 Maximum plate current d.c. 100. mils. Maximum plate dissipation 100. watts. Maximum screen dissipation 10. watts, Nominal screen voltage 500. volts. The filament voltage current character- istics are the same as for the 852 and are not given here. This curve may be found on page 21 of the May, 1927 issue. This tube should be of interest to those operating crystal controlled transmitters or other types of oscillator-amplifier circuits at the higher frequencies where feedback is so damaging. As w.th all other power transmitting tubes excepting the 852, the 860 may only be obtained directly from the Engineering Products Division, Radio Corporation of America, 233 Broadway, New York City, New York. To save you the trouble of tell- ing us that the 210 and 250 are obtainable through dealers, we should like to point out that these types are now considered as being primarily amplifier tubes for broad- cast receivers and not transmitting tubes exclusively. eH - Correction An error was made in figure 1 in the article “Some More About the Family” by A. B. Chamberlain which appeared on page 29 of the July issue. The ordinates should be labelled “TU Loss” rather than “TU”, thus indicating a loss of high frequency audio energy due to transmission over a bare cir- cuit. This is compensated for by the equal- izer which has opposite characteristics. *e- 9XL Transmissions (Continued from Page 8) Sunday Afternoon Schedules Central Standard Friday Evening Schedules Central Standard Time Time Time Schedule A Schedule B Time Schedule C (PM) f y) f } (PM) f r) 8:30 3.5 (85.7) 7.0 (42.8) 3:00 14.0 (21.4) 8:42 3.75 (80.0) 7.2 (41.6) 3:12 14.2 (21.1) 8:54 4.0 (75.0) 7.4 (40.5) 3:24 14.4 (20.8) 9:06 8.5 (35.3) 7.6 (39.5) $:36 15.0 (20.0) 9:18 9.0 (33.3) 7.8 (38.4) 3:48 16.0 (18.7) 9:30 9.5 (31.6) 8. (37.5) 16- 28 a 26- _ DIVISION OF TIME 3 minutes—QST QST QST nu9XL. 3 minutes—5 second dashes broken every half minute to give station call letters. 1 minute—announcement of frequency in megacycles per second (8.75 megacycles is sent as “8r75 MC.”) If you use these transmissions please send a note to the Experimenters’ Section, A.R.R.L., 1711 Park St., Hartford, Conn.

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1928 mils. watts. watts, volts. acter- id are found those srs or rcuits ack is itting ily be ering n of City, tell- nable point 2d as road- tubes the ” by page ould 4 iar Ludio cir- jual- rnoon s ndard ule Cc / 21.4) 21.1) 20.8) 20.0) 18.7) ery call in 8.75 r75 end ion, L. W. SEPTEMBER, 1928 OST The Zepp Facts and Figures for the Design of the Hertz Antenna with Two- Wire Voltage Feed James J. HE general principle of the two-wire feeder is as old as the theory of electric waves on wires. The Hertz antenna is as old as the theory of electric oscillations. Therefore this article is inded on ancient history, and anyone in- terested in digging deeper into the theory d mathematics of the thing may do so by looking up the chapter on electric waves on wires in Fleming’, (edition of 1910), or n Pierce’s “Electric Oscillations And Elec- ric Waves.” The latter, by the way, cov- rs the theory of feeders beautifully. There are two types of antenna feed in general use among amateurs today, one be ing what is called “voltage” and the other " The names have not as much to do with the feeders themselves, as with the point at which they are connected to the antenna. The voltage feed system is coupled in some manner to the antenna at a voltage antinode (usually at one end) while the current feed type is coupled in some manner to the antenna at a current antinode, usually the center or an odd quarter wave ym one end. The feeder systems are them- selves of two general types, the first com- plex in design and suitable for one fixed the second wonderfully adapta- . irrent ad quency, le to amateur use. The first system is that in which the out- put impedance matches the impedance of the feeder system thereby preventing wave reflection and standing waves on the feeder wires.” The second, is that in which output terminals are open circuited, re being full reflection and consequently standing waves on the wires." The second, used as a voltage feeder, is the familiar Zeppelin, and the one in which we are interested. } } } when The conventional case of two parallel with their output ends open cir- cuited and with a non-reflective source of high-frequency sinusoidal E.M.F. at the in- put end is shown in Figure 1. In the case of the two parallel wires as used in amateur feed systems (the attenuation being negligi- le) we shall have maximum amplitude of rent at G at ae given frequency, 3 (wavelength) when the length Z of each of ? wires wires is equivalent to an odd multip a quarter wave f noth. The current a! ends of the wires will, of course, be SZ-1CEI Technical Information Service Lamb* zero, and the voltage agnplitude a maxi- mum. There will be a phase difference of 90 degrees between the voltage and current at any point on either wire, due to full re- flection, and the current at a given point on either wire will be 180 degrees out of phase with current at a similar point on the \ wi, j } f FIG. 1 TWO PARALLEL WIRES WITH THEIR OUTPUT ENDS OPEN CIRCUITED AND INPUT SUPPLIED WITH A HIGH FREQUENCY SINU- SOIDATI E.M.F. FROM A NON-REFLECTING EACH WIRE IS AN ODD MULTIPLE OF %4 WAVELENGTH LONG SOURCE G other wire an equal distance from the source. The field about either wire will therefore cancel that of the other, and lit- tle or no electro-magnetic radiation will re- sult. If a wire equal in length to an even multi- ple of a quarter wavelength is now added to one side, as shown in Figure 2, the rela- tion of forward to reflected waves remains the same as in the case of Figure 1, but the extension is a linear oscillator in free space, radiates electro-magnetic waves, and be- comes an antenna. This is one way of ex- plaining the theory of the two-wire volt- 1 Principles of Electric Wave Telegraphy and Te y. by J. A. Fleming ? Match T smission Line to the Antenna, I Walter Roberts, Q@ST, Jan. 1928. The volt- é d t practically in phase, there being st i votential difference between the input inals t ffset the drop in the line. A Na yn tube run along the length of such a feeder sys- m sh d Ww th practically constant brilliancy all points indicating almost constant voltage dis- ribution. 3 Wh re is a full refl from the out- t rminals, the voltage and current are in phase 1a tu r 90 degrees out « phase with each ther Standing wave on tl wires accompany re- flection and are ndicated | points of maximum nd m ! ) and « I listance be- tween two points of maximu irrent or voltage is w leneth and the distance between a point of maximum irrent and one of maximum voltage is 1 wavelength. A neon lamp run along the wire ll w with the greatest brilliancy at a voltage r e and will show low at a voltage node.

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» three essential requirements Zeppelin antenna, theory, we can Now that tackle the nsions of a successful “Zepp”, ENGTH OF If it runs close to the a SY 4 2, | 4, —oo— %, % — — 7 feeder system must be such ire is equivalent in length to iple of one quarter of the wave- In other as a unit used. wires the be words, ) must fundamental or an odd multi- ndamental of the antenna must have wavelength a length an even multiple of one quar- ‘eeder system must be electri- rical. antenna feeder system ll now take up its the or radiator is first suspended design and THE ANTENNA f the antenna or radiator for , will not be the same for OST IR ip I E ¢ E ice G Fr OF ™% apparatus. liately over a tin gutter-pipe or LENGTH EQUAL TO AN EVEN WAVELENGTH ADDED ) ONE SIDE OF THE SYSTEM is the antenna inductance and roof, near lightning rod tural period (in terms of fre- na be lower than that of the in the utopian state known The antenna will not far “above ground”, how- » apparently quite free from ‘ect of capacity to ground and ay therefore be calculated as r with zero inductive and ading in free space and later ay be required. which an unloaded operated is its fu it is a “half “ated it is operated. The lowest Hertz an- ndamental. wave”, or Therefore, antenna length we may have of the longest wavelength we The antenna may, of course, SEPTEMBER, 1928 be operated at frequencies which are har- monics of the fundamental frequency, or wavelengths which are %, % or 1/6 of the fundamental wavelength. Let us suppose Cc SERIES TUNING OF THE FEEDER SYSTEM L FIG, 3. that we wish to design an antenna to oper- ate on the four amateur bands of 3,500-, 7,000-, 14,000- and 28,000-ke. (80, 40, 20- and 10 meters). The shortest antenna which may be used is a %-wave 80-meter radiator, although it could be made a %- wave 160-meter radiator and operated as a 2/2-wave antenna on 80 meters. One meter is 3.28 feet, and the length of the %- wave 80-meter antenna is therefore % x 3.28 x 80 or 131.2 feet. We make the an- tenna of this length to start with and lat- er shorten it, if necessary, after giving it a check by the method to be described fur- ther on. Having our radiator now prepared for suspension between heaven and earth, we are ready for the feeders. 9 Vv. DESIGN OF THE FEEDER SYSTEM As stated before, the feeder system as a whole must be tuned to the fundamental or an odd multiple of the fundamental for the wavelength being used. In other words, the feeder system must be %-wave, 3/2- wave, 5/2-wave etc. The feeder system might be so constructed as to have each feeder wire exactly equivalent to an odd multiple of %-wave in length, al- lowance being made for the loading effect of the input inductance, but this would be a tedious process and would permit operation on one fixed frequency only. The amateur demands a_ system which is flexible in adjustment and which permits ready and rapid QSY from one band to another. The solution is, then, to have the system tunable, and moreover tunable in the station itself. This is pro- vided in the two tuning arrangements shown in Figures 3 and 4. The series sys- tem is used when the natural wavelength of the feeder system including the antenna inductance is slightly above the fundamen- tal or odd multiple of the fundamental of

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har- ' the pose ne er 0- ts S- a i- SEPTEMBER, 1928 the working wave. The parallel tuning ar- rangement is used when the natural wave- length of the feeder system including an- tenna inductance is above an even multi- ple of the working wave but less than an odd multiple. In other words, if the length of the feeder is such that the natural wave length of the feeder system is between % and 2/2 or between 3/2 and 4/2 wave etc., the series tuning arrange- ment is used. If this natural wavelength is between 2/2 and 3/2 or between 4/2 and 5/2 ete., the parallel arrangement is used. The series arrangement is used when it is possible to go down to the next odd % and the parallel when it is desirable to go up to the next odd %. Figure 5 shows some convenient feeder lengths and the system of tuning most satisfactory for each of the amateur bands. It is interesting to note that there are some particular lengths which are such that it is impossible to get down to the next odd % wave by series tuning and just as impossible to go up by parallel tuning. Care should be taken in putting up the feeders not to hit upon such a length. This situa- tion results when the feeders are of the or- der of 25 feet in length and it is desired to work on 20 meters. The jump to % wave is too much for series tuning. To go to 3/2 wave puts more than % wave in the antenna tank circuit when the parallel ar- Cc L FIG. 4. PARALLEL TUNING OF THE FEEDER SYSTEM rangement is used, and very little energy transfer from the oscillator output to the feeder input is possible. Increasing the feeder length to 30 feet, however, permits parallel tuning on the 20-meter band while series tuning is used on the 40 meter band. The lengths specified in the table shown in Figure 5 need not be exactly followed, a variation of a few feet one way or the other being permissible, particularly on the long- er feeders, There is one salient requirement in the feeder construction. It must be symmetri- cal. Each wire must be exactly the same length as the other. This is particularly OST important when the system is to be oper- ated on the higher frequencies where a foot is a considerable part of a wavelength, and an apparent slight degree of asymme- . . rennin init TT G 0 APPROXIMATE LENGTH |— oe Ties ecTecoesie soars oF " RE F 1750 kc S50Okc| TOOO kc | 14000 kc | 26000 ke OF EACH WIRE, FEET 1780, KE | 3500Ke! ToDo | ‘ego (om) he ae j - A AN Be 1 120 SER | PAR PAR | PAR |SER.ORPAR + —— a ——__} 30 PAR | SER SER PAR |SER ORPAR = wll 4 ol ee heeenenetee 60 PAR | SER PAR PAR = OR PAR | } } 4 a 40 (---) PAR SER | PAR | PAR _ + ———+ + — — + ———— + 30 (---) (--*) SER PAR = |SER._OR PAR ‘S | } 1 4 } sera 15 ---) | =» | PAR | SER. | PAR en j 1 } ) een Be | 8 r ) (---) +) PAR | ser. | L | __| ct RI, ave SER -Series Tuning PAR -Aeralle/ Tuning (---)- Not Recommended FIG. 5. SOME SUGGESTED FEEDER LENGTHS AND RECOMMENDED TUNING METHOD FOR EACH OF THE AMATEUR BANDS try would result in a comparatively great asymmetrical voltage and current distribu- tion, causing a loss of a_ considerable amount of the non-radiating properties de- sired in the feeders. The distance by which the wires should be separated is not critical in value, al- though there is an optimum value. They must be close enough together to give ef- fective cancellation of their respective fields and far enough apart so that minute vibra- tion with respect to each other will not cause proportionate variation in the inter- wire electro-static capacity of sufficient magnitude to cause, in turn, appreciable variation in the feeder tuning and conse- quent wobbulation of frequency. A value of separation which seems to meet these requirements satisfactorily is 10 to 12 inches. Since, in most cases, the feeder system is suspended from one end of the antenna it- self, all unnecessary weight should be eliminated. This means that the spreaders must be of the lightest obtainable material suitable for the job, and practically puts glass rods, towel bars and the like out of the question. Wooden spreaders in the form of %-inch dowels boiled in paraffin are quite satisfactory, or ready-treated pieces of “printer’s furniture”, which may be obtained in 3%” by %” by 3 foot strips from a printers’ supply or job printing es- tablishment, may be used. Spacers should be placed about every five feet and rigidly connected to the feeder wires. The feeders should be made up of wire of the same gauge as that of the antenna wire, because the current at the antinodes in the feeders will be of the same order of value as at the current antinodes in the Number 12 enameled solid cop- antenna.

Page 34

OST satisfactory both on this so because it possesses suf- lighter wire If possible, the feeders the length of the an- antenna is frequency at which it is being operated by SEPTEMBER, 1928 ficient at the point of maximum antenna current, (resonance) tighten the coupling between the feeder input and transmitter output coils, and repeat the tuning process. The feeder tuning condenser should not be so adjusted as to give maximum antenna current and plate input, but should be set at a point off resonance where the antenna current is about 85% of the maximum obtainable. This will give the stable operation, steady frequency and general al!- around operating characteristics demanded of the antenna system for 1929 conditions." If the series tuning arrange- ment is the one required, the process is the same, both tuninz condensers being adjusted from maximum down simultaneously and kept “in step”. The fre- quency should now be checked with a meter, and a slight read- justment made all around if the tuning of the feeder system has unduly upset the adjustment of the transmitter. The two feeder r.f ammeters should now indicate being approximately equal values of current. If the difference in the two readings is greater than about 10 percent, the length of (Loops), are indicated by V, current our radiator is probably too l-off insulators, wires taut and also te amount of the load ypes and guys. feeder system ‘ul catenary to to the antenna is adjusted to the before we can from the output be tuned to do the table of Figure ng arrangement parallel type. ximum down un- the input is 1 great, and a process of pruning is in order. CHECKING THE LENGTH OF THE ANTENNA A short review of the voltage and cur- rent distribution in the feeders and antenna under the ideal and abnormal conditions may be in order. Figure 6 illustrates A, the voltage distribution when the length of the antenna is correct for the frequency at which we wish to operate; and B, the volt- age distribution when the length of the an- tenna is too great for the frequency at which we wish to operate. There will al- ways be voltage antinodes (loops) at V; and V; of both A and B, as these are the extreme ends of the whole system. This will always be true when there is a state of oscillation. A voltage antinode is also to be desired at a point directly opposite Vs, and this we have at V- in A. In B, how- ever, the antenna is too long for the fre- (Continued on Paae 4. Overhauling the Transmitter For 1929, by Ross A. Hull, QST, Aug. 1928 It h been usually found that a better note, denoting more constant fre- quency, is obtained with the feeder circuit tuned be- w the resonance frequency or with the feeder tun- ing condenser set at a higher value of capacity than at resonance Some exception have been noted however, the note being better in several cases with the tuning condenser set at a lower capacity value. This setting should be checked by listening to the signal via a monitor or shielded receiver.

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SEPTEMBER, 1928 AM not going to sa that ham radio is the bunk, but when you buy a new fifty watt bottle after using a seven and a halfer fer a long time and then onli get one tenth amp less radiation it doesn’t go over like a R 8 report in South Africa. Its all right fer these big boys like 6AM and 6HM to throw the cow’s husband about radiation don’t count fer nothing, but that kinda stuff just qsy’s over my ne o those kind a guys that try the amp meter move until you almost se it going around in a circle. tion is o.k., but me fer the big swing on the ammeter needle, Which all goes to prove that I was getting mighty disgusted when after buying a fifty I found to my pleasure that I was getting abt one amp wid a suction of 200 mills. I had onli been getting an amp and two wid 80 mills. Boy I was sure disgusted and I don’t mean lay VC. When I am sore at my set I usually get out of the shack and L ir d Soa this particular occasion I betook myself in the general direction of 6CL1T “Sa om,” I qsoed, “what do you do fer a amp meter that won’t bedge?” “What kind you got?” he cams k. “It is a answers. “Just set a candle under it,” he sez, watch her budge. I’ll go as far as to bet you get two tenths more.” “Aw. Cut the funny qrm. I just got a fifty and I get a tenth less than I got wid my seven and. I have tried every thing from cutting down the counterpoise to put- ting a couple thousand on the plate. I even put the R.F. chokes in backwards.” Roller Smyth hot wire.” I “We Ta he comes | ick, “Budge l sec ms to get three amps out of his you better try—.” “we : “Sh! I breaks in, looking out of the window, “will you qso that neat pair of ground connections.” We gazed with awe. “Sa, ain’t that one hot mama. i where I am qrw right now.” I jumps up busts out of the door and continues on my way. The mean YL was abt a half a bloc] ahead of me and I aimed to k behind until I found her qrd. About two blocks more and sh« veaks to a v friend, and I’ll be blessed if it isn’t my old friend CBY. A hi does the trick and one minute more and I am qso the bov fr 1 “Who in the world is that mama?” Is ANN, 1148 E. 17th St., Long Beach, C OST gone a o* ww ~l The Fifth Age By W. A. Adams rking my head in the general direction f the fast disappearing YL. I knew that CBY was hogtied so no danger from any qrm. “That’s Helen,” he comes back,” Don’t ou know her? She lives down in your neighborhood.” “T don’t,” I returned, “but I sure craves Hw abt it? Sure thing,” he sez, “I will be over to uur house tomorrow when she goes by. Anything to help another ham.” “Gee your anxious,” I sed, “do you know qrming you a asp. 11 her too well or have I been pretty bad?” “Neithe he sez, but I was suspicious. M: e tha was making more noise han I thought it was. Maybe 6HM was right after all. Nevertheless he was over to the shack next afternoon, and after he d exhausted every means of getting more without putting in a killowatt, we qsy’s to the front porch and the YL ymes by. Everything was working to sked diation YL comes by he puts out a nice ‘Hello, Helen,” he sez. Miss Helen turns ind and we become qso. “Sa,” he con- inues, “I want you to meet my good friend Bill or Annie as he is commonly known.” “Hello, Annie,” she sez with a voice that sounds like crystal control. “I am very glad ‘Your not half as glad as I am,” I says ruthfully. Then an idea pounds in a ton of bricks, fer the om is abt as w asa bug wid all the weights off. Aren’t those books awful heavy?” » comes back, “they aren’t very carry them for you,” I sez, “I was just going down to the store.” I just remembered that my ma had asked me to can of prunes the day before, and + o er them herself. She looks me over but I don’t crack a and she hands them over. “Sure sorry you have to go so soon.” I z to CBY and I begins to walk off wid Helen. But I notices a smile around his ips, and so I looked around when we had ne two or three steps and I see him aughing fit to kill. Right off I confirms icions that something is not so good Ssmiie, (Continued on Page 90)

Page 36

c ANY of those who are receiving our transmissions of radio-movies are having difficulty in rotating their dise in synchronism with the trans- lise so I should like to make a sug- OST SEPTEMBER, 1928 Synchronism By C. Francis Jenkins* is probably already mounted motor shaft and if you have an- If, how- stor it may be left there. uu have only the one motor, it will to mount the disc haft making sure that the bearings supported and not loose. ‘ut from the rubber inner tube of automobile tire, a disc about one- essary on some RIVING the reduce slipage. +h ea rom the center. diameter of your scanning disc. {8-hole, 12-inch disc, a 3-inch rubber VING THE GENERAL ARRANGEMENT OF MOTOR AND SCANNING DISC. driving motor shaft should be at the same shaft on which the disc is mounted so The motor is mounted at an to the scanning disc so that it will usually be than the breadth of the motor. be about right. Put this disc be- pair of 2-inch diameter flanges that mounted on the motor shaft. tor should then be mounted on a ean slide between guide strips latform that holds the scanning disc. ition of the motor should be such case of a 1725 r.p.m. machine to lise at 900 r.p.m., the friction wheel uch the dise at a point about three Now, by means of adjustment, the position of the yard may be shifted so the correct tained. As the friction disc ap- the center of the scanning disc, the e scanning disc will increase. t advisable to use more than two lises cut from the average thick- er tubes and in most cases, one will be best. Although the disc a bit at starting, it will be 1140 simple to obtain and hold n after the dise is up to its run- t Ave., Wash., D. C, Don’t use a rheostat in the driving motor circuit to control its speed; let it run at the speed for which it was designed as this w.ll result in greater constancy. Most any size of motor will do providing it is not too small; a 1/20th, 1/16th or 1/8th horsepower motor revolving at about 1725 r.p.m. will work well with scanning discs up to 12 or 15 inches in diameter. 2@e — Radio Set Tester N this day when the average radio re- | ceiver is operated from a variety of sources, employs tubes that differ wide ly in their characteristics and circuit ar- rangements that are vastly more complex than one would have thought practical a few years ago, the lot of the trouble shooter or repair man is certainly not one that is envied by many. Upon him devolves the problem of keeping the ultimate consumer happy and content with his purchase, for, even the best of sets fall heir to ills most of which are minor but many of which have possibilities of developing into prob- lems of major importance. What is more valuable for the repair man than test equipment which will allow him to put a set through its paces in the shortest amount of time? The diagnosing of trouble should be but incidental to the correcting of it. The instrument shown in the illustration is a versatile device that may be used to check almost all parts of any modern re- ceiver without the use of a great deal of thought or time on the part of the opera- tor. It is equipped to measure direct volt- ages as high as 600 or less than a volt, re- gardless of whether they are obtained from (Continued on Page 70) ing mj act ert the tol th sm in co) op >. eo oars

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* motor at the is this St any not tor >power n. will 12 or ut a punt ould tion 1 to re- l of ora- ‘olt- rom SEPTEMBER, 1928 Ost Remodeling the Traffic Tuner for 1929 Opening up the scale of the Autodyne not only for this year but for next year’s conditions By Harold P. Westman, Technical Editor. set that the receiver to be described is not the result of the organized “Techni- cal Development Program” that is be- ing prosecuted by the League. It is merely my own opinions as to some receiver char- acteristics that should be desirable for op- eration primarily in 1929 but with a thought towards making the set satisfac- tory for the remainder of this year. When the transition occurs, a comparatively small amount of work will allow the tun- ing ranges to be modified to meet the newer conditions. We are at present doing practically all of our communicating within three bands: the 3500-, 7000- and 14000-kc, bands in which there are a total of 3500 kilocycles. What is left of these in 1929 will encompass but 1200 kilocycles and it behooves us to use all the territory open to us. Our 1750-kce. band will contain 285 kilocycles and while transmission over large distances when em- ploying low-powered transmitters is not as good there as it is in the 3500-kc. region, it should be-very satisfactory for distances not in excess of 250 miles or so. Traffic net- works, where the distance between stations is small, could be established there and the reduction in the amount of interference en- countered should help considerably in get- ting traffic through. Any receiver suitable for 1929 should, then, be capable of cover- ing the 1750-ke. band as well as the other three more popular ones. Our new 28000-kc. band has offered some possibilities, in that communication over comparatively short distances has been es- tablished. We would be very foolish not to make extensive tests to determine just how effective these frequencies are for our purposes. This gives us five bands that must be covered if we are to make ready for 1929 conditions. While it would be nice to cover also the 56000-kc. band, this does not seem to be thoroughly practical from a constructional point of view. and it would seem best to build a separate receiver (prob- ably of the double-detection type) for this band. The simplest method of constructing a receiver to cover all five bands would be to use a size of condenser that allowed that band to be covered which required the larg- est capacity range and let the other ranges fall where they may. However, there wasde- I: should perhaps be stated at the out- scribed in the April, 1927, issue of QST, under the heading of “A Traffic Tuner,” a receiver that spread each band over prac- tically the entire tuning dial scale. After handling such a set one simply hates to go back to receivers which resemble a New York subway. The subway gives you lots of space between trains but precious little within them; so does the average set treat the amateur bands, As the name implies, the “Traffic Tuner” was primarily devised for the benefit of the traffic handler who must be capable of making and keeping schedules even though conditions be poor. This requires a set that spreads the particular band in ALL PRETTIED UP which operation is desirable over a large portion of the tuning dial so that tuning, even with a comparatively fast motion dial which allows the band to be searched quick- ly will not be abrupt and critical. In the second place, the regeneration control must not have too great an effect upon the tun- ing. Thirdly, it should be possible to log signals and assuming that the signal fre- quency has not been changed to be able to go back and pick them up without wast- ing too much time. Sensitivity and stability must, of course, not be sacrificed. A receiver built with these points in mind might answer many of our 1929 troubles and if it didn’t, it would at least give us a start towards meeting them. That in it- self is well worthwhile. . The older tuner employed a conventional type of tuning condenser which goes from minimum to maximum capacitance with a rotation of 180 degrees. In this one, a Na- tional “equicycle” condenser which is rotated

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in dial space results.

THE INNARDS. capacity section. The the use of 14000-ke. are necessary. For- is a simple matter to National condenser for nges two types of National ondensers. The older is h is built into the set tograph of the newer hown separately. The and spacer thickness is * both types so no trou encountered from The main difference is of frame used to sup late assemblies. he De rting the unit for use in ver, the stator plates ar« well as the rods on are mounted. It will not ry to take the fram this operation unless ng on the rods does not * enough to allow one end d to be worked back as

band. a single capacity peless and two condensers of to cover its range is used. change needed to cover the indicated by the tables in is several times that required

is holding onto the tie rod of the tuning con-: ion. nnected to the larger section. When both sections on : . ‘ , . ther sec > C “ ed, it is clipped onto the machine screw supporting The othe ction of the con antenna tuning range machine screws and placed between two of dif the rotor plates. For convenience in wir- W y +” {} es iam gs gudsliied E s . : d €) . 1) e - 1% ms ‘t S Se SS a +S = a ‘| «> 24 | ey ’ 1 3 ’ aie TA + — = | 14 | if. 2 iS ae + > > 1 —>— i | se r ‘ ‘ oA T A ane FIGURE 1. rHE SCHEMATIC DIAGRAM OF THE SET. Ci1—350 fd. variah'e C2—Described in text. C3—Described in text. C4—100 pufds. C5—2000 pufds, Ci—.1 ufds. Ri—7 megs R2—10 ohms or more R3—Frost 50,000-ohm variable Ri—.1 to .25 megs. : : : R5—Frost 500,000-ohm variable for volume control. insulating piece. L1 will vary to suit the antenna and L2 and L3 are described removed may be cut in in the text. employed to support ew stator assemblies or else ing, the smaller capacity section is as may be replaced by four 6/32 sembled to the back of the unit and the headed brass machine screws’ other at the front nearest the panel and 1! inches long. One of these dial. The smaller section will be wired into SEPTEMBER, 1928

OST

A assemblies which will be used for the higher frequency bands employs a single stator plate and exposes one side of it to the first rotor plate. The spacing between these two plates is very important and it should be adjusted so that with the proper coil, it just covers the 14,000-ke. band with enough overlap to take care capacity effects due to antenna coupling which may be changed and which shifts the tuning slightly. In the particular set being described, more overlap * was allowed than is absolutely necessary that there should be no great difficulty in duplicating ranges even though the capacity effect of the wiring, ete., should differ by much in other ts. As a rough adjustment when reassembling the condenser, make this spacing the equivalent of the thickness of eight QST pages. The final adjustment will | he set is in opera- ot SO the S¢ be made when t

coil is not denser may consist of a single plate or if double spacing is thought desirable two stator plates This should be used. It is mounted on a pair of

—raeg oe wD Ores Sew ct aeons ss oe a, —_

Page 39

1928 higher Stator he first ese two uld be proper 000-ke. to take due to nay be ts the ticular verlap olutely yuld be icating h the g, etc., other stment lenser, valent QST it will opera- > con- single ng is plates air of wo of | wir- ee, R9 ribed as- the and into SEPTEMBER, 1928 the circuit permanently while the larger section will be connected across it for the 1750-ke. band. A switch could be structed for this change but would probably result in mechanical difficulties. To simpli- fy matters, a piece of flexible wire was connected to the larger section stator plate and the clip on its end may be snapped onto the machine screw supporting the stat plate of the smaller section or onto th frame of the condenser thus grounding th larger section when it is not in use. It makes a workable and practical arrang ment involving the use of no great amount of mechanical ability or equipment as might a more beautiful appearing switch. Ther is no need for its being operable from th front of the panel because it will need to | shifted only when it is con- desired to THE NEWER TYPE OF EQUICYCLE CONDENSER AND HOW IT IS CONVERTED FOR THE JOB It shows the larger capacity section as consisting of two stator and three rotor plates with double spacing. This section may consist of just one stator and two rotor plates with normal spacing. Neither is it necessary to remove the unused rotor plates. ft j on a different band ane change coils when making such a shift, no hardship is imposed by requiring that the clip changed. The only other point to cerning the condenser is the use of the Ham marlund “neutralizing” conde T allows a band that is either above the U. S. bands to be covered so that, for instance, those foreigners working around 8330 kes. may be received. The circuit It will be noted tuned after the Bourne on page 36 of the allows the antenna tuning and be varied independently and if coupling is to be employed for the 1750-ke band it is of great help in building up the 1recessary to also be diagram is given in Fig. 1. that the antenna circuit is fashion described by R. August issue. I coupling to capacit OST 41 ignal strength. What is more important, helps on the signal noise ration. A large ining condenser is used and the coil should e of such dimensions that the antenna cir- ‘uit will tune over the 1750-ke. band. Har- = onic tuning will be employed for the higher FORM WITH 7000-KC. COIL WINDING ON IT THE PILOT THE frequency bands and the coil will not have to be changed for them. No switching ar- rangement has been provided for discon- cting the tuning circuit other than the an extra binding post. If such is may be installed without a great If a very long antenna is ised, the tuning coil and condenser may ‘d in by connecting the oil across the two antenna binding posts. } ] > duneshi aeal of troupie. e connecte series The antenna coupling condenser consists two small brass plates. One is some- vhat larger than the other (it happened to be available and was not cut down) and aller is approximately % inch square 1d is soldered to a piece of heavy bus bent in the form of a “U”, the sides of which pass under the head of a binding post. Spacir ip to an inch and a quarter may be ad Coup should be made loose and he 9 stage audio amplifier relied upon x obtaining good signal strength. The coupling the less effect will the antenna tuning have upon the calibration * the tuning dial and the less need there will or using the regeneration control. The coils are wound on Pilot forms, one of wl is shown next to the tuning con- denser. When using such small tuning ca- pacitic one really begins to appreciate he tuning effect the tickler coil has upon the circuit. In the 14,000-and 28,000-kc. bands, it is possible to shift the tuning very materially by changing the number of one, this with tickler coils wire. The tickler seems tickler turns by of No. 30 s.s.c¢. 0 the smallest effect on loading the st lary circuit and detuning it when the least number of turns is employed. The coils were wound about % of an inch below the filament end of the secondary winding and the turns reduced one at a time until the circuit would not oscillate over the en- of the tuning condenser. After tire range the minimum number of turns was obtained,

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OST SEPTEMBER, 1928 nding was shifted away from the lary until the loosest coupling was 1 without causing the regeneration become cranky and irregular. The a smooth control of regeneration slight detuning effect. The use rge coil with looser coupling causes r detuning. use of a 2000-wufd. by-pass condenser the battery side of the tickler coil nent helps materially in the prob- 30 so 70 30 uo 130 150 RE 2. THE TUNING CURVE FOR THE 3500-ke. COIL. how the number of dial divisions for a e will change depending upon the particu- the scale being used. neration. A small condenser in n makes it necessary to increase the tickler coils with its ac- ng troubles. As the size of the by- enser is increased, it tends to by- of the higher audio, frequencies is in shunt of the primary of the nsformer. While this may be dam- nsidered as an assistance in a set ing telegraph signals in that it reduce the hissy background. It has » effect upon signals in the lower nge to which they are usually tubes of the ’99 type are used. have been equipped with long prongs that make decent contact, not half so troublesome and are e as oscillating detectors for high work. Fringe howl has been isual by shunting a .1 or .25 meg s the secondary of the first audio transformer. The transformers are de- signed for music and so we are not dis- criminating against a large percentage of the signals on the air. Separate B leads are provided for the two audio amplifying tubes so that on nights when the static is very bad, the plate voltage to the first am- plifier tube may be dropped to a volt or two and thus by its limiting action, one to one ratio between the signal and static can be obtained. This is a stunt that has been mentioned before in QST and was recently suggested again by Paul G. Watson of West Chester, Pa. The phone cords do not come to the panel at all and, therefore, won’t al- ways be getting in the way. Coil sizes are as follows: Degrees to Number Turns cover band Band in kes. Coil Range Sec. Tickler 1928 1929 1500-2000 1395-2055 65. 9 106 40, 3500-4000 3371-4027 46.25 5 116 116 7000-8000 6897-8000 16.25 4 133 21 7940-9755 16.25 4 14000-16000 13510-16300 7.25 4 114 11 11760-13640 7.25 4 28000-30000 27650-30380 2.25 3 40 40 The 6879-8000-ke. and the 11760-13640- ke, ranges are obtained with the shunt ca- pacity in the circuit while the other ranges for the same coils are obtained without the shunt condenser. The value of this con- denser is determined by shunting it across the tuning condenser and increasing its capacity until when with the tuning con- denser at about 10 degrees, the frequency is slightly below that obtained when there is no shunt and the tuning condenser is set at 150 degrees. It would, perhaps, better be adjusted with the 14000-ke. coil which band is covered without the shunt capaci- tance in the circuit. The secondary coils are wound with No. 26 d.c.c. wire excepting in the case of the 1750-ke. coil which is wound with No. 30 s.c.c. which is used for the tickler coils. The ticklers are close wound and are spaced about %” from the filament end of the sec- ondary windings. The 1750- and 3500-kc, coils are close wound while the spacing be- tween turns of the 7000- and 14000-kc, coils is the diameter of the wire used. In the case of the 28000-ke. coil, it was found necessary to wind the secondary coil with about %” spacing between turns and then wind the tickler coil between the turns. If the tickler were wound below the secondary in the usua fashion, it would probably call for at least two or three more turns which would require that the number of secondary turns be reduced still further. Fig. 2. gives a typical tuning curve. It happens to be for the 3500-kc. band but is similar for the other range. The thing to be pointed out is that the number of divisions of dial space to cover a band (Continued on Page 68) \SEP iSon char our sign eral not first not now suec and stat of 1 the cha) uar 771) 154! stat find duc com ran be our or 35, Cor ber trai pre ind: stat “W an¢ ting the Ser actu deer Octe new Stat rath 1925 edit clas the call Hay add call and

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1928 e de- t dis- ge of leads ifying itic is t am- ir two oO one an be been rently West come ’t al- 40 3640- t ca- nges t the con- “Toss r its con- ency here ; set otter hich yaci- No. the 30 oils. aced sec- )-ke, be- ‘oils pase ary 1% od the kler the > & yuld rns It but ing of and |ISEPTEMBER, 1928 OST 43 Washington Developments ‘Sommercial Assignments in Our Bands; Amateur Calls Changed; Amateur Extra E have previously mentioned in QST that 21 channels between 7300 and 8000 ke. (part of our present “40-meter” band) and 27 channels between 14000 and 14400 ke. (in our present “20-meter” band) have been as- signed to commercial interests by our Fed- eral Radio Commission, because these will not be amateur frequencies after January first and because United States stations will not get the use of them if they do not start now. Construction permits have been is- sued for the use of many of these channels and it is now expected that many of the stations will be in operation before the end of the year. This applies particularly to the Radio Corporation group. R.C.A. channels on which operation prior to Jan- uary Ist is likely are: 7400, 7415, 7520, 7715, 14800, 14830, 14920, 15040, 15430, 15460, 15490, 15970 and 16000 ke. As these stations one by one come on the air we shall find our operating territory gradually re- duced, but by the same token the foreign commercial stations now operating in the ranges 7000-7300 and 14000-14400 ke. will be moving out, for they must be clear of our 1929 bands by the first of the year. NEW AMATEUR CALLS As anticipated in our August issue, page 35, the Radio Division of the Department of Commerce announces that, effective Octo- ber 1, 1928, all amateur, experimental and training school station calls are changed by prefixing the existing call with a letter to indicate nationality, as required by the Washington Convention. The prefix for stations in continental United States is “W”, while for those in distant territories and possessions it is “K”, to permit dis- tinguishing them from continental calls of the same district. Quoting from the Radio Service Bulletin for June 30th: While the requirements of the convention are not actually effective until January 1, 1929, it has been deemed advisable to change the call signals effective October 1, next, as the Division desires to show the new signals in the annual list of Amateur Radio Stations of the United States, edition June 30, 1928, rather than to change the calls effective January 1, 1929, and publish the new calls in the June 30, 1929, edition. Therefore, beginning that date, all stations in the classes above named within the continental limits of the United States are hereby ordered to add to their call signals the letter “W’, and those in Alaska, Hawaii, Porto Rico and the Virgin Islands, should add the letter “K’’. These letters should precede the call signal; for example, station 4ABC, if within the ‘ontinental limits of this country, becomes W4ABC and, if in Porto Rico, becomes K4ABC. It is important to note that the prefixes First Class Operator’s License Restored. “Ww” and “K” are not to be used before October first. On that date, however, their use commences, with the old intermediate “de” and the abandonment of “nu”. In passing, let us mention again that every amateur ought to subscribe to the Radio Service Bulletin. It contains much important information. It cost sbut 25c per year (stamps not accepted), from _ the Superintendent of Documents, U. S. Gov- ernment Printing Office, Washington. Aside from the fact that Canada is go- ing to use the letters “VE”, we have no re- liable information on the prefixes that oth- er countries will use for their amateur calls. As it does not seem likely that we will have a complete list before the year is out, we print below the international table of allo- cation of call signals from the Washington Convention. Nations are obliged to select some letter or letters from their assignment to use as a prefix to amateur calls, but we can not tell at this date what they will be. Where a nation is given all combinations beginning with a given letter, as in the case of “W” for the United States, that single letter will suffice; but where a letter is par- titioned amongst several countries, like “7”, two letters will be necessary. One cannot say to-day, for example, whether New Zealand amateurs will use the prefix “7K”, “ZL” or “ZM”. This list, therefore, is of no aid in making calls but will be help- ful in determining the identity of calls heard. BEE. tvtbcneedeeen eeeeeetaleendseeagenaes CAA-CEZ CE . nc dc veeserestucenetnceeddeantene CFA-CKZ Sain iadubivn ti gee seen en eenbeseans CLA-CMZ ee re ee er ye CNA-CNZ DED ci cocudteddundebeasookbiadtsiewees CPA-CPZ ee Rrra ee CRA-CRZ DET ccc cena esac sadness esnnGhaene one CSA-CUZ EEE: ccvcrbdteaetenesanaeessenenens CVA-CVZ TS cc ound candenvecnecosesaesuunee CWA-CXZ , cic ot ndeensahes cease iawnseeeeeees CZA-CZZ ee SEPPREPOTCCTTTCTTT CCT CT TTT D PEE 5a 6) 4ioense 0 dtecdsensaehoaswans een EAA-EHZ BrEG WOO BtASe 2c cccccccccsececeeseseses EIA-EIZ OE OSC rer ee er ELA-ELZ SSFP OTET TTT TCC ESA-ESZ Ethiopia ; SE eS See ETA-ETZ France and colonies and protectorates .... F Grant BEAM ccccccicccccccvconccecsseses G i ac eeen the eee eee wai ae HAA-HAZ ED cn ccccktossadscannaveaneesen HBA-HBZ ee errr rr ee HCA-HCZ =a iS 2 = eeerererer rere toes HHA-HHZ Cemmemees TORS 6 vccscccncucevestesses HIA-HIZ Republie of Colombia .......cccccccceces HJ A-HKZ Republic of Honduras ........-seeeeeeee HRA-HRZ SE. conatieinienen mace jensktinndanenares HSA-HSZ Italy and colonies . biandeadabeateneseu I SOME cccececes pbnteedeeeenes — United States of America .........+++4++ kK Norway .....--. ass oe bite a ow he Ge ee RL LAA-LNZ Argentine Republic ..........-+++eeeeee LOA-LVZ

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~ LZA-LZZ M N OAA-OBZ OHA-OHZ OKA-OKZ ONA-OTZ OU A-OZZ PAA-PIZ PKA-P osece PPA-PYZ eeese PZA-PZZ RAA-RQZ RVA-RVZ secce RXA-RXZ RYA-RYZ SAA-SMZ SPA-SRZ SUA-SUZ SV A-SZZ TAA-TCZ TFA-TFZ TGA-TGZ TIA-TIZ TSA-TSZ UHA-UHZ UIZ-UKZ ULA-ULZ ( Ss t UNA-UNZ UOA Z VAA 1Z \ VHA- Z, V \ Z VPA-VSZ VTA-VW Ww xX Xe Y YI y Y) YN ys yV\ Z. ZK ZP ZSA-ZUi \ LICENCE RESTORED here called to the kind the Radio Division, of th Class Amateur Operator edalt ION that is license. toria ipervisors ot ue th Radio are now For further this month should FREQUENCIES a generation order wil 1? Federal Radio Commission in iture, authorizing amateurs witl ransmission 1 pi 1715-2000 **160- thin me thes« ‘ture transmission n within the fre- ke. and 56,000-60,- er” and “5-meter”’ two bands only. OST SEPTEMBER, 1928 This has no reference to the frequencies used by broadcasting and experimental sta. tions for popular consumption, but refers only to transmissions by amateurs them. selves. THE GOVERNMENT CALL BOOK Amateurs are not adequately supporting the very splendid call book, List of Amateur Stations of the United States, published an- nually by the government for the modest sum of twenty-five cents. Only about 5,000 copies are sold annually. With 17,000 amateurs in this country there should be bieger support. It costs the Radio Divi- sion over $3,000 of their appropriation to have this list made available for popular ss there is more evidence that the list is in demand the Division may dis- continue its publication. The book will appear in September or October and will be complete to June 30th. It is accurate, and it deserves our support The Radio Division having paid the entire cost of composition, the 25¢c charge repre- sents only the cost of paper and handling. Orders should be addressed to the Superin- tendent of Documents, Government Print- ing Office, Washington, and remember that stamps aren’t accepted. Last year some purchasers were erroneously advised that the supply was exhausted and their money was returned, but this year we are assured of an ample supply. CHANGES IN ALABAMA On July 1st the Radio Division, for ad- ministrativ convenience. transferred the state of Alabama from the Fifth District , i nder Major Van Nostrand at Atlanta. This necessitated the ] _ —_ f anging of Alabama amateur calls from 5s to 4’s. Applications were sent all amateurs early in June and 4th-district licenses, dated July 1, were issued as fast as applications came in, so that those who responded promptly will be correctly listed in th June-30th issue of the government all book. In many cases the same combina- tions of call | were given the stations; in other cases two- or three-letter calls were given them according to what they had while in the Fifth District. Major Van Nostrand kind supplies us with the fol- lowing list of Fourth District calls in

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1928 iencies il sta. refers them. »rting ateur 1odest 5 000 7,000 Divi- mn to pular that dis- — 50th. port ntire ‘pre- ling. erin- ths at some that mney ired ad- rict Van the 1 5s urs ted ons led the ‘all na- 18: Ils ey an in SEPTEMBER, 1928 W4AIB George Woods Fahrubel 500 Miller Ave., Birmingham W4AIE Leonard William Thomas 115 Kate Ave., Birmingham W4AIM_ Hdars. Co. 3rd Bat., 167th Inf., Ala. Natl. Guard 1800 2nd Ave., Birmingham W4AX Joe Wheeler Clancy 1316 17th St., S., Birmingham WwicD Alabama Natl. Guard, 106 Obsn. Sqdn., Air Corps Roberts Field, Box 570, Birmingham w4DS William Alonzo Boon 216 Pine St.. N. West End, Birmingham W4GG Edward Florien Herzog 1007 ¢ rescent Ave., Birmingham W4HI D. J. Connolly 1530 N. 20th St., Birmingham wiJY I. J. Jones 388 llth Ave., Birmingham W4MY Wendel] H. Binkley 1400 30th St., N., Birmingham W14OM Walter Martin Garrard 1430 N. 12th Court, Birmingham W4RE H. L. Ansley 1428 N. 12 Ave., Birmingham W1iVC M. B. Drennen 510 St. Charles Ave., Birmingham W4AHZ Leonard C. Kron 1719 29th St., Ensley W4AIO Aubrey Whitney Fayette Ww4iUV Julius Clarence Vess« Fayetteville W4AIA Arthur & Viola Hook P. O. Box 127, Foley W41ET Robt. L. Brackett Ft. Morgan (Mail c/o United Fruit Co., Mobile) W4AID Raymond N. Jones 903 S. 10th St., Gadsden W4PAR Joseph E. McCormack 246 S. 5th St.. Gadsden (Portable) W4RC Joseph E. McCormack 246 S. 5th St., Gadsden W4ACX James IL. Kelly Hazen W4AHY J. W. Hudgins 104 Oakwood Ave., Huntsville W4MB Wilton H. Pollard 104 White St., Huntsvill W4SN Charles Forrest Striplin, Jr 724 E. Clinton St., Hunts W4AAS Thomas Joseph Peddy Loachapoka W4AAJ Chas. E. Emrich 55 S. Joachim St., Mob W41OA James Robertson 264 N. Conception St., Me wiws Norman Sinclair Hurley 160 Marine St., Mobil W4AAQ Samuel Jefferson Bayns 108 Cramer Ave., Montgomer W4AHO Alexander D. Trum 217 Catoma St., Montgomery W4AHP Robert Edward Troy, J 516 Cloverdale Road, Mont W4AHR ow rew C. Kilpatrich ’ , Montgom W4AHS ohn Brown St., Montgomery W4AIP alee Maurice Gantt -arkway M I V4AN John Craver Howe! Ave AHU Basil B. McGinty W4AlH Terry L. Geurrant St... na W4AIL Henry W. Fulwider Selma WwiDJ William H. Dent Selma W4FN Walter W. Merl Selma W4IA L. Tennett Lee, Jr t.. Selma W4PAS R. B. Sommerville St., Selma (Portable) W4TH Karl William B g i St., Selma W4TI R. B. Sommerville Ss Selma wv Carroll M. W. E . Box 834, Selma W4AIK Leslie B. Stanton Tuscaloosa W4AHV Ra'ph A. Ower Ave., Tuscumbia W4AIC Earl Campbell Schrimsher i833 6th Ave Wylam SUPERVISOR KOLSTER COMMENDS US Manual, he must be best known as one of In the annual report of the Supervisor, OUF most helpful friends at the W ashing- First District, to the Radio Division, Super ton international conte rence—see January visor of Radio Kolster comments as follow QST. Our congratulations and best wishes to both oficers: under the subject of “Interference” “IT wish to bring to the attention of the Division the splendid coéperation extended to this office by the amateurs who volun teered their services in connection with S@>-Strays $s this investigation work” . — We’re proud of that. -K. B. W. If you substitute for the crystal a wave- CAPTAIN HOOPER NOW D. N. C. meter or any tuned circuit, tuned to the Captain S. C. Hooper, in charge of the same wavelength as the crystal, during the adio section, Bureau of Engineering, — Ss, “tuning up” process, you will not be so apt to have a crystal “transmitter” and a broken Ni VY, and lately assigned as Technical « : Commission crystal when it comes time to work the set. After all the preliminary adjustments have been made, the crystal can be put back in the circuit.—3CKL + sor to the Federal Radio h: een appointed Director of Naval Com cations at Washington, relieving Capt Thos. T. Craven, who has been promoted Rear Admiral and transferred, we believe to sea duty. Like Admiral Craven befor him, Capt. Hooper is a splendid friend of A description of their line of uniform- the amateur. He has known us longer than size meters for transmitters, and some dope any of his predecessors in that office. Al- on the uses of various meters, is in the hough known to amateurs as one of th Weston Electrical Instrument Corp. new oint revisors of the well-known Robison’: circular J. Better get one.

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OST SEPTEMBER, 1928 Experimenters’ Section rs of the Experimenters’ gether with the rest of the fraternity, are faced with ‘oblem of meeting the more or | ange in operating conditions wh ruration of the provisions of the I nal Radio Conference of 1927 will is January first of next year. We |} r been licked by frequency re- strict re, and we are not going to be | time. It is quite obviously not lient but also necessary that the | xperimenting amateurs con- cent1 r activities on the technical pha 1ring to cope with the not far tuation, and that the Experi- ment n as the organized body of thes« nting amateurs tackle those tecl blems bearing most directly 1 1 hing situation. co} ON PROBLEMS TO MEET 1929 ONDITIONS W wpoint in mind the list of x § blems has been somewhat modifi le most of the old problems hat tained, the scope of several has | red and several new problems have | 1. Four problems have, for self ns, been eliminated, The pr - problems is as follows: ENNA CIRCUIT \ and feeder systems. Al nsmission and reception. AT und antennas. EPTION R1 uency amplifiers for ama- R1 ' obtaining audio frequency NSMISSION uency chokes for transmit- T27 ion and reception on 28,000 Ke., (1 r), band including antenna 73 n and reception on fre- quer 56,000 Ke., (wavelengths be- ] : T33-C juency transmitters . Glar r the list, it is seen that A10 has | red to specifically include feeder , while Al2 and A138 are as befor ng problem R12, while speci- ficall; ng radio frequency ampli- fiers, ncompasses every type of receiv r the superheterodyne. R13 is an n, and one which is un- doubtab! ve of great value in adapting receive! 1929 conditions. Th tting problems T25 and T26 1, while old problem T27, hav- ing outlived its usefulness, has been replaced by new problem T27 made necessary by opening of the 28,000 ke. band. T28, port- able Transmitters, has proven more the question of mechanical design in adapting a low power transmitter for portable use than a real experimental problem, and has therefore been eliminated. T30 and T31 have been combined as T30, while T32 has been enlarged to include all constant frequency transmitters as T33. General problems G12 and G13 are so obviously general in their nature and remote from the big problem be- fore the amateur at this time that they have been eliminated. Due to the wide scope of each problem and the desirability of having each experi- menter concentrate to the greatest pos- sible extent on the problems he may select, not more than TWO problems are to be chosen from the list by each member. If at some future time, however, the ex- perimenter should decide to substitute a dif- ferent problem for one first chosen, he may do so by writing Headquarters, advising the change. Experimenters at present enrolled for problems which have been discontinued on the new list should not drop their activities on these problems, but should continue to a conclusion and report on these problems as usual, Outlines suggesting a method or methods of attack on the problems as well as a list of references of material are being prepared for each problem and will be sent to mem- bers enrolled for the respective problems as soon as the preparation is completed. There is work to be done by every experi- menting amateur now as never before, and new members for the Experimenters’ Section are needed and wanted. All desir- ing to be enrolled should do so at once—just address the Experimenters’ Section, Ameri- can Radio Relay League, 1711 Park St., Hartford, Conn., and state that you wish to join the X Section. J.J. L. t+, seo, =p hh aa

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SEPTEMBER, 1928 OST Mica Condensers For High Frequency By Arthur M. Trogner* recent article in QS7 gave some explanation of the necessity for symmetrical arrangement of con- denser units when used in parallel in high frequency transmitting ‘circuits. This is no new conception or principle, but, like a lot of other fundamental rules it is of such small moment in intermediate and low frequency circuits that it can usually FIG. 1. THE THICKNESS OF THE DOTTED LINES THROUGH THE CONDENSERS SHOWS ROUGHLY HOW THE CURRENT WILL DISTRIBUTE ITSELF be neglected there. In the high frequency field the effects of a neglect of this princi- ple of symmetry will not be pleasant unless your pocket-book is well lined and you de- light in making business for the small con- denser makers. What is meant by this symmetry can best be explained by first showing what not to do and why. Fig. 1 shows several com- mon methods of connecting small fixed con- FIG. 2. SHOWING THE DISTRIBUTION OF THE CURRENT IN A COIL WOUND WITH ROUND CONDUCTOR Of course, there will be some current flowing at the outer surface and even in the center but the percent- age of the total current which flows along the inner surface will increase as the frequency is increased. denser units in parallel when greater cur- rent carrying ability, greater capacity, or both are desired. It is obvious that the paths from “A” to “B” in 1 (a) are not the same length through both condensers. From your own work with high frequencies you know what an appreciable difference in *Formerly at U. S. Naval Research Laboratory. Now with Wired Radio Inc., New York City. inductive reactance such small differences in physical circuit length may mean. This difference in inductive reactance will force most of the current to flow through the lower reactance path and very probably burn out that condenser. In the figures the different thicknesses of the dotted lines in- dicate (very approximately only) the pro- portion of the total current which will flow through each condenser in the various ar- rangements. If you are counting on using nearly the full current carrying capacity of each condenser in the combination, it is easy to see that burnt-out condensers will be the result. Adding more condensers in parallel such as 1 (b) and 1 (c) even though the physical lengths of the separate paths may be the same will not cure the trouble to any appreciable degree since the GROUPS OF FOUR CONDENSERS MOUNTED IN PARALLEL SHOWING A SINGLE GROUP AS WELL AS TWO AND THREE GROUPS IN SERIES outside condensers will still carry most of the current for the same reason that high frequency currents are crowded to the sur- face of a conductor on which they are traveling. The inside condensers, or the inside of the wire, are paths of higher in- ductive reactance than the outside and ra- dio frequency currents always travel in the path of least inductance even though this results in higher circuit resistance. An- other example of this is shown in Fig. 2 which shows roughly the character of the current distribution in the conductor of a coil carrying high frequency current. The current is crowded to the inside surface of the wires since the outer surface of the turns, being cut by more lines of force, has a higher inductive reactance. This will be easy to see if you remember that the in- ner surfaces are cut by the flux which is in- side the coil, whereas the outer surfaces are cut by this same flux plus the flux which distributes itself between the inner and outside surfaces of the wire. (See More- croft, Principles of Radio Communication, page 125 first edition or page 156, second

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W rn is one reason why coils c opper strip are so effec- ‘equency work; there is not C ‘opper on the outside of 1use eddy current losses. is to the right way to connect parallel. Put each condenser oO ‘ A 1¢ equal inductance. This 3 for various com- Y have tried this out and worthwhile every time. irrangements, each con- fy CONDENSERS SHOULD BE CON- PARALLEL TO OBTAIN EQUAL TION AT loys n } L ar OF CURRENT THROUGH THE UNITS y its share of the each condenser in any tion should be at least of capacity otherwise the dif- tl ve reactance thus form- rHE 20-KW. TUBES the same principles as do the eh it has been necessary to change rement somewhat. This unit has {d » parallel with five sets in series. It units which are built to stand ) d.c. The total combination has fds. and has been tested to 35 O¢ It is only needed where 10- led tubes are being used. current to flow through s and might overload well to point out here OST SEPTEMBER, 1928 that the usual difficulty with condensers at these high frequencies is not voltage break- down but heating and failure of the dielec- tric. In Fig. 4 is shown detail dimensions of standard parts which have been found very useful here at the Laboratory. These parts provide for 4 units in parallel and by using the ring fittings shown, such parallel units can be readily arranged with 2 or mor: sections in series where needed to take care No 8-32 Jap ‘* lig ~ No 6-32 Tap —~ ->4 zi END FITTING 25" ol ee | 6 ; r eee RING FITTING FIG. 4. DIMENSIONS OF fTHE MOUNTING UNITS TO CONNECT FOUR CONDENSERS IN PARALLEL Connection to the rest of the circuit is made through S x 32 machine screws run into the threaded holes in the center of the end fittings. The ring fitting is employed to connect sets of four condensers in series. Several sets may be so connected making a_ solid mechanical as well as good electrical unit. of high plate voltages, and the like. Fitting of similar construction are employed to mount six condensers in parallel. It might be well to add a few words about choosing the proper kind of con- denser units to use. One of the benefits to “Hamdom” from the coming of the BCL is the improvement in many radio parts available on the market. Among these are greatly improved small mica condensers. Originally intended mainly for use in re- ceivers, it has been found that the better types, constructed of the best materials to rigid standards, are just the thing for use in high frequency transmitters. Notice that I did not say that all small mica con- densers are good for transmitter work. of of of ‘Jf > wel am itp tt toe,

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SEPTEMBER, There are many makes of condensers on the market which are all right for use in receivers, but which will not stand up un- der the severe loads found in transmitters. The difficulty with most condensers of this type is that their internal high. Often this is true only when the con- denser is passing appreciable currents which accounts for the fact that such con densers may be good low-loss units for re ceivers and yet fail in transmitter use A suggested set of rough specifications is losses are too given below. The units should be entirely enclosed to prevent accumulation of dust and moisture across and between the edzes of the mica sheets. A complete -water-tight since only a enclosure is to be preferred slight amount of moisture may cause a rapid i Condensers should be capa- ble of carrying the currents specified in the table below without exceeding an ultimat: emperature rise of 10° C above surround rise in losses. ing temperature. Capacity R. F. amps. at 6000 Kes } amps. 0096 to 00099 mfd 1 amps. 001 mfd. and larger 5 amps. 0002 to 00059 mfad 2@e ELECTION NOTICES To All A.R.R.L. Members Res‘ding in the Central, Hudson, New England, Northwestern (including Territory of Alaska), Roanoke, Rocky Mountain and West Gulf Divisions: 1. You are hereby notified that an elec tion for an A.R.R.L. Director, for the term 1929-1930, is about to be held in each of the above Divisions, in accordance with the Constitution, Your attention is invited to Sec. 1 of Article IV of the Constitution, providing for the government of A.R.R.L. affairs bv a Board of Directors; Sec. 2 of IV, defining their eligibility; and Laws, 14, 15, 16 and 17. providing fo: nomination and election. 2. The election will take place during the month of November, 1928, on ballots vl will be mailed from Headquarters in the rst week of that month. The ballots for each Division will list the names of all li candidates nominated for the posi tion by A.R.R.L. members residing in that Division. Nominating petitions are hereby solicited, Ten or more A.R.R.L. members Division have the privileg« member of the Leagi living in any ff nominating any 1928 OST 49 in their Division as a candidate for Direc tor. The following form for nomination is suggested: (Place and date) Executive Committee, A.R.R.L. Headquarters, Hartford, Conn. Gentlemen: We, the indersigned A.R.R.L. residing in the Division, hereby nominate RCO te ee re ee as a candidate for this Division for 1929-1930. (Signatures) The signers must be League members in good standing. The nominee must be a League member in good standing and must e without commercial radio connections. His complete name and address should be given. All such petitions must be filed at the headquarters office of the League in Hartford, Conn., by noon of the first day of November, 1928. There is no limit on the number of petitions that may be filed, but no member shall append his signature to more than one such petition. 1. Present Directors from these Divi- sions are as follows: Central, Mr. Clyde E. Darr, Detroit; Hudson, Dr. Lawrence J. Dunn, Brooklyn; New England, Dr. Elliott A. White, Hanover, N.H.; Northwestern, Mr. Karl W. Weingarten, Tacoma; Roanoke, Mr. W. Tredway Gravely, Dan- ville, Va.; Rocky Mountain, Mr, Paul M. Segal, Denver; West Gulf, Mr. Frank M. Corlett, Dallas, 5. This is your opportunity to put the man of your choice in office as the repre- sentative of your Division. Members are urged to take the initiative and file nomi- nating petitions immediately. For the Board of Directors: K. B. WARNER, Secretary. Hartford, Conn., 1 September, 1928. 2p-Strays "$5 Reports have been circulating in amateur radio that the UV-203-A 50-watt tube is no longer available. The rumor is untrue. The must be ordered in New York. Only ibe is still available, but direct from the R.C.A. the UX and the UX-210 are available from dealers. All the other transmitting tubes are sold under a sales agreement, through the Engineering Products Division, Radio Corporation of America, 233 Broad- way, New York. Requests for information on, and orders for all transmitting and power rectifying tubes other than the 852 and the 210 should be addressed to that qgivision., -R5?

Page 48

is one reason why coils copper strip are so effec- ‘equency work; there is not s copper on the outside of 1use eddy current losses. to the right way to connect parallel. Put each condenser equal inductance. This Fig. 3 for various com- Vv have tried this out and is worthwhile every time. arrangements, each con- NS @ W CONDENSERS SHOULD BE CON- N PARALLEL TO OBTAIN EQUAL BUTION OF CURRENT THROUGH ALL THE UNITS carry its share of the irse, each condenser in any ination should be at least of capacity otherwise the dif- pacitive reactance thus form eee R THE 20-KW. TUBES nploys the same principles as do the Ithough it has been necessary to change rrangement somewhat. This unit has n parallel with five sets in series. It ifd. units which are built to stand 5,000 d.c. The total combination has ifds. and has been tested to 35 kes It is only needed where 10- r cooled tubes are being used. re current to flow. through and might overload be well to point out here pacities OST SEPTEMBER, 1928 that the usual difficulty with condensers at these high frequencies is not voltage break- down but heating and failure of the dielec- tric. In Fig. 4 is shown detail dimensions of standard parts which have been found very useful here at the Laboratory. These parts provide for 4 units in parallel and by using the ring fittings shown, such parallel units can be readily arranged with 2 or mor sections in series where needed to take care Es - 8; ' Y ~~ Ne 6-32 Tap ~~ —»4 END FITTING RING FITTING DIMENSIONS OF fHE MOUNTING UNITS TO CONNECT FOUR CONDENSERS IN PARALLEL Connection to the rest of the circuit is made through s x 32 machine screws run into the threaded holes FIG. 4 in the center of the end fittings. The ring fitting is employed to connect sets of four condensers in series. Several sets may be so connected making a_ solid mechanical as well as good electrical unit. of high plate voltages, and the like. Fitting of similar construction are employed to mount six condensers in parallel. It might be well to add a few words about choosing the proper kind of con- denser units to use. One of the benefits to “Hamdom” from the coming of the BCL is the improvement in many radio parts available on the market. Among these are greatly improved small mica condensers. Originally intended mainly for use in re- ceivers, it has been found that the better types, constructed of the best materials to rigid standards, are just the thing for use in high frequency transmitters. Notice that I did not say that all small mica con- densers are good for transmitter work. 00 00 on 1 t N j

Page 49

1928 ielec- is of very yarts ising units mo car zh les is es lid There are many makes of condensers on the market which are all right for use in receivers, but which will not stand up un- der the severe loads found in transmitters. The difficulty with most condensers of this type is that their internal losses are too high. Often this is true only when the con- denser is passing appreciable currents which accounts for the fact that such con densers may be good low-loss units for re ceivers and yet fail in transmitter use. A suggested set of rough specifications is given below. The units should be entirely enclosed to prevent accumulation of dust and moisture across and between the edzes of the mica sheets. A complete water-tight enclosure is to be preferred since only a light amount of moisture may cause a rapid rise in losses. Condensers should be capa- ble of carrying the currents specified in the table below without exceeding an ultimate a temperature rise of 10° C above surround ing tempe rature. Capacity R. F. amps. at 6000 Kes 0002 to 00059 mfd } amps. 0096 to 00099 mfd 1 amps. 001 mfd. and larger 5 amps 2@e ELECTION NOTICES To All A.R.R.L. Members Res‘ding in the Central, Hudson, New England, Northwestern (including Territory of Alaska), Roanoke, Rocky Mountain and West Gulf Divisions: 1. You are hereby notified that an elec tion for an A.R.R.L. Director, for the term 1929-1930, is about to be held in each of the above Divisions, in accordance with the Constitution. Your attention is invited to Sec. 1 of Article IV of the Constitution, providing for the government of A.R.R.L. affairs by a Board of Directors; Sec. 2 of Article IV, defining their eligibilitv; and By-Laws, 14, 15, 16 and 17, providing for their nomination and election. 2. The election will take place during the month of November. 1928, on ballots which will be mailed from Headquarters in the first week of that month. The ballots for each Division will list the names of all si le candidates nominated for the posi tion by A.R.R.L. members residing in that Division. Nominating petitions are hereby solicited, Ten or more A.R.R.L. members living in any Division have the privilege f nominating any member of the League SEPTEMBER, 1928 OST 49 in their Division as a candidate for Direc tor. The following form for nomination is suggested: (Place and date) Executive Committee, A.R.R.L. Headquarters, Hartford, Conn. Ge ntl nven: We, the undersigned members of the ATE Es: GOCE TE TAD oc voce cccescennn Division, hereby nominate .............. OS ee .., as a candidate for Dire ctor from this Division for 1929-1930. (Signatures) The signers must be League members in good standing. The nominee must be a League member in good standing and must without commercial radio connections. His complete name and address should be given. All such petitions must be filed at the headquarters office of the League in Hartford, Conn., by noon of the first day of November, 1928. There is no limit on the number of petitions that may be filed, but no member shall append his signature to more than one such petition. 1. Present Directors from these Divi- sions are as follows: Central, Mr. Clyde E. Darr, Detroit; Hudson, Dr. Lawrence J. Dunn, Brooklyn; New England, Dr. Elliott A. White, Hanover, N.H.; Northwestern, Mr. Kar] W. Weingarten, Tacoma; Roanoke, Mr. W. Tredway Gravely, Dan- ville, Va.; Rocky Mountain, Mr, Paul M. Segal, Denver; West Gulf, Mr. Frank M. Corlett, Dallas. 5. This is your opportunity to put the man of your choice in office as the repre sentative of your Division. Members are urged to take the initiative and file nomi- nating petitions immediately. For the Board of Directors: K. B. WARNER, Secretary. Hartford, Conn., 1 September, 1928. —eeStrays) Reports have been circulating in amateur radio that the UV-203-A 50-watt tube is no longer available. The rumor is untrue. The tube is still available, but must be ordered direct from the R.C.A. in New York. Only the UX-852 and the UX-210 are available from dealers. All the other transmitting tubes are sold under a sales agreement, through the Engineering Products Division, Radio Corporation of America, 233 Broad- way, New York. Requests for information on, and orders for all transmitting and power rectifying tubes other than the 852 and the 210 should be addressed to that division.

Page 50

SEPTEMBER, 1928 vy i J va \ : yy i ) \\ ~ mu . \ Ww O\s ah MY lh AY a\\ al i IN wa* Conducted by A. L. Budlong this report is being written, a / number of replies have come in rom Presidents of National Sec- ns regarding the vote on the pro- Constitution. It appears, so the objections cited to the first have been satisfactorily taken the second proposal; we hope re that the new Constitution can 1 on as being adopted, in the of QST. In addition to the QST uurse, more detailed written re- | be mailed promptly to all Sec- department again urge upon the presidents and * all National Sections that in regularly each month some report for their respective sec- ng the Summer it was to be ex- t reports would fall off somewhat, the Fall approaching, there 1 a greater interest in amateur See to it that your country is rep- in this section of the magazine nth by sending in a short report Union Headquarters not later than fF each month. ation is particularly requested ign countries regarding the atti- heir governments toward the new wavebands. We want to know as ssible how much of these bands to be made available to you, what ill be allowed, intermediates ete. Please advise this office when such information becomes nown. tor of this ory ACTIVITY IN THE AZORES tter to the I.A.R.U. editor, Mr. M. Hon. Sec’y. of the Western Union Horta, Fayal, Azores, states: station, ep3MK, works on 45 } watts input to a Hartley oscilla- lub has just commenced work- there is much interest, and we made contact with nu2UN NV. We want to let all Nv sta- w that we are anxious to QSO iayVv BELGIUM According to a letter from Mr. Paul de Neck, President of the Reseau Belge (Bel- gian I.A.R.U. Section) there has not been so much activity for the beginning of the summer due to the influx of a great many new members, all young in the noble art of transmitting, and a period of motoring, football, etc., on the part of the old-timers. His report, which follows, shows an en- couraging amount of amateur work, how- ever: “eb4AU recently worked a Japanese un- licensed station on 20 meters, making the first EB-AJ contact. He also worked a Canadian ship anchored in Papeete harbor (Tahiti) and reports a QSO with VPG, a British station at Accra, on the Gold Coast of Africa. “eb4FT, on regular schedule, worked a French ship bound for the West African coast practically every night up to the ar- rival of the ship at Port Gentil, in the Gabon, its port of destination. “eb4AR is particularly interested in go- ing after ships, and works lots of them. “eb40OU, on 45 meters, puts out phone over the whole of Europe, with 100% read- ability, and recently received a report from Siberia commenting on the excellence of his phone quality. He is using a Belgian ham circuit, called the ‘circuit Van Gasse’, and with 45 watts input is one of the best phones in Europe. “eb4FT has just informed us that he worked a new official short-wave station skVPC, on 32 meters. The QRA: Port Stanley, Falkland Islands. Paul de Neck, President, Reseau Belge.” CHILE nu5APG, K. M. Ehret, at Oklahoma City, reports a recent QSO with that well-known Chilean station sc2AS, in which the latter stated that he was starting a new business further south and would definitely be off the air with the old set for at least two years, there being no electricity available at the new location. 2AS stated, however, (Continued on Page 62)

Page 51

1928 ul de (Bel- been f the many irt of ring, mers. 1 en- how- > un- r the ed a irbor G, a Yoast ed a ‘ican > ar- the go- hone ead- ‘rom rian sse’, best he tion Port qe. SEPTEMBER, 1928 Luis Greco Loprena, Calle Habana 7A, alta, Santiago de Cuba, Cuba (Heard during June) laba lacm lacu lacy lagd larb las lbbe Ibe liber lbbm lcb lcbg lich lemf licpi lgw i1mx Ino ldqai Irp ltr lvm lvw 2alb 2apy 2arb 2bea 2bek 2beg %gk 2beq 2brx 2bsr 2bxr 2cf Zev 2cxl 2dq 2kp Zila 2om 2pa 2pw 2rs 2tp 2ty 2ou 2xaf 2xc 2xs Saep Sanh Sarx 8cc Sccy Seg 3sh 3ts 3ut 4daep 4aq 4abi ick 4dq 4fe 4ha 4rr 4ud 4wo Saba 5acn Bbaep Saff tag Gaig Sain Sapi 5aq Sar Bary baw Sayl Bcf 5ea sen 5fi Sf] Sky Sle Slac 50a 5si 6am 6auk 6bgep G6byq Sbzs Gey Gdev Gdi G6Gdqb G6oiv Gwyk Tadx Tail Talp Tawn 7fc Saf Sap Sapn Savd Saxq S8azg Sbhn S8bho Sbhq Sbhr Sbvx Sbyw 8ccl 8eeq 8clq 8nx S8cug Sexe Sexd Sdig Sdno 8ei 9bal 9beq Ybo Ybq Ybsy YMbwj Sev 9cif 9cue Yex Yexe Yeys Sdce 9dkgE Yejw Yet Yevn {fs 9iv Spd ne-9dkg nj-2pa nq-2ac nq-2kp nq-4bn nq-5ex nq-5eq nq-5ry sa-Swb sc-2ab se-20m_ ue-3cs. H. J. Conti, 15 Harbor Terrace Drive, Rye, N. Y. ne-lad ne-lax ne-2bb ne-3aj ne-3ar ne-3ay ne-3bm ne-Bee ne-3in nce-8mv ne-9am ne-9cx velap velar velcc velco veldq ve2br ve3bo ve3br vedcb ne-S8ae ne-8rg nj-2pa nm-9a nm-xda nn-Inie nq-2cf nq-2iq nq-5by ng-bea nq-5fe nq-5fl nr-2ea ns-lfmh ea-gp ea-jh ea-ky eb-4fe ef-Tly ee-arc7? ef-Saxq ef-Sbtr ef-8cl ef-8er ef-8gdb ef-Sgyd ef-8It ef-Spns ef-8rrm ef-8vu ef-8wb eg-2un eg-5dh eg-5lw eg-6bb eg-6by eg-6dp ei-lce ei-ldo ei-lmg ei-lImm_ ek-4abg en-oj2 ep-lae ep-lef ep-3am ep-3¢b sb-lah sb-lat sb-lbg sb-Ica sb-lid sb-2bz sc-2ah se-lmi se-2ea se-2jm su-lcg fe-sur fe-suw fm-Sgke fq-pm oa-3jk od-afv oh-6ajl. 70V; Don Newman, RFD 12, Box 632, Seattle, Wash. (20 meters) lagr lap latr lav law Ilber lbyl Icki lom 2ayj dhe 2dk 2er 2nj 2av S3aqi 3ee 3gr 4daek 4am 4ck 4dt 4dv 4gg 4pd 5aek 5ahx 5akp 5aot 5ara 5Sast 5at 5auz jawp 5bbe 5Sbf BSbe Sbh Sbw 5em Sie 5kj 5ql 5qo brg Sta Buk 5xd 5yb 5za 5zas 5zav Taav Tabg Tacb Tact Taev Tafo Tafu Taij Tail Taka Takj Talz Tuq Sakv Savp Sawf Saxf Sazge S8be S8box Sbrh 8ecl S8cep Semx S8epe Sded Sdjv 8dma S8dne 8nb 8db Yacl Yaid Sajw 9ama Yany Yasx Yatq Yavo Yaxf 9bcx Ybez Ybjp Shay 9bxx 9byo Mbzy Ycet Ycje Yerd Yesr Ycuh YIevb Sewa Sdb Q9dex O9dfy 9der YIdhp Y9dih Ydjs Y9doq Sdrd 9dvr S9dvu Yeag Yecz Yefd Yefh Yeta Yeuh Yexs Seyl Sez 9fbw 9fci 9fdt 9fhy Yeab 9ety 9h] 9na Yay %sx 9wk na-7ady na-7aer na-7mn na-7nr ne-2ca ne- 4gg ne-4ha ne-5bn velaw ve2br ve8cs ve4gg nj-2pz eg-2ur eg-5by eg-5bma eg-5ml eg-5yq ef-8fe ef-8fd ef-8orm oa-2uk oa-2yi oa-3bd oa-3gr oa-3my oa-4bb 0a-71j oz-2ae oz-Saw oz-7mu oh-6alm oh-6avl oh-6clj oh-6dey oh-Gdud oh-Geat sb-law sc-2ab sc-2as wnp voq. E. J. Sahm, 265 E. 182nd St., New York City (20 meters) 6bjh Gbhy G6bzs 6eem 6ej G6esj G6ezk G6xe 6xu 6zz2d Tmx ee-ear91 ef-Sfd eg-5by eg-6by eg-6yv ek-4abn fe-les fe-egez oa-2ac oa-3bd oz-2bg. (40 meters) ek-4yt ep-len ne-2av ne-3ay nq-5cx nq-5fce nq-5fl sb-lah sb-lid. ity, wn tter 1eSs two ble rer, ei-ITU, Dante Bslaffi, Torino, Italy. lbgq 2ii 3sz 3eg nn-1na nq-5ex sb-lbg sb-las sb-1lbs sb-lar sb-lah sb-law sb-lea sb-2ad sb-7ab sc-2ar su-loa su-2ak oz-2ga oz-2am oz-2aq = oz-Baz oz-2bg oz-4am oz-2ae oz-3ar fm-Szk fm-S8jo fm-Sev fm-8gst fm-Shpg fq-pm fq-Ocya ft-nft. IBUX, D. H. Borden, Touisset, (20 meters) eb-dau ed-7zg xed-Oij ee-ear65 ee-ear70 ef-Sbf ef- Sbtr ef-8dmf ef-Seo ef-Sest ef-8fr ef-Ship ef-Shpu Mass. a wie _ ef-Sorm ef-8rrr ef-lm eg-2ay eg-2kf eg-2nh eg-2qv eg-2se eg-2vq eg-5ls eg-5ml eg-5uw eg-5vl eg-6bd eg-6dr eg-6hf eg-6hp eg-6ig eg-6mi eg-6oh eg-6rb eg-6ta eg-6vp eg-6wi eg-6wl eg-6wt eg-6xp eg-6byv ei-ldy ei-lgl ei-lgw ei-lpo ek-4abg ek-4ka en-Owr ep-laa ep-lbk fe-egez fk-4ms fm-tun2, fq-8hpg np- 4fagf np-4sa nq-2kp nay-laa_ sa-fc6 sb-lah sb-law sb-lib sb-2ab sb-2az sc-2ah sc-2ar sc-3ac sc-3cj su-lbx su-lex oa-2hm oa-2jk oa-2re oa-2rx oa-2ss oa-2yi oa-3bq oa-3my oa-3xo oa-4nw oa-5bj oa-Tcw oa-71j oz-2ac oz-2ae. (40 meters) ea-jh eb-4di eb-4fp eb-4ro ee-ear94 ef-8btr ef-S8zb ei-lgo ek-4uai ef-4uj ek-4yt em-smua ep-lae ep-lbl ep-lbx ep-lby ep-lcn ep-3am ep-3gb et-tpav fq-8hpg fq-ocya nj-2pa nm-9a nn-lInic nq-2ea nq-5ay nq-5by nq-5cx nq-5ea nq-5fl nq-pwal nr-2ags nr-2ea ns- 4mwn oa-2bv oa-2ij oa-2kb oa-2rb oa-2we oa-3bm oa- 3bq oa-3jk oa-3pj oa-3wh oa-3xo oa-4pn oa-5dx oa- 5he oa-5lf oa-5jh oa-5rj oa-5bws oa-7cew oa-7dx oa-7lj oa-Twt oz-2ga oa-3ar oz-3au oz-3az oz-4am_ sa-bx2 sa-ca2 sa-de3 sa-dl9 sa-dq4 sb-lah sb-lak sb-laq sb- lea sb-len sb-lid sb-2ad sb-2ah sb-2aj sb-2al sb-2bg sb-5ah sb-9af se-2ab sc-cnag se-lem se-lmi se-2ah se-2jm so-laa su-lfb su-loa su-2ak, Harold G. Fownes, 110 Riddiford St., Wellington, New Zealand. laal layj lanh lcdx lbub lcom laur lasr lbjp laoo lbat 1zl 1lnq lakz laww lum lbzi lajm lvh Ink lue leam lasu libkp lbvl lbyv Iry lajm 2bcb 2box 2kr 2alp 2bxg 2bbx 2ctq 2asb 2amd 2ie 2baz 2bir 2ate 2ahg 2agn 2at 2adl 2fc 2asz 2ass 2qu 2aol 2aha 2awa 2awx 2qu 2apa 2ahm 2ctf 3alq 3bbw 3bnu S8atp 3aed Sapx Sade 8ag 3wj Sajh 3cbx 3qp 3nf 3bnu 3S3aop Sais 8cfx 8ku 3akb 8aei 3a0c 3cfg 38bgs 3avm na-Tabz na-7mn na-7abe na-7aer na-7aam na-7to na-7hl ne-7ax ne-lak ne-lay ne-2ax ne-2bb nec-2bw ne-3es ne-3dy ne-3el ne-3hp ne-3ni ne-3qn ne-3md ne-4aj ne-4fv ne-4gb ne-4hm ne-4gt ne-4ac ne-5ad ne-5al ne-5cj ne-5co nm-laa nm-9a np-4aan np-3jg np-4kd np-4sa nh-ca nx-lxl ac-2cp ac-8to ac-8na ag-67ra aj-jxcx aq-l1lm lq-imdz op-lad oh-tdju oh-6ch oh-6dlr oh-6xk od-ipr sa-aa8 sa-da8 sa-de8 sb-law sb-2aw sb-3qa fm- tun2 fo-a8c fo-a3z eb-4ax eb-4yz ed-7dd ef-8ix ef-8ct ef-Szf eg-5by eg-5hs eg-5yx eg-6rg eg-6ut eg-2cx ej-7dd en-Ogg ep-lbx ep-lbk ew-h2 ew-ab. eg-5BZ, G. G. E. Bennett, 26 Blenheim Park Road, Croydon, Surrey, England (During May—On 20 Meters) labd ladm ladw laff lakm laqd laqt lasf latr lIber lbed lbig lbil lbux lbvl lbxe lcab Icjh lcemz Ide 1fn lkh Imx Isi lue luo lvw lixaw 2ag 2agp 2ain 2arb 2awq 2azl 2bbx 2bew 2bdr 2bfq 2bfy 2bjm 2bmk 2bms 2bot 2bxr 2cdm 2ch 2ck 2ctq 2ff 2ih 2sb 2sj 2vk 2xad 2xg Saal S3aih 3ann 3anv 3aqj 3bee 3bwj 3chk 3db 8dge 8di 3dr 3wm 3zf 4daay 4acc, 4adb faek 4afe 4dagr 4ck 4db 4dv 4io 411 4nl 4ow 4pd 4pl ikn 4ry 4to 4wm bacl Bbadn Bae Bbafk 5aq Sara batj 5Sauz 5avs Bbayb bazu BSbbe Sbj bdq 5dv Sef She Ske 5mq 5ns 500 5re Swz bzav 6agr 6ahs 6ajm 6alw 6ard 6azs 6egv G6Gbjd 6bjh 6bkd 6bhoa 6bq G6bux G6bzf 6cedw 6ceez@m 6chq 6col 6cyx 6ceze 6ezz 6dbo 6ddy 6dep 6dev 6dfs 6dhq 6djk 6dlw 6dom 6don 6dor 6drb 6dri 6ec 6ih 6i¢ 6jn 6kb 6pw G6uf 6uz Gwhb G6xi 6xu 6zzd Taav Tacs Tacy Taff Tafo Taij Takj Tako Tek 7fe 7fh 7kt Tilt 7md Tmv 7Tmx Tnr Tov Tsf Ttj Tvq Sabh Sacm Sade Sanv Savp 8bbl 8bdp Sben Sbev S8bg 8bkq 8byn Seae See] Secw Sclt Semb Scnh Sepd S8ewie Sdce 8dfw Sdjv Sdqk 8gz 8jj 8kq Snb 9abu Vaid Yajw Yake Yalz (Continued on Page 72)

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Correspondence The Publishers of QST assume no responsibility for statements made herein by correspondents. For Next Year 136 High St., Exeter, N. H. IST: to be done about it? Must the - OST be changed after January Ist to be noted that “QST” is not the list of “Q” signals adopted Washington Convention and ap- “CQ” is to take its place (Article ir. 3). Won’t the CQ hounds laugh 1agazine must be called “CQ”. sly, though, I hope that an article be forthcoming dealing with the operating procedure which must accordance with the Convention. i S been said about the new wave- very little about the other vhich amateur operation will be Of course most of the regula- to commercial work, but it would for the sake of uniformity, the hould conform to them as far as the set ol nple, I don’t Suppose that are bound to use the new signals (“R” signals), running 5, but it seems to me that they especially as I think that the re better than the present to 9, st of “Q” signals certainly looks t ones from the old one. It will take o get used to QRZ meaning “You r called by—”; QRV “Send a series QSR “The distress call received been attended to by—”; etc. It note, among the numerous us abbreviations which have been , that “OK” is officially ri ining, “We are in agreement. ly the owners of amateur phones little occasion to send out SOS’s. perhaps some of them ought t« they may wonder why the official e distress call is “Mayday,” until lers that this stands for the m’aider”’. gr to Cog 0 ” 4 ood ndering if the amateurs will adopt Yes and “N” for No, or if such ex as “Yep” will continue to hold Do you think there would be any in trying to establish a set of ns especially suited to amateur as the commercials have their Is? These might be special “Q’s”’, OST SEPTEMBER, 192 although there would be a disadvantage | mixing the official with the unofficial. Wj already have “73,” so how about extendi this plan? Thus, for example “71”, mig mean “Please send card” ete ad infinity A rather lengthly list might serve emergencies, as for instance, when open tors do not speak each other’s language, } I am not enough of a DX man to spe with authority on such matters. I am glad to see that national prefixe rather than intermediates, are to be w hereafter. I have never cared for the ij termediate plan and I guess we have all hy the experience of listening to a long strin only to find that the all-importa intermediate was given carelessly or wa lost in QRM or QSS. The prefixes ought go far iki t identifies “alle OL Calis, towards making station tion easier. amateur stations fall hat they are municating with I; to w hat They are “fixed” ; . nently located and co. ~ perma or more stations similarly located,” but most ways their operation (except wh working on schedule) ms to be more the nature of that of mobile stations, % referred to in the Convention. Probably th matter of no importance, however, le in QST on sot ed would be of intere is a I am sure that an arti of the points mentior to many of us. H. 5: 1 r r referred to the Editorial pages Sha . 1R) of t The “Splatter System” I Dr. H Taylor and Hub mn or im sibili ‘ } War rr» » Editor. ] Editor, OST: In OST I rea i ion of the “Warne use of the 3 This systes July 1928, page 7, Splatter System” for the waves based on Meissner’s 80-degree angle lo distance experiment, ntemplates directil these waves more or less vertically upwa with the idea that they be splashed do from the skyward regions. From the & scriptions which I have read about the ové head regions I wonder whether the wit

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Type BNA forreplac- ing the acid jars in Balkite Types N and K Trickle chargers ”, mig nfinit — ¥ u é . ; lypeBJ for replac- serve \ . . 7 ing the acid jars n oper in Balkite Type J saat chargers AALe, 0 to Spea prefixe be us the in ; Type V-4 for re- all hy placing the rec- tifiers in 6makes of Trickle charg- ers Type M-16 for replac- ing the rectifiers in . 11 makes of “A” Eliminators and 3 Ampere chargers ibly th Vox. on som intere , IR Type EBH for re- placing the BH type Tubes in “B” Eliminators Every Elkon Ree- tifier goes through these exacting tests. Identifies You and Helps QS T Say You Saw

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Get into the \ COMMERCIAL RADIO FIELD where the MONEY ; Is We've | hundreds tell us that they knew radio backwards and forwards. Yet th lled in our courses. And a few weeks ey started to learn radio the RIGHT hese same men told us that they n lized how much they had been missing long Mayb ve sufficient radio knowledge to build a circuits. That isn’t enough to make a ercial success. What you really need is t takes you from the first elements of rad zh the most complex stages and gives } tical knowledge you need for com- mercial ADIO INSTITUTE SPONSORED BY RCA, G-E ‘ WESTINGHOUSE The R f America is the world’s oldest radio s z the finest and most comprehen- sive inst tainable. Our graduates are mak- ing rea send you copies of some of the letters ¢t bout their successes. UDY AT HOME Another 1is course is that you can study at hon please and as long as you please. No need p your present employment. No time lost k and forth to classes. Our new booklet others —just like yourself success in radio, and ho 1 make this pro- ee fession ting brain-work RADIO mstrrure) career. You Rica | yourself to , OF = his book through qr will clip and f ff e coupon, we'll | ff j book to you. j x | rw}, RADIO [- rE OF AMERICA Dept. D-9 326 Br vw York City P your booklet. Name ; MITT TIT TTT Tt Addre ss You Saw It In QS T—It Identifies You and Helps QST less waves will act as the system has sug- gested. To have any considerable splash- ing, or scattering, of the wave would re- quire electron coagulations of rather high density—ten million or so per cubic centi- meter (or a million, million ions)—whereas the usual electronic densities are probably a hundred times less. It is difficult to see any way in which such coagulations could occur under normal conditions, although they might possibly exist under unusual circumstances, as during wind storms in the high atmosphere, aurora displays, et cetera. On the whole, one cannot be quite certain yet of the meaning of Messner’s experiment. There is, however, a scattering of the 10-meter waves which unquestionably does exist—a scattering from the waves of the sea. Sea water has a very high refractive index for these waves (twice as high as the index of a diamond for light) and consequently is a very perfect reflector. It is like molten silver for light waves. If an observer had an eye sensitive to 10 meter waves and were situated aloft over a patch of the sea on which were falling a sheaf of the waves, he would see the water waves and ripples shimmering and scintillating very brilliantly in all directions with the 10-meter illumination. The same thing, but prehaps to a lesser extent, would be expected to be true of the facets and inequalities of the land. This type of scattering may be of importance in the 10-meter communica- tion channels, such as filling in the skip zones, indicating storms at sea and the like. E. O. Hulburt. Danger [The following letter from S. C. M. Sears, to an amateur in Los Angeles, is published to bring this subject to the attention of the membership, so that all members may be warned against accepting such offers. The Los Angeles amateur stated that there would be “something in it for the stations doing this work.” Amateurs cannot accept compensation for their services in handling messages. See the article by Mr. Segal on page 13 of July QST.—Editor.] LaJolla, Calif., May 27, 1928. Dear OM: I am in receipt of your letter of the 25th with reference to lining up some San Diego amateur station to handle orders between ere Company, where you are employed, and the ............ Company of San Diego. I am sorry, indeed, that I cannot do as you request. To handle such business, the stations involved would have to operate under a limited commercial license; such work not being permitted under an amateur license. Recently some of our stations have have had to decline similar messages from other sources, as they do not care to jeopardize their licenses, \\\ 1 Same

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ACEW (: onsole Model A.C. TUBE Strom berg-Carlson Here is the wonderful Receiver you have dreamed of owning—a Receiver with the celebrated Stromberg-Carlson tone, at a price within the reach of everyone. Not only the tone but its extreme sensitivity—its keen selectivity —its splendid work- manship tell you at once it is a Strom berg-Carl son. This Receiver has a handy graph into a high quality electrical reproducing instrument. c eStromberg-(arlson Sextette (friday jack to facilitate playing records hecialuiiie through the wonderful audio system of the Receiver; thus making it pos- sible to convert any standard phono- modern STROMBERG-CARLSON TELEPHONI venings Fadi n o'clock Eastern Day! through the NBC and 22 v Stromber¢- Carlson MAKERS OF VOICE TRANSMISSION AND VOICE RECEPTION APPARATUS FOR MORE THAN 30 YEARS No. 636 Stroml one UX-171 Output Tube, and one UX-280 RCA Tubes. A sy less Tubes and Speaker, $245. Slightly higher Rockies and West and Canada. rg-Carl son Uses 5 UY-227 A.C., The beautiful cabinet sets a new standard in radio. It is low, artisti- cally designed, with two-toned Walnut panels re top of matched Walnut A slide which may be used as a writing table acts as a cover to close the front. butts. Mra. Co., Rochester, NEw York light Time 1 Stations Say You Saw It In Q S T — It Identifies You and Helps Q S T

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Push-pull Transformers with + impedances to match power tubes and dynamic speakers. ... ELE(¢ BX” Input Transformer xtremely high primary in- d 1ce. Secondary accurately di Price each, $6.50 ‘GX-210” Output Trans- former. Especially designed for push-pullamplifier using UX-210 or CX-310 tubes. Secondary con- ne lirectly tomoving coil of dy- speaker. Price each, $6.50 “HX-171" Output Trans- Same as above except impedance matches UX-171, Cc» l, or UX-250, CX-350 tu Price each, $6.50 SANGAMO CTRIC COMPANY SPRIT? FIELD, ILLINOIS ular giving audio hook-up iplete information on request. You Saw It In QST Say I trust that you will understand my rea- sons for taking this stand, and hope that you will be able to effect some other arrange- ment that will prove satisfactory. The Boulevard Express Company maintain sta- tions in Los Angeles and San Diego and might be in a position to help you out o this. Yours very truly, Section Communications Members A.R.R.L. G. A. Sears, Chisholm eg2CX. Why YL’S Become Amateurs “Round Hills,” So. Dartmouth, Mass. Editor, QST: | have been wondering if you and the other “hams” wouldn’t be interested in hear- ing from a YL operator—since they seem to be rather scarce—and perhaps hearing how a YL became a “ham”. My husband, being the Radio Engineer for “The Round Hills Radio Corporation,” had a transmitter and seemed to have such a lot of fun staying up all night operating it, that I began to think that I was missing a lot. So that—and the fact that I was afraid of becoming a “radio widow” caused me to learn the code and become the YL operator at Station 1BHS. I am not saying much about how the amateurs, whom I QSO’ed, had to suffe when I started (and I’m not so good yet) but I will say they were all perfectly great about sending slowly and repeating possibly a dozen times, and I would like to take this opportunity to thank them. I wish some more YL’s would get the “bug”. I have attended two conventions; one in Boston and one in New York and only met two other YL operators. In Boston I was rather backward, but in New York I entered the contests with the rest and came back to Round Hills with four tubes and an aluminum shield. Helen Davis, YL at 1BHS. In Appreciation Aboard S.S. Astoria, in port, Seattle, Washington. Editor, QST: Having just finished reading the ex- cellent article by Mr. Boyden Sparkes in the Saturday Evening Post for July 21st, en- titled “Some Attic Adventures,” in which Mr. Sparkes has so ably caught the spirit of amateur radio and placed it before the public, it comes to me that we could show our appreciation of this in some way, such as by letters or station cards. The writer can recall no comprehensive article on this subject ever having been printed in the more popular non-radio magazines, and it seems that Mr. Sparkes is due a sincere vote of thanks from each of us. Many of our difficulties can be traced tu lack of informa- ~It Identifies You and Helps QST

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rea- that nge- The Sta- and 0 ve CARDWELL CONDENSERS L ~a Ar” ver With Commander Byrd in 1926 9 Emto the Antarctic in 1928®@ —=, » —— — — — : —. — _ 2 —_— — — — a —\ > N ONTHS, sometimes years, are spent in preparing for Polar | I Expeditions. Every item of equipment from ship to footgear is considered, tested, viewed from every conceivable angle before being accepted as worthy to share responsibility for the safety of an expedition and its participants. No factor that human in- genuity can devise, making for success and security, is overlooked. DEPENDABILITY in materials and equipment is of paramount importance in these, as in other ventures, where man is dependent upon things of his creation for his very life. VAST and silentspaces, the Polar Regions. Vast, but to the listening ear not silent when vibrant with the all pervading voice of Radio. BYRD, DYOTT, MACMILLAN, STOLL-McCRACKEN, are some of the names identified with expeditions placing their confidence in CARDWELL CONDENSERS for the equipment needed to . keep them in touch with civilization, and possible succor when in desperate need of it. ~ ~ ~ ~ WHO will say that the equipment selected for ventures like these is not DELIBERATELY and WISELY CHOSEN? —, —— — -—_ —w — =( , , = — 4 4." — — \ sy a. ’ — = 4 é ae =v at WS “p= Literature upon request The Allen D. Cardwell Manufacturing Corp. $1 Prospect Street. Brooklyn, Mi Be “The Standard of Comparison” Say You Saw It In Q ST It Identifies You and Helps Q S T

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No Grid Leak Interference with the Bradleyunit-B Resistor RB )LEYUNIT-B solid-molded , istors eliminate the noise aI mterference in radio circuits caused byinferiorgrid leaks. Oscillo- graph tests show the Bradleyunit-B to be remarkably quiet in operation. Bradleyunit-B Fixed Resistor is made of a special, uniform. mix- tur ked and solid-molded at high re. This creates a solid, uni- form unit, providing a constant re nce regardless of voltage used. R manufacturers are assured of al irately calibrated resistor wl will retain its initial rating in I itely. For Radio Manufacturers narkable solid-molded resistors tically unaffected by moisture, alt t depending on a glass enclosure for tection. yunit-B is furnished with or W t tinned leads for soldering. Made - from 500 ohms to 10 megohms. I Bradleyunit Resistors are also furt 1 to meet your specifications. dley Co., 277 Greenfield Ave. Milwaukee, Wis. —— Resistors | ) Say You Saw It In QS T—It Identifies You and Helps QsT tion on the part of the public, and truthful publicity of this kind will certainly go a long way toward establishing a better un- =. of the radio amateurs of the world. —Emry C. Stuedle, 6NW, KGEP, 5503 South Cimarron, Los Angeles, Calif. e %? es” and “c&” 4338 W. Fort St., Detroit, Michigan. Editor, QST: Many of the fellows, in their correspon- dence and on QSL cards, write the abbre- viated “and,” “es” instead of “&”. No doubt this is due to the general run of amateurs being unaware that “. . . .” is the character for “&” in the American Morse code. —J. O. Ellison, 83COW-8AGR. “Propaganda Cards” 66 Ingram Road, Thornton Heath, Surrey, England. Editor, QST: Probably many American hams have by now received a card from a British station which bears at the head an inscription which ye only be read as a direct insult to the R, S. G. B. pt il so far as we have van able to find out, the operator’s only objection to the R. S. G. B. is that it does not give the same value for the money as the A. R. R. L., he does not join up and lend a hand with im- proving things, but tries his hardest to dis- courage other intending members from join- ing. QST readers will realize that the T, & R. Bulletin, with its minute circulation as com- pared with QST, is neither so large nor so prolific in advertisements, but that it will grow if the R. S. G, B. is given support by the British hams, and not if they all cry off and do nothing whatever to support it. Luckily there are not many such “hams” in Great Britain, but the existence of one or two is enough to cause anxiety to those who are looking forward to a British version of the A. R. R. L. as the ultimate outcome of the R. S. G. B., with a proportionate large membership. We hope that stations seeing these propa- ganda cards will not treat them seriously, and will realize that they only express the sentiments of a very few unfortunates who have lost interest because they have been content to watch the work of others instead of doing their own bit. —L. H. Thomas, eg6QB, D. W. Height- man, eg6DH, H. D. Price, eg6HP, H. Chisholm egBCX. Members A.R.R.L.

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5503 t St., ran. $pon- bbre- No n of - oe [orse 1GR. > by ition hich the e to the ame , he im- dis- oin- om- r so will by off ns’ one ose ion » of rge pa- sly, the rho en ad ht- Remarkable Federal Feats A Federal F xr at Buffalo, N.Y., has a record of verified re- ception from JOAK- Tokyo, Japan, 2LO London, England, CWX-Havana, Cuba, and practically every distant station in this country. America’s Most Sensational edera ORTHO-SONIC* Licensed under patents owned and or controlled by Radio Corpora- tien of America, and in Canada by Canadian Radio Patents, Lid. Say You Saw It In Q S T — It Identifies You and Helps Q S T 59 D. X. Receiver N planning the F 11, Federal had but one goal to produce, regardless of cost, the most sensationally performing radio re- ceiver that skilled engineers could devise. Delicate hair-line tuning, together with an almost unbelievable distance range, attests to their success. Antenna and ground operation with four stages of tuned radio frequency coupled with detector, and two stages of amplification will bring in even the weakest of radio impulses picked up by the an- tenna. Each unit of the set including the individual tubes, is com- pletely shielded. The chassis is of sturdy all-metal construction — the cabinet of genuine mahogany. This set may be had either for battery or for light socket opera- tion with Federal’s power-tube coupler which greatly enhances tonal quality and the efficiency of the set. Prices, without tubes, for battery operation, $250; for light socket oper. sora, 60 cycle, $360; 25 cycle, $380. (Slightly higher west of Rockie Ss. The designated Federal retailer in your community will . - s , , ; gladly demonstrate this phenomenal receiver, or you may write direct for complete specifications FEDERAL RADIO CORPORATION, BUFFALO, N.Y. OPERATING BROADCAST STATION WGR AT BUFFALO Federal Ortho-sonic Radio, Ltd., Bridgeburg, Ont. Radio Federals fundamental exclusive developmen: sonic reproduction is patented under U.S, iomerel Pei oe te Ne. 1, panty ane

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Radio Broadcast announces a Series of Articles by Mr. Robert S. Kruse R BROADCAST wishes to al that Mr. Robert S. Kruse, f Technical Editor of QST, W regular contributor to R ideast. MR SE’S first article entitled “Wy it the 5-Meter Band?” the Augustissue. His entitled “Practical W >-Meters”’ will appear in ber issue. Other articles Ol ave experiments, experi- el apparatus, written by Mr will appear in future Sé 1cie RE (S OF QST can follow Mr. K xperimental findings in t ave field by reading R adeast each month. Send on NOW for the next four lio Broadcast contain- by Mr. Kruse. This ~~ AL ofl vou the magazine at 25c pe stead of 35c. Ra vadcast, Garden City, N. Y. next four issues of Radio rticles by Mr. Kruse 60 Say You Saw It In QST Award of Honor Anvik, Alaska, May 14, 1928 Mr. Kenneth B. Warner: It has been noted here, in Alaska, that while many bouquets were handed you aft er the Conference in Washington, and a few bricks were thrown, none of those sub stantial rewards were tendered you which are ordinarily so gratifying to the re cipient and which testify to posterity of the gratitude of his contemporaries. It is, therefore, with great pleasure that I hav to inform you, that the Bunkodyne, which you will find enclosed, has been awarded to you. The Bunkodyne, as you are _ probably aware, is to the A.R.R.L. amateur what th: Carnegie Peace Prize is to the prize fighter and the Pulitzer Medal is to the pacifist the ne plus ultra of recognition. The latest award was made to Mr. Everett Lasher, of TADY, Latouche, Alaska, who makes a specialty of routing his “nu” correspondence via England. Mr. Lasher has constructed his transmitter in such a way that it can be used as a long distance pulmotor. He recently revived a 4 who lost consciousness during a CQ endur ance test, Mr. Lasher’s want of judgment was overlooked in view of the humanitarian impulse which led him to do what would otherwise have been reprehensible. At the time that the award was made, I made the mistake of informing him that it was the 347th award that had been made during the present year. On looking up the rec- ord, I find that in point of fact, it was the second award that has been made since the foundation, in 1923. The first award was made to Mr. Charles A. Service, Jr., for be- ing good looking. No other names were considered at the time. Your name, there- fore, in point of time is the third on the list; but in point of honor, as one who loves his fellow ham, it leads all the rest. Please accept my congratulations. The Bunkodyne, as you probably know, is a perfect substitute for the rubber bands and shawl straps which are principally re sponsible for the decline in morals which is characteristic of the present generation. It consists, essentially, of a grid, an induct ance and a condenser. The condenser, which is the tightening or binding element, is in the form of a loop which is passed throug! It Identifies You and Helps QS T

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- a. a oo \ ska, 28 " Radio Operators! 2 ub . uo Are you prepared to use the new International “Q” } : ; - - signals which go into effect January 1, 1929? Do you = know the correct procedure for obtaining a radio com- my pass bearing as prescribed by the terms of the Interna- Be tional Radio Telegraphic Convention, effective January ; oe 1, 1929?—-the right procedure when distress communi- rm cations are ended and silence is no longer necessary ?— . what to do when you hear from a radiotelephone station the spoken expression Mayday? bly th These Questions and Thousands More ter st Are Answered In {r. -_ rs he ne [r. 7 A Compblete Handbook of Principles, Methods, Apparatus for Students, Amateur and Comercial Operators, Inspectors By G. E. STERLING, Radio Inspector and Examining Officer, Radio Division, U.S. Dept. of Commerce. - Edited by ROBERT S. KRUSE, for five years Technical Editor of QST. 7 ‘ , . . saa ~ ‘ rn Complete Preparation for Government License. 16 Chapters Covering 6 Element I t t nd A. a Broadcasting Equip- including, for first time in ) Marnetisr ment including, for the first any text book description and it VI and Ger time in any text book, the circuit diagram of Western Stora Batter and Char complete equipment of West- Electric Superheterodyne Re- n i Cireuits ern Electri 5 Kilowatt ceiver Type 6004C d > a y a Ap) atic i broadcasting Transmitter 13. Marine and Aircraft Radio the Va im Tub ed in over 75 of Ameri- Beacons and Direction Find- I lamental Cit t Em can broadcasting stations. ers. pl d it \ r rul l Ar rransmitters inecludin 14 The Development of Amateur e I mitter lescription of Federal Marir Short Wave Apparatus. Com- Or 6. Mod tir Systen Em- 2 Ki'owatt Are Transmitt plete details of construction, 3 ! d in Radio Broade: t [ype AM 4151; also model operation and licenses. ‘i 7 OW meter Piezo-I tt ‘K” and “Q” 15. Radio Laws and Regulations ( llat Wave Tr: and 1 Spark Transmitter includ of the U. S. and Interna- ' ‘ Stre } Measur ng cescription of Navy tional Radio Telegraph Con- \ it Standard 2 Kilowatt Tra vention. Quotations of all ; M ! Vac be 'T mitter important sections 5 mitter lud ! Commercial Radio Re ver 16. Handling and Abstracting ; description of Model E17 t nd Associated Apparat Traffic : a e Order On This Coupon a ~ It F yf ‘ccc FF ees eee eee eS ee rxamMine a ree - D. VAN NOSTRAND CO., INC., 8 Warren St., N. Y. 8 4 Send me as soon as published THE RADIO MANUAL § rt = es Ria af examinatior Within ten days after receipt I pecial I TICe IN OW 8 ll either return the volume or send you $4.95.—The : . 8 special advance price 1 The R » Manual now on the press and will & ' ‘Teady hortly Over 900 pase bound in flexib § Name +s § brikoid Regular } publication will 1 i (QST 9-28) g ww. QO rs received now will be ac« da t §St. ar Nur esceatbiee 1 lal a nee price of $4.95 Send no money now a 7 amir e book first. Pay or return in ten day a Cit I OR 6 i.e 56 N0600 0% 6K904810506000NR ER ORES t Phin = : i \ —— Say You Saw It In Q S T — It Identifies You and Helps Q S T

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Don’t Start the Season Blindly— time here! That means over last season's equipment very part of the set to make certain | of proper performance. Par- should check the calibration of your Much can happen to them unless ntifically designed and constructed ning. is ing will need to make some replace- igest that you give serious con- the instruments you select. Radio ry widely in their design charac- their ability to withstand the and surges incident to the op- ‘ WESTON ae MULLIAMAGe. STATI 2d, 409 “2 * “ » Weston Thermo Milliammeters ve call your attention to the fol- ristics of Weston ‘Thermo Milli- Model 425: finite assurance of your output, readings after hours of con- er-loads will not burn out these eal for short wave transmission, very low inte rn il ‘lectr static this reason it the true in the circuit, and does constants of your transmitter. vives irrent ammeters having a safe radiation amperes, Iso made as 1 to 20 I te the new radio circular ‘‘J’’ just off rON ELECTRICAL INSTRUMENT CORPORATION relinghuysen Ave., Newark, N. J. WESTON RADIO INSTRUMENTS ht) 43) 62 Say You Saw It In QST —It Identifies You and Helps QST one of the two holes which form the gri the other being reserved to receive the coy denser in the event of the first hole beiy worn out. The grid is located in the midd of the inductance. The inductance and grj may be purchased from any mail order ho orany dealer in second hand buttonholes, condenser consists of a string of any desj able length, having a resistance one ine more or less, from each end. The ends be yond the resistance are the filaments. Oy of these, F, is longer than the other, f. operation, the letters, papers, millioy dollar bills, ete. which it is desired to keg together having been placed in the loop ¢ the condenser, the filament F is_ pulled steadily and firmly until the desired degre of compression has been attained. It wil be found that it will release this compres. sion, if it is desired to extract one or mor of the papers or the bills. A gentle pull will effect this. The Bunkodyne is a patented device, The award carries with it the privilege of manv- facture and sale; subject, of course, ‘| prosecution by the holders of the patent rights. It is not known who they are; but it can, doubtless, be found out by experi- ment. In making the Bunkodyne award, it is customary to send with it case remittance of $342,671.00, or as much of this amount as may be available from the interest ac- cumulations on the original foundation in- vestment of $00.29; but in this instance, out of a delicate regard for your feelings, this feature is omitted. Trusting that you will find great enjoy- ment in the use of the Bunkodyne and in the exercise of the privileges which accon- pany the award, I am sincerely yours, rep John W. Chapman, na7TE.F rig P. S. Having discharged the responsible— son duties which have devolved upon me, I want bee to say that it would be a good thing forf jg, your critics to ponder upon what would ~ have happened to us if you had not taken part in the conference at Washington. 7 is | 8,0 vic I. A. R. U. News tio (Continued from Page 50) ont that he would try to set up a transmitter— au with a 201A tube and a dry-cell plate ' supply. We are sorry to see the old 2AS go off gis the air, but hope that some satisfactory} f5, QSO’s are established with the baby set in uf: the new location. Let us hear from you by mail, at least, OM. , CHINA Father E. Gherzi, S.J., in charge of the Fae weather and seismic services at the Meteorological Observatory at Zi-ka-wel. near Shanghai, and already familiar to QST readers from his article on fading in the June issue, writes as follows:

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le grid he cop e bein midd nd y r hou es, Th ’ desig e in nds de . On f. nillion Oo kee loop of pulled degre: Power Supply Transformers It wil These transformers supply full mpres wave rectifiers using two UX-281 * more tubes, for power amplifiers using le pull either 210 or 250 types power ampli- iving tubes as follows: T-2098 for two 210 power tubes, $20.00; T-2900 for e. The single 250 power tube, $20.00; T-2950 manu- for two 250 tubes, $29.50 se, | patent Double Choke Units ms but Consist of two 30 henry chokes in one x per'- case. T-2099 for use with power sup- ply transformer T-2098, $14; T-3099 it is for use with transformer T-2900, $16; ttance T-3100 for use with transformer mount T-2950, $18. st ac- : Power Compacts yn in P e, out A R- 30 MER A very efficient and compact form of this UDIO TRANSFOR power supply unit. Power transform- , er and filter chokes all in one case. Type R-171 for Raytheon rectifier and ad te UPREME in musical performance, the 171 type power tube, $15.00; Type nd m — i. : R-210 for UX-281 rectifier and 210 ccom- new Thordarson R-300 Audio Trans power tube, $20.00; Type R-280 for former brings a greater realism to radio UX-280 rectifier and 171 power tube, reproduction. Introducing a new core mate- ae ‘7TE.F vial, “DX-Metal” (a product of the Thordar- Speaker Coupling Trans- 1siblef son Laboratory), the amplification range has formers — been extended still further into the lower reg- y ior rould , ° ° vaken De reproduced with amazing fidelity. 4 complete line of transformers to : couple either single or push-pull 171, ister, so that even the deepest tones now may 210 or 250 power tubes into either high impedance or dynamic speakers Prices from $6.00 to $12.00. The amplification curve of this transformer . : . : Screen Grid Audio Couple: is practically a straight line from 30 cycles to : : oo The Thordarson Z-Coupler T-2909 is 8,000 cycles. A high frequency cut-off is pro- a special impedance unit designed to vided at 8,000 cycles to confine the amplifica- couple a screen grid tube in the audio ° ° a amplifier into a power tube. Produces tion to useful frequencies only, and to elimi- excellent base note reproduction and nate undesirable scratch that may reach the amplification vastly in excess of ordi- . ° nary systems. Price, $12.00. audio transformer. plate : 4 When you hear the R-300 you will appre- THORDARSON ELECTRIC MFG. CO. y } ) off } ciate the popularity of Thordarson trans- 500 W. Huron St., Chicago, Iil. =e on formers among the leading receiving set man- Gentlemen: Please send me your constructional ‘you | Ufacturers. The R-300 retails for $8.00. annem. ~~ndieer iat te a interested in amplifiers using........................tubes. URDARSON ELECT TRIC M. MANUFACT URING CO. _— ; enamine: ‘Transformer Spec: URLD OLDEST AND LARGEST EX CLUSIVE 11 TRANSFORMER MAKERS Street and No. uron and Kingsbury Masts — Chicago, lil. USA. . pan Say You Saw It In Q S T — It Identifies You and Helps Q S T

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You can depend on their performance ecause Cunningham Radio Tubes are guar- inteed against electri- mechanical defects in construction. ook Jor the Name Cunningham on the [. Cunningham, Inc. San Francisco “I think amateurs everywhere might interested in knowing that I am sending every day at 0145, 0945, and 1215 GCT, oy 23 meters, a weather bulletin giving meter ological observations from many stations in the Far East. As this sending is a] ways done with the same power—220 wattg at a very exact hour, I would be indeed grateful to all hams who could try to listey in. The transmissions last about }§ minutes. “IT am sure that various official weathae bureaus, for instance, along the Pacifi: Coast, would be glad to get these observ. tions, and it would be another feather i; the cap of the amateur if through this channel a scientific link could be establishe# between the observatories on each side of the Pacific Ocean. “The station is always operated by my. self, QRH 23 meters, under the call ac8ZW,; The note is fairly distinctive, beinz £0 cycles.” ENGLAND May: “Most work during May has bez done on 23 meters but conditions do not seem to have been as good as usual; at any rate in the latter half of the month. 45ML‘% est QSO’s were with the sixth and seventh US districts and the third, fourth and Canadian and with OA, SC, SB, AI fk2MS. Lately he has been listening ten meters without hearing much so 2XV had consistent contact with the si and seventh with 75 watts until the middle of the month, when he too found conditions fall off. OA and 6Z were also worked on 23, and a number of these boys seem to have left their old yet 30 meters for the lower band. Some interesting QSO’s were had with nulII and 2XV is looking forward te meeting him in person soon. “SYK worked fk2MS and the usual sixes and sevens on 23; he has been trying phone on this wave. too. and also did some wor® with negative results on the 10-meter band 5YX, who like 5YK is crystal controlled worked two NU sevens and some fives on 22 meters during March and would like t know if any six heard him as he could.ns raise one. 5BQ is getting out FB on 3 and wants schedules with the Nu fourth and nc. What offers, gang? “9CB and 2CX are working South Amer ica on 23, but 2CB cannot seem to get d cent contact with the States. He is one 0 the ‘mangle brigade’ using a hand gener tor for power supply. 6QB has_ worked heaps of sixth and seventh district stations getting RG from both on 23 meters with low power. He also hooked OA and nc4FB 2NH ran a schedule with oz4AM for 3d days without a break! He is also investr gating ten meters. 6BB works AS and 8 on 45 meters as well as the U.S.A. 6PA has worked all over the States on 23 with a power unit of five watts. Good work OM. “6HP works 0A on 23 but has difficult? with South America iCL has had some ’ f 1

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Unless You Are | Checking Out Jan. I... YOU WILL REQUIRE A FREQUENCY METER TO OPERATE WITHIN THE LAW! ¢¢ PRECISION work requires precision measuring equipment,” says H. P. Maxim, Pres. A.R.R.L. Old wavemeters will soon be useless. You can’t operate with the new 7000-7300 Kc. band jammed into 5 or 10 divisions on the dial. Try to pick out 7275 Ke. on the dial of your present wavemeter. It can’t be done! Kilocycles will supercede meters. QRH will be specified in frequency. REL, anticipating the need of thousands of Amateurs, is pro- ducing the new frequency meters show n on this page, designed expressly for the new bands. Years of scientific re- search and en- gineering skill have made these Illustrating the 3500 to 4000 K.C. frequency meters superla- meter. Separate fre- quency meters are des- tive p i eces of igned for each band. equipment, typi- calREL products. WRITE : rhi Illustrating for literature which how: ‘the 7000 » dis- to 7300 K.C. completely dis frequency oes y _ meter is coup- cribes the new met- —_ meter iscoup- > i : ternel fre- ers and outlines the eae new operating re- indicator. quirements. RADIO ENGINEERING LABORATORIES 100 Wilbur Avenue Long Island City, New York Say You Saw It In Q S 1 — It Identifies You and Helps Q S T

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manship. W.E. 211 W.E. 212 U. V. 293 U. V: 203A U. V. 204A U. V. 204 10% Discount on lot of 6 tubes, We List and Price Repairs - = $16.50 40.00 15.00 19.00 75.00 50.00 from above list) Our work guaranteed against defects of material and work- ( UT down your operating cost—our rebuilt tubes ac- complish this—their life is equal to new tubes and their perform- ance will satisfy—send in your Burnt Out Tubes Now These tubes are rebuilt using same type filament as they had originally; also the operating characteristics are maintained the same. We purchase burnt out tubes of the above types. SOLVE your rectifier troubles | once and for all. | RECTOBULBS 3000 Volts and 250 Mils. $15 ea. Type 203 50 Watt Tube $20 ea. No charge for crating if cash accompanies order. National Radio Tube Co. 3420 18th St., San Francisco, Calif. (A Ham Institution) — NATIONAL TUBE REPAIRS Say You Saw It In QS T— It Identifies You and Helps QST interesting NU contacts early in the month but like everyone else is finding things dud just now. 5HS is very QRW but will be QRV again soon. “The Third Annual Convention of the R.S.G.B. is to take place on the 28th and 29th of September, and any American hams over here on these dates will be welcomed, Further details as to programme are not yet available, but it is sure to be wonderful for everyone.” —K. E. Brian Jay, eg2HJ. “June: The general impression _ this month is that the pet 23-metre band has been bad—at any rate, compared with previous months. It would seem by con- parison with last year that this state of affairs will last until about next February, as far as super-DX is concerned. “5YK worked Nu fourth on phone and got R4 with 60 watts crystal. He could not raise either the sixth district or the Antipodes, both of which were weak. He is working on a ten-metre crystal set, em- ploying a new principle. This station will be ready to go on 10.15 metres as soon as the license arrives. “5YX has done nothing, being QRW with exams . 5BY has been going strong, how- ever. 2XV found conditions rather poor, but in spite of this worked su2BT, sb2AJ, sb2AX and a few NU stations; also oa2RB on 32 metres, the others being on 23. Fre- quent QSO’s were had with nullII to make various arrangements about his visit to England. 2XV will shortly be on the 8-to 10-metre band and reports will be welcome; the word TEN will be sent after each trans- mission to show it is not a harmonic. Oper- ations will probably commence early in August. “Other hams busy on ten metres are 2NH and 6QB, who also are to be found on 23 and 90. 2CX worked sB and SC, so is now WAC. Very FB OM. 2AX worked lots of NU’s and sc and aQqon 23. 6WN cannot raise NU, so would welcome re- ports on his signals if any one hears them. 6CL on 23 was called by an Nuvu four, but did not hear him. 6PA says NU is only local when conditions are good. 2CB worked OA, sc and Nv first, on 23, but has difficulties with the States; he, too, would like reports. “6RB worked the world on 23 in May, but has not had any luck in June. “Many hams are rebuilding and getting set for next year, and 5YK’s standard fre- quency transmissions are being found of the greatest value. 6QB with his standard R.S.G.B. wavemeter is pretty busy, too. Most of the British members are now pre- paring for the new Washington wave- lengths, which may become effective any day now. —K. E. Brian Jay, eg2HJ. FRANCE From a letter sent in by our old friend Leon Deloy, one of the past presidents of

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nonth Ss dud ill be fF sthe 1 and hams omed, 2 not lerful AJ. this 1 has with com- te of uary, and could the He em- will nm as with how- poor, 2AJ, 2RB Fre- nake t to 8-to me; ‘ans- )per- - in 2NH 1 23 now lots WN re- ears our, J is 2CB has ould fay, end of “ROUND THE WORLD” FOUR Just What the Name Implies! The trimmest short wave set ever—that’s the verdict everywhere on the new 730 $M “Round-the-World” Four. It does everything you expect of a short-wave receiver —everything, even, that you expect of an S-M receiver. The Radio Broadcast Labor- atory, in initial tests of the 730, received English 5SW daily on the speaker, during afternoon hours. 9BBW, receiving on the “Round-the World” Four, worked in one evening stations in Germany, France, England and Italy. Low-power amateur coc: stations over the U. S. and Canada are received regularly on the 730. And for television work, it’s ideal! The “Round-the-World” Four is a complete four-tube regenerative, non-radiating short wave receiver kit with aluminum shielding cabinet. It has one screen grid r.f. stage, a regenerative, non-radiating detector, and two high- gain Clough audio stages. It tunes from 17.4 to 204 meters with four plug-in coils. The kit is $51.00, complete with cabinet, four coils, and full instructions—ready for immediate shipment The 731 “Round the World” Adapter is the two-tube, r.f. amplifier and detector, less the two stage a.f. amplifier of the above set. With an adapter plug, it converts any set to long-distance short New S-M 131 Plug-In wave reception. Price, complete with cabinet and four coils (17.4 to 204 meters) $36.00. The 732 Coils (used in the 730) “Round the World” Essential Kit contains the two tuning and tickler condensers, the four plug-in wound on moulded coils, coil socket, and three r.f. chokes, with full instructions for building a one, two, three or four * ~ ~~ He tube short wave set. It costs but $16.50 complete. wy $1.25, or And it beats anything for getting out into the short-wave “Thrill Band.” Choose the kit you blank, $0.50 each. prefer—and “‘step out!” 720 Screen Grid Six Audio Transformers The Year’s Biggest Value Just Two Years in Advance This is the set that S-M gets squarely behind and tells Radically new in principle, these transformers are the you it’s the biggest value in broadcast-band receivers to be first to give freedom from the hysteretic distortion found in all found today. A man-sized recommendation! other types. They combine decided advances in both tone Successor to the famous Shielded Grid Six that took the and volume, as will be seen below. E is the two-stage curve country by storm, the 720 is the kind of a set you can build for the large size transformers (S-M 225, Ist stage, and 226, in an evening, on its pierced metal chassis. When it’s fin- 2d stage, $9.00 each); D is that of the smaller ones (S-M 255 ished and you put it on the air—then the real surprise begins. and 256, $6.00 each). Note the marked advantage over A, Distant stations will come in, one after another, with local B, and C—all standard eight and ten dollar transformers under equal conditions. And you can have this finer performance in any set at less than average transformer costs! S ~~ ° volume, and positive 10 kc. selectivity. As to tone, the 720’s Y tuperiority is insured by the new 255 and 256 audios, as = described at the right. ' \Look at the 720’s features as you see them in the picture, 5 * and remember that S-M backs it to the limit—assures you that 4 you can’t get more actual radio elsewhere at twice the cost. d — it i Then note the prices: Custom-built complete in a beautiful oe ” eae two-tone brown metal shielding cabinet, $102.00. Complete : 7 ° The S-M catalog describes all these products, as well as A gm — with = see Ga.2S additional. and B Power Supplies, Power Amplifiers, Modulation tter order now—such values spell scarcity! Transformers, etc. ements meer | Seem Silver-Marshall, Inc. Are you receiving the “The Radiobuilder” regularly? Every month it gives you all the earliest S-M news, operating hints and kinks. To SM Authorized Serv yoy YF — on of, ea ith all 858 W. Jackson Blvd., Chicago, U. S. A. new constructional Data Sheets. If you ild professionally, write l ith us about the Service Station franchises. = | eee ee a a ay W. JACKSON BLVD. .-For enclosed 10c, send five sample SILVER-MARSHALL, Inc., OMICAGO, ~~ U. S-M Data Sheets. Name. ccccccccccccccesscccccesesssess iicisiorencncarcaeaas aaa Se ——— TT Say You Saw It In Q S T — It Identifies You and Helps QS T 67

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\ detailed treatment of vacuum tube cir- cuit theory If 5 een this book to examine it, with a depend- te liscussion of reuits; places y developed be used in roblems with theory to of amplifier ch phase of ube circuits HE ORY “OF [ERMIONIC vi \CUUM TUBE CIRCUITS > JAMES PETERS f Electrical En 4 of Wisconsin istrations, $3.00 ughout this to furnish 1 of funda iliarity with that nd cireuit liscussed iy blems so a | MoGRAW-HILL FREE EXAMINATION COUPON | 8 Me Co., Ine., ‘ R7 A nue ' ; Ne y ! Bs Peters’ Theory of Thermionic ; gs Va r $3.00, postpaid. I will either » g re ystage prepaid, in 10 days, or re 1 ' me ' - a Ee. wensetneenisesnetnscedossadasecnhaesmennest ' Bc ! Dar” nt SttOoeseentenntenastonsaredennnenanenesen . 7 0z=.LpRL Lee eee eee ee ee ee ee es ' DT: eenkesaeuenean cacepadeneaddeuneeetteumebaaas ' 8 wy m ' @2 P 60tes600peckeewesatacesiasauseus ‘ 7 en DOO 2600006600000 60h ed esedekeekewndens 1 1 valinthe U.S. and Canada only) § : Q.S.T. 8-1-28 8 eR RP Fe we ee eee eee ee eee ee “mike”’ » button * similar to cut, priced St t Type, ideal for public address, etc., price formation, A new special bulletin on all short w ready. EFT \N COMPANY Waseca, Minn. SPECIAI TO A Bar — RADIO BARGAINS ame Shows the latest wrinkles, new- Le ; eve lopmente in radio at startlingly tha w prices. Get the set you want here desir nd save up to 50%. The best in parts, rt kits, complete factory-built sets and’ Gui supplies wasn y ey same day re- rarer ceived rite for free Catalog and Guide NO . slesale prices to dealers, seh butler aa BARAWIK CO., 119 Canai S Chicago, U. S. A: Say You Saw It In QS T —It Identifies You the R.E.F. (Reseau Emetteurs Francais) we learn that in a recent election a new president was appointed to this society, and is Mr. Reyt, Professor au Lycee, 24 Rue des Vaupulents, Orleans (Loiret) France. Mr. Reyt, who is well-known to all ama- teurs through his calls 8FD and 8YOR, was elected in May; Pierre Louis and Mr. Deloy become Honorary Presidents. We extend our sincere congratulations to Mr. Reyt on his new appointment. GERMANY A card from ek4HX, contains this inter- esting information: “IT beg you to put a few lines in QST about QSL’s for EK. Many NU amateurs send cards direct, but that is dangerous for us, and the cards often do not reach their destination. All cards for EK sta- tions should be sent via DF TV, Berlin W57, Blumenthalstr. 19. Perhaps NU OM’s don’t know that all Ek stations with a ‘4’ and only two letters in the call-sign are unlicensed.” 2@e Remodeling the Traffic Tower (Continued from Page 42) depends upon the position of the band on the diai To cover 500 kes. starting at 3500 kes. requires a dial rotation of from 134 to 18 degrees or 116 degrees. Now, if we start at 3350 kes. or 147 degrees, we have to rotate the condenser only 72 degrees to get to 3850 kes. Thus if we cut our coils so as to place the desired range at the lower dial readings, the maximum dial rotation will be obtained for a given band. Of course, at the lower range of the con- denser, any changes in circuit capacity will have a larger effect upon calibration than at the higher capacity settings. With this in view and the thought that the minimum capacity across the coil due to the tube socket, wiring, etc., may vary to some ex- tent in other receivers, no effort was made to squeeze the last dial division out of the ranges. He who is so inclined may do this; others will perhaps be satisfied with the ranges as they are. At any rate, it re- quires but little effort to add or subtract one turn, more or less, and you can suit yourself. Well! So far we have a pretty decent 1928 affair but it isn’t much of a world. beater for the 1929 conditions. By doing some more adjusting and shifting, we can make it into just as good a 1929 set as it is a 1928 one. The shunt adjustable condenser can be dropped because there will be but five bands in all—and the smaller section of the tun- ing condenser will be employed for tuning on the 7000- and 14000-ke. bands while the two sections in parallel will be used for the 1750-, 3500- and 28000-ke. bands. Of course, they will both have to be reduced in capacity. and Helps QST @ Cro © posi opera any t oat dible rec i any Ms furnite ley easily d for ion int of | binet. f Powe!

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cais) new , and Rue ance, ama- YOR, Mr. ns to leplace Your Old Radio! radios at any price ALL the following which are so neces to the fine radio re- » you may have to Crosley gives you ALL at the world’s * prices \Eur=ooyNf ‘2 FICATION i Other syoreame 5*5*5-125 Radios tune efficiently Crosley neutrodyne ait ig sharp, sensi ad selective Radios are shielded dement is shielded each other. This 0 the efficiency ol gt. Stations close ber are easily sep- .J «ire Radios are selective stations are ded together you ) seppreciate the ive qualities of ay radio You ps to ONE station a time. felt ; - a! Radios have volume volume of Cros Radios is phe- nal for the ht amount of bat or AC current wmed, The vol- miay be in 4 tremendously thout distortion 2% Self-contained A C electric receiver. Utilizes two radio, detector, two power and a rectifier tube (171 power output tube). Operates from 110 volt 60 cycle A C home lighting current. Try this amazing set. Prove to your- self on a 5 DAY FREE TRIAL IN YOUR OWN HOME that no radio that approximates Crosley price can compare in performance. Why pay Radios higher price? be softened . r : , toa whisper This wonderful little Gembox is designed to use the new and as- tounding dynamic. DYNACONE the Crosley power speaker, which is radio’s greatest development this year. A genuine dynamic speaker selling for $25 equals ANY in pure realistic tone— unmatchable in price. volume con a Crosley sets positive that operator may any broadcast m down to m end scarcely dible reception. oh Radios any kind of furniture side cases of ley radios easily re- d for instal- 5 iube dry cell operated BANDBOX & $35. io into any Ideal ». et of console : recharging inet. : va storage battery is.inconvenient Dept, 18 I can not locate a Crosley dealer ease arrange f L in my ne 5 DAY The Crosley Radio Corporation Ci . . . : % Rie ae Ohio = | Bancbor ‘s rosley, Jr., President Musicon a | acon i} Crosley, = President Musicone ( ( ) Dynacone ( ) 10 and West Prices slightly ido. Ne ‘ Name ..._. higher. oe ¥ Radio Prices do i = t : not include Adie | tte ee. Say You Saw It In Q S T — It Identifies You and Helps QS T

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> Push-Pull Power Stage for Dynamic Speakers I st results, every dynamic type speaker be preceded by a push-pull amplifier. This arly true because they reproduce fre- ; low as 30 cycles and the attendant raw AC on the filaments of power tubes is greatly ess filtersd out by a push-pull amplifier. completely wired push-pull power stage has been gned for dynamic speakers, Consists of type 151 in- t transformers (100 for working out of 210 type tubes type tubes). Completely wired with sockets and vailable for cone type speakers and for both 210 t Patents owned or controlled by R.C. A. 1 may be bought with tubes e complete( without tubes) $36.00. ghely higher west of Rocky Mountains) eas for hook-up of this remarkable instrument, \MERICAN TRANSFORMER COMPANY former Builders for more than 28 Years 194 Emmet Street, Newark, N. J.

(,uaranteed to Stay Accurate thing to build a resistor that ell in a quick test, and decided- to give it a month’s trial carry- rk-a-day load before testing it. in accuracy can be (and rprising. Har-field Resistors for a month or Day after day they will carry were built to carry, and main- racy your order specifies. For Field, Inc. have built the ac- t heir resistors that enables them y make their guarantee. ld Resistors are made in two types the vitreous enamel or specially vent. They come in a wide nlues to suit every need, and ities of any type or size can upplied. Prices are low enough 1 consideration from every care- ing agent and individual. bout the resistor you want and make up samples for you HARDWICK, FIELD, INC.

i r SALES OFFICE HAR-FIE FACTORY 122 Greenwich $ 215 Emmett St. How York Newark, WN. J. WIRE-WOUND RESISTORS ' SS A A A A <a 7 Say You Saw It In QST 70 The distance between the plates in the smaller section should be increased until the 7000-kc. band is covered by a dial rota. tion of somewhat over 100 degrees. The spacing will be roughly equivalent to the thickness of 20 QST pages. In the other section, we can no longer use the capacity obtained by a single stator plate between two rotors and must shift the stator so that it is exposed to but one rotor plate. In this respect it will be similar to the smaller section although the spacing between the two plates will be less (about 10 QST pages). We then get the following coil sizes and ranges:

Turns - -y s Sevtions ‘or of Band in kes Coil Range Sec Tickler Band Condtnser 1715-2000 1675-2055 77. 9 98 Both 3500-4000 3279-4000 37. 6 120 Both 7000-7300 6666-7316 26.25 5 118 Smaller 14000-14400 13045-14460 9.25 4 60 Smaller 28000-30000 27900-30800 2.75 3 45 Both The types of winding, size of wire, spac- ing of turns, etc., are the same for these coils as for the previously described ones. The same coils may be used with the neces- sary turns added or removed as the case may demand. eer Radio Set Tester batteries or socket power devices. The various ranges are 600, 300, 60 and 8 volts and a resistance of 1,000 ohms per volt is had for all of them. Direct current ranges of 150 and 30 milliamperes are available for checking the plate current of the tubes as well as the output of various of the com- monly used rectifiers. For sets employing tubes similar to the UX-226 and UY-227, there is an a.c. volt- meter having ranges of 150, 8 and 4 volts. The four-volt range is used for checking the filament voltage for the tubes men- tioned above, the eight-volt range will be convenient for ascertaining the voltage across the filaments of 171s, 210s and the various rectifier tubes now in use, while the highest range may be used to deter- mine the line voltage which may vary con- siderably in some parts of the country. It is possible to make measurements upon a tube under normal operating con- ditions employing for such tests the regu- lar power supply to the set. It is also possi- ble by means of a switch provided for that purpose to change the bias on the grid of a tube and by measurements of plate current to ascertain whether the tube is in good con- dition. A rotating switch is so arranged that measurements of the plate and fila- ment voltage, plate current, bias, etcetera may be made in succession without moving any of the equipment excepting the switch. A product of the Weston Electrical In- strument Corp. of Newark, N. J., this in- strument is known as their Model 537, Ra- dio Set Tester. —H. P. W. It Identifies You and Helps QS T

SpaPtF®§scTezszsaocz

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The Mershon Con- denser gives a very large capacity in a very small space. Is self-healing in case of puncture, and is un- affected by changes in temperature, or by moisture. Expert radio amateurs used the Mershon Condenser for more than six years in their trans- mitting equipment. Today the Mershon Condenser is being widely used over the whole coun- try in connection with electrical radio sets, whether new AC tubes are used, or battery sets are at- tached to house current thru the use of Eliminators. Send for Your Free Copy of This Book.... Say You Saw It In Q S T — It Identifies The AMRAD Corporation Medford Hillside, Mass. of your new book d y onthe MERS HON CONDENSER, show- ing hook-ups and designs. You and Helps QS T

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BUILD A DAVEN TELEVISION RECEIVER Kit Furnished with either T-24 Scanning Disk Motor, Bushnig, Rheostat Tube 3 Complete Stages of Daven ation and = Instructions for Building. Receiver, Complete, in Tube—$100.00 Less AVEN TELEVISION APPARATUS Scanning Disks Each -- $ 5.60 10.00 24 t and §=648 XN 15.00 BS cocccccess 12.50 Amp. T-4 for 2 ! 2 power Tubes Types Lamp 20 to 80 Stricking Voltage x1% each 12.50 t % inch 5-16 Motor Shafts 1.00 Aperture dis¢ 3.50 Elect. Cell 1% Elect Cell 3 inch Couplers i2ix D-42lxx ix D-422xx x D-423xx 1 for Grid and Plate resistors 2 Plate and Glastors in Grid 4.65 tubes in series with Tele brighter illumination) Mu Tubes for Amp. Stages 2 ver Tube .. 3.50 end stamp for new Television Booklet. THE DAVEN CORPORATION AMPLIFICATION SPECIALISTS 170 nmit Street Newark, N. J. Tete Me) y ERN RADIO 1929 Catalo? Dealers and Set Builders "THE NEW 1929 Cata- : og is crammed full of FINEST, NEWEST, nallyknownA.C.sets, es, cabinets, dynamic skers, kits, PARTS, mators and accessories )WEST PRICES. t stock of radio parts, t delivery. rour FREE catalog WESTERN RADIO MFG. CO., 128W Lake St..Dept.Q9,Chicago ge e” Radio Hous Say You Saw It In QS T— It Identifies You and Helps QST Calls Heard (Continued from Page 51) Yanz Yara Yasx Yavu Yaxf Yaze Ybga Ibgq Ybmx Ybay 9bwk 9cfr che Ycok Yerd Yesr Yecuh Yevd 9dk Ydke 9dmt 9dng Yecl Yef Yegy Yehd Yeoh Yesh Yeyq 9ez 9fci 9fbw YIpdj Y9few Y9fly 9fnz 9hm Ymt af-kol ai-2kt aj-jll am-3ab fe-2vo fe-sux fk-4ms fm-Sags fm-Sey fm-8jo fm-8rit fo-a3a na-7ady na-7aer na-7mn ne-cf ne-cq ne-lar ne-2be ne-2ca ne-3ap ne-3cj ne-3es ne. 3fe ne-4dq ne-4fv ne-4ha ne-4hh ne-5au ne-5bn nm- 27a np-wet np-4agf np-4sa nq-2kp oa-2dy 0a-2ij oa-2jy oa-2re oa-2sh oa-2uk oa-2yi oa-3bd oa-3gr oa- 3jj oa-3jk oa-3lp oa-3my oa-3vp oa-3xo oa-4lj oa. 5bj oa-5bw oa-5by oa-icm oa-5dx oa-5hge oa-5wh oa- 7ch oa-Tew oa-vip oa-vis od-and od-anf oh-6alm oh- 6avl oh-6bqj oh-6dey oh-6dki oh-6dud oh-6dvg oh- npm oz-lao oz-2ae oz-2bg oz-2bx oz-3at oz-3aw oz-3az oz-4ae oz-4am sb-sqi sb-law sb-lib sc-3ac sc-3cj sl-hjg si-hjo. (On 40 Meters.) lagg lagw lajec lakk lanx lanz laqi lart lasy laxq lbat lbdm lbed Ibki Ilbia lboe Icft lcjz lemf lemz licxj lgw lhb lic 1kb lkm llt Imk Imr Ing lsi lvt Izh 2ace 2adl 2afa 2afw 2agw 2ajb 2amh 2ans 2apl 2apv 2aql 2ase 2avz 2axk 2ayk 2az 2am 2bey 2bda 2bdh 2bek 2bgb 2bege 2beq 2bgz 2bhv 2bih 2ble 2bov 2bse 2btb 2bts 2btt 2bxr 2cdm 2chu 2eot 2eqd 2ewm 2cxl 2cyx 2dn 2dp 2dq 2fs 2gh 2gq 2ja 2je 2kl 2kr 2lx 2mb 2ps 2qe 2rk 2sj 2uo 2ve 2vd 2wi 2xd 3aac 3aaj 3acn 3aef 3ael 3afl 3afw 3afx Sage Saib 3ajt 3amw 3anh 3aob 3ard 3arh 3arx 3ath 3atn 3ato 3aua 3auj 3auv 3auw 3bce 3bel 3bgg 3bip 3bn 3bns 3cbt 3cfg 3cjn 3dh 3ec 3er 3ez 3gb 3er 3kd 3mb 3qt 3sz 3ve 4aba 4abz 4ac 4dacv 4ada 4adf dado 4Aaec 4aeg 4aek 4aem 4daed 4dafe 4agd 4aw 4ay 4cj 4ck 4dt 4ec 4ei 4ft 4g] 4gy 4hk 4ib die 4iq 4jo 4jw 4kv 4ky 4lj 400 4ox 4px 4rn 4rr we 5afx 5agz 5ain 5aja 5apo 5are 5as 5ats 5axn 5Sayl Sbe Ser She Sie 5ih 5je 5iy 5kh 5mx 5oc 5ql 5uk 5vh 5vx 5yb 5yw 6chk 6dww 6Geah 6ju 6xb Tek Saau Sadu Sagu Sahu 8ajj Same Sapn Saty Savz Saw Saxg Saxz Sbaz S8bbj S8bbs &bi Sbky 8bjx S8bpa S8brh Sbuj S8bva S8bvy S8bwn &8bwr S8cau Scbd Secs Scfb Sche Schz Sclq 8cmf Scmo 8eng Scpe Seq S8cof Sess Sexe Sezr Sdal Sdad S8dbs 8ddu 8dfd Sdhx 8dsa Sdps &8dqi Sdra S8drg She Snt Sqb 8qh Std 8tn S8uj Yaee Yaeo Yaghb Yaju Yake Yaou Yasb 9awt 9axu 9baz 9bea Ybre Bbsh Ybwo Ycia Yeis Icke 9enc 9cos Icph Yesr Yeue Yeuv Yevn Yceya Ydb Ydbi 9dga 9ds 9efz Yell Yelp Yeqp Yeru Yetd Yetv Yeul Yexr 9ezu 9fcg 9fgp 9fkz 9fs 9lx 9m! 9ng Ynr Ysx Yxi naa nar nixb wee wiz woo wuo oa-2bb oa-2dy oa-2lm oa- 2re oa-2yj oa-3¢t oa-7lj oa-vim oz-2aq oz-2bg oz-2ga oz-3aj oz-3ar oz-3au oz-3cg oz-4ae oz-4am fe-2vo fe sux ne-cf ne-2ca ne-3dz ne-3zb ne-8ae xnh-2vq nm- 9a nm-xcsi nn-Inic nq-2cf nq-2iq nq-2se nq-5fl ne 5uz nr-2ags nr-2ea xnu-6cly ny-laa nz-fo5 sa-lp sb poaa sb-3qa sb-9aa sc-cnag sc-2ab sl-cos sq-2g. 8AVS, Donald F. Byram, 43 River St., Homer, N. Y. (20 Meters) eb-4au ef-Seo ef-Sct eg-5ml eg-5uw eg-5vl eg-6hp eg-5sk eg-6ut eg-6qb eg-6ht eg-6vp ei-Ifp em-smpv em-smzf gi-2by gw-l7c nr-cto (40 Meters) eb-4wx eb-4ro ef-8gyd ef-8fc ef-8lx ef-8rbv ef-8hpg ef-Ser ef-Sorm ef-8xd ef-8ix ef-Sest ef-Sbtr ef-8fxf eg-6rm eg-2nn ep-lbx fm-8rit fm-S8ags fq-pm en-ozf oa-3ls oa-3ep oz-3az oz-4am oh-6adh oh-6dey nm-lz nm-9a nm-Sa nn-lnic nq-2ac nq-5ex nr-2ags ns lfmh sb-law se-2ah. eg-GWY, H. Almaxwell Whyte, Burtleigh, Charch Road, Forest Hill, S.E ldi lauk 1gx lbeb lbat Iblif 1bz lcaw Ilbke lasu lcjh lue 2blx 2aoj 2cjd 2afx 2bew 2bha 2m¢g 2axx 2caq 3di 4fs 4adb Saxa 8auc Sbtr 8drj 9dbj Yasd Yef. 8DDK, Hosea Decker, Delaware, Ohio (Heard from April 18 to May 16) oa-2dy oa-4ab oa-4nw oa-4]j oz-4ag faq-ocya eb- 4au eb-4fp ef-S8est ef-8fc ef-8hpg ef-8lx ef-Swb e- ldy se-2ah sb-law sb-lid sb-2ag sb-2ak ne-8rg nm- irz nm-9a nq-2jt nq-5ea nq-5cx nq-5fl nr-2ags nidk. ef-8XD. laac labd labt labv ladm laff lage laha lalb lalr lals lamu lapv laqp laqt lavk lauz laxq lbbe 1b lbft Ibke 1bjx Ibu lbux Icjh lemp lemx lepe Icki 1jaa Inq loh lom Imx 2aca 2adl 2aeb 2aco 2afw 2ahh 2aib Qafb 2akj 2ajg 2api 2ass 2atq 2atx 2awb 2aul 2avw —- =)

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r-6hp smuv Shpg -Sfxf n-ozf m-lz ns- urch lasu 2axx . e- nm- idk. lalr lbed 1jaa 2aib avw THE AMATEUR’S BOOKSHELF Readers of QST appreciate the need for good radio books. What we consider to be the best standard text books are handled by A. R.R. L. Headquarters for the convenience of members of the league and readers of QST. Those listed below pretty well cover the requirements of the average amateur or experimenter. The Radio Amateur’s Handbook, by F. E. Handy, Communications Manager, A.R.R.L. Third edition. The standard text book and manual for transmitting amateurs. Contains immense quantity of data and information valuable to experimenters and all interested in any phase of radio. 256 pages, 297 illustrations ................-- $1.00 The Radio Amateur’s Handbook, Cloth Bound Edition. Except for binding, identical with regular edition ..............0eeeeeeeeeeees 2.00 Radio Telephony For Amateurs, by Stuart Ballantine. One of the most valuable books we know of for the amateur. Theory, construc- tion, practice. Not particularly about telephony. Heartily recom- mended for every amateur. 296 pp., 54%2x8M% ....... ccc cece ecenees 2.00 Manual of Radio Telegraphy and Telephony, by Commander (now Admiral) S. S. Robison, U. S. N., published by the Naval Institute. “Ranks with the very best of all published radio matter . . . Not only worth its cost but is perhaps the best radio book that ever came to this desk.”—QST Book Review. 895 pp., G4X10 ......... cc cccccccccces 4.00 Experimental Radio, by Prof. R.R. Ramsey. Third Edition. A splendid manual for the student and experimenter describing in detail 117 experiments of particular value and interest to the amateur desiring a complete understanding of radio work. 2.75 Principles of Radio Communication, by Prof. J. H. Morecroft. An elaborate general textbook. 935 pp., 554x9 ..........c ec cece cece 7.50 Radio Engineering Principles, by Lauer & Brown. An excellent gen- =— eo as Sees See ee rae re ee 3.50 Practical Radio Telegraphy, by Nilson & Hornung. 380 pages, 223 illustrations. A text for prospective commercial radio operators ..... 3.00 ‘Wireless Pictures and Television, by T. Thorne Baker. 188 pages, 99 illustrations. Completely and clearly presents the whole subject .... 2.50 Thermionic Vacuum Tube, by H. J. Van der Bijl .................... 5.00 Radio Frequency Measurements, by Moulin ....................... 10.00 Prepared Radio Measurements, by R. R. Batcher .................. 2.00 Elements of Radio Communication, by Ellery W. Stone ............. 3.00 Radio Simplifier, by Kendell & Koehler, revised by J. M. Clayton .... 1.00 Ideas For The Radio Experimenter’s Laboratory, by M. B. Sleeper ... 25 Prices include postage Read ’em and learn! AMERICAN RADIO RELAY LEAGUE, INC. 1711 Park Street - - - - Hartford, Conn. Say You Saw It In Q S T — It Identifies You and Helps QS T

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\ x Control Your Volume! A Complete Line of Volume TONATROL Observe this caution in building your re- eiver Make sure you can control the ie smoothly and easily by incorpora- Tonatrol in the circuit. mu ely Licensed by ne Corporation S. Patent Nos. 1034105, 1034104 } are the highest development in ntrols and are designed in types the special requirements of all or conventional battery circuits furnished with filament or power tch attached Electrad specializes in a full line of con- trols for all radio purposes. Write for FREE descriptive circulars. Dept. T-9, 175 Varick St., New York nounces with Pride and Pleasure \ New Condenser Trade Marked, Surgproof +P ROOF Condensers carries an imme- replacement guarantee if defective within RGPROOF Condensers have a safe work- tage of 1300 volts D.C. and are recom- l¢ | Ux Wr ‘be Deutschmann Company '20 for any high-voltage amplifier, using 210 Power Tubesin Push Pull or the » tubes. lin a familiar Tobe Silvered Case 414" 2 2Mfd $5.00. Type 1304 4Mfd. $9.00° r Sale at Your Dealers Canton, Mass. Say You Saw It In QS T — It Identifies You and Helps QST 2az 2bad 2bav 2bbe 2bee 2bek 2ber 2bdf 2bfg Ae! 2bgg 2bjg 2bif 2bsc 2bke 2cin 2com 2erb 2euq 2ex 2cyx 2fg 2ge 2hr 2dg 2nm 2rs 2up 2tt 2sz 2wi 2 3aa 3aee 3afj 3aih 3anh 3ajh 3aqi 3aqm 3apm Saod 3aqz 3aso 3bip 3cfg 3cjn 3dh 3lz 3qw 3qe 4aby dar 4ac 4aef 4aej daep 4aek 4f] 4ds 4br 4cj 4ceq 4ge 4q 4km 4me 4th 4tk 4td 4we 5acl 5atf 5ayl Sre Sy 5yb Sadg Sary Saw Saxa Sawu S8baz 8bbs Sbfw sh Sbaf S8bjb & hz 8baqr S8bou Sbto Sccg 8clp Senh Sen Scpr S8ctl 8dad Sdnf Sdod Sdsy 8gz Yain Yama Y%by S9cia Yerd Ycue Ycad Yef Yerh Yejo Yeex Yecz Mfg 9tm ne-lad ne-lby ne-lbr ne-Irr ne-2be nm-Irz nm. 9a nq-2ac n2-2cf nq-2kp nq-2ig nq-2ro nq-5ea nq-5ay nq-5by nq-5cx nq-5fce nq-5fl nq-7cx ns-lfmh nz fr5. ecRP19, Al Weirauch, Mestec Kralsve lawe iby Ickp 2cxl 3sz nq-5fl sa-de3 sb-lah sb lat sb-lar sb-laq sb-law sb-lbo sb-lca sb-lcg_ sb-lij sb-2ac sb-2ad sb-2af sb-2ay sb-7ab sc-lah sc-lai sc-2ab (20 Meters) lads laff Iry 2arb sc-3ac. eu-78RA, W. Nelepez, USSR, Leningrad 2 27 Sagorodny pr log 13 lbt Imf lom 2cuq sb-2ad sb-2ay sc-2as sf-ldy fe-gm fe-les fm-8ssr xed-7sch xed-7rl. S.S. DROMORE CASTLE, New York City to Cape Town, South Africa, via 2CUF, Operator Clyde Townsend, care the Union-Castle Mail Steamship Co., 26 Broadway, New York City. Port Elizabeth to 5000 miles S. E. N. Y. laa laba lawq laun lbgq ickp Iino Inq Irp lut 2apd 2aqr 2atk 2atx 2aub 2axt 2bda 2bhr 2bke 2chb 2euz 2cxl 2exr 2ja 2k] 2kp 2mu 2ty 3aef 3api 3ard 3bme 3qe 3py 3au 3avk 4dabz 4acv 4ob 4tk 4ut 4vh 4we 5ayl 5uc 6avl 6awa 6ccw 6ue Tawa Tek Sawu &bbs Sbhz S8bto Sbyw S8ccew Schi Scxt Sdal 8eq 8xas 9bhe 9bwo Yeaj Yecx Yeln Yerm O9fbv Y9fhy Yra afk arbm as-rao3 byc byb byz ea-lh eb-4co eb-4di eb-4ft ee-ear28 ef-Sev ef-8fd ef-8fx ef-8nox ef-80rm ef-8vvd ef-8wb ei-lfp en-ofp ep-laa ep-lae et-pju ew-hb fk-3ms fi fo-2srb fo-a3c fo-a3t fo-a3u fo-ade fo-ado fo-a4v fo-a5l fo-abo fo-a5t fo-6sra fo-a7b fo-a7d fo-a7gz fo-a7n fo-a7q fo-a8j fo-a9a fo-a9l fo-a9n fq-8hpg fq-ocya fq-pm gbj gebr gfa gizt gkt gill ido isf kfu kzet lgn ocdj od-3bk oh-6avl oh-6dty ohk por rili rza_ sb-lad oxz ozce pch pepp pdt pkh rpo sb-laq sb-lbt sb-law sb-lbo sb-lca sb-lem_ sb-lid sb-lno sb-2ad sb-3qa sb-5bf sb-7ab sfv sof soh swmk wnbt wuaq wva vkef vtc. 5000 to 4000 Miles S. E. N. Y. laoi 1bki lckp lgw iro Irp lom 2apd 2aub 2avb 2bdf 2bhr 2bts 2cuz 2ev 2iq 2sm 2sm 3avk 3bbw 3bnu 3sj 3vge 4aba 4dabge 4hy 4nc 4vp 5ayl 5sz 8acz Saxd Saxz Sbbs Sbky 8brh S8bvy S8che 8cgk 8cmo S8cyg 8dps Sdrj 8fhy 8ez 8li &8sx 9anl 9cev 9enr 9fgs byb byw ee-ear28 ef-Swbh ek-4abm ep-3am fo-a3z fo-a5t fq-ocya fq-pm gbr gfa gkt ido Ign naa ocdj peh rza sb-lah sb-laj sb-lbg sb-lcj sb-lem sb-lid sb-2ad sb-2ah sb-2aj sb-2ar sb-2ba sb-5aa sb-7ab su-loa snu sof sqbx spp wiz wnbt. 4000 to 3000 Miles S. E. N. Y. labt lade lage lajd lalb lamf lanz lau lavf leng lenz liga lic ljm ikh Ikr 1lx Imx lIpu Irp 2afa 2apd 2aql 2aqw 2auo 2baz 2bda 2bfn 2bhr 2bkk 2buy 2byw 2cot 2kx 2tw 2ty 2uo 2vi 2za 3aa 3aaj 3aco 2afj 3afx 3am 3aqm 3arx 3aui 3auv 3cs 3ee 3nn 3nr 3qe 3sz 4acc 4acz 4ar 4at 4uq 4vh 4wm Sabi Sauz 5awd 5Sayd 5Sayl 5bt 5fo 5ke 6lv S8apn Sawu Sbbt Sbdt &bkh &Sbky Sche Schz Sent Scpd S8cu 8eq 9afi 9ak Yapi 9bir Yceb Odku 9dmt 9dlj Yeln Yerh 9fhm 9fnz agb agj byb byc eb-4di ed-7rl ee-ear65 ee-ear 28 ef-8fj ef-8pam eg-6kd ep-lae ep-lbx ep-lms ep-3am ep-laa fq-8hpg gbr gekt gzce hjo ne-4fv nkf oze pepp pid ptt sa-en8 sa-a2z sb-laa sb-lah sb-laj sb-lan sb-lar sb-law sb-lbg sb-lbt sb-lca_ sb-Icb sb-lcj sb-len sb-lid sb-1t] sb-2ag sb-2aj sb-2bf sb-3qa sb-5aa sb-5bf sb-7ab sc-2aa su-lfc shin snn spw spx sqcl sqpa wet wik wiz waqo wvr. 3000 to 2000 Miles S. E. N. Y. ladb lafd lany lasu lax! Ibcbh lbqt Icio Ickp Icnz Ino 1 nu Ilvt 2ail 2Zamt 2ans 2aqd 2ass 2aup 2awa 2bav 2bda 2bif 2bit 2bkk 2bts 2bxr 2byw 2ch 2cxl 2dr 2k] 2mb 2qu 2sm 2ve 2wi 3ahh 3anh 3aob 3av 3bj 3d! 3ff 3sz 3sn 3wm 4acd 4acn 4aep 4ec 5gr 6aal S8agk Sake Sakv Sank 8bjb Sbpa &8btr S8cnt 8cnz Scyg Sdds 8dfb Sdhe 8dnf Sdps 8dpw &8sx 8uj &xl 9esb 9ef Selb 9fax 9my Yuu byz ea-jh eb-4bu eb-4di ee-ear28 ef-Saa ef-Sajf ef-Sbtr ef-Sed ef-8fiz ef-8hpg ef-8il ef-8lx ef-Sorm ef-Srrr ef-Swb eg-5ma_ eg-5vl ei-las ei-lbs ei-ldy ep-laa ep-lbv ep-lbz ep-3am ep-3gb fi-lab fo-a5l fq-ocya gbo gbr gkt hjo kav

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2bfgz bey Zcuq 2ey) Zz 2wi 2p lapm 3aoj 4aby dar q 4ge 4a 5rg by Sbfw sh Senh Seni ama 9%by ecz Of gp i-lrz nm 2a nq-bay fmh ne re lah sb tg sb-lid ai sc-2ab 2 27 ly fe-gm to Cape tle Mail City. ce Irp tut ke 2chb ipi 3ard dut 4vh k Sawu eq Sxas dra afk i eb-4ft ef-8vvd ew-hb fo-ado fo-aT7d fo-a9n rkt gil Ity ohk sb-lad sb-lid of soh » 2avb nu 3sj 1 Saxz 8dps b byw q-ocya sb-lah sb-2aj X spp leng 2afa 2buy 3aco 3nn 5abi Sawu | Seq 9erh -ar65 lenz -4di hpg 5vl am Are YOU among the 35,000 who refer daily to a copy of the Radio Amateur’s Handbook for Guidance and Information? If Not, get a copy NOW We believe that The Radio Amateur’s Handbook, by F. E. Handy, Communications Man- ager, A.R.R.L. is the most valuable book which any amateur or experimenter could own. Its chapter headings will give an idea of the thoroughness with which the subject is covered. They are “What Is An Amateur?” “Getting Started”, ‘“‘Fundamentals”, “How Radio Signals Are Sent and Received”, “Building a Station—The Receiver”, “The Transmitter”, “Power Supply, Keying and Interference Elimination”, “Antennas”, “The Wavemeter—Radio Measurements”, “The A.R.R.L. Communications Department”, “Operating a Station’, “‘The Experimenter’”’. These chapters each occupy from ten to forty pages—indicating that each subject is treated in a thorough manner. In addition there is an appendix containing a fund of useful data. Then there is an index, occupying six pages, by which the valuable information contained in the book is made available. This in a particularly important point and has been compiled and cross-indexed with great care and thought. Altogether the Book contains 256 pages of the most valuable radio information ever found between two covers. The Radio Amateur’s Handbook starts at the beginning and tells what an amateur is, what the League is, what amateur radio is, how to become an amateur, how to learn the code, how to understand what you hear, how to get your licenses, how to build a simple station, how to build a better station, how to operate your station, how the A.R.R.L. works, how to handle traffic, how to conduct experiments and make measurements, and a multitude of other things too numerous to mention. Anyone who is at all interested in the technical side of radio can ill afford to be without The Radio Amateur’s Handbook. Regular Cover $1.00 Postpaid Anywhere Bound in Leather Cloth $2.00 “2.9 > © r eyes ‘ rs ,* ! AMERICAN RADIO RELAY LEAGUE, ae Se § HARTFORD, CONN. Oo oS # Dear Sirs: PS SF 5 ar %, a oy ' Enclosed find my $------ Please send ‘ S$ 2% ! me postpaid (any where in the world) e eo Ng © CP wccnnnsmecs copy of the Handbook. IP re Y Name . (apnnene sere eine onsennoabeee "es ' & 3° DO [T=—*: & ; Addrese, ...ccccccess (tid see aken Cheek $ NOW * . eee teeetoe testes seeeeeteeee kav Say You Saw It In Q S T|— It Identifies You and Helps QS T

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-Martin’s Latest and Greatest Bug THE eat Ne’ WIBROPLEX Reg. Trade Marks: Vibropler, Bug, Lightning Bug No. & The smooth- est, easiest- working bug onthemarket. Not too fast. not too slow— but just Japanned Base $17 right. Works where others Nickel-Plated $19 can’t. | Famous | Improved | Vibroplex | tens of ™ | na f op- : because ease and ‘ tion Japanned Base $17 ~ | ng Nickel-Plated $19 Special Radio Bug pped with Extra Large, Heavy, Specially tructed Contact Poi without relay nts for direct ae get the Genuine Vibroplex. The Vibroplex Name- | r protection. Remit | Cable Address: “‘“VIBR by Money Order or registered THE VIBROPLEX CO., Inc. 825, Brondvey OPLEX” New York 6 Say You Saw It In QST kfzq naa np-4ug nq-2cf ocdj olq perr pts sh sb-law sb-lca sb-lid sb-2ah sb-2bf sb-9aa sb-ptr sy wik wiz wnbt. 2000 to 1000 Miles S. E. N. Y. lagg lalp ibeb Iicgn Ickp lga ino Inq Iqb } 2apd 2ats 2avq 2ayj 2az 2bbe 2bda 2bgz 2bhr 9 2bjh 2bps 2bw 2ccw 2cdm 2crh 2cxl 2ja 2je & 2ps 2ve 2vy 3aal 3afw 3afx 3agb 3ais 3ajh 3bno 3cjw 3dh 3di 3ds 3uz 3vge 4dacv 4acz 4daec 4 4acv 4cj 4ea 4si 4ug 5acl Sain 5awd Sayl 6car § Sagy Sajt Sank Sapn S8axz S8bdf Sbhz 8bkt S8brf & Schp S8ciy 8cmo Sent 8cenz 8ess S8dhe Sdsy &8li %& 9bhz 9cos 9ctg 9fax 9fgp 9eq Ykb Y9gb Ygj Yyy 3 ee-ear28 ef-8btr ef-8wb eg-6nx es-2nak ep-3am # gbr gkt naa ne-2bb nm-if nm-8a ocdj ohk pch pq sb-lid sb-3bf wik wiz wll wnbt wsbs. Cedric Serle, 1 Torrington St., Canterbury, Victoria Australia (20 meters) ladm laep lasf lasu lawe Icki lemx l1fl Iry } lsz 2afx 2ags 2amn 2atx 2awf 2baa 2bcew 2bev 2 2bum 2cuq 2cuz 2gf 2np 2tp 2we 2xad 3aib Sani 38cm 3hf 3ly 4dt 4io 4km 411 4nh 4ob 4px 4to 4 5afb 5Sawd 5bf 5ke 5mx Swz bByb 5Szav 6Galm 6 6awp 6azs 6bau G6Gbax 6bev 6bhq G6by G6cby Gclt & 6esj 6cevy 6dan 6dbo 6dev 6dor 6doa 6jg 6vz 7 7fh 7si 8ane Savp S8axa Sbaf Sbox 8btj Sbto 8cjm & 8dbp S8dhx S8djv 8jq 8xe 9ckp 9dbj 9dku 9drd 9§ 9eq Yez 9sd ne-3cs ne-3fe np-4sa ef-8fd ep-lae eg-2 eg-2hh eg-2xv eg-5by eg-ima eg-5ml eg-5mq eg- ei-lgw ai-2kx ai-2kt as-ra03 gi-6mu. (40 meters) laxa lay laz lbgq lIbhs Imx liw! Iizg 2alu 2am 2evj 2cx!l 2ib 3sm 4fu 4Ik 4oc 4u 4si Sahx ban 5aqy 5auz Sbj 5ke 5ql Swe Sre G6Gagr 6Gakw 6alz 6 6aov 6avy 6awa 6bag 6ben 6bhv G6blp 6bpc 6bzn fd 6cem 6cht 6cut 6dam 6dca G6dhe G6dju 6ea 6ec § Jaax Tiz Sabw S8ahe Saxz 8bq S8dhs 8gz 8pa & Ssh Szg¢ 9aok Yara Yarn Yasc Ybev Sbxb Ycau Yeh 9cix 9ck 9ckf 9ckp 9cmz Ycya Ydg Ydfz Ydga dh S9dng 9Yenp 9ez 9rp YXxi ne-5co eb-4ar eb-4ft ne-l ne-9bz sc-2as sc-2ax ac-lax ac-2ck ac-2al ac-2fi ac-l ac-2ff ac-8na ac-8rj ac-9aa fe-egez fe-ze oo-laj es-2n ef-8fce ef-8fd ef-8xd ef-8cp ef-Sorm ef-8wb eg-6 oh-6adh oh-6alm oh-6avl oh-6boe oh-6bud oh-6b oh-6bqe oh-6bhl] ch-6dtge oh-6xk ai-2bg aq-1lm ci-li = ei-lfb ei-lfp aj-lsk aj-lsm aj-2by aj-3bq aj-4bk aj- aj-4zz od-ljr od-2aj od-3bk od-4as od-6kl fk-3n am-3ab en-0rz en-0fp op-lbd op-lgz op-lem op-! op-Ire ae-lhh as-35ra as-ra03 fo-a3q fo-a7l vs-l oo-bam su-2bt su-loa xnu-6dhg ardi na-wuj. eg-2B0Q, H. E. Bottle, 27 Stormont Rd., Lo S. W. 5, England (Heard during June 1928) labx laep lafd laff lafl laqd laqt lasf lawe Ib lbux lbvl lemx lfs lia ljr lkmp Ilmr 1lmx Inaa le Iry lsz lvw 2acj 2acn 2ahf 2aks 2arb 2arx 2ate 2a 2bee 2bfq 2bkk 2bme 2bmk 2chd 2cx!l 2fu 2mb } Sadm 3aqi 3bq 4aft 4!k S8agq Sagy Sawg Sbaz &d 8enh S8ceqo S8cuq Sdgl Sduw 9ez sa-fc6 sb-law sb-li sb-2ab sb-2at sb-2al sb-2ax sb-2az sc-2ah se se-3cj su-lcex su-lna fe-egez fe-gm fe-les fm-tw ne-lad ne-2be. ezg-6YL, Miss B. Dunn, Stock, Essex, England (40 meters) (Heard during June 1928) lack 2ber 2bhr 2box 2cs 2va &cla 8dgs nb-be3 ne-Se xed-7sch el-lala el-lai3 el-lals el-la2b el-la2g xel-aw em-sbm em-skb ep-lafe ep-lbv ep-lca ep-lcen ep-l" xep-Ims eu-4rb eu-9rb eu-19rb eu-26ra eu-08ra @ 27ra eu-54ra eu-57ra eu-63ra eu-90ra eu-93ra eu-1skt eu-oskw ag-67ra ar-8fbh sa-de3 sb-lah sb-2az. = 2@e Book Reviews | By Harold P. Westman, Technical Editor Practical Television by E. T. Larner with a foreword by John L. Baird, 175 pages, % figures and illustrations published by DP. Van Nostrand Company, Inc., New York City, New York. Price $3.75. : This book is apparently intended for general publis consumption in that it treats the subject in thst fashion commonly referred to as “popular’’. It givé -It Identifies You and Helps QST

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pts sh. b-pt r su iq lab l | 2bhr ja 2je & 8ajh 3 | 4aec 4 | Gear § t Sbrf s sy Sli gi 9yy -~3am e. kK peh Dey bury, fl iry | 2bev 2% » Bani ty x 4to 4 jalm Gay 6elt 6vz Tak 8cjm 9drd 9 lae eg-2 mq eg-by alu 2am ahx 5an 6alz 6 6bzn 6c a Gec § Spa § Jeau 9c) dga 9d ft ne-l -2fi ac-] aj es-2n b eg-§ | oh-6b lm ci-ld bk aj-4 fk-3m m op-lh 1 vs-l Lon awe Ibi naa le fate 2aull 2mb 2y baz Sef w sb-li n se-da fm-tunl ngland 3 ne-Se xel-aw | ep-lw Sra & eu-lsk¥ az. itor | — r with es, 9 by D York public n that t give Jewell and accessories. A.C., and 0-1.5-15 microfarads. "28 YEARS MAKING Radio Test Bench The Jewell pattern No. 580 Radio Test Bench has been designed to provide, interconnected, all the in- struments necessary to completely check the circuits and general working condition of radio receiving sets The testing panel is steel, black enameled, with all markings engraved directly in the steel and filled with white. The panel carries seven instruments, as follows: 0-7.5 volts D.C.; 0-75 volts D.C.; 0-150-300-750 volts D.C.; ptt volt; 0-15-150 D.C. milliamperes; 0-4-8-16 volts A.C.; 800 ohms 0-150-750 volts the panel. A pair of outlets are arranged to be connected to the | | 0-volt, 60 cycle, The panel is supplied with binding posts, so that all instruments can be used individually and with switches to cover all ranges. also supplied with a plug and cord so that all circuits in a radio set can be tested along with the tube, which may be placed in a socket in A.C. line, so that line voltage may be read and a set plugged into the outlets. Line voltage is also used for measuring the capacity of condensers. Our descriptive circular F orm No. 2004 describes this Radio Test Bench in detail. Write for a copy. Jewell Electrical Instrument Co. 1650 Walnut St., Chicago GooonD INSTRUMENTS” NEW SUPER COILS TYPE 19; FOR 20-40-80 m. Receivers, celluloid supported space-wound with N« 15 green s.c. wire plug-in, two coil unit type Plug in antenna coil Extremely efficient ot low r.f. resistance ind small field fype 19—Complete, with mounting ............cseeeeee8 $9.75 pe I19E—Extra coil for broadcast band $2.50 TYPE 15—Especially recommended for the Amateur and Experimenter sume as type 19, except of single coil unit type Range 15-220 m Fine for low power transmitters \ flexible i it ses Ne f ils and «mounting ‘ .2. $6.50 WAVEMETERS! SRL TYPE {60 fG@ange 15-110. “4 of 1% accuracy guaranteed $15.50 Crystal grinding a specialty—Consult SRL for your crys t Out Now—New fall bulletins—Writ« for them They're free SEATTLE RADIO LABORATORY “Builders of Good Radio Equipment” 3335 33rd Ave. So. SEATTLE, WASH. = ~~ = ae ) 7 ol RADIO OPERATORS WANTED THE EASTERN RADIO INSTITUTE can train you quickly and thoroughly because: MODERN AND EFFICIENT METHODS THOROUGH INSTRUCTION under staff of LICENSED COMMERCIAL OPERATORS MODERN APPARATUS including SHORT WAVE TRANSMITTER FIFTEEN years a RADIO SCHOOL THE OLDEST, LARGEST and MOST SUCCESSFUL school in New Se BY THE A .R. BR. tp Day or Evening Classes Start Every Monday. SPECIAL CODE CLASSES Write for Illustrated Prospectus EASTERN RADIO INSTITUTE 899 BOYLSTON STREET BOSTON, MASS. Say You Saw It In Q S T It Identifies You and Helps Q S T Raytheon = Kino-lamp = As Pioneers in TELEVISION We invite correspondence from amateurs in regard to these new Raytheon Products, which are being used successfully in the Television broadcasting. Kino-Lamp — the first Television Tube developed to work on all systems. Foto-Cell — made in both hard vacuum and gas-filled extra sensitive types. RAYTHEON MEG. CO. Kendall Square Building CAMBRIDGE, MASS.

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Say You Saw It In QS T—lIt Identifies You and Helps QST a brief history of some of the many systems that have been devised for television, pointing out the principal manner in which they differ from each other. The more important difficulties confronting the experimenter and some of the methods evolved for their solution are also discussed. Elementary ex- planations of seleneum and photo-electric cells as well as of the cathode ray tube are given. A generous portion of the book has been devoted to the methods of Baird including descriptions of his ‘‘Noctovisor” and “Phonovisor”. Picture transmission is treated but incidently, the author devoting practically all his space to television, that is, seeing at a distance, It is an interesting book through which the un- initiated may make his acquaintance with the subject in a not too technical manner. Bible Dramas by William Ford Manley, 225 pages, published by Fleming H. Revell Company of New York City, New York. There is but slight or no connection in the minds of most between radio and the Bible. It might, therefore, not be amiss to say that the reason for this review is that this series of Bible Dramas is published by arrangement with the National Broad- casting Company and covers a dozen stories prepared in such a manner as to make them suitable for radio presentation as well as for church or theatrical use. The material has been so prepared that each story is complete in itself and although written primarily for radio presentation, makes interesting reading. It seems almost foolish to speak further concerning these when it is possible to get a vastly better and more accurate impression by listening in to one of the Bible Dramas as broadcast on Sunday nights over the N. B. C. Network of stations. Storage Batteries Simplified by Victor W. Page, new revised edition, 258 pages, 112 figures, published by the Norman W. Henley Publishing Company of New York City, New York. Price $2.00. This book is not an advanced work on storage batteries but rather, a simplified version as the title suggests. It is apparently aimed at the garage man whose knowledge of electrical equipment and theory is meagre and whose radio knowledge is a negative quantity. The author has drawn profusely upon the installation and operating instructions supplied by various storage battery manufacturers. It should have but little appeal to the radio man and perhaps the second sentence in this paragraph goes further towards describing the book than do all the rest. Standard Time Conversion Chart. Perhaps many remember the “Time Slide Rule” de- scribed on page 42 of the September, 1927 issue of QST. This chart is very similar, though in some- what more detail. The circle indicating geographical locations is divided up to show every 7.5 degrees and the names of the principal countries through which these meridians pass is given. The time is shown from midnight to noon to midnight with the hours running from 1 to 12 rather than from 1 to 24. This may cause some inconvenience but is easily corrected and so should not be very damaging. It is called, Miscellaneous Publication No, 84 and may be obtained from the Superintendent of Documents, Government Printing Office, Washington, D. C. for 10 cents. No stamps or uncertified checks are ac- cepted. Conversion chart. (Kilocycles to meters or vice-versa.) At this time when we are endeavoring to think and speak in kilocycles rather than meters, it is of utmost importance that we have some means of making this conversion with the least amount of effort. The Radio Division of the Department of Commerce, under whose jurisdiction the amateur is, are using the factor of 300,000 kilocycles per second in their conver- sions and this value will accordingly be used by QST. The Radio Division has had charts prepared covering values of from 10 to 29,990 in steps of 10 (the units may be either meters or kilocycles) and these may be obtained from the Superintendent of Documents, Government Printing Office, Washington, D. C. for 5 cents each. No stamps or uncertified checks are accepted.

Br abs les: 200 sis' spt $4.

Viti

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ject ley, yell nds rht, for ad- red dio se. ory ‘ily se re he he absolutely noise- less and stepless, 2000 to 30,000 ohm re- sistance. List $5, special $2.95. $4. Bradleystat No Special et Bradley Leak, 2.95 E-210 1.60 Signal Buzzer Set Code on Baseboard Belden braid % inch wide, ft. international $2.45 $7. Acme B-6—*‘B”’ elimina- tor transformer, 235 v. each side of centre tap 2.45 Acme 500 w. plate trans- former 1000-1500-2000 each side of centre tap, 24.00. Acme B.H.-1 transformer, 255-510 each side of centre tap; also 2 fil. windings of 4 v. each side of centre tap, $10.25 Acme C.W. 30 Henry choke, $18 list 150 M. A. single $14.40; also other sizes at special prices. ‘ 45 VESEY STREET NEW YORK New York’s Headquarters Transmitting Apparatus When in Town Visit Our Store Full Line of Acme -- Thordarson -- Jewell -- Flech- theim -- General Radio -- Signal -- Bradley SPECIALS for Dubilier Mica Condenser .002 cap. 6,000 working volt 1.95 General Radio 247D .001 cond. plain or with vernier 1.75 Dubilier cond. 1.7 mfd. 1,000v D.C. test; 650v. working voltage 1.35 Dubilier cond. .5 mfd. 1,000v D.C. working voltage -B5 R.C.A.—U.V. 1716 Super Het. transformer 1.45 Ward Leonard Resistances; fits standard base receptacles; sizes 300—600—900—1200 and 2000 ohms 95 $15. Imported German head sets; very sensitive 3.45 Honeycomb Coils unmounted, all sizes in stock at % price. $8 Signal Corp adjustable arm micro-transmitter for panel mounting 2.45 $9. Dubilier condenser, 4mfd; 600 v. D. C. working type 903; limited quantity 2.25 R.E.L. Transmitting Inductances,per set, 8.80 Bristol 50 Henry choke 2.75 6.50 Acme .0005 enclosed condenser -95 Neon Glow Lamps, made Flechtheim Condensers, by General Electric Co., all types 35% off list type G.10, standard base densers, double spaced fortrans- mitting, .00025 cap. No. 12 Enameled copper wire, any length, ft. $ No. 10 Enameled copper wire, any length, ft. Genuine Bakelite Panel 10xl4x\%& Cardwell con- 3.45 Baiawin phones type C, pair 5.95 Myers $5 4% volt Det. or Amp tube, complete with mounting clips eeccccce o Ward Leonard Resistance $4.75 list-6% inch long—800- 1000 -1200 -3000 -6000 -8000- 11000 ohms; can be used for 2-50 watt tubes or less, $1.48 101 uses, as illustrated in QST May issue page Pyrex Low-loss V.T. i steseeawes cove ae sockets, each 39c. MAIL ORDERS FILLED SAME DAY 10% Must Accompany All Orders Television disks as in QST special $1.9 General Radio No. 358 Short Wave Meter, 14 to 225 meters, list $22, special $14.50. specified >. RADIO IN BRASIL When in Brasil, apply to M. BARROS & CIA for anything you need in connection with radio. M. BARROS & CIA 70 sob. Rua S. José 70 sob. Postal Box 89 Rio de Janeiro to 25 per in few evenings. pass exam quickly. them by 75 or confusion. Either code DODGE RADIO SHORTKUT With Appendix and Hints for Better Key Work. Fixes Signals in mind to stick—Kills Hesitation, Cultivates Speed and Good Fist—Produces Results. Slow Hams raise speed Previous Failures qualify and Beginners master code and pass in ten days. DODGE HIGH SPEED METHOD (Intensive Speed Practice) Quickly puts 25 per Hams in 35-40 per class. Five Hams report made this gain in few evenings. One of minutes total practice only. DODGE MORSE SHORTKUT Easily mastered by Radio Ops—Kills tendency to mixup used as desired. REPORTS FROM USERS ° ° . Tell th c let story—Mailed on _ request. Radio Telegraph address, Radioparte, Rio de Janeiro $3 50 High oy $2.50. Morse $2.50. Monay order. . = P None C. O. D. Foreign add 50 cents See our amad. Branch: Avenida S. Joao 4, S. Paulo, Brasil G. K. DeDeE, MAMARONECK. NEW YORK. 780 pp. Fleet) S. S. Robison. Eighth Edition Just Off the Press U.S. Navy, now Director of Naval Communications, Robison’s Manual of Radio Telegraphy and Telephony Completely Revised in June, 1928, and Up-to-Date. Of the 6th edition of this book reviewed by QST it was said this is perhaps “The Best Radio Book That Ever Came to This Desk” The standard Navy book on radio originally prepared in 1907 by Lieutenant (later Admiral and C-in-C of U.S. The present edition revised by Captain S. C. Hooper, Price $4.00 postpaid. 6th edition sold for $8.00; 7th edition sold for $5.50 Address: Secretary-Treasurer, U.S. Naval Institute, Annapolis, Md., U.S.A. Say You Saw It In Q S T — It Identifies You and Helps Q S T

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Consulting Engineers Short Wave mitting Apparatus Fon and Trans- We can furnish you with any type of Radio Experimental Apparatus you I ight require. Communicate with us for further information. EGGERT SALES COMPANY 179 Greenwich St., N. Y. City

Short Wave Converter Unit Complete $99.50 Special

Some of the best entertain- ment of the air is bros t on the short waves by many power- ful There is no longer any reason why all t receive these excellent programs fron er the world. The Dresner Short Wa ter Unit is completely assembled. It eff covers a wave band of 15 to 550 met makes reception easily obtainable for lat the special price of $22.50 compl ady to plug into your receiverina few second ir dealer cannot supply youSEND MONEY ORDER DIRECT and we will ship P. P. } GUARANTEED. DRESNER RADIO MFG. CORP. 644 Southern Boulevard, New York City

xO) Say You Saw It In QST Financial Statement Y order of the Board of Directors the following statement of the income and disbursements of the American Radio Relay League for the second quarter of 1928 is published for the information of the membership. K. B. WARNER, Secretary. STATEMENT OF REVENUE AND EXPENSES FOR THE THREE MONTHS ENDED JUNE 30, 1928. REVENUE $ 14,810.09 Advertising sales, Newsdealer sales, QST Handbook sales ............ Handbook advertising sales .. Dues and subscriptions Back numbers, etc. Emblems Interest Cash QST earned discount earned Deduct: Returns and DO ax paceeninuas Less portion charged to reserve for news- stand returns allow- $4,309.27 1,306.51

Discount 2% for cash ....... Exchange and collection charges Net Revenue .............. EXPENSE Publication expenses QST .. Publication expenses, Hand- DE dcktiwbebeadanckcaawan EE Spee ee ee Forwarding expenses senwes Telegraph, telephone and post- 2 a <icatbbbansasdens eee Office supplies and _ general CE wachineicccdiaveca Rent, light and heat .... Traveling expenses Depreciation equipment of furniture and Bad debts written off ...... Communications Dept. field ex- DOEMBEB ccccsccccccscccceses Total Expenses Net Gain from Operations eee 9,906.36 3,464.26 1,305.00 3,002.76 272.74 16.45 —E

11,124.47 1,521.99 14,056.25 565.24 1,066.91 1,660.93 927.50 1,728.72 493.56 62.14 71.30

$ 39,182.26 3,291.95 35,890.31 33,279.01

$ 2,611.30 Indiana Central Division Convention ES Sir! The Hoosier boys know how Ye run conventions and the Indian- apolis Radio Club, who sponsored this year’s affair which was held on July 28-29, more than kept up the reputation. Beginning early Saturday morning dele- gates began arriving from different parts of the state and the register showed several from neighboring states. The forenoon was spent in getting acquainted and by the was ready to open every one was on a friendly basis. Promptly at 2 o’clock, Director Darr called the convention to order and welcomed the time the afternoon session guests. Then followed some really good informative addresses by F. R. Finehout, 9CLO, on crystal grinding and with prac- tical demonstration. D. J. Angus, the SCM, 9CYQ, understands crystal circuits It Identifies You and Helps QS T

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of FOR 8. ITROHM Transmitting Grid Leaks and Rheostats now cover the V entire line of transmitting tube circuits. ‘The prices on these amateur products are reduced materially. {Your dealer should stock Vitrohm Transmitting Products. If you have difficulty in obtaining them, write us direct. fATALOGUE— PEeean Emme wi euneER ____ PRODUCT —__RESISTANCE _ DISSIPATION _ CURRENT ___ RATING _ PRICE 507- Grid Leak* 5000 ohms 44 watts 90 m.a. 100 watts $2.00 507-3 3. GridLeak*® | 5000ohms 200watts 200m.a. — 1000 watts 2.80 507- + “Grid Leakt 50,000 ohms ~—200 watts 60 ma. 1000 watts 6.50 507-5 Grid Leakt —-20,000ohms = 200watts 100ma.a. 1000 watts 4.25 507-51 Grid Leak* ———10,000ohms = 200 watts 135 ma. 1000 watts . 4.00 507-66 Grid Leak** 15,000 ohms 200watts 120m.a. 1000 watts 6.00 507-63 Rheostatt* 50ohms 50 watts lamp. 5.50 507-59. ~=Rheostat*t 20 ohms 80 watts 2 amp. 5.50 507-83. Rheostat*t — 12.5 ohms 60watts 2.2 amp. 5.50 *Centertapped 2 —*S Steps at 5M—10M—15M + DeForest P or R. C. A. 852 Tube for R. C. A. 852 or DeForest P Tube De Forest H Tube +* For Primary Control *{ Filament and Primary Control Ward Leonard(tectric Company 37-41 South Street Mount Vernon, N. Y. RADIO SCHOOL | | suiers stn an ear Earn $35 to $50 Per Week stage, has now advanced sufficiently The rapid expansion of RADIO has created to enable amateurs to build outfits many new positions on land and sea. En- that will give edifying results. roll now. New term begins September _ ‘ , 10th in both day and evening class. Send My rite today for our price list of for free catalogue. television apparatus. MASS. RADIO SC HOOL Photo Electric Devices, Inc. 18 Boylston Street, Boston Tel. Hancock 8184 Established 1905 594 Fifth Avenue Brooklyn, N. Y. Q@ST OSCILLATING CRYSTALS AMATEUR BANDS WE WISH TO ANNOUNCE: lst.—That now, our crystals are capable of being used with as high a power tube as the 50 watt size. 2nd.—That we do not claim to grind the CHEAPEST crystals, but we do claim to grind only the best which is the cheapest in the long run. $rd.—That we will ship the closest frequency crystal we have to your desired frequency, and that the frequency of the crystal will be stated ACCURATE to BETTER THAN A TENTH of 1%. ith.—That all crystals are absolutely guaranteed in regard to output and frequency, and immediate shipment can be made on crystals in the amateur bands. Prices for grinding POWER CRYSTALS to oscillate in the various amateur bands are as follows: 1715 to 2000 Kilocycles $15.00 Note: The above prices are effective July 1st, 1928, to be in effect 3500 to 4000 Kilocycles $25.00 until November Ist, 1928. (Add $10.00 to these prices if crys- 7000 to 7300 Kilocycles $40.00 tal is to be mounted in an excellent dust-proof power mounting.) Broadcast Band——We will grind a crystal for you accurate to plus or minus 500 cycles of your assigned fre- quency for $45.00 unmounted, $55.00 mounted. Two day shipment and all crystals guaranteed. Crystals ground to any frequency between 40 and 10,000 Kilocycles. We will be pleased to quote prices on your particular requirement. SCIENTIFIC RADIO SERVICE, “The Crystal Specialists’ P. O. Box 86, Dept. ZA Mount Rainier, Maryland - It Identifies You and Helps Q S T Say You Saw It InQ ST

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New Tone Brilliancy , Potter Condenser Block in your Power Amplifier. Rich, natural bass tones that possess a real thrill. with No. T2950 where two 250 Type Power Tubes are used $22.50 Highly Efficient—Long Life Che Choice of Leading Radio Engineers sy our dealer for full information POTTER MFG. CO. North Chicago, Illinois Besi Advanced snners/ Students! The TELEPLEXCode Sender will make you proficient in code prac- tice—both sending and receiving, in half the usual time. This is the only instrument that Reproduces ac- tual sending of expert operaters. Sends mes- sages, radiograms,etc. — regular code traffic at any desired sfeed. Endorsed by U.S Navy and leading Technical and Tele- graph Schools. Com- plete Set of Instruc- tion Tapes( Wireless or Morse) for begin- ners and vanced students furnished with the Tele- lex. Remem- r, only the Teleplex pro- vides practice when, where and how you want it. Write for booklet RL. Silent Teleplex Co., 76 Cortlandt St., New York, N.Y. ey, THE BEST $1 You EVER am— ny 5 ee ¢ & se # ¥ ave u ordered ur copy-of andy’s © | ri see andy : andbook.§ Say You Saw It In QS T — It Identifies You and Helps QST and showed the gang what he could do with that small xtal-control portable set. H. F. Weakley of the Esterline-Angus Co. gave a good talk on Radio Instruments. C. E. Dutton of the A. T. & T. gave us a new angle on chain broadcasting and made us realize the advance which has been made in that particular field of radio. The most interesting lecture of the two-day sessions was that given by R. J. Kryter of the Presto-Lite- Battery Co. The subject of Rectifiers and Filters was handled in a masterly way. A. A. Hebert, Treasurer- Fieldman, from A.R.R.L. Headquarters, discussed the 1929 problems with which we amateurs will be faced, and told us what was being done by Headquarters to help relieve the situation. Former Division Manager R. H. G. Mathews, Lt-Commander, U.S.N.R., brought a naval personnel with him, and en- rolled 22 of the delegates present into the Naval Reserve. Matty is certainly a worker and if he continues the same pace he will have the best Unit in the service. When we speak of Banquets we always think of those night affairs which are scheduled for 7 o’clock in the evening and let every one starve until 8 o’clock, but this banquet was another departure from the conventional—it was held in the after- noon; a real Sunday afternoon dinner. There were so many nice things that took place that space prevents mentioning every- thing, but we will say that the good prizes donated by the manufacturers had to be won. The closing of the affair took place shortly after the dinner but not before OM Burns had had a chance to regale us with his entertainers—they were good too—and we now know he has an eye for pulchri- tude. —A. A. H. The New England Division Convention Held at Augusta, Maine. HE Maine A.R.R.L. Convention held at Augusta, July 13 and 14 was ac- claimed by those who attended the big- gest and best affair of the kind ever held in the Section. The Convention Committee secured the full codperation of many state and local agencies in “putting it over”. Chairman L.A. Burleigh Jr. (1KE), Sec- retary Fred Best (1BIG) and Leslie Hall were responsible for the fine arrangements. For those who drove from all parts of New England and New York large banners and signs pointed the way to Ham Headquar- ters at the Augusta Y.M.C.A. and bid the delegates welcome. The opening sessions were held in the Senate Chamber at the State Capitol. Aft- er the address of welcome by Mayor Mc- ch \ ie ws “ 7s ae. ene The Fe § 5 F thes

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Se were (6S 225 South St. Synchronous Motors for Television In addition to building reliable and satisfactory motor generators, “Esco” has had many years of experience in building electric motors for a great variety of applications. Synchronous motors, small, compact, reliable, self starting are now offered for Television equip- ment. tation, are quiet running and fully guaranteed. Other types of motors suitable for Television may also be supplied. Write us about your requirements. ELECTRIC SPECIALTY CO. Trade “ESCO” Mark They require no direct current for exci- Stamford, Conn: 4th Edition—Just Off Press “Radio Theory and Operating” By Mary Texanna Loomis The standard radio text and reference book of America. Near goo pages, over 700 illus- trations, flexible binding. PRICE $3.50—Postage Paid For sale by hundreds of bookdealers throughout America and many foreign countries. Or may be pur- chased direct from the publishers. Send check or money order to LOOMIS PUBLISHING COMPANY Dept. 5 Washington, D. C. YARRE Ad, ~pprovee oP RODUCe Special Switches There are almost limitless possibilities for different spring arrangements with Yaxley switches. Write for prices on special switches, giving as much information as possible, together with sketch of spring arrangement wanted and of panel. YAXLEY MFG. CO. 8 So. Clinton St. Chicago Say You Saw It In Q S T — It Identifies You and Helps Q S T Centralab Giant Power Rheostat Small in diameter but large in capacity, this rheostat will safely carry any power load of 70 watts. Con- structed of heat-proof materials throughout. No fibre to warp or burn out. Wire is wound on a steel core insulated with as- bestos. Extra wide core assures large area for quick heat dissipation. This unit is ideal for primary control of “AC” receivers or It will keep the line at a constant “A” Power Units. workable average, keeping the secondary output well within rated limits. These units connected in series across the output of a Rectifier and Filter system for “B” Power will provide all necessary voltage taps. These units can be used in any power circuit position without any danger of burning out—the capacity is only limited by the capacity of the wire. Manufactured with either two or three terminals. Diameter 2”; Depth 14”. Write for new Booklet on “Volume Controls and Voltage Controls—their Use.” CENTRAL RADIO LABORATORIES 20 Keefe Avenue Milwaukee, Wis. T][[Centzataby |]

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FROST |AD00 FROST RADIO FROST-RADIO FROST-RADIO FROST- | FROST-RADIO | New Data Book Now Ready ew Frost-Radio 16 page Data B ist off the press, is ready for ng. It contains a great deal of e information regarding cir- t also technical data on rheo- riable high resistances, filter rs, etc. We have aimed to his a complete authoritative * interest to every reader of Write for your copy today, in- 10e to cover cost of postage ling. Also contains full in- on the new Frost-Radio 1928. HERBERT H. FROST, INC. Main Office and Factory Elkhert, Indiana New York City see ae oe = eee 8 8 8 8 Oe Ue Ue Ue GE UG UG UG UG UG UG UG UG H. FROST, Ine La Saile Street, Chieago return mail your NEW 16-page Data Boo’ FROST-RADIO FROST-RADIO FROST-RADIO FROST-RADIO FROST- RADIO FROST-RADIO FROST: RADIO fResT-gante (REST QARlD [ROST-QantD GunSr The Short Wave Set That Backs Its Claim TY! P’’ S. W. Receiver—portable—embody- ing all the latest developments in H. I ‘ Compact, quality job — size 6 in. x 9 in. Ca il on permanent or portable installations. esults on either S. W. broadcasting or Finest grade material throughout, latest type small ss coils. 3 plug-in KIT overing 15 to 115 tandard UX 201A $3 2.50 TYPE B.L.4 ‘gh gonde® ww. Receiver for either * S.W.Broadcasting or Code reception. Sa fel ‘P’’, designed specially y+ for per- rT ullation, Drum dials. Bot e receivers will give fir receiving American $2.00 sta foreign countries . » have these sets aouaiiied tested, operate, enclose $7.60 extra to cover LOW WAVE LABORATORIES 37 Barclay St. New York City Ne manufacture complete line of transmitting appatatus ME ENCLOSE STAMP FOR CATALOG R4 Say You Saw It In QST Lean, the traffic session was conducted by S.C.M. Best and the C.M. from A.R.R.L. Headquarters. Code contests were next held for groups of novices, amateurs, and commercials. The crowd adjourned to the “Y” for a buffet lunch. Stunt night in the “Y” gym was under the capable direction of Physical Director Mahan. Everyone got acquainted and had a good time. Prizes were awarded those who excelled in the different contests. From the “Y” the gang went to the Central Maine Power Co. Audi- torium for a dance and jamboree under the auspices of the C.M.P. Co. Girls Club. Saturday morning a sight-seeing tour was the chief feature of interest. In the afternoon the Technical Session was held in the C.M.P. Co. auditorium. L.C. Brown of 1AQD demonstrated his ten-meter equip- ment in a very interesting way. L. B. Root of General Radio discoursed on crystal con- trol. F.E. Handy exhibited a portable re- ceiver and mentioned some of the consid- erations in its design. The 125 delegates assembled at the Augusta House for the big banquet which was broadcast through WCSH of Portland. “The Song of the Short-wave Ham” written by 1KE featur- ing T.O.M., the Wouff Hong and Retty- snitch was sung, broadcast, and placed on sale following the convention. A silver cup donated by W.J. Lee, 1BCY-4XE-NRRG, as a Naval Reserve award for the individual amateur and reservist in Maine, N.H., Vt., and Mass. for achievement in the past year was awarded to Evans of 10C-1BFT with appropriate remarks. This identical cup will be awarded and engraved annually. After other prize awards and speeches by Hon. Wm.R. Pattangall, L.B.Root, F. E. Handy, Ralph Given of the C.M.P.Co. and A.A.Hebert, A.R.R.L. Treasurer-Field Man had been broadcast, the wire to Portland was opened. The remainder of the evening was spent in hamfesting and perusing three reels of movies sent up from Hartford, During the convention a special ladies program was provided for those not inter- ested in the technical sessions. A local drug store provided free soft drinks for the thirsty delegates. An amateur station in operation during the convention was much in evidence as a window display. Those in attendance were able to attend moving pic- tures at the Colonial Theater free at any time by showing their badges. Movies of the convention sessions and stunts taken by the Portland Press Herald were shown throughout the state during the next week as a special feature. Daily Reports of convention doings in the Kennebec Jour- nal were of interest to the delegates. Bids for the next annual convention were made by representatives of Portland and Bangor and the Queen City Radio Club of the lat- ter city is already working on plans for next year. —F..E.H. It Identifies You and Helps QST \| th jig & im

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d by ~R.L. next and » the n the ction e got rizes the rang Ludi- * the tour the held ‘own juip- Root con- re- \sid- ates the ugh the tur- tty- on cup RG, lual Vt., ear vith cup lly. by E. and [an ind ing ree ‘ies er- ug the in +4 | PATENTS The new Air-King Short Wave Kit con- sists of three plug-in coils, ranging from 15 to 130 meters (when tuned with a .00014 mfd. condenser), and a plug-in base, with variable primary, which is soldered with phosphor bronze flexible connections to per- manent antenna-ground binding posts on the base. Each coil is accurately space-wound 216-WALL ABOUT ST. PRECISION -* SHORT WAVE PLUG-IN KIT ~ DIELECTRIC GENUINE ; BAKELITE / PENDING on a bakelite squirrel cage form, with ribs threaded to lock each turn in place. Friction holds the variable primary in any position it is put in. Double contact between coil prongs and the jacks in the base.assure perfect connection at all times, from the moment of inserting coils. Send for free booklet on hook-ups and descriptions of coils. If Your Dealer Can’t Supply You,,Order Direct Mro. by AIR-KING PRODUCTS Co. BROOKLYN,N.Y.,U.S.A. QUARTZ OSCILLATING (CRYSTALS i] lin. sections ground ny 14 alee An = frequency at these prices: OO- TE MOIETS ncccccccccoscesece $25.00 75-100 meters .....ccccsseseess 17 50 100-200 meters ......eeeeeeceeee 10.00 200-600 meters .....eeceecnevees 15.00 Tested blanks, 2 to 5 mm thick .. ».00 Sections of any practicable dimensions made to order. Prompt Delivery 4. T. Roone 31 Calumet Bidg., Buffalo, N. Y. Ad Li; Crystallographic experience clHIDE OHM ISUPER-DAVO ’ (ACTUALSIZE) 500 to 5,000,000 ohms Gemibated 7 acity and inductance practically negligibie. The most accurate cient resistance unit known to io. /rite for booklet B. DAVEN ‘CORPORATION NEWARK, N. J. BECOME A RADIO OPERATOR See the World. Earn a Good Income. Duties Light and Fascinating. LEARN IN THE SECOND PORT U.S.A. Radio Inspector located here. New Orleans supplies opera- tors for the various Gulf ports Most logical location in the U.S.A. to come to for training. Nearly 100% of radio operators graduating on the Gulf during the past six years trained by Mr. Clemmons, Supervisor of Instruction Start training now for fall runs. Member of the A.R.R.L.—€all “5 G R” Day and Night Classes—Enroll anytime cular GULF RADIO SCHOOL 844 Howard Ave. New Orleans, La. Write for cir- SUPERIOR Dear OM: FLECHTHEIM (F) ER CONDENS designing and eanting that new power pack you’ve had in mind. Flechtheim Superior TYPE F14- for 172 Power Pack-450 D. C. FLECHTHEIM You will soon be busy again at work on your transmitter, or ondensers have created an enviable name for themselves, for they are dependable and at the same time very reasonably priced. Complete line of By-pass, Filter, High Voltage, Transmitting and special condenser blocks for the 171,210 and 250 power amplifier tubes. Write for catalog X Tnx, OM es pse QSL. Complete Line From 250 to 3000 V. D.C. A. M. FLECHTHEIM & CO., Inc., Dept. QT, 136 Liberty St., N. Y. C. FEC wT MEIN High CONDENSERS: 73’s nu 2AFS, Chief Engineer. TYPE H200-650 D.C. Say You Saw It In Q S T — It Identifies You and Helps Q S T 85

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_ TELEVISION LAROSTAT has pioneered in super- B-eliminators, socket-power re- zality amplification, so is it ready elevision. CLAROSTAT, with stance fitted to the exact needs, ; the ultra-critical requirements f chnique. It is for you to ask for \ROS T AT engineering cooperation. M cal of what CLAROSTAT can f< eee Bg

Neon Lamp Control ard CLAROSTAT is indispensable ng a critical voltage on the neon desired contrast between light and A satisfactory image, with suf- f r ail, depends on proper direct-cur- for normal glow, yet low enough t of ample contrast with increased i » signal modulation. Sc anning Disk Control of receiving and transmitting btained by means of special 100-watt rating). A push-button tance for momentary speeding up of proper step with transmitter. This tandard practice in most television r our literature and for any special data CLAROSTAT MFG. CO., Inc. 5 rth 6th St., STA r Y

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Say You Saw It In QST-

The Zepp (Continued from Page 36) quency by the amount X, which has the effect of shifting the voltage antinode V. from a point directly opposite V; along the wire away from the point directly opposite V; by the same amount X. In order to maintain the whole system in resonance with the desired frequency it is necessary to so adjust the feeder tuning as to in ef- fect reduce the length of the feeder system by the amount Y. The current and voltage distribution in the two feeder wires is no longer symmetrical, and the two radio fre- quency ammeters A-A will not indicate equal values of current. We _ therefore shorten the length of the antenna by the amount X, and retune the feeder input cir- cuit until the system is again in resonance. The two meters will now indicate approxi- mately equal values of current, and the voltage and current distribution will be proper as shown in A. There should be a current antinode (voltage node) at the center of the an- tenna inductance when the condition shown in A of Figure 6 prevails and this may be checked by touching the center turn with a neon lamp or point of a wooden-handled screw driver. There should be no glow from the lamp or spark from the screw driver. In the actual process of adjustment, the antenna inductance and tuning condenser arrangement is connected to the input end of the feeders, as shown in Figure 7. The two ammeters are located equal distances from the top end of the feeder system, which also makes the distance from the antenna inductance and condensers to each meter equal. Therefore, when the current as indicated by the two meters is the same, there will be the proper distribution of voltage and current in the feeders and an- tenna. The length of the antenna, which we made a full % wavelength long in the first place, is cut off by about six inches at a cut until the difference in current as in- dicated by the two meters is not more than about ten percent. It should be remembered that the current as indicated by the meters may not be, and very probably is not, the maximum current in the feeders. The maxi- mum current would only be indicated when the meters were located at current antin- odes, which is not likely to occur in many cases. The importance of the readings of the two meters is not how much current they indicate, but the ratio of the currents at these two points opposite each other on the feeder system. If the distribution is perfectly symmetrical this ratio will be one to one, or both meters will read the same. The screw driver or neon lamp test on the center of the antenna inductance should indicate zero voltage at that point when the two meters indicate equal cur- rent, as mentioned above. Figure 7 shows a suggested arrangement of the input end of the feeder system for -It Identifies You and Helps QST

Fe. ||

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the V: the site to ince ary ef- tem age no fre- ‘ate ore the tir- ce, »xi- the be ode an- wn be ith led ow ew he ser nd he es m, he ch nt @c) UNI-RECTRON POWER AMPLIFIER @) (IDEAL FOR USE WITH DYNAMIC SPEAKERS) As the Uni-Rectron stands it is a super power amplifier, which ean be used in connection with any radio set and loud speaker. Binding posts are provided for input to the Uni-Rectron and output to the speaker. Requires no batteries for its operation. It obtains its power from the 110 Volt, 60 Cycle alternating cur- rent lighting circuit of your house. The UX-210 super power am- plyfying tube and the UX-216B or 281 rectifying tube are used with this amplifier, which can- not overload. From the faintest MODEL AP-935 LIST PRICE $88.50 (Without Tubes) Special *19: 75 Power EA Transmitting purposes ever of- whisper to the loudest crash of sound—R.C.A. Uni-Rectron am- plifies each note at its true value. High and low notes are all treated alike The volume and quality deliv- ered will be a revelation. Also by removing the input and output transformers it can be used as a source of power for an oscillating or transmitting tube, furnishing power for all circuits, grid, plate and filament and is the cheapest form of Supply for Amateur fered. New. SEND FOR OUR LISTS OF RADIO BARGAINS AMERICAN SALES CO., 19-21 Warren St., New York City NATIONAL Velvet Vernier Dial type N for short wave work. A solid German Silver Dial with the original Velvet Vernier mechanism and a real vernier for close reading to one tenth divi- sion. Price $6.50. Send for Short Wave Bulletin NATIONAL Co. INC., W. A. READY, PRES. MALDEN, Mass. resistors and condensers that are Built Better — to endure. Write for The Research Worker. A free monthly publication. AEROVOX WIRELESS CORPORATION 68 Washington Street Brooklyn, N. Y. To Our Readers who are not A. R. R. L. members Wouldn't you like to become a member of the American Radio Relay League? We need you in this big organization of radio amateurs, the only amateur association that does things. From your reading of OST you have gained a knowledge of the ‘nature of the League and what it does, and you have read its purposes as set forth on page 6 of every issue. We would like to have you become a full-fledged member and add your strength to ours in the things we are undertaking for Amateur Radio. You will have the membership edition of OST delivered at your door each month. A con- venient application form is printed below—clip it out and mail it today. A bona fide interest in radio is the only essential qualification for membership. American Radio Relay League, Hartford, Conn., U. 5S. A. I hereby apply for membership in the American Radio Relay League, and en- close $2.50 ($3 in foreign countries) in payment of one year’s dues. This entitles me to s f - - receive OST for the same period. issue. address. Please begin my subscription with the .........csssssesses Mail my Certificate of Membership and send QST to the following name and Do you know a friend who is also interested in Amateur Radio, whose name you might give us so we may send him a sample copy of OST? eprrererererrrrrrrerererrrrrrrrrrirrrr rrr rt ttt t tt ttt ttt tt tre Thanks Say You Saw It In Q S T — It Identifies You and Helps Q S T

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— QST nu9FO — CALL BOOK Published March, June, September, December Single Copies U.S. and Canada $1.00 Each (Foreign $1.10) Subscription ONE YEAR (4 Issues) For $3.25 (Foreign $3.50) Amateur, Land and Ship Stations From 83 Countries Radio Amateur Call Book Inc. 508 So. Dearborn St., Chicago, U. S. A. New Hook-ups. This yok shows how to make Short Wave Re- eivers and Short Wave Adapters. How to use the new screen grid ’ tube in D. C. and A. C. White - Cireuits. How to build fer it! Power Amplifiers, and ABC Eliminators. Up to the minute information on all new radio develop- ments. Set Builders, Fans, Dealers, end for it today. KARAS ELECTRIC COMPANY 4030J1-N. Rockwell St., Chicago, Ill. Please send me your free book You can easily become an EXPERT Radio Operator Through The Candler System Course of Training in High Speed Telegraphing Theo. McElroy, World’s Champion Radio Oper- ator ' no other system. He writes: “At th nt of Progress, Chicago, I copied 56 w r minute for 5 minutes, establishing a record. I owe my skill, speed and steac nerve to The Candler System.” What tl m has done for McElroy and over 40,000 t will do fer you. new radio FREE booklet explains Send for it TO-DAY. A postcard Im CANDLER SYSTEM CO. Dept R 6343 S. Kedzie Ave. Chicago, Ills. Say You Saw It In QS T—lIt Identifies You and Helps QST the amateur station where quick QSY with a minimum of time and effort is desired. The connections between the antenna in- ductance and parallel tuning condenser should be “low loss” and with plenty of cross section to carry the tank current. The parallel tuning condenser should be @/Ne, FIG. 7 capable of carrying the tank current with- out heating and should have a voltage rat- ing approximately the same as that of the plate circuit tuning condenser of the trans- mitter. Its capacity may be around 250 uufd. The series condensers may have a lower voltage rating but should be of the same quality, their capacity being also about 250 uufd. maximum. L is the usual antenna inductance of about 5 to 10 turns. When the parallel tuning arrangement is being used, the two series condensers are set at maximum, and when the series tun- ing arrangement is being used, the parallel condenser is set at zero. : pS trays"$s Zero LB suggests that the cover designs by 8ZZ should be signed something like this: Darr! Darr! Darr did it Darr! Darr did it Darr! Darr did it That General Radio plugs will screw into Sangamo fixed condensers is a point that should be of interest to anyone who wants to use plug-in condensers for any purpose. —IMJ ADAM! COME AWAN FROM THAT RAVIO THE FIRST WOMAN TO DISAPPROVE OF RADIO AS A HOGBY An ome Sate

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y of rent. be ith- rat- the ins- 250 to at ts Ls C Protection at Last Circuit Breaker or Plate Overload Relay “Those Precious Bottles’ — Secondaries of Hizh Voltage Transtormers, Choke Coils, Ete. ot All can be protected from damage by an overload through the installation of a Bun- nell Plate Overload Relay. Inserted in the negative “‘B’’ lead they will open the “B” supply instantly, if an excessive cur- rent is permitted to flow (as adjusted). The instrument is supplied with a ver- nier operating —s Line Binding Posts rent adjustment, Ne. alarm contacts and oe : manual reset. Num- ber 10268 — $12.50 each—Schedule BB. Operating current adjustment 32 Park Place Insulated Bar which Closes Alarm Contacts Alarm Binding Posts 10268 J. H. BUNNELL AND COMPANY, Inc. ‘ Manufacturers of Telegraph & Radio Apparatus For those who pre- fer to have an addi- tional set of contacts to break the 110 volt line at the same time Alarm Contacts iy we can supply our No. 10268-A, with additional contacts normally closed. They open only when the instrument trips. SPECIFY IN EITHER CASE YOUR NOR- MAL OPERATING CURRENT SO THAT WE MAY SUPPLY THE CURRENT AD- 3) JUSTMENT RANGE. No. 10268-A—$16.50 each—Schedule BB. New York City TO |Barawik’s new ishort wavedept J everything|est developments in radio at startling}y | desire Barawik Radio| kits. com Guide gives full/8Upplies. Orders filled same day details. ow &. SPECIAL AMATEURS _—————————— RADIO BARGAINS Shows the latest wrinkles, new amateurs /low prices. Get the set you want here The/|and save up to 50%. The best in parts ete factory-built sets and’ re- Se nq cived. Write for free Cat and Guide NOW! r Wholesale prices to dealers, set butiders, agents. ——___ BARAWIK CO.. 119 Canal Sts., Chicago, U.S. A. To your signais that puts em over. Batters down QRM, hurdles continents, lifts em clean over the ropes. Takes a mercury are to do it The rectifier of unlimited power, life and performance Read what the gang says. Write now and your rectifier problems are solved. RECTIFIER ENGINEERING SERVICE 4837 Rockwood Road Radio 8ML Cleveland, Ohio [J The A.R.R.L. Diamond Is the Emblem of a Real Amateur! every possible way. THE PERSONAL EMBLEM. pin-back style. light under a bushel. place in the radio fraternity. The League Emblem comes in four different forms. Members is endorsed and encouraged by the League. ber should be proud to display the insignia of his organization in rolled gold and black enamel, There are still a few fellows who are hiding their Wear your emblem, OM, and take your proper THE AUTOMOBILE EMBLEM. ready more than 800 cars are proudly displaying the mark of the “Radio Rolls-Royce.” 5x 2%”, on sheet metal, holes top and bottom, 50c each, postpaid. Its use by Every Mem- A handsome creation in extra-heavy 42” high, supplied in lapel button or Either style emblem, $1.00, postpaid. Introduced only this spring, al- heavily enameled in gold and black THE EMBLEM CUT. A mounted printing electrotype, the same size as the lapel button, for use by Members in any type of printed matter, letterheads, cards, ete. $1.00 each, postpaid. THE “JUMBO” EMBLEM. You've taken care of yourself, your car and your printing. How about the shack wall or that 100-footer? this big gold-and-black enamel metal emblem will get! Automobile Emblem. $1.25 each, postpaid. Think of the attention 19x84”, same style as Mail your order and remittance NOW to The American Radio Relay League : : Hartford, Conn, Say You Saw It In Q S T — It Identifies You and Helps Q S T

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If insist on the best, they must hand you Televocals. All standard types. Ask for them at your dealers. RS 4a TELEVOCAL CORPORATION lelevocal Bailding R-3,588 12th Street st New York, N. J. SZ Quality Tubes A Don’t Forget y RER That the A.R.R.L. Em- diem is the badge of every real Amateur. It is available in various sizes for button, pin, auto or radio- mast “That ham may recognize ham —display the A.R.R.L. Emblem.” American Radio Relay League, Hartford, Conn. TRANSFORMERS Guaranteed—Mounted—Complete 250 watt = I $10.50 700 watt CS “eee 4.50 700 watt 2 eases 21.00 tr Kw 2 Se eeereee 30.00 Add $2.00 for fil. winding SCES F. GREBEN 1927 So. Peoria Street, Pilsen Sta., Chicago, Ilonis ROBERT S. KRUSE Consultant for Shortwave Devices 103 Meadowbrook Road, West Hartford, Conn. Telephone Hartford 45327 Say You Saw It In QS T—It Identifies You and Helps QST The Fifth Age (Continued from Page 39) in ED. Anyhow I puts my best cq into get- ing acquainted, and before long we sound like two old maids at a ham convention. We walks on past the store, and neither one of us thinks anything about stopping. Our minds and my heart had qsyed liked someone had hanged a boarding house wash on my counterpoise. Before either of us knew anything about it we were in front of her house and I was still holding on to her books. “Sa,” I sez, “would you get mad if I asked you something?” “IT don’t know.” she sez, “Go ahead and ask it.” I clears my throat, and like I was starting in to send one of those reliability msgs, I asks : “T got a bid fer a frat dance and no date. Will you—Will you—er—go with me?” She smiles sweetly or do I imagine it and sez: “You will have to ask father.” That comes in R9 and sounds like bad qrn on a Saturday nite. “Gee whiz. Holy condenser dials.” I sez wondering what size shoe he wears. “When is he home?” “Every evening,” glad to see you.” “Yea;” I says, “just like he does a bill collector, and then he will be glad to see a bootblack.” Just then her ma announces that if she expects to eat she had better get in and start to work. I started walking home feeling as happy as a guy that has called an aussie and gets an R8 report only to find that he failed to get the last dot on the call. I had an idea what the qso with the old man would be like. I would step up sa hello and then provide the house with a new exit. A light bulb rose over my head. That was the rea- son CBY had laughed at me. He knew that I would get enough punishment to make up fer all the qrm I had ever caused him. Anyway the next eve I goes over to the house per sked and asks for Helen. She takes me in hand and shoves me in a small room off the living room. “Father,” she sez, “I want you to meet Bill.” “Pleased to meet you,” he sez between throwing out condensers, voltmeters, monkeywrenches and etc. out of a receiver that he had his head stuck in. “Trouble?” I queries in a small meek voice. “No. Not at all.” he sez, “I am just taking my daily dozen.” Vs I sez and he_ immediately straigitens up and I began a hurried search fer an exit. she sez. “He will be

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get- und ion. -her ing. ked ash out vas ind ing nd ad Tew hee Li —a “Do you know anything about a radio?” he asks. “Very “What is the matter?” “This thing won’t work worth a darn, and I got a bet with one of the boys down to the office that I hear better dx tonight than he does.” “Do you hear anything at all?” I asks. “Not a blankety blank thing.” he returns. “Ah, that sounds easier.” I sez and sticks my head in the cabinet. If I can only fix the set I thought to myself I sure will be in good wid the old man. I looked through the whole thing without seeing a thing wrong, and in moving around to get a better look I feels a loose wire wid my foot. One look and I saw that the B bat lead fer the R.F. tubes was nil here. So I hooked it up when he wasn’t looking and then I put my head inside again. When he was looking again I pulled my head out of the set and sez: “There, I’ll bet the thing will work.” I turned the switch and immediately the room was flooded with music. He looks at me like I was the radio congress kicking the hams off the air fer good. “Your sure a wonder. How in the world did you do it?” “Well,” I sez thinking of Peck’s theory, “the syncronating by pass condenser was fowled with the neutralizing oscillating hetrodyning frequency, and after unjoining the diaphram it worked O.K. Now may I asked you a question? Can I—.” but he had already plugged in the phones and was listening fer dx. He waved a hand at me. “Do anything you want. I have lost too much time now.” I walks out into the living room and an- nounces that it is ok with the old man. So we qsy’s to my leaping lena and dashes fer the dances. About aussie time we return and the old man is as happy as a youngster with a new seven and a halfer. de has a list of W’s as long as an unraveled filter condenser. “Just wait until I tell the gang about this,” he sez, “It sure will make ’em sit up and take notice.” and he chuckles to himself in anticipation of the great time he will have. “Sure is ok with me.” I sez and bids Helen an affectionate goodby using 88’s as a standard. On my way home I just began to wonder what CBY was so happy about. I will make him laugh up the other side of his a when I tell him about the hit I have made, little.” I sez, It is one month later. I have sold my tube fer twenty bucks, and my filter fer ten. Still I can’t see just what the laugh of CBY’s meant. Sure a funny thing. Guess it will be an unexplained mystery like the origination of static. Oh, yes. I forgot to mention that CBY has a nice note with that new fifty of his. HAM-ADS ANNOUNCEMENT Effective with the October, 1928, issue of QST the following changes will be made in the rules of this department. The Ham-Ad rate will be 15c per word. The restriction which has limited use of this column to mem- bers of the American Radio Relay League will be removed and advertising may be signed either by company name or by an in- dividual. A special rate of 7c per word will apply to advertising which is obviously non- commercial in nature and which is placed and signed by an individual member of the American Radio Relay League. Please read carefully the following conditions under which advertising in these columns will be accepted. (1) Advertising shall pertain to radio and shall be of nature of interest to radio amateurs or experimenters in their pursuit of the art. (2) No display of any character will be accepted, nor can any special typographical arrangement, such as all or part capital letters, be used which would tend to make one advertisement stand out from the others. (3) The Ham-Ad rate is l5c per word, except as noted in paragraph (6) below. (4) Remittance in full must accompany copy No cash or contract discount or agency commission will be allowed. (5) Closing date for Ham-Ads is the 25th of the second month preceding publication date. (6) A special rate of Te per word will apply to ad- vertising which, in our judgment, is obviously non-com- mercial in natvre and is placed and signed by a member of the American Radio Relay League. Thus, advertising of bona fide surplus equipment owned, used and for sale by an individual or apparatus offered for exchange or advertis- ing inquiring for special equipment, if by a member of the American Radio Relay League, takes the 7c rate. An attempt to deal in apparatus in quantity for profit, even if by an individual, is commercial and takes the l5c rate. Provisions of paragraphs (1), (2), (4) and (5) apply to all advertising in this column regardless of which rate may apply. Say You Saw It In Q S T — It Identifies You and Helps Q S T New 80 meter band 9DRD, Edwardsville, POWER crystals tested 600 volts. $15.00, 40 meter band $22.5Q@ Kansas. THE life blood of your set—plate power. Powerful per- manent, infinitely superior to dry cells, lead-acid, Bs, B eliminators, Trouble-free, rugged, abuse proof, that’s an Edison Steel-Alkaline Storage, B-battery. Upset elec- trically welded pure nickel connectors insure absolute quiet. Lithium-Potassium solution (that’s no lye). Com- plete, knock-down kits, parts, chargers. Glass tubes, shock-proof jars, peppy elements, pure nickel, anything you need. No. 12 solid copper enameled permanently perfect aerial wire $1.00, 100 ft. Silicon steel laminations for that transformer 1l5c lb. Details, full price list. Frank Murphy, Radio 8ML, 4837 Rockwood Rd., Cleveland, Ohio, PURE aluminum and lead rectifier elements holes drilled brass screws and nuts, pair 1”x4” 138c, 1”x6” 165c, 14%4"x6”" 17c, 14%4”x6” 19c. Sheet aluminum 1/16” $1.00, lead $1.00 square foot prepaid, $1.00 or more. Silicon transformer steel cut to order .014” 10 Ib. 25c, 5 Ib. 30c, less than 5 Ibs. 35c Ib. .022” 5c less per Ib. Not cut 2-7” wide l5c lb., minimum 10 Ib. postage extra. Edge- wise wound copper ribbon 7 sizes see January QST. Air pocket and stand off insulators 25c each. 4 for $1.00. Glazed porcelain 5 and 614” long prepaid on 4. Electro- lytic condenser parts, $1.50 prepaid. Geo. Schulz, Calu- met, Michigan. HAWLEY Edison element battery and parts standard for over five years. Look at our patent pending connec- tor—no thin wire to drop off—contains 20 times more metal than regularly used. Heavy shock proof cells, fibre holders, etc. Everything for a rapid-fire “B’’ sup- ply. Complete assembled 100 volt “B” $10.00. Knock- down kits at still lower prices. Chargers that will

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charge to 160 volts $2.75 to $4.00. Trickle B Chare« 150 volt “B” $3.75. Special trans- mitter “B up to 6,000 milli-amp capacity, any voltage ‘ interesting literature, testimonials, te. B. H th, 360 Washington Ave., Danbury, onn FOR a nur years we have been supplying the highest paratus to laboratories, universities, broadcast mental, marine and amateur stations. Building t as well as standard items for any particular the art Our long experience is your guarantes Merely state the items in which you are ir for literature covering same. Thos. Ensall, l ew A re., Warren, Ohio. JEWELI M new, 25% discount. We stock Ham- marlund, Ww nard, Acme, Thordarson, Pyrex, Na- tional, Car dwin, CeCo, Yaxley, Signal, Bakelite, Samson, | RCA, Browning-Drake, Fleron, Ferranti, R . Eby, Victoreen, Silver-Marshall, Tyrman, Grid Tubes, Carter, Bodine, Claro- stats, Air Speakers, Exponential Horns, Abox, Kingstor , M Ham Call Books, Keys, Relays, Buzzers, Exide, Pt nghouse, Fritts, Newcombe-Hawley. Many other Ham and BCL apparatus. Tell us what yo yunts to Hams, dealers and custom set builder Roy C. Stage, Montgomery & Burt Sts., Syra N. } OMNIGRA lexes, condensers, crystals, trans- mitters, 5 ipersynes, S tubes, Vibroplexes, elec- tric and 1 receivers. Phone transmitters, motor generators hokes. Bought, sold, exchanged. L. J. Ryar Hannibal, Mo. FOR sak tation receiver DET and 2 step transmitte 15 watt panel mounted with meters, ete., $10% | Rutger Street, St. Louis, Missouri. SALE onl; new condition, fifty dollars. George H. Smith, Penn. S8ANC., SELL or Western Electric portable navy tele- phone trar | three tube receiver complete, $40.00. RCA trans i ET-3619 Kenotron power unit model ET- $60.00. Rectifier tubes, meters, coils, micr Real bargains. Write for bargain list. VE2A‘ |, Thetford Mines, Quebec, Canada. LARGE 22 vac batteries, 89c, RCA 50 watters, original REL 50 watt sockets, $1.50, 6 months guar ew 210s also 281s each $4.50, 6 months guar As and 199s 79c, Readrite 2 meter tube checker Resistometers 49c, RCA 535 rheostats eee: 0 her | sizes, 15c, Willard storage B atteries $ ilent 2% amp. homecharger $4.75, Bradley wi Federal transformers $1.19, pure aluminum — sq. ft. 80c, Electrad 5000 ohms, grid leak 5 panels le sq. inch Bakelite panels 2c sq. incl r Call Books 865c. Westinghouse four volt er $6.25, six volt $7.50, Brandes phones $2 t, everything for hams. D.L. Marks 125 Madisor bany, N. Y. ; LOOK 9E YT Write for list! UX852 never used, $27.5 coils, $6.00. 12 Jewell meters cheap. ( om] mitter and receiver, $20.00. 9EYT Lincoln, TI . i QSL ham ) neat and reasonable cards now. Samples on r Radio 1NQ, 206 Metropolitan Ave., Roslindale, M SELL—3 Cot ensers ; one each 23 plate, 17 plate, 33 plate: ma key, 10 amp.; home-made relay, large singl WE VT2; 3 WE VTIs; Cootie =. _~ LF a sg 23 plate; Cardwell 43 ate; aiaw (ys Make we Eg e offer, M. B. Seyffert, SELL—new watter) $15.00. Slightly used 203A, $15.00. Bot! aranteed in good shape. L. B. Hallman, Jr Oates St., Dothan, Ala. HAMS : Get r winter DX. Order your QSL cards now, with ediate. Satisfied hams everywhere. Highest qua Prompt service. If you need cards send nples and prices. 8CUX, Milling- ton, Michigar FOR sale: t dial Omnigraph, with 32 dials, cost $41. Fir ffer takes it. Prepaid. Write 8DII, 34 Howard A umton, N. Y. FOR sale, N . Service Test Set, complete with batteri« ). Sell for $55.00. Will service all kinds of bes. L. W. Van Slyck, Ironwood, Michigan FOR sale—Jev 34 0-15 volt AC $3.00; Jewell No. 33 0.300 mill Weston No, 301 0-800 mills d.c. $3.50: 2 Jews { 0-8 amps TC $4.00 each; Jewell No. 53 0-8 volts d.c. $2.50; General Radio hot-wire 07 amps. $1.50, Also four Xtals SRS at different frequencies in 160 meter band at $7.00 each. R. A. Donnelly, 2CPp, Brielle, N. J. QRH? Will your wavemeter do next year? Does it cover the ten meter band? We'll rebuild it to meet the new requirements. We calibrate amateur wavemeters to an accuracy of one fourth of one per-cent. Two bucks for any band, three bands five bucks. All calibrations from standard frequency crystal oscillators. All work guaranteed. Higher degree of accuracy if desired. We build precision laboratory wavemeters and oscillators, Write for dope. Something new, center-tap kit for fila. ment transformers. Ask us. QRX We can save you money on all standard radio apparatus. Write for prices, 9BVC, Lutesville, Mo. SOMETHING for your notebook! Complete diagram and three page explanation RCA 200 watt, 500 cycle, ACW transmitter. See July hamad-price fifty cents. C. 0, Slyfield, 8LA, Frankfort, Michigan. WANTED—power filter and rectifier supply for 250 watt tube, C. J. McDonald, Dresser Junction, Wis. Hams: Get our samples and prices on printed call cards made to order as you want them. 9APY Hinds, 19 S. Wells St., Chicago, Ill. FOR sale or trade. Delco light plant 10 amp. 32 volts no batteries, in Al condition. Worth $65. Want 1000 MG set. Will pay difference. 6ARV, Earle L. Mallette, Box 269, Saratoga, Calif. NEON tubes—-General Electric type G10, $1.00 each. Add postage. Radio 9AUB, 1231 South Meridian St., India- napolis, Ind, SELL low power xmitter, power supply and receiver. Cardwell, Aero, Thordarson, etc., parts. Fine for beginner. Almost new at less than half cost. 6CKS, Hurley, 1180 Mullen Ave., Los Angeles, Calif. TRADE Conn. C melody saxophone and case for REL apparatus or GR type 358 wavemeter, Weston or Jewell meters, or what have you? C. E. Peterson, 2719 Price Ave., Cincinnati, Ohio. SELL—Acme 150 watt filament transformer, $7.50, LIV, 66 Vine St., Bridgeport, Conn. CHOKES, 30H 100 M.A. $2.00. 30H adjustable 160 M.A. $5.00. 250 M.A. $7.50. Transformers, 500 to 1000 each, side midtap, 250 watt $8.00. 325-325-744-7%4 $5.50. 275- 275-5 $4.00. Complete new lists and specifications ready. M. Leitch, Park Drive, West Orange, N. J AERO coils, REL transformers, grid leaks, chokes, xmit- ting tubes, and other items. New and of standard makes, priced low. Write for list. H. A. Carr, 1114 Monroe St, Vicksburg, Miss. WANTED, 24-1500 or 32-500 volt dynamotor. Wisner, Neb. QSL cards, 100 two colors, 85c. New enlarged line. Cartoons, radiograms, stationery, etc. M. Selden, Cranesville, Penn. CURTIS says its DX time now! Thordarson mounted transformers: 550-volts each side, two 7%4-volt filaments, each $20.00; Thordarson 350-550 power transformer $16.00; 1000-1500 power transformer $22.00. Special Thordarson 650-volt power-filament transformers for 7%4- watters $6.90. Aluminum square foot 85c; Lead square foot 85c. Potter 2-Mfd tested 1000-volt condensers $2.19. “Ham-List” 4c. James Radio Curtis, 5-A-Q-C, 1109 Eighth Avenue, Fort Worth, Texas. HEADQUARTERS for hams:—Mueller 150-watt input tubes $15.00. Aerovox 1,000-volt 1-mfd condensers $1.29. New complete 7%4-watt transmitters: tube, transformer, rectifier, key, etes. 20-40 meters $40.00. Receivers 20-40 meters and one-step $17.50. Potter 2000-volt tested 1-mfd Condensers $2.50; 2500-volt 1-mfd condensers $3.25. Amateur Callbooks $1.00. “Ham-List” 4c. Robert Curtis, 1109 Eighth Avenue, Fort Worth, Texas. COMPLETE 50-watt short wave transmitter with power supply, tube rectifier, wave meter and specially built receiver. This is a first class, complete, powerful trans- mitting and receiving station for which I have no further use because of business interests. Parts are finest obtain- able, consisting of Acme, Thordarson, National, General Radio, Weston, RCA, etc., and cost over $400. Will sell everything complete for $150 cash and guarantee pur- chaser first class condition. List of parts on request. K. N. Ford, Apt. 3-J, 7010 Continental Ave., Forest Hills, Long Island, N. Y. WESTINGHOUSE radio frequency ammeter. Type Cay. Range 0-10 amperes with protective shunt. Switchboard 9CHZ, 92 Say You Saw It In QS T— It Identifies You and Helps QST