"4 -IN -2 "SHORT -WAVE ALL -ELECTRIC SET See Page 398

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HE BUILT THIS "4 -IN -2 "SHORT -WAVE ALL -ELECTRIC SET See page 398

Hi- Fidelity on Short- Waves -Novel 1 Tube All -Wave All- Electric Set 5 Meter Transceiver-All -Wave Oscillator- 6 Tube All -Wave Receiver ...... SERVICE MEN'S ESSENTIALS FOR ALL MEMBERS OF THE ORSMA

N-11.ß'1 ARE THE SERVICE MEN'S ESSENTIALS? THE OFFICIAL RADIO SERVICE MEN'S ASSOCIATION has arranged to supply a number of "Service Men's essentials" for its members and associate members only. These essentials are priced at cost, plus a small additional fee which is the only source of income that the Association has. No one obtains any profit or benefit, except the Association itself. Whatever profit accrues, is reinvested for the furtherance and enlargement of the Association. By using the letterheads, hillheads, etc., you present the business -like appearance to your customers. In addition, the Association has made arrangements with most of the prominent manufacturers to allow special discounts to members, providing ORSMA letterheads are used when ordering.

No. 1 ORSMA LETTERHEADS These letterheads, shown on the right. are furnished with your name, address and telephone number. printed on excellent paper. They are sold in lots of 100 or multiples thereof. with a distinct saying for single orders of 1.000 or more. Per 100, 60e; per 1000. $3.00. No. 2 ORSMA ENVELOPES 71rmbrrship These are furnished to match the letterheads, printed with your and of the Association. 1ÇÇrrrlifirUf handand yin hand with the letterheads anda usually ordered in the same quantity. Per 100, 60e; per 1000, $3.00. No. 3 ORSMA SERVICE RECORD CARDS These serve a double purpose; whenever you complete a Job you rill out the report -bill and hand It to the customer; this L rT..l..{ the "psychological moment" to collect. Icy the use of carbon laver a permanent record is kept. Furnished with name. No. 1 -60e Per 100 0f6dal FaDie 4rroin91rns6aeriekm address and telephone number. Per pad of 50, 60c; per 10 $3.00 per 1000 a. W.I.... C4..4.J._ 1. e. d. ..J. t. L. .y. pads, each of 50, $3.00, ra.Ma..itmi No. 4 ORSMA INSPECTION LABELS The label Is to be filled in with the proper dates, and pasted inside the set or cabinet where the cuss Omer will see it. It is a continuous remainder to him that when service is needed. he can call you again. The advantage is apparent. Per 100. 60e; Per loutt, $3.06. No. 5 ORSMA LAPEL BUTTON At the suggestion of many members a handsome lapel button bearing the name and emblem of the Association has been designed. It signifies that you belong to the ORSMIA; and No. 14 -50c each In addition it gives your customers a better appreciation of (Plus IOc for Postage) the professional nature of your work. 50e each. No. 6 ORSMA BUSINESS CARDS These are furnished on a fine grade of paper in two colors with a blotter back. Thus they present an incentive to customers to keep them in a prominent place. They are Printed your esss4aDnd telephone and bear the official seal of the Associa- tion. witli urname, 1000,dd 9 & 10 ORSMA EMBLEM CUTS These cuts for printing. advertising. to are furnished in two styles and sizes. They may be used for newspaper r telephone -hook advertisements or for printing of any kind. Large size. lye x lye in., $1.35 each; small size. % x % in.. $1.20 each. Poo No. 11 ORSMA MEMBERSHIP SIGN A set of three signs. printed of heavy rands. and having holes punched in order to Snob hang In office or store. These are sold to members and a.ahde members. Large enough to be quite prominent and the two tote effect mikes then attrai tire. Set of three, 50e. No. 12 ORSMA ADVERTISING DISPLAY SIGN A two color sign printed in large letters with your name. address and telephone. >rralp moan .rn..r,. with the seal of the Association. This sign is .sold in quantities of 21 or more and is ideal for hanging in stores, olliees, etc.. for advertising purposes. Set of 25 cards. $3.00. a.... No. 13 RADIO SERVICE MEN'S ASSORTMENT PACKAGE This includes one gold tilled lapel button, 100 letterheads, loll envelopes, 50 service record cards, and 100 labels printed with your name and address as described above. The whole assortment costs only -$3.00-a worth -while saving. Complete, $3.00. No. 3 per pad of 50 14 CERTIFICATE -60c No. ORSMA MEMBER $3.00 ten pads, each of 50 No. 5-50c each A handsome diploma -like certificate engraved on stiff vellum -bond. The certificate Is per Personally signed by the President and Executive Secretary and the corporation stamp or the Association is impressed on a red seal attached to it. Your name, certificate number and date of registration are lettered by hand and the Certificate is mailed In a cardboard tube to insure safe delivery. Each SOC. plus Ice for tart age.

STEPHEN MARKO

139 anthtw D.,.a Tel 3 -0672 A IRON, O.

No. 6 -75e per loo No. 4 -60e per 100 No. 2-60e per 100 $4.00 per 1000 $3.00 per 1000 $3.00 per 1000

I- -1 Application for OFFICIAL RADIO SERVICE MEN'S ASSOCIATION Itt:-1-35 Membership in ORSMA 99 Hudson Street, New York, N. Y. Please send me the following RADIO SERVICE MEN'S ESSENTIALS which I have Executive Secretary. ORSMA -elected from this advertisement. My remittance for $ is enclosed. Send 99 Hudson Street, New York, N. Y. remittance in form of check or money order. Register letter if it contains cash, currencu or unused U. S. Postage Stamps. Kindly send an application blank for f7 Full Membership El Associate Membership

Name

Street or Box Name ORSMA No. City State Address City and State iet-1 -35 t- RADIO -CRAFT for JANUARY, 1935 385 OPPORTUNITIES are many for the Radio Trained Man Don't spend your life slaving away in some dull, hopeless job! Don't be a $20 or $30 a week. Let me show you how to satisfied to work for mere on earth. get your :fart in Radio - the fastest - grossing, biggest money - making game Jobs Leading to Salaries of $50 a Week and Up Prepare for jobs as Designer, Inspector and Tester -as Radio Salesman and in Service and Installation Work -as Operator or Manager of a Broad- casting Station - as Wireless Operator on a Ship or Airplane, or in Talking Picture or Sound Work-HUNDREDS OF OPPORTUNITIES for a real future in Radio! Ten Weeks of Shop Training Pay Your Tuition After Graduation We don't teach by book study. We train you on a great outlay of Radio, Television and Sound equipment -on scores of modern Radio Receivers, huge Broadcasting equipment, the very latest and newest Television apparatus, Talking Picture and Sound Reproduction equipment, Code Practice equipment, etc. You don't need advanced education or previous experience. We give you - RIGHT HERE IN THE COYNE SHOPS - the actual practice and experience you'll need for your start in this great field. And because we cut out all useless theory and only give that which is necessary you get a practical training in 10 weeks. TELEVISION and TALKING PICTURES And Television is already here! Soon there'll be a demand for THOUSANDS of TELEVISION EXPERTS! The man who learns Television now can have a great future in this great new field. Get in on the ground -floor of this amazing new Radio development! Come to COYNE and learn Television on the very latest, newest Television equipment. Talking Picture and Public Address Systems offer opportunities to the Trained Radio Man. Here is a great new Radio field just beginning to grow! Prepare NOW for these wonderful opportunities! Learn Radio Sound Work at COYNE on actual Talking Picture and Sound Reproduction equipment. ern Television equipment. You work on real Talking Picture FOR YOUR TRAINING machines and Sound equipment. You learn Wireless Operating PAY on actual Code Practice apparatus. We don't waste time on useless theory. We give you the practical training you'll need After You Graduate -in 10 short, pleasant weeks. I am making an offer that no other school has dared A to do. I'll take you here in my shops and give you this MANY EARN WHILE LEARNING you have You get Free Employment Service for Life. And don't let lack training and you pay your tuition after of money stop you. Many of our students make all or a good part graduated. Two months after you complete my of their living expenses while going to school and if you should course you make your first payment, and then you need this help just write to me. Coyne is 33 years old. Coyne have ten months to complete your payments. There Training is tested - proven beyond all doubt. You can find out are no strings to this offer. I know a lot of honest fel- everythingabsolutelyfree. Just mailcoupon for mybigfreebook! lows haven't got a lot of money these days, but still H. C. Lewis, Pres. RADIO DIVISION Founded 1899 want to prepare themselves for a real job so they COYNE ELECTRICAL SCHOOL lay offs. won't have to worry about hard times or 500 S. Paulina Dept. 15-8H, Chicago, Ill. I've got enough confidence in these fellows and in St., my training to give them the training they need and Mai! Coupon Today for All the Facts me have training. 111.6. pay back after they their H. C. LEWIS, President If you who read this advertisement are really inter- in your future here is the chance of a life time. Radio Division, Coyne Electrical School ested S. Paulina St., Dept.15 -8H, Chicago, Ill. Mail the coupon today and I'll give you all the facts. 500 Dear Mr. Lewis: -Send me your Big Free Radio Book, and all details of your Special Offer, including your "Pay After ALL PRACTICAL WORK Graduate" offer. At COYNE in Chicago Name. ALL ACTUAL, PRACTICAL WORK. You build radio sets, install and service them. You actually operate great Broadcast- ing equipment. You construct Television Receiving Sets and ac- Address . . tually trasmit your own Television programs over our mod- City State

Please Say That You Saw It in RADIO -CRAFT (1dio.aft FOR TM(

SERVICE MAN . DEALER RADIOTRICIAN

HUGO GERNSBACK, Editor -in -Chief J. T. BERNSLEY, Managing Editor RA C. W. PALMER R. D. WASHBURNE Associate Editor Technical Editor

wE DO Ou9 1.0,R1

CONTENTS OF THE FEATURING JANUARY, 1935, ISSUE BROADCASTING

VOLUME VI Number 7 IN OUR NEXT ISSUE:

Editorial: Short -Wave Applications Hugo Gernsback 391 WATCH for the next issue of RADIO -CRAFT in which The Radio Month in Review 392 you will find descriptions of all the new developments in radio operation, Short -Wave Radio Pictorial 394 from studio to home. Hi- Fidelity on Short Waves 396 ALL ABOUT BROADCASTING. If you want to know jusF How to Build the "Four -in -Two" Short -Wave Electric how far the American broadcast system has progressed Set J. T. Bernsley 398 to date, and just what are its trends, read the article on The Latest in Police Radio Receivers 399 this subject which has been prepared by one of its active New Short -Wave Link to Byrd 399 participants.

Short -Wave Stations of the World _ _ 400 HOW TO CHOOSE YOUR RADIO SET. With a veritable The Latest Radio Equipment 402 galaxy of radio sets staring him in the face as he enters An Improved 6 -Tube All -Wave Set M. K. Baker 404 the store door of the average radio dealer, it is no won- Build This Novel I -Tube All- Electric, All -Wave Set der most persons buy by "luck" (or lack of it!), rather H. G. Cisin 40 than good judgment. All the sets seem to "listen" alike, How to Build a New 5 -Meter Transceiver and so our hero takes a second squint at an attractive A. G. Heller 406 cabinet, checks with the bank roll, and says, "gi -'me." But Elements of 4th Dimension P.A. or Sound Systems the CHASSIS harbors the real value. How does one chassis (Part I) H. S. Manney and C. R. Shaw 407 differ from another; how can you tell a "good" chassis from a "poor" one? Well, the answers constitute International Radio Review 408 our author's story. A Short -Wave Band -Spread 2 -Tube Portable Set Frank J. Lester 410 An Improved 2 -Tube Short -Wave Booster S. Miller 410 RADIO -CRAFT is published monthly, on the fifth of the month preced- i ing that of date; its subscription price is $2.50 per year. (In The Listening Post for All -Wave DX -ers Canada and foreign countries, $3.00 a year to cover additional postage.) C. A. Morrison 411 Entered at the post office at Mt. Morris, III., as second -class matter An Economical P.A. Amplifier A. J. Koenig 412 under the act of March 3, 1879. Text and illustrations of this magazine are copyright and must not An Impressive 7 -Tube Dual -Range Superhet 412 be reproduced without permission of the copyright owners. We are also New Design in All -Wave Antennas A. H. Lynch 413 agents for WONDER STORIES and EVERYDAY SCIENCE AND MECHANICS. Subscription to these magazines may Short -Cuts in Radio 414 be taken in combination with RADIO -CRAFT at reduced Club rates. Write for Readers' Department 415 information. Copyright 1934. A Real "How to Build" Service Man's All -Wave Os- Continental Publications, Inc. cillator Howard J. Benner 416 ORSMA Members' Forum 417 HUGO GERNSBACK, President I. S. MANHEIMER, Secretary Operating Notes 418 Published by Continental Publications, Inc. Publication office: 404 RADIO SERVICE DATA SHEETS: N. Wesley Ave., Mount Morris, Illinois. Editorial and Advertising No. 129 Victor Model 102 4 -Tube A.C. - -RCA Office: 99 Hudson Street, New York City. Chicago Advertising D.C. T.R.F. Receiver; General Electric Table Office: L. F. McClure, 919 North Michigan Avenue, Chicago, III. Model M -49 4 -Tube Radio -Phonograph Dual - Western Advertising Office: Loyd B. Chappell. 511 So. Alexandria St. Wave Super 419 Los Angeles, Calif. No. 130 -Stromberg- Carlson No. 69 4 -Tube All - London Agent: Wave Superhet. Selector (Converter); Pilot Hachette & Cie., 3 La Belle Sauvage, Ludgate Hill, E.C. 4 Model 63 All -Wave 6 -Tube Superheterodyne 422 Paris Agent: Hachette & Cie., Australian Agent: McGills Agencl RADIO -CRAFT'S Information Bureau 420 111 Rue Reamur 179 Elizabeth St., Melbourne

386 RADIO -CRAFT for JANUARY, 1935 387 Now ¿71p"ot Zits a ÇÓOdJC

ON, NOT SO GOOD BILL, NO, TOM. no SEEN TOO BUSY WANING I AM LUCKY. TOM, RUT YOU SUT IM STILL HAVING FUN GOOD MONEY OUT OF RADIO TO NADINE SAME CHANCE, PLAYING WITH RADIO, SPEND TIME 'PLATING- WITH IT. EEMEMSER EOVT A YEAR A60 GEE, THERE'S DJ C IN HADDJ(LAST NIGHT I SNOWED YOU A SOOK FROM BERLIN. THAT'S THE TENTH ON A LITTLE SET I BUILT. NATIONAL RATIO INSTITVIE now TOLD ABOUT THE OPPORTUNITIES FOREIGN STATION IS RADIO STILL YOUR GOSII,SILL,VOU'RE SURE LUCKY. AND 016 FVTUR( IN RADIO, AND TONIGHT, RADIO IS HOBBY TOO . I NOTICED YOUR SWELL CLOTHES NOW OTHERS NAP SUCCEEDED SURELY FUN. ANP SNAPPY CAR. I THOUGHT TNROV,N THEIR NOMI TRAIN You HAD INHERITED A MILLION. D IM61 REMEMBER, I TRIED TELL ME ABOUT IT. E DT TO GET YOU TO ENROLL. D FOR THEIR COURSE WHEN I DID, Ea 1,1C-

THEN I CAN MAKE OR INSTALL AND OR MAKE 600, MONEY YOU CERTAINLY N.R.I. TRAININ& WELL, IT WAS THE SM MOVE I NARY REAL MONEY SERVICE LOUD IN ANY ONE 01 THE KNOW RADIO. CERTAINLY PAYS. I EVER MADE. I'M DOING SWELL. MARY AND IF BILL OTHER NEW AND 6R0W,N6 SERVICING MARIA SYSTEMS MINE NEVER JUST STARTED A FEW I ASZ TO RE MARRIED MELT MONTH, TOM, RANCHES OF RADIO, SUCCEEDED, ( MONTHS AGO AND I'M RADIO SETS 'HIRES No 1 ND OF soon SOUNDED FETTER WHY DON'T YOU SNAP OUT of IT! DON'T I CAN JOBS FOR A TRAINED MAKING 6000 MONEY STAT In THAT DREARY LOW PAY 40E ALL ALREADY. TNIS SPARE TOO: RADIOMAN: YES, TOUR LIFE. RADIO IS MORE THAN A THE WORN IS SWELL SIR, I M 601HÁ TO SEND RAYTNIN6. WS A 116 SUSINESS. IT'S MamAT FREE 000K FUN, AND 50041 I'LL TOUR OP,OATUNITY. TAKE MI TIP. IT D OFT THE DOPE SE ALL SET A ISN'T Too LATE. RADIO IS RILL RIGHT NO FOR YOUNG GOOD ANO GROWING- FULL TIME JOB

OH,TOM. ITS WONDERFUL' OUR WORRIES ARE OVER, To moue NOW FAST YOU'VE IM MAKING 0000 MONEY NOW. THEMES A FUTURI GONE AHEAD SINCE YOU ANO SIG WENT INTO AAD,O. WI AHEAD FOR US IN THIS COULD NAVE ROTTEN LIVE WIRE RADIO r e . E A IwiII help you start MARRIED ON WHAT YOU FIELD WERE GETTING BEFORE. a spare time or full time Radio service business Without Capital

Many Radio Experts Make 40, $60, $75 a Week The world-wide use of Radio sits Lat made I'. ;uirc'is of opportunities for good spare time or full time MANE GOOD IMONEY Iladin OUNiue+.,rs, Many of the ,el eat can mllhm. Had., sets are only 'S'; to 40,4 efficient. I will show HEREFS PROOF >011 how to CANT. in ou this condition. I Kill show )01: how to install and senke all types of receiving seta in spare time. I'll show )m. how to make enough money while learning Radio to start your own service business- CIup the coupon. Cat ply free hook. "111th Rewards in Radio." head how "Made $6,000 in 2 Years" hundreds of N, lt, 11. men hate made good money in apare tune or full time businesses. "Soon after the h do- -Ion -tartui, I ftamd myself Many Make SS, S10, SIS a Week Extra in Spare Time While Learning Yl ithnut a job, nut I n nti! protested hob N. It. The day you ruull t send oI ,lilry ljolr t,,: 'a.mg 2$ Motto jobs common In almost every' 1 swung L training. a right to full time Radio neighborhood lml pane time m I, . I girt rot pia l:- and ideas that have made $200 to $1.000 St miring and have made over 56,000 in a little over a year for many N. R. 1. men Olt spelt Ilme,- 31y 1 'uut-v it Lotions as "The Training that pays de Iwo .wars. " -Wm.J Spaniveot, Starry Radio Service. for itsrlt." t'3 Broadway, Newark, N. J. Get Ready Now for a Business of Your Own and for Jobs Like These In lust :Joan 11 yew. itadil: gloat!. la. I I'4II ntrr :O0d1UO $010, Thousands more jobs will hC upeurd by men Radle dr rtd,rinue lit', Ih Oa,.4 -ling -tat ion, rte engineers, op,ra tor, ' "$500 O' a Year In Spare Time" ,tatlal IuaIIagera and pay' up to $5,IN00 a year, )tale;farturrr, unpin)' tester. Inspector,. S "Althnngll Loing spare time Radio work only, I have I Id Inert. engineers. arm ileuleu, huyera, for jut paying try to SL500 year. Dealers' averaged about SS(KI a Tear extra in addition to my ud jobbers employ ,erv'eemen. a1e.nlell, burlr -. m:,nagen, and pay up to 1100 ' tegolar inrume lull time Radio work would net me heck. 31)' Fret Rook tells about these and oust Ippornudl ter. man) times that amount. " -Edw. H. Fawcett, Slough Television, Short Wave, Loud Speaker Systems included a Rd., Ladner, B. C.. Canada. There is oovorluuity for you in Itadtu. Ir haul, certain. 'relevlion, WUt ' :> ' lice Radio, automobile : . laud Speaker winos hip Itstlio. In it ial ion Radio -In ver)' la ankh, derelopmrnn and indu°remen, a } FREE: Radio Ling place, Isere Is a read future t'or thou-alai, ,f met who .rally v w .uuw -teen with N. 11. I. training. Ott tbC training that, Servicing Tips Radio e04 clear. Find Out What Radio Offers You Let me PROVE that my Course Is that easy to understand, and fasr¡nating to 1 am sooIIsure N. It, 1. can train you sallsfa, roily I S` you re ` Andy. d the 01011110 for a free m writing to reload every penny If your tuition it lesson. `T omble Shooting In not sulhlhd with my Lesson and Inri .net ion Stn Waal 4 -t.l'. and Ramey Set,." This Illler- o111 1e1Nm, Get my al -page hark of It's :n. I'aendt age. tell- ``A I -ling lesson gives 1:12 ways r eet any ambitious fellow over 15 yam of It ill l'MII -e: Litt ¡armai Itadln Roubles, I ale IS llling About Itadllia ppoAAUlllt h+: ahonll 1' Dlt. book to more that you. then re dole¢ nd m :Ik lug. Fli,d OUT %ilia: t,,o, ran toaster Radio-just as thnu- Radio offers v allo oldhr i1, m- -t('T \UST, -

, tt 1: nnd- of other fellows hanse dune. Many 51a11 coupon In ,loss]. e n it un a ó0 of Timm, n II ham men a grammar -6N} poIrard. Ps .eLoN rdural inn. and 1111 Itadiu or lech- .,al elptriente, bare loom. Radio J. E. SMITH, President tl-pert and now won two or thr. Nat'l Radio Institute, Dept., SAX +W,Poo . ". s, °sue 1 their former pa)'. Mail the loll-on C, 1.á ;gis -R, /1, Washington, D. ''

c°c'N .'.`

l'líuso S o Thrrt i-a+I .Slur It il+ R,tpnl-(1;;FT 388 RADIO -CRAFT for JANUARY, 1935

GOOD BOOKS WHICH HELP MAKE RADIO WORK MORE PROFITABLE i a.

Here are the Presented on this page are books of the RADIO-CRAFT LIBRARY SERIES -a most complete and authentic set of volumes treating individually, important divisions of radio. Each book has been designed to give radio men subjects covered- the opportunity to specialize in one or more of the popular branches of the industry. You will find them real help in your work and they will contribute to your money earning capacity. Read these books during your spare time at home. The authors of these books are well -known to everyone. Each is an expert radio man; an authority on the Set subject-each is thoroughly familiar with the field which he represents. This is the first real opportunity that you have ever had to build a library of radio books that are authentic. Analyzers MOST OF THE BOOKS HAVE BEEN RECENTLY REVISED AND REWRITTEN TO KEEP THEM UP TO THE MINUTE. Mail coupon below for your books. Tubes Book No. I Book No. 6 Book No. 10 Radio Set Analyzers Bringing Electric Sets Home Recording and Superheterodyne And How To Use Them Up to Date All About It By L. DER Circuits VAN MEL By CLIFFORD E. DENTON By GEORGE 1. SALIBA

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GERNSBACK PUBLICATIONS. INC., 99 Hudson Street. New York, N. Y. I lisce circled below the numbers of boors In the RAI)IO -CRAFT T.TURART SERTES o filch you are to send me. and have deducted 3J% for ordering five Ir.) books or more. I have included my remittance In full. at the price of 50e each. when less than the books are ordered. The amount of my remittance is (Stamps, checks or money orden accepted.) Circle numbers wonted: I 3 3 4 ti 8 7 8 9 10 11 12

rame Address

Cltf State RC -136 M Please Say That You Saw It in. RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935 389 ?eLI[AHU EXILkI THE- ONE MAN IN 1000 WHO CAN SERVICE MODERN RADIO REC-EIV.6RS

RADIO SERVICE WORK - NOW 0111125 GREATEST OPPORTUNITIES SINCE RADIO BEGAN

Radical changes have taken place in radio receiver design during the past year. Circuits and construction are very different from the receivers with which the radio service industry has had its greatest experience. Even more sensational developments with further complications are coming next season. Who will service these receivers? Cer- tainly not the "old timer" who knows nothing about modern receivers! He THIS CIRCUIT ANALYZER can't do it. That is why, right now, AND POINT -TO -POINT there is an urgent demand for reliable RESISTANCE TESTER service men with up -to- the -minute knowl- INCLUDED F/ZEE- OF EXTRA CHAR edge of modern radio receivers. Such GE _4-1-s Cr men can step right out and earn up to FOUR LAt1GE KITS $3 an hour doing nothing but pleasant Of HOME PRACTICE service work in the better homes around EQUIPMENT town. No Past Experience Needed Past experience actually counts for little IT'S JUST AS SIMDL- AS II-415 NpW THE SET r ' $ p at this time, because the swift changes in OF COURSE SOUNDS GREuT 1)1').' I MADE I8 Jf. TWO OTHER MEN .', - 1 receiver construction have made knowl- HAVE TRIED TO' ',I , I CAN FIX IT our ' t THERE'S NOBODY - edge of old equipment practically useless. COULDNT DO IT - FIX IT 1 U ELSE IN TOWN `"1 Even though you may not know one tube WHO CAN FIX f from another today . . . still, you can _ -__- , I a' THESE NEW - take R.T.A. training and make more SETS money servicing modern radios than ir: MI I most of the "old timers" are making. efAlk r_ II / Ç \ R.T.A. graduates are doing it every day. - 7 Many of them are making more money Keeps Ahead c as R.T.A. Certified Radio Technicians R.T.A. Membership You of Competition than they ever made in their lives before! With tour enure of training, and without extra uist, ou get a valuable lifetime membership in R.T.A. This gives you a big advantage over ordinary service men Be An R. T. A. Man and You'll Be . because we constantly furnish advanced information to our members ... informa- the One Man in 1000 tion that puts money in your pocket while the other fellow is stumbling around in R.T.A. training Hill equip voti to give fast, the dark. complete service to any radio receiver built. To Start You Making Money Right Away The jobs that puzzle and sometimes baffle the Quickly following your enrollment for training with R.T.A. you get, without extra usual service man will be simple as "A.B.C.rr cost, the R.T.A. Set Analyzer and Resistance Tester ... the handiest piece of portable to you ... when you become an R.T.A. Cer- service equipment ever de- tified Radio Technician. It is very possible that vised. Instantly helps you SEND you will the only service man in your local- locate the COUPON be trouble in any A. G. Mohaupl, Engineer ity able to quickly diagnose and quickly repair type of receiver, old or Radio Training Assn. of America the new types of radio receivers. Be the one new, and shows you pre- Dept. RC51. 4513 Ravenswood Ave., Chicago, III.

man in 1000! You car. cisely what to do about it. I year. Mr. )Iobauit: l'ha - send me your free book of farts about d io oiportuui t ir. and how I , rake big money quickly. Also ,91 i t horn I obi a ln your Sett Aeunrer and four big eSVeri- RADIO TU LINING mrntaÌ Duaux -1ÌtEE OF EXTRA CILtlu:E. Name ASSOCIATION of AMERICA A.klre 4513 Ravenswood Avenue CHICAGO, ILLINOIS c"s State

Please Say That You Saw It in RADIO -CRAFT 390 RADIO -CRAFT for JANUARY. 1935

The Last Opportunity You Will Have to Order The 1935 Manual AT THE SPECIAL Pre -Publication Price

NO other radio book in history h comparable to the 1933 OFFICIAL RADIO SERVICE MANUAL. In contents. in style of printing. in grade of paper. in illustrations, there has never been published such a comprehensive volume. V. The 1935 Manual contains over s thousand pages -yet it Twill be only 1% inches thick because it will he printed on a special Bible stock which is an exceptionally good stock. yet one of the thinnest and most durable papers. This new Manual will be voted as the most authentic and elaborate service guide ever used in the radio industry. Service Men and dealers who use this 1935 Manual will be astonished by finding in it such a wealth of profitable service information which has never been previously made available. Contents Reveal Important Chapters in the Contents of the 1935 Manual 9 x 12 Over 1.000 pages full of diagrams and essential hdornrat inn of manufactured receiver-only data of real use in servicing is included. This ben- is inches Manual really panatela sleeve It will he extremely thin and I i ght as !yell. Volume V mitt loues where the preceding manual left off- -none of the circuit i unfelt -IIml have ever appeared irr any laeeious volume. of the OFF'IDIAL RADIO SERVICE MANUALS. Marin einults of extremely old sets not merino:1y available are included. Service Men know ever; radio .et Iras eertaln weak points which are really the earl, of troubla Thick Wirer ever the Information could be obt ained, thr,e weakne -ses with their cure, are printed right with the eireu it a. This is an entirely new and valuable addition to the Manual. All the litre., receivers are included all -nave sets. short -wave sett, auto-radio sets. ml dgel and r rear -box set.. et., a titi! a, P. A. amplifiers and equipment. and r menial testin g nd servicing Instruments. The cumulative index Is even more complete than before: including cross reference to sets sold under different name. and Upe SET SERVICING numbers Identical t it h circuits pr loud in this or previous volumes. Volume V Includes reiteence vdata: .socket layouts; I. F. data voltage data; color rodes of Authentic servire information found In ring. cable, rte.: and the purpose of each tube in the .,et Is clearly indicated o the 1935 Manual of a thousand pears the diagrdiagram. Tube data on latestr. and all previous Utes will be included vera all types of radio receivers in use to facilitate servicing. Free quest iota and :maser service-aa Included In our last today. The material will be extremely three manuals. valuable to every Dealer end Service Man. On the diagrams of the receivers. Three Big, Special Offers -See Coupon wherever appear voltage read- possible. In the coupon below will be found the same three special offers as they appeared In ings of socket uonneet isms, inter- tubes. our recent circular. Here is the last opportunity for you to v a few dollar. by mediate frequencies, trans farmer data. taking advantage of our PRE- PUIt1.1CATION OFFER- -BUT -YOU MUST ORDER alignment details. scone pia of NOW before the book is published -about Dee ember 1a. (heck the offer In the coupon trouble and other valuable service sautes. most convenient to you and mall It to the publishers today. DON'T DELAY!

PUBLIC ADDRESS OVER 1,000 PAGES The many Pages on new. outstanding developments in Public Address Installa - Over 3,000111ustrations. Flexible, loose -leaf covers tion and Service will be bond helped to Servit e Men and P. A. speclolists. Surir prominent features os class A and Size 9 x 12 inches - yet only 11/4 Inches thick It ampi lflr'rs -- single and dual chancel systems-alteuuators. and mixers-super- power stages - pre -amplifiers and other commercial desires available for public GERNSBACK PUBLICATIONS, Inc. address and call work, will he found in 99 Hudson this Street New York, N.Y. Complote reference volume. 7 GERNSBACK PUBLICATIONS. INC. 99 HUDSON ST.. NEW YORK. N. Y. RECEIVERS Gentlemen: -Herewith is my remittance for S to cover the pre. ALL -WAVE Publication mire for one ropy of the 1935 OFFICIAL RADIO SERVICE. Information reltt ive to short waves 1a.we MANUAL. the regular prim of which Manual is $7.00. I have marked In the found their way into the 193; by topul. square below the offer chosen. It is distinctly understood by me that. should this Manual Inc offered demand. The numerous all -wove recene, r for sale within a year by a reputable mall -order bows or dealer far less than this amount. you the difference to me. now being sold by all tin will return Practically I understand that the new Manua! is to be published about October 15th. large radio se manufacturers are includ- On all three offers the postage Is prepaid the publishers. This Is an additional ed. For then sets wherever posslbLc. CLIP saving for you. le complete aller Ina details .for all OFFER NO. I hands th.- aro included in addition to THIS I enNose 55.00 In full (during the month of September. 1931). for service material listed for other sets. the tut al prim of the 1935 Manual. This me $2.00. OFFER NO. 2 COUPON I enclose $3.00 now (during the month of September, 1931). I will pay the oostman $3.00 when the 1935 Manua Is delivered. This saves AND me $1.00. AUTO -RADIO RECEIVERS OFFER NO. 3 I enclose $6.50 now (during the month of September. 1934), and I am No servire manual meld he complete MAIL to get FREE. a one -year subscription to RADIO -CRAFT Magazine. without a section devoted In auto -radio. This saves me $3.00. All available servire information on new auto -radin sets has been included. Ft-nm TODAY! NAME this section alone Servire Men maid derive sufficient knowledge to venture in ADDRESS a specialty field -that of servicing only auto- radios. It is one of the biggest CITY STATE opportunities in radio today. t [intent uee should be made In U. S. or International Money Order: we also pt personal cheeks. If you remit In cash. or should you send new and unused l s tamps. which we also accept, be sure to register your letter.) L J Please Crrfr Thnf l'al Saw It in RADIO -CRAFT ädio FOR TOIL aff

SERVICE MAN . DEALER RADI07RICIAN "Takes the Resistance out of Radio"

Vol. VI., No. 7, January, 1935 Edisorial ONl_es: 99 Hudson St., New York, N.Y. HUGO GERNSBACK, Editor SHORT -WAVE APPLICATIONS

An Editorial by HUGO GERNSBACK

HE short -wave art today has assumed such vast found in "radio therapeutics." Less than 10 years ago it proportions that it is difficult even for the man well was discovered by physicists that short waves could be used versed in radio to keep track of all its ramifications. to produce artificial fever in patients simply by placing Each month there are new developments and appli- them directly in the field set up between two plates ener- cations in this fastest growing branch of radio. gized by a short -wave transmitter. The artificial fever, In short -wave reception we have, today, close to 10,000 which can be controlled accurately, thus is induced in the short -wave stations which transmit 'phone or code. The patient and many diseases are today treated by such short- largest and most powerful transmitters are those that send wave therapy. This particular branch of short -wave radio international programs of the entertainment type which is still in its infancy, and much work remains to be done. in field. One can be heard all over the world. Incidentally, it is a pecu- Many surprising things will come about this liarity of short waves that the effectiveness of the trans- of them, for instance, has to do with the extermination mitter is not realized within about 500 miles of the trans- of insect pests whereby the larvae are killed by the direct mitting' station, but becomes apparent as the distance in- application of short waves. This can be accomplished right creases (up to a certain point). in fields where crops are grown and no doubt this branch of However, while the average man associates "short waves" short -wave radio will, in due time, reach vast proportions. only with the reception of foreign programs, and while no Geo -radio is still another branch of short -wave radio by doubt this is their foremost application, newer applica- which geologists and others make use of the versatile tions are cropping up every day. short waves to explore the ground for its mineral contents. Short -wave transmitters are used, for instance, for com- Nowadays, new mines are no longer discovered by the hit- mercial purposes such as transatlantic and overseas short- or -miss procedure, but the prospecting miner uses short- way telephony. Other radio transmitters are required in wave radio equipment and systematically explores his ter- the ship -to -shore telephone service. In fact, there are to- rain by noting the reflection, refraction and absorption of day, 21 passenger liners equipped with short -wave tele- short waves sent out by a miniature, portable transmitter. phone whereby, for a reasonable sum, the passenger at sea Excellent results are had by this method, which is always may telephone from his own ship to almost any part of certain, and cheaper in the long run. In this country alone, the world, via short waves. Then, of course, there are the the Federal Communications Commission set aside wave- many thousands of stations operating daily in airplane lengths just for the purpose of radio exploration of this work, for communication purposes between ground and type. Much is to be expected from this branch of radio 'plane, and vice versa. There are also over 50,000 short- in the near future. wave amateur transmitters scattered all over the world. These items do not by any means exhaust the list because Most of these use code, but 'phone is on the increase. there still are numerous other applications of short waves, An entirely different field of short -wave radio operation many of which have, as yet, no practical value. For in- is that of "facsimile" transmission, or the sending of photo- stance, down in the micro short wave region, that is, in the graphs and the like. The facilities of such transmitters are spectrum where the wavelengths are only 4 inches (about being utilized more and more by most of the larger com- 10 centimeters) in length, the action of the radiations be- panies. This branch of short -wave radio has been greatly comes entirely different. As we all know, the usual short developed in the past few years. Since it is now possible and ultra short waves penetrate brick and wooden to transmit a photograph from London to New York in the buildings just as if they did not exist, but down in the short time of 15 minutes, important press photographs are micro short waves, conditions suddenly change, when it is now flashed across oceans at lightning speed and record no longer possible to send the waves through solid build- reproduction. Witness the recent photo-radio service of ings; nor do these waves follow the curvature of the earth the assassination of King Alexander where the actual views as do their sister waves. Indeed, micro waves behave much of the assassination were published in the morning news- like light waves, and transmitter and receiver must be in papers in New York within 10 hours after the assassina- sight of each other -the signals will not ordinarily carry be- tion took place in Marseilles, France. low the horizon. Television, of course, is accomplished by means of Senatore Marconi is reported as pursuing experiments short waves, and while the final word has not yet been toward utilizing these micro waves in "radiodynamics," or spoken, one thing is certain: when we finally have regular the control of mechanical devices at a remote point by television service, it must be via short waves and most prob- means of radio waves. Reports so far received seem to ably ultra short waves, or the wavelengths below 6 meters. indicate that results as reliable as those obtainable over a And here it might be well to state that the further down in regular copper-wire line may be secured by using these the short -wave spectrum we go (the higher the frequency) "beam" waves, which may be directed like a beam of light. the less strong becomes static interference until, finally, Still further down, in the micro -wave band we come to there is reached a point in the "micro short-wave" band a point where the so- called "radio" short waves are no where static is entirely absent. This highly important longer really radio at all. Here the frequencies merge advantage will be a boon to television because the use of into those of heat waves, and behave exactly as such. Very such micro waves will enable us to have images unmarred little is know about these borderline waves, and there is by static. no gainsaying that some of our greatest surprises in radio Still another application of high- frequency radiations is will come in the application of these microscopic waves!

391 THE RADIO MONTH

will be merchandised, it is expected conversations with de Forest which that only a single design, approved by convinced me that he did not know of the government, will be manufactured or understand the production of radio by all the manufacturers. This is in frequencies by vacuum tubes. I have line with the present plan in Germany therefore been amazed at the fact that to make "Hitler's own" receiver (a set the highest court has previously upheld of small size, and relatively insensitive the de Forest patent." so that only local programs can be Professor Pupin sums up his letter picked up) the distinctive set. Thus, with the following remarks: "The the citizens of Germany will be pre- court holds Dr. de Forest to be the invented from hearing the powerful ventor; the scientific world is a unit transmitters of Russia and other for- holding Armstrong to be the inventor." eign countries from which undesirable -and -" ... I have never heard of any programs might be heard. scientific opinion of recognized weight supporting the de Forest claims." "Dr. Langmuir, a recent Nobel Prize man, was one of the claimants of the "FINAL" ACTION same invention which was under liti- gation between Armstrong and de For - IN RADIO est for eighteen years. FEED "Third, the famous radio engineer, -BACK CASE Mr. Round of England, one of Mar - The latest move in Germany is the establishment of THERE have been so coni's right -hand men, also sent a huge network of television transmitters for dis- hearty bursing propaganda. many "final" decisions approval of the decision of the Court in the long- drawn -out of Appeals of the Second Circuit. case between the de (Which gave the decision to Armstrong HITLER Forest and the Armstrong interests re- -Ed.) Both these letters appeared in garding who actually invented regener- full in the Columbia Alumni News of ation that there is no wonder that cries Sept. 29, 1933. TAKES UP of "wolf, wolf" have been heard from "Fourth, the very significant fact TELEVISION all sides in the radio industry. that Cyril Elwell, who was the chief It will be remembered (RAnco- CRAFT, engineer of the Federal Telegraph WITHIN the past August 1934, page 70) that the United Company, the company employing de month, RADIO- States Supreme Court, presided over Forest at the time he claims to have CRAFT has re- by Judge Cardoza decided that Lee de made the invention, supported Arm- ceived a report Forest was the inventor, and held that strong, as did Professor Leonard Ful- that Chancellor Hitler is preparing a de Forest had heard a "clear hetero- ler, now head of the Electrical Engin- huge network of television stations in dyne" before Edwin H. Armstrong, eering Department at the University Germany which will probably be used then a student at Columbia University, of California." as an aid to broadcasting as a medium had struck upon the same phenomenon. It seems that while Dr. de Forest has for disbursing Nazi propaganda. Major Armstrong recently petitioned the upper hand as far as legal proceed- As mentioned in the report, Hitler's for a rehearing of the case with the ob- ings are concerned, he must now vindi- plan includes the making of cheap tele- ject of reversing the Supreme Court cate himself in the eyes of Professor vision sets available throughout the ruling, and the latest decision of the Pupin and his supporters. And so the country. This will make Germany the court is a denial of that application. Feed -back case seems no nearer to an first nation to establish extensive tele- In addition to the legal actions which end, in one sense, than it has been for vision programs on a large scale. have taken place, a heated argument the past ten or twelve years. Short waves will be employed for has been progressing in the New York these transmissions, so that the re- Times, between Professor Pupin and This is how one of our staff artists visualizes the quired number of channels can be ob- Dr. de Forest concerning the opinions arguments in and out of court concerning the "re tained. In this way, with numerous of the former who has rallied to the generation patents." stations properly spaced, it is expected support of his colleague, Armstrong. that even the outlying districts will be This argument has become heated to adequately covered. the point where many bitter words are Television transmitters manufac- being said by both parties involved. tured by the Baird Television Co. of In the latest epistle by Prof. Pupin, England are said to have been ordered over half a column in the Times, is de- by the German officials. These trans- voted to a "tabulation" of the names of mitters are of special design to cover famous scientists and radio engineers the conditions required for each indi- who take sides with Armstrong. So vidual installation. They include famous an authority as Dr. Irving sound facilities as well as the vision Langmuir is quoted as having made the units, so that the voices of Hitler and following statement: his Nazi orators will be heard, in ad- "Ever since 1913 when I first learned dition to visualizing the speakers, of your (Armstrong's) pioneering work themselves. in this field, I have known the great While no actual data is available value of your contributions. On sev- regarding the type of receivers which eral occasions after that I have had

392 RADIO -CRAFT for JANUARY, 1935 Radio is now such a vast and diversified art it becomes necessary to make a general survey IN REVIEW of important monthly developments. ADIO- CRAFT analyzes these developments and presents a review of those items which irterest all. RCA MAKES A POLICE CAR BUSINESS TALKS TO STATEMENT AUSTRALIA ITF the financial position of IN A spectacular demon - the largest radio corpor- stration, one day last ation in the world has month, engineers in any bearing on the con- Schenectady, New York, dition of the radio business, then their working on a new type of police latest financial statement, issued last "prowl" car accomplished two -way tele- month, covering the first three quar- phone conversation with Sydney, Aus- tralia, with cooperation ters of 1934 must give other manufac- This is what happens when you drop a radio trans- the of station turers an optimistic outlook for the mitter from a height of I mile. W2XAF. future. The conversations were carried by A glance at the chart shown here, ultra -short waves from the car to the which is reproduced directly from their control board of WGY and W2XAF, printed statement, shows that the total STRATOSPHERE where incoming signals from Australia gross income for 1934 is well above the were also being relayed. By carefully same figure for the equivalent period of RADIO regulating the incoming and outgoing time in 1933. signals the two -way conversations were Also, the part of this income which EQUIPMENT made possible. is applied to surplus (the amount left The police car was one of many new when all deductions have been made - RADIO has played an developments in police radio which will Ed.) has been substantially increased important part in the be first used in Boston, Mass. as indicated by the chart. numerous flights A few words about the car and its While these figures do not have a made recently by equipment might be of interest. The direct bearing on the radio business as scientists in their efforts to learn more car is a light sedan, bearing no evi- a whole, it is safe to assume that it is about the mysterious cosmic rays. It dence of an antenna or other special indicative of a gradual rise out of the was more than an ordinary aid to Pro- features. A French -type phone is in- depression slump for the majority of fessor Picard in his flights, and has stalled in a convenient position on the enabled him radio organizations. to communicate constantly instrument panel, while the 8-meter In connection with the Radio Cor- with the ground -thus facilitating the transmitter is located in the rear trunk. poration of America, or rather its sub- flight and subsequent landing, as well The rear bumper is mounted on insu- sidiary, the RCA Victor Company, as keeping the ground informed of lated brackets, and acts as the trans- which has been extensively advertised progress of the scientific investigations. mitting aerial. as the largest radio manufacturer in An interesting result of the recent The receiver is kept in operation at the world, we note with interest an ad- flight conducted by the National Geo- all times, according to regular "police e vertisement which recently appeared graphic Society and the Army Air practice." When the car is called by in the London Times, in which Phillips Corps, is found in the photo of the headquarters and the 'phone is lifted Lamps Ltd., a European concern, radio equipment shown below. This from its hook, the mobile transmitter, claims in bold -face letters to be the tiny 8 -watt transmitter which was used on a different wavelength from the "world's largest radio manufacturers." during the flight was dropped through one at headquarters begins to function We wonder who is correct? Is RCA space a mile or more and was recov- immediately. This method permits Victor or Phillips the world's "largest "? ered last month by the NBC, which co- "duplex" conversations between the operated with the National Geographic (Continued on page 423) Society in broadcasting the signals The Radio Corporation of America is evidently from the gondola of the balloon. An engineer at Schenectady, N.Y., talking to c irnbing well out of the mire of depression accord- Australia from a new type of police car. ing to these figures. The battered transmitter which is now on display in the studios at Radio City, illustrates a phenomenal incident. 1934 1933 Panels, transformers, resistors, meters, ---- sockets, condensers, and virtually every $52.648.007 part with one exception, was completely wrecked by the drop through space. $41344.550 Oddly enough, the one part which remained intact is a vacuum tube. Even the socket in which the tube was mount- e1 ed was cracked, but the tube, with its "A46.8611 1 58,057813 fragile glass envelope withstood the shock.

RADIO -CRAFT for JANUARY, 1935 393 SHORT-WAVE RADIO PICTORIAL

TO facilitate the work of policing the numerous channels throughout the broadcast and short -wave bands. the Federal Communications Commission has just purchased six of the devices shown above. These portable frequency monitors are designed for use in special trucks which travel around the country checking the accuracy of tuning of the various broadcasting stations. Iw e Each of these consists of a highly stabilized ¡SHORT WAVE TRANSMITTQR quartz crystal oscillator, a harmonic generator and a radio receiver. They are accurate to three parts in a AND RECEIVER million.

CONTRARY to popular understanding in the U.S., radio amateurs across the "big pond' are showing much interest in ultra-short waves. The interesting F! photo on the right depicts an elaborate mobile instal- HERE is another use for ultra - lation of an English amateur (G5BY). The "rig" con- I short waves. The Japanese gov- sists of a 5 meter transmitter and receiver, each with ernment is at present trying to a separate aerial for duplex transmission. The trans- introduce radio telephony on the mitter is mounted at one end of the box, while the important railways, for signal - receiver occupies the other end. The antenna poles can be removed while the car is in motion. liling and communication to nearby towns and cities for the con- THERE seems to be no limit to the height of fre- venience of passengers. The quency which can be utilized for radio communication. photo above illustrates some of Several years ago, transmission on 5 meters was a most the experiments which were con - unusual and mystifying study, and was utilized mostly ducted recently in duplex trans - for spectacular demonstrations and laboratory experi reception. Note the ents -today it is used for commercial communication. ____J mission and The photo below shows an apparatus set up in the apparatus. Bell Telephone Laboratories for transmitting and receiv- I'll, t,, A. N. 3f irrar ^.. ing waves of 60 centimeters which is equivalent TO the "round to flier, about 24 inches. The specially designed receiver has 4 the world" tuned circuits for detector tuning. whether he con- l'Iwtk.: \ \ca inLuu :ï: \\'izele-a \Vs'ild; 13e11 Tel. Labs. templates a speed record or simply a leisurely flown Í tour, radio communication is perhaps the most essential and most used instrument on the plane. This was realized by Dr. R. U. Light, who recently started on a flight in a Bel - lanca monoplane equipped with two -way r a d i o equipment. The transmitter is rated at 75 watts and covers the c o m p l e t e range of frequencies of 330 to 14,000 kc. The receiver is also of the wide range variety by the use of a special coil changing mechanism. All of t h e equipment, including t h transmitter operated from the plane's 12 volt storage battery.

394 RADIO-CRAFT for JANUARY, 1935 i

TELEVISION, as a commercial product -to be used and enjoyed as a source of entertainment by the general public -is fast approaching that stage of development where actual instruments will be sold in stores. This fact was brought out recently, at the New York Radio and Electric Show -where the instruments shown above were demonstrated. A more complete description of the technicalities attached to this system for sending and receiving pictures appeared in the December, 1934, issue of RADIO -CRAFT, page 330. The receiving set appears at the left in the above photo, while the transmitting devices are at the right.

1-IE two photos, above and to the left, show a new installation just completed in Paris, for providing radio aid to the Prefecture of Police. The transmitting car, with its large aerial structure is shown above, while one of the patrol cars equipped with receiving apparatus appears at the left. While this installation is, no doubt, a distinct departure from previous practices of the police department of that metropolis, we cannot help but remark at the antique appearance of the auto receiver, with its large cabinets for speaker and FRENCH set, and the pretentious appearance of the aerial POLICE of the transmitter equipped truck. A comparison of recent photos of American police radio instal. RADIO lations, which have appeared in RADIO- CRAFT, and these pictures, indicate how far advanced is American equipment. The incident shown in these photos is the inaug- uration of the new cars, in the courtyard of the Prefecture of Police.

THE Radio Doctor has made his appearance in far off Australia. In the isolated mission stations and settlements "out" from Cloncurry, it often took weeks to get a message through, by water or land. Now, when medical aid is needed, the radio equipped planes of the Aerial Medical Service can reach a patient in a matter of hours. The photo below shows the flying doctor attending a patient, while in the picture at the right is one of the short -wave transmitters in actual use.

l'hui of \VirrIe ., \Verkls.

1 R. CARL SPITZ, inventor of the device appearing at the right, is shown explaining its operation. It is a recorder designed to indicate constantly the exact location of an airplane in flight. A small light, actuated by short -wave radio signals SHORT WAVE moves across a strip map of the AIRCRAFT plane's route, thus keeping track of its movements. The device is in- PLIGHT tended to eliminate some of the RECORDER hazards of blind flying for mail and transport lines. Some of the equipment is seen behind the inventor.

RADIO -CRAFT for JANUARY, 1935 395 HI- FIDELITY ON

There is a high -fidelity broadcasting station, operating on 1550 kc. -just below the broadcast band, which is aiding listeners in obtaining lifelike reproduction. This station, W2XR, is blazing new trails with daily broadcasts that cover the entire audio frequency range. Its marvelous quality is causing nation -wide comment, and this may be attributed to the unusually high standard of equipment employed, besides the unusual precautions to ensure high quality. Fig. A High -fidelity piano music broadcasts aided by a crystal mike.

N THIS present era of high -fidelity ascertained that realism in reproduc- nel 20 kc. wide, this station has a flat one hears much about new receiver tion can only be attained when high - frequency characteristic from 20 to I design which will permit the attain- fidelity is attained, and, also, inasmuch over 15,000 cycles, handling at least ment of the ultimate in radio repro- as high -fidelity reproduction can be ob- 91/2 octaves of the musical scale! The duction, but little regarding the broad- tained when frequencies upwards of quality of the broadcasts from this sta- caster's efforts to aid in this respect. 10,000 cycles (at least up to 7,500 tion is so uncanny that it completely While a 19 -year period of radio broad- cycles) are broadcast, received, and re- upsets preconceived ideas of high -fidel- casting development has given the aver- produced.- realism or natural repro- ity and, because of the favorable com- age listener -in much to be grateful for, duction becomes contingent upon ment, three other stations with similar there has always been that feeling whether these conditions are satisfied. equipment are now under construction (when listening to the majority of sta- With manufacturers now producing (one each) in California, Missouri, and tions) that there is something lacking high -fidelity receivers, the listener may Connecticut. John V. L. Hogan, noted to lend realism to the quality of the wonder where the required "wide - engineer and past -president of the In- broadcasts. This may he attributed to: range" broadcasts may be obtained. stitute of Radio Engineers, developed the tonal (audio frequency) range of Such a station is in existence in New W2XR which is destined to make his- th, transmitting equipment; the gov- York City; its call letters are W2XR, tory as the first real, licensed high - ernment's regulations in regard to ad- and its daily high -fidelity broadcasts fidelity broadcast station in the world! herence, within 10 kc, of the frequency have been amazing to all who have lis- So complete is the equipment, and of assigned to the broadcast station (see tened to this station. (The station is such fine engineering design, that "Problems in High- Fidelity Design," really a vast research laboratory where amongst the radio engineering fraterni- December 1934. RAD:o- CRAFT) ; and, by Mr. Hogan and a large staff of engi- ty this station is considered as being a no means least of all, the receiving set neers are putting the finishing touches model installation. No ordinary type which, with the exception of the new on their facsimile and television de- of microphone or auxiliary pick -up de- high- fidelity receivers, restricts the re- vices, as well as the high -fidelity broad- vice is employed. Crystal microphones production to below high -fidelity level. casting.) are employed exclusively, and the These limitations permit only a fre- Broadcasting on 1,550 kc. (193.5 "wide- range" response of this type of quency range of from 20 to 5,000 cycles meters, just below the broadcast band), unit is an established fact. In Fig. A (maximum) to be broadcast and re- and authorized by the Federal Com- the studio can be seen and the crystal ceived. Since it has been definitely munications Commission to use a chan- microphone on a stand, at the extreme

Fig. 6 Fig. C The bank of transmitters at W2XR for all types of broadcasts. Mr. Hogan at the facsimile transmitter, and facsimile sample.

396 RADIO -CRAFT for JANUARY, 1935 SHORT WAVES

No hit -or -miss methods, or conventional design will be found in this station. Results are obtained only through sound engineering, good design, and continuous research towards improving the quality of transmission. The station is equipped, in addition to the regular quality broadcasting paraphernalia, for facsimile and television transmission. Only crystal microphones and pickups, resistance- coupled amplifiers, and cathode ray tubes for monitoring, are employed.

Fig. D Visual and audible monitoring, with Mr. A. A. Barber, sound engineer. right, picking -up piano notes for broad- movie projector, ultra -short wave trans- this station is not the result of hit -or- casting. So lifelike is the transmission mitter (46 megacycles or approximate- miss methods, but rather due to sound that even on an ordinary receiver the ly 6.3 meters), and a facsimile and tele- engineering, good design, and long re- quality of reproduction is superior to vision transmitter (2,500 kc.). search. The combination of crystal mi- that of ordinary broadcasts. With a From the description given thus far, crophones, phonograph, pickups, resist - high -fidelity set the reproduction be- it can readily be seen that W2XR dif- (Continued on imite 426) comes so realistic that the listener actu- fers greatly from most radio broad- ally feels that he is present in the cast stations. Few, if any, have so studio. versatile an array of equipment. Some While the station is licensed to use few months ago Mr. Hogan demonstrat- 1,000 W. it only broadcasts 350 W. of ed to an amazed engineering group an power. Nevertheless, it is heard at exceedingly simple facsimile receiving very great distances, Seattle, Washing- and transmitting system (described in ton, as well as all through the middle July 1934 RADIO- CRAFT, "The Radio west, reporting excellent quality and Pen," page 13). Its applications are reception. The bank of transmitters in multitudinous and can be employed, if this station (W2XR) is shown in Fig. desired, along with broadcast talks to B. (Note the motion picture projector illustrate certain essential points. How- in the foreground, used for television ever, at the present time the equip- broadcasts of motion picture film. The ment is applied only to commercial use. equipment necessary for transmitting An idea as to the simplicity of the television impulses must be of an ex- transmitter, apparatus, and a sample ceedingly "wide- range" nature, gener- of the pictures it can send out into the ally from 15 to over 50,000 cycles.) either, may be gained by reference to The equipment, as seen in this photo, Fig. C. Mr. Hogan is shown operat- from left to right, are: high -fidelity ing the machine, a duplicate of which transmitter (1,550 kc.), television is being installed at Station WTMJ in transmitter (2,050 kc., designed for Milwaukee. Fig. F A control panel for correcting the deficiencies in modulation of 50 kc. each side), sound- The high- fidelity broadcasting from recordings. Photos: Hannan Fig. E Fig. G The equipment for phonograph renditions using crystal pickups. Daily quality tests are made on the equipment by means of tuning forks.

RADIO -CRAFT for JANUARY, 1935 397 + QUIP ir HOW TO BUILD THE -CONDENSI: POWER `!NSER1 SWITCH SWITCH ( "FOUR -IN -TWO" SHORT -WAVE ELECTRIC SET This amazing little short -wave and broadcast set incorporates the functions and possesses the efficiency of four tubes, yet uses only two. It is remarkably simple and economical to construct.

Fig. A. The chassis includes a spare coil rack. J. T. BERNSLEY

WAS IT with the realization that short -wave set con- On broadcast tests, conducted in a steel office building in structors preferred a set that is economical to build New York City, stations 1,500 miles away were brought and operate, and employs a minimum of tubes with in with fair loudspeaker volume. a maximum of efficiency, that this receiver was designed. On short waves police calls all over the country were Before discussing the relative merits of the circuit, and more than comfortably heard on the loudspeaker. At the the theory involved, it would undoubtedly be of greater time the receiver was completed and first tested some interest to the constructor to learn, first, just what this police stations in the middle west were tuned in. On that set can do. Well, in the first place, it will operate a loud- particular night they were extremely active and engaged speaker (magnetic, or permanent magnet dynamic types) in pursuing the late Dillinger. It. was a distinct thrill to on most signals transmitted within a radius of 750 miles. listen -in on the various stations in numerous cities who were cooperating in this almost nation -wide man hunt. SPARE COSL Foreign broadcasts, on short waves, were received from RACK \ numerous countries. At the time of these tests LSY in Argentina, South America, was heard with good loudspeaker volume. Also YV3RC, in Venezuela, with exceptionally good volume. DJC, in Berlin, Germany, was tuned in (on loudspeaker) consistently for several weeks. Amateur radiophone stations in abundance, to delight any ham or other interested listener, were received in the various bands assigned to amateur phone communication. Using only two tubes, and of the most unique types that have ever been produced, it is possible to obtain full four - tube results. The set is distinctly designed for electric operation, either 110 V. D.C., or A.C. (of any frequency), but only this combination of tubes, as will be explained later, will permit such operation -and the equivalent performance of four tubes. By using conventional plug -in coils the complete short -wave range of from 15 ANT to 200 TRIMMER meters is covered. COND Broadcast Reception, Tool However, the necessity for ever- changing coils to cover various wave -bands is reduced Fig. B. above. considerably by a special Rear view showing parts layout and workmanlike appearance. Feature included within the tuning circuit. This consists (Confirmed on page 424)

Fig. C, left. Bottom view. Note reg fion and vol. control. Fig. I, below. Wiring diagram. Operates from 110 volts A.C. or D.C.

AOG M v c. ¢o. C 2MEGs 5 c

A. F. 2 a RICO To - 0.25. 12A7 ONUSCíEr4 MEO. ti

MEG

1 G.F t .MErr l o. ME.

BOTTOM VIEW Y Oe COIL MEG. 325 oMMS - SOCET MF. IIOV.ac: OC

398 RADIO -CRAFT for JANUARY, 1935 THE LATEST IN POLICE RADIO RECEIVERS New miniature police receivers may ante- date present cumbersome models. The new sets are extremely small, light, and efficient.

PORTABLE radio receiver de- without taking the belt off and can The complete equipment of the personal set. signed for use by patrolmen instantly be mounted on a bracket pro- and mounted police has been vided for it on the handle -bars of the perfected by Sol J. Levy, of motorcycle. New York City. The loudspeaker for the motorcycle Weighing only 31/ pounds, the five model is also mounted on the handle- tube super receiver delivers loudspeak- bars. A female plug in front of the er volume on police broadcasts. rider on the machine connects the set The receiver is made in three styles speaker and batteries; plugging in the for patrolmen, for motorcycle men, cord instantly puts the set and speaker and for mounted police. into operation. The motorcycle model operates from The receiver has excellent sensitiv- the 6 volt storage battery supply of ity, being tuned to a fixed wave to in- the motorcycle, the plate voltage being clude only the police calls desired. It supplied by a small motor -generator has an output of 3 watts and can be mounted on the motorcycle supplying clearly heard above traffic noises. 225 volts. The antenna for the motorcycle The receiver proper weights only model is comprised of metal tubing 1% pounds and is mounted on the mounted on the handle -bars, and to the driver's belt. It is easily removable (Continued on page 423)

NEW SHORT -WAVE LINK TO BYRD How the airwaves were made to travel when Byrd talked.

RcA HORT waves carried a two -way conversation between + . CBS T*. .IETTINL RCA : HEADQUARTERS STATION RECEIVING Richard E. Byrd and his mother, Mrs. .RC''._ '4e5MADISONMe. STATO LA Rear -Admiral 4'.. N VC., Eleanor Bolling Byrd, over the ten thousand miles of S HEAD USED ST 14,15 WWN[J. BTO space separating Winchester, Virginia, and Little America. ÌO MEI This interesting exchange of greetings between Mrs. Byrd / TMMiICIKS) / and her illustrious son took place on October 17, during HÉIX6' the weekly broadcasts with Little America conducted by the WABC -Columbia broadcasting network. 'y STÂ.ICiCL N The voice of the Admiral's mother was plainly heard by ` 474 v ú.SN# wINCNE5TER5,f/ millions of listeners when she said: "I am thrilled to hear MALBTnD - 351AGE j tt AT VIINCeES1ERyA. V T.YOCAL" / VA. safe and sound." ARRLOIER that you are back in Little America again CASC This sentence and a number of others were carried to the Admiral via the powerful 20 kilowatt short -wave trans- ',FRANCISCO mitting station of the RCA system located at Rocky Point, TO N V CITY Long Island. The wavelength used to transmit the voice to and from Little America was 25.6 meters or a frequency of 11,830 kc. One of the most interesting and little known facts con- oACITIC ATLANTIC cerning these broadcast programs carried over the CBS OCEAN OCEAN network from Little America is the fact that there are three short -wave "stand -by" circuits always ready to pick TO up the voice from Little America and bring it to New York. tiL40iO1 \ the short -wave signals from Little America, via N Ordinarily 01 I k TRAN SMITTING 4SFANDAV SWW.CIR Buenos Aires, South America, are amplified, the short z AERIAL CUITS(OPTIONAL) waves being picked up on a receiver and immediately 01 VIA HONOLULU 0E VIA SAN FRANCIS. passed through a powerful S -W. transmitted at Buenos co Sw AMSMrtTE0. 03 DIRECT TO RIVER. Aires, whence they are again flung northward with the HEAD I. 5WRECE,vIeG light, and intercepeted at the RCA receiving sta- A(AERIAL OA I speed of ORRE5VrBVW.RE at Riverhead, Long Island. Here the signals are picked 5M FRANCISCO Ì tion TO NEW //OAR up on a special receiver and suitably amplified through sev- CITY 1 L11 TLE AOIr11RAL BYRD RECÉ IVER . (Continued on page 426) AMERICA RADIO -CRAFT for JANUARY, 1935 399 SHORT -WAVE STATIONS OF THE WORLD A list of the important short -wave phone stations throughout the world listed according to frequency. Stations are classified as follows: B- Broadcast Service. C- Commercial Phone. X- Experimental Transmissions.

Wave- I Wave- Wave Call - Leaflets Freq, length Sers- Call Location Freq, length Serv- Call Location Frog,, length Sen. Letters I (lee,, )meters. ice Letters (kc,) Letters - .- tmeterst ice (Flee,) (nanan) is

XGBA Shanghai, China 21550 13.92 B 12R0 Rome, Maly.. 1810 25.40 B HKE Bogoto, Colombia 7220 41.55 VK3LR Lyndhurst, :Australia 21540 13.93 B OER3 Vieunu, Austri, 1801 25.42 B HJIABB Manizales, Colombia 7210 41.60 W8XK Pittsburgh, Pa 21540 13.93 B WI XAL Boston, Ma, 1790 25.45 B YV2AM \laraeaibo, Venezuela 7200 41.60 NAA Washington, D. C 21500 13.95 B TITR SanJose, Posta Rira.. 1790 25.45 B OMB Lima, Peru 7160 42.00 FYA Parie, France 21490 13.96 R F3ICD Saigon, Indo-China 1780 25.46 B HJ4ABB Manlz: les, Colombia 7140 42.02 GSH Daventry, England 21470 13.97 B DJD Berlin, Germany 1760 25.51 13 LU5CZ Buenos Aires, Argentine.... 7080 42.37 WI XAL Boston, Mass 21460 13.98 B GSD Daventry, England.. ; 1750 25.53 B HJ1ABE Cartagena, Colombia 7000 42.86 WKK Lawrencevlle, N..1 21420 14.01 C HRB Tegueigalpa, Honduras 1740 25.5.5 B LCL Jeloyy, Norway 6990 42.92 LSN6 Burlingham, Argentine_... 21020 14.20 l' RRRR Tachkent, L. S. S. R 1740 25.55 B EAR110 Madrid, Spain 6977 43.00 LSY Monte Grande, Argentine... 20700 14.49 C NAA Washington, D. C . 1731) 25.58 B GDS Rugby, England 6905 43.45 GAA Rugby. England 20380 11.72 C PHI Haiaen, Holland 1730 25.58 B KEL Bohm., Calif 6860 43.70 LSG Monte Grande, Argentine... 19900 15.08 (' CJRX Winnipeg, Canada 1720 25.60 B WOA Lawrenceville, N. J... 675.5 44.41 WKN Lawrenceville. N. J. 1982(1 C ...... 15.14 FYA Paris, France... 1720 25.60 B BC2RL Guayaquil, Ecuador 6676 44.93 EAQ Aranjuez. Slain 13 19720 15.21 VE9DR Winnipeg, Canada 1720 25.00 B F8KR Constantine, Algeria 6667 45.00 LS145 Hurlingh:rn, :Argentine 19650 15.27 C VE9JR Winnipeg. Canada 1715 25.60 B HC2RL Guayaquil. Ecuador 6606 45.00 LSF Monte Grande, Argentine... 19011 15.31 C . FYA Paris, France 1710 25.63 B YNCRG Granada, Nicaragua 6664 45.00 WOP (keen Gate, N. J 19380 15.48 C KIO Kabuki', Hawaii 1680 25.68 X IAC Piza, Italy 6050 45.10 FTM St..Asist% France 1935.5 15.50 C CT3AQ Funchal. Madeira 1180 26.83 B PRADO Rioinmba, Ecuador 6620 45.30 WKF Lawrenceville, N. J 19220 15.60 C GBP Rugby, England. 0770 27.85 C RW72 Moscow, P. S. S. R 6611 45.38 GAP Rugby, England 131160 15.66 ( JVM Nazaki, Japan.... 0740 27.93 C REN Moscow, L. S. S. R 6610 45.38 6 Rugby. England 18970 A 15.81 ( WNB Lawrenceville, N..1 (1675 28.10 C HJSABD Manizales, Colombia. 8500 46.14 PLE Bandoeng, Jura 188311 15.93 ( JVN Nazaki, Japan...... 0660 28.14 C HJIABB Barranquila, Colombia 6447 46.53 GAX Rugby, England 18680 16.06 X FYB Paris, France 11578 28.361 B HJA3 Barranquilla, Colombia.... 6425 46.70 GAU Rugby, England 18620 16.11 ( WOK Lawrenceville, N. J .. 0550 28A4 C W3XL Bound Brook, N..1 6425 46.70 FIS Saigon, Indu- ('hint 18345 16.35 C GBX Rugby, England 0.530 28.49 X HIZ Santo Domingo. Dom. Rep 6320 47.50 WLA N. J 18340 16.36 C Lawrenceville, VLK Sydney. Australia 0525 28.50 B HJ3ABF Bogota, Colombia 8275 47.81 GAS Rugby, England 18310 16.38 C YBO Medan. Sumatra 0430 28.76 C MIA Santiago, Dom. Rep 6272 47.84 .TO St. Anise, Frmce 18250 16.43 C XGW Shanghai, China 0420 28.79 C HJ3ABF Bogota. Colombia 6250 48.00 GAW Rugby, England 18200 16.48 C KES Bolin:., Calif 0410 28.80 X OCN Lima, Peru 6235 48.10 >MC Bandoeng, Java 18135 16.54 C PDK Kentwijk, Holland 0410 28.80 C CJRO Winnipeg, Canada 6150 48.78 .SY3 Monte Grande, Argentine... 18115 16.56 C LSX Monte 03511 Grande, Argeroile . 28.99 C YV3BC ('aralias, Venezuela 6150 47.87 GAB Rugby, England 18040 10.6.3 (' ORK Rnysselede, Belgium 03:311 29.04 B KZRM Manila, P. I >CV 6140 48.86 Knotwijk, Holland 17810 16.84 (' LSL2 Ilurlinghann, Argentine 0300 29.13 C W8XK Pittsburgh. Pa 3SG England 6140 48.86 Davcntrv, 17790 16.86 B PMN Bandoeng, .lava 0260 29.24 C ZGE Kula Lumpur, Feel. Malay W3XAL Bound Erook, N. J 17780 16.87 B LSK3 Hurlingham, Argentine 9,!.51 29.27 C States W8XK 6135 48.90 Saxonburg. l'a 1778(1 11.87 B PSH Rio de Janeiro, Brazil.. 1622(1 29.35 C JB Johannesburg, U. of South N9XF Downer's Grove, III 1778(1 16.87 B ZFB Hamilton. Berme 6 0055 25.57 C Africa 6122 49.00 W9XAA Chicago, Ill. 17780 16.87 B LSN Buenos .Airre, argentine !601 30.03 B ZTJ Johannesburg, . of South 'YA Paris. France l 17775 16.88 B GCU Rugby, England 9950 30.15 C Africa 6122 49.00 'Hl Huizen, Holland 17775 16.88 B LSN Burlingham. Argentine. 9800 30.33 C NAA Washington, D. C 6120 49.02 )JE Berlin, Germany 177611 16.89 B WON Lawrenceville, N. J 11370 30.40 C OQU Basmka.u, Bel. Congo_ . 6120 49.02 AC Pisa, Italy 177610 16.89 l' EAQ Aranjuez, Slain !1890 30.43 B PKIWK Bandoeng, Java 6120 49.02 4SP Bangkok, Siam 117411 16.01 l' JYS Tokio, .padan 9840 30.49 X RKOM Dnepropetrovsk, U.S.S.R. . 6120 49.02 e3XL Bowl Brook. N. J 173111 X 17.:33 LSE Monte Gnaule. Argentite.. !6860 30.61 C W2XE Wayne, N. J 6120 49.02 4AS5 Szekeafebervar, Hungary.. 17130 17.51 B GCW Rugby. England !790 30.64 C F3LCD Saigon, Fr. Indo -China 6116 49.02 VOO Ocean Gate, N..1 171211 17.52 (' WOF Lawrenceville, N..1 8750 30.77 C HJIABO Cartagena. Colombia 6116 49.02 VOY Lawrenceville, N. J 1712(1 ...... 17.52 C GCA Rugby, England !1710 30.89 YV2RC Caracas, Venezuela 6112 49.08 'BC Rugby, England 170811 1' 17.511 CTI AA Lisbon. Portugd.. .. 9610 .31.25 EAQ Aranjuez, Satin 6110 49.10 VLK Lawrenceville, N. J 1627(1 1' 18.44 XETE Mexico City, Me (100 31.25 VE9HX Halifax, N. S., Canada 6110 49.10 VOG Oeem Gate, N. J 16270 18.41 r HBL Geneva. Switzerland 9595 31.27 VUC Calcutta, India 6110 49.10 ZR3 Saigon, Indo-China 16233 18.48 1' K2ME Sydney. Australia 9590 31.28 YV1 BC Caracas, Venezuela 6110 49.10 TK St. Assise, France 15880 18.90 l' PCJ Hilversum, Holland 9590 31.28 HJIABD Cartagena, Colombia .SL 6100 49.18 Hnrlingb'am, Argentine 15811) 18.98 C TIRA Cartago, Ceuta Rica 9590 31.28 W3XAL Bound Brook, N. J YT Kernikwa-('ho, Chibaken, 6100 49.18 W3XAU Newtown square. Pa 9590 31.28 W9XF Downers Grove. Ill 6100 49.18 Jamul 15760 19.04 X GSC Daventry, England 9585 31.30 VE9OW 13owmanville, Canada 6095 49.22 IC1FO mho, Ecuador _.. 1541(1 Rio', 19.47 B VK3LR Melbourne. Australia 9580 31.32 OXY Skandelek, Denmark 6090 IAS3 Szekesfehervar, Hungary.. 49.26 15370 19.:52 B XGBD Shanghai, China 9579 31.32 VE9BJ Saint Johns, N. B 600 49.26 :TI AA Lisbon, Portugal 15350 19.55 B VUC Calcutta. India 9.575 31.33 VE9GW Bowmanville,Canada 6090 49.26 62XAD Schenectady, N. V 15330 19.56 13 KZRM Manilt P 1 9570 31.35 CP5 La Paz, Boliva 6080 49.34 PT la Paz, Boliva 15300 19.60 It SRI 1'.cun, Poland 9570 31.36 TIRA Cartago, Coeur Rica 6080 49.34 YA Paris, Frmce 15295 19.61 B WIXAZ Millis. Mass 1/570 31.35 W9XAA Chicago, Ill 6080 49.34 42XE Wayne, N. J 15270 19.65 B W8XK Saxonburg. Pa 9570 31.35 OER2 Vienna, Austria 6072 49.41 AQ Aranjuez, Spain 15265 19.65 11 VUB Bomixty. India 9565 31.36 EAQ Madrid, Spain 6070 49.42 V1 XAL Boston, Mass 15250 19.67 11 DA Berlin, Germany 9560 31.38 OXY $kamlehak, Denmark YA France 6070 49.42 Paris, 1524:3 19.68 B NAA Washington. D. C 9550 31.41 VE9CS Vancouver, Canada 'K3LR Lyndhurst, .Australia 6070 49.42 15230 19.70 B LKJ1 .ieloy, Norway 9.550 31.41 YV5RMO Maracaibo, Venezuela 6070 49.42 MK Pittsburgh, Pa 15210 19.72 B EAQ Aranjuez, Spain 9545 31.43 HIX Santo Domingo, Dona. Rep.. 6005 49.46 IJB Kouig w uvtcrhauven, Ger... 152 0) 19.74 B LCL jeloy, Norway 9540 31.45 SASH Motala, Sweden 6065 49.46 'NSF England.. Daventry, .... 15140 19.82 B YNA Managua, Nicaragua 9530 31.48 C OSC Boemle, Belgium Congo.... IAA C 6060 49.50 Washington. D. 151311 19.83 B W2XAF Sheneetadv, N. Y 9530 31.48 B OXY Skumlebak, Denmark IVJ 60610 49.50 Vaticn City, Italy 151211 19.84 B OXY Skamleink. Denmark 9520 31.51 B VQ7L0 Nairobi, Kenya, Africa.... IA Kouigswtaerbausen, Ger... 6060 49.50 15110 19.85 B GSB Daventry. England 9510 31.55 B W3XAU Newtown Square, Pa 6060 49.50 INC Ifialeah, Florida 15035 19.92 (' VK3ME Melbourne, Australia...... 9510 31.55 B WBXAL Cincinnati, Ohio 6060 49.50 AY Manila, P. 1 14980 20.03 C PRF5 Rio de Janeiro. Brazil 95011 31.58 B ZL2ZX Wellington, New Zealand.. 6060 49.50 IJB Bogota, Colombia 149o0 2(1.07 C YV3BC Caracas. Venezuela 95011 31.58 B GSA Daventry, England 6050 49.59 /MN Lawrenceville, N. J 14590 20.56 C SRl Peen, Poland 9493 31.60 B EAQ Aranjuez Spain 6045 49.63 L SM2 Hurlingham, Argentine 145011 20.69 C PLV Bandoeng, Jar9 9415 31.87 0 HJSABI Bogota, Colombia 6045 49.63 IMF Lawrenceville, N. J 14470 20.73 C CJA2 Drunanomiville, Canada... 933(1 32.15 C CMCI Havana, Cula 6040 49.67 G BW Rugby, England 14440 20.78 C GCB Rugby. England.. 9280 32.33 C RILO Omsk, L. S. S. R 6040 49.67 0 BA Rugby, England 13990 21.44 C YUR Maracay, \enezuela 9175 32.70 B RLEC Tchita, U. S. S. R 6040 49.67 ' L CO leloy, Norway 13980 21.46 B WNA Lawrenceville. N. J. ... 9170 32.72 C WI XAL Boston, Muse 6040 49.67 G BB Rugby, England 13585 22.08 C CP5 ta Paz, Bolivia 9120 32.89 B W4 XII Maimi Brach, Flu 6040 49.67 G CJ Rugby England 13415 22.36 C GCS Rugby. England 9020 32.26 0 YNA Managua, Nicaragua 6035 Y ID Baghd;ul, Iraq 49.71 13410 22.37 B GCX Rugby. England 8920 33.63 X OQT Buta, Congo 6030 49.75 IMA Iawrenceville, N. J 13330 22.40 C GBC Rugby. England 8860 33.86 B PGD Kootwijk, Holland 6030 WOY Lawrenceville, N. J 49.75 12840 23.36 C PNI Mak:us Celebes, D.E.L.. 8775 34.19 C VE9CA Calgary Canada 6030 49.75 100 Ocean Gate. N. J 12840 23.36 C GCQ Rugby. er.England 8760 34.19 C DJC Berlin. Germyan 6020 49.83 C NR Rabat Fr. Morocco 12830 23.38 B PNI Mak:asser, Celebes, D.L.L. . 8760 34.19 B PGD K otwijk, Holland 64120 49.83 1 IC Pisa. Italy 12800 23.45 C GCI Rugby, England. 8730 34.36 C XEBT Mexico City, Mex 6020 49.83 G BC Rugby, Lligland 12780 23.47 l' GBC Rugby, England 8680 34.56 C ZHI Singapore Malaya 6012 49.90 G BU Rugby, England 1' 12290 24.41 WOO (Ica Gate. N..1 8560 35.05 C COC Havana, Cula 6010 49.92 G BS Rugby. England 12150 24.69 t' WOY Lawrenceville, N. J 8560 35.05 C HRB Tegucigalpa, Honduras 6005 49.96 R NE MONCOW, I. S. S. R 12000 25.00 13 IAC Pisa, Italy 8380 35.80 C VE9DN Montreal, ('canals 6005 49.96 K KQ Bolinas, Calif 11950 25.10 X HCJB Quito, Ecuador 8214 36.50 B VE9OR Montreal, Canada 6005 49.96 F TA Paris, France 11905 25.20 B PRA3 Rio de Janeiro. Brazil 8186 36.65 B EAJ25 Barcelona, Spain 6000 50.00 Y NA Managua, Nicaragua 11890 25.23 B PSK Marapicu, Brazil 8185 36.65 B HIX Santo Domingo Dom. Rep.. 6000 50.00 YA Paris, France 11880 25.25 B CNR Rabat, Morocco 8035 37.33 B RKOM Medevejia, C. S. S. R 6000 50.00 UK Pittsburgh, Pa 11870 25.27 B LSL Ilurliugham, Argentine 7901 37.97 6! RKDN Segja, U. S. S. R 6000 50.00 V JC Calcutta, India 118'0 25.27 B JYR Kemikawa -Cho, Japan 7880 38.07 B RKDO Par telovo, C. S. S. R 6000 50.00 G SE Daventry. England 11865 25.28 B LCN Jeloy, Norway 7835 38.29 B RW59 Moscow, U. S. S. R 6000 50.00 K ZRM Manila, P. I 118.40 25.34 B 0A4AC Lima, Peru 7832 38.30 B TOI Bucharest, Rumania 6000 50.00 W2XE Wayne, N. J 11830 25.36 B HBP Geneva, Switzerland 7799 38.47 B ZL3ZC Christchurch, New Zealand. 6000 50.00 W 9XA Chicago, Ill 11830 25.36 B HBO Pranging, Switzerland_. 7444 40.30 B YV4RC ('arasas, Venezuela 5990 50.25 EAQ Aranjuez Spain 118i0 25.40 B HJSABD Bogota. Colombia.... _ 7400 4(.54 B HJ2ABC Corna CnInmhia Xa7( :va 97 n 400 RADIO -CRAFT for JANUARY. 1935 Wave- Wave- Wave - a Call Louden Freq, length Serv- Call Location Freq, length Sere- Caf location i Iea1th Sam Letters (ko,, (meters. ice Letters (ken, (mews is Limn (IIe,(aMYrf) Ica

HVJ Vatican City, Italy 5968 50.27 B WCN Lawrenceville, N. J 5077 59.08 C HCJB Quito, Ecuador 4110 73.00 B HIX Santo Domingo, Dom. Rep. 5953 50.40 B ZFA Hamilton, Bermuda 5025 59.70 C WND Hialeah, Florida 4098 73.21 C HJ4ABE Medellin, Colombia 5952 50.40 II GBC Rugby, England 4975 60.30 C 12R0 Rome Prato Smeraldo, Italy. 3750 80.00 B HJ4ABE Medellin, Colombia 5930 50.60 B GDW Rugby, England.. 4820 62.24 C CT2AJ Ponta Delgada, Acores 3600 83.50 B HJ2ABA Tunis, Colombia 5880 51.02 B WOO Ocean Gate, N. J 4752 63.10 C CR7AA Mocambique, E. Africa.... 3543 84.70 B WOB Lawrenceville, N. J 5853 51.25 C WO Y Lawrenceville, N. J 4752 63.10 C PK1WK Bandoeng, Java 3490 85.96 B VK3LR Lyndhurst, Australia 5800 51.70 B Y10 Baghdad, Iraq 4470 67.10 B PLV Bandoeng, Java 3197 94.00 C HCK Quito, Ecuador 574 52.50 B GOB Rugby, Englan4 4320 69.44 C PMY Bandoeng, Java 3183 94.30 C FI CIA Tananarive, Madagascar... 5690 52.70 II RW15 Ktubarovek, C. S. S. R. 4273 70.20 B OXB BlaavanI Denmark 1613 185.00 B HJ5ABC Cali, Colombia 5660 53.00 B WOO Ocean Gate, N .1 4272 70.22 C OZP Lyynggby, benmirk 1595 188.00 B PMY \" .1 Bandoeng, Java 5170 58.00 B WOY Lawrencevill 4272 70.22 C SCJ Rarlekron, Swalen _.. .. . 153. 196.00 B OKIMPT Prague, Ccechotlovakà.. 5145 58.30 B RW15 Kbarbarove'.. S. R 4270 70.49 B

POLICE ALARM STATIONS BY CALL LETTERS

Call Location Freq. Call Location Freq. Call Location I Freq. Letters (kc.) Letters (kc -) Letters (kc.)

CGZ Vancouver, B. C 2452 KGZR Salem, Ore .. 2442 WPEI E. Providence, R. I 1712 CJW St. Johns, N. B 2416 KGZS McAlester, Okla 2458 WPEK New Orleans, La.___. 2430 CJZ Verdeen, Que 2452 KGZT Santa (Cruz, Calif 1674 WPEL W. Bridgewater, Mass 1666

KGHG Las Vegas, Nev 2174 KGZU Lincoln. Neb . 2190 WPEM Woonsocket, R. I 2466 KGHK P4alo Alto, Calif 1674 KGZW Lubbock, Tex 2155 WPEP Arlington, Mass 1712 KGHM Reno, Nev 2174 KGZX Albuquerque, X. Alex .. 2.114 WPES Saginaw, Mich 2442 KGHO Des Moines, Iowa 1682 KSW Berkeley, Calif 1658 WPET Lexington, Ky 1706 KGHX Santa Ana, (Calif... 24:30 KVP Dallas, Tex 1712 WPEW Northampton, Mass..__ 1666 KGHY Whittier, (Calif 1712 VYR Montreal, (':ni 1712 WPFA Newton, Mass 1712 KGHZ Little Rock, Ark .... 2406 VYW Winnipeg, Man 21111 WPFC Muskegon. Mich 2442 KGJX Pasadena, Calif _ 1712 WCK Belle Island, Mieli 2111 WPFE Reading. Pa 2442 KGLX Albuquerque, N. Alex ._. 2114 WEY Boston, Mass 155s WPFG Jacksonville, Fla 2442 KGOZ Cedar Rapids, Iowa . 2166 WKDT Detroit, Mich 1.í5x WPFH Baltimore, A1d 2414 KGPA Seattle, Wash . 2314 WKDU Cincinnati. I )hi., 1706 WPFI Columbus, Ga...... 2414 KGPB Minneapolis, Minn 213( WMDZ Indi:uinpoti :. Ia,l 2112 WPFJ Hammond, Ind...... 1712 KGPC St.. Louis, Mo 1716 WMJ ]buffalo. N. Y '122 WPFK Hackensack, N. J...... 2430 KGPD San Francisco, l' :dif 1671 WMO Highland fart, Mich 2 114 WPFL Gary, Ind 2470 KGPE Kansas City. Mo .. 2122 WMP Framingham, Mass 1166 WPFM Birmingham, Ala 2:382 21.12 KGPG Vallejo, Calif WPDA Tulare. Calif . 2114 WPFN Fairhaven, Mass 1712 KGPH Oklahoma City, Okla 2150 WPDB (Chicago, Ill 1712 WPFO Knoxville, Tenn 2474 Omaha, _... KGPI Neb 2166 WPDC Chicago, Ill 1712 WPFP Clarksburg, W. Va_ -._ - ---. 2490 KGPJ Beaumont, Tex 1712 WPDD Chicago. 111 I712 WPFQ Swathmore. I'i 2474 KGPK Sioux City, Iowa 2166 WPDE Louisville, Ky 2112 WPFR .Johnson ('ity, Tenn _...... _ 2470 KGPL Los Angeles, Calif _ 1712 WPDF Flint. Alich 2166 WPFS Asheville, Md 2458 KGPM San .Jose, Calif.... 1674 WPDG Youngstown. Ohio 2158 WPFU Portland, Me.. 2422 KGPN Davenport, Iowa.. 2166 WPDH Richmond, 1n,l 2112 WPFV Pawtucket, R. I 2466 KGPO Tulsa, Okla._..._ 2150 WPDI Columbus, Ohio 2 130 WPFX Palm Beach, Fla. 2.442 KGPP Portland, Ore . 2442 WPDK Milwaukee. Wis 2150 WPFZ Miami. Fla 2442 KGPQ Honolulu, 'I'. It .. . 2450 WPDL Lansing, Mich .. 2112 WPGA Bay City, Mich 2466 KGPS Bakersfield, Calif 2414 WPDM Dayton, Ohio 2.1:30 WPGB Port Huron, Mich 2466 KGPW Salt Lake City, 1-tali _. 2406 WPDN Auburn, N. 1"._ 2382 WPGC S. Schenectady, N. Y 1658 KGPX Denver. Colo_ _ -_! 2 442 WPDO Akron, Ohio 24,58 WPGD Rockford, Ill 2458 KGPY Baton Rouge. 1.a _ _._ . 1574 WPDP Philadelphia, Pa 2174 WPGF Providence, R. I_..___ 1712 KGPZ Wichita, Kans. .... 2450 WPDR Rochester. N. V 2382 WPGC Findlay, Ohio. 1682 KGZA Fresno, Calif 2414 WPDS St.. Paul, Minn 21:311 WPGH Albany, N. Y 2414 KGZB Houston, Tex 1712 WPDT Kokomo, Ind 21!)0 WPGI Portsmouth, Ohio.... -..... 2430 KGZC Topeka, Kans 2422 WPDU Pittsburgh, I'a 1712 WPGJ Utica, N. Y 2414 KGZD San Diego, Calif 2490. WPDV Charlotte, N. C 215S WPGK Cranston, R. I 2466 KGZE San Antonio, 'l'ex_ .. 2482 WPDW Washington, D. C 2 122 WPGL Binghamton, N. Y.. _. -- 2442 KGZF Chanute, Kans 2450 WPDX Detroit, Mich 2 11 4 WPGN South Bend, Ind__ ...... 2490 KGZC Des Moines, Iowa 2166 WPDY Atlanta, Ga 211-1 WPGO Huntington, N. Y 2190 KGZH Klamath Falls, Ore 2382 WPDZ Fort Wayne, Ind 2190 WPGS Mineola, N. Y 2490 KGZI Wichita Falls, Tex 2458 WPEA Syracuse, N. Y 232 WPGU Boston, Mass 1712 KGZJ Phoenix, Ariz 24:30 WPEB Grand Rapids, Mich 2112 WPGW Mobile, Ala Shreveport, 2:382 KGZL La 1712 WPEC Memphis, Tenn _ . 2166 WRBH Cleveland, Ohio 2458 KGZM El Paso, Ter. 2414 WPED Arlington, Mass 1712 WRDQ Toledo, Ohio 2474 KGZN Tacoma. Wash 2414 WPEE New York, N. Y.- 2150 WRDR Gross Pt. Village. Mich_ 2414 KGZO Santa Barbara, Calif 2414 WPEF New York, N. V 2150 WRDS E. Lansing, Mich 1666 KGZP Coffeyville, Nan: 2450 WPEG New York. N 1 2 I.O KGZO Waco, Tex 1712 WPEH GnnerviIlo. \I -- ,-1?

TELEVISION STATIONS BY FREQUENCIES AND CALL LETTERS

Call Location Call Location Call Location Letters Letters Letters 2000 -2100 kc. W6XS Los Angeles, Calif. W3XE Philadelphia, Pa. W2XDR Long Island City, N. Y. W9XAL Kansas City, Mo. W3XAD Camden, N. J. W8XAN Jackson, Mich. W9XG W. Lafayette. Ind. W 110XX Portable & Mobile (Vicinity of W9XK Iowa City, Iowa W2XAB New York, N. Y. Camden) W9XAK Manhattan, Kansas 42000 W2XDR Long Island City, N. Y. W9XAO Chicago, Ill. -56000,60000 -86000 kc. W8XAN Jackson, Mich. W6XAH Bakersfield, Calif. W2XAX New York, N. Y. W9XE Chicago, 111. 2750 -2850 kc. W6XAO Los Angeles, Calif. W9XAT Portable W3XAK Portable W9XD Milwaukee, Wis. W2XD New York, N. Y. W9XAP Chicago, Ill. W2XBT Portable W2XAG Portable W2XBS Bellmore, N. Y. W2XF New York, N. Y. W1XG Boston, Mass.

RADIO -CRAFT fo, JANUARY, 1935 401 THE LATEST RADIO EQUIPMENT

on VARIABLE CON- tube, which incorporates two tri- 400 and 450 kc., are indicated MIDGET odes in one envelope. This type of an upper section of the main scale. DENSER (604) tube (first described at length in Harmonics of the Hartley circuit are the article, "The 2B6-A Duplex available to the 50th, and often the (The Hammarlund Mfg. Co.) Triode," in the September. 1933 150th harmonic. of RADIOCRAFT merits the THIS day of extremes, the tend- issue IN special consideration of foresighted is to build equipment to big- ency engineers. ger and bigger, or smaller and ELECTRIC PHONO- s m a l l e r proportions; the latter GRAPHS (610) trend is exemplified in the TABLE -TYPE ALL -WAVE IF YOU scant to "play" the best newest design of variable con - in phonograph records, i.e.- "elec- denser, which measures only 1 7/32 SUPERHET (607) tric" recordings, it will be neces- ins. deep. This condenser x;,;x1t2 least expensive 110 V. A.C. sary to use an "electric" phono- is particularly well adapted for use graph, which incorporates a "pho- This con. THEmodel of a series of 12 receivers Pee wee variable condenser. in short -wave and ultra short -wave nograph pickup" rather than a will a tube base. recently introduced by one manu- denser fit inside fields ; also. as u tuning condenser 5 in a dual- "tone arm." A recent design in (604) for I.F. transformers, trimming facturer utilizes tubes wave chassis that covers the range portable type is available in either R.F. coils, trimming gang con - of 540 to 1,800, and 5.600 to 18,000 single-play or automatic type, and densers. antenna tuning, for fixed Incorporated are a two -posi- optional 331, or 78 r.p.m. oper- tuning of R.F. circuits or plug -in kc. tone control, limited A.V.C., ation; a piezo -electric pickup is coils, and for padding purposes in tion and dual -ratio tuning. used. Connected to the usual A.F. general. The capacity per air gap amplifier of high -quality type the is about 4 mmf.; commercial maxi - instrument affords the finest avail. mum values. 25, 50, 75 and (il- able musical and other programs at lustrated) 100 mmf. Terminals are A MASTODON IN SET an instant's notice. end; the extensible from either (608) shaft may be extended. These tiny DIALS for fitting condensers are "swell" (Crowe Name Plate & Mfg. Co.) "SHORT- WAVE" FIXED inide n coil form of tube -base size. SHOWN at the recent Radio Show, CONDENSERS (61 I) and one of a large number of HORT-WAVE receivers and recent models brought out by II S of high -quality de- NEWEST IN SERVICE manufacturer that specializes in the sign necessarily are large and ex- and custom production of stock pensive, due mainly to the need for High -grade service oscillator. Use OSCILLATORS (605) models, the latest in full -vision dials this unit in field or lab. work. (6051 components that will meet the (Earl Webber Co.) is nothing if not arresting in ap- "epees." Now, "oil- impregnated" pearance; its overall diameter is 7 fixed condensers are available at of the HOW good is it? Let the follow- ins.I The center portion lower cost and less bulk than the 4 ins. ing facts speak for themselves. dial is covered with a glass mica condensers formerly required Frequency calibration: checked at in diameter that can be graduated for such services in short -wave names are 6 points on each band against crys- to suit; the station equipment as bypass, antenna coupl- tal- controlled frequency standards; printed on a removable ring. Stand - ing. blocking, filter, rotor-ground- m,sldation: 355: at 400 cycles, sup- ard tuning ratio, 5a' to 1. inc, and buffer units, at capacity plied by separate tube and switch values from .002 to 0.1 mf., at po- controlled, and available at A.F. tentials of 1:500 to 1000 V., and to tip -lacks: range: 90 kc. to 25 mega- HARMONIC -TYPE OSCIL- pass up to 50 A. per mf. at 28 cycles at fundamental frequencies in megacycles. The pourer factor is 8 bands; attenuation: complete con- LATOR (609) extremely low. An 0.1 -mf. unit trol over entire frequency range. ?¡s (Try -Mo Radio Co., Inc.) measures only 21i x -in. din. (Re- Equipment: two type 30 tubes. tain mica units only for padding or dummy antenna, demodulation jump- WHERE cost is an im sirt:uit trimming resonant circuits.) er: uses one 41_. V. and one 221_ factor it is usual to select the V. battery. The dial of this port- "harmonic" type of service oscill- able service oscillator is of direct - ator. One of four recent models, in MULTIPLE OUTLETS FOR reading, full -vision type. this design, brought out by this manufacturer utilizes. in the portable ALL -WAVE SETS (612) (illustrated) and cabinet types, A.C. YIIU have read about sill -wave an- with a single type 56 tube. The two tennas of increasingly improved IMPROVED 2B6 TUBE (606) companion types are battery models types, but did you know that the Above, an improved 216 tube. Two 'si l'it0\"EI) -lilt- characteristics and using a type 30 tube. all -wave idea has been applied to range radio outlet antenna triodes in one envelope. (606) a fast-heater cathode are features The fundamental frequency the "multiple recently announced for the latest is 50 to 150 kt-.; common I.F. set - system" describers in past issues of version of the 2B6 "direct-coupled" tings within this range. and at 260, RApto- CRAFT? After "stringing" the all -wave antenna, the dowvnlead Below, a low -cost all -wave set. The more new cable is bared at each florin and a manufacturers have II service oscillator. (609) models. (607) Full- vision, recording -type dial. (60B) Harmonic -type lead tapped off to an "all -wave outlet," to which the antenna post of the radio set connects. The down - lead cable ends at a "terminal out - !et" which is grounded.

A "POKER GAME" RECEIVER (613) FIRST, a boon companion, had recommended to us the "cock- tail" set. described in the preceding October issue, which included with the receiver chassis a full 6- person complement of drinking glasses and assorted liquors. (The "beer bottle" set described in the following De- cember issue was more decorative than practical -unfortunately') Now we our urged to purchase the very (number) in description under picture. Name of manufacturer of any device will be sent on receipt of a self- addressed, stamped envelope. Kindly give 1935 402 RADIO -CRAFT for JANUARY, High quality electric phonograph. Dealing cards, music and a sip! (613) Oil- impregnated (610) S. -W. condensers. All -wave type multiple outlets. (612) (611) companionable receiver, illustrated, acre of parking space, in capacities value is 4,000 ohms, but "specials" that includes not only the drinking from I to 4 mf. at 1000 V., and are available. Cone diameter i- paraphernalia. but also (under the I or 2 mf. at 2,000 V., in round 10 ins.; the over -all width. across lido chips and cards for "a quiet lit- cans (A, in the figure(; and 1 to the baffle. is 14 ins.; a solid spider tle game." 4 mf. in 1,000. 1,500, 2,000, 2,500 acts as a dust cap. and 3,000 V. rating, and 0.5 to 2 DUAL RANGE A.C. -D.C. mf. at 4,000 V., and 0.5 or 1. mf. OSCILLATOR (614) at 5,000 V. rating, in rectangular DUAL -WAVE MIRROR SET cans (R, in the illustration). Pure (Delta Radio Co.) linen insulating paper, impregnated (620) T HE dial of a service oscillator re- with oil, is used; the assembly is It,ST when it appeared that radio cently developed for the low - immersed in an oil bath. As th, set makers had about eached priced trade is accurately calibrated section becomes heated in oper- rho end of their ropes in designing for two ranges; one covers funda- ation it expands and the oil flows new cabinets, out comes an instru- mental frequencies from 132 to 380 into the section, thereby maintain- ment that takes first prize for kc., and the other, the fourth -har- ing a perfect oil film throughout originality in a regular commercial monic range (broadcast band) of the condenser section. As the sec- production job. The set in question 540 to 1,500 kc. On A.C., A.F. tion cools and contracts the oil is utilizes a simple and effective 4 -tuba modulation is obtained from the forced out of the section hack into s'.R.F. chassis, with a wavelength line ripple: on D.C., at 1,000 cycles the can. range of 75 to 550 meters, encased A duel -range service oscillator. (614) from a neon tube. The oscillator in a cabinet composed entirely of is R type 37 tube. mirrors! A modernistic design is MULTI -POLE WAVE -BAND sand -blasted on the portion of the WALL -TYPE "ORDER" SWITCH (6I8) glass that comprises the speaker grille: the colored grille cloth is MICROPHONE (615) ARTICLE after article has ap- interchangeable with cloth of other peared in the technical "maga.," Sh who been colors. l(V ICE Men have pointing out the need for good con- making "aide" money selling tact in wave -band switches. A and installing P.A. systems in switch designed to meet this major A 3 -TUBE SHORT -WAVE restaurants, lunch counters, etc.. demand uses silver -plated contacts, will be glad to know of a new and self -cleaning rotors. The stator KIT SET (621) "wall" -type microphone. A pilot contacts are laced, and then staked (Harrison Radio Co.( lamp lights directly over the press - in place. Available 6 in pole, 16 SHORT-WAVE reception to r the to -talk button. when the button is point, (95 wiring combinations) and be range of 15 to 200 meters may operated; the lamp also may 8 pale, 24 point (500 wiring com- be obtained, by means of plug -in wired to a button at the opposite binations) models, in double-throw coils, in a new short -was e set end, for "O.K." signals. types, diameters, 2, and 2?_ ins., that embodies 5 -tube performance a e.,pectively. TUBE -TYPE CODE PRAC- with only 3 tubes; an additional set of coils is available which in- TICE SET (616) A "SHORT- WAVE" LOUD- creases the tuning range to 025 IT IS an amazing fact that a large meters (Reception of regular number of people of prominence SPEAKER (619) broadcast stations and long -suave (in radio) point with pride to an (WrightDeCoster, Inc.) ship and press transmissions is apprenticeship served in "pounding possible.). Operates on 110 V.. / is the difference be- brass." l'or those who aspire to /WHAT A.C., a 220 V. adapter is available. tween a 'short -wave speak- learn the radio code there is no bet- w This receiver has the volume. er, and any other kind ?" is the first transmitter than the selectivity and sensitivity of a ter practice question the radio man will risk. Wall -type "order" microphone. (6I5) unit just on the market which 5 -tube set, although only 3, "mul- put The major portion of the answer is utilizes a type 30, 2 V. vacuum tube ti- purpose' tubes are used. These as follows: In the new "short- sin an oseilistory circuit comprising tubes are: (a) the new 6F7, used wave" reproducer particular em- as a combined variable -mu R.F. an A.F. transformer l to produce a is on reproduction whistling note exactly like the C.W. phasis placed of pentode, and regenerative detec- the voice frequencies from 200 to tor: (b) a 76 high -gain triode a continuous wave) signal of a 3,000 cycles. regular station. (The Frequencies above first -stage A.F. amplifier, and: (c) transmitting 3,000 cycles are attenuated "A" and "R" supply fit into the so that a 12A7 combined pentode second - noises generated either by the case of the instrument.) stage A.F. (power) amplifier, and radio set itself, or picked up from half -wave rectifier. the air are reduced.. Care has been Provision has been made for OIL-FILLED HIGH -VOLT- Liken to prevent resonance effects optional operation with the built -in AGE CONDENSERS (617) at frequencies below 500 cycles, in speaker, an external reproducer, or order to retain the intelligibility of headphones. Hum level is very low, ( Aerovox Corp.) low- pitched voices. Field excita- even when sensitive headphones BI ILDING a high -power ampli- tion is obtained from 110 V. A.C. are used. Available complete or in fier or transmitter? Well, we by means of a 25Z5 rectifier tube; kit form. Cabinet is 7x5 !_x9 ins. ran tell you where you can get voice coil impedance is IO ohms at long. fixed condensers that can "stand the 400 cycles; the standard output (Continued On page 4211 v aR" without the need for a half- transformer primary impedance Above, tube code practice set. (616)

Oil -filled S. -W. condensers. (617) Improved wave- changing switch. (618) A "short-wave" loudspeaker. (619) Below, a fine set for the boudoir. (620)

RADIO CRAFT for JANUARY, I 9 3 5. 403 i PLUG-IN 58 TUBE 58 TUBE PLUG-1N AN IMPROVED CO J L COIL 6 -TUBE ALL -WAVE SET This receiver will come as a welcome sur- prise to constructors who thought that a "super" was necessary to get good results. It employs a T.R.F. circuit with plug -in coils to cover the complete short -wave and Fig. A is 110 Airplane dial and special shielding gives com- broadcast ranges. It designed for mercial appearance. volt A.C. operation, and includes many de- M. K. BAKER* sign innovations.

THE construction of an all -wave Good Distance Getter! receiver, when it involves more When discussing the relative merits than 5 tubes, should (the writer of a receiver, theoretical design and po- feels) be made as simple as possi- tential possibilities are never as con- ble for other constructors. The use of a vincing as actual practical results that superheterodyne circuit with its conse- are obtained when a receiver is put on quent elaborate padding and trimming an "air- test." Nor is it possible to make condensers, and elaborate aligning pro- any comparison with receivers of other cedure (which, it should be mentioned, design, unless the conditions (which if not performed carefully and precisely affect reception) are exactly similar for will impair the efficiency of the set) each. Consequently, when this set was frightens most set constructors. Not ultimately completed, it was placed on only that, but it is an established fact test alongside of a prominent 6 -tube that few of the average constructors "super" which also employs plug -in are even partially equipped with the coils for band changing. The same spe- Fig. B necessary -wave oscillator and out- -wave view illustrating coil compartments. all cial antenna (all type, with trans- Top put meter to correctly align such a set. posed lead -in) was used for both, a For these reasons a tuned R.F. cir- single -pole, double -throw switch serv- cuit was selected as the basis for this ing to connect the antenna to the set receiver. However, the usual short- which was to be tested. Antenna, comings of such design were given more weather conditions, location, and even than careful attention, with the net re- the operator were therefore the same sult that this set, if built carefully and for each receiver. as per instructions, will be found On practically every wave -band this equivalent in efficiency and selectivity receiver out -performed the "super." On to most "supers" of complicated design. foreign broadcasts the actual volume of All of the usual ills associated with reception was greater on this set, and T.R.F. receivers have been completely numerous stations were received which removed, and what is more, instead of were impossible to get on the "super." sacrificing any of the desirable quali- The selectivity on the ham 'phone band Fig. C ties in such a receiver an actual and (80 meters) was as good in each case. Sub -base view showing layout of parts. appreciable improvement was effected. Amateur code on this set was so far ll ,ffll"'C'hl!II!II Clsicf Eng. Alan Isasilu Corp. (Continued on page 427)

Fig. I. Wiring diagram. Regeneration is employed in first R.F. and detector stages. Second R.F. stage is untuned.

L9 PRONE JACK 60.000 TO 2 GANG 145MMF EACH -- 150 SECTION MMF ÑMF L5 5ONMS PRI. OF - E I 62518 OUTPUT TRANS 50 RF2 OET /.Ol- A.F.2 I MMF MAO MF. TOO V, 5e 58 56 A.FI YT J SW i 1 / 2A5 Ol.' l 80 F 58 F RECT a B o 0.5 fi' MF Va MEG 5 MEGS X -- X X X V5 x MOMF T 01-MF IOMF; 9 25V -v fi 3oyF--T 7.1 L MEG 50.000 OEiíGiL 2 500 O1MS - 14 ó°ús CH -)J N4 2 OHMS L200 L) 2.500 ONM L7 CN MÉG O1M5 FIEL000IL LB see 12 vms - goy v1 425 MF 425 i -T 0,0.45 012.Ó 12 i Comas/ 50.000 OHMS MEG - r\rT`BMF VOL BREGEN coNTROL Net (CAC.)

404 RADIO -CRAFT for JANUARY, 1935 BUILD THIS NOVEL 1 -TUBE ALL -ELECTRIC ALL -WAVE SET The receiver, using only a I2A7, is built within a "cash box." This automatically serves to completely shield the set. The circuit is a standard regenerative detector, using the pentode portion of the tube. It will operate from 110 V., A.C. or D.C. H. G. CISIN

THIS receiver is so small and light tenna trimmer (1), provides a con- cord (15). This resistor is connected in that it can be carried around like venient means of adjusting the set for series with the filament terminals A a camera. Nevertheless, it will varying lengths of aerials and this com- and B of the tube. work from any 110 V. house light- ponent also furnishes an additional Adequate filtering is accomplished by ing circuit, either A.C. or D.C., and will tuning control for short-wave reception. means of a dual electrolytic condenser bring in short-wave stations from 10 The second radio circuit utilized in having 8 mf. sections, one being con- to 200 meters and also the regular this set, is a unique A.C.-D.C. circuit, nected at each end of the 10,000 ohm broadcast station from 200 to 550 whereby chokes are eliminated and re- filter resistor (11) in the plate supply meters. sistors substituted. The receiver can circuit. To save space, the "on -off" The circuit is built into a compact then be operated equally well from al- switch (16) is combined with the po- metal carrying case ( "cash box ") and ternating or direct current sources. No tentiometer (6). the entire outfit including the five plug- power- supply transformer is necessary in coils and the earphone, weighs less in this circuit, which results in a cheap- Construction than three pounds. Only one tube is er, lighter, and simpler receiver. Since The construction is very simple due used, this being the remarkable dual the 12A7 is a cathode heater tube, it is to the fact that the parts are few in purpose 12A7 tube. The wide tuning possible to heat the filament with raw number. The antenna trimmer is range from 10 to 550 meters is at- A.C., without introducing noticeable mounted on the left side wall of the tained through the use of five special hum. The filament voltage is reduced carrying case (see Fig. B). It has a plug -in coils, wound on compact com- to the correct value by means of a 350 short shaft soldered to the adjusting position forms. A single variable tun- ohm resistor, contained within the line screw and a knob fastened to the shaft. ing condenser (3), shunted across the The tuning condenser and the potentio- longer winding of the plug -in coil, takes meter switch are mounted on the front care of the broadcast as well as the wall. The twin phone jack is mounted short -wave tuning. As a matter of on the rear wall. The tube socket is fact, it is possible to cover a much NSAtING IT CRNEG O Vrn E mounted in a horizontal position on the RuOM higher range with this same tuning ONDC '14ANrD CV ( T inside wall, by means of two 5 -in brass condenser, through the use of specially P1.UGIN toi 12 A? TJ;;C bushings. The other parts are mounted wound long -wave coils. ¡SOCKET on the bottom of the case. The antenna trimmer and the jacks must be well in- Circuit Operation and Adjustments sulated from the metal case. The po- Regeneration is controlled by means tentiometer must be of the type which of the potentiometer (6), shunted will not short circuit against the case. across the ticker winding C, D, of coil The coil socket may also be mounted on (2). For broadcast reception, a short short brass bushings. indoor aerial or a wire thrown on the The wiring can be completed in a floor will suffice. Naturally, a well - very short time. The socket connec- constructed outdoor antenna will pro- tions are shown in the schematic dia- duce best results in bringing in the gram (Fig. 1). In socket (8), A and distant short -wave stations. The an- Fig. B. How the set looks when opened. (Continued ou page 433)

Fig. I. The diagram. Resistor filter employed instead of chokes. Fig. 2. A- layout; parts list identifies numbers. B- dimensions.

7 FLEXIBLE WIRE PHONES TO ANTENNA iL/ 12 A7 11

1 MEE

. 12 y1 1 _ q i 14 - A5BE510Sii 1, F LINE CORD e¡ 15 15

cr70 110V., A.C.OR D.C.

RADIO-CRAFT for JANUARY, 1935 405 HOW TO BUILD A NEW 5 -METER TRANSCEIVER Complete construction details are given here for an improved and highly efficient transmitting and receiving unit. Its features are: 6 volt battery operation, radiophone transmission, small dimensions, ultra -port- ability, and employs only 2 tubes.

PHONES A. G. HELLER*

THE popularity of transceivers is tics which make it admirably suited for functions as an oscillator and the 41 increasing steadily with short- specialized work. The tremendous as a modulator tube coupling back to wave "hams." The reason for saving in parts and auxiliary equip- the plate of the oscillator tube (plate this becomes obvious when one ment that an instrument of this type modulation). considers the numerous features of a requires, as compared to that needed The microphone transformer has, in unit that can be readily used for trans- by two separate instruments for trans- addition to the single -button micro- mission as well as for reception pur- mitting and receiving, is in itself a phone winding, another primary for poses. Ignoring the novelty of such a paramount feature. By the elimina- audio coupling to the 41 which is intro- device, we find that a transceiver has tion of this added equipment the sav- duced into the circuit when the switch individual features and characteris- ing in weight is, of course, a conse- is in "Receive" position. quence which follows and which adds The selection of a super- regenera- l'hi,f F: IrInrrr. Insulin' Cmp. ..r to the unit's virtues. In addition, the tive detector circuit is practically a construction of the entire unit is pos- necessity on 5 meters. The tuning sible in a casing of comparatively small characteristics of such a circuit are dimensions, thus enhancing its value essentially "broad," and since the fre- for portable operation. The 5 meter quency "drift" or "shifting" of an transceiver pictured at the top was oscillator on 5 meters is considerable, carefully designed after considerable it becomes readily apparent that such a experience in constructing numerous broad tuning circuit will aid materially similar units. Needless to say that all in keeping the signal "tuned -in." of the problems and difficulties of each Assembly of its predecessors have been finally The chassis and cover may be ob- overcome in the construction of this, tained drilled. Assembly will then con- the final transceiver. sist of merely attaching the component The Circuit parts, and fastening them to the Analysis of the circuit shown in Fig. chassis with nuts and bolts. The pic- 1 will indicate that only 2 tubes are ture diagram (Fig. 2) is a rear view of employed; namely a 37 and a 41. With the transceiver chassis. It clearly illus- the switch in the "Receive" position, trates the positions of the various the 37 functions as a super- regenera- parts and the manner of mounting tive detector and the 41 becomes an them. A close study of the picture A.F. amplifier stage. With the switch diagram should be more than sufficient Fi9. A, above. Interior view illustrating compactness. in the "Transmit" position, the 37 (Continued as page 435)

The layout of parts is not critical. Fig. I. Schematic wiring diagram of 5 meter transceiver. Fig. 2. Pictorial diagram.

S METER 37 OSC 41 AMP BMOD. ¡1EL Ow 3MINDING CO L IMF BLUE ANT ( NON S v \_

) c.IT l ) 15 BLACK THAW RED 10.0000NM5 014,1E6 ftl0w GREEN OUT OUT RF o TRANSF CHOKE NI it TRANSF 01. MEG

BIVE 0 alece X X .006 O . MF M I C REG wr-- XMIT - ,a+ 5V g-

406 RADIO-CRAFT for JANUARY, 1935 ELEMENTS OF 4*" DIMENSION

MICROPHONES P.A. OR SOUND , SYSTEMS

This is the first of two articles which dis- closes, in a non -technical manner, all of the principles involved for attaining absolute (

rOUR SETS OF realism in sound reproduction. Part 2 will BLOCK DIAGRAM NIOU.MIODLE OF A FUNDAMENTAL AND LOW FOURTH DIMENSIONAL FREQUENCY cover practical construction and installation. SOUND SYSTEM FOUR CHANNEL DYNAMIC AMPLIFIER SPEAKERS S. R. Fig. A H. MANNEY* AND C. SHAWt Block diagram of a fundamental 4th dimensional sound system.

PART I F ARTIFICIALLY recreated sound and centralized. In fact, a critic is eyes you cannot tell whether you are is not "perfect" in all respects to quoted as saying, "To listen to a sym- listening to an electro- mechanical de- natural creation, it cannot produce phonic orchestra reproduced by electro- vice or to the original rendition-if you I an illusion of true reality. mechanical systems, is like listening to can mentally locate the true position Inasmuch as the purpose of all enter- the performance through a knothole in of each sound source, then, and only tainment is to help the auditor to forget a fence." then, are you hearing perfect artifi- himself, the more perfectly we create Although innumerable attempts have cially recreated sound! the feeling that he is listening to real previously been made to attain a true Why then, has this perfect illusion people, the more will he "lose" himself and natural state of sound recreation, not been achieved before, and what and the greater will be his feeling of few have approached the goal as close- elementary principles are involved in real enjoyment. ly as did the Bell Telephone Labora- presenting such an ultimate in electro- Very many people regard mechanical tories during the early part of last mechanical sound recreation? sound reproducing equipment frankly year. This organization demonstrated Before we answer these questions, as a mechanical device and therefore to the Institute of Radio Engineers a let us consider two points of the defi- do not expect it to simulate reality. three dimensional sound system, which nition for "perfect artificially recreated The consequence of such a point of was subsequently described by R. D. sound" as given above. view is that they accept this unnatural Washburne in RADIO CRAFT for May First, we have "true reproduction" sound on the basis that it represents 1934 (Page 654). which involves the use of a sound coI- perfection for modern artificial creative To understand why this apparently lective, amplifying, and distributive means and methods. "perfect" system does not attain a full system which will not modify or alter Musically trained a n d artistically 100% naturalness, we must first define in any manner whatsoever the fre- tempered people, on the other hand, "perfect artificially recreated sound ". quency, phase relationships, or pro- have oftimes complained that repro- For our purposes of discussion we will portional intensity of the sound or duced sounds (as furnished by "talk- simply consider it as a true reproduc- sounds undergoing recreation. Such a ies", radio broadcasts, P.A. Systems, tion of the original sources of sound in system will of necessity employ micro- electric recordings, etc.) are too flat a spatial relationship corresponding phones with a series of performance exactly to the placement of the original characteristics equivalent to the .sullmr of 'ruurth DIulendouRl Noand... human Tnr.IFn F:nFiurri, Columbia .ouwl N)lM1'IP Co. son ad sou rces. If upon closing your (Continued on page 430)

Fig. I. When we hear a natural sound, we sub- Fig. 2. Block diagram of sound localising mechen Fig. 3. Practical experiments in single dimensional consciously make three measurements. ism. X indicates source of sound. sound systems. See text.

6- 12 VOLT 500 /1 -A- f SOVRCE OF SOUND OHM /\A-\ \ i STEP -DOWN POTENTIOMETER. 200 OHM TRANSFORMER. TELEPHONE / HORIZONTAL ANGULAR 1 1 RECEIVER AXIS \\ DISPLACEMENT INDICATES OF SOUND I \` i ;AXIS OF SOUND / / WAVE REACHING \ /- WAVE REACHING \\ NOW MUCH TO ONE SIOE L / ( LEFT EAR LX) RIGHT EAR (RX) \ \ / THE SOUND 15 COMING FROM .,' TOP VIEW INTERPRETIVE CENTERLHEARING', OF HEARING n\ FOR LEFT EAR ) /- - CENTER. N CENTER OF HEARING 411 VERTICAL ANGULAR DIS- / \ FOR RIGHT EAR PLACEMENT TELL US LEFT NERVE TO 11OVOLT CONDUCTOR 1 WNETNER THE SOUND IS RIGHT NERVE A.C. 60 CYCLE 1-i / COMING FROM ABOVE OR BELOW CONDUCTOR POWER LINE RECOMMENDED 60 SIDE VIEW CYCLE SOUND SOURCE X / LEFT / EAR RIGHT EAR SEPARATE ROOM -C- HEAD 2.000 011M ^y HEAD PHONES C DISTANCE OF A SOURCE -.- -- - OF SOUND 15 ESTIMATED WHEN SWNO ACCORDING TO THE IN- SORC F TO //F ONE S IDO TENSITY OF THE SOUND LISTENER. SIDE WHICH REACH / SOUND VIEW WAVES OUR EARS. LX\- I SOURCE Rx -D- 200 OMM MICROPHONE \ A SOURCE OF SOUNC 15 LOCAL- 0.5MEG IZED IN SPACE BY COLLATING MICROPHONE POTENTIOMETER THREE MEASURES IA)IIORNONTAL 41/2 VOLT I ANGIAAR OISPLACENENT,IB) VER BATTERY I TRANSFORMER TICK ANGULAR DISPLACEMENT, AND IC) DISTANCE LODUZIW A SOMO SOURCE,KIeII -B- PsiB,. X INDICATES ORIGIN OF IT IS 'TYPICAL DIRECTLY IN PRONI SINGLE DIMENSIONAL SOUND - SOUND OF LISTENER SYSTEM

RADIO -CRAFT for JANUARY, 1935 407 INTERNATIONAL RADIO REVIEW

HERE is what the radio experi- TELEVISION IN EUROPE menter has been wanting for a long time semi -technical re- HILE television is gradually near- -a ing of commercial pro- view of the thousands of new the point duction in the U.S.A., depending on ideas which are continually ap- public interest to awaken suddenly; pearing in overseas publica- the condition in Europe is somewhat tions. Each month there are re- more advanced. ceived at the offices of RADIO - Experimental transmitters are in CRAFT hundreds of daily, weekly constant use in England, Germany, and and monthly magazines orig- several other countries, with varying inating from all over the world. degrees of success. Commercial receivers are available for picking up SINCE the cost of subscribing to these transmissions and there is con- each of these would be prohib- siderable interest shown in the radio itive for most radio men, we have magazines of these countries on the arranged with technical trans- subject. Fig. I lators to prepare for our readers The photo at Fig. A, shows a com- A short -wave converter covering the wavelengths mercial instrument being sold in Eng- 12 70 reviews of all the really impor- from to meters. land. It contains a four tube receiver tant, new developments illus- having an audio frequency character- trated and described each month istic of 20 to 9,000 cycles according in these publications. to claims of the manufacturer. A glow NOTE that the only available in- discharge lamp of special design permits black and white images. formation is that which is pub- It is reported that the B.B.C. is con- lished; the experimenter must templating a change to 30 lines which adapt the ideas to whatever will increase the picture definition, equipment he has on hand. though it will necessitate changes in existing receivers.

AN ITALIAN SHORT -WAVE CONVERTER A NEW FREQUENCY-CHANGER IN reviewing the foreign magazines converter tubes have received this month, an endeavor PENTAGRIDmade a very definite step forward in has been made to cover some of the the design of superheterodyne receiv- outstanding items on short -wave sub- ers, since the electron- coupling over- jects- inasmuch as we are featuring comes certain defects which were pres- short -waves in this number. ent in all other types of frequency Fig. A The Italian magazine, Radio Lux, changers. However, it appears that converter is also imper- The appearance of the new television set which contains a description of an interesting the pentagrid supplies black and white pictures. short -wave converter to be attached to fect in certain other respects, espe- the broadcast set. It comprises a pen- cially on short waves. An interaction Wllll :IIIM... tode of the R.F. variety. The partic- between the oscillator plate and the ular tube advocated is one of European control -grid causes degenerative effects Fig. B manufacture, though American tubes which become particularly noticeable The triode- hexode freouency converter. when high frequency signals are being Triode- hexode coupling at short wavelengths is ni . are extensively used in Italy, as we have mentioned before. received. The effect is so marked in some cases, that the oscillator section A grid coil, tapped in three places of the tube refuses to operate above a (see Fig. 1) tunes the grid circuit, certain critical frequency. while two coils wound on the same To overcome this disadvantage, a tube act as the oscillator grid and plate new tube has been introduced on the coils. The wavelengths between 12 European market, according to a re- and 70 meters are covered by the coil cent issue of WIRELESS WORLD. (Fig. combination, and with this coverage, B). It consists of two separate tubes, a no taps are required on the oscillator triode and a hexode, built in a single coils. The coils are wound on tubes, envelope. The hexode has six elec- a control -grid, two 1% ins. in diameter, with No. 24 trodes, cathode, screen- grids, a coupling -grid, and a enameled wire. The grid coil contains plate. The control -grid immediately 4 turns on the first section, 4 on the surrounds the cathode and is sur- second, 5 on the third, and 6 on the rounded by the screen -grid. The fourth. The oscillator contains 6 turns coupling -grid comes next and is sepa- on the tuned section and 4 on the plate rated from the plate by the second side. The grid coil sections are sepa- screen -grid. The coupling -grid is con- rated by about '/a -in. while the two nected internally to the triode (oscil- coils of the oscillator are wound as one lator) grid which supplies the desired electron coupling. continuous coil, with a tap at the sixth Variations in the oscillator plate po- turn. tential have no effect upon the screen The remaining values for this con- and plate currents of the hexode, and verter are indicated on the diagram. changes in the hexode screen, plate or

408 RADIO -CRAFT for JANUARY, 1935 the earth and this definitely limits the distance which can be covered by such units. But on the other hand, the aerials used for these transmitters and receivers determine to a large extent their effectiveness. Aerials, on these very high frequencies, do not exhibit the same characteristics as similar designs do on longer waves. Marked directional effects are encountered with Fig. C horizontal and vertical dipoles, half - A novel combination radio -phonograph. wave and other types which should not show these effects. Loops on the other hand, are found to be markedly effec- control -grid voltages do not alter the tive for reception purposes -and the oscillator plate current. Thus the two directional "selectivity" tubes are independent, except for the depends to a electron which great extent on the dimensions of the coupling takes place. loop, its shape and height above This tube shows markedly improved ground. characteristics for high frequency Thus, the ambitious a work. ultra- short -wave fan has a fine chance to experiment Fig. D. A really portable receiver. with different types of aerials, and thus achieve real results which can be AN INTERESTING DESIGN of use to the entire "ultra- short -wave IN the Italian radio magazine, LA world." RADIO PER TUTTI, was included an in- In giving some facts regarding the teresting design for a combined radio above subject, a circuit for a 5 meter and phonograph, in one of its recent super -regenerative receiver was given. issues. The cabinet, when closed, ap- (See Fig. 2.) The values of parts used peared as an ordinary radio of the in this set were not given, but the table type, having two wave ranges, interested fan will find the method of with separate dials for each band. The connecting the loop to the set advan- cabinet, however, was split across the tageous. Suitable sizes for the vari- top in such a way that the two halves ous condensers and resistors can be opened out, as shown in Fig. C. When found by a little experimental work. opened, a complete phonograph of the electric type was revealed. The amplifier of the radio receiver provided the necessary increase in volume for ordi- A REAL PORTABLE nary room enjoyment. TO digress for a time from short- waves; the tiny portable receiver shown at Fig. D, using the newly developed small tubes which we mentioned SOME WORTH -WHILE EXPERI- several months ago, has just appeared Fig. E. A complete permeability tuner. MENTS on the English market. The entire receiver box measures 4 x41/2 ins. HILE ultra- short -wave experi- %x61/4 W high and it weighs only 3 lbs., complete ments are exceedingly interesting with batteries. The set tunes over the to the lively radio experimenter, even broadcast band, and with only a tem- this field becomes prosaic if definite porary aerial will pick up direction is broadcasts not given to the experi- over a distance of 75 to 100 miles. This menter which will make his work of "really" portable set was announced value to others. in WIRELESS WORLD magazine. The latest issue of WIRELESS WORLD takes this point in hand and points out some very interesting ways in which experiments in the ultra -short-wave PERMEABILITY TUNER field can be made useful. One of these IN A number of past issues, we have is in the field of aerials for ultra- short- mentioned the popularity of metal wave transmission and reception. It is core coils for R.F. tuning. known Fig. F that the sky waves from such The idea has been developed a step A high -quality pine-electric mike. transmitters are not reflected back to (Continued on page 426)

Fig. G Fig. 2 This rectifier covers the broadcast band. A loop- operated 5 meter super-regenerative receiver for direction finding. '/4' -a¡

RADIO -CRAFT for JANUARY, 1935 409 A SHORT -WAVE BAND -SPREAD 2 -TUBE PORTABLE SET Here is an excellent and truly portable short -wave receiver, for outdoor use. It employs only 2 tubes, dry -cell type, which results in real economical operation. Batteries are self- contained. FRANK J. LESTER*

WITH increasing public interest day. However, little attention is being noise of the city, remarkable results in short -wave reception, man- paid to another angle of the short- can be obtained with relatively simple ufacturers have kept their wave market that is also very much outfits. engineers busy designing bigger and alive -portable receivers. The very definite demand for a sxt better receivers for home use. Sets us- Many people who are cursed with of this kind led the writer to design ing nine, ten, twelve, and even fifteen bad locations for short -wave reception this "bandspread portable." This is tubes are by no means uncommon to- would like to take compact receivers truly a portable receiver in that a per- out in the country with them on Satur- son can carry it more than 10 feet -Eng.. IChole.ale Min Servile Co.. Inr. day or Sunday drives. Away from the without dislocating his shoulder. It can be thrown in the back of a car or Fig. I. left. Diagram. Circuit consists of regenerative der., and one audio stage. carried comfortably in a train or trol- Fig. A. below. Internal view. Coil h mounted ley. Complete, with all required bat- between the 2 tubes. teries, it weights only 9 pounds. If this sounds like a lot of radio set to lug around, weigh up your handbag the next time you have occasion to take a short trip! You'll be surprised to learn how much more than nine pounds it weighs. The receiver is built into a strong metal case measuring only 8% by 634 by 51!s ins. wide, fitted at the top with (Continued on page 433) AN IMPROVED 2 -TUBE SHORT -WAVE BOOSTER This unit was designed for the purpose of improving the efficiency of your present short -wave receiver. It is an improved 2 -stage short -wave amplifier, A.C. operated, employs special completely shielded compartment type coils, and is very simple to connect to any type of receiver.

S. MILLER*

IN THE average short -wave receiver, upon numerous factors, chief among the input voltage of faint or prac- them being antenna pick -up efficiency antenna will always receive the signal tically inaudible stations has a and signal strength. with the same intensity (under similar relatively constant value depending If the power of a weak or inaudible atmospheric conditions). If the aver- is -1111r4 Eng'r.. Postal Iladlo l'rP. foreign station remains the same, your age intensity of the received signal too weak to activate your receiver, it will not be heard regardless of how sensitive your receiver is or how much audio amplification you use. On the other hand, if that same feeble signal could be strengthened Fig. I is The wiring diagram of considerably, before it fed into the a 3 -tube. 2 -stage short- reciver, the result will be equivalent wave signal booster. Special compartment to an apparent increase of power on type coils are employed. the part of the broadcasting station, and the same signal will become distinctly audible (or it may operate the loud -speaker at full volume). This is exactly what this R.F. booster does. (Continued on page 432)

410 RADIO-CRAFT for JANUARY, 1935 THE LISTENING POST FOR ALL -WAVE DX -ERS The author imparts some very valuable information on how to best obtain proof, or verification, of foreign station reception. Also, schedules and hints on DX on all waves.

C. A. MORRISON Zeesen's (Germany) directional antennas.

WITH that feeling of pride foreign country return postage should on the broadcast band. At this time that comes to every Dx'er be enclosed in the form of an Interna- signals from Japan, China, Hawaii. upon hearing his first for- tional Reply Coupon which you can Alaska, Central America, South Amer- eign station, whether it be purchase at your local post office for a ica, Europe, Australia, and New Zea- on the broadcast band, or short waves, few cents. land are heard under good weather con- there arises a natural desire to have For your report to be of value to the ditions. some way of proving to other people station these general items should be Foreign countries which will be re- that he actually received this station. included in your letters; (1) State ceived best during this period on the It is through this desire to show proof weather conditions, (2) temperature, eastern coast of the United States will of foreign reception that the hobby of ( ) direction of wind, (4) volume of be about as follows in order of consist- acquiring verifications or confirmations station's signal, (5) whether fading - ency: (1) Europe and South America. has arisen. A verification of reception and how bad, (6) whether natural (2) Australia, New Zealand, and is nothing more than a written state- static was present, (7) was station in- Hawaii. (3) Japan and Central ment by letter or postal card from a terference experienced, (8) type of re- America. (4) Alaska and China -very station that, upon a certain day and ceiver in use -and number of tubes. rarely. at a certain hour, you actually received These facts, in addition to your report, Foreign countries which will be re- their station. It stands to reason that will certainly insure you an interesting ceived best in the central area (From for a station to issue such a positive and attractive confirmation of recep- the Appalachian to the Rocky Moun- statement they must be reasonably tion. In the case of foreign stations it tains) will be about as follows in con- sure that you actually heard them. The should be kept in mind that several sistency: (1) Australia, New Zealand, more accurate and concise information weeks, or even months, may be neces- and Hawaii. (2) South and Central you can furnish to the station the bet- sary before you receive your reply. America. (3) Japan and Europe. (4) ter are your chances for securing a Many DX'ers have accumulated, over China and Alaska rare. verification. A report of value to the a period of years, collections of hun- Foreign countries in order of best station is never turned down. The ap- dreds of verifications which are great- reception for the Pacific coast area will proved method for the securing of veri- ly prized by them. generally be (1) Japan, China, and fications is as follows: Next month we shall delve deeper Hawaii. (2) Australia, New Zealand, When listening to a foreign station, into this fascinating subject of secur- and Alaska. (3) South America rare. and if you wish to verify, have a re- ing foreign verifications, describing (4) Europe very rare. liable clock and your log book handy. how you may obtain a verification of a Foreign stations from the east are Carefully note down what is heard and program, even though both music and best received for a period of one or the time in your log book. When not- voice are of a foreign nature, and de- two hours after the U.S. stations have ing musical selections, titles should be scribing for you some of the logs of signed off for the night. Foreign sta- given if possible, type of musical in- the greatest DX'ers of all times, and to tions from the west are best received struments, time of music (whether what they attribute their success. one or two hours before dawn. Sta- etc.) When noting march, jazz, classic, What to Listen For During December tions to the south are received good to songs include titles if possible and al- - fair almost daily with average weather ways specify whether male or female January conditions. Their reception being lim- voices, runnber of voices, type of music -Broadcast Band - ited principally by their power, or to the (jazz, blues, operatic, etc.), type of With the exception of Australian - times when they are on the air unusual- voice (bass, tenor, soprano, etc.). When New Zealand stations, December and ly late on a clear channel. Once in a noting a speaking voice include actual January are usually the peak months while, they will break through the U.S. words spoken when possible and type for foreign reception in North America stations in the early evening. of voice (high pitched, or DX'ing reports for the low pitched, etc.). If in a A view of the transmitting equipment at Reykjavik, (cela nd. early part of the season in- foreign tongue state kind of dicate foreign stations being language if possible. Call let- received with unusual excel- ters should be noted, along lence. Europeans coming in with location, and musical very good on the eastern signal if any. If station is coast. Japanese and Chinese signing off be sure and note stations good on the Pacific the exact time. coast, and Australia and In writing to the station be New Zealand stations fair to sure you have the correct ad- good over the whole area. dress by referring to some South Americans are break- good station log. The letter ing through in the early eve- should consist of a resume' nings. of what you heard as given above, and the time each Short -Wave Band item was recorded. Return As fall changes slowly into postage should always be en- winter the seasonal high - closed. When writing to a (Continued on pane 428)

RADIO -CRAFT for JANUARY. 1931 411 AN ECONOMICAL P.A. AMPLIFIER This amplifier is suitable for the majority of P.A. installations. It has a power output of 18 watts, total distortion less than 5 per cent, and uses type 45 tubes in the power stage. Power supply is built separately, facilitating rack and panel installations. A. J. KOENIG*

SERVICE Men and other technicians who are bemoan- Many amplifiers on the market at present are tainted ing the shrinkage of their income on radio receivers, with the stigma of fallacious power output ratings. It is would do well to devote some serious thought to the significant that no mention is made of the total per cent lucrative opportunities offered in public address appli- distortion at full power output. The amplifier described cations. Many have been quick to realize the wisdom of an herein possesses a gain of 75 db. and is capable of. delivering investment in a sound system but have been deterred 18 watts with a total distortion of only 5%, which is largely because of limited funds. It is the purpose of this almost negligible. paper to describe an amplifier which shall meet all the Power Output: While several factors are taken into con- necessary requirements and at the same time be well within sideration in the choice of an amplifier, power output is the price range of those who have procrastinated on ac- perhaps first in importance. The coverage value of a sys- count of financial considerations. (Continued on page 440) Enrineer. Kenyon Tran.former Co.. Im,

Fig. I. Wiring diagram of amplifier; employs only 4 tubes. Fig. 2. A- diagram of mixer circuit; B -power supply. MIKE INPUT 57 NIGH IM G. 57 TRANS TRAMS 45

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0.5 nono \ áÑO..os 35V 400V 0..5 K S V INPUT') 04.MEG AN IMPRESSIVE 7 -TUBE DUAL -RANGE SUPERHET This receiver has distinctive design features which make it an outstanding performer on broadcast and short- waves.

THE RECEIVER illustrated in the mediately impressed by these facts, adjacent photograph is of unusual which are later proved when a closer design, both in regard to appear- scrutiny is made of the set's construc- ance and engineering. One is im- tion. The 5 -inch tuning dial is of such

Illustrations, eourte.y .1. 3lalheson Bell. Ins. intriguing design that it lends distinc- Diagram. Receiver employes 6 volt tubes. tion to the physical appearance' It incorporates, in addition to the dual -wave range scale, two novel indicators which are directly and respectively controlled by the volume and tone controls. Circuit This receiver is a broadcast and short -wave set with a frequency coverage of 530 to 1,740 kc. on the broadcast band, and 5.8 to 18.3 mc. on the short- wave band. Dual -band coverage is accomplished by means of dual sets of (Continued on page 439)

412 RADIOCRAFT for JANUARY, 1935 NEW DESIGN t- 114FT. TO SUPPORT STAND-OFF AT EDGE IN ALL -WAVE T; WATER PIPE OF ROOF

DOUBLE ANTENNAS LIGHTNING ARRESTOR The improvements SPLIT described result in great- KNOBS volume er on the broadcast as well as short- RECEIVER wave bands. Also, they assure reduction of COUPLER. local interference, which permits full effi= ciency from high -fidelity receivers. Since TO RECEIVER. most listeners make use of the tone control CHASSIS. NOT RED to minimize the strength of noise, the advan- TO"GND" POST tage of an efficient noise -reducing antenna, BLACK - TO as an aid to fidelity, becomes obvious. RECEIVER -ANT" POST A. H. LYNCH* C' CLIP OR "ANT.' WIRE Fig. 2. A simple, complete noise- reducing, all -wave antenna sistem.

UI' TO the present time every all - mentioned system by the use of an convenience rather wave than electrical effi- noise -reducing antenna impedance -matching device at the an- ciency. This system is shown in Fig. system has been deficient in sig- tenna which eliminates the losses usu- 2. Its commercial prototypes were nal strength on the broadcast ally sustained in the ordinary type of known as inverted L -type antenna sys- band. In some systems a compromise noise -reducing lead -in. tems. has been made with noise by including Where suitable space is available an The latter system does not require a switching arrangement which con- entirely different type of antenna is the elaborate verted and rather expensive an- the antenna from a doublet with suggested having a total over -all length tenna transformer and where space is noise-reducing properties to an ordi- of 114 feet which is approximately half available it is recommended as being nary "T" antenna with no noise- reduc- a wavelength at 70 meters or 4.3 kilo- superior to the doublet type. As is ing properties. It had been thought cycles. With this type of horizontal true with the duplex system, the flat impossible to provide an antenna sys- antenna the lead -in is taken from the top need not be in a straight line. It tem which would be efficient over the end rather than in the center. This has may zig -zag, but it should not double very broad band of frequencies which been done as a matter of mechanical back on itself. lie between 5 meters and 600 meters, which is equivalent to 55,000 to 550 How the Systems Work kilocycles. Most of the important short -wave The ordinary broadcast receiver has broadcast stations a frequency operate on approxi- ratio of approximately 3 mately 13, 16, 19, 24, to 1. 31, 49, and 70 New and improved antenna sys- meters. A long horizontal tems, now available, antenna cut have a frequency to receive on 70 meters is fairly effi- ratio of more than 40 to 1. cient on all of the other wavelengths Location Determines Better Type and it is extremely good in the broadcast band. Such an antenna should be For the person who is located iii the To f- -2FT. .I 114 FEET SUPPORT TO OTHER NAVY at least 30 feet above the ground. By city or who lives on a modest -sized plot OR MAST STANDARD INSULATOR reason of the size of the collector (an- in the suburbs, the new doublet antenna) the signal strength it picks up tenna system shown in Fig. 1D is rec- is rather large and compensates for ommended because the total length of ANTENNA WIRE small deficiecies between the antenna the horizontal portion of NAVY (HEAVY GRADE) the antenna STANDARD and the receiver which could not be need not be more than 41 feet. Natu- INSUL ATOP tolerated with a collector of the smal- rally an antenna of such small dimen- CABLE -B- ler size. Therefore, the impedance - sions will not have the pick -up of one matching transformer at the antenna is made with a very much longer flat -top. Fig. 3. above. eliminated for both mechanical and But this deficiency is overcome in a A -new antenna coupler; B-end -led antenna. financial reasons. A low- impedance most practical manner in the afore- transmission line is used on both sys- *Arthur H. Lynch. Inc. (Continxed on page 438)

Fig. I. Fundamental and practical all -wave, noise -reducing, antenna systems. See test for complete details.

TO TO ANTENNA 20I-6' 1701-H" A1 L2 L3 L4 A2 ANTENNA pl RED RED Ì~ WIRE ,! pl ) A2 ------I

LIO O CABLE ANY LENGTH , I V ¡r A3 Al 1 _ o A2 A3 I , L5 - - I -18 _ -_ . J CI --4 C2 - f BLACK BLACK O i (WIRE Al, 1 wIRE IIY A3 'g!

TRANSMISSION I LINE p % - L9 BLACK A2 l'' TO RECEIVER. A2e - WIRE TO .. TO CHASSIS ANTENNA POST -A- B A3 c -D-

RADIO -CRAFT for JANUARY, I 9 3 5 413 FIRST PRIZE $10.00 SHORT -CUTS SECOND PRIZE 5.00 THIRD PRIZE 2.50 Honorable Mention IN RADIO EXPERIMENTERS: Three cash prizes will be awarded for the best "short -cuts" - time- and money-saving ideas- submitted by readers of RADIO -CRAFT; Honorable mention ON 11 MA 5 TURNS V will be given for all other published LL FORM. /4' ACE ON FORM TO FIT 5- TURNS BETWEEN INSIDE OF TUBE items concerning radio and its allied 75 WINDINGS PLUG IN fields. FEET COIL I1 (ANT) Send us your "kinks" right away.

L2 SOT. NR.28 LINE NOT ENAM. WIRE LONGER THAN TAPPED EVERY L FOOT IC TURNS STA

OP TOO. PLUG -IN COIL

Device to increase short-wave sensitivity, and signal -to -noise ratio. Circuit of unit pictured at left.

FIRST PRIZE 10 turns; fine tuning is accomplished by means of condenser IF AN antenna is resonated at the frequency to which the C. Coupling between antenna and receiver (represented by receiver is tuned a considerable increase in signal tube V) is accomplished by a "link" circuit, one coil of strength can be obtained; also, the signal -to -noise ratio will which is inductively coupled to the antenna loading coil, be improved. The illustrations above show a simple device and the other to the receiver. The little 5 -turn coil, L3, at that can be constructed for tuning the antenna of a short- the receiver end of the link may be slipped inside the grid wave set from approximately 15 to 75 meters. The antenna end of coil L4. We strongly recommend that short -wave proper is roughly tuned by L2, which is tapped at every fans give this gadget a try. GEORGE N. SHORTT

SECOND PRIZE SOLVED! -the problem of how to successfully groove short-wave coil forms at home. The idea is to cut in the SAW tube base, by means of a coping saw, as many closed- circle CUTS SAW ACROSS of CUTS grooves as may be required for the desired number turns FORM is conveniently rotated for the purpose AROUND of wire; the form FORM, by utilizing a hand -saw. Just drill a hole in the center of the base of the coil form, run a bolt through the hole and WIRE !/J tighten in place by using a lock -washer, nut, and lock -nut, in chuck of a hand -drill. Hold the saw - and grip the bolt the CROSS blade against the coil form and rotate the form until a OVER. groove of suitable depth has been cut. The final step is to mount the coil in a vise and a series of diagonal grooves SAW CUTS ACROSS FORM along the top of the form, at an angle of 45 degrees. These HOW TO GROOVE 5-W. COIL straight, diagonal incisions join each successive ring, as FORMS WITHOUT NEED OF SPIRALING shown in the illustration at the right. S. S. MARC,t.ox At last! short -wav coil fo dh may be easily grooved. This kink saves set builders a dollar or two. THIRD PRIZE HERE is the way you can make a back -of -panel control from an old front -of -panel dial -such as Marco, etc. WASHER. Just discard the bake!ite cover and retain only the dial and SOLDERED SOLDER TO TO FACE PLATE friction drive -shaft. (The particular dial illustrated at BUSHING the left is a rebuilt Pilot.) An escutcheon on the panel BUSHING WITS, will complete the commercial appearance of the job; most 1/4" HOLE mail -order houses carry an assortment of designs and sizes. Many of the front -of -panel dials were equipped with trans- lucent discs on which the graduations were marked, conse- SET SCREW quently, these lend themselves very nicely to illumination by means of a pilot light mounted in back. WASHERS Little mechanical ideas such as this one may be applied by wishes to save a and BOLT FOR the radio man who dollar here there, ATTACHING in conjunction with the valuable information contained in WASHER SOLDERED TO 6, TO FRICTION CHASSIS RADIO -CRAFT LIBRARY BOOK NO. "Bringing Elec- DRIVE-SHAFT tric Sets Up to Date," to "cash in" on the intrinsic value of a great number of older set models that are now available for a song. GEORGE H. MORSE

414 RADIO -CRAFT for JANUARY. 1935 READERS' DEPARTMENT

A department in which the reader may exchange thoughts and ideas with other readers.

S. -W. SERVICING IN HAITI For the telephone channels "inverters" or "speech scram- Editor, RADIO- CRAFT: blers" are employed to assure secrecy of communication. A Lincoln SW33 battery -operated -ct, after 1 month of Broadcast Programs: The Brazilian government trans - service cut off suddenly. When called to service this set I mits daily, with the exception of Sundays, their news bul- thought first it was the primary of the first A.F. trans- letin of the "Programs Nacional" through PRF -5 (31.5 M.). former which had burned out, but this transformer proved From 22:30 G.M.T. news in Portuguese; and from 23:00 good after test. The defect was in the tuning meter. "It's until 23:15 G.M.T., news in English, French, Spanish and a long way to New York," from Port -de -Paix, to get a re- German. placement meter, so I connected a wire across the terminal Special musical broadcast programs are frequently re- leads in the meter and the set worked as perfectly layed in combination with some of the local medium -wave as before. stations. GEO. A. CELESTIN, Station PSK with directive antennas to Buenos Port-de-Poi.., Aires is frequently used to relay Rio programs to the Haiti, Argentine stations, and PRF -5 is employed when the pro- British West hulks. gram is meant for the rest of the world. Transmitter: The equipment employed is a "Standard" 60 kw. short -wave radio -phone transmitter (similar to the THE WHOLE STAFF THANKS YOU! B.B.C. Empire transmitter), and is located in Marapicú Editor, RADIO -CRAFT: in the middle of the Brazilian jungle, at a distance of 80 Have been buying Gernsback publications since they first kilometers from the beautiful city of Rio de Janeiro. came out years ago and I think they are "all to the berries" Reception and Exchange of International Programs: (if you'll pardon my French). With great success we have very frequently received and To date I have built and used nearly all test equipment relayed programs from other countries. Among these we and literally hundreds of various hookups, and while some may mention England, France, Italy, U.S.A., Germany, of them had an error or two in the diagram, I have never Argentine, Uruguay, Spain, Portugal, etc. For these re- been stumped, and have not had a failure yet. I have lays special high -gain superheterodyne receivers together no kirks to make. with "double -vee" directive antennas are employed. I opportunity take this of thanking the whole staff, for Listeners' Reports: Listeners' reports will be greatly ap- their fine elope and wish them many years of continued preciated. Correspondence should be addressed to: success. Short -Wave Station, JACK GEIER, Caixa Postal 709, <% Valley Radio Shop, Rio de Janeiro, Brazil. Suu Fcrarntdo, Calif. e hope that this information will be of use to the readers of RADIO- CRAFT. J. C. BRAGGIO, Contn,'l. .1/yr.. PSK -PRF -5 RIO DE JANEIRO Cotapathia Radio Iiiteraariaurl Ile Brasil, Editor, RADIO- CRAFT: Caixa Postal 709, For your information and in case it is of any use to you Rae Vise. Inha,íaat, 6i -40, for publication, I tender a few details of PSK -PRF -5, the Rio de Janeiro, Brawl. "I.T. & T." short -wave transmitter of Rio de Janeiro which I have seen mentioned repeatedly in your columns (some- We are sure that owners of short -wave and all -wave times erroneously by our old call sign PRBA, or by PRA -3. receivers will be interested in the above information con- the call sign of a medium -wave station we frequently cerning this transmitter in the jungles of Brazil. Un- relay). doubtedly, the operators of this installation will be "tickled Operating Company: The transmitter belongs and is pink" to receive reports from listeners, and we urge our operated by the CompanhTa Radio Internacional do Brasil readers to give these boys some consolation in their (a member of the International Telephone & Telegraph isolation. Corp.) and is employed regularly for the international (Confirmed on page 437) telephone service to New York, Buenos Aires and Madrid, View of transmitting station located at Marapicu near Rio de Janeiro, S.A. and from these points to the rest of the world, and also for Directive antenna arrays to Madrid in background. Thick jungle had to be special short -wave broadcast programs. cleared to build this station. Operating Schedules: International telephone daily channels and special programs through the following stations:

FREQ. W. L. IN CALI. MISC. IN KC. METERS LETTERS REMARKS 21,080 14.23 PSA Tele. to New York 14,690 20.4 PSF Tele. to Buenos Aires and Madrid 14,935 20.7 PSE Ditto 10,220 29.35 PSH Tele. to Madrid 1111. : 1ç.1 9,505 31.5 PRF-5 Special Broadcast ! Programs 11 1!_ =1=_t_" 8,185 36.65 PSK Tele. and Special j 1 Night Programs to Buenos Aires

RADIO -CRAFT for JANUARY. 1935 415 A REAL "HOW -TO- BUILD" ALL-WAVESERVICE MAN'S OSCILLATOR Here is what all Service Men have been looking for! A really complete article on

building your own I I O V. A.C. -D.C. all -wave oscillator; all fundamental frequencies from

7 mc. to I 10 kc. HOWARD J. BENNER

THE TREND of the radio market next to impossible and proper tracking dummy antenna but has effectively a toward receivers having more than becomes difficult. higher impedance, and 400 ohms is con- one band has created a serious This article presents a simple and sidered the proper match. problem for the Service Man. He inexpensive A.C.-D.C. all -wave service Figure 1 shows the circuit diagram. is confronted with the problem of serv- oscillator or "signal generator" which As can be seen, the instrument consists icing all -wave receivers with equipment the Service Man or amateur can easily of four units. These are: (1) the oscil- that was designed only for the broad- construct. This instrument is not of lator; (2) modulator; (3) attenuator, cast band. The use of harmonics has the usual type that works on harmon- and (4) power supply. been one way out of this problem, but ics, but instead supplies fundamental The oscillator circuit uses a type 77 at higher frequencies the harmonics are frequencies, and is in every sense a tube operated as an electron -coupled so close together that a calibration is laboratory instrument. oscillator. The control -grid, screen - The output control completely atten- grid, and cathode are used as the oscil- uates the signals, and no signal is evi- lator elements. The plate is used only dent even on the ultra -sensitive receiv- to couple the generated signal to the ers of today. This has been accom- output posts. The oscillator is of the plished by effectively filtering the line familiar Hartley type with the tuned and completely shielding the generator. grid coil tapped to provide feed -back. A shielded lead from the signal gen- This type oscillator with the advantage erator to the receiver must be used to of electronic coupling has proved very reduce stray field. For use on the satisfactory, since a variation of output higher frequencies a 400 -ohm resistor is load, even at the highest frequencies, placed in series with the "hot" lead has little reaction on the oscillator. from the generator. This is necessary This is accomplished as a result of the because the average antenna does not suppressor -grid being tied to the screen - Here is how the parts should be placed have the characteristics of our usual (Continued on page 434)

Fig. 2. Building and drilling the chassis. Fig. I. Wiring diagram of osc'llator. Fig. 3. A- modulation transi.; B- cover. 110v,AC-DC. it, 1r il 1 t WOOD IN GLACE 25MF. +' ÓÑMS .:.E /20W OF -E - LAMINATI0r/S

r I ORIGINALE ¡ LAMINATIONS -A- 0.1-MEG 10,000 ONMS 2575

I H".OIMF.

D DO 0.4 i, 16 2 TRñÑS MF.

MMF J I 76 s .l} $MF ' 100 IFI OHMS - 2000 ILTER \ /, OHMS HOKE A D w1i':la!I+ u. ri-4Y i+II44-

II' .25 7 RED Dot tOR IDENTIFICATION C 21_x3 r .225 PAF -B- j R El w,..,., _.:.r. HmS A,,-,.X '? (Awl s OA 1 I g -. 250 LUG LAYOUT LOOKING -I NOTE HOLES MARKED -A- MUST COINCIDE WITH Mw MAr¢r THE EIGHT .093' HOLES IN THE DNDcum, - Lwow AT COIL FROM BASE l- CHASSIS 416 RADIO -CRAFT for JANUARY, 1935 MEN'S SERVICE AS ßa 0 SO eb. A` MEMBERS'/ . / FORUM This department is devoted to members and those interested in the Official Radio Service Men's Association. It is the medium for exchanging ideas, kinks, gossip and notes of interest to those who comprise the membership.

SOMETHING WRONG? I enclose a picture (shown below) which shows the RADIO -CRAFT, ORSMA Dept.: panel (center) with the dynamic and magnetic speakers In the course of the last year or so I have had a good on the panel above. These speakers can be arranged for many car radio sets come into my service shop with stuck use on any radio set I might receive for servicing, by vibrators. Apparently the sets have been O. K. other- means of various field coils brought out and connected in wise. At the present time I have a Philco N, an Atwater series (with proper cores) by means of phone -tip jack Kent 424, a Ford Majestic and a small G. E., all with the connections between each coil. This permits any resis- familiar trouble of a sticking vibrator. tance unit to be "thrown" into a set circuit where neces- Surely there must be something wrong that I am miss- sary. Also, tips are provided for connecting the voice ing as it wouldn't be likely that all these power units are coil to the output of the set with clip connections. Where defective, and as many are only a few weeks old it can't the set carries no output transformer, arrangements are be because they are worn out. made by a switch and jacks to connect a transformer I would like to know if it is advisable to clean the con- behind the speaker panel to the set and speaker, thus pro- tact points, readjust the contact gaps, etc., as a remedy viding coupling. or if it is best to replace the entire assembly. It has been All parts used in building this board are parts of old test my experience that replacing the entire unit is the only units or parts thrown around the junk box. The only part remedy after the points have become pitted. bought was a new multitester unit. This can be connected JESSE SMITH, Ja. to the board by "loop wires" with phone tips. A ten wire cable connects from plug (6 -prong with phone -tip center Here is a question which has stumped many a Service jack) to panel sockets, -one each of the 4, 5, 6 and com- Man. What do other members of the ORSMA think about posite 6 -7 sockets, each socket lug hooking into phone -tip this letter. Are the sets at fault? Is it best to replace jacks shown in line at the bottom of the panel. The the entire vibrator assembly or can the units be repaired cathode, plate, screen -grid and suppressor-grid lines can to the advantage of both the Service Man and the cus- be opened by toggle switches. I have the filament lines tomer? These are questions which can be settled best by going to a 0 -15 volt A.C. meter, the screen -grid and plate the opinions of other members who have experienced the lines looping through a special 3 -way switch (from the same or similar troubles. junk box) one for each circuit -to the milliammeter. This The opinion of one auto-radio expert is that wherever arrangement is necessary because of using one meter for the aforementioned trouble occurs the best remedy would both screen -grid and plate -to keep them separate. The be to replace the entire vibrator assembly. His expe- meter is 0 -20 -100. I use two large and two small push- rience has been that the early models which incorporated buttons, shown under the meter (center top) one large such devices have always given trouble due to design and one small for each circuit, the large one reading kinks which did not develop the higher scale, and A complete test panel for th e shop, built by one member. the until the sets were placed in smaller the lower scale. A the field. Since then, im- push- button under the fila- } proved vibrators have been dIV ment A.C. meter cuts in this developed, which, when in- meter across the filament stalled, will eliminate almost circuit. completely this type of trou- On this board is provided ble. an output meter with two ranges, which is more easily A VERSATILE TEST PANEL accessible than changing the RADIO- CRAFT, ORSMA Dept.: multitester, as well as a Knowing your interest in separate 0 -200 D.C. volt- the Service Men and their meter (upper left) and a problems, I feel that you 0- 10,000 ohmmeter. These will be interested in an up- are brought out to phone to -date test panel which I jacks in line with the other use in my service shop and tip jacks. which has been just com- The large Weston meter pleted after several weeks of is a heavy duty type, used drafting and study. (Continued on page 425) RADIO -CRAFT for JANUARY, 1935 417 THE ANALYSIS OF RADIO RECEIVER SYMPTOMS OPERATING NOTES

the cathode leads had opened inside the WHAT THIS DEPARTMENT tube. This receiver uses the 25Z5 as DEFECTIVE TUBES IS FOR two half -wave rectifiers, one -half sup- - plying current to the speaker field and Are not to be considered as It is conducted especially for the other half to the tubes. the subject for an Operating the professional Service Man. In An emergency rapair due to lack of Note. is all it will be found the most unusual a 25Z5 tube was made by connecting It assumed that Serv- troubles encountered in radio the 2 cathodes together. This put the ice Men test tubes when making service work, written in a prac- tube load in parallel with the speaker a service call. Their experiences tical manner, by Service Men for field portion of the rectifier. No harm on the subject of testing tubes, resulted by connecting in this way and you. unless most unusual, are not of the receiver worked fine until a new Have you, as a professional tube was procured. sufficient interest to other Service man, encountered any unusual Difficulty in tuning to and holding Men. Operating Notes should be or interesting Service Kinks that a station was traced to insufficient confined to those faults which are may help your fellow workers? tension of the springs on the tuning characteristic of, and repeatedly If so, let us have them. They will condenser rotors. be paid for, upon publication, Soldering pigtails eliminated this occur in connection with a par- at regular space rates. trouble. ticular model of radio receiver. MARIO BORDUCA

STEWART -WARNER MODEL 116A 275 V., but 400 V. jobs were used for "NEW YORKER" (U.S. RADIO & replacement. Placed in operation, THIS is a broadcast receiver incor- TELEVISION CORP.) porating a police band, and using a after the field repair and condenser has a set come in with so renewal, the set was practically dead! 6A7 first -detector and oscillator. The RARELY complaint was, "no reception on the much wrong with it. Receiver re- Cause: a shorted 0.01 -mf. R.F. cathode broadcast band, accompanied by noise ceived dead. Due to an open 5,000 resistor bypass condenser. Theoreti- at several positions of the station se- ohm section of the voltage dividing cally, this should give maximum vol- lector." See Fig. 1. system, i. e., the 5,000 ohm section of ume as it gives no bias and hence high After testing all tubes and checking the two fields. Symptoms, no screen - plate current in the R.F. 24A, but such socket voltages a continuity test was grid voltage on either 24A and no con- was actually not the case, perhaps due made on the coils in the radio -fre- trol -grid bias, and hence high plate to overloading. Be this as it may, re- quency section which revealed an open current in the 71A- nearly 40 ma. By placement of this condenser was in section of the antenna coil. This coil careful inspection of the removed field order. On the usual routine test of is wound with large enough wire to be coil the break was located approxi- all condensers it was found that re- easily rewound. mately 2,400 ohms in from the outer placement of the following condensers CHESTER MCCLINTLOCK end of the coil, and at this point, only, was necessary: a few turns were lost until the con- (1) the above -mentioned R.F. tinuity was again picked up from the cathode bypass, 0.01 -mf.; the 0.05 -mf. BEST 4 TUBE MIDGET inner end of the coil, and the two sec- detector control -grid to cathode iso- receiver uses 6C6, 6D6, 43 and tions soldered together. Corrosion lating condenser; the 0.1 -mf. detector THIS25Z5 tubes. Receiver was dead as far probably caused the trouble. For screen -grid bypass; the 0.01 -mf. de- as signal was concerned. Speaker had schematic see Fig. 3. tector plate to 71A control -grid cou- an alive sound. Refer to Fig. 2. Each electrolytic condenser was pling condenser (a 600 V. job here) ; No voltage anywhere except at drawing far too much current and the and the 0.1 -mf. 71A control -grid resis- speaker field. Trouble was found to be two were replaced to avoid trouble tor bypass. All were leaky, and except due to defective 25Z5 tube. One of here. Originals were each 8 mf., (Continued on page 443)

Fig. I Fig. 3 Stewart.Warner 116A; noisy, no reception. Troublas in a "New Yorker" (U.S. Rad. & Telev.) were traced to I sources.

INTERMITTENT TO BREAK 6A7 a OSC 6 DET 1 WAVE CHANGE SWITCH T ro WAVE-CNANGE AVC SWIT H CRCJI?

Fig. 2, below. Best 4 tube; fading.

418 RADIO-CRAFT for JANUARY, 1935 129 Radio Service Data Sheet

RCA VICTOR MODEL 102 4 -TUBE A.C. -D.C. T.R.F. RECEIVER (Incorporates wide tuning range: 540 to 1,712 kc.; A.F. power output, 0.18 -W.; circuit permits compact chassis design.)

Following are ope rat ing solda ge and Cur- The receiver is aligned at 1.400 kc. for This set is observed as being one of the rent figures for this set, measured to K. or maximum output. Align the tuned cir- most simple and effective designs that can fil. cuits with the trimmers in position of mini- be produced. A single, type 78, variable -mu mums rapacity. After alignment. check to pentode, V1, is coupled to a type 77, non - Tube C: G. S. -G. Plate Plate sure that a 1.712 kc. signal can be variable-mu V2; the A.F. output Type Volts Volts Volts Ma. make pentode, heard when the main tuning condenser is of V2 is amplified by the type 38 tube, also VI 2.5 105 105 7.0 near its extreme minimum position. Power a The 37 rectifier furnishes ade- V2 2.0 17.5 40 0.1 pentode. consumption. 40 W. quate current for this combination. Inas- VS 10.0 100 95 5.5 Care should be taken to avoid much as a tuned radio frequency circuit is V4 16.0 restriction 115 of natural ventilation as would occur with utilized there can be no whistles of any () Impossible to measure on ordinary the set resting upon or placed close to a sort when turning across the scale as often voltmeter: () r.m.s. Above voltages for radiator or other heating device. occurs in sets of the superheterdyne type A.C. will he approximately 5'b lower on 115 In most localities the 20 ft. antenna lend which incorporate only a limited number of V. D.C. Measure at maximum volume. of the set will provide StrtR tient pick -up. tubes.

C16 CIO MAGNETIC REPRODUCER. 300 A.F .00O24-MF 1 DE MMF .0024 -MF 1 78 77 3.8 371 RECT. C2 Cl CS C7 4-30 14-405 4-30 14405I +1` NMF I uMMF\MMF -1.2MMF .SR+ ÉG 1 't5 ( R6 .1jo6- o- I.MEG MGI

(7e) -R4 I r161UII* 2 MEGS O (5 OMMS C13 CI< 315 4MF __i FC..) ev C5 5w y -+ °`MF[[ 1A,{110V, C- 05-MF = 0C CMA5515 - R2 0.35-MEG !r/

GENERAL ELECTRIC TABLE MODEL M -49 4 TUBE RADIO -PHONOGRAPH DUAL -WAVE SUPER. (Features: frequency range, 540 to 1,500 and 1,600 to 3,500 k.c.; A.F. power output, 1.9 W.; tone control; phono. is 78 r.p.m.)

Following are the operating voltage and Second- detector coil LI is tapped su that The Synchronous motor used in this in- current figures for this receiver, at 120 V. the tuning range may be extended merely strument is of simple design; the two stator line potential; maximum volume setting of by shorting out a portion of the coil. The coils are connected in series and the motor 126. and no signal. Measure tu cathode. oscillator circuit is not tapped, the high - is started by giving it a clockwise spin by frequency range being obtained by use of hand. If it is found difficult to start, or Tube C'. -G. S. -G. Plate Plate Type Volts Volts Volts Ma. its second harmonic instead of the funda- if it runs at a sub -synchronous speed such as at 70 V1 1.25 70 235 2.5 mental for obtaining the I.F. r.p.m.. such action may result from 180 3.5 Align at 1.400 and 600 Ice. one of the following causes: VI - to V2 1.25 70 235 5.5 The magnetic pickup and tone -arm as- Difficult Start: May be due to stator of and unique con- failing to rotate on outer V2" 19 145' 0.4 sembly are new design bearing (due to - mainly spaghetti sleeve being V3 17 240 230 26.5 struction. Service work will consist jammed in the slot, of centering the armature, replacing the or sticking to the resilient bumper). Outer V s - 335" 50.0 rubber pivots, and replacing the magnet coil. bearing may not be properly lubricated. See A feature of the power supply circuit - Care should he taken to avoid restriction that the ball hearings are at the bottom or only one secondary is used in power auto - of natural ventilation through the cabinet the main assembly. r'ansformer P.T. This is accomplished by as would occur with the set situated so Slow Speed: Lift tone -arm from turn- basing a cathode -type rectifier, series fila- that its back is flush with a wall of the table until motor reaches normal speed. ments, and taps on the secondary of P.T. room or with the instrument resting upon At 125 V. the motor consumption is 4 W. () Oscillator section; () second -de- or close to a radiator or other heating de- Do not turn on motor with rotor removed re,lor section; (') actual voltage cannot be vice. Black wire connects to antenna, and as the heat rise will be er:cessive. r, awured ; ( ") r.m.s. yellow, to ground.

ANT. r Cap DET.2 L I.F. C17 RECT. SV T. =EG-, 85-170 85-170 (6F7 .05MF 41F .ti3F (3.8) w3 lam MMF MMF L FT .2 .MF 1r17 MMF i .F DET I605C. ( 647 Ir I (44) I I TI a (SS) III

~ 1 ` ' (IS) d 1.31

wó C13 C14 i }s 4 as. 5 MF. , o.t- RII MF CI T C19 500 OMMS C1 .25- S.MF. Ol- C3 F MF .0015- J 112) MF. MF PKTNF' T3 (i00) ' ' RI 0.1-MEGy: CttttGMF"tttt "'GPO I.F=46OSC R aM12 (s085) 20,000 ZS WO 0MM5 t E G 014M5

RADIO -CRAFT for JANUARY, 935 419 RADIO- CRAFT'S SPECIAL NOTICE Those questions which are found to represent the greatest general interest will be INFORMATION BUREAU published here, to the extent that apace permits. (At least 5 weeks must elapse between the receipt of a question and the appearance of its answer here.) Mark such inquiries, "For Publication," Replies, magazines, etc., cannot be sent THAT REMOTE SPEAKER (A.) We do not know of any really effective C.O.D. Back issues of RADIO -CRAFT 'loudspeaker" circuit utilizing the 1A6 pentagrid prior to December, 1932, are available at (300) Mr. Lee C. Davies, Imperial, Pa. converter tube. You see, this tube does not have 50e per copy; except the following issues: (Q.) In the department, Short -Cuts in Radio, satisfactory output characteristics for matching 7/29, 2, 3. 4, 6. 7, 9 and 11/'30: 5, 8 and in the October 1934 issue of RAOto- CaArr. page into a loudspeaker as the output "load." In- 9/'31; and 10/'32, which are out of print. 225, is shown a circuit to permit a remote we Succeeding issues are still available at the stead. recommend the circuit shown in Fig. regular price of 25c per copy. speaker to be controlled either at the radio set Q.302, which utilizes a type 19 tube. I see how, Inquiries to be answered by mail MUST or at the speaker. However, fail to This tube, too, is in the 2 V. class, but is be accompanied by 25c (stamps) for each if the extra speaker is wired in such a manner, well- designed for operation as an output device. separate question; answers are subject to it would work. Is the circuit correct as shown? In addition. having two triodes in one envelope, subsequent publication if considered of (A.) We thank you for calling, to our at- exceptional interest. this tube is well adapted to the special circuit Furnish sufficient information (in refer- tention the diagram in question which, unfor- shown, in which one section of this tube is used tunately, is in error; a correct version is shown ence to magazine articles, be sure to men- as a triode regenerative detector, and the other tion issue, page, title, author and figure in Fig. Q.300. section is used as a triode A.F. amplifier. The numbers), and draw a careful diagram use of plug -in coils permits all -wave operation (on separate paper) when needed to ex- plain your meaning; "BUILD THIS ALL -WAVE SET" from 15 meters to 550 meters -and higher, if use only one side of suitable coils are used. the paper. List each question. Be SURE (Re. "B" Unit) to sign your name AND address. (Note that this is not a "reflex" connection. Enclose only a STAMPED and self -ad- (300) Mr. E. E. Randall, Mattoon, Ill. inasmuch as each set of triode elements performs dressed envelope for names and addresses (Q.) In the November 1934 issue of RADIO - only a single function in the circuit -the dia- of manufacturers; or, in connection with CRAFT, in the article, "Build This All -Wave Set," gram is reproduced by courtesy of SHORT WAVI correspondence concerning corrections to is the wiring of the supply shown cor- CRAFT magazine. The cost of building this set articles, as this information is gratis. power Individual designs can be furnished at rectly? Are the plates of the type 84 rectifier is next to nothing.) an additional service charge. The fee may in the tube -type "B" supply unit, that operates It would be a "wise stunt" to mount the be secured by addressing the inquiry to the from the 6 V. "A" supply, shown correctly antenna trimmer right on the front panel where SPECIAL SERVICE department. and fur- wired? I am building this set and want to be it would be easily accessible. The value of the nishing COMPLETE specifications of de- sure that it is wired right, inasmuch as the set grid leak shown as 3 mega. should be varied to sired information and available data. itself is just what I have been looking for. meet individual requirements; once set, it should (A.) Although the diagram of the "B" sec- not again require adjustment. tion of the unit is correct according to the original copy, we find upon further checking "WIRED RADIO" "The Commission has no special regulation that this portion of the circuit is incorrect. A LAWS with reference to wired radio, but investigation revision is shown as Fig. Q.301. Note that, now, (303) Mr. John Butterworth, Pasadena, Calif. has shown that in all cases where wired radio the plates of the rectifier connect to either end (Q.) In the November 1933 and several sub- operations were being claimed they were merely of the high- voltage winding of Ti. and that sequent issues of RApto-CRAFT, have been de- radio stations emitting signals into the air as "B-" now connects only to the centertap on scribed radiophone equipment designed for any other radio stations. Under these circum- this winding, the two buffer condensers. one operation, over the electric light lines, on the stances they were all subject to regulation by side of the filament of the 84, and the low - principle of "wired radio." Does operation of this Commission. potential leads of the two 25 mf.. 25 V. electro- this equipment come under the jurisdiction of "The mere fact that these stations may lytic condensers. A point of interest in con- the Federal Radio Commission? operate outside the broadcast band would not nection with this circuit is that, at first glance, (A.) In this connection we are advised by exempt them from Commission regulation. The choke an R.F. (connected to the cathode of the the Federal Radio Commission, as follows: on page 425) 84) appears to be the only A.F. filter unit in (Continued the "B" circuit; however, the fact is that the 1,800 ohm field coil, which is bypassed by two S.P. D.T. 8 mf. condensers, in the receiver circuit supplies TOGGLE OR the requisite filtering. KNIFE SWITCHES

I TUBE LOUDSPEAKER ALL -WAVE ) SET (The "Twinplex ") (302) Mr. Marion Stine, Somerville, N.J. (Q.) Is it possible to make a "loudspeaker" set using only drycell tubes of the 2 V. type? EXTRA" _-- I would like to be able to make such a set if RADIO SET SPEAKER it is not too complicated. Most of the circuits I have seen, and which are capable of giving "decent" volume on the loudspeaker from local Fig. 9.300, above stations, have required at least 2 and usually 3 Off -on operation of remote speakers. tubes, but it seems to me that the old Arm- strong or "Ambassador" regenerative circuit Fig. 9.301, right could be used to advantage in some really modern Correction of vibrator -type "B" unit. circuit utilizing one of the new multi -purpose Fig. 9.302, below

tubes, such as the 1A6. A REAL I Tube "loudspeaker" set.

C7 C3 C5 ANT. IOO MMF. .O1-MF MMOF 19 L i Ìt

95 M MF Cl R4 I R1 MEG RS 3MEGS 0.1.-MEG. o ANTENNA i TRIMMER 7p PN0NE5 T C2 g 14GMMF TUNING 6, CONDENSER. O.l. MF. GNO. R3 _i C4 'A+' ós MF "R650.000 R-' OHMS R2 REGENERATION 20 OHMS CONTROL iWvdW B- VOLUME CONTROL --V 90V. i

420 RADIO -CRAFT for JANUARY. 1935 RADIO -CRAFT for JANUARY, 1935 LATEST IN RADIO -103) l Cun(i,00U from pnyr MEN VOTE FOR HIGH -FIDELITY 15 W. SERVICE AMPLIFIER (622) (Marto Products Co.) AFREQUENCY range of 60 to to 12,000 cycles, at high fi- THE BURGESS 8 HOUR DAY delity. is claimed for this 4 -stage amplifier: the figures are given on the basis of a 2% + power DOUBLES THEIR. at 5% maximum har- A 3 -tube sort -wave set. (621) variation, monic content. The tubes are ar- ENJOYMENT ranged as follows: type 57 first voltage amplifier; 56, second voltage amplifier; 2A5, driver; two 2A3s, class A prime power output. Chassis incorporates tone and volume controls.

"FREE REFERENCE" ANALYZER (623) (Radio City Products Co.) Hi-fidelity, IS W. P.A. unit. (622) AN EXTERNAL, multi -range meter, and this new analyzer unit, and you are all equipped for making practically any circuit analysis. Connect set and analyzer via the 10 -wire, 6 -ft. cable, then rotate the two switches for voltage, current. or resistance measurements between any two circuits, or any circuit and ground ( "free reference "). Available in kit form, or completely assembled, wired and tested.

AIRCRAFT -BROADCAST "Free reference" analyzer. (623) A.C.-D.C. PORTABLE (624) SERVICE MEN AIRI'LANE travel has shown the need for accurate knowledge KNOW that many of weather conditions at air -ports ahead. To meet this need a port- owners of battery - able, 6 -tube, 110 V. A.C.-D.C. su- operated sets still perheterodyne has been developed have the old- fashioned which enables the owner, en- sconced in his hotel room, to tune belief that batteries in the Department of Commerce give fewer hours of weather and other aircraft data on the 140 to 375 lie. (2,142 to 620 service when used meters) band. A switch provides more than 3 or 4 programs on 500 to 1,500 kc. (600 a day. to 200 meters) band. Set incorpo- hours That rates a tone control, A.V.C., built -in belief has been exploded by B ' GESS engineers. Re- aerial, and dynamic speaker. in use have Aircraft- broadcast set. (624) peated tests in our laboratori and actual proved that you can use BUR SS Batteries 7 or 8 hours MODERNIZING SERVICE a day -and get maximum se ice!* (625) INSTRUMENTS tell your (Precision Apparatus Corp.) When battery- operated set need new batteries, SERVICE Men will be pleasantly customers about the BU ESS "8 hour day ". They will surprised to learn thut their be glad to know they c n double their enjoyment at no old test apparatus, now beginning to exhibit increasing inadequacy, increase in their batter cost per hour! may be modernized. A Jewell type 538 tube checker, modernized by a Owners of 2 -volt se can buy 400 hours of dependable company that specializes in doing the B GESS Power House for only $ 3.20. this sort of work, is illustrated. "A" power in Job includes complete new wiring, The Power Hous is 100%. DRY, requires no attention on Above, modernized checker. (625) and provision for double test and is not affect by weather. Like the world- famous all dual -purpose tubes and full - wave rectifiers. New molded sock- BURGESS "B" nd "C" Batteries, it costs no more per Below. 6 -tube all -wave set. (626) ets, a new filament transformer. hour when operated 7 or 8 hours a day. and new engraved metal panel COMPANY, were installed. Other makes and BURGESS BATTERY models are similarly imi ror, d. Freeport, Illinois.

5 -TUBE ALL -WAVE For economical operation of SUPERHET. (625) 7 to 8 hours a day, sets should (Pilot Radio Corp.) be powered by batteries of LL -WAVE reception over the proper capacity. Set owners range of 16 to 660 meters ie should ask their Sers ice Men to notA the only feature of the newest recommend type and size of bat- in 5 -tube, 110 V. (also. 125 to 240 teries best suited for their use. V.) 60 cycle supers. (Export model: 16 -55, 168 -550, and 835 -2,000 meters.) The cabinet, for instance, is acoustically designed; vernier - dial action permits either 10 -to -1 or 80 -to -1 tuning ratio. A phono. pickup is provided; also, A.V.C.. and a tone control. Tubes (one BURGESS each) : types 6A7, 6D6, 75, 80. and 12. BATTERIES AND FLASHLIGHTS Please Soy Thot You Saw It in RADIO -CRAFT Radio Service Data Sheet 130

STROMBERG -CARLSON NO. 69 4 -TUBE ALL -WAVE SUPERHET. SELECTOR (CONVERTER) (Frequency range: 1,500 kc. to 25 megacycles; makes any broadcast set an "allwave" receiver; power consumption, 28 W.) Voltage readings are obtained by mea,ur- The manner of connecting the combination Sections T of the 7- section ing range switch between the various tube socket con- inverted -L and doublet antenna system reconnect to the primary windings of the tacts and the bases with the tubes in place. commended for use with this type of short- R.F. inductances in the converter. Figures Sections are given for a line voltage of 120 wave converter is described in Part II of B connect to the secondaries of these coils. V., using a high -resistance meter. Measure the article, "Important Facts About the In the operating position for a given range. on Range B, at 2,400 kc. New All -Wave Antenna Systems." (RAmo- the range switch shorts and grounds the ad- CaAPr, Tube Sup. -G Cath. Plate August 1934, p. 84) ; note Fig. 7 jacent unused grid inductances. This pre- Type Volts Volts Volts Volts Volts in the article. vents "dead spots" and erratic operation. VI 0 103 2.9 2.9 191 Position A of the range switch establishes The use of the stage of tuned radio fre- V2 0* 103 103' 3.1 191' a straight -through connection from the an- quency amplification ahead of the first -detector or V3 14 - 0 160 tenna to the standard broadcast, 200 to 660 modulator tube is an extremely V4 207 178' meter receiver with which the selector or important factor in preventing cross -talk converter is being operated. The and image -frequency reception. Modulator grid: G2 (G1, V., output of () () -1 the selector, at 545 kc., is fed A double superheterodyne receiver results approx.): (') modulator ( through a plate; ") A.C., when this selector is connected to a - per plate. grounded shield; one output lead connects super to the antenna post het. receiver. The first auperhet. action A bank of individual coils is used to ob- of the set, and the other connects to the ground post. is in the selector. and the second in the retain complete coverage at maximum ef- ceiver. Consequently. both ficiency. over units moist be the wavelength range of 12 Condensers C31 and C32 bypass line in- tuned exactly to resonance tu prevent cut- to 2011 meters. terference due to refrigerators. lights, etc. ting sidebunds,

RECT.

ItOV,AC 7r

PILOT MODEL 63 ALL -WAVE 6 -TUBE SUPERHETERODYNE

(A.V.C.; tone control; phono. pick -up jacks; frequency range, 16 fo 550 meters; A.F. output, 3 W.)

Operating voltages for this receiver are To align the I.F. circuits turn the hand - 00,/ USA INN 720V 240, given below. Use a high -resistance meter. selector switch to "Broadcast," and connect the service oscillator to the control - ÓAwD Tube Cat h. Plate grid of V3. a fixed UOACIToR pT Type Volts Volts Volts through condenser of .002 The VI 90 4.0 -mf. return of the service oscil- 235 lator connects to the receiver ground. V2 90 4.5 235 After 11111 alignment of I.F.T.2 feed the oscillator output V3 90 4.0 235 to the control -grid V2. MÓ VJ 1.5 120' of and align I.F.T.1 rli,on for maximum output. Repeat CI- V5 230 14.0 210 procedure. REAR VIEW SeEAKER To align broadcast band, connect service SOCKET (1 Voltage measured through a plate re- oscillator to antenna and ground posts, turn sistor of 0125 -meg. Speaker field. 110 C7 Ca V. range switch to "Broadcast," and align os- All plate and screen -grid voltages are mea- CI cillator, interstage and antenna trimmers I sured to cathode; cathode voltages are mea- at 1,400 ke.: and oscillator CIS gadder at 600 sured to the chassis. kc. Repeat procedure. Rock C2 - tie tuning control C19 The power consumption of this set is 70 while aligning gadder. W.; Illt' the undistorted power output is 3 W. Align bands 1 and 2 at service oscillator C3 - C21 If it becomes necessary to realign the set, frequencies of 17,800 ke. and 6,100 ke.. re- be sure to reconnect the speaker cable to spectively. setting the receiver dial at 16.8 C9- SÉw the receiver after having removed the chas - and 49 meters, respectively. .sis from its cabinet, before connecting to There are no padding condenser adjust. prover line. ments on short -wave bands 1 and 2.

0 13.,0 4Kr1 A es DA S .2a O3c OF.1.toOVr1 a2 RF S. Ll [FTI tiT.2 is 66 11 1D OCt] Rcawx`r.a rs / \I 1 á} W

CS S.wr 0:ï 00v 20" ACO GAO O.S "to 50 000 DT r:22.?? r O88S e1 -Kc ou-s r 01 T.+ ]Mi - . 5v C,trr) 4i5vr4tG.

}wi C vom é4: 50.000c.w

ID 1 S.vLMSw]r Ir456KC 1 Sn.`tst s AOto

422 RADIO -CRAFT for JANUARY, 1935 RADIO -CRAFT for JANUARY, 1935 423 RADIO MONTH IN REVIEW (Copt in ucd iront lane 393) Master INTERCHANGEABILITY cruising car and headquarters, just like ordinary telephone communication. Master Units make possible The transmitter used in the car has a TRIPLETT interchangeable y a; LET combinations of test equipment . . a com- tower of 1 5 watts. different plete tester for every purpose. Units nia) he used as furnished, or placed in convenient portable cases holding one. C. F. McCLELLAND two, three or four units. A counter case is furnished for the tube tester unit. Triplett instruments are recognized standards. The are BROADCAST reliably accurate and dependable in performance. These DEAD new Master Units typify Triplett adaptahilit to meet EXECUTIVE es -ers sen icing requirement. Within the past month. one of the outstand- broadcast chain to rival ing hopes for a third Triplett Master Test Set No. 1205 One Unit Portable Case No. 1201 the NBC and CBS faded, with the untimely Takes Any Master Line Unit. Use death of George F. McClelland. includes only- Dealer's net price S1.00 Mr. McClelland. formerly a vice president VOLT -OHM -MILLIAMMETER of the NBC and n pioneer in broadcasting had No. 1200 on his new been working for almost a year TESTER No. 1220 by those in the FREE-POINT chain. which was expected GENERATOR "know" to be the most promising of the ALL -WAVE SIGNAL many attempts made to formulate a new na- No. 1230 tional network. TUBE TESTER No. 1210 As stated in our February 1934 issue. Mr. Complete in Portable Case No. 1204 expected to tackle the problem McClelland Dealer's net price Two Unit Portable front a logical and sound business standpoint Case No. 1202 encountered by Ed -to avoid the pitfalls Takes Any Two Wynn and others who have tried to rival the Master Line Units. "big two." Case only- Dealer's It is with regret that we print this notice net price 51.67 of his death, by his own hand, when the future looked so bright for his "Broadcasting Stations Corporation."

THE LATEST IN POLICE RADIO RECEIVERS (OM t;,,,ttd. frna, pap, 399) front fender of the motorcycle. The sane model receiver is also supplied for use on automobiles. a special bracket permitting the clamping of the receiver onto the steering column post. making an exceedingly compact and unobtrusive installation. Advantages claimed by the inventor include the filet that in the motorcycle model the receiver is ty"Ia on the body of the policeman vibration being largely eliminated by the damp- ening effect of the body. Damage to tubes. condensers and coils often occurs in a few Jaya on the average receiver mounted on motorcycles Four Unit Port- due to the excessive vibration. Attached to the able Case belt with all heavy parts built onto the motor- No. 1204 cycle. it is claimed this model eliminates most Case only -Deal- er's net price trouble of this character. 56.00 Because the receiver is self -contained and not permanently affixed to the vehicle. it is easily accessible for repairs. Naturally various receivers of the same model are interchangeable and earl he used on different mot, ,cycles at differ - ent times. This makes it possible for the motorcycle to be constantly ready for arse. and avoids tieing up a complete motorcycle while minor repairs are being made in a radio receiver. The portable receiver for mounted police is Slant Top Oak similar to the other receiver model, except that Counter Case r No. 1211 it operates from a filament supply of 2 volts with a plate supply of 90 volt. The batteries for this for -IL BE TEST. Three Unit Port. 1R 1210. receiver are enclosed in leather saddle bags. able Case No. 1203 No. Case strapped to the saddle of the policeman. Takes Any Three Master Line only- Dealer's net Units. Case only, 1/valet's net price $4.00 A female plug in the front of the saddle horn Price $5.33 permits instant connection of the receiver worn No. 1200 VOLT OHM -MILLIAMMETER. E.sel' -ive TIC, bó - on the belt with the loudspeaker and the bat- lee double Al' and IN.' tilling instrument. rea,la II Write for FREE an' angle. Nt) TESTER 1d yhll)ERN w'1'rlp d T TI I Literature tery supply. Wads AC and IS' up to lotto 1, In this receiver the horse is used as antenna. IN' milliamperes, 3 no-gamic (:ires output 1' The ohms pet volt resist - '$21 .C7 Triplett Electrical Instrument Co. his sure UC voltmeter hits 2uÓÓ a special connection to bridle giving anse. sealer'; net price ALl V I 103 Main St., Bluffton, Ohio contact at all times. TUBE TESTER. t:n01> and Roll St .. 1. No. 1210 Please send me details on the new Triplett The pedestrian police model uses the body of collage rua Irnl. Te -1i all luter -element -httn -. degree of leakages. Provides separate n *I - F+ Master Line Radio Testing Instruments. the patrolman us the aerial and requires no Easily oprrat ed. ground. The small loudspeaker is worn either Uralrr'i net price 520.00 under the lapel or under the coat of the police- Ne. 1220 FREE -POINT TESTER. used o sets. voltage, tut, man. The power supply consists of especially to acolyte radio Tel lances. continuity, rapacity from Wpm -to -n Address constructed small, light weight batteries, worn DRh plug Maker onncetions and lead wIre-...... _...._.. in a special belt. ealer's net prier $8.33 Na. 1230 ALL -WAVE SIGNAL GENERATOR. receiver weighs only 1 pound and like the t The continuously variable signal. frequent les f, . -- other models is worn on the policeman's belt. to Is %legatyeles, either ma lulatrd The five tube super-heterodyne receiver, bat- Furnished with batteries a d lao T`ai, r:ul netting I ires and six graphs on Iargr -v, teries and loudspeaker together weigh less than chan -. i lr..lrr's net pr l.,' 515.33 the average police revolver worn by patrolmen, R totaling an ounce or two under Sty pounds. Only The Triplett Electrical Instrument Co. Ci;. Stare 67t;; volts of plate battery are used on this model, 103 Main St. MOW, Ohio, U. S.I. I Pease .G,g That Vois SaR lt iu RADIO-C.ADIO-CRAFT I - R T r 424 R A D O C A r f o JANUARY, 1 9 3 5

HOW TO BUILD THE 114 -IN- KEN1-ON iPRODUCTS 2 SHORT -WAVE ELEC- TRIC SET

(eon, 11111( d from pogo 398) of a tandem 140 mmf. condenser gang, one sec- Power and tion of which is constantly in the tuning circuit -the other section inserted at will (in parallel, to increase the total effective tuning capacity) from the front panel by means of a toggle Lcono.n ' switch mounted as shown in Fig. A. Thus. not only does this feature facilitate a wider tun- A Public Address System capable of delivering ing frequency range, but should the constructor desire to use this set for regular broadcast re- 18 watts of undistorted output power. ception (using a broadcast plug -in coil from which a few secondary turns are removed) he Will find that the operation is much more highly -- AUD10 AMPLIFIER Primary Features Are: Rtu- trationenu on efficient and satisfactory. This may be attributed, and left show.. the Amplifier system possesses a gain of 80 db. in engineering parlance, to an "improved" L/C .torii° Amplifier Delivers 18 watts with only 5% total harmonic dis- ratio. . ith the Closet tortion soosed and The unusual sensitivity and volume obtained ,lately enclosed in Input from 200 ohms, 500 ohms or a double -button Its crackled ease. carbon microphone from this set can be attributed to circuit design, l'hetulcesemploy- Output impedance of 4 or 8 ohms and the successful manipulation of the regenera- d in this amplifi- tion which will er are: 2-77:2-45. Total power consumption is less than 100 watts control permit obtaining the Extremely Versatile For All maximum possible sensitivity. Sound Installations Circuit Design Referr.ng to Fig. 1 it will be noted that Can used for the be for permanent installation or two tubes employed are the new "multi -purpose" mobile sound truck. It can be equipped with types 6F7 and 12A7. The 6F7 tube really com- straps to make it adaptable for portable public prises two tubes in one glass envelope. a pen- address work when necessary. Total weight is tode and a triode. In this receiver the pentode approximately 20 pounds. section is employed as the detector. with regeneration. and the triode section as the first audio Complete in Kit Form stage. Thus, two -tube efficiency is obtained from this single tube. The 12A7 also comprises two No. 11 Transformer Kit $23.50 List tubes in one glass envelope. but the type of operation and arrangement of the elements within the tube are entirely different. Here we find No. 11 Accessory Kit List AMPLIFIER 33.00 r a power pentode (whose characteristics are Write today, addressing Dept. RC, for com- The alustrati,m /an ve orne identical with the 38 power tube) and a half - plete literature on KENYON Transformers ab show. the Power wave rectifier all in one unit. 137 utilizing the and other essential radio accessories. Men- with tion your dealer's .same. dutchassis osed power pentode section of this tube as the final ad power audio stage. and the its Tubes half-wave rectifier KENYON TRANSFORMER CO., for rectifying the alternating current, when it is Inc. uad in ithe Po . r Amplifier are: operated from A.C. (on D.C. the direct current 810 Barry St. New York, N.Y. 1 -112. N; continuously passes through the tube) we obtain two -tube efficiency from this single tube. The net total, as a result of this arrangement, is a SERV ICEMEN ,Jf four -tube efficiency front two tubes. No reflexing or other tricks, just a straightforward r. generative detector followed by two stages of AMATEURS and resistance- coupled audio amplification. the final stage being a power audio, and a rectifier for "R" supply -all from two tubes. EXPERIMENTERS The heaters of these two tubes are wired in PAPER MICA OIL ELECTROLYTIC series, thus requiring a filament voltage of 18 V. and a current of 0.6 of an ampere (or 600 ma.). Backed by twenty -five years of scientific This is obtained from the power line by means of a series resistor (325 ohms), or a power cord WRITE research and quality production. One bil- in which this value of resistance is included. No power transformer, or any other transformer FOR OUR lion since 1910. Available at all leading whatsoever, is employed. The 110 V. supply - CATALOG suppliers. Use a C -D the next time. A.C. or D.C. -is fed directly to the half -wave TODAY rectifier section of the 12A7 tube. The efficiency of this rectifier is auch that the voltage drop through it may be considered as being almost negligible. Since resistance coupling is used in CORNELL-DUSILIER the audio stages, no audio transformers are CORPORATION necessary. 4347 BRONX BOULEVARD Two kw- resistance power chokes (only 100 YORK ohms resistance, approx., each) are employed NEW in the filter section. This design. coupled to p/ the use of three electrolytic condensers, completes ``, 1`' Ñp FOR HORT -WAVE the filtering arrangement, as shown in Fig. 1, Ty/ SET BUILDERS and has been found more than sufficient to re- 1WAt NEED THIS BOOK move any trace of ripple or hum. Regeneration is obtained by inductive coupling BOOK Every ee rim ser who hm et ,.r COIL tried to build r. short .seam of the "plate" winding to the secondary or Isnnwe by a rienee. then differ- "grid" winding, It is controlled. however, by ence between good end n a midget 140 mmf. variable condenser (mounted is usually found ill Ff J:: a receiver the P. short w coils. Often you have under the sub-base, as shown in Fig. C) which CATALOG m es, book.. tee-m ., hunt through regulates the amount of R.F. energy existing in to find the information you Chock full of BARGAINS require. The hook W. the plate circuit. Regeneration may also be con- In RADIO SETS. I.ng and been s up rM wt hvi:ne these trolled by the volume control. which is shunted BIG Short Wn ve Apparatus. difficulties. across the plate coil and thus serves as a con- NEW ISSUE Servicemen's Repair anal Re- honk you find every placement Parts. In this m-- trolled short- circuiting device to regulate vol- JUST OUT Electrical slble bit fI information ono coil .Appliances and hundreds of winding. Only the m urne or regeneration. For broadcast reception miscellnntsms sIWCISIs at "dope' has been published. this control will be found considerably more SAVINGS. TREMENDOUS n ions sabr, sit ins not only full instructions on bow m effective for regeneration regulation. It is rec- Get this hug new Bargain Bu,k. It's ahco- wind evils. lout dio,eo.ion.. does el whr. curves. how to plot them. lutely FREE without obligation -just wool by means of which any coil for any particular short wave set can he ommended that the single variable condenser be us your Name and Address on a host card figured in advance.e. m to number of turns. size of wire. spacing e used on short -waves for this purpose, and left There ha* never been dots published In suchoh a idle at maximum capacity for the broadcast band \VRITE FOR YOUR COPY NOW. form e. this. in which case the volume control is used in its God :our .nee of 25e ÿn cash n unwedd U. Stomps WAVE stead. OFF PRESS 2COIL ROOK. Sent to you y eaid. JUST THE It is felt that it is more or less superfluous to CIRCULAR CO.. RADIO INC. Hudson St., New Yark,N.Y. give specific dimensions and layout RC VARICK ST.. NEW PUBLICATIONS,IOIC drawings, 225 YORK since the impression left with the constructors Please Say That You Saw It in RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935 425 is then that this phase of building a receiver is rather critical and therefore must be followed INFORMATION BUREAU precisely. This idea, in this case. is farthest (Continued from page 420) as Shhh! Inasmuch only two tubes are Shhh! from the truth, employed in a apace that is ample for con- principal question is whether their signals may structors to arrange the necessary parts as they be construed to be in interstate commerce, and see fit. For convenience sake, those who desire if so they come under the Radio Act of 1927. to imitate the original as closely as possible "The Radio Act itself does not include the may consult the photographs showing different reception of signals and, therefore, the commis- views of the receiver in Fig. A, B and C. As sion has made no regulations with reference to mentioned previously. neither circuit nor lay- receiving sets. It is understood that some states out is at all critical, and any moderate deviation have passed laws pertaining to this matter but is entirely permissible. the Commission has no record of these." /ndirtidua The above clearly outlines the question of the / //y TESTED List of Parts legal status of wired radio operation. as first for NOISE raised in a letter received Due to the simplicity and excellent choice of from another department of the Federal Radio Commission -Division tubes in a carefully arranged circuit, the parts 0 Field necessary are surprisingly few and low in cost. of Operations, Dallas, Texas-from which we quote, as follows: They are as follows: ELECTRAD One Hammarlund tandem, dual -section, 140 "Your attention is called to the fact that the mmf. (each) variable condenser gang; proposed apparatus" ( "A Wired -Radio Public System," One complete set of plug -in coils (5, with Address RADIO- CRArr, November 1933. (I !! if. i page 272) consists of a simple radio transmitter broadcast coil, 4 only for complete short -wave coupled to the unshielded general lighting system coverage) : of the in which the shielded wires within One single Hammarlund midget variable con- city, VOLUME CONTROL the building act only as a transmission system denser, 140 mmf.; to the open wire leading away. from which 30 by., 100 Two General Transformer chokes, radiation will occur. ohms each; "Several of these wireless systems' have One Hammarlund R.F. choke, 85 mhy.; 'wired been constructed, and put into use in dis- Two Cornell -Dubilier electrolytic condensers, this trict. and a number of people have gotten into 16 mf., 200 V.; trouble as a result of the inspiration furnished -Dubilier electrolytic condenser, S One Cornell by this article in your magazine. mf., 220 V.; "It is suggested that you advise Mr. Freeling" Two 7 prong wafer sockets (small) for 12A7 author article) investigate and 6F7 tubes; (the of the "to the radiating ability of his system when connected One 4 prong wafer socket for plug -in coils; to a house wiring system having unshielded One I.R.C. resistor, 1,500 ohms, 1 W.; wires leading away from it, and to warn your One I.R.C. resistor, .1 -meg., 1 W.: readers of the danger connected with the use of Two I.R.C. resistors, .25 -meg.. 1 W.; this system." REVOLUTIONARY in its operating One I.R.C. resistor, .5 -meg.. 1 W.; Unfortunately, it was not clearly brought out, mechanism, Electrad's new Guaran- One I.R.C. resistor, 750 ohms, 1 W.: in the article, that interference radiation is teed Quiet Volume Control fills a long - One I.R.C. resistor, 2 meg.. 1 W.: prevented by the correct use of R.F. choke felt want. One special (wire -wound) resistor. 325 ohms, placed in the power line. If the building is en- Absolute quiet, smooth, positive control 40 W. size, or power cord with equivalent; tirely of metal construction, it ordinarily is of volume is accomplished for the Two S.P.S.T. toggle switches: sufficient to place these R.F. chokes at the main first One Electrad volume control, 75,000 ohms; power switch. where the power lines enter the time in radio history. Two Cornell -Dubilier tubular condensers, building. If the building is of frame construc- .1 -mf., 400 V.: tion. it may be necessary to place the chokes Built on a Radically New Two Cornell -Dubilier tubular condensers. .006 on the individual floor level on which the equip- mf., 400 V.; ment is to be used, and to limit the radiation by Engineering Principle One Cornell -Dubilier mica condenser. .001 -mf.: controlling the amount of R.F. energy delivered One Cornell-Dubilier electrolytic condenser, 10 by the transmitter. mf., 26 V.: The extreme importance that attaches to this One Insuline antenna trimmer condenser; procedure is evident by reference to the case of One drilled sub -base and panel unit (as shown Norman Cohen of Bridgeport, Conn., who, in in illustrations) operating a "wired radio station," was convicted One Sylvania type 12A7 tube; of operation of a broadcasting station without One Sylvania type 6F7 tube; a license from the Federal Commission. De- Miscellaneous supplies, such as wire, hardware, fendent Cohen claimed his broadcasts were vernier dial, etc. carried only on the wires of a Bridgeport power company, but Government witnesses said they Resistance element PIogtbrp ron t a e t Conclusion were able to hear his programs without any baked on flat outer shoe glides t,rrr rc- hook -up with the lighting company's lines. riot of Bakelite P(Ptgare ,,i, lrrrlt irl This receiver, if wired carefully and as per ring straight path Fig. 1, should operate to the complete satisfac- Actually, the facts of the case were approxi- tion of any constructor. The adjustment of the mately as follows, according to the recollections antenna trimmer condenser may be rather cri- of Assistant U.S. Attorney George H. Cohen: More even distribution of current, tical if an antenna system of relatively long "Cohen was charged in an indictment contain- smoother control and longer life are at- dimensions is employed. For best resulta use a ing two counts. the first charging him with tained with this construction. Molded operating a radio station without obtaining a short overhead wire (about 35 ft.) placed as Bakelite case, when mounted, projects high as possible. radio station license, and second -with operating radio station having a radio only one -half inch behind panel. New To those who encounter any difficulties in the a without operator's license. He was found 'guilty' on Type power- switch (approved by rnuler- construction of this set, or who find the results instantly attachable. Long not up to or desire any further particulars both counts after a trial by Jury. writers) par, easily All standard relative to this set, the writer will be glad to "The testimony showed that in spite of the aluminum shaft- cut. give any desired information, and will welcome fact that Cohen was attempting to send his pro- replacement values. Mail coupon for queries. grams through the wires of the United Illuminat- descriptive folder. ing Company, radio signals were picked up on radio receivers which were not connected with the electric wires, and furthermore such signals were picked up by similar sets in Long Island, ORSMA- MEMBERS' across State lines. /WM-- "Cohens experts attempted to prove that it is FORUM possible to send radio signals through wires and RESISTOR (Continued from page 417) confine these signals to the wires. but this was by means of the double -pole double -throw disproved by Government experts, particularly when the signals are of the strength of a very switch shown, to measure voltage from an ex- large number of kilocycles" (apparently, the terior source, or by throwing over the switch, wording should have been, "when the signals are secure power through the meter for testing con- of the of a very large number of kilo- densers' continuity, etc. The same power unit frequency ËLËCTÏìÄ]) cycles"). "In this case, as I recall it, the signals .,....._._ Electrad, furnishing voltage for this use supplies voltage Inc.. were in the 1,300 kc. band. for battery sets, and "pre- heater" voltage, sock- 175 Variek St., "The Jury, in other words, found that Cohen Now York, N. Y. ets for which are also provided. Two oscillators Please send raw 1935 Re- are used with the work. Note also, a graduated was in effect running a radio station as the . i, Catalog. ....Cheek here radio waves were passing through the air out- (sr folder on new QUIET Vol - resistor (lower right) for trial use where re- /Q 0 unte Control. sistance is unknown. J. B. McGtar. side the wires and were crossing State lines." It is possible that the new Federal Communi- OJ This is a very interesting installation, Mr. Mc- cations Commission will be a little more lenient Girt, and we feel sure that some of the members than the past Commission, in permitting exper- Address will profit by your design. imental transmissions, Please Say That You Saw It in RADIO -CRAFT 426 RADIO O R A F I t o r J A N U A R Y, I 9=° INTERNATIONAL RADIO REVIEW (CortlJuurd front µrye 409) further in the device shown at Fig. E, which i Something Nero and Exciting in P. A. Amplifiers a complete tuner. This method of tuning Equipped with a broadcast type Four Position Mixer, eliminates the usual gang condenser as tuning is High- Gain Pre -Amplifier, High- Fidelity Voltage Am- accomplished by moving the high permeability plifier and Phase Inverter, as well as a High -Powered core with respect to the inductances, thus in- -Band Power Amplifier-/ire stages -all contained ssithin Broad creasing or decreasing the effective induetanr, -. one compact chassis! Operates from 110 or 220 volts AC nt is sele.- from a 6 volt storage battery. Write for low net prices and free It claimed that this tuner has constant pamphlet "What's New in Public Address Amplifiers." tivity over the entire wnve band covered. Dif- Ideal For All Sound Truck Installations! ferent types are available for T.R.F. sets and Can be used directly with all microphones-carbon, crystal, con- -uperhets. In the latter type. a slightly dif- denser, dynamic and ribbon (velocity) types! ferently shaped section of the gang control pro- Write stating your prospects problem. Give full particulars. vides the necessary difference in oscillator tun- Our design engineer, h1r. Charles R. Shaw, will personally recom- ing. mend the hest type of sound system to employ and supply free diagrams, cost estimates, etc. Get our estimate before you bro. A PIEZO- ELECTRIC MIKE CoLVMBIASOVND SYSTEM.CO. ROCHELLE salt crystal.: have found many 135 A-LIBERTY NEW YORK CITY applications in radio and associated field_. ST. 111,0. of the numerous fields of applications. "'high promises to become quite fertile, is that of microphones. HI- FIDELITY ON SHORT Several types have been developed in recent months, but une of the must intriguing. in de- SHORT i tR Y WAVE WAVES sign. that we have ever seen was described in PRODUCTS OF Y RELIABILITY _ pa,, :t7ii tin English magazine- WlainEss Wotan. (Loch u,d i "n .1i atom that As shown in Fig. F, it consists of a large u,I. fu: leA produ, to coupled amplifiers, etc.. are all employed leliabi The list Orites once- number of individual crystals of special design, shorn are subject to a discount of 40°9 when Our. to attain the ultimate in high -fidelity. which produces not only a large output but also chased Ihn. your Jobber or favorite Mail Order House this high standard prevents resonance effects over the audible spec- 4.1,r dire. -t training .lubber and As a means of assuring v, ,1111 -et that sou are pruruptlh wl.iilird of transmission cathode ray tube monitoring trum. It is claimed that a variation of less than is employed exclusively. Not only that but 1 db. is experienced between the lower limit of Build Your Own Short Wave engineers are constantly on watch checking audibility and 10.000 cycles. The individual Receiver the ouality of transmission by actual recep- eryatals are made in a unique manner as shown It'A Shut Witte kits are the World', cashed to build: we see process in the sketch Fig. F. A bakelite frame sup- Ti.-,.. tion methods. In Fig. D this 1:,14 1, ugdee poi a- lilt diagrams. The cathode -ray ports two very thinly cut crystals which are LI vil -t.- tuf 1 nd Ilse nd 3. 4. actually being performed. rube .%11.E1..:- Irl -. I el bvi'i.- tubes can be plainly seen before Mr. Alfred varnished in the usual manner to preves cat t.] n ,.. ,..i. t .u... 11 hie patent:. A. Barber, sound engineer, who is on the alert absorption of water. The sound is impinged en for any visible indication of lister ' , in the edge of the crystal units to reduce resnn- addition to checking the audible duality with ance effects to a minimum. a special receiver amplifier. A special monitor board, being operated by Edward Rhoad, staff engineer, is employed fur holding the volume from the studio art a A HIGH -FREQUENCY CUPROUS constant level. OXIDE RECTIFIER cathode - Another control panel, in which the AI.R' cuprous oxide cryst l whic h ha s .: ray tube is mounted (projecting horizontally). -, olieiont lx low internal capacity to pernit is employed separately for phonograph rendi- i, to rectify efficiently on frequeneiex as high i,-

as shown in Fig. E. There are 4 phono- e tion 1 500 ke. (or over the entire broadcast band graph turntables-2 on either side of the con- has just been introduced under the trade name o'' trol panel. All employ crystal -type pickups Sirutor. This new device was described in only. It is frum this point that the beautiful bate issue of RAFA, a German publication. The originate. (Note also S METER TRANSCEIVER broadcasts heard daily device is about 1r^í, ins. long by 5'16 -in. in di,,- KITS the crystal microphone over the panel.) neter and will carry a current of .25 ma. cnn-

.1., of a u. . _ Phonograph records, it should be 1 nder- tinueusly, without any ill effects. These metal Land to favor in European ,.. 51,;e ,oundrlrls of stood. suffer from various deficiencies, rectifiers are finding much broadcast these record programs with high sets. where they are used for replacing died, quality an instrument was devised as a means tubes. A.V.C. controls, and plate current e - of overcoming their inherent defects. A sam- nomizers where the action is similar to class Ft 519.511. t'19.25. ple of the visible indication of the quality nm phi flout ion. of the voice amplifier voice impulses can be seen from the screen of the enthode ray tube BIG NEW 1935 CATALOG mounted in this panel. The unit which performs this is shown in NEW SHORT -WAVE LINK a view in Fig. F. This particular n q1:,., close -up irr kit..,, supply !honed. Senil n to avoid panel controls the recording, and is so de- TO BYRD signed is ntnde fur c,mnpn-nsat- that provision (Cwt t inurd from paye 399) INSULINE CORP. of AMERICA ing any deficiencies in phonograph records 23- 25Park Place, Dept. C -15, New York, N. Y. only. eral stages of vacuum tube amplification, Then However, it is interesting to note that they go over a telephone circuit approximately original broadcasts fturn the studio retuaire seventy miles long to New York. The voice currents are passed through the RCA control center RADIOS no loading or tone controls (frequency e - MEN WANTED -SELL 'sensation) of any kind. The whole system, at 24 Broad Street, New York. and then routed SPARE TIME -BIG PROFITS from microphones to antenna, is so well de- through the distribution switchboard to the CBS headquarters and network control switchboard ili, 1 signed in the frequency range, so wide and etcult inc.' :tonne generally no compensation is necessary. Thus at 455 Madison Avenue, New York City. Here quality stitch tail' radio fiat, that the listener hears a true rendition of the the engineers re -route the voice from Little craulzat Iat. men stilts a original program. America over the telephone circuits reaching out .tute t other could ever like fingers across the country, as they carry II Our .pare tane .. . As a matter of fact nothing was overlooked the voice curents to the various broadcasting áhut shim still cell .. . in the design of this station. Many of the stations of the Columbia Network. One outgoing year old ('1,11.1 eon ar- testing devices are unique, such as the tuning wire circuit from 485 Madison Avenue carries 1... -talont ott 1117 823690 sic shown in fork mounted on a sound chamber the Little America program twenty -five miles r ,- u.I:. e 0e London hut ... quite Fig. G. This particular tuning fork has a iii» O. :1 a, ... easy ai any local and from .New York to the powerful WABC trans- tal . frequency period of 250 cycles. and when mitter located at Wayne, New Jersey. In the x . 5 tube super at E11ís o tt' 116 1 lode all -Its -t tapped with a hammer a pure tone is heard ieleellrltt to 12 tube odio, I cabinets or P: event that the programs are to be broadcast to tt1 t;t' sound box. The tmb tflout. ]Ir line a complete. 2 cult alt cell through one open end of the foreign countries, via short waves, then the wire hatter land 32 wIL quo in ,.A,''r.' till. w "-iv crystal microphone on the left of this phono- circuit to Wayne is o connected to the Co- °Ar' fru ate .new clue lone,and all of a quxbU al _ on to soli and .. make friend +. graph picks up this tone and passes it lumbia short-wave transmitter (located at WaU'ne e man's lined Three t. loo e for ira I. the various amplifiers. where it is conducted also). tal u v a, bllie mede If reg tar lined on right. through one of the laboratories making some second short circuit is the direct one bra it r Fir selli bes ..the ('esular lines winch The -wave plies, are are lut waive 1'ar leant expert. tests. This general procedure. over the entire from Little America, and with good radio e. a err ,vt. this the Riverhead station has >I `ori''11 n0 flues illo -t rated literature and prlre audio spectrum, is performed tiaily; weather conditions Su'll tiud hot11. silts talay. "check -up on the equipment is made so as picked up the Little America, programs over MATHESONx BELL 10.000 miles of space, a severe test for the 308-110 W. Randolph St.. Chicago to insure absolute maximum efficiency. Please Say That You Suie It in RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935

in watt phone -transmitter at Little Americ.,. .- third short-wave "stand -hy" link from Little America is that running northward to San Francisco. from which point the program can 6 -TUBE ALL -WAVE SET LATEST TECHNICAL I. transmitted to New York over a leased tele- I( ,,1111.4.11 FPO,' npr fiat) phone wire circuit. or else by short wares. The .superior that no question ans to the superiority short emergency extends fourth -wave circuit of this set remained. The controlled regenera- northward from Little America to Honolulu; tion action, which enables the listener to bring INFORMATION.... the program when picked up at Honolulu is re- a receiver up to its maximum point of effi- transmitted on short waves to San Francisco, ciency, was the attributable factor such .vhonee the voice can travel by wire or short- for remarkable performance. -rive circuit to New York. Let us examine the circuit. One 58 tube as YOURS One of the most interesting angles of the regenerative T.R.F., one 58 tube as buffer, one .hart -wave conversation carried on between Ad- 5s tube as regenerative detector, one 56 tube as miral Byrd and his mother a few weeks ago was FOR first A.F.. one 2A5 tube as output A.F.. and e telephone circuit set -up arranged between one 80 tube as rectifier. Erich tube performs Winchester, Virginia. and New York City. : single purpose and therefore does it most effi- 'listanee of about 2I5 miles. Two leased tele- ciently. phone circuits were kept open for several weeks 1ac before conditions were considered suitable to Mechanical Features pernnit this special program to be carried out, Aside front its improved circuit characteris- and a pretty penny it cost the sponsor for the tics this receiver incorporates other notable fea- :casing of these two complete telephone circuits tures. Of primary importance is that of front to Winchester. which were kept open for test panel plug -in coils. A glance at Figs. A and It v the CBS engineers at all times. will indicate the convenient method of chang- Headphones were worn by Mrs. Byrd in her ing the coils so that the wave -band desired may Winchester home and she had a special micru- be covered. This type of construction not only ;,hone of her own. while the second microphone features complete accessibility to the coils, but -erved the purposes of the announcer. As the also keeps the coils effectively shielded. which diagram shows, a local three -stage amplifier was folds considerably in obtaining stability and 'rented at Mrs. Byrd's home, and the out -going selectivity. The coils employed are of the 6- Dices bound for Little America passed over one prong type and consist of 3 windings on each. f the telephone circuits to New York. Ampli- These are mainly the primary (enameled wind- fiers spaced at a distance of about every fifty ings, feed -hack or tickler coil (enameled stiles helped to boost the voice currents as they wound), and a silver plalyd, space -mound sec- -pert on their way. The voice of Mrs. Byrd ondary winding. These coils contribute in no 'awed through the control switchboard at CBS small way to the selectivity characteristic of the headquarters at 485 Madison Avenue. thence receiver; also to the sensitivity on short -waves town -town to the RCA control center at 21 In cause of extremely good high -frequency char- Broad Street, out over a telephone wire circuit acteristics. lo the RCA 20- kilowatt short -wave transmitter A special dual ratio (60 -1 and 8 -1) airplane ocated at Rocky Point. Thus, with the speed dial permits careful tuning, which is extremely ..f over 186.000 miles per second, the voice of for gdgood short -wave reception. Mrs. Byrd was hurled from the little town of e The power supply is so designed that prac- Now available. A convenient 104 - Winchester, Virginia. to her waiting on at tically zero hum level is encountered. A built - page Manual containing essential Little America 10.000 milees away, thanks to the in tunable hum filter, see Fig. 1, is directly magic of short waves. responsible for this. information users must have to get optimum performances from any de- The Return Circuit List of Parts vice using vacuum tubes. The return short -wave circuit from Little One Alan set of 6 -prong special front plug -in America which carried the voice of Admiral coils; Complete data on over 90 receiv- Byrd as he answered his mother's questions. is Three H.F. chokes, grid -leak style; ing tubes. Base Symbols. Recom- also very interesting. When the 25 meter One audio impedance, 625 hy.: waves carried the Admiral's voice to Buenos One Alan filter choke, 30 hy.. 1,200 ohms, mended Operating conditions, cir- Aires, they passed through the transmitter and CH39; cuit applications, amplifier classi- were relayed northward to Riverhead. Here One power transformer, 2.5 V. 7 amp., 5 V. fications. Over 150 the voice passed over a telephone circuit to the 2 amp., 700 V. center-nap; cuts and dia- ItCA control center in down -town New York. Two Electrad 50,000 ohm potentiometers (one grams. Represents months of pains- with switch/; 0 4R5 Madison Avenue (CBS Control Center?. taking research b y Sylvania's thence out over one of the telephone circuits Two I.R.C. carbon pigtail resistors. 425 ohms, toing southward to Winchester, Virginia. 1 W.: famous technical staff. Mrs. Byrd could have listened to her son's Three I.R.C. carbon pigtail resistors, 120,000 This Manual is as necessary :Dice on a regular broadcast receiver and loud- ohms, 1 W.; as speaker, picking the voice up on rr broadcast One I.R.C. carbon pigtail resistor. 5 mega.. your voltmeter. Just fill in the cou- wave from either the New York WABC station I W.: pon, attach 10c in Three I.R.C. 0.2 stamps and mail. or from a Washington station : but the head- carbon pigtail resistor. -meg., phones and private receiving circuit: from New 1 W.: York to Winchester were considered a more One I.R.C. carbon pigtail resistor. 2,500 ohms, rliable and positive way of solving the problem. 1 W.: YOURS! for 10c in STAMPS As with the transmitter telephone circuit, the One LR.C. carbon pigtail resistor. 60.000 ohms. 1 IYGRADE aeeeiving circuit also passed through the V. T. 1 W.: SYLVANIA CORPORATION Eight Cornell -Dubilier or Aerovox tubular mplifiers in the exchanges at New York, lo- Makers of Factories cated approximately fifty miles apart on the condensers. .01 -mf.: SYLVANIA TUBES ST. MARY'S. tvay from New York to Virginia, which served Tani Cornell- Dubilier or Aerovox mica pigtail PA. HYGRADE LAMPS EMPORIUM. PA. to boost the voice at regular intervals as it condensers. 220 mmf.: ELECTRONIC SALEM. MASS. raced over the 275 mile circuit. One Cornell-Dubilier or Aerovox condenser. CLIFTON. N. 1. It is interesting to note that the facilities of 3L50 mint.; the RCA receiving and transmitting stations at One Cornell -Dubilier or Aerovox condenser. Riverhead and Rocky Point, Long Island. which 150 mint.; distributed these programs through the RCA Con- One 2 -gang variable condenser with planetary trol Center at Broad Street, comprise a service drive, 145 mmf. (each section) ; available to anyone who wishes to use it on a Two Cornell -Dubilier or Aerovox electrolytic tubular condensers. 10 mf., 35 V.: regular fee basis. Admiral Byrd at Little Amer - THE SET- TESTED RADIO TUBE i,a has several code or C.W. transmitters at his One Cornell -Dubilier or Aerovox tubular con - .command but the most powerful phone transmit- denser, .5-mf.: ter is rn 1 kilowatt unit used for this and an- One Cornell -Dubilier or Aerovox electrolytic condenser. block. 8 8 nit.. 12 500 other weekly broadcast. mf.. mf.. V.. 10C- TECHNICAL MANUAL-10C Radio code messages are exchanged daily be- One antenna trimmer condenser, 45 mini. ninvinmm capacity; - tween Little America and New York and other H ygrade Sylvania Corporation. points, two -way code communications being Three 58 wafer sockets; Emporium. Pennsylvania. (B.isi on and all the time. One 56 wafer socket: carried regularly practically 1I,:re -end One 2A5 wafer socket; toe thy new Srlv.c.i.. During the special Wednesday evening Little In-e 111 nm, in .,AUp, America broadcast programs conducted over One SO wafer socket; the CBS network, the "cuing" circuit used by One dynamic speaker (2.500 ohm field,: the engineers and announcers is that taking place One "Ant." and "Grid" terminal strip; mee in the RCA 20 kw. short -wave transmitter at Three wiring terminal strips: Rocky Point, and this transmitting link with One phone jack, double- circuit; nlre:a Little America has permitted some extremely One Alan drilled and formed chassis; interesting two-way "interviews' to be carried Two Alan special coil and tube compartments: on during the program, much to the delight of One Alan special dial mechanism: the radio audience. One Alan metal cabinet with hinged cover. Plrnse Solt That Yon sawn io RADIO- CRAL'r F RADIO -CRAFT for JANUARY, 1935

2 -4:30 a.m. M.S.T. included (China) XGOA THE LISTENING POST FOR (Manila) KZRM (Japan) JOAK -1. JOAK -2, JOBG, JOCK -1, JOFK, 5011K. JOIK, JODK -1, ALL -WAVE DX -ERS JODK -2, (N.Z.) 2YA, 3YA (Australia) 4QG, (Continued jrunt. poor 411) 4RK, 2CO2BL. I also had ZL1BQ on the short frequency changes are at work. The 49 meter waves." band is now the most prominent. with excellent John A. Shanks, Russellville, Tenn., reports signals the rule. Little static remains to mar that 'LS2 is coming through WOAI very well this band. and high program value may be en- at times. I think I have enough for verification joyed from the more powerful stations limited from last light's log between 6 -7:30 P.M. C.S.T. only by channel or station interference. The 31 You fellows that think you had LS4 (Buenos meter band holds up good during the daytime Aires) on 674 kc. were wrong, as I have identi- t but fades away rapidly in the evenings. The fied this station as CMCQ (Havana, Cuba). 25 meter hand is perhaps the most erratic of LR3 (Buenos Aires) is sometimes heard through JUST THE THING FOR till sometimes producing excellent signals in the KMBC. There are two stations interfering with morning hours, or mid -afternoon and at other WBz. One is LR4 (Buenos Aires). and the times being practically dead. The 19 meter band other is a Mexican, or a Cuban. Two stations SERVICEMEN good in the early to late morning. are near 910 kc. One is LR2 (Buenos Aires) and one WHO ARE Tgenerallyhe 16 meter band is little heard from at this the on 912 kc. is a Cuban. The pro- time of the year. A few high -frequency com- grams from South America are generally a mercial, or phone stations may he logged on the much different type of music than the Cuban. FROM MISSOURI or Mexican. They use classic music, concert think that radio schools and high frequencies. The 20 meter "ham" band Maybe you orchestras. and lyric tenors a great deal." courses are not for you. Perhaps you think most active in the mid -afternoon, and South they're ALL for beginners -that they can't American "hams" can generally be heard best Evan B. Roberts, Danvers, Mass.. is getting be of any real help to a man already in Jost before dusk. an early start on the European stations as he the service game. tells us that "the Europeans are really coming I want to talk If so, you're just the fellow What the Dx'ers Say About It in. In addition to Rome on 713 ke., Milan on to. For when I say that Sprayberry's Prac- 814 kc., Turin on 1140 kc., and Radio Toulouse. tical Mechanics of Radio Service is differ- -Broadcast Band - France. on 013 kc., the following stations are ent, I mean DIFFERENT. Missoula. Mont.. says: being heard with good loudspeaker strength It contains no "fluff", fancy bindings, Ralph W. Schofield, - high pressure selling or a raft of theory "Radio is getting good. My morning's log from Stuttgart. Germany, 574 kc.; EAJ1, Barcelona, with which you're already familiar. But it does contain plenty of sound, practical help on every phase of service work -just the Radio -Craft's Foreign DX Calendar kind of up- to- the-minute advanced training every serviceman needs and at a price he For December -January can afford to pay. 6,t.atern Srnn.t,rd Time But I won't describe It here. As one D,m. 7 Fri. 1:30 -3:00 n.m. 1 Palk, 4(11f11w Prieto, Buenos Aires, Argentine LS2 man from Missouri to another, I only ask Dee. 9 Sun. 2:0(1.3:00 0-.w. 0'9ke 17(10(1w- Strasbourg, France you fo give me a chance to SHOW YOU. Dec. n or 10 2:00-3:00 a.m. 8311ke 'H1(KKlw Excelsior, Buenos Aires. Arg. LR5 Just send the coupon today. It will cost Dee. 11 Tues. :3:004:00 a.m. l O4ikc 10000w Illimmni, La Paz, Bolivia CP4 you nothing to investigate. If I don't Dee. 12 Well. 2::30 -3 :30 a.m. 1230kc .1(IWw' Nacional, Is Paz, Bolivia CPX show you", you don't spend even the Dee. 16 Sun. 5:00 -6:00 p.m. 70SOkc 38.47m RADIO NATIONS, GENEVA, SWITZ. HBP small cost asked for Sprayberry training. Dec. 21 Fri. 1:00 -3:00 a.m. 082k e 1500w Bogota. Colombia HJN And even if you do buy you must be satis- Dec. 21 Fri. 1:00 -3:00 a.m. 6079kc 49.35m Bogota, Colombia (Short Wave) fied or every cant will be refunded in Dee. 30 Sun. 9:00 -10:00 a.m. l2000kc 25.00m Moscow, U.R.R.S. (Short Wave) It strict accordance with my Money -Back Dee. 30 Sun. 9:00 -10:00 a.m. 75 20kc 3!1.87n1 Moscow, U.R.R.S. (Short Wave) RKI guarantee. Nothing could be fairer. .Ian. 10 Thurs. 1:00 -2:30 a.m. 7115kc 10000w Madrid, Spain EAJ7 .l:,n. It's your move next! lf, Weil. 12:01 -2:00 a.m. 1030ke. :0(11x. Parole. Portugal CTIGI, .lao. 2(1 Sun. 1:00-2:11) a.m. 9:59ke 1(11111w Poste Parisien, Paris, France P.P. THIS COUPON WILL HELP Jan. 22 Tues. 2:00 -3:00 a.m. 1190ko 4(1(1(11w Prieto, Buenos Aires, Argentine T.S2 YOU SAVE $3.00 , WEEKLY Sat. 12 :30-1:09 a.m. 980ke :111(1(1w Pitts., Pa. KDKA DX CLUB, Also on W8XK. Rest Foreign Broadcast Stations /F. L. SPRAYBERRY,zWB SHINGiCONI, D. C. ` December -January Sure! Tell me all about SPRAYBERRY'S PRACTICAL MECHANICS OF RADIO SERV- T. Chino-Japan .4114ra:in -NZ 3.A., C.A., P.R. Europe ICE. Also give details of your offer where- HEARD AT Manila Hawaii by I can get the new series of Sprayberry I)ark S:31 p.m. ROME, Italy Data Sheets (worth $3) at no additional 713Ár, 50kta cost. It is understood this request entails I p.m. MILAN, Italy no obligation on my part. 814ke, SOÁw I p.m. TURIN, Italy i I4Okc. 7kto Name I )ark-ì:00 p.m. LONDON REG. 877kr, .50Á,o I ):,rk-1i:30 p.m. TOULOI'SE, France Complete Address 1113kr, 80kw hark-8:00 p.m. BUENOS AIRES STUTTGART, Cer. 71Okr, 84-to, 574kr, 100Áw RC I /35 I.R2 I):rk-8:00 p.m. BUENOS AIRES LR3- :)SOkr, I!km SPRAYBERRY'S PRACTICAL I ):I rk-8:00 p.m. BUENOS AMIES Lß8- I1.50kr, ankre MECHANICS Olio SERVICE l)ark-8:00 p.m. BUENOS .tIItISS LS2 -1 I.'1Oke, 4ukw Dark-S:00 p.m. CARACAS, Venez. The lLVI'T I I I: %VS' Y l'iBC, DeOk .-, 5k-w 12:01-1:35 a.m. FRANKFURT. Ger. 1105kr, 17kw CIL t LLENGER: 12:01-2:50 a.m. KONIGSBERG, Ger. As featured in November Radio -Craft 1030kr, 60kw Noise -Free Reception with the new Frequency Converter 12:01-4:00 a.m. HONOLULU, T. H. An Exclusive Feature in this NEW All -Wave Receiver KGU. 750kr, : t .kto 1:11)-:3:30 a.m. HONOLULU, T. H. KC.1I B, l.t.:nkr, ! 1 kw HORRY, Sweden 7 y 1:45-2:00 a.m. Saturdays 11.31 kr, 101-to t1 .áÁt. 2:011-:3:111 a.m. FECAMP, France 1450Ár, 10kta 2:10-3:00 a.m. POSTE. PARISIEN 959 r. 100kw 3:00-5:00 a.m. GUATEMALA, Guat. Sun -Irregular TOW, 565kr, 10kw 3:1(1_3:30 a.m. SAN JUAN, P. R. Frequency Chk WKA(;, 1240kc, 1/0- 4:30-Dawn SENDAI, Japan CORY 01A A. '. . R'. JOHK, 770kr, 1Okto 4:30-Dawn NAGOYA, Japan III \' , (,,\, N. Z. JOCK-2, 810kr, P)kto 4:30-Dawn SAPPORO, Japan (III;I Will NCH, N. Z. JOIK, 8301.x, IOkto 4 :30-Dawn TOKYO, Japan ]Ita.l{OU1cNF:, Aust. CUSTOM BUILT TO YOUR REQUIREMENTS JOAK -1, 870kr, 10kw 3LO, 800kr, f ! 2kw Wave All 13 to 500 Meters. Fourteen Latest Type 4 :30 -Dawns MANILA, P. I. BRISBANE, Auat. Tutu, New Frequency Converter Stage. No Noise. 50kw 760kc, 21 ykm Ten Kilocycle Selectivity. Four Deng Condenser. KZR.11, 610kr, Tuenty -Pound Dynamic Speaker. Eighteen Watts 4:30-Dawn SYDNEY, Aust. Output. Chromium Plated Chassis. Modernistic Air- 'BL, 8.55kq .3Aw plane Dial pith Oxner'a Name included. 4:30 -Dawn BRISBANE, Aust. Writeler Prices end Complete Descriptive Literature 46C, 1145kc, 750kw 6:00 NANKING, China We offer a special discount on any order placed for -Daylight delivery by Christmas. XGOA, 860kc, 75Áw (NOTE: While this is by no means all of the foreign stations you may hear under good conditions, this MATTHEWS RADIO 4Flushin0, N.Y.' will serve as a guide to the most important foreign stations you will hen.- during this period. Ed.) Please Say That You Saw It in RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935 429

Spain, 795 kc.; London -Regional on 1,77 kc.; West Regional 977 kc.: Bordeaux- Lafayette, CONDENSER France on 1077 ke. All of these are being heard The from 5:30 -7 P.M. E.S.T. Toulouse, France, was for Original T OBE ANALYZER so loud I could hear it on a three-foot piece of Ideal wire for an antenna. from G to 6:30 P.M. The T1rs (Trans -Pacifies) are astonishing, as every or Replacement Greatly simplifies morning from 4:45 -5:30 P.M. I am able to tune in 15 or more. 201K. Tokyo on 830 kc. is the Radio Service: only Japanese station I have heard so far." Construction The TOBE CONDENSER AN- ALYZER instantly indicates if -Short Waves - condensers of any type -paper, sends us the HAMMARLUND mica. nil, electrolytic --of any Don H. Townsend. Fallon, Nev., rapacity from .00005 to 100 following valuable data on the Japanese short- .lid. -have low dielectric wave transmitters. "The S.W. stations of - r r.kta tce and high cur Japan who are relaying the Japanese Broad- Air -Tuned ^it leakage and will casting System's programs are JVM, Nagasaki. down or on break 10740 ice.: JVR Nagasaki, 7390 kc.: JVT 6750 ..me "open "; are and 15760 ke. in The INTERMEDIATE rating inter - ke.; JYT Kemikawa. iittently (loose schedule observed in E.S.T. is -4:00 A.M. Chil- internal con- dren's Hour, 4:25 A.M. talks in Japanese, nections) or 4:55 A.M. news in English, 5:00 A.M. news in TRANSFORMERS :acs,-;-. if they are Japanese. 5:30 A.M. variety program (talks and ef- "open' or music). A.M. time signals and news. "shorted." 7:30 iMXIMUMficiency of 7:45 A.M. sign off." (At the time of compiling superheterodyne Thousands of servicemen are now this article JVT could be heard each morning circuits depends using this new instrument. with good signal strength -Ed.) "TIEP, La niore on the I.F. Voz del Tropico, San Jose. Costa Rica operates Transformers 110 volt, 00 cycle Model on 6710 ke.. and 850 ke. The owner Eduardo than any other Only 811.-10 Net Pinto Hernandez also operates amateur station factors. T12EP on 7238 kc. These stations are both The HAMMAR- Stocked by leading parts jobbers everywhere. members of the newly -formed "Latin American -Tuned Available in 25 cycle. and 220 volt Models. Chain of Radiobrnadeasting Stations." LUND Air Send for complete description TRANSFORM- ERS have proved The Gist of the NPws their mettle in the Tobe Deutschmann Corporation Broadcast Band famous COMET CANTON, MASSACHUSETTS The following Japanese broadcast stations will "PR O" Receiver. increase power during 1935 -1936. JOAK -1, They are equally Tokyo, 870 kc., from 10 to 150 kw. JOCK. well adapted to Kumamoto, Japan, 790 ke., from 10 kw. to other high -grade circuits, or for re- Truly a Pioneer! 100 kw. JOBK -1, of Osaka, Japan, on 750 kc. will increase from 10 to 100 kw. JOSK, Kokura, placement pur- This modern all -wave receiver features every Japan, on 835 kc.. from 1 to 10 kw. These fine poses. conceivable improvement known in radio to- super -power transmitters will definitely place The coils a r e day-it is a receiver that you will be proud to own. Japan in the vanguard of the international race Litz -wound and are tuned by AIR - for super power. Beromunster. Switzerland, on DIELECTRIC, Isolantite- insulated The "MY' rescher ., the truly critical 556 kc.. has increased power from 60 to 100 kw. condensers. This feature assures peak East coast DX'ers should be able to get this I.F. selectivity and a gain of 200 per station nicely. New Newfoundland frequencies stage. They are unaffected by tem- are as follows: VOWR at St. Johns, 681 ke., perature vibration, or humidity. 500w. VOGY, at St. Johns, 845 kc., 400w. VOAS, St. Johns, 945 kc., 100w. VONF, St. Johns, 960 kc., with 5000 watts. Midget R.F. Short Waves CHOKES That popular radin station PHI. at Huizen. Holland, is now back on their winter wavelength The HAMMARLUND Mid- of 25.57m.-11730 kc. Radio ROMA 12R0 on get R.F. CHOKES are the 25.40m. -11810 kc., which has been making ex- smallest and lightest ever tensive repairs and improvements in their transmitter will be back on the air with greatly in- devised. Inexpensive, they creased power and a full Empire service using may be used wherever R.F. directional antenna array about the first of the There ú finer nll. filtering is desirable. Induc- - -- eseit-er built new year. They will transmit different pro- wá> grams daily to the various continents. RNE, tance, 2.1 mh. Five impreg- IVritr for Compete Details on this on Modern All-Wave Receiver Moscow, U. S.S.R., on 25m. -12000 ke., and RKI nated pies Isolantite on 39.57m.-7520 kc., are being well heard again core. Tinned copper leads Pioneer Sound Laboratory with their transmissions for NBC rebroadcast in ample for support. Choke 135 Liberty St., New York, N.Y. this country. At the present writing the NBC rebroadcasts RNE -RKI on Saturdays at 11:90 size: 'Fe in. X 1% in. to 12 noon E.S.T. and Sundays from 9:30 -10 A.M. E.S.T. PRADO of Rio Bamba, Eucador, have abandoned their popular Sunday afternoon HAMMARLUND MANUFACTURING CO.. ,sra1RA1 -Stop Guessing!- concerts on 19 meters until next spring when 424.438 W. 33rd St., New York. 1 Radio servire Is easy ,hen ymt knots just where the band begins to show a little life again at 1 I to look for the troubles. And. the securing of this time of day. XEBT, Mexico City, have a -Check here and attach 10e for 10 -page lbuu- / profitable fees for the makes the work I repairs I t i ug still more attractive. A eliminates habit of camping almost right on top of DJC. I mn rhmd 19:15 Short -wave Manual, llust rn Citt'('KKER most S -W of guess -work in "what Is Wrong and what to Zeesen, Germany, on 49.80 meters, although and .bsrribltig popular circuits ipant year. Willi schrmatle and picture 4Ingran.s I'harge." This trouble- loralizer. olth a really is supposed to be on 49.92 profitable repair- prieer schedule included. enables XEBT meters. A and parts lists. radio men to lm -alite any trouble In any radin. new station being heard early each morning l'hart here for PREF. insert, taon on (ludo, ! aatirkly. In the field without disman- !- right on about 6100 kc., with only Dutch being spoken and 'l'rn nsfornars. 1 tling the radio. It looks oClrlal. and permits you and typical Asiatic music, is believed to be the here l'REE General ('tstaing. easily to conrince set-owners that you are not I - ('heck for 1 guessing at either the trouble or the prlre of the new short -wave station YDA, at Bandoeng, repair job. You competitor makes good money Java. They seem to sign off at about 8 A.M. 1 Name by using a CHt'CKKERI Semi $1.00 NOW for yours, postpaid. Also. ask how you might scrum E.S.T. Senor Pompilio Sanchez states that the Weston testing equipment PItEE for answering schedule of HJ2ABA at Tunia, Colombia, on I one simple question. 6150 ke. -48.78 meters, is Tuesdays. Thursdays. FREED'S RADIO CO. and Saturdays from 6 to 9 P.M. E.S.T. Ita'-, Publishing Division R ------J 5053 Baltimore Ave. Philadelphia, Pa. Radio -Craft Awards Each month a prize of a year subscription to RADIO -CRAFT will be awarded to the DX'er who LEARN RADIO sends in the best ten foreign verifications. it'Jot, Rii=1-Aorta:, 200 Graduates Placed in the Last Three years (Verifications for stations on same continent as At the oldest, largest and best equipped privately owned be radio operating school in the East. Western Electric and DX'er will not be considered.) Award will ámmärlund RCA tube transmitters: 200 licensed graduates placed in announced in the successive issue of this publica- PRODUCTS past three years in broadcasting. shipping. pollee radio. tion. All verifications should include self -ad- u aviation. service work, etc. Course prepares for all U.S. Government Telegraph and Telephone licenses. Send for drssed envelope and return postage, to insure 40 -page catalog. Investigate. New classes every six weeks their return. Address DX Editor, RADIO- CRAFT. from Sept. 10th. Open all year around. 99 Hudson St., New York City. MASS. IIAOIO SCHOOL 1S Boylston St, BOSTON lt. l'. Trop. Tres. -EST. 11.1519---41. lt. Entwistle. Pres. One of America's leading Radio Schools Please Say That You Saw It in RADIO -CRAFT 430 RADIOCRAFT for JANUARY, 1935

tin phase) and with equal intensity. These ELEMENTS OF 4TH DIMEN- waves are converted into nerve impulses, by the inner ear, and sent along their respective nerve SION SOUND SYSTEMS fibers to their individual centers of hearing (Cb"t r,,,,d front nape -107) located within the bruin. The interpretive center then compares the pattern in each hear- ears. The amplifiers will of course. be of the ing center (with respect to phase and intensity) high -fidelity type while the speakers will operate and gauges the direction and d,ahg arc of the with performance characteristics identical to sound, basing its judgment solely upon previous those of the original sound producing devices. hearing experiences with that sound. In this Second, we have "spatial rr /olionsh;,," -which particular instance, as there is no difference in appears to he the stumbling block for perfect phase or intensity, the source of sound is local - G artificial sound. Although Dr. Harvey Fletcher ized in the median plane that is directly in (of the Bell Telephone Laboratories) succeeded front or behind the listener (Fig. IA). It in closely approaching exact spatial relationships should be borne in mind front the foregoing of the original and reproduced sounds with a illustration, that in order to naturally localize tri- dimensional system, the "last word" will not a sound, a complete circuit (acoustophysinlog- have occurred in the recreation of sound, which leal) must be completed between the source of completely fulfills the requirements for perfect sound and the interpretive center through both ears illusion. until a fourth dimension is taken into and their respective hearing centers consideration. (Fig. 2A). Before we delve into the elements of artificially recreated fourth dimensional sounds, let us The First Dimension: Distance briefly analyze our own hearing sense so that Ir a source of sound (Fig. 3A) is kept in n we can use it as a standard of comparison. horizontal plane level with the ears, but moved For, without such a "yardstick" it would he in the median plane to and from the listener. difficult for us to realize how far we actually a sensation of distance will be noted as only the are from the goal of perfection. Then again, if intensity of the sound wave. but not the phase "Since using your con- the understand how people normally react to changes. As the intensity is decreased the trol eI feel like a new natural sounds, (which, strange as it may seen. source of sound is localized at a greater distance, radio." "never continuously occur in a fourth dimensional while with a gradual increase of intensity per- world) the formed better in my life," we can easily grasp the elementary source of sound appears to be canting closer to spatial principles and conditions involved in our the listener. This same effect can be created writes another. everyday hearing, and possibly find it a relatively artificially with the use of a simple electrical and so it goes ... thou- The mine simple matter to duplicate in an artificial sys- circuit (Fig. 3B) which is analogous to present sands of old, worn nut, tem. sound systems. RÁDÌÓÑM By keeping the sound source at tired radios are being re- a fixed distance from Our Directional Hearing Sense the microphone, and re- juvenated by alert serv- gulating the attenuator. a listener located in Our first bit investigation, icemen with a small stock of therefore. in- another room will be unable to tell whether the volves itself of with the mechanism of hearing - source of sound is moved or the attenuator set- CEXTRALAB re- particularly the spatial localization of stationary ting changed. placement units. and moving sound sources. With this arrangement it will be noted that if When we normally localize a natural source the sound source is moved in any direct inn, up .,y Ra.. .fin,,, .Ifw The Sturdy of sound in space we subconsciously or down, from side ...0 Me w"oMefv make three to side, or to and front the ..r4W-hy.,e.- Fixed measurements; first, we microphone, the RESISTOR estimate its horizontal listener in another ream will angular displacement (Fig. IA) which indicates interpret all directional movements as either di- how much to one side the sound is coming from: rectly approaching or receding from hint. NO then we estimate its vertical angular displace- sensation of horizontal an gn la r displacement or nient (Fig. 113) which tells us whether the .sound Vert iral antut,,r displacement of the sound source is coming from above or below; and finally we will be experienced. This single dimension illu- judge its distance (Fig. 1C). When the sound sion is representative of the .working limitations source is moving, we make an additional fourth of our present radio bruadea sting, sound picture, RADI OH MS-RESISTORS measurement in order to approximate its di- telephone and public address systems. v , rection and speed of motion. The accuracy GLOBE UNION MFG. CO. with which we localize a sound depends upon The Second Dimension: number of factors, among which are; fa- Angular Displacement MILWAUKEE ,iliarity with the sound, tilt of the head, and in Horizontal h ll ity to see the source of sound. The inip"r- Plane :nt part played by these secondary hearing - If the sound source used in Fig. 2 is dis- :,Ids account in a large measure for the manner placed 30 degrees to the right (Fig. 2B), but I1 which the brain deceives the interpretive kept in a horizontal plane level with both ears, , wring centers by supplying the missing di- two different acoustophysioiogic circuits are set ',tive properties of' sound. Because we be- up front the sound source to the interpretive Ine accustomed to this deception, we frequently hearing center. In this instance. the axis ( Rx t 'u lain unaware of the handicaps characteristic of the sound wave reaching the right ear is single dimensional sound systems. UNIVERSAL reproducing much shorter than (Ls i the axis of sound I hr' directive "hearing" aid offered by the eyes reaching the left ear. The result is that th- easily be checked the next time you view ALL -WAVE . "talkie." Note how easily you recognize un- 4 usual sounds-and locate them, because you N. Fig. the apparent source of sound. Now close your Detail illustrations of 4th dimension sound. ANTENNA SYSTEMS eyes and you will be surprised to find how difficult it becomes 2 00 ONM 20OOpeaS ro 1000 ONM t000 to localize the shot of pistol. MICaODIpNE 1000ONMS.TYANS r-l>O 06MAe01e 'CAVA) the clicking of a typewriter, the approach of an (ESC.) ,J 1 anq Model 34 * automobile or the movement of an actor front i one side of the screen to the other. In fart, List unless the theatre is equipped with a fourth sound system, it will be impossible Price t..limensional localize any sound whatsoever that would vnrre. pond to natural localization as tvnuld occur if you were at the actual scene while the $6.95 picture was taken. ACUUSTIM EOUIVALEN1 - I 00 ONV O EAD A- T VAC) Thousands of TOILE antenna kits are now How We Judge Direction 135° in use. Here's why! A casual study of Fig. 2 shows the elements V Can he used with ordinary flat tops or involved in normal binaural hearing of a single ` f doublet antennas. stationary sound source in free space. (Fir V Receiver coupling transformer has two simplicity sake, we will limit our discussion to - - wave band toggle switches. direct sound waves and not the reflected or AS' V Tremendous noise reduction. reverberant waves because the former are far -B more important in the localization of sound V Contains everything required for a com- sources than the latter. plete antenna system. Any system which can recreate direct sound waves in their natural Model 35, a basic kit of 2 couplers and 50 spatial relations will automatically reproduce ft. of twisted pair lead -in, at only $4.96 list. reflected and reverberant waves sold by leading parts jobbers everywhere sound identical :.t ry,',,I,r trod. with those of the original rendition if the acous- -C O tics of both the localities involved are identical.) If the source of sound is directly in front Tobe Deutschmann Corporation of the listener, the axü of the sound waves Canton, Massachusetts (RX and LX Fig. 2) are of equal length. Sound I1I11--- will therefore reach both ears at the same time Please Say That You Sato It in RADIO-CRAFT RAD10-CRAFT for JANUARY, 1935 431 WATCH THE "LEADERS" right and left center of hearing present entirvd; different patterns to the interpretive cents FOLLOW LYNCH which therefrom approximates the horizont,, MAKE MORE CALLS For more than two years Arthur H. Lynch angular displacement. The listener Usual l:. has been can nhaslzing the fact that turns his head in the estimated direction un, "No Radio Can Be Better the differences of phase and intensity are tslu.'- «d BIGGER PROFITS ized in both cars and thereby assumes that nl Than Its Aerial" sound anurce is directly in lino with his nos-. If the source of sound is sighted. definite local- "ar1A T ization takes place. if not seen the direction of iva"7lewcr- HI -FI the sound source is imagined. As two separate patterns must be formed by RADE MARK REGISTERED both hearing centers, it becomes evident that a (High- Fidelity) special pickup and reproducing system must be employed (Mg. 4A) so that the phase and in- Ea RITE ANTENNA SYSTEMS tensity differences, as would normally be picked are as superior to all other antenna ardents as up by both ears, be preserved. The best IWO- the present high-fidelity radio receivers are oe,lure is to separate both microphones wü h superior to the malsy. squealing sets of years aga. The "Lades. +" are Just beginning to some object accoustically equivalent to the heal. realize they pare been playing a gatito of By adjusting both attenuators to match the Sen- Rip liar Winkle. .sitivity of the ears true stereophonic repreRlw- ASK YOUR DEALER tion will result. A listener sitting in another TESTER to demonstrate a LYNCH Antenna- roost will be able to follow a sound source or mite us for free literature. moved from side to side. Some ambiguity will Then COMPARE! result because of the listener's inability to move N? 720 ARTHUR H. LYNCH, INC. his head towards the sound image for purposes of confirmation. Thus, when the sound souse 227 N. Y. Fulton St., New York, is at a 45' angle to the right it might appear PIONEER OF NOISE- REDUCINGAERIALS to be at a 135" angle. (Fig. 48). By Hiving either attenuatur and keeping the sound source stationary. the apparent location of the sound image can be changed. A perfect illusion. how- Presenting the ever. will not he creates! unless an appropriate phase lag is introduced into the circuit having new improved JIFFY 3 the greatest attenuation. Experiments conducted have shown that considerable deviation may be SHORT WAVE SET mule from ideal phase and intensity patterns. without seriously affecting the accuracy of the sound image localization. When two different sound sources are used (bell and telephone receiver). the listener will be amazed at the ease with which he can follow both sources even though they be moved from Side to side or to and from the microphone. Not until one experiences stereophonic reprodu'- t ion can he begin to realize how limited and unnatural are our ordinary systems of artificial sound reproduction. Ilrorld -Il t.l, Earphone Reception! If the microphones are connected either in il... .et that ran be a l series or (Figs. 4C and 4D) the stereo- littler uiring -the `embiew parallel Iybeginner;. Tite set etmdet phonic properties of the circuit will be lost as sud has bakellte bare. Tile both ears receive identical sound patterns, and 1,.I. I..n regeneration saki detect ion thereby Complete band- d tuning and low current shunt the interpretive center out of the drain is assured. .mouth, dear and quiet opera acousto- physiologic circuit. HERE is the tester that every ser- don at all tIne. s KIT, =dingInalading 4 short wave viceman needs for properly servic- $6.25 ing radio receivers. new Wired. &:.7'.: tulles extra $1.t.° The Third Dimension: The Readrite We welcome ìnguiries and comparison. No. 720 Tester enables you to make LEOTONE RADIO COMPANY Angular Displacement in a Vertical more calls per day at less cost per call 63 Dey St. New York, N.Y. Plane -and make bigger profits because of Strange as it may seem. n listener with his its speed, its accuracy and its depend- oyes closed, and without tilting his head will ability. WHEN CHOOSING be unable to localize a SIM eve of sound t retina The new No. 720 unit operates taster front above or below the level of his ears. 1e This physiologic handieap plays an important part more efficiently and with less ma- A RADIO SCHOOL in the design of a fourth dimensional sound nipulation. It tests all resistances, con- In>t 111.1 ii... tat ton eataltitdp system, and is mousei by the location of both our tinuities, voltages, current and capac- raire. is an Iin; it ut ion re,, . ears in a horizontal plane. If we had two ad- ities from the set socket by the reliable Mudo as important (moor ditional ears in a vertical plane, we could ac- in the radio Indust n. point -to -point method. And it is built Whether elements, y radio trin- curately gauge the vortical angular displacement to withstand severe field service. rhde; or a,hattre,I swi;,, r,. of a sound image by using the same process as nand application; or practical Two highly developed Vane -type AC radio engineering. RCA Ind!. used in judging horizontal angular displacements. tuft, la prepared to give you We can however localize a sound coming from and DC meters are incorporated into the Instruct ion you need. alone or below ua by simply lilting our head this new tester. They are simple in de- RESIDENT SCHOOLS NEW YORK AND CHICAGO sound xiah nie, lent standard equipment until the attains maximum intensity. sign and dependably accurate. The is EXTENSION COURSES FOR HOME STUDY Here again localization hastened by sighting DC scales are 15, 150, 300 and 600 volts, mnder nmrenlrm "no obligation" plan the source of sound. Inasmuch as the eyes play 15 -150 milliamperes. AC scales 10, 25, v lu It.1rited Catalog Request. a secondary part in sound localization. it would 150 and 750 volts. appear that sightless people, as well as the R. C. A. INSTITUTES,rV Inc. RT35 audience of our (mirth d' nsional sound system. Your Jobber Can Supply You ... 7S Variait St., New York- -1161 Nerdiandise Mat, Chicago would be seriously handicapped. Such is not the i case however, for our inner ear contains an With the Readrite No. 720 Tester at organ of balance (semi -circular canals) which Dealer's net price of only $15.011. Write play no limit purl in hearing. but afford an direct for literature to g Socket Operated accurate measurement of the tilt of the head. READRITE METER WORKS It therefore becomes evident. that in order to 136 College Ave. Bluffton, Ohio 4. `N1 M11: 11 CI I achieve perfect illusion in a fourth dimensional MILES anCKaT MIKF, nxi_ Y.n.l.) sound system we must project sound from above a....iaoad to operata, 11nnrn t I tlhru whou and below the level of our ears by using a set of MAIL COUPON FOR CATALOG Aulaina vithout ie overhead and sub -level speakers. sod in Kit Form enmrl.eewiiÌ di:.arato mW ioenmri..n. The demonstration staged by the Bell Tele- r Ì.i.1. x 1 1 f21.7f MILES REPIIÓDUCËa CO.. INC., phone Laboratories was lacking in this respect Readrite Meter Works 1124 West 14th St.. Dept.: NC1. Now was picked 136 College Avenue. Bluffton, Ohio. York. N. Y. because all sound up from one and projected in a series horizontal plane of Seul me Ian ,m Remit Ile No. T_I'l't'.ler ail (.a_. planes sound most suitable for adequate dis- proving Iteadring lender.hip. NOW READY tribution, but without regard to the vertical The 1935 Profit Guide angular displacement of the original sound lui Pages Full of ylarvnlon. Nance A complete titian( public sources. While it is true that the reproduced amplifiers and eguhnnent- version of the airplane roar seemed to come Adire lrh.-Meaker- from overhead. this false localization was sensed iinrunittarnart r rem s taos.. only by individuals whose past experiences as- City State .u1 i r Your Fnr, ("' , 7 sociated airplane roars with elevated positions. BALTIMORE RADIO CORPORATION 721C Broadway New York. N.Y. Please Say That Yoa Saw It id RAnlo- CRAFT 432 RADIO -CRAFT for JANUARY, 1935

One cannot doubt the fact that illusion of some ,tther sound like the overhead sawing of wood or singing while swinging could not have been produced by this system. There's plenty of A block diagram for a system used to direc- tively project a sound depending upon the position of the original sound source, is shown in Fig. A. The four microphones pick up the original sound with a proportionate intensity Servicing depending upon its nearness to anyone or all HIGH FREQUENCY units. By using four separate channels. the By -Pass pick -up pattern is maintained clear through the Condensers amplification to the recreation and projection. OTHER Sprague dureL,r Ae,i; avers f r Material .. ilin . e'Ñ1Wove 'iS¡i,rIlent The Fourth Dimension: Time and Ifs hfen ut Measurement of the Rate of Change n! sou have 1 , e, in the Jest the 1934 Manual ti ëóñ; I" m,mrrfMe.. i ~ of a Moving Sound Source moire tr`ÁL mee The factors which Radio Service Men and others en- wfr drrmt. Tb,e.ei ;ii» euh.r, determine the localization wu rdrn e CAN of a moving sound source involve gaged in various branches of radio know end eHecOeetues rn the all of the re arunnLsafetyr tn. eShort perceptive and interpretive facilities used for the the importance of the GERNSBACK YOU JUST CAN'T IIREAR THEM DOWN. location of sound in any one of the three planes Manuals, and how much they depend on TESTS AT HEAVY CURRENT AND THE: of space; as them for reliable information. IsNIJOU.S IIF.tT HAVE SHOWN NO Fvl. well as the coordination of the Whether CHES. QUALITY AT A PRICE RECAUSE OF rate of change with which for public address work, receiver dia- NEa_, _I.II'ROyF.O CONSTRUCTION. OIL the various patterns of the right and left hearing centers are pre- grams or tube information, the material sented to the interpretive center. needed is certain to be found in one of eeaetlae met/ ts`.-aÌ`rn...denser. onh1nler usirufoetird It thus becomes evident, in the volumes of the OFFICIAL RADIO Ie u,nre rethrss. Metal nrrexH-nun-indoeric,- that order for us r power m re l with to recreate the illusion of fourth dimensional SERVICE MANUAL. ¡::nyáe -alïsr-i mtniau V. con- tusions D. é.InówC. retina. Guaranteed .edm nllv sound we must use a system which will present a. hy lending r en Contents of the 1934 Tlllí'%l'lIyI EIeI TODAY/ ld to both ears a series of changing patterns identical in every respect to the sound patterns we Manual in Brief would hear if we were listening to the moving Diagrams and service notes, more complete CatCat. D. C. Working sound source directly. In other words, the sys- than ever before in any manual. Voltage read- No. Cap. Vol. Olam. Length List Net tem should be capable of picking up amplifying ings for practically all sets, as an aid in SW-22 .002 1500 9 16" by 1 9 16" 5.45 5.27 and projecting all sources of moving sound in checking tubes and wiring. All values of SW-25 .005 1500 5Al" by 113'16" .45 .27 exact accordance with their original speed, mo- I.F. transformers used in auperheterodynea, 11 SW II .01 1500 11/16" by 1 13,16" .70 .42 tion and with the manufacturers' own suggestions as SW-IS .051000 7/8" by 2 1/4" .80 .48 direction. r to correct balancing. A complete compilation T SW -1 0.1 1000 7/9" by 2 1/4" .90 .54 Pant experiences have shown that the complete recreation of radio tube data, covering both old and new of moving and multi -sound sources, in types. A complete list of American broa.least their exact spatial Write our complete Condenser Catalog in- relationship and aesthetic stations with their frequencies in kilocycles; cluding famous Sprague Transmitting Condensers aspects, is possible only by employing a special extremely useful in calibrating test oscillators sound system and using a new technique in its and receivers. Free question and answer service. SPRAGUE PRODUCTS CO. installation and operation. Such a system will No theory; only service information in uickly accessible form. A handy, easily -con- be presented in next month's issue of RADIO - North Adams, Mass. sulted master index making it easy to find CRAFT together with detailed information for the almost anything pertaining to service prob- instruction, installation and operation of this lems, instantly. This index includes all the r ystem. diagrams published in all the previous In the meantime, the authors will be pleased to GERNSBACK manuals, as well as the 1934 diagrams. receive comments and answer questions relative A big convenience and time saver. to the fundamentals of fourth dimensional sound. 400 PAGES for Short Wave Over 2,000 Illustrations IMPROVED 2 -TUBE S. -W. 9 x 12 Inches BOOSTER S. Model W. 429 (Coatiiled from poor 110) Flexible Looseleaf Leaiberefte Corer Reproducer Receiver selectivity is obviously No need to aria :ending us your of paramount ORDERS order -the 1934 MANUAL. like its importance in successful short -reeve reception. predecessors. is a necessity in your R.F. boosters not only provide for attainment of TODAY business. We strongly advise you to order your copy today. an ultimate degree of selectivity but also furnish a successful method for signal and noise rejec- tion. Both of these functions are essential for dependable transoceanic reception and both of these conditions are best accomplished by increasing the selectivity of your present receiver. for the reasons outlined below: 1. Increased Selectivity Minimizes Static. 1 9 34 2. Increased Selectivity Avoids Interference.

With the constantly : increasing number of N+rticiël ' foreign short -wave stations, owners of both elab- Radio orate and simple receivers are becoming aware Service of the inferior selectivity of their sets. The ac- Manúal tive 19, 25, 30, and 49 meter bands are particularly notorious for their interference. The .'__lAmplHe Directory only effective remedy for this form of interfer- . G. \V. TWOMEY. U. S. Veteran's ence is increased selectivity and is best accom- DR.Hospital, Minneapolis. Minn., oper- plished by adding at least one (or more) tuned ating a most complete short wave receiv- R.F. stages to your present receiver. ing gives his report nation, on the S. W. The duplex drawer coil unit employed in the f29 after a most thorough and exhaustive booster. test. diagram of which is shown in Fig. 1, is essentially composed of two precision space- A copy of this complete report will be wound coils sent to you upon request and you will fully shielded from each other, but GERNSBACK PUBLICATIONS, INC. contained within one catacomb drawer and so find it not only interesting but instructive 99 Hudson St. New -write for a copy today. arranged that the entire unit slides into its re- York, N. Y. The Model S. W. 429 is designed and ceptacle through the front panel. in a manner manufactured especially for use in short similar to changing drawers of a miniature GERNSBACK PUBLICATIONS. Inc. wave reception and is extremely efficient. desk. 99 Hudson Street, New York, N. Y. I- :nln.ed tlnd The sensitivity in the voice frequencies The cadmium -plated steel receptacle, into which my remittance of $3.50 for m111.14 s.nd makes capable Potage Prepaid. One Copy of the 1934 it of bringing in weak sig- the drawer coil slides, is equipped with three CIAL OFFI- nals which would be practically lost when RA l)I t) SERVICE MANUAL. (Send rem Illam, specially designed double- spring, butt -wiping by cheek or money order: or register letter If It c using any ordinary speaker. tnlns rash, - and self- cleaning contacts which are in no small eurreney or unused l'. S. Postage stamp. .I Also write for our catalog -a speaker for etery purpose. measure responsible for the unusual performance and permanent operation of this bawl- Name \\ RIGHT -DECOSTER, Inc. changing system. Each contact is composed of two springs; one made of phosphor bronze, for Address 2251 University Ave., St. Paul, Minn. connection and the other made of tempered high Export Dept. M. Simons & Son Company carbon steel (similar to clock springs), for ten- 25 Warren Street, New York sion. The tension spring absorbs all bending Car _ State It(' -13:, Cable Address: Simontrice, New York. 1 stress. Please Sal/ That You Saw It in RADIO-CRAFT RADIO -CRAFT for JANUARY, 1935

ed in the diagram as C5 is a tiny trimmer type BUILD THIS NOVEL I -TUBE condenser mounted directly in the end of the coil form and connected across the entire grid The New NATIONAL ALL -WAVE SET winding. This condenser is adjusted by means ( Continued front page 405) of a screw sticking out of the end of the coil. It acts as a fixed loading condenser, while con- 1935 CATALOGUE B are the filament terminals, G is the cathode denser Cl, which is connected across only a por- of the detector portion. This has a suppressor - tion of the entire secondary inductance, has a grid connected to it within the tube. C is the relatively slight tuning effect, and therefore the Lists a Variety of plate of the detector, while D is the screen -grid entire dial movement represents only a limited of the detector. E is the cathode of the rectifier frequency range; hence the "bandspread" action. portion and F is the plate of the rectifier. The Of course, the particular section of any band to New Parts and Receivers cap of the tube (H) is connected to the control- be covered depends on the coil used and the grid of the detector. It is suggested that the settings of the individual C5 condensers. grid circuits be wired in first, then plates, for SHORT -WAVE Set cathodes, bypass condensers, and filter condensers, and finally the filament circuit. A Regeneration Control flexible wire is soldered to the antenna trimmer Regeneration is controlled by the 1 megohm Construction- for the aerial connection. This set dors not re- variable resistor, Rl, which is connected directly quire a Around ronnretion and in fact. none in series with the "B+" 22t_ volt lead to the should be used. If A.C. hum is noticeable. use audio transformer primary. This is bypassed an additional dual 8 electrolytic condenser, con- by a .5 -mf. condenser which effectively eliminates necting both sections in parallel so as to obtain any tendency of the control to be noisy. The 16 more microfarads at point (10). regenerative action is smooth and quiet, and phone stations can be brought in just at the List of Parts critical point of oscillation. The secondary of the transformer is shunted One Hammarlund variable condenser, .00014 by a 1 megohm resistor, R4, merely for the pur- mf., type MC- 140 -M. (3) ; pose of eliminating fringe howl. One Hammarlund antenna trimmer condenser. On the left side of the cabinet is a double 3 to 35 mmf., (1) : binding-post strip for aerial and ground connec- One Aerovox mica condenser. .0001 ml, type tions. It has been found in actual practice that 1460, (5); most any sort of an antenna will bring in sig- One Aerovox mica condenser, .0005 mf., type nals. Fifteen feet of insulated flexible wire 1460, (7) draped over the roof of a car worked very well One Aerovox cartridge condenser, .01 mf., in some road tests and brought in program, type 484 -N. (14) : from numerous foreign short -wave stations. A One Aerovox double cardboard con- section fire hydra -t and an iron railing have all been tainer electrolytic condenser. 8 mf. per section, used successfully as "ground" connections. type PB -2. (12. 13) One Electra(' potentiometer, 75,000 ohms, type RI- 202 -P, (6) with Sw., (16) List of Parts One power line cord, 350 ohms, (15) ; One Two- winding 5 -prong band -spread coils as One set 4 of five -prong plug -in coils, covering described below, Ll ; 10 to 550 meters. (2) One 2.2 mh. R.F. choke coil, 1,2: One I.R.C. metallized resistor, 1 meg., One 140 mmf. midget variable, Cl ; (4) One .00025 mf. mica grid condenser, C2: One I.R.C. metallized resistor, 10,000 ohms. One .0005 mf. mica bypass condenser, C3; 1 W.. (11) One .5 -mf. paper bypass condenser, C4; One twin jack. (9. 10) : One trimmer condenser built into coils, C5: One seven -prong (large) wafer -type socket One Two -plate 5 mmf. antenna trimmer, C6; (8): One 1.000.000 ohm potentiometer. Rl; One Hammarlund Isolantite socket. 4 prongs. One 8 ohm wire -wound resistor, R2; Send for YOUR COPY Today! (2); One 10 megohm grid leak, R3: One 12A7 tube, (8); One 1 megohm grid leak, R4: The new NATIONAL Company One roll of Corwico braidite solid core honk -up One single open circuit phone jack with insu- wire; lating washers, J; Catalogue No. 240 is ready. Many One metal box, tiv, x 5% x 3% ins. high: Two Type 30 tubes, V1, V2: screen new items One -grid clip; three knobs; One 3t_, -to -1 ratio uncased audio transformer. are illustrated and des- One headphone. T; cribed, including the new HRO Ama- Note: Numbers in parentheses refer to cor- One Steel cabinet as specified: responding numbers indcoted on the diagram One 412 volt "C" battery, Burgess No. 2370; teur Receiver, new TR 5 -Meter and layout view (Figs. 1 e,ol 2). One 45 volt "B" battery, Burgess No. 5308; Three -inch vernier dial for condensers Cl, Transceiver, new Cathode Ray Oscil- knobs for RI and CG. double binding -pest strip, loscope, new Transmitting Conden- 5 -prong socket for plug -in coil Ll, and incidental hardware and mounting screws. cers, new P\V Precision Condenser A SHORT -WAVE 2 -TUBE and Micrometer Dial Unit, lnany PORTABLE Coil Data Table Wave Band Secondary Primary Trimmer other new components for Short (Continued from page 410) (meters) No. of Tap from No. of Capacity \ \rave Receiver construction ; and the a comfortable carrying handle. Its feature is turns bottom Turns. (mmf.) the use of special hand -spread coils, which make 19 4t P.í 4% 80 latest catalogue information on the station finding a comparatively simple matter, 25 4tí 1!í 4% 180 and also permit the use of the receiver as a com- 31 6 180 well known NATIONAL S\\- -3, plete amateur station monitor. 49 111_. 4% 6 180 F13 -7A, FB-X A, PSK I'reselector, Exactly half of the space inside the cabinet Fixed variable condenser. Values shown are is occupied by the receiver components proper maximum. All secondary coils are wound with and other S\V Receivers and Con- and the other half by the batteries. No. 24 bare wire spaced to a winding length of verters; and Power Units, Dials, The main tuning condenser Cl. of 140 mmf. 1tá ins. Ticklers are close wound with No. 28 capacity, is controlled by a small vernier dial. or 30 S.C.C. wire. Condensers, Transformers, Chokes, In the lower left -hand corner of the end of the cabinet is the antenna trimmer condenser, C6: etc., for high frequency work. in the lower right -hand corner the combined regeneration control and filament switch. R1 -SW. The 2 -tube portable in use. Between the two lower knobs is a short single- I7 I S F. CODUPON I1ELO % circuit earphone jack. J. This is carefully insu - lateo from the cabinet. as the latter forms the grounded "A-i -" side of the circuit. NATIONAL CO.. Inc.. 61 Sherman Street, Malden, Mis. The band -spread coils, which are described in an accompanying illustration, are of the double Gentlemen: Please send me your new winding type. The small winding at catalogue No. 240. I enclose fic to cover postage the bottom and mailing. of the form serves as the tickler, and is connected in series with the plate circuit of the Name detector tube, VI. The R.F. choke coil, L2, of 2.2 mh. inductance, keeps the R.F. energy Address out of the primary of the audio transformer. City It will be observed that the main tuning condenser CI is connected across only a portion of State the entire grid or secondary winding. The tap is about a quarter of the way up from the grounded end. The variable condenser represent- RC-I-a; Please Say That You Saw It in RADIO -CRAFT R I R F T 434 A D O C A J A N U A R Y 1 9 3 5 TO BUILDI' -Announcing- A "HOW A MAGAZINE SERVICE MAN'S ALL - A NEW DEAL WAVE OSCILLATOR WHICH NEEDS in getting acquainted with (Cot, %blood from Pape 416) NO INTRODUCTION grid and, as far as R.F. is concerned. these elements are at ground potential. This shields the SPEED plate from the frequency -controlling elements of TO SHORT -WAVE FANS- the tube and effectively isolates the output RADIO TUBES Therefore, a variation of output load has very Pioneers In tube development .Ince 1921. little effect on the oscillator. We make this get- aequahmed. money-awing Ltftr to The tuning condenser used has a capacity of servicemen dealers and techniciatls for a period of 365 mmf. Any condenser such as is used in the of tuamnet 60 day. 0111y. with the idea giving old average receiver can be used. This condenser and new the same opportunity to save otonev. We ha SHORT Mere titis announcement to be of outstanding hnlon- must be insulated from. the chaaxis, as is shown tauce ... and worthy of immediate action. in the print. Nothing is returned to the chassis SPF,KD RADIO CORPORATION Is up -to- the -tnino except bypass condensers. This has been done achievements. Listed below are inn in latest tube -navi to prevent short -circuits on the puss-er line when buttent 1 tn.y types of tubes for Tort AILE GUARANTEED FOR A an A.C.-D.C. receiver is being tested. WAVE we. A1,1.I, TI'ItES PERIOD OF NIX MONTHS. The switch used is a 3 -pule, 5- position as- Here I. the Tube List: sembly. One pole is used as a shorting switch Net Net Net to short the preceding coils, that is, the lower - Trite Prim Type Price Type l 'rite frequency coils. This is done to prevent the nat- 45 S .33 4s S .65 CRAFT 01\ S .27 ural period resonances of the unused coils from 210 1.13 47 .59 11 1 .74 12.5 .41 4s 1.35 14211 .74 falling in the other bands where they would This popuL, u . Ibe ;,rot army of short- 15:: .74 tho ! .68 2511 1.13 affect the oscillator in use. The other two poles wave e11Uw1-ia.l, `ecentl' :equirert a third for Si .50 .50 SAS .80 more knowledge nn stn .hors ay switch both the control -grid and cathode the SHORT W.55-1-7 .29 56 .33 2 t .30 of C11AFT, monthly magazine. : ontains everything you .32 57 .50 2AI; .50 oscillator circuit. want on kit. labuut the art of Short tt'aves. Ili .36 58 .50 2A: .60 The coils are the hardest thing to build and The wonders of world -aide shot t.w awe rrreption are i1 .36 :I.\ .32 211: 68 clearly described amt illuOated in each issue. Later i2 .63 7, .50 .1A7 .60 it is recommended that a set be purchased that practical information for radio fan., experimenter. anti o'3 .63 77 .54 tilt: .63 corresponds with the calibration shown in Flit. "ham." will be found or tremendous Interest. Tell. you 11 .68 74 .34 6E6 .30 Isms' to build .bnrt'wave re, elver- und 4. is tran.udtten; roe .r. .50 110 .32 opti .50 However, below listed the data for winding .trurt set. of one and tail tubes or a: many a ven. 36 .50 21111 1.13 ..E: .72 the coils. eight or nove. Tells bed foreign at at Ions. to Tog e ami .39 82 .41 2 /,:: .34 olden to rule tue Esrey month nui be found nett est ;5 .50 83 .50 121:: .50 COIL FRED. TYPE OF SIZE nul bed ui still. toff the time. SPOILT WAVE CRAFT No. RANGE :m -II .54 Cl .59 .55 /a .72 WINDING WIRE I. a tamtillalill_. i:t- reluise Inagatine, edited by lingo I1 .50 X99 .45 Ts is- 1 -V .30 I -OSC 26.7 roc. Solenoid 26 Gernsback. V99 .56 21ta 1.13 2 -OSC. 8.5.2.Smc. Solenoid 26 12 .54 NEW FEAT, the 43 .57 11m; 3.26 3 -OSC. 2700.800k, Solenoid 32 lt}: ItE''}:NTLv ADDED T. .hot 4-0SC. 900.3001a. Universal 36S. S. E. wave fan who tut lugged atol obtained retitle:oiml of Ille -state If stmt jobber e now till your order prtain,t ly .t t l i 3 -OSC. 360-1101o. Universal 36S.S.E. largest unadær of hnrt station. from all over the direr, to us for immediate shipment. 6 -CHOKE Universal 32D.S. nord during one mouth. will be ail tradd a magnifivent TURNS FORM NO. 2I- :diver trophy. No order for les. than 8:I no cant br II, t,'pre-I. no' COIL OF 25'; ekposit, balance C.O.D. All tube prices shown No. TO TAP INS. TURNS are net-and Orders are F. 0.I1. fa. tors'. IP i iI-TV 9 16 TARES OR MuaE ARE ORDERED. OItDFatS .titE 2 flt 9 16 32 3 30 9 16 NII I PREP.\ it). I'l'ED 4 30 9 16 150 5 75 9 16 300 Special Offer SPEED RADIO CORP. 6 3 8 300 f1 .14 40th Avenue Long Island City. New York tb Coil Nu. 1 is space- wound. (This spacing is and Users -write for our special Jobbers Large done by winding two wires at the same tine. tdttr. This Month Only and when the one to be used is properly secured the remaining wire is removed, leaving an accu- For for r fa... -tober only. we rately- spaced coil.) The remaining coils are offer resat., td till: sagaz] l, - - - colt)- to read radio'. greeted shag- tight -wound. pave manan n.- special saving. The regular sub.erip- The R.F. oscillator section of the type 77 tube IHml psi year. You Cali now get .tusar 0,1%.\ 11.31 -'1 ¡1 WAVE r nest Elcht Month, for One IMllar. is modulated at A.F. in a novel way -that is, The mulas u, ,ke. it nleni for you tu -end us i in the screen -grid circuit, which is the anode your ruh.erin'. -I'CD IT I TOD. \Y. of the oscillatory circuit. The audio frequency 4.Calor Cover 9" a 12" oscillator uses a type 76 tube and a push -pull Over 200 Illustrations ? audio transformer for the modulation trans-

former. Figure 3 shows the way the transformer 25c The Copy is assembled before it is ready for use. All the ./ %Z ear! "1" laminations are removed leaving only the "E's ", and a block of wood is used to replace the "I" laminations that ss'ere removed so that the old mounting bracket can be used. MI/VIN 1: Cl/IL The untapped side of the transformer is the grid coil and one half of the tapped side is used in the plate circuit of the audio oscillator. The Microphones unused half is used as a pick -up coil to introduce the audio signal into the R.F. oscillator An improved type of moving roil mitt union 1. non' cir- available,. at low mat. to the general Public .4b ire... cuit. If when the generator is assembled the Ilroadtaa and Talkie.- Recording trade. Thi hntrument audio oscillator does not function, reverse the tbararlerislirt of mewl. toil retains all the de. irable connections the grid coil the mleronhanes -Ian luit itit It. iii . perm it ln¢ loue tran mils - of to make phase n lines without not -o pick -up: freedom from lo' --, etc.; relationship correct. tondit tou, and. performante unatttrted bt atmeapherie The attenuator consists of a 100 -ohm poten- operation while being neon] around. Tite new standard and deluxe models. Mlnving Coll Mi. rd- tiometer. This should preferably be tapered to little offers the fol too lug features: wide - avidi' pick -pry. 25 ohms at 50" of the rotation so that the scale oh'. eliminates grouping: rugged must net ion: -null dhneaons, making concealment omen tent. ami high. will not be too crowded at the low- signal end, totality pick -up. with re.pnnae flat to 3.000 iv. -le and although a standard potentiometer may be used. 51110 without :Inning 5 db. at e)-elcs. redstart, peak-. The chokes and condensen used in the line Specifications: tleiti roil. 2 to 6 volts: voice roil. 20 ohms. (The Deluxe umd.9 is equipped with su.pen.lon prevent R.F. from feeding back into the line and oke. thus into the receiver on test. These are very Standard Model Moving Coll Micro- and the success instrument On All phone matching auto- trans- 4s14s essential of the de- ner)(withtut pends on this filter system. News- Figure 2 shows the chassis. shield, and the SS, wLinloi,,l other metal parts that must be drilled. with stands RADIO F,QI'IPNE\T CORP. dimensional data. These parts may be made of 155 East Genesee St.. Buffalo, N. Y. steel, aluminum, or any other available metal. SHORT WAVE CRAFT Dept. RC-133 Angeles Office: Company. 1026 S. 99 Hudson Street. New York. N.Y. LOS s ics. thenstein the signal is completed and R Hudson Street After generator New York Office: Albee Radio Coro.. 16 shields in place. reverse coil of the Gen lemeu: F:1n lutol not will find m0' remittent: of New York. N. Y. the grid f '.loin plra-e :end one a sub.rriptioe t" modulation transformer. if necessary. If the sig- SIIOI4T t \'d C}: l'It. ET for nal works satisfactorily the problem generator t I Eight Months 0 S1.00 (Ca liada and foreign. $I. -.0t f calibration is next. The simplest way, of ( 1 Sixteen Months t $2.00 Is'auada and foreign. .CS. out course, is to calibrate with a calibrated all -wave When It's Needed in a Hurry! receiver. but if higher accuracy is desired, the None best way would be to compare directly with Servicemen -Amateurs -Experimenters Addre.. Depend on crystal -controlled stations whose frequencies are BURSTEIN- APPLEBEE CO. known. City _ State America's l.ive+t Radio licol.e As is shown in Fig. 4, ranges 3 and 4 cover in America's Handie.1 Ship- the broadcast band. These bands can be cali- ping Point. 148 1012.A Meese 8t. Page. brated by comparison with stations in these Kane. City. M e. Please Soy That Yon Sale It ie RADIO -CRAFT Rr,DIO -CRAFT for JANUARY, 1935 435

bands. The receiver that is used to calibrate the generator is set at some known frequency HOW TO BUILD A NEW 5- and the generator is tuned until a beat is found. this beat being carried to zero. and the point METER TRANSCEIVER Working With One indicated on graph paper. this is If procedure ( Cont i,uud frout paps 06) followed at several points on the band, a curve can be drawn. to guide the assembly. but, in order to facilitate Hand Tied Behind? Range 5 may be calibrated by the harmonic the work, it is best that the following supple- How rnethtsl. For instance, the receiver used may be mentary explanations be observed. often have you spent hours, perhaps days, set trying to locate the cause of oscillation in a radio at some known frequency, say 000 ke. The .006 mf. condenser is connected between receiver? When You checked the screen bypass capaci- the generator dial is moved it will be no- the R.F. choke and the ground lug. The 250,- tor -tried to lower the potential ticed screen -removed that beats will be heard. Analyzing these 000 and 10,000 ohm resistors connecting to the the tuning capacitor and cleaned the wiping con- heats (being careful to avoid taking cognizance "Transmit -Receive, switch are supported) away tacts, installed pig tails, bonded the shielding, and of beats resulting through reaction with the from the switch by their pig -tails and must not tried to re -align the tuning stages, but still the local oscillator in superheterodyne sets) it will be touch it. The other pig -tails are twister) to- radio oscillated and refused to operate satisfac- found that the following occur: gether and soldered. forming a connection to torily. 100 ke. its 6th Harmonic being 600 he. which n wire is soldered. The .00015 mf. mica Then, you probably packed up the receiver and 120 kc. its 5th Harmonic being G00 ke. condenser is connected between the 2 inner lugs carried it fo a jobber whose service department 150 kc. its 4th Harmonic being 600 ke. of the 5 meter coil. The remaining 250.000 ohm may have repeated your "cut and try" methods in 200 kc. its 3rd Harmonic being 600 ke. resistor is connected between the terminal strip an effort to locate the trouble. Finally, a pro- cedere 300 kc. its 2nd Harmonic being 600 kc. and the 6 prong socket. It must be supported of substitution of parts was tried as a last resort, and was By repeating the above procedure and plotting by its pig -tails so that it does not touch the it found that the trouble cleared up when one of the electrolytic filter capacitors these points, a curve may be drawn. If a super- 4 lead transformer over which it straddles. was replaced. heterodyne is use,) receiver to calibrate the gen- The inner winding of the 5 meter coil, shown erator, care most be What was wrong with the original electrolytic taken that the signals do connected to the stand -off insulators. is nut to not beat with the capacitor? You probably assumed that it had intermediate frequency. This be connected until after the transceiver has been will be easily determined by turning the dial of "opened up" or lost some of its capacity, and tested. you reasoned that you could have saved yourself a the receiver every time a beat is found. If the lot of lost time modulated and trouble if you had been able signal still remains. although the bent Testing to check the electrolytic capacitor, but you did not vanishes, it will be known that the signal is at Place the 41 and 37 tubes in their printer have facilities for measuring the capacity of elec- the frequency of the intermediate frequency of sockets. Connect the positive post of the 0 V. trolytic capacitors. the receiver. Therefore, these points will not storage battery te terminal 1 and the minus In other words, you did not have a Supreme be used in the calibration. post to terminal 2 of the terminal strip. Snap Model 333 Deluxe Analyzer which is the first and Calibration of bends 1 and 2 will be rather un the "on -off" switch. The heaters of the only analyzer to offer facilities to measure elec- hard unless both care and time are taken. There tubes should glow. Connect two 7t_ V. "C" trolytic, as well as paper capacitors, in six ranges are numerous which sources from reliable signals batteries in series. Connect the plus post of from 0.001 to 12.5 mfds. can be heard. Station WWV at 5,000 kc. is the one to terminal 3, and the -3 V. post of the outstanding frequency standard for this country. other (giving -lot V.) to terminal 6 of the The several amateurs have in their own bands. terminal strip. Connect three 45 V. "R" bat- The various commercial short-svrve services are teries in series. largely crystal- controlled and sufficiently accurate for calibration. Even at the highest frequencies, Connect the minus clip to terminal 4 and the plus 135 V. clip to terminal 5 fixed frequency band services are now in use, of the terminal strip. The wires be mostly on phone. with a battery may of any con- Hence, reasonably- goad venient length all -wave receiver, and care to have the right beat or a battery cable may be usel. If greater power is desired, use four 45 V. from the signal generator, it is fairly easy to "li" batteries in series to give +180 V.. and connect provide a sufficient number of points in each the two 7rt. V. "C" batteries to give V. band so that reasonably accurate curves can be -13'_ drawn. ¡'lug a pair of headphones into the double tic jack for phones and If the constructor of this signal generator turn the "Transmit- Receive" switch to the right (Receive follows the data given, especially that of the pusitiou1. if everything is in order the characteristic colts and the tuning condenser. it will be Pos- sible hissing sound of super -regeneration will be heard io match the calibration given in }Sg. 4 as in this calibration the phones. If the transceiver does not was made with parts of the same super -regenerate, SO,' ificxt ions. disconnect all the batteries -7 o p e 0 and recheck the wiring completely. Plug a sensitive single- button microphone into the -fito double tip .lack for microphone. (The micro- ®® phone current is supplied by the "A" battery.) Turn the "Transmit- Receive" switch to the "Transmit" position. With a short piece of wire momentarily ground the upper pin of the SUPREME 333 DELUXE double tip jack for phones to the chassis. Speech should now be heard clearly in the head- RADIO ANALYZER phones. (Ordinarily. in transmitting, the phones are disconnected by the - "Transmit Dealers Net Cash 9,95 Receive" switch to avoid microphonic feed- $ 3 back.) Wholesale Price If the transceiver has been found to test Supreme 333 Standard properly. connect the inner winding of the 5 Radio Analyzer $29'95 meter coil ta the 2 stand -off insulators on the top of the cover with 6 in. lengths of wire. Under today's service conditions, if you are Then clip the cover over the chassis, fastening working with art analyzer that does not give you the two together with 3 self -tapping screws on this facility, you are slowing up your own skill, each side. shrinking your own income -it's like working with awn! +st0oat0eDe0eUA0770ttla07e0s0a370lteltD rt one hand' tied behind you. And when you pay as aarootwsmsso.00.sos0oxesoososro 150 DOD AD ee much as $40.00 for an analyzer, you are entitled 503 MD Vm 50D tpro tfro tam wc Antenna to a complete electrolytic capacitor tester, as well e111 u2/1 26 te32 16 400.6e52 56 6014 te72 26 e2.a4 50 Because of the harmonic effect, an ordinary aa m w0 un 161) 770 760 trc as a complete analyzer. The Model 333 DeLuxe broadcast or short -wave antenna may he used Analyzer is the only way to get it. for 5 meter work with fair results. In this Ask your jobber to show you this supremely fine Fig. 4, above rase, the antenna is connected either stand to -off and complete, compact radio laboratory. Includes Representative output -frequency graph. a is -on masted insulator. while ground to the such additional exclusive features as circuit for other. If a doublet antenna is e used the lead -in compensating effects of temperature and other Fig. C below is connected to both stand -off insulators and no variations of the full wave rectifier unit, free refer- Underside view of 3 -tube oscillator. ground is used. ence point system of analysis, Supreme's 5" fan - However, for the most efficient opera[' any shape, full- vision meter. Meanwhile, write for de- data and complete catalog on one of the variaans types of 5 meter antennas tailed technical Supreme instruments. should be used. An efficient antenna is obtained by suspending an S. 1G. 32, G4 or 128 ft. length SUPREME NEON - of wire horizontally or vertically and as high IZED TUBE TESTER as possible (the higher -the better the results) Portable Model and connect a lead -in 10 it at a point 1'7 of (85 its length away from the center. The lead -in -P) $ 3 9.95 must extend at right angles to the antenna for Upright Counter a distnnee equal to at least tí of the antenna's Model (85 -C) .... length. The rest of the lead -in may then be of any length and is connected to one of the stand- TUBE TESTER MODEL 35 $29.95 off insulators. The other stand -off insulator may be connected to gròund or left unconnected entirely. SUPREME INSTRUMENTS CORPORATION. Fur portable operation, the simplest antenna 512 Supreme Bldg., Greenwood, Miss. is a 4 ft, length of copper or aluminum wire. Please Say That You Saw It in RADIO -CRAFT 436 RADIO -CRAFT for JANUARY, 1935 rod or tubing, attached directly to one of the stand -off insulators and extending vertically HOW TO BUILD, TEST above it. The other stand -off insulator may be left unconnected, or may be connected to the AND REPAIR transceiver case or nearby metallic body (as a counterpoise) ; or it may be connected to ground. RADIO Experimentation alone will reveal which method is the best. EVERYDAY SCIENCE AND MECHANICS is the SETS finest scientific - technical - mechenicel - Operation eonstructienal na naine in the field. Up.to-,he- wi,h n es flasher of ,eientifie events Doses With the batteries and antenna connected and of construction.] nrt isles and many popular experi- the "Transmit- Receive" switch turned to the ment.. Ido, from which yn Vara make thine. to nil. "Receive" position. the hissing sound of super - regeneration will be heard as the tuning knob A HOST OF INTEREST. is turned. However this hiss will be moderated INO SUBJECTS COY - or will entirely disappear whenever a signal is ERED:-Wmdeorkinr- tuned in. Photo.rnphy - Magic - The frequency for both transmitting and re- Patent. and Invent...- Radio Construction Hook Reviewe-Metol- ceiving is set by the tuning knob and dial scale nrkint -Chend .- on the front of the transceiver. To minimize Enam rin - Micro- Library hand capacity effects in tuning grasp the knob rrc Eintriw Including Television. Short- Wave Receivers and Auto at the extreme end. The frequency range is nerirnente - Hower- pages, 561 illustration Radios. 3 Volumes. 5',ía8 -1177 approximately 50 -63 megacycles. permitting the hold Help. - Shop This practical Library includes: PRACTICAL RADIO- which n in t r nod other The fundamental principles of radio, presented in an reception of special experimental stations. understandable manner. Illustrated with working dia- may be located outside of the amateur 6 meter grams. PRACTICAL RADIO C'ONSTRI'CTION AND band. Get your cony today! REPAIR- Methods of locating trouble and reception all newsstands workmanlike repairs. Discusses mod- Identification of the 5 meter band can be ob- On faults and making 10c the copy ern Short -Wave Receivers and Inst allanon f automobile tained in localities where there is some 6 meter radios fully. RADIO RECEIVING TIItE.S- Principles activity by contact with other amateurs who underlying the operation of all vacuum tubes and their Over 150 use in reception, remote control and precision measure- have calibrated frequency meters, or receivers. ments. Otherwise a calibrated frequency meter. or wave IBustratwns Helps you to understand Modern type receiving sets - full of construclion data and prat trail kinks fur the ex- meter, or lecher wire system must be used to perimenter. check the frequency of transmission, in order 10 Days' Free Examination Easy Terms to be certain of legal operation. The battery current drain is greater when Most Amazing MCGRAW -HILL transmitting than when receiving. For reasons FREE EXAMINATION COUPON of economy, then, turn the "Transmit -Receive" switch to the "Transmit" position only when IYPEWRI1EQ rMcGRAWHILL BOOK COMPANY, INC. you are ready to talk, turning it to the neutral 330 W. 42nd St., New York. immediately after- Gentlemen:-Send me the RADIO CONSTRUC- or to the "Receive" position, TION LIBRARY, all charges prepaid, for 10 clays' ward. In the neutral position the battery drain BARGAIN Free Examination. If satisfactory I will send 61.50 is completely been is reduced, but the transceiver in 10 days, and $2.00 a month until $7.50 has is Paid. If not wanted I will return the books postpaid. turned off only when the on -off switch EVER snapped off. Name The transmitting range, as with every sort of OFFERED Home Address 5 meter equipment. is greatly dependent upon from elevations State its location. Over flat country or City and overlooking the surroundings. distances of from Position 10 to 20 miles may be worked. From higher Name of Company It(' -1 -35 elevations even greater distances are possible. Because of the quasi- optical nature of 5 meter waves, the limiting range upon transmission and reception appears to be the line -of -sight distance as determined by the curvature of the EXACT earth and intervening topographical obstacles. DUPLICATE List of Parts NEW CONDENSERS The kit contains the following parts for building a 6 meter 6 V. battery operated radiophone Take the mys- transmitter -receiver. REMINGTON I. I'QiIIIIhIllll tery out of elec- One I.C.A. 5 plate midget condenser, 15 mmf.; One I.C.A. 5 meter 3 winding coil: PORTABLE only trolytic blocks! One I.C.A. transmit- receive switch; 41CID FIRST TISIEI Remington s The TOBE label Dry Electrolytic One I.C.A. R.F. choke; new purchase plan now lets tells you all! cmnp1.1. Two I.C.A. double tip jacks; you buy a genuine latest model Remington Port- One I.C.A. 5 prong socket; able No. 5 direct from the factory for only 100 a Make of radio, day. Not used or rebuilt. Not incomplete. A beau- One I.C.A. 6 prong socket; tiful brand new regulation Remington Portable. mode 1, factory Two resistors, 250,000 ohms, (red body-green Standard 4-mw keyboard, standard width carriage, margin release on keyboard. hack spacer. auto- part number, ca- end -yellow dot) ; matie ribbon reverse; every ementiel feature found pacity and voltage One resistor, 10.000 ohms, (brown body -black in standard typewriters. %LC 820 17.18 With your maohinewo send you/We a l8-page course 001aS end -orange dot) ; of each section, rAAT Ms, In ty1ewriting.Teaches touch system qtuck ly.eaeily. op One cartridge condenser, .006 -mf.: &mu you dash off letter. quicker than and color code. One mica condenser. .00015 -mf., (orange - with pen and ink. You also get a hand- FREE some. atiinly carrying ease tree. brown -green dots) ; o..i.. o."r..; Typewriting Electrolytic One I.C.A. output transformer. with 4 Course BIG PRICE REDUCTION condenser blocks leads) ; The amazing low price and easy terms One I.C.A. microphone -audio transformer. now make it possible for you to buy . like the one illus- wu this genuine complete Remington sa (with 6 leads) Portable for only Mc a day. But we trated are avail - One I.C.A. on -off switch; cannot guarantee present prices long. Higher wage scales, rising cost of ma- able at parts job- One I,C,A. 100 -0 dial scale; terials, everything points to higher One I.C.A. pointer knob: prices. halo bers everywhere Two I.C.A. stand-off insulators; our offer still holds good! for all popular re- One I.C.A. 6 terminal strip: FREE You Don't Risk One Cent ceivers. One I.C.A. drilled chassis and cover: Carrying Try this typewriter In your home or Two insulating bushings; Cow office on our 10-day FREE TRIAL OFFER. Then. if you do not agree Six brass bushings: that it is the finest portable at ant/ Tobe Deutschmann Corporation Hook -up wire. hardware. piles, return it at our expense. Yea The following accessories will be required: don't evert risk shipping charves.Don t CANTON MASSACHUSETTS cwait. Mail coupon now. It's the best One Sylvania type 37 (or 76) tube; hance you've ever had to own so One Sylvania type 41 tube; complete a machine for so little One pair headphones; money. So act NOWT One Shure microphone. single button, 200 ALUMINUM PANELS ohms. high gain; CLIP COUPON NOW 1e Gauge 7x12, 28cí 7.14, 32e One storage battery, 6 V.: Remington Rand Ino., Dept 180.1 5/64 Inch or 13 Gauge 7.10, A A.e Three "B" batteries (or "B" eliminator). Buffalo. N.Y. 7.12, 34e 7x14, 41ct 7.18, 49ci7a24, gee fa7{r 45 V.; Thr.e eanel ore n isl lot al th. odotrprice. Longer nod Please tell me how I can buy a new Rem- i it, t a.poni gly prise. Add qtr.. for Two "C" batteries, 71 V. ington Portable typewriter for only We a day. e. I, Ñ'e do not poll.. ea, E ¡mates rindly 1 ni,l ed Also enclose your new catalog. r.n Material for antenna (see paragraph "An- r"""'"" asdic rte for ever 10 yeah. BLAN THE RADIO MAN, Inc. tenna"); Nanu 177 Greenwich St. Dept. RC New York N. Y. Stranded insulated wire (or 4 or 6 wire bat- Address 444/4444444444'.4444'44,0 .04' tery cable) for connecting batteries. city State Please Say That You Saw It in RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935 437 READERS' DEPARTMENT (Continued front page 415) New, Better, Lower "DEPENDABLE" If the personnel of other broadcast stations Priced operating on wavelengths above or below our "domestic" range of 200 to 550 meters care to ANALYZER UNIT address letters of a similar nature to RADIO - CRAFT, we will be glad to print these letters I'ST connect the new "DEPENDABLE" Model 501 in our READERS DEPARTMENT, or TIIE LIS- ANALYZER UNIT to the meter of your obsolete either analyzer better still, TENING -or to the new "DEPENDABLE" POST FOR ALL -WAVE DX -ens. 403 -A MULTITESTER, and you will have a modern A view of PSK -PRF -S is reproduced by cour- and efficient analyzer without expensive investment. tesy of Mr. Braggio. Model 501 is the only Analyzer Unit combining all of the following features: -(1) Equipped with 6 ft. 10- wire analyzer cable, 5 "Sure Pull Out" adapters, separate chassis -ground wire with insulated lamp. (2) Free ALL STATIONS ARE "DX" ONES TO Reference Point testing between any two elements, including chassis or ground. (3) Instantaneous selector THIS SASKATCHEWAN -IAN switches -no reference charts -no fussing with jacks and prods. (4) Current measurements through auto- EDITOR, It ADIO- CRAFT: matic series jacks. (5) Will not become obsolete. I am a reader from the rural sections of Can- (6) R.M.A. standard numbering at socket and circuit ada. terminals. COMPLETE, ready If I may offer my comments, would say that Compact, light, handsome. Includes Adapters, Leads to Opt rate. 510.95 I would like to see more articles concerning bat- for Current Testing. Open face, with tool and adapter net. KIT, $9.25. tery or rural -type sets, and would it not be compartment. possible to devote a page or two solely for the benefit of beginners who, as you know, constitute the future market for radio equipment, magazines, etc.? COMPLETE, ready we have no power New, Better, Lower Priced to operate. S13.95 In this part of the country $10.65. limn and no doubt you have many such readers. net. KIT, I may say that in this country practically every one has a wind -driven generator with which we MULTITESTER keep our `A" batteries charged and they work SERVICE men and dealers highly praised the Model fine. 403 Multitester -and it deserved praise. But the new you it would be of sufficient interest. improved Model 403 -A "DEPENDABLE" MULTI- If think TESTER insures even greater satisfaction at less cost. can you publish the constructional details of an Embodying every feature of the former model, No. "A" battery eliminator which would deliver 403 -A is more compact, having been designed as a around 175 V. from a 6 V. "A" supply (with- companion instrument to the new Model 501 ANA- out too much drain from the "A ") ? LYZER UNIT described above. There are a number of these on the market 2,000 ohms per volt. Accuracy within 2 percent in now for auto -radio use and if we could get the D'ARSONVAL type moving coil meter. 3 -range details of one suitable for use with the stand- 0. 2,000,000 ohmmeter; 4 -range 0.5.50- 250.750 voltmeter; ard battery set, it would he just the thing for 0-500 microammeter. Complete, with self -contained we rural readers in out -of- the -way corners. batteries. FREDERICK Box, Write Dept. RC -I for FREE Data Sheets Courval P.O.. Saskatchewan, Can. RADIO CITY PRODUCTS CO. 48 West Broadway, New York City "DEPENDABLE"

These comments by Mr. Box represent the ex- pressions of a great number of readers of RADIO - CRAFT. and for that reason we continually present in our magazine much that is of an ele- The 1935 - nature. (See the crystal set. and 1 OFFICIAL RADIO SERVICE MAN mentary UAL will be off press shortly. In order to and 2 tube receiver articles by Mr. F. R. Harris, YOUR LAST / in past issues.) We hope that our more tech- make certain that you get your copy at a advanced readers will forebear to com- special saving, be sure to read the announce- nically ment which appears on page 390 of ment too harshly concerning some of our pages OPPORTUNITY' this issue. which seem to be "too elementary" (as some of our readers have put it). The schematic circuit, and a description of the use of a "tube -type" "B" unit operating from a 6 V. "A" battery are contained in the article. "Build This All -Wave Set," in the November, \t 1934, issue of RADIO -CRAFT (a correction concerning this "B" circuit appears in the INFORM A. TION BUREAU of the current, January number): A "how -to- make" article concerning a "B" unit is the one entitled, "A 'B' Supply for Farm or POWER TRANSFORMERS! Auto Sets," on page 280 of the same issue. (Patents Allowed) The December number contains. on page 344- the STOCK OF ONLY FIVE (5) POWER TRANSFORM- article, "How to Build a Tubeless 'B' Supply." ERS provides immediate renewal of original perform- motor - Units of the rotary type (such as the ance in case of trouble in the transformer -the heart of grnerator) also are recommended. the radis -in any of over 95% of all radios- whether Regarding "beginners" material. we are re- "orphaned" or current models. luctant to print very much in the nature of elementary articles concerning radio theory, in- The wide range of asmuch as the shelves of the thousands of pub- &ad dap&Cate4 ELECTRICALLY adaptability of only lic libraries throughout the country are heavily five ",lets "Matti =rap" universal Power Transform- "bowed down" with books that go into the sub- ers is t made possible through various taps in these units ject of elementary theory from every conceiv- which may be used singly or in combinations. The required current values can be eliv- our readers are prac- ered to each of the several leads in the set with any combination of tubes, as accurately as able angle; also, most of by the original power units. Easily installed. tical radio men -not only professionals, who make their living in the various fields of radio, The extremely wide range of adaptability physically is Niue, lañ ladapta 6 FNrstutuY made possible with the scientifically calculated staggered but, as well, experimenters and amateurs -who, slots of expensive self- tuition in the School mounting in the several sides of the frame. This is very essential in many installa- by reason tions to avoid redrilling and defacing the mounting panel. of Hard Knocks or the more gentle education one IMPORTANT. Fully shielded for radios having Underwriters Lab. approval. Protects set N derives from a resident -or correspondence -school owners fire insurance policy. No extra course, have mastered the essential fundamentals unused leads to become shorted. of radio. "Multi - MAIL THIS TODAY most General Transformer Corporation, Instead, we believe, and we are sure that Tan" 504 S. Throop St., Chicago, III. of our readers will agree with us, that a page / Guide, different. e listing Send me without charge a copy of "Multi -Tap" devoted to something new, something liir42111 models of radios which you can im- Guide with name of nearest distributor. something original, THAT CANNOT BE service with one of only five FOUND IN BOOKS, is to be preferred to ma- mediately3i "Multi -Tai," Power 'transformers. Name terial that, at best, can only be considered as a "re- hash" of text -book material. General Transformer Corporation Address 504 9. Droop SL, Chicago, Ill. Are we wrong; are we right -what say, O.Ms. City State ._.._....__... and Y.Ls.? - Please Sag That Yon Saw It in RADIO -CRAFT 438 RADIO -CRAFT for JANUARY, 1935

NEW DESIGN IN ALL - WAVE ANTENNAS (Cool ia,rrd Jruru page 413) tents between the antenna and the newly Mr. E. H. Rietzke. President receiver impedance -matching trans- of CREI and originator of the t developed first thorough course in Prat- former which is connected directly between tical Radio Engineering. the lower end of the transm is line and the antenna and ground posts of the receiver itself. Are You Doing the Work That The impedance of the transmission line is approximately Ii ohms and the input imped- ANY Service Man Can Do? Hance of the receiver transformer employed as sl -n in Fig. ID, is also approximately 70 Every year UlwtsuMIS of men j.m;n the ohms. The output impedance of this trans- crowded service field . . . yet, every former may be selected by means of simple year only a few of those equip them- telephone tip -jacks to match receivers with selves to handle bigger, better and either high or low input impedance. A third more service work. Radio is setting a connection is provided on this transformer for which enables the entire antenna plus the fast pace, new developments call lead -in. to be utilized as a regular T -type increased knowledge, and more Serv- antenna, in areas where noise occurs on one ice "Engineers" rather than Mechanics. band and not on the others. This new trans-

' former which is very simple to use incorpo- CREI Training Is Available rates some of the most advanced radio engineering and provides, for the first time, a To Every Service Man .. . means of coupling a transmission line to the ordinary type of receiver without requiring We actually know that there are many any changes in the receiver itself and without ambitious Service Men who would wel- noticeable loss in either the broadcast or the come any opportunity to improve short -wove bands. In fact there is an actual themselves by studying to meet the gain in the broadcast band. needs - ever -increasing of the present HOURS day Radio man. The complete train- Improving All Doublets Z o ing that our courses offer is available The new type of all -wave antenna system to everyone at specially arranged employing a doublet for the horizontal por- of Reading Pleasure terms. Write today for complete tion of the antenna may be made to operate details. satisfactorily over all the existing wave -bands as a result of some important developments New 1 I -Page 1'stlssIis in impedance- matching transformers combined Many Stirring Stories with accurate fixed condensers. The funda- Mailed on Iltaqutavl system employed in this intricate net- of Future Science in Current Issue mental WONDER STORIES brings to lia readers vivid, thrill work is shown in Fig. I and the theory of Ing, and absorbing tales of adventure on allen planer, CAPITOL RADIO the operation of this complicated looking -stories of biological monarwitiec, time -travel, th+ future civilization. of man, and other educational ENGINEERING INSTITUTE system is not very difficult to understand. It science -action themes. 14th and Park Road. Washington. D. C. is common radio engineering knowledge that Ctmtento for .January: TILE ATDDEN COLONY by Otfrid Dept. RC -I fixed condensers have a lower impedance at n H.disle n. THE PRENATAL 1'I.5ta.tRlS'I he ilortl- than they do ut low frequen- r N'eisiuger. ONE -w.tv TlNNF.1. by lias- id Ii. Kellen. high frequencies 51.1... TIIF: EMOTION sus:TEIL: by W. Yarbk Nain- III. cies. Therefore, when the receiver is tuned MASTER OF 'rIlE I. KNF :S be Edmond Hamilton. to the high frequencies, that is. any of the 1111S \III' JOKE by Irsl le 1'. Shale, and li.ttt'N T11 Ili -sl( by F :solo Binder plus era) Inneresl lag depart short -wave bands, the impedance of conden- t el .bort items.ms Th ariaari of Ilk. INTERN.tT1ONAl. sers Cl and C2 shown in Fig. IA offers the Si'lKXl'F: rli'TION LF:.til POWERTONE of resistance to the incoming radio year for $2.00. path least SPECIAL OFFER (in U.S.A. only) -One Portable waves which pass directly through the con- Send check or money order. Oscillator densers to the low- impedance transmission - WONDER STORIES. 99 -R Hudson St.. New York. N. Y. I: line. From this line it goes into the receiver l impedance -matching transformer and then, by "l- It e primary one of to r:le is cull three distinct methods, directly the bnn,rl from :d1 receiver. to VW K.C. The It is also well .understood in radio engineer- I THERE'S GOOD READING IN I hors are 1 K.('. ing circles that a doublet antenna cut to a ap:rrt Don ill e on the -wave to SO K.C., Lawhich is most efficient short and 2 K.C. hand will not function satisfactorily when :,port front SII -rd in the broadcast band. For this reason I., 1511 K.C. :lie transformers shown at either side of the Therefore when ail srllli Till il,,, ted line fin Fig. IA are utilized to carry ItififAS .I v,rs nu- the broadcast signal into the transmission line ing the IOili at a considerable gain over the signal which hannunirl tali:n the .eparallon as regtsleled by for - could be possible without these transformers. ADVENTURES liott points is 10 N.U. from 'ail In Milli K.1'. t, I-'. In this case the impedance of the transformer oi'ihe Upper r,r +,nn.iary aale the popular inter- very Magazine .Iidtr is much lower than the impedance of the &ritten, h are clearly marked: 175. _d.l. Don't t s the t O1111'I.IIY NOVEI. in Ant 4311 N.I'. kith 117.5 -175 -172.5 +tauest. fixed condenser and the incoming broadcast "Itbc I FBKUARY ISSUE Moulded Its a oral lealhetelle case. kith gent'.. signal passes through the transformel in leather hxn.11r and removable covet. preferanre to the condenser. A.C. MODEL LEONARD H. NASON'S Model 66 uses Mlle NOTE: -It should be borne in mind that MODEL $6.75 each half of this antenna impedance- -THE \X'AR GANG" Model 66 -B u- _., .o. two. !?;',/n: matching device we have a tuned circuit com- SEND tor FREE Catalog story by an author known all over the prising the inductance LI and condenser Cl isurld for his exciting and authentic TRY -MO RADIO CO., INC. in one case. and L4 and C2 in the other case. stories of the War SS -C Cortlandt St., New York City Bath these circuits have infinite impedance :r frequency to which tuned and ALSO SHORT STORIES BY CAPTAIN the they are DINGLE. FRANCIS BOTCH, AND therefore this point of resonant frequency PETER Ht'N'Fl.11' M.IcA'RTHUR ntttst be located in some portion of the fr.- quency spectrum which is not used for either Look for 1935 POSTAI. SW the short -wave or the regular BOOSTER broadcast bands. HIGH-SEAS ADVENTURES now on I.ErTYut Special Adaptations all newsstands tpl Iris hse easily roua, Where any type of doublet is used, includ- a Copy or all-kart. ing double -doublet arrangements, the system 15c +upp 'r nl r the n shit i? ua ,.1.,. shown in Fig. ID improves performance. The idly kt y teceh, -r ever Lae. fundamental circuit is shown in Figs. IA and saur um 1.14I111.11,1..lr.l. 'netu tu are those m eak forei_u .tll,m- IB. Both the units shown coupled to- kith a ' Postal IntO:l'F.It. gether by means of the necessary length of Write Immediately fur 16. special cable, in the manner shown in Fig. pape descriptive booklet and s.erial ICC oiler. ID. One distinctive feature of this arrangement is that the length of this cable is not POSTAL ©R AIDS C important. It can be any length from a few 135-K LIBERTY ST. NEW YORK. N.Y. feet to several hundred feet.

Please Say That 1- no So w It in RADIO -CRAFT 439 RADIO -CRAFT for JANUARY, 1 93 5

The manner in which the duplex coupling device, shown in Fig. IA, operates has been described. Fig. 18. represents one of the receiver impedance- matching devices of an early type in w hich n multi-point rotary switch was employed. This has been replaced by the improved type of unit shown in Fig. IC. The use of pins and pin jacks assures perfect contact and presents a tare getting inside the unit, through the switch opening. It is important to keep the lends from the receiver transformer as short as possible. The red and black wire, supplied with the transformer are of the correct length and they should not be lengthened. This is particularly true of the black wire. Increasing the length of the black wire will tend to throw the entire system out of balance, resulting in a reduction in its noise -reducing properties. On receivers equipped with wires in place of binding posts, connect to those wires; the antenna wire, coming from the receiver should he cut very short. National Union plays San ta Claus For the best results, on ail bands. it is we4 suggested that the user try the various con- to Service experts all year round! a those which nections and keep record of NATIONAL UND )N gives tuts. testers. set anal y zrrs, scilbdors and Sf.rvire manuals wish tu prove most suitable. In the vast majority of punL;Iws. National I.aloft gives there a:doable instruments old servicing las,ks so that instances the best results will he had from service dealers can build a lues.. r better more efficient Lu,iurs for themwdves. The inseruntrnls inserting the tip of the block wire in A3 and ore all brand new models made by such Guuous makers as Supreme, I Iickok, Triplett. and N.gert. the tip of the red wire in either Al or A2 The manuals are cumpilat by John F. Rider. l! I idiot way and leaving them there. Tho alert. Sers ive+- Denier who equips himself the easy Nation knows his equipment I niuu. The difference between the doublet system is backed both by the maker and National not asailublr f any other single Ni nrew, (Fig. MI. and that shown in Fig. 2 (com- Notional Union gives sere ire charts and data monly referred to as a "ash' or zeppelin -type Na ' I Union gives sales sils sud Intiurrs formes. antenna, in radio parlance) is that the lead -in National U supplies radio tubes which are arcl ' I I.y cet ' In u-r,, amateurs and service wire is taken from one end instead of from experts for their a curacy and saga t i orit y. National I Ilion looses u e I. il to build coaslnruutr as thousand- es already dune. the center. as in the case of the doublet ii good will. You can quickly prove this fact lu yono-elf Irr doublet -doublet. Let Na ti I1 ' play Santa Clans to yon SIr. Service-Dealer 1 yon nasal sud giving your coassons This type of system nifty be made to have y giving rat the instrmnenls the line. radin',erfor they should demand: SEND the same nui se -redo ring properties as the , I regular doublet system by the proper applica- RC- taS COUPON tion of the transmission line and receiver it I I - Mono Corp. of N. Y. lull Madison Ave., New fork City 4 impedance- matching transformer. NOW The details for connecting the tra nsio i. vivo Tell mac xlxmt line to the antenna are shown in Fig. 31t. N: The connections at the lower end of the transmission line aree identical to those shown in Address the lower -half of Fig. ID. City State. Best results are secured when the horizontal portion of the aerial is in a straight line. However, where spare is limited. this portion may be zig- zagged without serious loss. In making such an installation. no sect' of tin D. R. 6 horizontal portion should be nearer than ' ALAN percent to any other sect' , as shown in Fi l. Ì. 2. The length of any individual leg is unim- portant and may be any hieh un, veniente permits. DUAL REACTION o. I _s;. DUAL -RANGE SUPERHET Employs six tubes. Dual Reaction circuit using 3- 1 -56; 1 -2A5: 1 -80. (Con t iruend from pant: 412) Built in power supply- utilize Alan silos wow,l, a- circuit front plug -in coils. phone jack. dual ratio dial. field supply. Completely enclosed in beautiful crackled metal R.I.. and oscillator coils, and a three- scctiun, cabinet. double -throw switch. The various circuits, made Cum ple.te kit of parts. including 4 sets of coils, cabinet and complete con - $2495 and broken as this switch is thrown, are indi- struurtional data, list, less tubes and speaker 541.60. Net to amateurs .. ... iinr cated in the *schematic circuit diagram. Wired and laboratory tested alti_ hit of Sylvania tubes for same 83.75 Net Referring to the antenna transformer in this 8 in' dynamic speaker to match thins! 84.50 Net (Utah., Ro/a, Magnavox l... $3.50 Net i diagram, TI is the broadcast transformer and T2 the short -wave transformer. The two pri- Order front your nearest source of supply. maries are connected in series. With the switch Washington Street New York, N.Y. i in the short -wave position, the short -wave sec- 172 Dept. ondary is connected to the grid circuit of the 6D1t ALAN RADIO R. I H.F. amplifier tube and the broadcast secondary CORP. 1028 South Olive Street Los Angeles, Calif. is short- circuited. When the switch is in the broadcast position, the short-wave secondary circuit is opened up std the broadcast secondary .AGENTS WANTED: is connected to the grid circuit of this tube. The MOTION PICTURE SOUND by R.F. secondary being used, is tuned the sec- Moat fascinating field awaits live Radio Serv- tion of the 3 gang condenser. A separate vari- ice Men -quirt+, sure profits VAN able trimmer condenser C2 is used for the short- ASK FOR FRED: CATALOGS Shunts wave secondary. S.O.S. CORPORATION The output of the 6D6 R.F. amplifier is fed 1000 Broadway New York. N. Y. and Dials into a second 6D6 which functions as the first- Cable Address: "8essund" New Ysek with schematic diagrams and hook- detector. A type 76 tube is employed in a sep- Come ups. For meter models 301, 88. 321, -324. arate oscillator circuit. A third 606 tube is used 50 millivolt; 30 millivolt, and 27 millivolt. as an 1.F. amplifier. This stage feeds into a RUN YOUR A. C RADIO 687 combined second -detector and first A.F. by DIRECT CURRENT Distributed and sold by reliable job- stage. The second A.F. (power) stage uses a bers and dealers everywhere. type 42 tube. Kato K011 tr'r ers i i t ra.to AC Radio, alnplit'.eri. Folders and list prices on request The A.V.C. voltage is applied through isolat- t rateadt te ri. etc. front Write for New Catalog No. 7. ing resistors to the control -grid circuits of the 6-12.32 or. 110 toll DC. R.F. and I.F. tubes. The audio voltage developed sent on trial. D. L. VAN LEUVEN across volume control resistor RIO is applied KATO ENGINEERING CO. -110 [pst 15th St. New York, N.Y. through the movable arm to the control -grid Mankato, Minn. U. S. A. of the 687 tube. ytsuufael ul ers of Kato AC light lilani.- -- -k t"r lie 440 RADIO -CRAFT for JANUARY, 1935 AN ECONOMICAL P.A. FREE EADI cÌ AMPLIFIER (Continued from page 412) FREE tern is a function of its power. Experience has 48-Page Supplement CATALO G shown watts of audio power de- that about 20 livered to a reasonably efficient speaker system _fòr1935! is usually adequate to meet most outdoor and to the Auto-Radio Sen ,oa r ..rv AoaF ; indoor applications. /rnJ,a 1 HoJie Yro,if Frequency Response: Inasmuch as the equip- "fA r Ir, NEW. IaalWnÌr.All-w.o Wnnn and ment associated with the amplifier is the limit- I .Shorti ing factor in frequency response, little need be Service Manual! ,Ìd1MnlaiWuhr. e_ Elrctri.. üet. inrli l and °3dÌÌ . Ii mode. nu said of the amplifier in this regard. es-cootie Pan11.a:es NEW. An entirely nr.line of m,dl.l.r'eee.rivn 'ro i Ilo nun' rho O}'F' I t' AI. ltand-.prend t'nea ith,rt Wn.'e. All-w'nye. Versatility: The amplifier design should be AUTO-RADIO SERVICE MANUAL this big .rl.ear .}.. In m2 aut,. r such is Is -pate Supplement Is issued FREE. Practically the S.W. that it suitable for permanent installa- Ì Ba.d 9Ïm. iImt. mrl pr.Arlwm mthtre ri all of the latest sets. together with servicing In- Mare than SO greet to rAenr from. tion, sound truck requirements and temporary /d m1111.11on uili be found in these new pages. The Tea NEW. An amnia. rler.i,m ..t r nip^nt: set -ups. w Suppleu.eut does not increa +e the cost of the Supreae : 8" Full \'i>iono Tri .l. a- book to but you an Auto- Itadio Servire p ir \Ìae 1 . Efficiency: This is important for two reasons. you. gives Manual that is right up -to- the -minute with serv- ióné,o ,. First, in sound truck installation where A.C. ile notes. 1935 t n- hindvion ',ices. power supply is derived from an auxiliary such as a small gasoline engine or a fan belt driven Good Money in Servicing Auto- Radios generator. Second, to keep down operating If you are overlooking servicing auto radios. you're missing a great deal of business. The auto -radio Costs in permanent installations. business hod its greatest !axon last summer when Reliability: This can hardly be over- empha- thousands of sets were sold. Ity now many of sized as anyone familiar with the operation of these same sets require servicing and with hundreds of then. right In your urn rvxrnnunity, you a P.A. system which is to show a profit well can build up a good auto -radio servicing business. knows. Breakdowns are costly incidents, when In a short time you can rosily add 25% profit or more to pair regular servicing business. NEW. A treat oec- considered in the light of rental loss and serv- Han assistedd . to Annear sen prner , icing. List to pe iv the .pier of sets covered in the Manual .l ur'' n bt..'ranerrine Arnie Radio Mfg. Co. P. R. Mallory & Co. the "Acorn" tare: the aenwnioneie Knial.t Trenreirer The Amplifier and Power Supply: Allied Radio Corp. Melhorn Radio Mfg. Co. w MAin. fer W. Transmute., and Atwater Kent Mfg. Co. Montgomery Warr) & CO. NEW. The ernten P.. A. array in podia. 4 to Electrical Audio!. Radio Co. National Co.. Inc. am., Autocrat Itadlo Company Nnblitt- Sparks Inc. Ne, °.eet re.L ¡.atlreraa. I.t'e.' pimno tend alto Intl.. nip,nem. a- Mfg. Co. Radio A, nntle..rd v near, v .roar. Referring to Fig. 1, the input is designed to Aulomalir Radio Phllro & Tel. Corp. apnrtunan vase Carter Genentoror Corp. Plerre- .tiro. Inc. accommodate a 200 -ohm line, a 500 -ohm line or Century Radio Prods. Co. Premier Elertrlr Co. Ntandatd .. Let a double- button carbon microphone. The input Chevrolet Motor Coogan Radio Chassis, Inv. o .va -nr.ne m ono transformer feeds from either of these into the Consolidated Industries, RCA-V irtor Co.. Inc. SEND FOR YOUR COPY TODAY Ltd. Sentinel Radio Corp. grid of a type 57 tube. The output of this tube Cro+ley Radio Corp. Sparks- tt'Ithington Corp. which is operated as a pentode, is impedance Helen Appliance Cmp. Stewart Radio & Tel. Corp. Allied Radio Detrola Radio Corp. Stewart -Warner Corp. coupled into the succeeding tube, also a type Emerson Electric, Mfg. Co. Stron.berg- Carlson Tel. 833 W. Jackson Blvd., Chleeso, Dept. D. 57. The coupling choke has been designed to Fada Radio & Elec. Corp. Mfg. Co. Federated Purchaser, Corp. of Am. Please send me your FREE 1935 possess a very high inductancy with Inc. Transformer ! Catalog. relatively }'oral -Majestic Failed Amer. Bosch Corp. Please quote for Kit described In low distributed capacity. This is necessary to Franklin Radio Corp. United Motors Service extend the frequency response at both the low Galvin Mfg. Corp. l'. S. Radio & Tel. Corp. General Electric Co. Utah Radio Prods. Co. and high frequency ends of the spectrum. The General Motors Corp. Wells- Gardner Company second tube is a type 67 which has its screen A. H. Grebe & Co. Wholesale Radio Serv. Co. Rudolph Wurlltzer Mfg. Address and suppressor grids connected to the plate Orig +by- Grunov Co. Chas. Ifodwin Company Co. and thus operates as a triode. Under these Zenith Radio Corp. City State International Radio Corp. mamas- wwwwwwisommumwwwisum conditions the tube has an amplification factor of 21, plate impedance of 10,600 ohms, a mu- tual conductance of 2,000 microhms and a power output sufficient to drive the power $2.50 RCA makes stage. The output of this tube is coupled to the power stage input through the medium of Over 200 Pages aerial history ! a push -pull input transformer. A push -pull plate to voice coil output transformer trans- Over 500 Illustrations fers the energy from the power stage to 9 x 12 Inches speakers. Both these transformers have been designed Flexible, Loose -Leaf Cover for class AB operation. The impedances available from the secondary of the output transformer are 8 and 4 ohms. This permits of sev- 11311 eral speaker combinations. Bias for the first ES and second stages is obtained by means of bias Atilt resistors from cathode to "B" minus. Ample bypassing is provided to minimize degeneration A1.WAVE and extend the low -frequency range of which the transformers are capable. The screen -grid .. 1933 "Provides a new source and plate supplies of the second stage are each of profit for the wide - passed through its individual resistance- capacity awake service man" -says A. H. Prow, Pres. filter to provide stability and eliminate common - Official Phila. Radio Service! Men's Association. source coupling. Inasmuch as class AB operation is a comparatively recent development, a adio EVERY home with an all wave set is an word as to its mode of operation is in order. The tubes are slightly overbiused so that with ly(anual immediate prospect...so get busy! AutoRService Tell your customers how this remarkable low signal levels they operate as class A. At levels Directory new antenna brings up weak signals, high signal. grid current flows alternately Cornplete man -made in each tube on the positive half of the cycle alrl . cuts down interference, gives . when the grid signal voltage exceeds the nega- dio R more uniform response because of tive bias voltage. The magnitude of the grid A,.tomobile Rceivers special "double doublet" feature. Kit current is considerably less than the tubes if añd of essential parts retails for $6.00. were operated class B. Hence the intermediate Fulhlnstallation -"class AB." The flow of grid cur- Guide Your installation charge extra. condition Shooting Special "Dealer Demonstrations" An- ' ouble tenna Kit, Net Price $9.85, makes possible convincing demonstrations in Underside view of power supply. MAIL THIS COUPOON TODAY! your store. Connects to four receivers. GERNSBACK PUBLICATIONS. INC. RC -135 Have you seen theremukable new RCA 99 Hudson Street, New York. N. Y. Full Range Test Oscillator? 90 to 2 5.000 Enclosed you will find my remittance of $2.50 for 'i-)' which please send nie One Copy of the OFFICIAL K. C. Direct Reading Dial, weighs 5 AUTO -RADIO SERVICE MIANt'AL with FREE 48 pounds with batteries. Only 229.50 page Supplement. Send remittance in cheek or money Camden, N. J. order. Itett +ter letter If It contains cash or current,. Write RCA Parts Division, WE PAY POSTAGE.

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Please Say That You Saw It in RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935 441 rent increases the useful linear portion of the tube characteristic and greatly increa -es the power output. Naturally the transformers as- You C'N HAVE THE FILTHY gat sociated with such an arrangement must be LUCRE, BILL. HERE'S NEW correctly designed for the purpose. POWER WIRE It is well to point SOMETHING FAR MORE out here two things of WOUND RESISTORS importance. First: the tubes utilized in the INTERESTING TO power stage are the 45 type which are inexpen- ME!!! sive and economical in a class AB system. Sec- ond: Successful operation of a class AB amplifier requires a low -voltage regulation in both the plate and grid bias supplies. Regulation in the NEW -LOW PRICES. 10 plate supply has been brought to a negligible minimum by correct design and great care in Watt Unit now only 21 c net (0) manufacture of the transformers and chokes. NEW -Higher wattage ratings Use of the mercury vapor rectifier tube mini- smaller sizes. mizes regulation from this source. There re- NEW- Cement coating. Dura- mains only the one offender -the bias resistor ble- dissipates heat quickly. from filament center -tap to "B" minus. This NEW -A COMPLETE line - has been eliminated and a bias power supply Low Wattage, High Wattage. substituted Fixed and Adiustables, Higher in its place. It is important that the resistance limits. bias voltage on the power stage grids remain constant. NEW -IRC Power Wire The bias supply accomplishes this. Wound Resistor Catalog con- Inasmuch as the transformers and chokes in taining helpful resistance data both the amplifier and power supply are the and computation charts. Write very heart of an amplifying system, not enough for a copy today -Ask for RC- emphasis can be placed upon the importance of 100. correct design and care exercised in manufac- pa o00ó (a) Priers slightly higher in Canada. ture. The units utilized in this amplifier and INTERNATIONAL RESISTANCE CO. O 1 Arch Philadeyhia, Pa. power supply possess both of these necessary 2100 St. qualifications. Conservative ratings, high -grade O %V o.jal., (In Canada. 187 Duchess St.., materials. liberal use of insulating material, Toronto, rust.) high safety factor and great care in assembly make for a uniform. dependable, efficient, quality product of long life. All coils in these units are impregnated and baked under a vacuum: a special process which makes LIARESI5TOR5 them impervious to moisture and greatly minimizes the possibility of breakdown. and "on -off" power switch for the power supply As shown in Fig. 2. the high -voltage power is mounted on the front panels of the respective supply is comprised of a power transformer. a units. These panels are fastened to the boxes There's pep behind th'is type 83 mercury vapor rectifier tube and a dou- by means of tapped flanges which are an inte- ble- section filter. Choke input is utilized for gral part of the box. Two miniature handles HItH FIDELITY the excellent voltage regulation it provides. A known as "Footman's Loops" are fastened one bleeder resistor is shunted across the filter out- to each end of euch box. By the simple expe- Class "A " Prime Amplifier put to maintain the voltage, dient of fastening either a leather or woven - proper whether cloth the amplifier is turned 'on" or not. This belt to these loops the units can be easily is a moved about by merely slinging over measure of to protect the electro- the shoul- precaution der in portable work. The component parts of lytic filter condensers which might be sub- both units 4 STAGES jected are mounted on their respective wood to the peak voltage if no load were baseboards. This involves a minimum of assem- i 15 WATTS present. bly labor and facilitates removal of either unit The bias voltage power supply consists of a from the box as a complete assembly whenever transformer designed for this purpose, a type occasion might arise. 82 tube as a half -wave rectifier and a single Mounting choke with two filter condensers (condenser in- of the bleeder resistors in the power put) as supply is simple but very effective. The mount- filter. A suitable bleeder resistor is ing screws pass connected across the output through holes in the resistor of the filter. The lugs and down through pillars to the wood rectified grid currents of the power stage are a base board. Thus the resistor This remarkable high lpdrlSp very is free from Class "A" Prime P.A. Ampli- small percentage of the bleeder current so contact with the board and mounted quite rig- fier employ, tulwa except i,nallr that there is practically no change in bias idly. low in d yet itt an output of 15 watt, The Merlo Amdn u w, ru of the u may voltage with full power output. The result is a Onmd m ' Ì The of the a e ae "fixed bias" which is so essential. photographs two units show the adds factor.a lall-u reYd . e.,r. and The filament plan layout of the amplifier and location of the mouOi of the rectifier tube Is excited by a winding rhe arN .ama with, on component parts. It is recommended that this refuels rl..ÚV1 1° " 5' u d =u aa rl+am au ...Yds. = . the "B" power i . transformer. arrangement be followed closely as possible. rwM1e e:' Amplter has been developed Iy An idea of the efficiency can readily be gained I1 ""a reef., ... ,lt áaarlei .e d mammon. on Io52.v S.C. Attention is called to the manner in which the shied Ìnápprfaeninnre tender :di condition.. Ito ehnni. b nf rugged when it is realized that the total power con- ., ..d-Irni.liN in a lr nalul Murk e nekle tal-hike q input. output, and u,e.l ia ae e n: 1-57: I-ea: 1.I.15; r.e.1a, and 14Z9 sumed is less than 100 watts, at full power out- power transfer are provided lTubes for. is .41lPLI!'!l:'a-ro.nNelely a emMed. put. This accomplished by means of a plug a.eed and lesled. Inslabe,. " si 4e75 NET receptacle arrangement which has proved In cases where it is itself naker eavipmenf arallahle at siNe ., Complets dead. ern! desirable to mix more most satisfactory. The plugs mrely n than one channel have rubber caps into the amplifier a mixer ar- which extend along the cable and relieve stress MARL() PRODUCTS CO. e 16 Hudsen St. New Yak, N. Y. rangement can be used. Reference to the wir- from the connection when the cables are moved ing diagram. Fig. 2A, will show how this can be about. accomplished. The thought given to safety is readily appar- FULTONE V ent in the method used for bringing the power Mechanical line to the power supply unit. A recessed flush NEW FIVE -IN -THREE SET While economy has been a guiding factor in motor plug receptable is located on the box. the The power cord is connected to a body con- electrical design it is evident that this has nector 6 F1 not been neglected in the mechanical design. which fits into the recessed receptacle. The amplifier In the event that the power cord should be and power supply are each con- alive when the tained in their own sheet body connector is removed from steel boxes. Thickness the receptacle, there are no exposed 76 of the box material was determined with regard blades, thus eliminating the possibility of a short - to strength and weight. Louvres on three sides circuit or shock. provide adequate ventilation. The control equip- 12A7 ment such as volume control for the amplifier Conclusion AC-DC Underside view of amplifier It is believed the system described will fulfill a long -felt need in the public address field and its existence is more than justified by the de- A remarkable receiver - mand for an economical, efficient, reliable ampli- at a remarkable price! fier, with relatively high power output. Sensit ice- potrerful -ttnr Id -u ide elrle-c.i full ti te tube Pertortnann- rmnpa,i headphone .Neratloll -eny to operate-ea,) to build: .t revolver sou will be proud of!! Operating Data Complete kit, Including all necessary' parts, $ crystal finished metal chassis with all holes, 4 PLATE PI.ATE 8.-C. C. G and complete, easily followed Instructions- a TYPE VOLTS MA. VOLTS VOLTS Set t Sylvania Tubes 55_.20. Metal cabinet -$1.25 \'1 (57) 250 V. 2 ma. 100 V. spec/al loud speaker-$1.-15. 200 -6225 meter coils -5.25 V2 (57) 250 V. 7 ma. 250 V. SPECIAL COMBINATION V3 (4.i) 300 V. 36 ma. Complete kit, speaker. cabinet, tubes, anti V4 (43) broadead band coils -only iZa 300 V. 36 ma. -60 V. b it vo.. draine m ,rde d MdM. erasieed. Please Say That You Saw It in RADIO -CRAFT HARRISON RADIO CO., Dept. R -1- íai::v. .a74° 442 RADIO -CRAFT for JANUARY, 19 3 5

The above values are based upon no signaI through the amplifier. Read the next issue of Notes on Construction and Wiring (1) Keep all grid and plate leads separated much as possible. (2) Keep grid and plate leads from close PIRATE proximity to wires carrying alternating current (in this case, filament wires). STORIES wires should be (3) Filament twisted up to A Complete Book - Length Novel the socket terminals to keep radiated fields to a minimum. SKULL ISLAND (4) To undesired. eliminate possibility of M. spurious coupling bring all wires which return By C. BENNETT to ground, to a SINGLE COMMON GROUND A Story of Blood and Thrmde'r on the Main POINT. V. (5) Wire the power supply and input -output TREACHERY OF MOW GHEE receptacles to their proper places before placing Thrilling Story f (Mite-, Sea-Bandits the units in their respective boxes. This sri!'. By ELTON STERRETT provide for a finished job and eliminate ann. .- essary lengths of wire when the units are And placed in the boxes and the receptacles screwed SUBMARINE HOLD -UP into place. By LEROY LAKE (6) Under certain conditions depending upon A Story of Sea -Gangsters Who 'threaten the degree of coupling outside the amplifier box a Transatlantic Liner between input and output, it may be found ad- Yoe, .JEWELL. No. 214 visable to ground one side of the low imped- ancfoneed run h, ,,,du A specially drawn series of ,nd.ro 1,1.i r,.oume estinti ii.ar,. 14... 1ñe.nm. ance output and the primary center -tap of the mere cube-cbecke me Exploits of Modern Pirates °lord in,uuw.w a letter end imoradot .ppwr. input transformer. .1- Ile I,.::,I.r, ici the field of modrrni :i,p obsolete (7) Connect all transformer cores to ground. u!1 ,quiptunt. I'reelslon offers Its Po tensive A regular reader's department, men. - ores° f I..building Instruments to radio "Jolly Roger. Log," in which . rte h,r, derriupul plans fur rebuilding List of Parts your questions are answered. 1,. (...ter models. TRANSPOR1MERR AND CHOKES NOW AVAILABLE One Kenyon type KMG input transformer; Buy your copy of January One Kenyon type KAC high -impedance plate Pirate Stories now from any MODERNIZATIONS FOR choke; newsstand JEWELL No. 214 WESTON No. 676 One Kenyon type KR -45 driver transformer t JEWELL No. 533 WESTON No. 677 JEWELL No. 534 WESTON No. 678 One Kenyon type KR -462 output transformer; No. 678 The Cops JEWELL No. 535 SYLVANIA One Kenyon type KR -1 power transformer; 15e JEWELL No. 538 ARCTURUS No. 27 SYLVANIA No. 538 CECO No. 535 One Kenyon type K -45C bins transformer: DAYRAD No. 381 One Kenyon type KC -90 filter choke; One Kenyon type KC -350 filter choke; WRITE FOR OUR PLAN One Kenyon type KC -200 filter choke. ACCESSORIES "48" HOUR SERVICE One Kenyon amplifier baseboard; One Kenyon power supply baseboard; PRECISION APPARATUS CORPORATION One Kenyon amplifier panel; N. Y. Ave. Brooklyn. N. Y. Dept. RA. 821 E. One Kenyon amplifier container; One Kenyon power supply panel; One Kenyon power supply container; SERVICEMEN! Two 6-prong bakelite tube sockets; and Four 4 -prong bakelite tube sockets; Step Ahead of Ihr rank file- One Cornell -Dubilier or Aerovox dual con - with "CASE RECORDS denser. 8 -8 mf., 450 V.: The 'Little Red' of BROADCAST One Cornell- Dubilier or Arroyos dual filter RECEIVER REPAIRS" .amdenaer, 8 -8 mf.: In this one -room cottage at Saranac Lake, ADD 10.000 Hours to your Two Cornell -Dubilier or Aerovox filter con- N. Y., called "Little Red." the modern treat- experience! densers, 25 of., 35 V.: ment of tuberculosis began in 1885 because WORKORK N - Two Cornell -Dubilier or Aerovox filter con- Dr. E. L. Trudeau discovered the value of rest ICING! densers, 1 mf., 400 V.; in curing tuberculosis o o Progress has been DON'T YOUR PROFITSPAWAY! One Cornell -Dubilier or Aerovox condenser. made in the fight against tuberculosis, but it .5 -mf., 400 V.: still kills more persons between 15 and 45 work is alleatiV done and Vonr or e a co ordrd for you In "('ASE One Cornell -Dubilier Aerovox condenser. than any other disease Help conquer it IIEI'OR IDS." This 9812" .1 -mf., 400 V.; by using Christmas Seals on your holiday contains 1.500 haneeat' hinder Two metal clamps for 25 mf. condensera: letters and packages. a p,hahetirolly and mmcericslly Sri angel ' CASE RECORDS' One metal clamp for dual 4 -8 nit. condenser: of SI'Cl'ESSFI'I.LY COM- Five plate filter and "C" bins resistors: $4.75 PLETED SERVICE JOBS! s One Electrad bleeder 40 )'ASE RECORD tells all details for iiiotiory resistor. W.; l'a,I, for 1 ',nail. St l'l'LEMI:N'rED ,11'. %RTE1t1.Y FREE One Electrad bleeder resistor. 5 W.; cot. fus receiver make:. .:3.000 models. One tube shield, base and reap; ... for FASTEST Terhuluue knos'n to the lh'ofesshaA One Electrad volume control: Two screen -grid caps; CAPITOL RADIO RESEARCH LABORATORIES. INC. One knob for volume control: 1503 21st Street. N.W.. One face-plate for volume Washington. D.C. control: Two 7- contact power transfer plugs with rub - 1:, nIrlu rra: ciel RI:coItll$." landq formed full decals "l'.ISE her caps; The National, State and Local Tuberculosis Two 3- contact power transfer plugs with rub- Associations ber caps of the United States TWO 7- contact pourer transfer receptacles; sDDIIESS Two 3- contact power transfer receptacles; BUY CHRISTMAS SEALS Two 7- contact lower transfer receptacles; Two 3- contact power transfer receptacles; BIG RADIO VALUES One recessed flush motor plug receptacle; One body connector with armored cord boo gain in the newest grip; rad finest of 19:35 models! BUY One toggle switch with "on -off" plate; THE MAGAZINE OF SEX SCIENCE DIRECTAriU1,ine from u.. and SAVE UP One coil wire for wiring; SEXOLOGY. foremost educational -ex magazine, Is written 1935 Factory on the In simple language and Din be real by every member of TO 50°ír. prices One coil power transfer cable; the family. It io instruettte. enlisWentng-not a risqu. MODELS vonlidete lin:. every set guaranteed: One roll solder; book-contains no offensive matter. AC -DC midgets: world -wide all - Four handles; Contains 21 important article. no Set Science. 68 liai:i.. ear, farm and bat- "Ith attractive two -color rover. Here Ore a few of tie are: dual wave: consoles: One of miscellaneous tery models. Also 2. 6 and 32 volt. Beautiful package hardware. enure important articles: cabinets; illuminated airplane type Sex Incompatibility-9s Pregnancy Dan Brous in Women modern for- over 30?-'Neuralgia of the Sex Oro ns- 'Vagintsmus dials; separate short wave switch control; and Married LiloCircumcision among the Jews - Xeed eign reception bands marked; greater Men as Fathers -'Should I Be Cystosco WT.Sexual Life power and selectivity. From 1.91.19 of Athletes- 'Spurious Pregnancy -'The "Juvenator" Fraud -Malformations of the Male Or RADIO -CRAFT INDEX gan -Man Carries Twin In Tumor- 30 -DAY HOME TRIAL ñotlrl1,' AGENTS Female Breast Development- Protee rH\ÓLï11 Satisfaction guaranteed. Try' your Fordeo. MAKE By Subjects. Issues and Authors. the July Lion against Ignorance-,Mother at 1I any ' d:u'e° :m dans before Belding. Rend TODAY for MONEY 1929 to June 19:12 issues of RADIO -CRAFT are -Is Frigidity Inherited?- Gestation rór Openil" crow rrm'plete F REE Information! indexed and cross -indexed. in a publication you in Man and Animals -Extraordinary send "D may obtain for only 25e (stamps or rash). Sex Habits- Ouestiens and Answers. o FORDSON RADIO INC. .bo., Write n.af to us for this valuable 24 page reference; its use 'Article Illustrated. nett 5512. Darman fill.. Detroit, Mid. will save you time and money! SEXOLOGY. 95R Hudson St.. NEW YORK. N. Y RADIO -CRAFT for JANUARY, I 9 3 5 443 OPERATING NOTES CLASSIFIED i i ADVERTISEMENTS (Contiwted front page 41°1 Adrertisemenis il Isis ....lion a -oiled a the ii. noted all were 400 V. cartridge typo. ost of twelve root. per word for earb insert All contacts were put in order and ane. lait lais and :Mite.. each count a one rotor BANDSPREAD avis Cash should ;terminally all t-la.sltied ad- wipers cleaned, as per usual, and the set Played vertisement: note-- placed by a recognized fairly well, but seemed to be lacking in "pep" advert lane age ivy. No lest than ten words are in lieve "71P M epted. Advertl -ing for the Fdrru:n y. the audio output. This was due to the fart Issue should be received not later than Dec. 5. that the two fields had been so connected that they were bucking instead of aiding mutually. .!-CAM ERA Reversal of the 915 ohm section cured this W[[[ aYi LQJlL, Lu l.V1C a e A. C. GENERATOR trouble and the set worked fine, and has ever and since. You'll be amazed that such a trim small sat 10 PRACTICAL AND LOW -COST CHANGES JOIIN Mt'e :Nt.KN can give such performance! This two -tube converting Dodge 12 -V., Ford T, A.. Chevrolet Band Spread Portable Short Wave Receiver Delco 6 -V. generators into 100500 watt capacity brings in London, Berlin, Madrid and other A.C. generators. or into 32 -110 V., D.C. motor or foreign stations with an ordinary IS ft. in- generator. Dodge is 500-W. self- exciter. All in ATWATER KENT 188 sulated wire for an antenna! one book illustrated with complete simplified instructions and drawings for only $1. Autopower, I HAD an unusual case of an Atwater Kent ist You can take it any place for it weighs but 410 S. Hoyne Ate., Chicago. which had all the symptoms of a loose con- 9 lbs. complete with self- contained batteries. nection, that s, it would rattle when shaken. If you want short wave reception when the ELECTRICAL SUPPLIES or when the floor was jarred. Usual diagnosis rest of the family wants U.S. stations-just failed take it upstairs and tune in without bother- INSULATION, WIRE, VARNISHES. SUP- to reveal noisy tubes or loose connections. ing the others. Or put it in your car and PLIES. etc. Send 3c stamp for bulletin. Auto- Finally, on looking further, I found that mov- get short wave reception on your week -end power. 410 Hoyne Ave., Chicago. ing the control -grid lead to one of the screen - trip. grill would produce PATENT ATTORNEYS the noise. Sweating all Complete kit of connections on the R.F. coil and lead failed to arts $7.95, kit of PATENTS -REASONABLE TERMS. BOOK and remedy the trouble. At last, as an experiment, 2 tubes, add $1.44; advice free. 1.. F. Randolph, Dept. 562, Wash- I substituted a new wire which cleared up the kit of 6 batteries, ington. D.C. trouble. Careful examination of the old wire add $1.18; if want- failed show any ed wired, ready to PATENT INVENTIONS IS MY SPECIALTY to defects, to I put it back in use add $1.35. Coils through 28 year.: Sterling Buck, Registered place. The noise reappeared. Apparently the covering 19, 25, 31, Patent Attorney 7780. 629 F, Washington, D. C. rubber insulation of this wire must have tad a 40, 49, 80 and 160 (Free Bea,klet -R1. high content of sumo mineral which made it meter bands are conductive, as there were no broken strands in available at SSc RADIO the wire or breaks whatever. A new wire made each! NEW TUBELESS 1850 MILE RADIO. OPER- a permanent repair in this case! ates Speaker. Blueprint 17 Others. 25c Coin. BIG FREE CATALOG Setbuilders List Free. Modern Radiolabs, 151 -It 192 pages of amazing bargains. Over 50,000 Liberty. San Francisco. tams. Contains Great Specialized Section on ATWATER KENT 260 ihort Wave, including sets and kits from 2 RADIO INSTRUCTION ASHORT time ago there appeared in your o 10 tubes, Transceivers, Preselectors, Con- RADIO ENGINEERING. BROADCASTING. columns an article regarding a set erters, 5 M. Equipment, etc. Also sections from on Public Address, Replacement aviation and police radio, Servicing. Marine which they had to take the transformer and bake Parts, Tubes, and Morse Telegraphy taught thoroughly. All it in an Refrigerator Parts. Get your FREE copy of oven to show up the trouble. I am go- this amazing Bargain where expenses low. Catalog free. Dodge's Institute, ing to "go Book everything Pine St., Valparaiso, Indiana. them one better." I had a late model is listed at LOWEST WHOLESALE PRICES! Atwater Kent 260, which is the short -wave com- UNDERGROUND TREASURES bination, which we had to put in a refrigerator to make the trouble appear! TREASURE SEEKERS -MAKE YOUR OWN This machine performed normally in the store WHOLESALE RADIO SERVICE gold finders. Learn facts about mineral ma- before CO; chines. free outfits, etc. E. Dodenhofî, 11.1 E. it was sold. but upon being placed in the NEW YORK ATLANTA 2Sth St., New York City. t'Ur tamer s home, it would sometimes take from 100 Sloth A 4301KP..eMt..e St-M.W. Local Branch 219 Centre: Ave., Rework, New J 2 to 3 hours before the set would start tee DEPARTMENT operate after being turned on, although every C-Ii tinte I made a service call. the machine would ( ) Send nie the order for Band Spread Portable I have described in attached letter. perform normally. We brought it into the shop ( 1 Send me your FREE 192 P. Catalog with Bin and over a of 2 3 Short Wave Section. period or days the machine 1 BACK ISSUES failed to play sick. After questioning the own- 'NAME 1 er closely', we found that the only times the ma- ADDRESS chine failed to work was when they had been 1LCITY of RADIO -CRAFT away from home and the house had been cold STATE ..... _...... during the day. Finding this out. I put the which you might need to complete "bassi into a large Frigidaire and chilled it thoroughly, and it worked: that is, the set did your files, can still be had at the not work, which was what we were looking for! On checking through. I found a short in the price of 25c per copy. Send us first input A. F. Transformer. Upon remov- :tNn Nor your requirements, together with ing this I discovered that the case was very full of tar. so much an, that the tar was pushing your remittance in cheek or against the chassis. When pressure was re- leased, in other words, when WEBSTER the tar was cold. money order. it contracted and the short would appear. How- CHICAGO ever. when pressure was applied to the tar, the same as when the machine warned up the tar RADIO -CRAFT expanded. and the short would clear. I might (lard of Ilia.. ring mention that in 99 Hudson Street, New York, N.V. this model there is a plate resistor mounted on the inside of the transformer Systems case instead as had been former practice in the 141ROM "mike" to amplifier Atwater Kent. This was a little confusing at ... to first since a test did not indicate a Complet,. Lone, two of forty head -sets so short. that those in the audience who are know Thyself! "hard of hearing" may Well hear without Illustrated Titi n t II I v strain -that is the new WEBSTER - magaelue 1i. ai.o tout own doctor. tcIt.tT CROSLEY 30 -S, 31 -S, AND 34-S CHICAGO unit. AILS Vol'? Port' - in LAR MEDICINE tells THE trouble these models seems to be cen- It is called the Hard of Hearing sys- and a tered in the electrolytic condenser It i.e. -variable tem and is the newest WEBSTER- thoroughly. Written condenser assembly, and in the resistors. I find for You by donor+. CHICAGO PA in case of hunt the quickest method to locate the system to be designed Nontechnleai y e t to help you authoritative for all source of trouble is to put an 0 to 100 nra. mil - get all the PA business lsym ti. Many ana- liameter in series with in your community. tomical Illii tral!1)114. each lead to the electrolytic condenser. If the drain in any section is Special Offer! over 5 ma., the section or sections should be NEW BULLETINS Months $ replaced. I invariably find on these machines Ask for special bulletins and be sure which have been for 1 not serviced for some tinte that your name is on the list to receive the condenser bearings have worn to such an ex- the new Bulletins on co- ordinated Send 25e for sau tent that the plates are too close on one side, systems that are now PIe copy and find it a very good policy in many cases to being pre- POPULAR pared. MEDICINE put a pigtail on these models, as the friction 97MewHudson bearing is very hard to keep clean. A little care York, N. Y. in centering the condenser THE WEBSTER COMPANY plates will make a SS ;e West Lake On All New.etnd. (Cesali,uv,d on large 415) Street, Chicago, III. Please Say That You Saw It in RADIO -CRAFT 444 RADIO -CRAFT for .JANUARY, 1935 - - ahead of others In TUBE TESTER Value !INDIVIDUAL TIODE,TRIODE, ;PENTODE TEST_

COLORED ENGLISH READING SCALE Outstanding I 12 Features HIGH CURRENT SHUNT FOR FUTURE TUBES ENGLISH READING Scale COL - 1 ORED DIAL indicates "GOOD- POOR- -T" TESTS EVERY TYPE of tube made 2 to -day and many new ones which shall UNE. VOLTAGE arrive in the future. METER TESTS SHORTS and LEAKAGES W- O tween ANY TWO elements. NEON LIGHT indicates leakages above 4 1,000,000 ohms, SEPARATE LINE VOLTAGE meter 5' with line voltage control. INDIVIDUAL TESTS OF DIODE, AUTOMATIC SHORT 6 triode, pentode, etc., sections of all combination-type tubes -both plates of AND LEAKAGE all full -wave rectifiers. SWITCH ws-PROVIDES AGAINST OBSOLES- SWITCH CENCE -Spare switching capacity for LAMENT three times the present number of OR ALL TUBES tubes. SIMPLE TO OPERATE; convenient to The new, Model 304, Dependable Tube Tester establishes a new 8 use - "high" in equipment test to meet all modern requirements in testing. PROFESSIONAL APPEARANCE- etched panel; Simplicity in design and operation permit even the average con- 9 leatherette case. sumer, who knows very little about radio technicalities, to follow ACCURATE D'Arsonval moving -coil meter, guar- the testing procedure, and to accept without further question the anteed 2% accuracy. "good" or "bad" evaluation of every in tube the set. NO ADAPTERS of any kind necessary. Dependable Model 304 -100.135 volts: 50 -60 cycles 11 NET TO DEALERS ECONOMY -Costs less than other testers that do not have all these features. (25 cycle -42.25 extra) 12 KIT FORM In kit form - "to build 2,000 OHMS PER VOLT your own" Model 304 De- pendable Tube Tester with all instructions.- MULTITESTER N O DEAL- A high -quality test instru- R S . ment. The moving-coil in- S 65 strument sensitivity is 2,000 l0 ohms per volt. This instrument meets 4 major specifications. Ohm -meter range: MODEI. 304 14-ohm to 2 megs.; indi- Dependable Tube Tester vidual r an g e: 0 -2,000 also in Portable Model (o h m s) -0.2 ( -meg.) -2 (megs.), (batteries, - There is an important economy self factor in purchasing a Model 304 contained) . Voltmeter Dependable Tube Tester. The range: 0 -5 -50- 250 -750 V. instrument is capable of making Milliammeter 0 -50 all essential tests, and, because ranges: it is portable, may be taken from ma. Microampere range: store or laboratory and used on 0 -500. The automatic selec- KNOCK-DOWN outside service calls. In addition switch connects the meter KIT -Model 403K it has a handy compartment for tor Complete with in- small tools. only to the desired circuit struction, (less bat- and range. teries and case). NET TO $10,95 Combination Portable Carrying Case for Model 304 Net to Dealers .. .1495 DEALERS - illustrated - $2.25 additional.

WE ISSUE NO CATALOG ( All orders are F. O. B. New York. Terms: GRENPARK COMPANY A deposit of 20% is required with every I order. Balance may be paid on delivery. Deduct 2% if full amount is sent. 101 Hudson St. Dept. RC New York, N. Y.

Please Say That You Saw It in RADIO -CRAFT RADIO -C Rh FT for JANUARY, 1935 445 IMPROVE OPERATING NOTES Before You BUY Try (Continued from page 443) YOUR BUSINESS! big difference in the sensitivity of the machine. r BY KEEPING RADIOMIHDER In cases of low volume and low sensitivity. look YOUR NAME BEFORE for low voltages in the detector, A.F., and R.F. YOUR CUSTOMERS N stages. You will find on referring to the sche- T Novel. at tro. matic of these modela, that there is a pair of sun minder Ade:r'I P. A. Equipment advertisement pr i ill s. 11.000 -ohm resistors in parallel in the bleeder help radio usera remember circuit. In cases of low voltage, checking these favorite programs. ayl 5 DAYS are provided on both sides usually shows that they have dropped in resistance for recording programs. Eta - to about 6,000 ohms apiece. It is best ABSOLUTELY FREE lions. time and wavelength. in replacing these to use 5 W. resistors to pre- Permanently kept in tvery hone- -right near the radio vent recurrence of this trouble. -handy always. BUD engineers challenge you to duplicate Bud's sensational performance and proved depend- CARDS HELP ability at any price) BUD'S FREE FIVE -DAY TRIAL CUSTOMERS RADIOLAS 64, 46, ETC. AThen radio trouble -tarts. enables you to accept that challenge, with no or tubes go Imd, you will HUM level in these machines usually is high obligation to youl Write today for beautifully promptly be called to sr at lee and I find that a sure cure is an 8 mf. dry - the set. )'rolls are big when illustrated descriptive folder, prices, and full cad, B electrolytic condenser across the speaker field, ads x o placed in Purr details of FREE FIVE -DAY TRIAL offer. home. Trial A or from one side of the speaker field to ground: or der for cards avrpttd for and case the 66, the best results are from as little as in of the filament of the 80 to ground. However. a Radlominders with year little experimenting will show the best connec- PORTABLE SOUND SYSTEMS Ad o/ 5 Ltion Printed100 for 50 tion in the various models. 100 Each additional 100 -50c, 5.-Postpaid ELECTRO DYNAMIC UNITS 5t4 Card size 3'í x Dulles. Ad space 1 13 Inches. Printed attractively on heavy Golden Hod Bristol Card. l'se ink and handprint your copy and mail today with remits anre to TEST FOR "B" ELIMINATORS AND CARBON MICROPHONES ROTH PRESS. $25 Sutter Ave., Brooklyn, N.Y. POWER PACKS AMPLIFIERS HIS is a very simple hook -up, but since I have I never seen it in your columna. it might be of use to some one. Most any service bench has an 4, 5 & 6 FT. ALL ALUMINUM 0 to 100 or 0 to 50 ma. milliameter, and an 0 to TRUMPETS N OwSHORT WAVE SUPER 300 V. volt -meter, and usually in the junk box Continuous Band Spread is an old Clarostat or its equivalent. By :mount- FIELD EXCITERS With Preselector Stage Built in beat oscillator ing a jack so that upon plugging in your test leads the volt-meter is across the leads and AIR COLUMN HORNS Complete Kit for above including cum series 4 the milliammeter in with the Clarostat, you sets of coils. List B57.50 .Pe7sF -Net have a very useful test. You can vary the load LOW AND HIGH FREQUENCY Wired and laboratory and note the output of the unit and various tested, additional voltages. However, do not leave connected for UNITS FOR WIDE RANGE $ too long a period of time. as the variable re- THEATRE USE ALAN RADIO CORPORATION sistor will overheat badly at such a load. 172 Washington Si.. Dept. R. New York, I. N. Y. WM. HASSELL Western Office: 1028 So. Olive St.. Les Angeles. Cal. BUD SPEAKER COMPANY SHORT -WAVE INTERFERENCE Professional 1144 JACKSON STREET TOLEDO, OHIO, U.S.A. PERHAPS you will think this case of artificial P.A'. EQUIPMENT static interference sufficiently unusual to be of A complete and flexible line of high quality amplifiers general interest. The receiver concerned is used designed tor trouble proof dependable operation. in a store for short -wave reception and so is CONSULT LIS ON YOUR P.A. PROBLEMS especially sensitive to any electrical noise. Oc- Write for Free 1935 Catalog. casionally the slightest vibration. from shutting SIMPLEX ELECTRIC CO., Inc. doors, walking, and passing traffic, would set 100 Fifth Ave. N. Y. C. up a roar that seemed to indicate a loose con- FREE nection. Removal of the aerial stopped the and noise. However, the aerial proved to have no Radio faults in it. So a check was made for trouble Amplifier If you are interested in servicing electric in wall outlets and plugs. It was found that CATALOG refrigerators, write Gernsback Publica- when the walls had been painted with aluminum tions, Inc., 99 Hudson St., New York, paint the outlets had been included, and one of the plugs would occasionally make contact with I00 N. Y., for circulars on the Official Re- this paint. This would of course be extremely frigerator Service Manual. noisy. PAGES This is an example of one of the simpler OF BIG causes of noise, and of the ease with which it MONEY elAntazin Remelts iritk thews could be overlooked. It should be obvious that NOVEL 1 -TUBE ALL WAVE SET"! metallic paints are not suitable for use on SAVING Set completely assembled In cabinet --with tube, sin- electrical fixtures. gle earphone and tao rolls covering VALUES $10' WM. ROBERT MACDONALD, JR. band from 70 to 200 meters WW IThree extra rolls to rover band from 10 to 70 .nie and Rack and Panel, tao and AllWave Remelt -, meter. 50e. Ea. Re- IKIT less tube and cabinet and ,Cons ,. Call Svn a. placement 1` . and Aeeew,r sTa'- E at unbent with 2 colla $7.75 able Rock Bottons vr,cesl Single earphone 0.50 I R.C.A. VICTOR M -34 AWED ENOINEERIND INSTITUTE IWE ARE HEADQUARTERS FOR Park Place. Dept. R New York. N.Y. OVERALL IM PROVE RENTS PUBLIC ADDRESS SYSTEMS 98 Rawl as est -sa mil worked on several hundred r! - - IHAVE R.C.A. Buy Direct from the Manufac- model M -84 car radio receivers, not only in Profit MICROPHONES the field, but in the factory. and have found turer and Pay Only One and ACCESSORIES that this set may not be the jinx it was _ COAST TO COAST RADIO CORP. when first introduced; in my opinion, this set 123 -K W. 17th St., New York, N.Y. Unexcelled for Performance. has no peer when working at its best! .:... Utility and Economy) When first put on the market this receiver At roar Jobber was the last word in "auto radio." Today, SHURE BROTHERS COMPANY the same superheterodyne circuits with sev- Microphone Headquarters" eral changes in constants is used in the R.C.A. 215 W. HURON ST -, CHICAGO, U.S.A. Models M -105, and Portette M -116. These r changes can be incorporated in the R.C.A. M -34 with worthwhile results, such as better WET AND DRY ELECTROLYTIC THE ALL -ELECTRIC sensitivity, improved A.V.C. and noise sup- PAPER AND MICA CONDENSERS ALL -WAVE RECEIVER pression action, and better tone. RECOGNIZED FOR A completely elrclrixed SW r capable of (1) Replace R3 a 270 -ohm cathode re- SUPERIOR QUALITY td.wde cobs Uwe peei:lr circuit for sistor with an 80 -ohm, w. IN LI CLIMATES DIET .3 tuba 1a bumf. 37. vand 1723 trice % unit. THE WORLD OVER Natalia. ' twS. a.Jw -care. Ope.atn (2) Replace R9 (a 400,000 -ohm resistor ASK FOR honor soto BY LEADING Coils for 1o2ÓÓ )meurs and nructb,u Included. which is in series with the arm volume of JOBBERS EVERYWHERE CATALOG Comm Raepfi.a Guaranteed control) with 0.8 -meg. % -watt KIT $5.95 Wired. e.t.a $5.25 unit. OF EXTREMELY Broadcast ".da SOBS Aselums tube. 2.25 (8) See that the 376 mmf. condenser by- SOLAR MFG. CORP. ORDERS PILLED. PROMPT SHIPMENT TYPES C.O.D passing the hot heater prong to chassis in SVV BROoWAT COMPACT GLEN RADIO LASS.. Dept. Nee FOR SERVICE 473 Fearth Ave. New Yens, N. Y. (Continued on page 447) NEW TORO HANDY Please Say That You Saw It in RADIO -CRAFT 446 R A D O C R A F T , JANUAR'

----WELLWORTH TRADING CO., C0 ICnAt GO - -1 W. WESTINGHOUSE Electrical Portable Sprayer Outfit

I internal Mis POWER $ so I spray Con dencrib.dbe low, Supplied with, COMPLETE Pe 15OSle GENERATOR 2 I eye Formerly sold for $68.50 . MANUFACTURED FOR U. S. SIGNAL CORPS V

SPECIFICATIONS: Silo..? WAVE. TRANS:41MTka: supplying 110 Volts AC for operating 1V Flla; 117 -141_ Ibr. "Ham" transmitter. I HOUSING -Aluminum (Diameter - OPERATING 110 V. AC 60 CYCLE l;' in. Length -5% in.) RADIO RECEIVER in DC districts. s HAFT -2 3/16 in. (driving end) MOTOR GENERATOR. Diameter 9/16 in. the end is PUBLIC ADDRESS SYSTEMS. threaded for a distance of 14 ELECTRIC SIRENS on Motor boats, in.) Yachts, etc. Bass-Cast Iron (Length- 7% CAMP LIMITING. in. Height 1 P in. Width 4% SHORT WAVE nrtificial "fever" ap- in.) paratus. 6lounted on base with three OUTPUT -200 Watt 110 volts AC TELEVISION. ballbearing rollers. Shipping speed 4500 R.P.M.) I'ELTON WATF.RWIIEEL for lighting weight of complete outfit, STATORS-TWO pairs (two North or other purposes. 55 lbg. and two South) AIRPLANE: for lighting strong This le the Ideal outfit for all- around spraying work wherever current Is avalleble. atgroa -12 tooth inductor. or With this electric sprayer you can spray paint, varnIM, duro, enamel, lacquer, search lights electric signs. Insecticides. etc.. with speed. You can move it from one room to another with Build in commutator LABORATORY WORK. Rotor turns in halibenrings. ease. Simply insert plug into electric socket and this marvelous machine 1s ready Furthermore the following uses to do a man -size job-end do It efficiently. (GENERATORS NAVE NEVER SEEN USED) are This electric portable sprayer saves its cost over and over again on your own explained: work. it will make money for you doing lobs for others. How to obtain electrical power: Outfit equipped romplete with Internal Mix spray Gun. with quart aluminum from a Windmill, from available cup, which enables you to obtain round or fan 'pray, '. H.Y. heavy duty motor. Waterpower, from your Auto- 110 -volt, 80 -cycle AC, air filler. Kellogg Alt- Cooled Compressor. 1%:1%. 15 fret of hone. cord and plug. FREE mobile, from your Motorcycle, with gun, With each ' from your Bicycle. Foot pedals Price of complete outfit $27.50 ll'r at( aghousc or Banderol!: (tor transport- Pries of outfit without motor, $20.00 Generator we supply free of able Radio Transmitters, Strong charge a set of diagram -blue Floodlights, Advertising Signs 1 ; prints and instructions show- how to operate AC Radio sets Internal Mix Spray Gun ing twenty -five different uses, from 32 V. DC farm light sys- This Pressure Type Internal M it Spray Gun Is the giving technical information, tems; how to operate two gen- Finest Value on the Market. It Embodies the electrical Hookups and install- erators in series to get 2011 Seven Following Outstanding Features ing explanations. V. AC; how to obtain two phase 1. Hardened =tee] paint valve needle and nozzles, to We also include free of charge and three phase AC., etc.. etc. resist the rutting action of abrasives in paint. a set of four re ¡dart ut car- 2. Quart rapacity aluminum cup with concave bottom bon brushes. to resist high pres ure+ -very light and durable. C.,..rob,r as described 3. Alr control (shown on top of gun. just bark of the Acme Including four re- nozzle) gives fustantaneou= control over the "wet- placement carbon brushes $'90 ness" of rma. THERE ARE OVER mid folder containing In- 4. Positive material control (shown at back of gun. tructions and uses ...... _... above handle). S. New type construction of cup cover allows instant APPLICATIONS Naicrdu wriuhl 18 Wu removal for cleaning or for attaching a paint hose to the gun. r Ito Mart out ut , n'born ben.. ara boualrr 25 SOME OF WHICH ARE: C. Latest type handle-"flts the hand." spare lr $I.LO prr art of four. A.O. T. Two -finger trigger. DYNAMO lighting from eight of Dix l,vrrlion. bought erpor`. In this got the material is forced up to the nozzle to ten 20 Watt 110 Volts lamps. c 1. ooI under pressure. properly mixed within the nozzle and h. charged, perfectly of onrizeit. in a fan - shaped spray Shipping $ ,': to 12 Inches vide. One hardened steel nozzle for 750 G. E. Phonograph Motor round spray also !twiddled vi th run. J lbs. Variable speed induction type self - is tarting, 110 volt. 60 cycle, AC, with Filter Tank lever control. Speed range from 5 Complete with tank, gauge and 601b. safety valve to 200 RPM. Can be Compressed air filter and expansion tank, equipped with gauge and s. focs valve. installed in place of Has standard taps in tank and base ieady to in,tall. Eliminates oil and moisture. old- fashioned, hand - winding speed motar. time as illustrated In Electric Portable Sprayer Outfit shown above. Also ideal for display cG; ppiny refight 8 lbs. turn table, and a hundred other uses. These G.E. Electric Motors are brand Kellogg Air -Cooled Compressors new, in original factory cartons. Same motor that for - at less than half price I merly sold for 815.00 S 395 same as illustrated In Eleetrie Portable Sprayer Outfit shown above. only Maximum Motor Complete with speed regulator (not shown Sire Pressure Speed Required Price in abuse Ph Ode,. Formerly Sold for si ;,at 1% x 1% 75 lbs. 600 %1 H.P *7.60 tfg x 2 100 lbs. 600 Ye H.P 9.00 2 x 2 125 lbs. 600 1/3 H.P 10.50 214 x 2 176 lbs. 500 1/3 H.P 12.50 ORDER FROM THIS PAGE Shipping weight, if, 1J, 14, and 18 fba. Since We Do Not Publish Any Catalog Remit by check or money order for full amount of each item- - shipped by express collect, if no money for P.P. enclosed. No. C.O.D. order accepted. Money refunded if not satisfied. lie sure to stilt, G. E. MOTORS shipping point if express Or freight office is not in your town. These Motors were manufactured by the General Electric Company and of iginalb intended for use by large WELLWORTH TRADING CO. RC -135 manufacturing conpaa'. 560 West Blvd., Chicago, III. livre are the spe,llitatlons: 1'30 Washington It.p. -4800 R.P.M. UnIret.51 . 5.1'. and D.C. 110 volts instant re, er -e. Size: I which please Diameter 3 Inch, length I inch. Ship, enclose $ for send me the ping weight, 3 lbs. Add 25c ter spe- following: cial packing and mail. in, anywhere In U.S.A. $245 WHILE THEY LAST. EACH Original Price $12.01) Name All Merchandise Offered On This Page Address City State Is Absolutely New and Unused

Pleure Soy Thot 1 -o1( Sato It DI RADIO -CRAFT RADIO -CRAFT for JANUARY, 1935 447

Index to Advertisers OPERATING NOTES (r ,.r;.,,,,..1 ¡JO., ,.a,,, n5i glewRADOLEK A the power converter is connected directly from Alan Radio Corp. 4:39, 445 the hot heater prong of the first R.F. type 78 Allied Engineering Institute 443 Allied Radio Corp. 440 tube. American Red Cross _..... -. 138 (4) Replace the 89 output pentode with a 41 tube, and replace R11 (a 1000 -ohm cath- B ode resistor) with a 500-ohm. 2 -watt unit. 431 1935 Baltimore Radio Corp.. -- .._.... -.. (5) Replace T2, the input transformer. (part J. Matheson Bell - 426 Blan the Radio Man, Inc. 436 No. 6488) with a higher -ratio unit (such as Bud Speaker Company 443 part No. 6732). Burgess Battery Company 121 (6) Replace RIO (a 60.000-ohm resistor Burstein- Applel.ee Company 434 shunting the audio frequency transformer) C with an 0.2 5 -meg. unit. Capitol Radio Engineering Institute 43 (7) Remove the trimmer adjustment plate 148 Capitol Radio Research Labs. 442 on the bottom of case to relieve hack pres- Central Radio Laboratories 430 sure. or drill S half -inch holes in the center Classified Section 443 of the top of the case. PAGE 445 Coast -to -Coast Radio Corp. (8) Replace Rfi (a 500,000 -ohm in the 6117 Columbia Sound System, Inc. 428 Cornell -Dubilier Corp. 424 control -grid circuit return lead) with an 0.3- Cornish Wire Company 417 meg., '_-watt unit. CATA LOG Coyne Electrical School 3,5 Worthwhile results will be obtained only when all these changes are carried as speci- 429, 430, 436 fied, due to the fact that partial changes will c9a 1tGsv- lea Tobe Deutschmonn Corp.lr not show the improvement that is possible E when all the specified changes are made. Knorr What You Are Baying Eilen Radio Laboratories LEO J. DBAUS. Radolek's 1935 Radio Profit Guide Electrad, Inc. -..- 4 -'' accurately describes every piece of mer- Electrical Laboratories Co.. Inc. 447 chandise required in Radio Service. Radolek's examines F VICTOR R -32 Engineering Staff Fordson Radio Mfg. Co. every new item! These technicians write Freed Radio Company 42!1 AN UNUSUAL trouble was experienced the descriptions published in the Radolek Guide. When you merchan- a of model. and one which I'rofit choose with set this dise from this big catalog. you are assured General Transformer Corp. _ - _.... 437 gave the writer and his partner quite a bit of reading an accurate description 444 of Grenpark Company - - . - of trouble in finding the cure. Upon looking what the item consists and what purpose H over the set, the 80 socket was seen to be it serves! Hammarlund Mfg. Company ._ __.... -.. 429 burned to charcoal from no apparent cause. Lowest Prices! Our Engineers: com- Harrison Radio Company 441 Upon replacing it with a standard wafer socket. pare Radolek's merchandise with compe- Corp. 427 are Hygrade -Sylvania the SO was found to be passing a "terribly tition. Our prices determined by com- I parative quality and are equal to or lower high current and the rest of the tubes getting on any quality items America 4213 than prices similar Insuline Corp. of -..- almost no voltage at all. The condensers. re- offered by other distributors of fresh. new International Resistance Co. -...._ 441 sistors, tubes, and in fact everything else merchandise. Whenever market prices a re K checked O.K. Finally in order to localize the reduced. you will always receive the bene- Kato Engineering Company ._....- .... - 439 trouble, various feeder lines to the different fit of these new lower prices. 424 Kenyon Transformer Co., Inc. - circuits were disconnected. one at a time. until Radolek protects your interests by re- L it was found that the lead troni one of the stricting distribution of the Radolek Prof- if it Guide to active and legitimate Radio I.eotone Radio Company - 431 45 socket's plate terminal to the output trans- Inc. 431 accounts. Full cooperation is extended to Arthur H. Lynch, former was disconnected, the voltages jumped Radio Dealers and Servire Associations to M to normal and the current of the 80 dropped restrict wholesale prices to the Trade only. McGraw -Hill Book Company 436 to a little less than normal. It was found Secure Greater Radio Profits! Send Marto Products Company 141 that this 45 socket was leaking badly to the for your copy of the 1935 Radio Profit School 429 Ise Massachusetts Radio chassis so it was replaced and the set re- Guide! I your letterhead or card. Just Matthews Radio Company 428 out -the Radolek Broadcaster. A 16 page Midwest Radio Corp. Back Coter turned O.K. bulletin of ideas, new merchandise, and Miles Reproducer Company 431 In about two months another call came in valuable information. Ask for it. N on this same set and the SO socket was found as before. al- The Radolek Co. National Company 433 to be in the sanie condition National Radio Institute 387 though the other sockets were O.K.! The 579 West Randolph Street National Tuberculosis Association 442 RO socket was replaced this time with an old Chicago, Illinois National Union Radio Corp. .139 type having over r -in. between the plate P terminals, and a heavy bakelite base. As Pioneer Sound Laboratories ...... _...... __ 429 there is a potential between 6011 and 800 V. Popular Book Corp. 434 across the plates of this tube and there i- 443 Popular Medicine only about ¡,; -in. between the terminals on maP Postal Radio Corp. 43S some wafer sockets. the writer came to the Precision Instrument Corp. - ...._.._ tb\s. conclusion that a film of dust and dampness Get R possibly started the trouble, in the narrow ...... 424 Radio Circular Company - ...._ gap. This conclusion was strengthened by City Products Company 43 Jr Radio the fact that the set has been operating satis- Radio Equipment Corp. 434 .otenni.t,,ett Radio Publications 424 factorily ever since. R<..dpe;. Radio Trading Company 448 i \t 389 \to"é í°t vvige ee Radolek Company .. 447 onan\ 431 258 oKa\\ boaoo RCA Institutes. Inc. GENERAL MOTORS \ ot\ <'`aot. 440 RCA -Victor Co., Inc. was Va`YS\1.. ae

)w ? TERMS r The STAR- ¡, Send money';¡, r RED () : order. certi- items on this a r page are o1 limited aven. stEmps. C.O. - I : áN tti ty and r: D. shipments "+a;i lr`t. ;: = I ente are : , onlyi if 20b A:; special I y re ttaneaar--r; tFr. '%'s:¡ priced. Once n companiesmpanies fj w ,, "1cf. sold out they . If sent tt,}¡: tan never; , TIIINK It a dio be eb- post pineeel':.-: again IédeïlA' m triced at ans x-. !(t--r;.. * OF IT! cul era a in cot price. Don't hssues:efundad.; , delay, order ' s: - sound movies ------all in gour to -day! "i..'ti.:vi`: s Electric recordings ou n hume: More than 8350 worth graph--Largee t- - ,nn- of cntertai omen, for i only sole a dio ami :rA 852.95. That 's value sneaker-all this is o f Ithmt prere,lent. Sy, fer you In a shnglefull-i bled talking tnorlot sized Kennlne walnut -Modern ''Iry trie Idlono- "Millet for only 582.95.

Dendrite Radio Jiodel 720 and Short Wave Analyzer Treatise Flexible Point -to 108 Pages Point Tester 1500 I llus. Enclose fi v e tents (coin) for Tests ALL Latest postage. Treatise Type Tube Circuits sent by return Requires minimum manipulation. is extremely mail. Print name tit%il.lr and so arranged that voltage and , and address clear- rent can he measured in any tube circuit. 1te- ly on request. -i muscs. continuities and calmc Ries are also Completely reels d and enlarged, this new nuiek¡y measured. 1935 edition contains 108 solid pages of use- Point-Pi-point lest: are made throne]] an A ful radio information. diagrams. illustrations. oudu, nor cable and plug ...tied to the s, -t Designed radio kinks and red live radio merchandise. ket . Tuben used: for 110 volts PARTIAL LIST OF CONTENTS: Funda- lias oneo AC ami one DC meter. Rugged . -57:3.06'x: 50/50 cy- mental Principles of Radio for the Beginner. simple. and accurate in use. The 1W cles A.C. I -82 rectifier. In- Chapter 2 - -- fundamental Circuits and l'ses scale: arc 15. 150. 300 and sitio volts, 15 and 20 -Watts of un- put -grid of of New Tubes Revamping Six -Volt Batten, 150 milliamperes. The AC scales are 10, 25. distorted 57; Output Sets for Tsin -Vont Tubes ami power. - -Public Address l'a, :ytl volts. Ship. ist. 11 111:. 4000 ohms. Systems -flow to Build Short -Wave Trans- Ns. 720 Readrite * Class B" Amplifier Kit mitters and Re- Pointto -Point Set Analyzer. ce i v e ti-to- Mere Is a splendid opportunity to tom a real. professional amplifier at n -I YOUR PRICE .. cnbslrnrxl saline! There are only 20 of these kits available at this Date Tube Chart nul Socket Con - price. First come, first served! No. 11K :N) Walt Amplifier Kit. nertions, etc. , Ir.

Please Soy That You Saw It in RADIO -CRAFT NOW READY

Official Air Conditioning Service Manual

A GOLDEN OPPORTUNITY FOR ALERT MEN IN THE NEXT GREAT INDUSTRY

THE idea of electricians, radio service men and other mechanically in- clined men servicing Air Conditioning and Refrigeration Units is self - evident and the thought has occurred to some untold thousands ever since air conditioning equipment has been installed in auditoriums, theatres, public ''^` . studios, department stores, office buildings and manufacturing plants. The tremendously broad possibilities in this new industry are hound to give OFFICIAL employment and success to men far -sighted enough to see its advancement and development. We quote an excerpt from Mr. Hugo Gernsback's editorial which appeared in a recent issue of Everyday Science and Mechanics: AIR CONDITIONING SERVICE MANUAL "I advise young and progressive men to go into the air. conditioning business during the nest Jew years; because this, without a doubt, is the coming industry in this country. Thousands of small firms will spring up, undertaking NOW to air -condition private houses, small business offices, factories, etc. lVe are not going to tear down every building $5.00 in the United States immediately. It will be a gradual growth; yet small installation firms will air-condition small houses, and even single offices in small buildings." A COPY

This is only partial proof of the certain success of this new field. Further assurance is that engineering schools have already added many important courses on air conditioning to their regular curriculum. Architects and building contractors are giving considerable thought to installation of this equipment in structures which are now being planned and built. The beginning of this business will probably he similar to the auto and radio industry, but in a few short years it will surpass these two great fields. The OFFICIAL AIR CONDITIONING SERVICE MANUAL is edited by L. K. Wright, an expert and a leading authority on air conditioning and refrigeration. He is a member of the American Society of Refrigerating Engineers. American Society of Mechanical Engineers. National Association of Practical Refrigerating Engineers; also author of the OFFICIAL RE- FRIGERATION SERVICE MANUAL and other volumes. In this Air Conditioning Service Manual nearly every page is illustrated: 352 Pages every modern installation and individual part carefully explained: diagrams furnished of all known equipment; special rare given to the servicing and installation end. The tools needed are illustrated and explained; there are Over 600 Illustrations plenty of charts and page after page of service data. Remember there is a big opportunity in this new field and plenty of 9" x 12" in Size money to he made in the servicing end. There are thousands of firms selling installations and parts every day and this equipment must he cared for frequently. Eventually air conditioning systems will be as common as Flexible, Loose Leaf radios and refrigerators in homes. offices and industrial plants. Why not start now -increase your earnings with a full- or spare -time service business. Leatherette Cover Here are some of the chapter heads of the AIR CONDITIONING SERVICE MANUAL:

CONTENTS IN BRIEF M A I L C O U P O N TODAY! History of Air Conditioning: Fundamental Laws: Methods of Refrigera- tion; Ejector System of Refrigeration; Compression system of Refrigeration; Refrigerants; Lubricating Oils: Liquid Throttle Devices; Servicing Ex- GERNSBACK PUBLICATIONS Dept. R( -135 pansion and Float Valves; Servicing Refrigerating Systems; Control De- 99 Hudson Street, New York, N. Y. vices; Thermodynamics of Air Conditioning: Weather in the United States; Gentlemen: Enclosed you will find my remittance of Five Dollars The Field of Air Conditioning: Insulating Materials; Heat Transmission for which you are to send me One Copy of the OFFICIAL AIR Through Walls: Complete Air Conditioning Systems; Estimating Require- CONDITIONING SERVICE MANUAL, POSTAGE PREPAID. ments for the Home, Small Store, Restaurant: Layout of Duct Systems; Starting Up a System: Operating and Servicing Air Conditioning Systems: Air Filtration. Ventilating and Noise Eliminating Devices: Portable Electric Name Humidifiers and Room Coolers: Automatic Humidifiers: Air Conditioning Units for Radiator Systems and Warm Air Systems: Central Conditioning Units. etc. Address

GERNSBACK PUBLICATIONS, INC. City State (Send remittance in form of check, money order or unused U. S 99 Hudson Street New Yoik, N. Y. Postage Stamps. Register letter if it contains stamps or currency.) 1

SAW- *< 507 bi/ BUYING YOUR RADIO 21 the A MIDWtST LABORATORI1S 7hri/ito ÿunrnateed World-Wick 411611 II DIE ITY Perfoimunce with 7h/ 74mA7New 1935 MI DW-EST Fi-41 SUPIR Deluxe ELAliW7AVIRadio ! ( AI L WAVE BANDS ) fI;,0 IRE s ' ^ ONLY RADIO COVE-RING F1 9 TO 2,400 MST -ERS. R) 64¡ /2.000 A TUN/NG RANGE

WORLD'S-- GRIAT.ST RADIO VALUE-

-; "` " / with New Deluxe Auditorium -Type SPIA h -R 1,4,1 TOSSI ,

30 Days tt Trial 1 BEFORE you buy any radio write for the new FREE 1935 Midwest "Fifteenth Anniversary" catalog and see for yourself the many reasons why 110,000 satisfied customers bought their radios direct from the Midwest Laboratories and saved u.t from ¡3 to!/. Why pay more than the direct -to-you laboratory price? world-W You, too, can make a positive saving of from 30% to 50% by buying M iddf.- this more economical way. Learn why Midwest outperforms sets cost- Here so so of ing up to 5200.00 and more. Never before much radio for little them.t.- money! Midwest gives you triple protection with: One -Year Guar- tion,f h antee, Foreign Reception Guarantee, Money -Back Guarantee. heard Only Midwest Gives You Multi -Function Dial EAQ,M.- in keeping with drid, This dial was designed ADVANCED 1935 FEATURES equalled world -wide broadcasts... of the times, yet is not an airplane 50 Spain - the trend Many exclusive features include: England, France, Germany, Spain, DJB, Zee,eu. U.rm,.nr- dial! It is a many -purpose dial that per- Italy, Russia, Australia, etc. Send GSB,GSF, Daventry, Ens- - M icro-Tenuator... Fidel -A- Stat... Innd -VH3M E, Melhoume, forms many functions. Now, Midwest guar today for money- saving Australia- 1i K2ME, Syd- Audio Generator...Cera- facts! ney. antees that inexperienced persons can se- Separate Australis- HJ2ABA. mic Coil Forms, etc. Only Mid- 11J4A BE. 11J3ABF, Co- cure good foreign reception. Send for FREE SENSATIONAL HIGH FIDELITY RECEPTION lombia, S. A.. and many a tuning range of 9 to Golden Hatfield. miniature of actual rotating dial which west covers This bigger. better, more powerful. clearer - (33 Megacycles to 125 super 2202 Grand Avenu.. clearly shows these outstanding advantages: 2400 meters toned. selective. I6 -tube radio gives enabling you to easily and you absolute realism-assures you of life- Praises Dial calibrated In Kilocycles. Megacycle. KC)- anything Perna so I. in even low - like. crystal -clear tone -unlike y se .;en Reception and Meters; successfully tune you have ever experienced before. You will Limn, 2. Call lettersof American Broadcast Stations powered foreign stations up to hear one more octave- overtones -that Peru - printed on dial and illuminated; 12,000 miles away with crystal- cannot be brought in with ordinary ra- we have Slow Smooth -Acting Tuning; dios. Now, hear every beard the 3. -Fast, -speaker reception. five e. Station Group Locator; clear, loud instrument, every 5. Simplified Tuning Guide Lights; voice, every shade and with your AU 5 Wave Bands enable you to inflection of speech. 6. Automatic Select -O -Band Indicator; hlidwnt. Pointer Indicator; enjoy today's finest High Fidelity Have 7. Illuminated programs. In addition, - 8. Silent Shadow Tuning-Improvement on American Take advantage of `M didagas- Meter Tuning; you get Canadian,police,amateur, the amazing 30- Sydney. London Pasriienna. 9. Centralized Tuning. Vr. Moscow. Madrid. commercial, airplane and ship day FREE trial New York. Shanghai. Tokio derive new delight and also South American Now Style Consoles broadcasts and offer. Send for transmitters. Maraui. H. The Midwest 36- and new excitement from un- FREE catalog. Buchanan, Apartado 96. Plaza Sal4 Martin, 171. page catalog pic- LABORAIOR1ES tures a complete DEAL DIREti WITH Increasing costs are sure to result in higher FOR! line of beautiful, ar- radio prices soon. Buy before the big ad- tistic de luxe con- vance..NOW...whde you can take advan- AMAZING 30.DAY FILL TRIAL' in tage of Midwest's sensational values...no sole and chassis middlemen's profits to pay. You can order OIEER A' D RIM 1935 CATALOG colors. Write four your 1935 High Fidelity radio from the new MICtsT RAJI'1 COSY., User -Agents with as much certainty of for new FREE Midwest catalog Dept. sag Make Easy satisfaction as if you were to select it in our Extra Mang catalog today! great radio laboratories. You save 30% to fo Cincinnati. Ohio. Midwest lung-range 50% when ou buy tins popular y...you get 30 days Without obligation on my part send Cheek Hero FREE d.treTS- radios FREE trial.. as II as $5.00 down puts a Mid- me for Satisfaction FREEWM west radio in your home. guaranteed plete details of your liberal 30ów Details Write new FREE catalog today. an ord r. low as .. or money back. for FREE trial offer. This is NOT MIDW-EST RADIO CORP. Narrt Address DEPT. 8 4 9 - CINCINNATI, OHIO, U. S. A. All Codes Town statt.._ Established 1920 Cable Address Miraco s.