"550 on Your Dial"!

THE IRON HORSE GOES ON RECORD! See Page 264

RADIO POSTMISTRESS

"550 ON YOUR DIAL"!

"PHANTOM RAIDERS"

F.M. RADIOS TELEVISION SERVICING PROBLEMS SERVICING 2-TUBE SUPERHET. RECORDING AMPLIFIER ELECTRIFIED NEW S. S. AMERICA'S RADII AMPfRITfJngìuj the B/GGl5790Y901f ía the 4iiwith Júzce iu JnceptlQie

!t GRADIENT IJYflhlmic

UNI- DIRECTIONAL. NEW SUPERIOR ELIPSOID PICKUP PATTERN ELIMINATES FEEDBACK A TROUBLE BECAUSE IT HAS LOWEST ELIPSOID FEEDBACK POINT PICKUP OF ALL DIAPHRAGM PATTERN TYPE MICROPHONES FLAT RESPONSE. FREE FROM ANNOYING PEAKS, GIVING STUDIO ¡Po moo X0000 -QUALITY REPRODUCTION. FIAT RESPONSE The Of PG DYNAMIC P.G. diaphragm follows air particle velocity where amplitude is a GRADIENT of the PRESSURE. dynamics In ordinary amplitude is restricted from following air particle velocity. J The P.G. DYNAMIC is a radical improvement in this type of microphone. according to modern You can actually hear the difference. Case is acoustic principles. Rugged, not affected by temperature, designed OUTPUT, -55 DB. altitude or humidity. HAS UNUSUALLY HIGH MODEL PGH (PGL. 200 ohms). Excellent for high fidelity P.A. installations, switch. cable connector, 25' cable. broadcast studio, and professional recording. With Chrome finish. LIST $32.00 ( 40. 10000 MODEL PGAH (PGAL. C.P.S. ) 200 ohms). For speech and music. 70 -8000 C.P.S. Switch, cable connector, 12' cable. Chrome. LIST $25.00 IsumoINAIIUN VELOCITY- DYNAMIC AMPERITE ACHIEVED WITH KONTAK MIKE ACOUSTIC COMPENSATOR Puts Musical Instruments Across An exclusive Amperite feature: By mov- ing up the Acoustic Compensator you AMPERITE change the AMPERITE VELOCITY to a DYNAMIC microphone without peaks. At the same time you reduce the back pickup, making the microphone practically UNI- DIRECTIONAL. k;:11311 So beautiful is the tone produced with the Kontak WITH ACOUSTIC COMPENSATOR: Mike, that it was used in the Philadelphia Symphony MODEL RBHk; RBMk (200 ohms) with to amplify a mandolin solo. Gives excellent results switch, cable connector. with any amplifier, radio sets, and record players. Chrome, LIST $42.00 MODEL SKH (hi -imp) LIST $12.00 MODEL RSHk; RBSk (200 ohms). Switch, KKH, with hand volume control LIST 18.00 cable Plug connector, Acoustic Compensator. extra List 1.50 Chrome or Gunmetal. LIST $32.00 FOOT PEDAL, for making beautiful crescendos LIST 12.00 WRITE FOR FREE SALES AIDS AMPERITE rAMPER/TE561 BROADWAY, N. Y. U.S.A. TRY, MARY, (-BILL, YOU'RE ALWAYS 1LL TAKE IT FOOLING WITH RA01O -- I'LL HOME TONIGHT OUR SET WON'T WORK -- WILL. You FIX IT T,

l V 1 BILL.\ SAY- WHERE IVE BEEN STUDYING RADIO AT HOME, HELLO JOE- N.NHERE'vE YOU DID YOU LEARN +IELLO. BILL- GOT A WITH THE NATIONAL RADIO INSTITUTE. l FIND OUT t TH PRTESTT ITS CANT YOU BEEN LATELY- TD TAKE THEIRCOURSE.. IVE GoT . ,TOUGH ONE OUGHT WRONG A A GOOD ONE WHAT'S AND WHERE 'DID YOU RADIO JOB NOW. LETS MAKE A TO FIX? A GOOD GUESS I'LL MA1

AVIATION RADIO, POLICE (` THIS THEIR ADS 11 M CONVINCED NOW THAT RA010, TELEVISION, IN THE I VE SEEN r GET A JOB NERFS THE TROUBLEBILL, I IS AND OR CONTROLS - BUT I NEVER THOUGHT COURSE 'PRACTICAL ELECTRONIC FIRST I.F, AMPLIFICATION STAGE. I NOW JWITH A RADIO COULD LEARN RADIO AT \ COMPLETE. l LL ENROLL RADIO IS SURELY GOING THAT TEST EVEN BEFORE BROADCASTING OR LEARNED HOME --I'LL 'PLACES. AND THE I STARTED TAKING THE COURSE, TRANSMITTING IN A MAIL THEIR NATIONAL RADIO amt.. IT'S DESCRIBED AND THEN I CAN MAKE STATION COUPON RIGHT INSTITUTE HAS TRAINED TREE LESSON WtttCH THE REAL MONEY FIXING INSTITUTE AWA HUNDREDS OF MEN NATIONAL RADIO RADIO SETS 1. WHEN r TOR JOBS IN RADIO SENDS YOU YOU MAIL A / COUPON FROM OR INSTALL AvD M 1 1 ¡ ONE OF THEIR ADS LOUD 5?tA .E0. SYSTE$ \ / I -_,lt . ' t.-- // , \ ; n' 15 KNOW THANKS: 11 CERTAINLY \ YOU CStTA.N Y THE A4 EASY TO LEARN RADIO Moro. SOunOS ONLY DAY WAY. l STARTED 0000 AS THE NR.1 AND l'M _1000GNT ITS / A FEW MONTHS ASO, ALREADY MAKING COOP MONEY. Lesson on THIS TIME I will send you a SPARE WORK IS GREAT )J FUN AND T 11 Tips FREE if PRETTY SOON ' Radio Servicing I'LL BE READY IT IS FOR A FULL TO SHOW HOW PRACTICAL TIME J09 TO TRAIN AT HOME FOR GOOD JOBS IN RADIO

equipment; ohm, ; J. E. SMITH, President OUR WORRIES ARE OVER. 1 R.Litn I'M SO Clip the coupon and mail it. t. m.lmt eaD.rinvnt;. Muhl National Radio Institute OH BILL- . I HAVE A GOOD JOB 1 in YOU .110 t .. l you t I ; n : ^ : d makes knn ú. I ASKED ' 1 = . years GLAD certain I can train Established 25 NOw, AND THERE'S A to be a Radio 'FecI,- I i i . n 'n,C. taslnatiur,, practical. Fl% OUR RADIO. your spare time Tests esehislr- 'ro FUTURE AHEAD I ' In L..ou a Ih,!: , tl. , BIG that I will send you ,ample ,heile lia 1 It GOT YOU STARTED niclen to :unl , 'frlrl-inn Dlcd.o it. recul it. see ly Tr'..l.,.i. 1 6' FOR US IN lesson free. Examine mc:d.,:: tle :in_, ,, _ t r ,. THINKING ABOUT , i lta how and easy it is understand. In I AS A CAREER, RADIO clear to help RADIO See how my course is Planned AND NOW YOU RE a good job in Italia, a young. TY You get GoING AHEI field scith . fol ore. Y.,. You .-.) or So FAST ne edn't give up your 'Pre,erlt job. Get This to become upend a ot of money Professional Radio Technician. I train you at li. ni' in your spare time. Servicing Jobs Like These Go to Men Instrument Who Know Radio .. Radio hrs., I.,+t , _ T operator- u 1,-,us TI,'- . Met nt Make; PT. I an ds nay' ell. lt, I 1 111,1 npua yIlol, u ' Ploy /asters. nope,;- r , huh 't,..k.tim, ud t. 1, h.iL. toad -Day :ohs ith II It t I,.. , rd , Ih. 1r.t 1 .1 I RA. 11, p t . 1 I : , call, ttment. r .,II 1 President. Dept. OM% I I E. SMITH. t 1 ll N.111 nnl D. C. ploy Intl t tt t tth iv, National Radio Institute. Washington. open their 0, P , Technic; n : I molt band F'ItF:I:. t ithout obligation. our Sample Lesion repair h ,' I t. x ', I I inn V >Ir n ¡Ili: 'fail me .. which tells about I h.,t Renard. in li:uli week. Others hold r: t. I, i, p, ..t a book ''Ruth tsi S5 a k ] 1 .'\Vials to SIP N lt,11't' li,r in eilt call Write l'hiub' 1 . Ia.:., Radio TttimleiIm. iNu sulesm time. AutomnhiI.. t,b' , ' a t t w tu he ril Radio; Inuópraker ssaom.t t.' Get Sample Lesson and 64-page Book Age devices. are newer Dells offer;,. I Free-Mail Coupon tonillos to qualified men .t, i includes Tel eelslnn. nid,h p many good jolts ....in Many Extra Spare Time oWhile Learni The day yon roll, allll. retlllar ewer. I start s ndo: I Money .Ti,o Sheet: star) 'i.., l how to to Rollo rrp.Jr j la- TI 14X -1 1 r SMITH. President MIL rout.» T ad plies. n.I - your Dent. OM X. National Radio Instil,. l inns Ivhlrh h:n'^ tripcI In ., SI. a Week 257 RADIO -CRAFT for NOVGf1RER. 1940 HUGO GERNSBACK, Editor- in- Claief of F.M N. H. LESSEM ABC SERVICE THOS. D. PENTZ RADIO Associate 4 Editor in Director OATA HEETTèstRonge o 25 R. D. WASHBURNE, Making Managing Editor ¡,/peter a/ibratOr NOW t° Tester Modulation Contents NOVEMBER, 1940 FrequencyAmplifier Issue the Minia- Use VOLUME XII NUMBER 5 HoW1Oto ture Tubes Mailbag 259 Editorial: Radio for Defense Hugo Gernsback 263 The Radio Month in Review 264 RADIO DEVELOPMENTS SERVICING Your Job in the Aviation Industry - Staff Sgt. Charles J. Schauers 299 F.M. Servicing Procedure Charles E. Angle 266 S.S. America's Radio New 303 Circuits in Modern Radio Receivers -No. 38 Broadcasting an Aquaplane Race F. L. Sprayberry 268 303 RADIO SERVICE DATA SHEETS: No. 292 -Crosley Model 29BA Radio -Phonograph DEPARTMENTS, ETC. Combination (chassis model 29) Mailbag 270 259 No. 293 -Emerson DX -356 3 -Band Mantel Set The Radio Month in Review (chassis 264 model DX) 272 New Circuits in Modern No. 294 Radio Receivers -No. 38 -Howard Model 520APC Radio - Phono Combination 274 F. L. Sprayberry 268 No. 295 -Mitchell Mfg. Co. "Navigator" Globe -Radio "Miss America 1940" Records (chassis models TW and TWU) Y76 275 Operating Notes RADIO SERVICE DATA SHEETS (See 271 Servicing) 270, 272, 274, 276 Please -Mr. Manufacturer Operating Notes Don Foard, E.E. 275 271 Regarding Standardized Service Charges ... Charles R. Leutz Sound Engineering 11 277 -No. Conducted by A. C. Shaney 278 Television Servicing Problems M. E. Southall 285 F.C.C.'s Mailbag 298 Calculating Impedance at a Given Frequency .... J. D. Weiss 289 Latest Radio Apparatus Servicing Teleceivers 306 292 Classified Radio Directory- Section An Inexpensive Test Speaker 2 311 W. T. Hallowell 302 Shop Notes- Kinks -Circuits 319 SOUND Book Reviews 269, 302, 320 Sound Engineering -No. 11 Conducted by A. C. Shaney 278 Recording - Playback Amplifier as Direct -Coupled Output Published by Radcraft Publications, Inc. Publication Circuit and Equalized 30 -Watt Output Street, office: 29 Worthington 280 Springfield, Mass. Editorial and Advertising Offices: Vesey New York City. Chicago 20 Street, New 2 -Way Advertising Office: RADIO -CRAFT, 520 North Dynamic Phono Pickup 284 Michigan Avenue, Chicago, Ill. Calculating Impedance at a RADIO -CRAFT is Given Frequency .... J. D. Weiss 289 published monthly, on the first of the month preceding that of date: subscription price is $2.00 per year in countries, U. S. and Canada. (In foreign $2.50 a year to cover additional postage.) Entered at the post office at Springfield as second -class TELEVISION matter under the act of March 3, 1879. Television Servicing Problems M. E. Southall 285 Servicing Teleceivers 292 Foreign Agents: London -Gorringe's American News Agency, 9A Green St., Leicester Square, ELECTRONICS W. C. 2, England. Paris -Messageries The Electronic " Solovox"- Latest Radio -Musical Dawson, 4 Rue Faubourg, Poissonniere, France. Adjunct Melbourne to the Piano -McGill's Agency, 179 Elizabeth St., Australia. 290 Dunedin -lames Johnston, Ltd., New Zealand. F.C.C. * What is the F.C.C.7 Text 293 and illustrations of this magazine are copyright and must not be reproduced without permission of the copyright owners. EXPERIMENTERS * How to Electrify the 2 -Tube Superhet Leonard Lasky 296 Copyright 1940 Radcraft Publications, Inc.

258 MAILBAG

MORE \'. -T. VOLTMETER ARTICLES Dear Editor: UNBELIEVABLE Quite often. in service articles, the vacuum -tube voltmeter is recommended to the Serviceman as a very worthwhile addition to the bench. But material on the con- b ¡rt True! struction and use of such equipment has been limited. How about some articles in Radio -Craft on this subject in the near The Fam us future? I have found the articles on "Servic- Receivers" ANALYST ing Orphans and Private Brand ME /oSNER very helpful and I am keeping them in a folder where they are handy for quick Completely Wired and Tested reference. KENNETH L. Bt RUCKER, Baltimore, Md. Ready to Operate article in the March, April Yes, this 3 -part , 69a5° and May, 1940, issues was well -received by Radio -Craft readers. What other topics do ozzl' you suggest we cover which aren't already for covered in available literature? The editors do not profess to be clairvoyant, so tell us what's on your mind.

SIGNAL TRACING Dear Editor: In reading over many of the magazines and the trade papers, I notice that there has been quite a good deal of discussion with regard to "signal tracing." Much of the comment appears to pooh -pooh the idea of using any elaborate method such as is advocated by the Rider philosophy. while old and die-hard Servicemen loudly attest their ability to service sets with no more than a volt- ohmmeter. On the other side of the picture, we have the Wren who, equally vehement in their condemnation of the opposition. refer to non -believers as "screwdriver mechanics." It seems to me, in view of the above statements. that there must be a middle road which the majority of us may take. First step is to have adequate basic test apparatus of high quality, a tube tester, volt -ohmmeter, signal generator. Next, either a "signal tracer" or a vacuum -tube voltmeter. Finally, an oscilloscope and frequency- modulated generator, adding various other pieces of equipment as resources permit. Nobody, as yet, seems to realize that many service businesses just can't afford expensive apparatus. The result is that some men, lacking elaborate equipment, become very resentful of their more fortunate fellows and write nasty letters. The whole question, then, seems to be economic. Incidentally, where will the men who depend on test apparatus to do their thinking wind up when, perhaps under war time conditions, they must do a job and do it quickly? HERE'S YOUR LAST CHANCE! WILLARD MOODY, -hot in- truannt that has -old by the hundreds. York Before staking change- iu tool- .onl New City. in kit form, less tubes. at $60 Net! Its equipment to prepare for manufacture of not be to give the time and money saving ability can new nnmlels, Ise have decided who is using one. by offering the surpassed. Ask the man RE "RADIO DOCTORS' CODE" Serviceman a "break" remarkable offer at once. 1.1.1:-4 at a substantial Get in on this water To get the gist of the present model AN T11Ú 11.t Editor's Timi- is the identical See t our slobber following letter read "Radio Doctors' Code" reduction ill price. 1940 Radio -Craft. JUST OUT on page 162 of Sept. TIME PAYMENT PLAN 1941 CATALOG Meissner General Catalog is now avail- Dear Vie: Meissner ANALYST. with full The new The complcte able. Lists complete receivers. kits. replacement Here is another bird who thoroughly set of l3 RCA tubes. may be purchased with daily needs of remainder in coils. and hundreds of other with you. This saine subject has been a small down payment and the and experimenter. Send a postal agrees installments. Ask your Jobber the serviceman 7 years now, but it seems easy monthly card for yr.ur+ TODAY! on my mind for the Meissner Time Payment Plan. that there is nothing that can be done about about it unless we have a strong-arm squad out to enforce rules and regulations. Evidently- we have more mice than men in the radio industry; however I am willing to take another crack at it. If agreeable with you. I can cooperate from the New York area in attempting to clean up all the undesirables in this industry- and to RADIO -CRAFT for NOVEMBER, 940 MAILBAG

make it possible for the honest radio man taining such an excellent magazine to make an honest and clean living. Radio -Craft. as As far as the public is concerned, they I am a radio Serviceman will save money and finally working for the be able to have largest radio retail firm in our city an honest -to- goodness job done for and I a am always interested in the excellent radio o$s change. It is a wonder half the radio men service and public address articles in working aren't thrown in jail by this time, magazine. the because there are many things to be taken I get nay copies from my newsagent regu- up, and I don't know how you feel about larly and ,'./ the April issue in my opinion is this yet. Let me fr+ Men with radio know what you want to the most outstanding training are lucky today! Great of any issue pre- opportunities have opened do about this and I'll give you viously up with the National 100% published -there seems to be about Defense activities -more radio jobs in industry cooperation. twice more work for service - as much information in it as men -and be.t of all, IRVING HOROWITZ, usual thousands of new radio jobs that are provided and I like the new "streamlined" idea. for in the Brooklyn, Army expansion plans. N. Y. Like Frank Mills who writes in the issue April ARMY PAYS A PREMIUM! against xmitter articles, I believe * In the RE "RADIO WAR INVENTIONS" there are plenty of other \ tiitern. magazines cater- Field Artillery. Infantry, Tank (Wm- Dear Editor: ing for the xmitting panies-in every branch of the service men are needed fraternity and Radio - with radio and electrical Re Craft training. These men command a "Radio War Inventions," Sept. issue. would lose its identity as well as premium In pay and In lank. In fact, those who reach top de- rank as After writing to priving a great nomnatindssloned officer. get 6 timer more than almost everyone in Wash- number of Servicemen of a private's base pay: ington in an effort to learn where the excellent material which * Think that over -a knowledge of radio fundamentals I could inspires them means send my to move MONEY and RANK to you. whether you are idea for a military device, I finally ahead and become better ning to enlist now or plan- tech- wait for conscription. received, from Sen. Robert A. Taft, this nicians. PREPARE NOW! morning, a letter addressed to him by I personally have derived a great amount * With these 2 famous Ghlrardi self-training books, you John D. Biggers, Acting Chairman*. Let- of benefit from Radio -Craft and I am ran quickly and easily get the w luahle radio keenly ttr.0 background ter advised interested will mean so much to Nutt. Right now In your spate' me to write to National In- too in the Public Address articles born, - ventor's Council, Room 7422, Dept. of Com- by Shaney and the other fellows. merce, Washington, D. C. I did! If the magazine can be maintained at the Hope this information pleases level of the April issue it will you as great be doing a LEARN RADIO much as it does me. Don't thank me -thank job. I too am a ham -since 1926 "Bob" Taft like Frank Mills, -I, and SERVICE of Ohio; also the others who am unbiased. WORK with finally woke up. KEITH IIANE, Ex- ZL2FT, 'Mr. Knudsen is the Big Boss. 8 Karaka St., NATE SILVERMAN, Palm. Nth., BIG Lorain, O. New Zealand. RADIO PHYSICS COURSE HE LIKES US AN UP- AND -COMING Dear Editor: SERVICEMAN BASIC FUNDAMENTALS Let me express my appreciation ier s your tan in Radio: l: for your Dear Editor: u e are a splendid magazine, beginner. this e I would also like to add I big. all -Inclusive, short -rut, have been servicing radios elf my two bits and say keep for about -instruction book of meads Radio -Craft for year -and a .000 pages -a -half, and I learn more every with over the Serviceman. After reading Mr. Freed- along day llustrations will give you man's excellent that line of work. thorough training in the hu, article on how to make a I have portent fundamentals of Elec- Simplified Practical Signal been purchasing Radio -Craft tricity. Radio, Sound. Televl- Tracer, I feel at a newsstand slon, like asking and let me tell you I Cathode -Ray Tubes, etc. for store. 1 refer to his sugges- enjoy really -all the essentials. all its, the magazine very much. I background tion at the end of the article, adding have been you need for :. an taking .nmplete radio the magazine for knowledge. R.F. tuner, and V: T.Vni. using a 1 the last 10 No math -no previous training ma. months, and it's necessary. meter. If you very interesting and also It starts at the think such an article would a great help be worthwhile, and could induce but some of the things are as Al aboututl Electricityctrteaching .'nd Mr. Freed- you might say above man to write it I would appreciate it very my head as yet. It's by yourself at hone, in Spare very interesting to read rime, much. How about another the different lettera checking your progress True -False quiz in Radio -Craft with the SSO magazine from self exam ¡nul low by Mr. Freedman? and maybe some more different ttetiew Questions. Servicemen discussing different 78 PAGES after that. questions. USED BY ARMY AND JOHN BURGER, NAVY SS REVIEW R. W. itecaese ,hirardl makes B. GOtYGH, every- S8 REVIEW Westphalia, Kansa8. hing ,o yst al - rlear and Bloomfield, Conn. easy to understand, this eery. QUESTIONS ate Radio Physics Course is u ed by the U. R. Army and Navy, Marine Corps, CCC Camps, and by no. ro TROUBLE WITH V -T VOLT- FROM A JAPANESE ,.rols all - .. than any ooh r radio book:,r- READER METER ARTICLE Dear Editor: Dear Editor: I have very interesting about Supersonic MODERNRadúiSERVICING note, and I have built the V.-T. Voltmeter by Turner the communication with it, Dear ow- in the June issue of Radio Editor, Please expornent details LEARN HOW -Craft. Would superior of new you please tell me why, when you short and relishfull study at your coun- with this! the A.C. input, the meter will try in me Radio -Craft Mag. This famous Ohirardl book will read about The teach you how to test and service 0.4 -ma. after it has been set at zero? electric musical instrument is highly all types of electronic and radin appreciated also. equipment. It's an illustrated EVERETT E. Cox, 1300 -page Yours "cold mine" of tern - Kaa8a8 faithfull subscriber, Icing knowledge. 420 pages ex- City, Mo. plain all types of servicing test This letter was forwarded to the SIGETAKA MASUDA Instruments - how they work. Author, No. 421, .low con.trueted, hnw to build whose reply follows: Fujikata them, how to use them. Then Tau -Shi, Miyeken 900 mere pages gire roil a Dear Mr. romp) re step-by-step procedure Cox: Japan. course in troublshooting test- When the A.C. input of the instrument ing, aligning and repairing all is We'd be some pumpkins if we were stink., of radin sein anti other shorted (as when the test prods equally Iectrrmic are touched as good in Japanese, device ., The eeryee together), the positive all right. We will try latest d randce scientific Factory pole of the bias cell Methods to run an occasional article on supersonics. of trouble .hooting and is connected directly (with the range selec- ouutalr} ronork Also we will continue to record radio's vari- You ulearnldnrvice tor in the 1 -volt position) to the diode ous es.ilw at home with developments, including those in examination 720 self- plates. The increased static indication elec- review questions to 1300 PAGES is tronic music. -Ed. clink your progress, 708 ILLUS. the result of impressing this D.C. potential Send for these books now-you can return them and your upon the diode. On the higher money will be refunded voltage If you're not completely satisfied! ranges, the cell would be connected around INCREASED GAIN FOR P MAIL COUPON TODAY! to the diode through one or more resistors RADIO .1 of PUSHBUTTON B a TECHNICAL PURL. Co.. Dept. RC -11O the input voltage divider which would SETS Astor City Dear Rend reduce the false Editor: I postpaid, with R -Dy Money Back Guarantee: II reading considerably. O RADIO PHYSICS C011tsE With the MODERN 8 -I. 54.50 toreltrnl RUFUS P. TURNER, advent of pushbuttons for Q RADIO SERVICING $4. 1$4.50 foreign) I WIAY tuning many manufacturers cut down on Name the R.F. sections FROM A NEW ZEALAND READER of their receivers in order Address to avoid the complications and added cost of ern- ... Dear Editor: tuning s Please send cut extra stages with the buttons. Ftti'1: Illn:lratnl dt-s.rim i sie ii-rvt,tr, -, For some time past I have been going to 6a M 'MONEY BACK IF NOT This, of course, caused a lack of selectivity SATISFIED. a write you and congratulate you on main- and overall poor performance, Diagrams A 260 RADIO -CRAFT for NOVEMBER, 1940 MAILBAG

and 13 show how this has been overcome YOU CAN BECOME A MONEY- MAKING RADIO EXPERT &a RADIO SERVICE EXPERT without adding to the button -controlled cir- LEARN AT HOME IN SPARE TIME cuits. ÿ Iron -core coils are used which reduce ad- lessons pray I fear, simple. fascinating interference considerably. In tyondfrlctl Beal work with experimental kits !deice jacent- channel p training easy and last. Up to date R.T.A. diagram A, the resistance-capacity coupling guidance of prominent engineer TRAINING in art h ter personal indus- besides adding greatly HOME Ii ghly endorsed by leaders in radio has some selectivity and educator, training. try. Spare -time profits soon pay for to the gain. This arrangement will provide You Learn Easily In your own hinnies. Irate more gain than will an ordinary tuned cir- Your Spare Hours . NOW or lit yourself for well with START in factories, police. marine the mixer. By Doing Many Experiments paid work with radio dealers, cuit at Up -To -Date Equipment or television fields. DON'T DELAY: end AT ONCE for complete in- BOOK Send FREE! REMOTE CUT-OFF TUBE OCTODE CONY. Here's a really fine. up-to-the c.. AMERICA ppp Radio and Television Training that'. RADIO TRAINING ASS'N. OF ZÓ MS dally designed in give you quirk fie. Doyen Are. Dept. RC -110 Chicago, 111. TRAINING PREPARES YOU FOR GOOD 135111 COIL RADIO JOBS ... AT EXCELLENT PAY. 31y training starts right at the hrgimdn; of Iridio . unfolds each subj,vt in u 1mV11Ocd, logical, understandable stvte. RADIO TECHNOLOGY You easily barn Television. Electronics. Institut . orcrr an intcn.ist co irse of RCA of Radin Facsimile Radio. Radio Set Repair and high standard voila drIng all pha -es Installation %Vork. I., Practical training with modern and Television. schools. NO PREVIOUSOU EXPERIENCE NEEDED equipment at New York and Chicago It makes difference courses in Aviation Communi- Also specialized Oper- as been. I can tir you for a Conti -0033, ctions. Radin Nery icing and Commercial Radio lob. Your success is my full ating. Catalog Dept. RC.40. 10,000 responsibility. RCA INSTITUTES, Inc. OHMS YOU GET PROFESSIONAL TEST EQUIPMENT PLUS A.V.C. EXPERIMENTAL OUTFITS Corporation of America Service T eB+ Re- A Radio Mart. CMcas. . Includes 110 Radio Parts Ito build complete 73 Varlets St.. New York, 1154 Merehaadlse ceiver). Tools, All -Wave. All- Purpose Analyzer, :rod Es- for conducting actual experiments with Drimento lOuttshands. I Supply EARN WHILE YOU LEARN RADIOTELEYI51011 My ISINESS OWILDSRS show y how to put your Equipment to practlesi YoU handling actual money-makIng Television school In west trains 116 RADIO PARIS you Oldest, largest Radio- including RaIndio shortly after hn pay Job. Complete ins%rurllon begin training.eiJobs gusci Broadcast Operating, Sound. Construction and Service. etc. Flexi- Pictures, Television, Public Address. SERVICEMEN Talking those with or without specific nieds of 1 ble plan to meet room and board offer Adv.need Training jobs. Transportation allooed to L.A. for those already in Ra. Pr ro .oEarn dio. Get complete details while Tea in my FREE 52 -page Book LoAn`SIX Th. Sprouberry (goes. NATIONAL SCHOOLS 11010 IDES is Sold Ender a Money task Aprremnn( COURSES é RUSH COUPON BIG FREE BOOK RADIO B makes use of a different lo I Nov, Starting Diagram F. L. Univeerry, Ires. Classes Coil L2 is an untuned, 320-L Ynivep1 c lace, N.W.. RADIO orERATIN(;- BROADASTING method of coupling. i SERVICING a practical course iron core. RADIO - TELEVISION close -coupled transformer with an rr Please FREE ny of ASIATEI'IL CODE TO MAREsend MONET IS RADIO." RADIO coulee )'ta. eve. secondary is to AI l PULPOSI INJI(J1R ' RO%Y LLECTEGNLCS -1 J'r. day i The resistor across the I II Rt'gmest. Name Age .... nay and EYCninlr elassoa, Booklet Plwn broaden the response. The resistor in series Y. M.C.A. Schools with the primary is also to prevent reso- Address New York New York C.tY a W. 64th Street nance The better coupling that the city ...... state .... I peaks. Tear off this counnn. mau In e provides results in a greater lope or loste d ln transformer t éxeo C LE Correspondence Courses gain than the arrangement of diagram A. INñhk I restore selec- tfrI RADIO dnd ELECTRICAL £NGIN££RINC (Philco is using this system to tivity without adding to the circuits for ELECTRICAL ENGINEERING',;:' .. .! tété" LOW Cost, to control.) trirai rind. Prepare yourself. at "n000éklre the pushbuttons futiles modern. lined, you can u t WILLIAM BOYDSTON MILLER. Er aáéien:ac 1, ,vest, t'.:";t: RADIO ENGINEERING w tithe Beach, Calif. Trains you to be uperaervice n vacuum Laguna Exper. kits (unshed.. Diploma technician. er Deferred a ono,uilupian. Tuition. EGteither catalogs. details SEND rNOW! RR E ma¢ zie.nsc complete SCENE IN 111423. LINCOLN, NEW THE CHANGING LINCOLN ENGINEERING SCHOOL, Pear Editor: Eventually, when all good things come to pass. a radio Serviceman will be paid for his work without being asked, "All that, just ÇREE!GIVEN for labor ? And if he is the subtle type, and does not charge outright for labor, he Will not be asked, "Why does a condenser cost so much ?" TO you day, when it comes, This great future THIS SUPER will find the radio Serviceman or dealer ordering tubes which will not be superseded MAGNET by duplicate types before delivery. Further- will not be beaten down THAN 20 more, his prices LIFTS MORE by cut -rate advertising of large (distribu- - TIMES ITS OWN WEIGHT tors engaged in retailing. The Serviceman LITTLE GIANT MAGNET -The world's dealer will, moreover, in this magical fu- 11,s. easily. most powerful. Lifts 5 new to Weighs a oz. Made of ALNICO, ture. find that radio sets are not sold high -magnetic steel. The xperimenter holdwist find of him at a high price only to be (lumped on and %or this high quality permanent magnet. Measures 13í x P ^. t mwith the market 2 months later, wiping out his keeper Value Sl00. chance to realize a profit on his investment. EVERY Radio GIFT, FOR SELLING ONLY Mechanic YOURS, AS A The Serviceman- dealer may even be so Service Man -& 16 "CASH IN" BOOKS! wit- Student Needs s ender fortunate as actually to Nn Invas nuent needed. %Ae tn(st o. 5 u ot.lr ridiculously ".AUdels Radio - ,woks from us. sell them for I5c each.h. and 'ben y,u of big electric the to (within 30 and w ill ness the non -participation mans Guide'- collect $2.40. it MAGNET absolutely FREE! Just Outl the LITTLE PANT' we ff power companies in the retailing of radio the Or Yoúun bier the here gifts The whole subject of Modern Radio - covering Ot con the first in 5-our appliances. He will then k Operation-- -Serv- Fill OlCr fl today. receivers and home Basic Principles-Construction neighbor, is't l rev rn1 money, and it is to be ice -- Repairs -Troubles -Ail Easily Understood. begin to make some ( 750 Pages. 400 I Ida trations. Parts & Diagrams 0 Ways I -SEND NO MONEY- ver for To - will not prove fatal. LATE TELEVISION DATA -Valuable National Plans Institute. hoped the shock AND HOME STUDY. Make 240.8 Fifth Ave.. New York City ever again built §- REFERENCE form MoneS ac Please smut me Id Finally, if radio sets are Gentlemen: Poor in and mail coupon%ä.ÿy looks "CASH IN. eh h I wet will be amazed to the point where yourself fill sell at pay for to last, he COMPLETE PAY ONLY S1 A MO- ADO- n 30 days. The, And if the ./ he Sci e he will be rendered speechless. will semi MC r LITTLE AUDEL, Publishers 49 W. 23rd St., N.Y. 40.000 GIANT MAGNET. Aslo on a tube extends more NEW ItAI %IOM ANA) GUIDE for free esann- Words list ofoother guarantee period NW Atli/EIS y1 dore: then remit al Immediately If O. g. 1 will end y in'1 ,-nur a 1 wdl rotato It. of Teal free iteiy than 90 days. or possibly is lengthened to muaWly uptn prltt of E; ill paid. Otherwise, o'CASII IN'' contains become a Sphinx. ono teul.d matt order year. he will definitely Name - rI' se- Name to radio sets, then he crets. formulas. If the saine applies Addrrsa- - real money Address is just a dead pigeon. makers. 08 loges. Ocupation_ Th. book will sell it- Cliv .. St. WILLARD MOODY, fIf to all of your PASTE COUPON ON le POST- Reference. RCP I York City. riends. lativH and [ CARD AND MAIL TODAY New neighbors. 261 RADIO -CRAFT for NOVEMBER. 1940 Tot L/ettet Setviein y - (Tot 2yy e7 /fro its - USE GERNSBACK MANUALS AND BOOKS!

lP ItVN FNa: wolfs RatiT 111 ANA! YIO.ILS

SINCE 1931 Servicemen have been buying RADIO -CRAFT LIBRARY more GERNSBACK OFFICIAL RADIO SERIES (:.t into the swing of reading instructive, SERVICE MANUALS year after year. The subjects- authoritative books on technical au- radio, air conditioning and refrigeration. It's the easiest, quickest thentic material. easily and most inexpensive may accessible diagrams and to improve your knowledge on these topic,. complete service In thie series, popularly known us the RADIO -CRAFT LIBRARY data make them invaluable are all the titles SERIES. to dealers and necessary to your personal advancement. Only by careful radio Servicemen. Without a study of these enlightening books, can you gain adequate Gernsback fields experience in Service Manual at the repair job, there's rinse of radio, air conditioning and refrigeration. Each book and The volumes is uniform. profit lost. Your service kit or laboratory measure 6 x 0 inches -contain 64 pages, and have is incom- flexible covers. stiff, plete without all the GERNSBACK OFFICIAL RADIO PRICE 50c I'Elt BOOK. All books are sent to you postpaid. SERVICE MANUALS. There are GERNSBACK MAN- UALS for servicing auto -radios, also refrigeration and Here Are air conditioning equipment. The Titles: Book No. 3 Book Na. It THE SUPERHETERODYNE BOOK POINTTOPOINT RESISTANCE VOLUME 7 OFFICIAL RADIO SERVICE MANUAL ANALYSIS Dow 1.800 Pages User 3.000 Illu -brat i.s, Stiff, M. LIO6oeleaf Covers Sine tl Leather. Beek No. 6 x 12 inches Net Weight $ 1 0.00 BRINGING ELECTRIC SETS UPTODATE Book No. IS PRACTICAL RADIO KINKS AND 1936 OFFICIAL RADIO SERVICE Book No. 9 SHORT CUTS ELI 1,800 Pager MANUAL AUTOMOBILE Ika :ver 2.500 111uatratlou. . RADIO AND Leoulraf Covers nine ; x 12 n,el,ee $7.00 SERVICING Book No. 20 THE CATNODERAY Book No. 10 OSCILLOSCOPE HOME RECORDING AND ALL 1935 OFFICIAL AUTO-RADIO SERVICE MANUAL ABOUT IT p y Beek No. 21 MM, Loeo.eëtat Cover.. O BREAKING 63z sbiz In -t $Z, 50 Book Ne. 13 INTO RADIO SERVICING ABC OF AIR CONDITIONING Book No. 22 Book N- o. 14 NEW RADIO 1934 OFFICIAL POCKET RADIO GUIDE QUESTIONS RADIO SERVICE MANUAL AND Oee 400 Pasea Over. ,000 Illustrationx ib1c. ANSWERS 1Loeieef Cerera Size F1. `.`...,i' 0 x 12 Inches Net $ Book N- o. 15 $3.50 ABC OF REFRIGERATION Book No. 23 PRACTICAL PUBLIC Book No. 16 ADDRESS 1932 OFFICIAL RADIO SERVICE MANUAL PRACTICAL RADIO CIRCUITS Over 1,000 Pares Over 2,000 111 lstratlonx F -h , NEW IC:JD; Looseleaf Covers. Size O x 12 inches -Book No. 24 lbs. 55.00 Book No. 17 AUTOMOBILE RADIO SERVICING WITH SET ANALYZERS PRINCIPLES AND PRACTICE OFFICIAL REFRIGERATION SERVICE MANUAL EACH 1O1B1ertillesll l BOOK IN THIS SERIES -50c Over 352 Panes 0, er 300 Flexible. Leather. et*, Looselesr Covert. S., 0 x 1 2 Inches Net weicht I t _ l hs. 55.00 ^ IfItf-It\I l l'I 11I.1C'ATIII] Inc., 20 VESEY ST., \I \\ YORK, N. Y. I i lind nu t e of t for which ,. .,.e. IL \I.. .s lo..k, POSTPAID, I OFFICIAL AIR CONDITIONING SERVICE MANUAL indicated Ib by a OM, lx) in the pane:. Orivtaer I (1 Volume 7 @ 510.00 ( ) 1936 Manual @ ( ) , L2o5o2s ePleaaef... 57.00 1934 Manual 2L,o lbs. @ $8.50 ' $5 .00 '( ) 1935 Auto - Manual @ $2.50 ( ) 1932 Manual @ 55.00 O Refrigeration Manual (Vol. 2) $5.00 ( ) To order these famous Manuals, see or write to @ Air Conditioning Manual @ 85.00 your jobber or favorite mail RADIO -CRAFT LIBRARY SERIES @ 50e order house. If more 1 EACH I. rrlc h,,lk ohln4ers named: 3 10 convenient, mail coupon directly to publishers. U 0 13 11 15 Pi IT 18 19 t:o 2! 22 23 24 1 Name ¿Mires,

' City RADCRAFT PUBLICATIONS, Inc. State (Send remittance in form of cheek or money order; register your letter if you send rash or unused 20 VESEY STREET NEW YORK, N. Y. U. S. Postage Stamps.) RC -1140 L.-.L. as as - .. - - - as ...... as as IIIM 11=1111 mil _b: RADIO -CRAFT for NOVEMBER, 1940 "RADIO'S GREATEST MAGAZINE"

. it is usually the private individual who crashes RADIO through with important inventions FOR DEFENSE By the Editor - HUGO GERNSBACK uals will, in our present emergency, come out on top and occasion tit, speak before on the tremendous value IHAD new crop of radio inventions, the sanie as was of radio for the country's defense and war purposes. There produce a of greater importance than the case in the past. is hardly a science today again, that any national with all its ramifications; during the coming History has proven time and Radio a tremendous stimulus on inven- months this importance will tend to grow. emergency always proves period in our history, I am convinced, will I find it necessary to come back to the subject time and tions, and this radio not be different from those of the past. Radio is such a vast again, because the average person, and frequently, complex they know too much of domain, and is so closely interwoven with our men themselves- because they think miracle if no great themselves into believing that every- Machine Age, that it would indeed be a the subject-hypnotize were to come about during the next few thing worthwhile has been invented and that there is no radio inventions in the art. years. room for improvement remains to be accomplished in our Independent radio workers also, are apt to lose interest A tremendous job which present preparedness effort. There is hardly a single instru- in radio research work, because of false propaganda defense which radio improve - mentality that can be used for our national makes them believe that the only worthwhile with radio. Many problems inventions nowadays come out of research labora- in some way is not closely allied ments and solved and radio often proves the key to the tories owned by our big radio corporations. remain to be This reasoning is altogether faulty, and does not jibe with answer. our big corporations In t':e past, history has shown that for every new weapon' the actual facts. While it is true that some form of defense vast laboratories and spend fortunes in develop- there has eventually been developed do maintain The airplane, and particularly bombing planes, ing new ideas, it will be found that ordinarily these inventions mechanism. so remain a direct threat to all nations, while an effective tie -in with the corporation's own developments and their own far of untold answer to its menace has not yet been found. Antiaircraft business; only rarely are new inventions that prove Airplane laboratories. As a rule, guns are only a partial and incomplete answer. value to the country developed in such due to the tremendous' are maintained for definite purposes against airplane also is not the answer, all research laboratories itself. Even two countries well matched; and research work is nearly always in a given direction. speed of the airplane laboratories rarely stray with the same number of planes, will still be in a position Research workers in commercial because defending work is already cut out for them and to do tremendous damage to each other, far afield because their all points at the same time, and as must limit their activities to operations directly related airplanes cannot be at they can operate at different altitude levels their potential to a specific result. It is true, that this is not so much the they here the research men danger is so much greater. When two nations can oppose case in university laboratories and armament and speed in freedom, but even here, the laboratory personnel each other with the sanie tonnage, have more can stalemate each other, or there will be is not permitted to work on any and all ideas which might battleships, they a predictable draw. But, two hostile airplane fleets, evenly pop into their heads. get past each other, inflicting immense The private individual has no such limitations and he can matched, can still and everything he wishes to. If he has the damage on each other's territories. work on anything one of the answers to the warplane and time and ingenuity and equipment, the sky is the limit. For I ant certain that the private individual is bomber will be radio, or some radio instrumentality, perhaps this reason, it still holds true that as yet known or tried out. it comes to original inventions and the allied with some other means not often far ahead when herald the approach of bombers today past record shows that it is still the lone worker who is able Listening devices to and it is usually he are known to be rather ineffective. Such information comes to satisfy himself and his ambition, the airplane will have through with important inventions. too late, because in a few minutes who crashes the 10- or 15- minute advance of the following, which does not by any means traveled such a distance that A list come to naught if there are no airplanes exhaust the subject, proves the point. Not one of these in- warning will have at the time in the air at the time and near the region, and at proper dividuals was working for huge corporations All this means yet all these radio inventions were fighting altitude, when the attack is coming. he made his invention, radio will probably be the answer important ones. speed, and more speed, and Radio Inventions to the problem in some way in the end. Guglielmo Marconi Numerous major problems that will have to Pickard Crystal Detector This is only one of the G. W. Entire books could be filled with other problems Dr. Lee (le Forest Vacuum Tube be solved. still unsolved, many of which will be solved by radio. Edwin H. Armstrong Superheterodyne communication. Here is a Farnsworth Television Tube Remember that radio is not just Philo T. radio is doing today, and it is only a partial list. do not think conditions have changed very much, and list of what I men, themselves, are apt to forget how vast a it is my firm conviction that this trend of private invention Even radio almost indefinitely. science Radio is today. will continue list will be found on page 304) I am also quite certain that hundreds of patriotic individ- (Complete 263 RADIO -CRAFT for NOVEMBER, 1940 THE RADIO MONTH IN REVIEW The "radio news" paper for busy radio men. An WMCA, is specifically designed to spotlight illustrated digest of the important happenings 5th column activities by revealing how they operate in the United States.. . A slice of the month in every branch of the radio field. of the $15.000,000,000 (yep, that's 15 billion) so far ear- marked for America's preparedness program (2 -ocean Navy, 2- million Army, and 50,000-plane air force) will go to establish 7 schools to train 4.000 radio- "FATHER OF RADIO" men and signalmen for the Naval Reserves. IS 67 Courses last 4 months, Students rate active August 26 was an im- duty status, and grads become Radiomen and portant date to the radio Signalmen, industry. It marked the 3rd Class, with 3 months' event of National Radio optional active duty, ashore or afloat, with Day and the birthday of is top pay of $60 per month. The Army, too, radio's ''grand old man" is planning new Lee de Forest. Two hun- radio schools... , dred members of the Thix department radio industry threw a calls attention to banquet for him at Chi- the statement of Sigrid Schultz, 1COR- cago's Drake Hotel where .11atan/ correspondent well- in Berlin, in a earned homage was broadcast from .'Nazi heaped upon him. Shown -land, that Hitler at the banquet scene are, concedes his successes would have been left to right, William impossible wiNrn5ft the aid of radio to Halligan, Pres., Halli- maintain substantially crafters, Inc.; Dr. Lee Ha interrupted de Forest; E. S. Riedel, contact with all units of the mechanized gen. sales mgr., Raytheon blitzkrieg »mchinc. Production Corp. ABROAD LAST month the t,ulay Noes of New York carried a copy- PREPAREDNESS righted article entitled "Boat Run by Radio, Once U. S. Secret, Is New UN) N;cA1 i< ),ow finding Hitler Weapon." This illustrated that peacetime developments article by Sloane Taylor goes on to tell how well- in the broad field of radio convoyed Allied shipping, are of inestimable value mysteriously sunk. in the work of actually was hit by remote-controlled. "safety first" mobilization of our defense explosives facilities. -laden 16 -foot motor launches, or Ferule ¡tbont. These unmanned launches For example, last month WOR Trans - were directed script ion Service to their objective -and their recorded four 15- minute own annihilation-by an disks of talks, urging enlistment 8-man crew in a in the second or control boast within telescopic 17. S. Army and Navy and training camps, range. by One of the controlling signals is Col. Frank Knox, Secretary of the Navy; capable of causing the destruction Robert Patterson, Ass't Secretary of War; of the remote- controlled bout if there seems to be Col. Hugh S. Johnson; and Col. Julius Ochs any danger of the boat Adler, civilian aid Secretary and its mechanism to the of War. falling into the hands of, for instance, The platters were shipped to over 200 broad- England. ( Hammond cast stations as sustaining features. in America is generally- credited with demonstrating the first craft of this sort around 1920.) Television was used, for the lirst time, for peacetime recruiting when the Army Sings, pore. - - Radio -controlled planes - Recruiting Division in Los Angeles inducted about the size of small, American flivver a group of recruits into the service before planes --are being used at this stronghold SIR OLIVER LODGE, 1851 -1940 the television essaieras of the British Pacific defense.,, Sir Oliver of Don Lee Television as targets Lodge, eminent inventor, scientist, author station W6SAO in Los Angeles. This for anti-aircraft gunnery practice. and spiritualist died ors August 22 at his home in "Uncle Amesbury Wiltshire at the age of 89. Among Sant Wants You" television program lasted many the England. --A "radio searchlight" is re- brilliant experiments performed during his l'á The lifetime those hours.... program "Hands Across ported by the New York newspaper relating to radio and electricity the Sea" regularly broadcast over PM to included h work on the conductivity, Thermo Inter- be in use by the British to detect approach- and electric, of metals and other national Shortwave Broadcast substances; mutual - station ing airplanes when they are yet scores of and self- induction resonant circuits, and the radio WRUL in Boston, and beamed on England, detector later called miles away. The opinion was advanced the "Lodge coherer." His ex- is reportedly doing a great job of that periments extended Hertz's demonstration of Max- bolstering it operates on the principle of the "terrain well's electromagnetic morale of overseas bomb- theory of light. Lodge en- harassed listen - clearance indicator" or radio altimeter de- riched the radio art with his inspired researches. ers-in on 11.79 and 15.25 me. ... "Trojan veloped by Bell Labs. (and described in n Horse," new sustaining program over past issue of Radio- Craffi.

THE IRON HORSE GOES ON RECORD! (Cover Feature) Robert Monroe, author of N.B.C.'s dramatic serial "Rocky Gordon," is shown in New York Central Yards at Weehawken N. J., recording the sound of locomotives and railroad yards for the sound effects to be aired. E HEALTH RAY METER A new instrument designed by Dr. Robert J. Cashman, assistant professor of physics at Northwestern University, is being used by meteor- ologists and bioclimatol- ogists fo record the intensity of ultra -violet solar radiation. Electric- ity generated when an ultraviolet light falls on a nickel disc coated with magnesium is caught up on 2 tiny wires suspended above the disc, and is then measured. 264 RADIO -CRAFT íor NOVEMBER, 1940 THE RADIO MONTH IN REVIEW

tondoo.- Perhaps the first Americana COLOR TELEVISION "radio casualty" case was that of John Dr. Peter C. Goldmark, C.B.S. chief television Steele, WOR- Mutual's London commentator, engineer, is shown at the who collected a bomb splinter while on a still projector of the dash from the B.B.C. studios during the color television device which he invented and height of a German air raid. which was recently dem- Norway.-A Nazi court at Oslo last month onstrated before the press. The same fre- dealt death sentences to 3 Norwegians. ('ol. quency band width re- Lund, Medical Officer Solent, and a Mr. quired for ordinary black Engdahl, said to have been convicted of and white images can be used for color television. maintaining a secret broadcasting station, It is possible that in the I.V.S. reported. near future a simple attachment may be sold Sweden. -The Swedish Ericson Co. has which can be attached to marketed an inexpensive air raid alarm---11 standard black and white doorbell and special fittings --which plugs television sets to permit be them to receive color into the regular lightline and can auto- images. The present film. matically operated by a slight rise of line scanning equipment used voltage ut the power house. (The rise is with this system employs on 16 millimeter film taken too slight to endanger other apparatus at 64 frames per sec. but the line, such as a radio set, etc.) run at 60 frames per sec. Image has 343 interlaced lines.

LAST month the total of Fre- News released a photo showing morning - quency Modulation station glory truck- loudspeakers going full blast as applications in the hands of Wendell addressed a huge audience in the I'. .t'. jumped 25 more; total. waiting Juliet, Ill. Confidentially, Mr. %Villkic, didn't for the green light: 150. Some of the appli- that Y.A. system help speed your recovery cants plan to operate stations estimated to from that sore throat condition you had? have a service area up to about 33.000 sq. miles. A score are now regularly ou the air. Aero- Voice, new recording company in New York City. has a mobile unit for Is New York City going to let other cities making spot recordings anywhere.. . The pioneer the path of F.M. police -radio "? nee- $3,000,000 recreation project at Ocean Latest city to vote for F.M. is the Chicago Beach, New London, Conn.. is said to have Police Dept., which issued specs. for bids the most elaborate sound system in the on 200 F.M.-equipped 2 -way squad ears and United States. It's a W.E. job 5, ctt 16 fixed -location stations.... Time maga- with impaired hearing has been equipped zine last month took tinte out to analyze the with a hearing -aid, stated The Delta Re- status of F.M., under the title, "F.M. By porter (Gladstone, Mich.) last month, and Stages." The article offered the estimate sported an illustration to prove it. that 5.000 frequency modulation receivers Ilere's how WT 31.1. the Milwaukee Journal have so far been sold.... A total of 42 station, answered the question of how to be large F.M. stations may soon be joined in in 2 places at the sane instant. Finding a coast -to -coast network! Here are key that the city's supt. of schools would not station owners, etc., in the projected set -up, be able to leave st broadcast at \\"TMJ in scheduled to be in operation in 1941: The time to attend graduating classes at Mil- Yankee Network, Boston (John Shepard, waukee's high school, the school set up its RADIO. POSTMISTRESS 3rd); KV00, Tulsa, Okla. (\\'m. Way); P.A. system in the school auditorium and Vivacious Jean Muir is the only postmistress to date of the U. S. Antarctic Expedition. She is shown read- KROK, St. Louis. Mo. ( Elzey Roberts); fed the system with the supt.'s radio speech. ing the fortnightly- mail to the 59 men now snow WTMJ, Milwaukee, \Vis. (Walter Dantm9; as part of the graduation exercises. bound in Little America over G.E.'s shortwave radio WSM, Nashville, Tenn. (Harry Stone); station WGEO in Schenectady. Shortwave radio is WSJS, Winston- Salem, N. C. (C. Gray); the only contact these men have with the outside she was proud of the work and, H. L. Pettey, Los Angeles, Calif. Paull II. 'l-nrtak. p res. of Ox t'u rd- 'l'a ttak world. Jean told them Corp., his they were doing for our country in the Antarctic. Radio last month announced (Photo on cover.) :acquisition of a substantial interest nt SOUND United Teletmse Corp. Both conipamits will CilLCKLE, chuckle. Last month continue marketing their respective lines -or maybe it was the month of loudspeakers.... Radio Daily records the hefore- W.L.W., in what was suggestion of an Ohio publication that practically a tidal wave of economy. said Wendell L. Willkie use as a play on the something like this: "Nope, no public ad- well -known radio station slogan "WLW -- dress trucks during this campaign. Too The Nation's Station," the political slogans expensive." But last month International "W.L.W. -The Nation's Choice."

"PHANTOM RAIDERS" "Don't come any nearer" Joseph Schildkraut holds off enemy gangsters while he prepares to operate a shortwave set that will blow up a freight ship miles away, in "Phantom Raiders new Nick Carter adven- tere, featuring Walter Pidgeon with Jacques Tourneur directing for Metro Goldwyn Mayer. "SSO ON YOUR DIAL" Frederick Stephan' is the This automatic radio transmitter installed by the producer. (See photo on Halstead Radio Traffic Control System on George cover.) Washington bridge between New York City and New Jersey sends out traffic information to autoists at regular intervals. The messages are picked up on auto receivers tuned to 550 as specified on signs. (See photo on cover,) The traffic messages are recorded on steel tape and can be changed at will by police authorities by remote control. The menage is magnetically recorded and erased. RADIO -CRAFT for NOVEMBER, 1940 265 SERVICING

F.M. SERVICING PROCEDURE

The following article contains the recommendations of a factory service manager on procedure for servicing frequency modulation receivers. Frequent comparison with well -known amplitude modulation service procedure is made.

CHARLES E. ANGLE

Radio Serviceman is vitally interested in the TO PLATE OF _ 50 47,000 6577 5OMMF. development of Fre- LAST I.F. MMF OHMS LIMITER EVERYquency Modulation. Much has been STAGE / written describing F.M. and how it works and it is the intent of this article to go on from there and point out briefly what w \ 1 the Serviceman's problems will be and how 05- they should be solved. 50 AMP MF (EACH) . h ` .005-MF, 0.1-I 11/4.27--MEO. t-- FUNDAMENTALS MEG. +95v. 1ME0./ 47.000 MF. There are 3 fundamental points to be -t0.000~ / . - g .I2.2MEG5 remembered: .005- oHMS M^^-1 1- .05- 17- .001' ,005-MC. MEG. MEG MF, e MEG. 1/ TO CONT (1) Broadly speaking, the methods to be I lee To OTU9E GRID OF A.F. followed in locating CONTROL- TO TUNING trouble and cor- +260V. AMPLIFIER INDICATOR RECTIFIER= recting it are identical with A.M. sets GRID .04 -MF tOp MM F. (EACH) (2) F.M. Receivers are high- frequency re- The limiter and demodulator stages of an F.M. circuit are important points for the radio Servicemen to watch. ceivers and must be treated as such. This diagram is part of the Stromberg- Carlson Series No. 480 F.M.-A.M. sets. (3) The circuits are essentially the same as A.M. circuits except that the particularly the 4.3 megacycle I.F., regen- ampere meter with a 1- megohm resistor in Limiter and Discriminator circuits, eration is very likely to occur. series across one -half of the discriminator and the I.F. and R.F. Alignment pro- This regeneration may be caused by any load. The signal generator with an 0.1 -mf. cedures, are new and must be handled one of a number of conditions. If it is condenser in series is connected to the con- with great care. necessary at any time to replace a part, trol -grid of the limiter tube and the signal extreme care should be taken to install the necessary for making adjustments is ap- In any F.M. Receiver, the I.F., R.F. and replacement part in exactly the same posi- proximately 1 V. The primary Audio of the dis- circuits are essentially the sane as tion as the part which was removed. When criminator transformer is then adjusted regular A.M. sets; therefore, service proce- locating or correcting trouble, the wiring of for maximum reading of dure will the microammeter. be essentially the same although the chassis should not be disturbed. The The center "0" microammeter should then some of the test equipment in use today plate, screen -grid, control -grid and cathode be connected across the whole discriminator does not have sufficient range to deal with of all tubes used in F.M. receivers must be load and the secondary of the high the discriminator frequencies and the wide bands. bypassed to a ground point directly at the transformer adjusted for "0" reading of the The minimum test equipment which any socket as a long ground lead is a common microammeter. service The remainder of the I.F. shop should have is as follows: cause of regeneration in these circuits. circuits are adjusted by connecting the (1) A good signal generator (test oscilla- Many explanations of the limiter and dis- output of the signal generator to the con- tor) with variable output voltage and criminator circuits have appeared previous- trol -grids of the various I.F. tubes, and a frequency range of 100 kilocycles to ly and it is not necessary to go into them adjusting both primary and secondary for 32 megacycles. in detail in this article. maximum signal, making any slight read- justments (2) A wide The limiter, in reality, is the last I.F. necessary to produce a sym- -band signal generator with a metrical curve. sweep circuit of ±200 kilocycles. stage in an F.M. receiver and acts as an These will, undoubtedly, be available amplifier which is very easily overloaded. R.F. adjustment of F.M. receivers is made shortly. The primary purpose of this circuit is to at the point specified by the manufacturer. The center (3) Cathode -ray oscilloscope. limit the variations in the I.F. circuit ahead "0" microammeter should be left of it and to pass on to the discriminator connected across the whole discriminator (4) Output meter. a constant -amplitude signal. The discrimina- load and a "0" to 200 microampere meter (5) Center "0" microammeter and a 2nd tor, which also acts as a detector, converts should be connected in series with the microammeter with a "0" to 200 the frequency deviations into amplitude limiter -tube grid resistor. microampere range. variations. Adjustments are made for maximum read- 16) A.C. and D.C. voltmeters with range Trouble in either of these circuits can ing of the "0" to 200 microamp. meter main- scales of "0" to 1,000 volts or more be located in the usual manner but realign- taining the center "0" microammeter at "0" and a resistance of at least 1,000 ment must be carried out in a new and at all times by rotating (rocking) the re- ohms/ volt. different way and it is essential that the ceiver's dial slightly back and forth. (7) Ohmmeter capable of indicating re- manufacturer's procedure be followed exact- Some of the troubles which have been sistance from "0" to at least 10 ly. In fact, since alignment of frequency found in the field are as follows: modulation receivers megohms. is carefully made at Noise: Defective tubes. the factory with special equipment designed NOTE: The meters for this Poor antenna systems. listed do not neces- purpose, ordinarily no realignment Leaky sarily have to be individual is necessary. or open bypass con- meters. Many However, on rare occasions, it densers. manufacturers of test equipment combine may be necessary and, therefore, a more these meters into one combination unit or less general description of alignment Regeneration: Chassis wiring not dressed which is very satisfactory. procedure follows: properly. Loose ground contacts in PROCEDURE ALIGNMENT chassis. Circuit diagrams, charts, instructions, etc., Each I.F. and R.F. stage in frequency Open by -pass condensers. for locating and correcting trouble are sup- modulation receivers should be adjusted in- Distortion: Limiter circuit not func- plied by the manufacturer and the usual dependently and no overall adjustments tioning properly. procedure for such fault- finding should be should be made. If the receiver is not in Incorrect realignment. followed. Remember, however, that these proper alignment after adjustments are Defective audio circuits. circuits are high- frequency, and the unit made, start over again. salues This article has been prepared from data and locations are very important. In Adjustment of the discriminator circuit supplied by courtesy fact, because of Stromberg- Carlson of the high frequencies and is made by connecting a center "0" micro- Telephone Mfg. Co. 266 RADIO -CRAFT for NOVEMBER, 1940 TYPE D ALL -PURPOSE CONTROLS HandlQ 60% to 75% of LL"REPLACEMENTS

...The All -Metal Cabinet is Included - AT NO EXTRA COST! Now, for the first time, you can purchase a stock of only 18 Controls, 6 switches and 5 special, extra shafts ... and be prepared for quick, efficient service on more than two-thirds of the radios you are called upon to repair! You save time, because it is no longer necessary to order a TAP-IN control every time you need one! You simplify installations be- SHAAFTS ray /'U t cause IRC Type D All- Purpose Controls with their Tap -in Shafts are easier to install and can be used universally to replace Type D All- Purpose Controls are exact reproductions of the larger midget size or larger, old -style controls! You save money -and IRC Type CS Controls, with exactly the same design, exactly the you assure your customer of a first-class job ! same features and with the added convenience of Tap -in Shafts. Just pick the control you need, select the proper shaft, tap it into Best of all, you pay only the standard price for the controls, position in the cone -shaped control receptacle following simple switches and shafts. The handy new IRC Master Radiotriciaá s instructions enclosed with each control, and the job is done. The Control Cabinet, as illustrated, is included with your purchase the quality of shaft won't pull or vibrate loose -and you're sure not one of extra cost. the control is the highest money can buy. at cent The Cabinet itself is of all -metal construction. Attractively decorated, it is an HERE IS WHAT YOU GET! asset to the appearance of your shop. It is 14'.s" x 71/4' x 4 ", weighs approx. 6 lbs. complete. IRC Control numbers are marked underneath each compart- s is factory -packed with The IRC Master Radiotrician Cabinet ment so you can tell at a glance just what values should be reordered to keep the following 18 Type D All- Purpose Controls, switches and special Three drawers supply ample space for shafts, switches or to be capable of your stock complete. shafts of the most popular types shown by records other spare parts. Front metal cover snaps securely shut for carrying, or may handling the big majority of all control replacements. be removed when Kit is used in your shop. The regular net price of the 18 Con. is in- lit Cuttet Typs Nn. Ruhmset lotion INC Cutrsi Typs Ni, INSWING Pstlsss trots, 6 switches and 5 special, extra shafts is $14.97 -and the Cabinet 2-013-133 500,000 1-013.133 X . . . . 500,000 cluded for not one cent extra!

. . . 1-011-116 . . 10,000 1-DC13n33 X 300,000 .G 1-011-123 . 50,000 1-D13-137 1.0 1-011-121 . . 100,000 ..c 1-D13-137 X . . . 1.0 CO. . . 500,000 c INTERNATIONAL RESISTANCE 1-D11-133 1-D13-139 2.0 .A 1-1)13-143 . . 50,000 401 N. BROAD ST., PHILADELPHIA, PA. 1-D13_139 X . . . 2.0 . 1-013-141 . . 100,000 1-013-130 250,000 1-014-116 . . . Attached is 514.97.n check. _' money order (nor send C O.D.) one IRC Master Rndio- X 250,000 1-D16-119 40,000 . 1-013-130 tric'an' Control Cabinet complete with the 18 Type D Alt-Purpose Controls. 6 switches A -Tens er Audio Circuit Centre! E -Tapped far A. V. C. and 5 Tup -in Extra Shafts cs described. It is ucderetood that, ti this does not meet my lull F -Tapped for Tone Compensation B -Antenna Grid Bias Central I within 5 cnys. G -Friction Clutch Auto Radio Type approval, can rete.n .n good conditia'i - lull re..,. C -Potentiometer Voltage Divider D -Tons Control H -Antenna Grid Blas of 2 Tubes NAME_ -___ Switches: 3-No. 41 S.P.S.T.; 1 -Ne. 42 D.P.S.T. 2 Shafts: 1 -Type B Auto Radio; 2 -Type C with stetted, knurled terminals; -Type D with stoned unknurted terminals STREET

Dealer Net en above controls, 6 switches, 5 shafts - .. 1497 CITY --STATE THE CABINET IS INCLUDED FREE!

Nance of your regular jobber City

(Jobber's nome must be given to State secure net dealer coat shown)

RADIO -CRAcT for PIOVEMBER 1940 251 SERVICING

PLATE 2NO.I.F PREAMPLIFIER 6H6 D15CRIMINATOR 0.1 OF 62544.7 65N1 I.F. DE TOR 0.1- 15Óv 15 -G L IST. A.F -, MEG CONTROLLED MMOF. 0.5- MEG. VOLUME CVONTROL 500 MME MEG-

I 0.75- 0.25- OHMS L MEG. MEG M IR P R.EC. 7 /6MF 65C1 75000 LIEG ppppp OHMS 4M5P' 1 CRYSTAL MIKE OHMS 100 5,000 L._ MMF. 0.1 05- I MEG. 5 MEGS. GIRCKUPL e MEG. MF NEW CIRCUITS I MODERN RADIO RECEIVERS

In this series, a well -known technician analyzes each new improvement in radio receiver circuits. A veritable compendium of modern radio engineering developments.

F. L. SPRAYBERRY No. 38

(FIG. I.) I.F. AMPLIFIER SERVES ALSO AS I.F. plate circuit to cut out received signals a zero grid in the 6SC7 input. both 6AD6G MICROPHONE PREAMPLIFIER while using the recorder or pick -up. control electrodes will be at - 75 volts and MONTGOMERY WARD MODEL O tBR -615A. both shadows will be closed. Plate voltage -A very worthy design achieving added (FIG. 2.) SUPPLEMENTARY SHADOWS IN- regulation of the 6SC7 by a gas tube keeps facilities for recording and microphone am- DICATE F.M. RESONANCE these voltages constant during operation plification with only a few additional parts MEISSNER MODEL 9. 1021 - -.4 double -acting and produces similar action within any nor- has been adopted in this circuit. indicator eye tube type GAD6C indicates mal line voltage changes. Instead of a complete additional ampli- zero D.C. voltage at the discriminator out- As the 6SC7 input grid becomes negative fier with an additional tube, with its added put by wiring such that one shadow will due to off- resonance action of the dis- space and transformer load, the lust I.F. expand as this point becomes negative while criminator, the plate of the 6SC7 input sec- tube is used as a microphone preamplifier. the other will expand if it becomes positive. tion goes more positive and the shadow due The circuit, shown in Fig. 1, is such that The best test of tuning in a discriminator to the ray control associated with this plate no substantial sacrifice need be made for is the D.C. voltage on the output cathode already being closed does not change. How- either of its 2 modes of operation. Being of the discriminator. This voltage is zero ever, decreased cathode current reduces the resistance -capacity coupled to the preceding only at resonance when the circuit is in bias on the other triode section causing its I.F. tube its grid circuit remains virtually proper adjustment regardless of the carrier plate current to rise and its plate voltage unchanged by the addition of the micro- intensity or whether or not it is modulated. to fall. This causes the shadow associated phone. Operation of the resonance indicator is with this plate and control electrode to In series with the tuned I.F. load in its based on this fact. expand. plate circuit there is a resistance A.F. load As shown in Fig. 2, the voltage at the A positive grid, on the other hand, will 175,000 ohms) and a 0.01 -mf. condenser output cathode of the 6H6 discriminator cause the other shadow to expand and allow coupling the A.F. into the A.F. selector is filtered practically to D.C. and this volt- the former mentioned one to remain un- switch point. For both I.F. and A.F. am- age is introduced into one grid of a double - changed. Correct tuning is obtained when plification the bias of the 6SJ7 is made triode 6SC7. The plates are individually re- bot h shadows are closed. slightly higher than normal so as to permit sistance loaded and the single cathode has high voltage in the plate. The gain of the a bias resistor in it. One of the plates is (FIG. 3.) ANTENNA TELEVISION INPUT stage is great enough for either I.F. or A.F. directly connected to the shadow control so EMERSON MODELS DP -332 AND DP1.332.- that a small grid signal is sufficient thus electrode in the 6AD6G tube while the other Here is an ingenious avoiding idea showing an ar- distortion due to large negative plate is indirectly connected to the other rangement which allows us to dispense excursions of with the grid. Ganged with the control electrode. the entire audio system including the audio audio selector switch is a swit ch in the 1st Circuit values are chosen such that with I.F. system in a television receiver.

05A7 651.7 10.000 OHMS, 05ILLATOR TO R.P MIXER ANTENNA CIRCUIT 1 G

I R.FC. 100 ro MMn! CONTROL GRID TO OF A.V.C. 61.SGT OSCILLATOLA' MIXER

41 47,000 i r OHMS O OHMS

ME- 1,000 OHMS

TO 4.5C 268 RADIO -CRAFT far NOVEMBER, 1940 SERVICING

Instead of using a complete I.F. and 2nd - detector system in a television receiver and then picking up the A.F. in a manner similar to that of a phonograph pickup connec- BRIGHT STAR PORTABLE tion, we may connect the antenna of this circuit, shown in part in Fig. 3 to the 1st - detector output of the television receiver. With the television circuit oscillator a beat with the voice carrier will be produced of RADIO BATTERIES say 8 mc. This receiver is simply tuned in 8 and this its high- frequency band to mc. of power supply for all types of Portable Receivers. beat frequency is received as any other A dependable source muy be S mc. signal. Adequate shielding -long associated with BRIGHT STAR direct pickup by the re- The highly efficient "bag type" construction needed to prevent of internal short circuits. ceiver but this is hardly more than would quality batteries -eliminates possibility receiver nor- be required in the television Special inner casing safeguards battery life from harmful effects of moisture or damp- mally anyway. ness when receivers are used outdoors.

(FIG. 4.) UNUSUAL TRIODE 2ND -DETECTOR Constant laboratory control over raw materials, APPLICATION manufacturing processes and finished product SII VERTONE MODELS 6321, 6124, AND 6493. assures high quality, uniformity and top per- -While the control -grid of this triode is formance. used as usual as a diode plate in I.F. rectification for the audio signal, the triode plate is used as a diode rectifier for pro- Build your battery sales with ducing A.V.C. instead of being connected to the cathode as in the usual case. BRIGHT STAR - The circuit connections are shown in Fig. for profits and satisfaction. 4. Due to the plate to grid coupling using a 50 mmf. condenser the plate and grid I.F. potentials are substantially in phase FREE!.,. and hence, unlike the usual diode circuit, A comprehensive Replacement Guide, the conductivity of the plate diode is in- showing recommended BRIGHT STAR on positive alter- creased by the grid action for over 700 models of port- nations without a corresponding increase in Batteries load on the tuned circuit. Because of the able receivers, is available. Send for in -phase operation of the 2 elements (grid your free copy today. and plate) the performance of one does not adversely affect that of the other.

(FIG. 5.) SERIES- COUPLED AMPLIFYING BRIGHT STAR BATTERY CO. COMPENSATOR Executive Offices and Factory: Clifton, N. J. GENERAL ELECTRIC MODEL J- I05, -An im- Chicago San Francisco Houston pedance that varies with frequency is placed in series with the R.F.-to-detector coupling Actual Size 4!s' by 9r,íí condenser so that the energy transfer re- -272 fact -filled pages mains reasonably constant for all bands in this receiver. Formerly used in series with the R.F. Big plate circuit between the plate and coupling Get Your Copy of the condenser, it is now placed to allow a direct plate to active load connection. The coupling network as shown in Fig. 5 allows for a change in energy transfer with frequency is more SYLVANIA of the order of 15 or 20(4 which nearly commensurate with the other circuit and tube characteristics which are inverse to this. The other method permitted several lute `Tact iloOK hundred per cent over- compensation for circuit characteristic. 272 Pages of Vital Tube Information BOOK REVIEW Including 1111111111110 010 01111110 11 0 0 0 0 11111 0 11110 110110 0 1OIW0 1 11110 0 01111111 1940 -1941 AMPLIFIER HANDBOOK AND PUB- LIC ADDRESS GUIDE. Published by Radcraft Operating Conditions Publications, Inc. Size, 6 x 9 ins., stiff paper cover, over 75 illustrations, AO pgs. Price, 25c. Tube Characteristics and "Amplifier Handbook and Public Address Guide," published last month, was prepared by a Circuit Applications on practical sound man. Printed on glossy paper HYGRADE SYLVANIA CORP. it is a convenient pocket-size book crammed with 374 Tube Types Emporium, Pa. RCIIO information on the newest developments in the sound field. Approximately 20 companies special- Enclosed is 35c. Please send me n valuable ropy of the latest edition of the izing in sound equipment contributed Sylvania Technical Manual. information which the author has incorporated in this book. Not a laboratory manual nor an engineer's USE THIS COUPON TODAY handbook, the 1940 -'41 Amplifier Handbook and Name Public Address Guide in presenting essential information and practical data for all sound men and P.A. specialists, offers to the technician who Address makes his livelihood by estimating, installing, maintaining and servicing public -address equipment a useful daily reference book. book is divided into Sections as follows: SYLVANIA City Sbeue The Experimenter I- Source : II-Amplifiers: III -Distribution Set -Tested Radio Tubes Serviceman IV- Coordination: and. V-Useful Public Ad- ,rj Dealer Amateur dress Data and Information. RADIO -CRAFT for NOVEMBER, 1940 269 SERVICING

Radio Service Data Sheet 292 CROSLEY MODEL 29BA RADIO - PHONOGRAPH COMBINATION IChassis Model 29) 8 -Tube Superhet.; 3 Bands (550 to 1,600 kc., 1,600 fo 5,000 kc. and 6 to 18 mc.); Built -in Rotatable Loop Antenna; R.F. Amplifier Stage Pushbutton Tuning for 5 Stations; Bass Compensation; Tone Control; Automatic Record Player; Crystal Pickup; Delayed A.V.C. 9q

roa Leer

MODEL --29 455 KC. I. P.

Alignment Pruvedure.Connect the output meter- front plate the signal -to-plate of the G}`Gs. Connect generator ground lend to the receiver chassis ore ground lead. Specified dummy antennas should he inserted in series with generator output. Position of volume control should In. full -on: 11,11t. control in Trail,. Align in following none rital order. Number Signal Generator Inoue Connection Band Dummy Antenna Tuning Cond. Trimmer Re- Freq. Setting to Rereierr Sitr11 Setting Adjusted mgrko III 0.2 -un. 2nd1st 121 93: ke. ,rid of e.\l:'l' 1:.1 . Fully Imam 1st TV.LP (_"1 (A) 121 250 aunt. I i5ii ke. .\ ml. lead (blue) li.r'. ILr, 'OFI - Fully inn s Trimmer 13) rs.t 211n mmf. e.0u kr. Ant, lead (b;nt) 10.C. .lnprnx. r,lr vrrhe... (C) nu Jial Trirnuur 19) Itrnrm Step No. : b. cheek possible shift due to series adlu.tuneut

2011 ID) 15) lour. 1,100 ke. .tin. lead (blue) 1L/'. Approx. Ile o i dial I1.l'. IL F'. Trimmer (A) 'ou ila'` (GI (carbon) 5.3 me. .tart. Ica,) (blue) Pollee PuII nain l'on "Ilur" III) :nn ohms Vol ".5.'r'. 171 ue. barium/ 5 Ant. lead (due) Pollee Approx. 5 and R.F. (CI m isi itiil(lIt'll Tl homes iuu ohms Location 1.1 I,arl.nte rs. m . .tut. had (bine) S.W. FOGY elan g.\\'. "OS, ¡BI of main components and I.F. trimmers. S.W. Ina mule .t) Is un. \ul. lead 1, I B.F. urb,nl. thine) S.W. .tpProx. IS Trimulrre IC) 'BE3I.tltKs, .tolet for the fnllou lug Utttpute -IA) \lay. 11:. Ptah; pot tl,e05 lev In rock conk. ICI)Inx.: male Kane. 1111 ]lax; lame B.C. pert trimmer um oiii,, d.

Important Notes. - \\'hen aligning die nlmrncave. huai -0SO" Irinlmrrs sail, mint be eyerelsed to nee that the torahs are S.W.(J C` S.W. aligned on /lie eneteet teenernee nod not nu the image 11.-F is whirl) 05C +pures. Pin ke, 10., as Indicated on the dial. To ,hark. .rease gener:hm' 010ninth. SHUNT B.C.e i'POL $NUNT Im,t -In general. fregu. n,)' and TRIMMERS then tune -lo huas, fl'r.pnney uidrh should TRIMMERS7 Inc be weak,. than fundaunl,lul of P0110 :OWN, 1110 lie. lower on the POL.g B.C. dial than Ille fUUdauelh l. If Image cannot '-ORC" trival:er he time,. in. the I. u.t)nstr,t to the 5 mea k. n...erect peak is tir 21,1 P, sic s, trimmer from s i the elna -.l po. idea.) Repeat 011clona `. msdur, uwr ,urate adltis nenl.s .ths Acne output a hay RI Location of aligning trimmers. prsstine In era 111 1011 In " :let 10p or he . .pe1.o.

Socket Operating Voltage,' ollaaes measured to rltassls (d 117.5 -V. line. with 1.000 ohms /volt, 500.V. range D.C. meter Pin Number 'l'I'Ii F: i't N, "1905 1 ' K,r.F, tmu. o o 1.- - 0 J.B. 9113 S - n,nd. 0 n t.: n 130 d5 1 uS197-0.o..K; -LF. :Imp. n n n 2.3 1ßU7 -2 t- 11eí.- A.\-.C.A.P. n UJSr.T-- 0 u 110 et .3 Y O PI,:no Tntro 0 n lye_, 0 0 .LB, 0.3 ' *StO onrnn. n it 220 2:01 0 .I.B. 0.3 14.5 r,Fr;O - Ihcput n 0 5Y30 290 0 .1.11. 911.3 19.5 -Ii rt. NI' 3.9.0 Lit. '3 T(,0 J.B. 1115 J.B. 329.0 Men-ire with A.G. Creole). model 298A phono- radio. voltmeter. 1.11.- Jm,Onn hin.k. N.V.- -1 o m next toll. Max. power nntnnt (q5 117.5 V. line 8 W. l'mcer ton. ongmlou O. 117.5 85 W. \'. line loon : : +n - y.ruko r nel9 95 V. Voltages may sail' 10? of velars given.

270 RADIO -CRAFT for NOVEMBER, 1940 SERVICING

OPERATING NOTES BUY DIRECT FROM THE MANUFACTURER AND SAVE New roua with . Announcing for the First Time -The

.. . EMERSON T A common complaint of this set is "oscillation" when the tuning condenser is rotated DYNAROMETER and when the set is jarred. New Giant 8 Double Jewelled Meter The tuning condenser in this set then is Features usually not making a good mechanical con- versatile instrument is the This amazing nection to the chassis. Simply bonding our answer to the demands of radiotri- will elim- tuning condenser to the chassis cians for a combination instrument inate this trouble. Also check the filter and to making the usual defects. which, in addition cathode condensers for possible V.O.M. measurements, will also permit DYNAMIC D.C. VOLTAGE MEAS. . . EMERSON "MICKEY MOUSE" UREMENTS without interfering with A frequent complaint of this set is "motor - or upsetting delicately balanced cir- boating and oscillation" when the volume cuits, such as tuned circuits, electronic control is turned upward toward maximum. control voltages, etc. Ac. replace the apparatus, To correct this trouble, tually, as you will note from the speci- screen -grid bypass condenser. This is one below, the DY'\ block. The fications listed section of the filter condenser ROMETER is a combination Vacuum best thing is to replace the entire filter Tube Voltmeter and V.O.M. l.- will pay in the long run. block as it permitting additional measurement - such as Capacity, Decibels, Inductance. .. EMERGENCY DIAL CORD etc. calibrations printed in large. method of All Many times I've used this easy reading type on the giant 81V2" replacing the dial cord on a receiver. Some- double jewelled meter. The Input Ins. times it's hard to obtain a dial cord for a is 11,000,000 re- pedance for the V.T.V.M. certain set or it may be all emergency 2,000,000 ohms per volt on a good ohms with pair. You can save many customer's range. The 4 V.T.V.M. method. the lowest will by this simple ranges are 5, 25, 100 and 500 Volts. Simply get a piece of ordinary string no string and because of the zero center and some bees -wax and draw the attention need be paid to polarity across the wax a few times back and forth will read either in the the strongest and since the meter and you'll have one of plus or minus direction, depending on most reliable dial cords. the position of the probes. HAROLD R. KUNTZ, Brooklyn, N. Y. HAVE YOU EVER . - REMLER 36 AUTO RADIO Tried to measure Control Voltages such as A.V.C., A.F.C., oscillator, etc.? Noisy reception such as interference (or V.O.M. due to loading of the circuit BUT the It megohm Impossible with the ordinary molestation hash) may be caused by an opened filter input impedance of the DYNAROMETER enables measurements without condenser (0.05 -mf. and 0.1 -mf.) in the 3t any point in the receiver. or Tried to locate distortion in the audio section of a receiver? "hot" battery lead into the dynamotor, instantaneous with this new choke. Replace the defec- A long tedious job with the ordinary Y.O.M. but almost a defective R.F. method of testing. component. Low -volume output fre- DYNAMIC tive Tried to isolate Me cause of trouble in an intermittent job? quently is traced to the 2nd A.F. plate re- possible with the DYNAROMETER, but because of the extreme sensi- Not only is this with a V.O.M. sistor having increased in value, thus caus- tivity and flexibility measurements are possible at points usually impractical ing a drop in the plate voltage of the 76 2nd A.F. tube; the value of this resistor SPECIFICATIONS: is 15,000 ohms. This model has 3 stages of INPUT: D.00. CURRENT MEASUREMENTSIN 4 RANGES: A.F. 4 D.C. VOLT RANGES AT 11 MEGOHMS EMENTS 0 -5 25/100'500 Volts IN 5 RANGES: OUTPUT D.C. VOLTAGE MEASUREMENTS 4 AUTO - (at 1000 ohms per volt) .... HOWARD HIGHWAYMAN 2 CAPACITY RANGES: 0 -TTI 502SO'5oo /5000 Volts RADIO A.C. VOLTAGE MEASUREMENTS IN 4 RANGES: 1 is reported inoperative, 000 ohms per volt) Mfd . If this receiver approximately INDUCTANCE: 42 0. 15/150 -'1500'3000 volts . the trouble may be caused by the power 1 H. RESISTANCE MEASUREMENTS IN 3 RANGES: H.-70 having 10,000 H. tube input grid coupling condenser 0.1,000 Ohms, 0. 10,000 Ohms, 0.30 Megohms. 7 H.- 0.01 -mf., volt- opened. Replace with one of The operates on 90 -120 Volts 60 cycles A.C. Comes complete Q 0.J Dynarometer weight 20 lbs. Size Y age rating 400. Then, if there is no control with(at tent leads and all necessary instructions. Shipping of tone, check for a defective tone control irit,'x10 "xo," . Our net price switch; replacement with a new tone control switch will cure the fault. C0.136 LNi Nt.1RC -11 SUPERIOR INSTRUMENTS EWtYORK, . BALKEIT 100 Failure to operate, or interrupted reception, frequently is caused by an open choke. A NEW BOOK ON PUBLIC ADDRESS subjects appears on Replace, and at the same time check con- announcement of sound and allied An important NOW! densers C11 and C12 for short or open; if Pass 315 of this Isms TUR TO THE ANNOUNCEMENT either, replace C12 with a condenser rated V. instead of the usual 400 -V. one at 600 ALL YOUR (capacity 4 mf.). Interrupted reception may also be due to the 56 oscillator not func- RADIO NEEDS tioning. Continued blowing of the A.C. line FItEI;! Here in This one big book fuse sometimes is due to a shorted power you will trod everything you need in radio ... sets. parts transformer primary buffer condenser, HAMMARLUND and supplies ... public ad- value 1 mf. Be sure to replace this con- NEW dress systems ... amateur denser with one that is non -inductive and '40" equipment ... teeters and RADIO CATALOG kits . your nationally of sufficient voltage rating. known favorites at lowest Write The latest Hammarlund catalog with possible prices. .. GRAY BARETTE 4- MIDGET complete data. illustrations. draw- today for this big valuable This set is a dandy when it is working ings and curves on the entire Ham - catalog and save money. right, but has a common source of trouble marlund line. Address Department PROMPT SERVICE in that this model may develop an open R(' -lit for your free copy. or shorted 1st R.F. cathode bypass con- HAMMARLUND MFG. CO., INC. denser. is best to replace the whole unit: It 424.430 West 33rd Street. New York City BURSTEIN - APPLEBEE COMPANY in 1st cathode - this takes the R.F. cathode, STRUT, KANSAS CITY, MISSOURI (Continued on page 273) 1012 -14 McGEE RADIO -CRAFT for NOVEMBER, 1940 271 SERVICING

293 Radio Service Data Sheet

EMERSON MODEL DX -356 3 -BAND MANTEL SET 1 Chassis Model DX) 5-Tube Superhet.; 3 Bands (540 fo 1,750 kc., 2,300 to 7,500 kc. and 6.9 fo 22 mc.); 115 V. A.C.; Automatic Volume Control; Consumption, W.; Power 55 6V6GT Output; Tone Control; Built -In Electrostatic Antenna (termed an all -wave loop antenna). EXTERNAL ELECTROSTATIC 1 Fr ANTENNA 65a7G7 1 65KI F T I CT 2 Bj))Q](;( i (IN CABINET) / MIXER 6V6GT. SPEAKER Paw[R ll, -- /l2 i1.Ai 4007 eeEAMOUTPUT 111 %4-w - t i Á VOICE -- ..v..\: - - 7r _ _ 4.w I / . . / CO,L

( Oh i MF 4pW OUTPUT TRANS. (LOP r .05-Mc 400V. JVMPE9 L l5 0000 -ÿ00A T / 3w. t B. ANO s1ÓßN .25 -MEGI M fw.1) '/4 -W. 400V PT

16MF / 450V 5v3G

.002_ RESE VIEW OF WAVE ` c90 ¿p LR.F.CL 7 BAN ',sw. (SW IN B C COIL POSITION 16MF wAVETRAP ) 400v. ANTENNA 4405 TION L2aC. POSITIONS TONE CONTROL LOADING COIL SHOWN IN CO MAX. BASS POSITION. (VIEW LOOKING AT CoTRIMMERS 150T0 Net BROADCAST REAR OF LwTCNI MART OF OSE SOOMMF NEB. POLICE ta0n > 23JL COIL ESEMBLT) NI 3. SNORT WAVE ) -1 LW /B. W CA TRIPLE TRIMMER STRIP e FOR ANTENNA NUM NEUT41L1211G I.F 455 KC. TO 1l5T RESyTOR, 4r-OHM AC DIAL LIGHT Complete schematic diagram of the Emerson model DX -356 receiver (chassis No. DX).

Alignment Procedure Nadler for usas. ras panse. Return to 1.6110 Culree 51:W I.pper.

Broadcast - Alignment. Set wave -band formers is as follows: grid, Wu.: "Ii -. ", red; switch at broadcast l clockwise) position; l;eneral Notes plate, bl.; grid- return, bl'k. pointer at 60. Feed 600 kc. tri antenna )using II) The color coding of the power trans- standard dummy antenna) and broad- 111 The receiver should never be turned on adjust former is as follows: pri.. 2 bl'k. leads; cast -band series with either the speaker plug or the 11V6GT padder (beneath the chassis II.-V. sec., 2 red leads; IL -V. set. C.-T., red in the rear of the variable condenser) tube nut of their respective sockets, .since for & yel. lead ; 6.3-V. sec., 2 gnu, leads; 5 -V. max. response. Move pointer feed the rapid rise in re,tifler voltage will damage to Lin, s e c . . 2 yel. leads, 1,600 ke und ose. the electrolytic condenser. adjust roil trimmer, then 15) When replacing C20 ant. coil padders and C29 trimmer for max. response. Re:et (2) When replacing the chassis in the cabi- Ito sure the tolerance is within 2C, of the pointer at 60. 600 feed kc. and rock the net take precautions to keep any part of the specified value, otherwise the shortwave coils veriablo condenser while adjusting series dial and condenser assembly from touching any not track.

272 RADIO -CRAFT for NOVEMBER, 1940 SERVICING

(Contioucd from pane 271) THE MANUFACTURER AND SAVE to- plate, and cuthode-to- screen -grid con- BUY DIRECT FROM denser. THE NEW MODEL 1240

. , MAJESTIC 380 an occa- TUBE TESTER "Low volume or sometimes dead," snap switches sional complaint with this set, is usually Instantaneous unit being open reduce actual testing time caused by an audio bypass minimum. or shorted. Replace with a new, can -type to absolute condenser. There are 3 condensers in this Tests all tubes 1.4 to 117 unit (capacities: 0.03 mf., 500 mmf., and volts. 0.01 -mf.l, Sockets for all tubes - No Adapters. . . FREED- EISEMANN FE 15 -18 This is a battery model, and sometimes Superior is proud to offer the new- has a heavy "B" power drain. The trouble est and most practical tube tester is caused by a leaky 0.1 -mf. bypass con- over designed. Unbelievably low in denser acro.> Ole "B "- battery circuit. price -unbelievably high in performance. . . WESTINGHOUSE 12 * Teils all tithe.. 1.1 to 117 Volts. i circuit is used in this eluding 1, ; G, 7. 71. wilds. total. "/!111I111I A superheterodyne natlpml .1r., l'Mercu singles ended. now set. If inoperative, it may be caused by an Inc slew MercuryIn Vapor 1 every secondary wind- the series. 111 fall, eyrry lu' open 1st I.F. transformer .p i' I to date. ing. Replace, and also check the 1st R.F. * 9r :u socket Included on front Dæ:.:1 resistor for an open, or for any fut uro tubes. 8,000-ohm cathode *Tests by the \fell- rsn,hlished emioh Ti an increase in value. melliot roe ntl,. quality directly read n Ile 00í1U t HAD :gale or the metes. OFOR(:E F. BAPTISTE. * .Tenet neon. R. I. protected Howard, * Pest shorts and leakages ut. to 2 me;: "lino in all tunes. * Teets leakages and shorts in all elrmcut AGAINST all rl, unit i in 511 . . CANADIAN WESTINGHOUSE * Tests BOTH plates in rectifiers. RECEIVERS *Tests iudl\idual sections sutil as (tales, males. prldales, etc.. in multi -Pulpus Iola. changes * E:dcst type Voltage regulator. The following are production * Mixtures an at t rari ire etched aluminum D..uel. which have been made in certain radio sets * works un 90 to 123 Volts 10 eyrie. .l.('. Model 1240 comes complete with instruction: and tabular data for es:ry known in this line. type of receiving tube. Shipping weight 12 pounds. Sire 6" x S I," x 11W,", Model W -651 Y (serials above A- 236971- Our Net Price -This model is the stone as model 651 -X Portable cover 53.00 additional sr with the addition of a dial escutcheon, part No. M 16730. A resistor of 39,000 ohms has THE NEW MODEL 1230 been added in series with the high end of the volume control and the common connec- SIGNAL tion of the 2nd I.F. secondary (L121 and resistor R4. Condenser C14 is left con- GENERATOR connected to the high end of the volume WITH OF trol in the factory diagram. This change FIVE STEPS was also added to some W -651A and W -651X SINE -WAVE AUDIO receivers and stops I,F, signals or oscilla- tions from entering the audio circuits ut SPECIFICATIONS RADIO FREQUENCIES ,'fil lao tit'. to 90 sw1,11 full volume. Veca,,elrs i 7 bands by front panel :lad :,,vale tO \1 -035 A (serials above 23797 - .odpulati'a,n All direct reedit,, Model t.''th111 ,fil I.I' and Si madr:,-1 lint 11, 2.1 on I'r sep The 2 left -hand phono. switch contacts (as higher ue,tmraele,. The tt.F. i ,o al,, :11,11. close the eaten' or malulated by any ontot` Ise fisc .sotto seen on schematic) are used to F'tr,meufiet. "B -"supply to the W-6SA7 oscillator plate AUDIO FREQUENCIES: 5 steps of SINE- w.t\'F: null _on put, 190.1. :.0 r veby WITH and the \V -6SK7 R.F. screen -grid in the OVER "Radio" position and to open these circuits hitvO inr I, ÌbrtrratÌa,d.'Iae1' -(r v (nre /ring Ií.5., hard- of- hearing on "Phono" operation. ATTENUATOR: Late design. full.r ago valor recd for I,xllndlin;: either the pure T ILE. The broadcast oscillator circuit condenser. . :hoed Il. same capacity as before (15 ?cillalor circuit for rl,e ILI% affording plAtlee c7, has the CIRCUIT: The Model 1230 employs an I o'rnc.l tile. tom reupled o, -compensating frequency If II di Ly u.i;Llwr rlreuit for the ,t. E. srrOLll. annf.) but is a temperature n fnxrt hand, uéb,g a n,,, Inaehanlra.l> prrta-trii DIAL (MANIPULATION: eii..l Ird ih rt,li' , type No. 594768 -8). The 1.0- megohm tri te for perfect t'nitr control. 1 (part s in a lifedrng auraotite front lied nrrntly prrttrled p , _. "luth rn>ul Clé referred -to in the sche- APPEARANCE: 'raldn. I. resistor across The t ornes l- tit, 9r a1 ndiurd Plllrldr,l Or e'. any 1 r'raotN i. . volts t.C, II. matic 18 used. CURRENT SOURCE: Tho Model 1230 ope '- 90 to 130

Westinghouse Model B -562A (serials The Model 1230 comes complete wit: I ahie1,1, +1 enfile;, nun ltl,,t coming potin, Is. ONLY $1285 1 weight 13 above A- 27197). -Molded condensers C6 and handle and instruction:. Si .t . . Phil ping ('7 have different values from earlier pi o Unit ('6 w'as 4.7 mmf.-changed to 136 eNtYRC -11 duction. LNEW YORK, 8.2 mmf. Unit ('7 was 12 mmf.-changed to SUPERIOR INSTRUMENTS CO. 8.2 mmf. Condenser C'4 (0.01 mf., 400 bolt is not used on this later production. () no A.V.C. bias was lip PoPIiI.:%It Pit ICE earlier production WITH REAL MUSICAL QUALITY' plied to the I.F. tube type W -1N5C. On this tube has the saune DEAL O,R the later production PRICESES A.V.C. bias as the W -1A76. To effect ti the winding L -14 is not connected to ;;cou. but the previously grounded end i- fleeted to the common point of r, na r ,af oo,,,., R6 and R7. t. Free I!,J 1 1 rain talt,g Ott- - I CANADIAN \\'F:3TINC114 st: Co. ÌallnrcA 10-day hi Hop, iIt,,,', (',rit, GOLDENTONE RADIOADIO CO.. DEPT. RO. DEARBONM. MICR.

"FREQUENCY MODULATION AUDIO AMPLIFIER" OLAt 11 ED-CAPS to hrr Smalier D ameter Dry Electrolytics e :aring > need li s nt It. le t I te ",en looks Mon. f t keel. k r 1.r. 00,1Iili, ' t, Ìíh ti freaan y Snore. ',v,vrI.1 II ° 111,11, _,_ uH n t h flat, tupi a noise level SPEQ eoonsed IIIt i 111 fidelity SI -ittlieientlyfile low. to afford maximum fidelity I 1 I t 111 1 1 1 .'I 11 Ihnh tel 1 1 .. I v i o l my imum fin'k::round noise for full ap- 0 rrl r+t 1 t. ..r, }1h ans'ren. r.., of F.M. , look for t i u - to vF:ie ne.,l.,. prerirltnal prolran, wrote lo, Catalog CO - W ' t MUSIC MASTER MANUFACTURING : , r t i r t e Ft December fled fo.f' r,! f- -tin the net.- 508 South Dearborn St, Chicago, Illinois. -Lmds N e -t'ih. r 1 - SOLAR MPG. CORP. Bayonne. New Jersey RADIO -CRAFT for NOVEMBER, 1940 273 SERVICING

Radio Service Data Sheet 294

HOWARD MODEL 520APC RADIO - PHONO COMBINATION 12 -Tube Superhet.; 3 Bares (540 -1.700 kc., 2.2 -7.5 mc. and 7 -22 mc.); A.C. Operation; R.F. Stage; Built -in Loop Antenna on Broadcast Band; Pushbutton Tuning (6 Buttons, Mechanical); Power Output (max.), 17 W.; Automatic Volume Control.

. C-F5GT

ANTENNA

,nF _ 100 ..,..... aw s, ..I,tee R E, C NNKR o vetted 4i,6. .0 ..E. WEAERK ,100 Gp ÓR o» As 4. 6L66 `r".. 7FTTEj'o Mtt MEN. (ras ^1.F.465KC.", Diagram, Howard model 520APC phono - radio. First (left) section of Vol. Control is coupled to the 6F5G1' through a 0.02 -mf. unit. Note dummy antenna clip "R.F. lead" should read "I.F. lead "; choke CH. measures 20 microhenries. +ANTENNA SOCKET VOLTAGE READINGS SECTION'. Voltage taken from ground with line voltage at -117, A.C. High -voltage reading off rectifier -435 V. Drop across speaker field -75 V. Voltage taken with 1,000 ohms /volt meter. Tube Func- Plate Fune- fion Tube Lion K S. -G. Plate R.F. 6F5 6GT' 31_ 100 250 CT Audio x x 60 Rt4 6A3 -Re Mixer 4 250 6F5 IeMC. GT 100 OPI35 CT Bass B. x x 116 6SK7 1st I.F. 6 615 100 250 CT Inverter9 x 195 61.6 6SK7 2nd I.F. 6 100 240 Output 1615 250 G 360 - R. F. 6J5 614 SECTION 2nd-Det. x x x 161.5 GT G Output 250 350 L<ÓÓKC. U V ALIGNMENT PROCEDURE o Wave Tri mrne,a s=0 -Band Position Gen. Gen. See Adjusted Trimmer Sw. of Dial Freq. Conn. Note (In order Function Pos. Pointer shown) o B.C. Min. Cap 465 kc. 6A8 Grid A. E 11 12 13 14 I.F. 15 16 w0 o o o KC. SW. IN Inc. 18 mc. Ant. Post B. D 07 R8 A9 Ost,. R.F. Ant. SELLATOR PB. 0.5 mc. 6.5 mc. Ant. Post 010 R11 Al2 Osc. R.F. Ant. 44S Location B.C. 1,400 kc. 1,400 kc. Ant. Post 013 R14 A15 Os.,. R.F. Ant. of alignment trimmers. B.C. 600 kc. 600 kc. Ant. Post C P16 Osc. Pad Howard model 520APC phono.$. radio receiver. NOTES A -Each step of the alignment should be repeated in the original order for greater accuracy. Keep output from Signal Generator low. The I.F. trimmers are reached through the 2 holes on the top of each I.F. can. recommended, since it is adapt- 1S -When aligning the shortwave bands, do not frequency. adjust to the IMAGE able to any frequency range. For example, if the adjustment is correctly made at 21 mc., The grid cap should remain then a weaker image will be heard at 21,000 ke. less 930 kc., or about in place during alignment. 20.070 ke. on the dial. For best results short the an- E' -When adjusting this pad, move the tuning hand back and forth, tenna and ground terminals ::nd adjust padder until the peak of greatest intensity is obtained. when using the loop on the broadcast band. D --See that the tuning hand is set exactly on the last line above 540 when the condenser is at maximum capacity. The current consumption is E dummy 145 W. for the A.P.C. unit plus -The antenna circuit shown with the schematic diagram is SO W. for the radio cha,sis.

'74 RADIO -CRAFT for NOVEMBER, 1940 SERVICING

PLEASE -MR. MANUFACTURER BUY DIRECT FROM THE MANUFACTURER AND SAVE A Plea, by Don Foard, E.E. Kalamazoo, Mich. VOL; will measurably decrease the use and abuse of profanity in and among radio :`g MODEL 1280 SET -TESTER Servicemen if you will refrain front manufacturing receivers having deep. cavernous A complete testing laL,r- chassis in which socket prongs and other ratorgi all ill one ruait. vital points are hidden from the repair- Tests all tubes, reads man's view, and in which the aforesaid A.C. volts, D.C. vital points are inaccessible to the diagnos- A.C. current, D.C. cur- tic touch of the test prod. Make our work rent, High Resistant.,, hard, if you roust -- please don't make it Low Resistance, High impossible. Capacity, Los, ( sllas- (1) Please don't ever use condenser blocks itlf, DcrILt.l$, Luhtet- again. P- L- E- A -S -E. nittv', (nad ll'nttu. (2) Why not innrk capacities and lead Instantaneous snap Your part num- switches reduce ac- codes on all electrolytics? leal testing time lu bers and private codes mean very little to absolute minimum. most Servicemen -and not all of your re- Spare socket. and listed in Rider's. filament voltages ceivers are up to 117 volts (3) As everyone knows, it is about time make the Model we had fewer tubes. And if you have any I280 proof against ideas, any ideas whatsoever, requiring new olu rdescence. it. Latest design d'. -_" or different test equipment. forget Most D'Arsonval t y p e of us like to keep our test equipment awhile, meter. housed in until it's paid for. I know one Comes at least attractive, leather - fellow who is still paying for a tube tester elle covered com- that would test 6- and 7-prong tubes. A lot ing case. new bases have passed over the Sloping panel for of tube rapid, precise sen' - counter since then. icing. (4) One manufacturer staples a circuit Works on 90 -12i diagram of the receiver to the bottom of volts 60 cycles A.C. course. make measurements accts :at ely and the cabinet. Talking his name up isn't such 'fire primary function of an in- trutne ut i,, of to the when designing test equipment tIi i. is our ti r',I, thought. However, we al -o appreciate hard work. ra nee of an in -t rument plays in the impression a serviceman makes Most important part the app.'u attention to the (5) Must you use cord driven dials? n his customers. especially on home calls. We have. therefore. paid special s. the 1.1 this Model 1290 of then: require frequent repair- -and many oulw'a rel de -ign of all of our new instrument For instance Panel ;1...1 by a radically new process. which results in a beautiful, a in the neck to fix. is made of aluminum and etc of us find them pain n,nfidenee- inspiring at/year:1n, (6) A built -in power line filter costs very little and does a lot of good. SPECIFICATIONS (7) Don't let your sales literature writers sill -, including A.1'. and D.C. Voltage and Current your 4- Tests all tubes. 1.1 to 117 go off the deep end. You tell them J, í, 6. 7. 7I.. octets. lacta! , Bantam Jr.. Ranges. tube job will get Europe-and we find it Peanut. single ended. floating filament. D.C. Voltage: 0.13. n -1S0, 0-750 Volts. We Mercury Vapor Rectifiers, the new S se- hard for them to get strong locals. date. A.C. Voltage: 0 -15, I.ISo, 1.-75r' Volt -. down. ries. in feet every tube designed to don't ask you to talk your product Spare socket included on front panel for D.C. Current: 0-1. 0 -tt, ''.1'r. 0450 ma. Just have a heart for those of us who ny future tubes. w ell -established emission A.C. Current: 11 -15. 11.150, 0 -7S0 nta. t is Tests by the must meet the customer who often read on face. method for tube quality. directly 2 Ita'sistanee ]tancer. 1.-3O0 ohms. 500 -5 bigger than we are) face to the Idlii1) ' It AD scale of the meter. megnhms. a 10 -tube receiver neon. (8) Let's quit making Jewel protected .0005 to 1 Tests shorts and leakages up to 2 meg- High and Low Capacity Scales: out of a 5 -tube receiver by the simple m fd. and Jri to Su It is also ohms in all tubes. process of adding .i ballast tubes. 'Pests leakages and shorts in all elements 1 Decibel Ranges, very embarrassing for a receiver to play AGAINST all elements in all tubes. in rectifiers. 10 to +19. well : s ever with half the tubes out. Tests BOTH plates as + Testa individual sections such as dindes. -lu to +S%, -10 to -153. We know. of course. that !lea don't make etc.. in multi -purpose triodes, pentodes, 1 '700 Hennie,. sets like this- -hut some of the others do. tubes. Inductance: to Let's jigUre apt some u',y whereby we + Latest type voltage regulator. Watts: Based on f, MW. at 0 :5.11. in 500 or Features rs attractive etched aluminum idiots .01,6000 MW. to 900 watts. ea It all make e.Orgfh to lire ire neasonhle panel. give the ertston,es his O N LY eoinfoif, and still charts. instructions. money's :r'Orti,. Model 12SO comes complete with 1rs1 leads, tabular and tabular data for every known type of receiving lithe and many Iran- milling tubes. Shipping weight IS II.. $19.95 MISS AMERICA 1940 RECORDS PORTABLE COVER $1.00 ADDITIONAL Nt1RC -il SUPERIOR INSTRUMENTS CO. 136LNEW YORK,

Turn to Page 313 for important FREE OFFER for Subscribers to RADIO -CRAFT

COI`REPAIR & REWINDING RADIO OPERATORS' SERVICE ... by coil specialists kinds. Send in defective LICENSE GUIDE IF-OSC.--RF types -alt MO OPERATORS' coils-mongrel or standard makes -old or new. Save hun- service -quality nnrk -economi- Containing over twelve time and money-quick LICENCE GUIDE fifty cal -give coil data if known -coil rewinding bulletin dred and acceptable available QUALITY RADIO COILS OF ALL answers to the new "Sic -write needs. KINDS MADE TO ORDER I or 1110-state your Element" radio operator license examination ques- BARBER & HOWARD. Inc. East Avenue. Westerly, R I Hadto e05ì neere and roil mfr.. tions as embodied in the that 1'lays the Federal Communications Woody Hernial, and his "Band Guide. Blues" is introducing a unique entertainment Commission Study in tiro Ice room of the Hotel New feature -Terrace 11111111.17 /711114111111rr Pit YOU NEED THIS GUIDE Yorker. The recorder having been set up. micro- TO PASS phones are tai -.s1 tu the guests at their table,. YOUR EXAMINATION them to sing or otherwise neaompu ny th, DUMONT inviting if not satisfactory. orchestra 1171 a honte -recording blank. Precision Built Condensers 53.00 Postpaid r funded making toe's,. records then have them autograph., at your nearest jobber or write to Wayne Miller, Suite 200 and mailed be friends or relatives. Photo ill.- Building trates Frances Burke. "Miss America 19111.' re- DUMONT ELECTRIC CO., INC. Engineering ceiving une of the "RecorDisr" home -recording 514 -516 BROADWAY NEW YORK. N. Y. Chicago, Illinois blanks (furnished by the Rec,,rDi -c Corp.) from PAPER - MICA - ELECTROLYTIC Jlar -t ru Wr!.,,I Berms u. 275 RADIO -CRAFT for NOVEMBER, 1940 SERVICING

295 Radio Service Data Sheet MITCHELL MFG. COMPANY "NAVIGATOR" GLOBE -RADIO (Chassis Models TW and TWUI 5 -Tube Superhef.; A.C.-D.C. Operation; Pushbutton Tuning (Mechanical System); Automatic Volume Control; Built -in Loop Antenna; Broadcast Band Range 55 -1,700 kc. (174.560 meters); \;T 1,712 kc. Police Band. 12A8GT 12N7GT CONVERTER 1 207G 35L6GT 1.F. DIODE- OUTPUT .01- Au.10 MF.. l ./400V. MEN 95v. 5I N. ANTENNA r COIL LOOP SPEÁMER f I 4V. 95V

(.01- MF. 400V. ó 7'v oO +95\' q« o 0.1- MF. 02- MP. (OÑVDEL 400V. .05- MF. 400V) OHMS +/:W.

0 5- "0.5- ON MODEL TW HMS. MEG. MEG.. ALL POINTS SHOWN V2 W. VOLUME 'tV CONNECTED TO CONTROL BUS ARE CON- NOTE. SHOWN NECTED DIRECTLY ARE URES TO CHASSIS. TERMINAL TO BUS. MEG_ OhiMS. VaW. +/xW. - 100 ,e, HEATER POLTAGES MN tR OHM. ARE A.C. WHEN LINE 2W. 50 VOLTAGE IS MMF ALTERNATING. -OSCILLATOR PHONO A "01- COIL TELEVISION LIE COSTRIION 400V. 0 .50 OHMS, 1:9#.

a5v 35 'Ne47 MF, 20 DIAL il'6V. 150V MF SWITCH ay LAMP mP í50P VOLUME %;- CONTROL '35.7.56T Complete RECTIFIER schematic diagram of the "Navigator" Globe-Radio receiver.

SERVICING AND ALIGNMENT DATA or other metal Poor tone near the loop. Do not make ea3HtwrrOH quality and lack of sensitivity this set -up on a metal bench. raseas may be due to any one or a combination of Connect the isr,YcLH causes test oscillator to the antenna such as weak or defective tubes or of the set through speaker, open a 200 mmf. condenser. or grounded bias resistor. by- With the gang condenser set at minimum pass condenser, etc. Never attempt to realign capacity. set the test oscillator et until all other possible sources at 1,720 kc. of trouble and adjust the oscillator (or 1,720 kc. trim- have been first thoroughly investigated and mer) on gang definitely proved condenser. Next -set the test not to be the cause. oscillator at 1,400 kc. and tune -in the signal on the gang condenser. Adjust the ) a'¡ÿkpr NOTE: It is absolutely necessary that an antenna trimmer (or 1.400 kc. trimmer) for maximum IS. accurately -calibrated test oscillator with some signal. Next set :/sOT TONI type of output measuring the test oscillator at 600 kc. -Cio:.í" srssc device be used when and tune -in signal on condenser aligning the receiver and that the procedure alignment to check of coils. e'c be carefully followed. otherwise the receiver Voltages shown on the trill be insensitive and the circuit diagram are dial calibration from socket terminals to chassis base eb will be incorrect. The trimmers will be tor bus re- on model TWU). In measuring voltages use ferred -to by their function as indicated on a voltmeter having a resistance of at least 14"At.OP,pp - p G 'r- Ta.MMLR the parts diagram. nor.sTeie.e.ìw oc G.As5,51 (L'IXÑ,GTH 1,000 ohms /volt. Allowances should be made 6,455,3) for variations in line voltage. Cha sis view of receiver showing locations of ALIGNMENT PROCEDURE AUTOMATIC TUNING (Mechanical System) tubes, major components and alignment trimmers. GENERAL DATA. The alignment of this To make adjustments receiver remove all 4 buttons requires the use of a test oscillator which pull off readily. The center buttons that will cover the frequencies of 456, 600, should be removed first since by depressing 1.400 and 1.720 kc. and an output meter to be the adjacent buttons with thumb and finger connected across the primary or secondary of a firm grip may be secured the output on either center transformer. If possible, all align- button. The side buttons can then he easily ments should be made with the volume con- removed. trol on maximum and the test oscillator out- Loosen the screw of the desired button put as low as possible to prevent the A.V.C. and with from operating the manual tuning knob tune to and giving false readings. any desired station. Hold the manual tuning CORRECT ALIGNMENT PROCEDURE. knob in position The intermediate frequency and depress the tuition shaft stages should be as far as possible. With the button fully aligned properly as the first step. After the depressed tighten I.F. transformers have up the screw firmly. been properly adjusted Be sore the pushbutton knob is held down and peaked, the broadcast band should be position adjusted. in while being tightened. I.F. ALIGNMENT. After the stations are adjuster) it is advis- With the gang con - able to check each button to assure sufficient lenser set at minimum. adjust the oscillator test tightening. to 456 kc. and connect the output to the To assure accurate grid of the 1st adjustment, the volume detector tube (12ASGT) control should be net at a moderate level and through a 0.05- or 0.1 -mf. condenser. The the station tuned -in slowly to a point of ground on the test oscillator should be con- maximum volume nected to the and clarity. chassis ground. Align all 3 I.F. It is not necessary to follow any particular trimmers to peak or maximum reading on the sequence output of stations since each button is meter. adjustable to any station. BROADCAST BAND ALIGNMENT. Re- move With each button definitely set and securely chassis from cabinet and set it up on tightened to the selected stations. the tuner the test bench taking care to have no iron is ready for operation. The Navigator Globe -Radio set. 276 RADIO -CRAFT for NOVEMBER, 1940 SERVICING

Regarding Standardized Service Charges By Charles R. Leutz IN the radio field, apparently some attempts are being made to standardize charges, a practice which has proven very successful in the automotive industry. It must be remembered, however, that the automotive repair field is much older than radio and that there was a time, not long ago, when the question of proper charges for automobile repairs was just as much up in the air as the matter of radio repair charges is today. Today, the manufacture of automobiles is confined to a relatively small number of different corporations. The set -up covering manufacture, merchandising and service is highly organized. The operations are also fairly profitable. Dealers. by employing skilled labor and using advance service equipment, are able to offer much superior service, and at lower prices, than a free -lance repair shop. In radio, we have a relatively large number of different manufacturers, offering receivers which are essentially the same as far as performance is concerned, but varying widely in circuit and mechanical designs. Accordingly, the possibility of standardized A fixed charge for a repair charges becomes greatly involved. TAKES certain repair to one model may represent a small profit but the same repair to another model may represent a decided loss. The BOTH general idea of fixed charges, if they are high, may apply to a dealer operating in a prosperous residential area. but it becomes a very- difficult proposition for a dealer having customers in different income brackets. PACKED IN ONE Price competition need not be feared by qualified radio tech- CONTAINER nicians who are also able to apply modern salesmanship. A good knowledge of salesmanship is as essential as technical ability. The main reason fixed charges are not profitable is due to the fact that invariably the different customers have incomes which TWO DRAWER vary between wide limits. Old- established and successful professional men, for example ethical doctors and lawyers, vary their STEEL CABINET circumstances involved. They realize a popular fees according to the a honey of a hundred dollars to one man is no more than one dollar to some Here's man with a much lower income. The doctor realizes that steel utility cabinet other CO NDENSER sonic patients cannot possibly pay a fair price for the service with the drawers par- not be able to pay involved and also that other patients may titioned to make it ASSORTMENT at all. The doctor also knows that the patients in the upper income brackets are agreeable to paying above the average to equalize easy for storing small matters. parts. You'll find this LIST proce- The radio Serviceman can well copy the above -outlined cabinet a mighty use- dure. Repairs for customers in the low- income class can often be completed using serviceable second -hand parts and the total repair ful addition to your cost confined to labor. Trade -in sets which have no ready market shop equipment and $1,4,35 can be broken up for such useful parts. Other trade -in sets can best of all ... you get be overhauled and sold to customers, in the low- income class, it FREE on this limited who might otherwise be unable to buy a fair set. This fine assortment of pop- Top service charges cannot be expected unless real value is offer. Don't delay, ular type N.U. condensers given in exchange. Wealthy men do not mind spending money take advantage of will move fast, give you a are the first to demand value. Accordingly it takes sales- and insure the but they deal and get your good profit manship to get orders of this type and real ability to give satis- this good will of your customers. faction. The "new" or inexperienced Serviceman without proper FREE steel cabinet. If you're already using N.U. equipment, cannot possibly compete for this trade. Cabinet size is - condensers, you'll be sure fo The inevitable question always presents itself. It involves the width, snap up this offer in a hurry. wealthy customer that calls for service for some insignificant length lll'r" If you don't know yet how repair. The answer centers around modern salesmanship. When depth, 5" really good N.U. condens- a client comes to a doctor with a broken arm, a definitely known ers are, here's a great op- difficulty, the break is fixed and the case closed. The doctor portunity to try them! The does not try to sell the client on the idea of a complete overhaul assortment you get on this just because he has a complete set of new test apparatus. How- NO DEPOSIT limited offer consists of: has a complaint, the source of which is not ON CABINET ever, if the customer the con immediately apparent, a thorough examination is in order, buy You can 3-1B8450 1-AT2015 necessary and justified. denser assortment I-188845 I-AT8230 So if the radio customer simply needs replacement of a burned - be I-SC8450 I-AT4450 57.50 Plus Points can out filter condenser, it can be taken care of efficiently and at a aetto pfe5ent I-AT81311 3-AT8450 of repeat business. contr N.U I-AT1613 I-AT 1845 reasonable cost with the expectation added get the if radio trouble is complex, a complete shop However, the contr FREE. now overhaul may be in order. cabinet deposit. 3 -T601 analysis and possible complete steel more is no 4-1602 Salesmanship and intelligence, at this time, are important There assort- The technician called in to make a minor repair condenser 3-7605 than fixed prices. 5-7610 has secured an entry and if well informed technically can tact- ment c610u- cwthstile 2 -T625 fully suggest improvements, useful and valuable to the customer packed and involving more money than any repair job. The information n et.' along this line given to the prospect must be presented in an educational manner, leading the receiver owner to appreciate their value and utility. The following possible improvements are applicable to probably more than 50',( of all receiver installations: FOR DAYS ONLY (1) A directional aerial or loop to eliminate part of local noise GOOD and possible adjacent -channel interference. 60 (2) Installation of new tubes with more favorable noise and amplification characteristics. (3) Wavetraps to eliminate certain station interference, or a Signal Booster (R.F. Amplifier) to improve Image Ratio nATIOnAL and reduce interference. 51 STATE ST., NEWARK, N.1. (Continued on page 279) rurrincur RAD10 -CRAFT for NOVEMBER, 1940 277 SOUND SOUND ENGINEERING 7-tee lQ9irn and -fidvi_lory SérviCQ 'jot nadio- erait S'udlcriGQri

Conducted by A. C. SHANEY

This departn.rot is brip condocted for the bcnryil l( um)-C RAFT subscribers. All design, engineering, or th ro. et leu! questions relative tu P.A. installations. sound equipment, audio amplifier design, etc., will be uns wered in this section. ,.Note: when questions refer to circuit diagrams published in past issues of tee!ueiral literature, the original, The Answer . . . or n ropy of the .molt should be supplied in order fo facilito fe reply.) Figure 1 illustrates the original circuit, which is given for the benefit of our readers. No. 11 Figure 2 shows the revised circuit. It will be noted that essentially, an additional 57 pentode stage was added to provide the increased gain required for ac- commodating a crystal microphone. While the 57 is not the ideal tube for this particular application, it is recommended only because a 6-volt winding is not available. It would have been better to use a metal tube in its place, such as the l6SJ7. The use of a 57 (pentode) in the 1st stage necessi- tates careful shielding to avoid hum pickup. It will also be noted that the only changes involved are the addition of one additional stage plus a slight revision of the existing 57 stage. A tone control (of the high -frequency attenuating type) has been added in the grid circuit of the 56 driver. The carbon -mike volume control, Rl, has been removed, together with the double -button carbon -mike transformer TI. Precaution should be exercised in wiring the 1st stage, so as to avoid undue hum pick -up. The feedback trouble that you are ex- periencing (howl and whistle when volume control is turned up) is no reflection on the construction and design of the amplifier. It undoubtedly is caused by operating the microphone too close to the speaker. This condition would probably be present with any other amplifier, unless of course, the REVISED AMPLIFIER CIRCUIT amplifiers are made for carbon microphones. particular model you now have is peaked ACCOMMODATES XTAL MIKE i would like to change to crystal. Can you at or near the frequency of feedback. The INSTEAD suggest changes we can make in this am- chances are that the revised amplifier cir- OF CARBON MIKE plifier, using most of the present parts that cuit, with u more sensitive crystal micro- are in this unit, to give us fuir volume and phone, will aggravate this condition of feed- The Question . , , tone? Would like to incorporate a tone con- back, unless suitable precautions are taken f am very much interested in P.A. sys- trol in this unit also. to adequately separate the microphone from tems and amplifiers. We have ut the present I am enclosing u drawing taken from a the loudspeaker. time about 12 portable public address sys- print we have of this amplifier, with all tems, with which we have had considerable the type numbers and model numbers on the 2A3 AND 53 AMPLIFIER trouble in trying get ease of one of to good volume and theft units, The Question . . . UMW. They seeat to howl and whistle at Wm. L. PASCttxe, This section of yours in Radio the least touch of the volume control. These Chicago, -Craft is Ill. one of the best ever placed in any radio

u.-.+c...< bat WO 531 w,u,.r CO.rtNR 643

,ic' fOCte 278 RADIO -CRAFT for NOVEMBER, 1940 SOUND

I it's one of the most magazine! believe QUALITY UNBEATABLE helpful sections that could possibly be FOR UNMATCHED - LOw PRICES( thought of, or put into use. IT'S RCA And now for a little circuit: We would like to get a circuit using a couple of 53s, P.-P. output, and a 53 driver without using a driver transformer, if possible. The balance of the circuit is something similar to the 2.5 -V. filament circuit in Fig. 2 of your AERODYNAMIC No. 3 article in the March issue for 1940. We wish all the gain possible and about 15 watts output. If you have such a circuit that would fill our requirements, even "MIKE" though it must be altered somewhat from the line -up mentioned, we surely would appreciate the same. Even a couple of 2A3s might work best in the output. You know you. best! That's why we are asking -4-- Please give the complete circuit diagram. RCA Aerodynamic Mi- B. B. BARTHOLOMEW, Priced right crophone...M1-62 26D Harmonies (low impedance) The Bartholomew Sacred even the lowest of Broadcasting Station KFKA, for MI-6228B (high impedance). College Place, Wash. cost job! The Answer ... A circuit diagram of the type amplifier you desire is given in Fig. 3. Although this particular amplifier employs 6A6s in the output stage, these can easily be changed to 53s as the latter are the 2t_ -volt proto- THE RCA Aerodynamic type of the former. of the Inasmuch as the output stage is operat- Microphone is typical ing in class B a driving transformer should world's most complete line of be used. For best results the type 42 (or the "mikes "! It's tops in quality-, low 2%-volt, type 2A5) should be employed its value as a triode driver. The circuit ahead of the in cost. Has proved RCA Uni -Directional triode -which is composed of a 6A6 elec- splendid performance Microphone MI-4043. RCA Junior Velocity through tronic mixer and 6C6 high -gain preamplifier RCA 3 -Way Microphone under the most difficult condi- Microphone Ml -4044. -may be altered to fit any particular re- MI-4036G. quirements you have in mind. For example, tions. In the air, on the ground the front end of Fig. 2 of Sound Engineer- -even in a diver's helmet under ing No. 3 (see March, 1940, issue, page 531) water, the quality is outstanding. may be used to replace the preamplifier and voltage amplifier section of Fig. 3. No matter what kind of in- As I do not know just what you intend stallation you make you have to use this amplifier for, it is difficult for when you use me to recommend either a 2A3 or 53 type satisfied customers of output stage. A 6A3 amplifier circuit RCA microphones. Pressure, is illustrated in Fig. 4. If 2A3s are desired, velocity, lapel, unidirectional, it will be necessary to change the other tubes for their corresponding 2' -volt type bi- directional, non -directional (6C6 to 57, 6A6 to 53); or if the output all types are available, for use tubes are to be changed only, then an addi- outdoors or in. And remember RCA Velocity tional 2',z -volt winding will be required on RCA Pressure Microphone the power transformer. In this latter cir- Microphone -the prices are right. MI .4027B. cuit, the preamplifier and voltage amplifier MI- 4N)4RA. stages may be altered to fit any desired requirement.

REGARDING STANDARDIZED SERVICE CHARGES of America Camden, N. J. A Service of Radio Corporation Coo tinned from page 277) RCA Mfg. Co., Inc., (4) Replace carbon resistors, which vary system sounds better, equipped with RCA Radio Tubes in resistance in operation, with met- Any sound allized resistors of constant value. NOW! Get your copy of the NEW book - (5) Replace all paper and electrolytic RADIO- Principles and Practice -See Page 30+ condensers of low rating with new AUTOMOBILE high -grade units of higher safety factor or rating. FILMGRAPH (6) Install improved "iron- core" R.F., 1 VOIÇ[ AND MUSIC REGOROIMG3 AUDIOGRAPH antenna and oscillator coils for im- Lengthy or continuous recordings now possible with newly NE Sound Catalog proved gain and more uniform re- patented "FILMGRAPH ". Over 13 hours of indexed voice. radio, code, telephone recording on a single 500 ft. reel of AUDIOG "APH Sound Systems repre- sponse over their range. film costing $3.00 and up. No other expense. INSTAN- TANEOUS and PERMANENT play -back. Can easily be the atest in Sound Engineering (7) Replace the I.F. transformer units free. sent synchronized with Motion pictures. Bulletins line plus pre- with improved "band- expanding" MILES REPRODUCER CO.. INC, Dept. RCB. and Desig -a complete types to permit better over -all audio 812 Broadway, New York City tested accesso response. This change also provides a control of selectivity vs. fidelity, University alters NEW LOWE °RICES depending upon the receiving condi- plete line quality and erform- .1 rill gh Power Outstanding tions encountered. I ugh Efllcleney- once at prices that help you eet any Simplify No,Remnant -- (8) record playing by installing MI,vlinm Price - competition. a phonograph oscillator. i. udspeakers. Writs for FOR FREE .OPY (9) Replace phonograph pickup head Catalogue U -6 -40 WRITE with a modern unit. UNIVERSITY JOHN MECK INDU RIES LABORATORIES IIL (10) Install one or more extra loud- 19s Chryetie St. 1313 W. Randolph St. Chicago, speakers. New Vora City RADIO -CRAFT for NOVEMBER, 1940 279 SOUND

:IF. M P. POWER SUPPLY

- .} SPEAKER PHONO bADIO) SOCKET JACK JACK Front (left) and rear views of the Direct -Coupled Recording and Playback Amplifier. All the equipment in the front view is identified, to right, as follows: The pushbuttons at left of meter are marked reading from left Pl, P1 and OFF; at right OFF -. -30 and - 40. Immediately below the meter PANDER and SUPPRESSOR switches. Nest 4 are the EX- controls that read THRESHOLD, SUPPRESSOR, TIMING and AUXILIARY H.F. Extreme lower pilot light and, below, STANDBY switch. Controls: PHONO, RADIO, -left, STANDBY LOW PASS, MEDIUM PASS, HIGH PASS and AUXILIARY L.F. Extreme right, MASTER pilot light and, below, MASTER on -off switch. The Auxiliary are Controls for constant velocity equalization; the Low, Medium and High Pass controls are for . to"1 nmpti .sb equalization.

RECORDING-PLAYBACK AMPLIFI ER Has Direct -Coupled Output Circuit and Equalized 30 -Watt Output

1 ,,,i- leeInlieal discussion of (W amplifier specifically designed to fill tit, To*, , tt,t ttl. r the high- fidelity/ recording and playback field. A nor' l I,' le ss 2 independent equalizer circuits for both constant-velocilll recording and constant -amplitude recording.

A. C. SHANEY

THE requirements involved in the design Wining a constant velocity of the cutting lease time, or time controls, of these circuits of a semi -professional high-fidelity Re- needle. It is obvious, therefore, that when are of critical importance in order to avoid cording and Playback Amplifier offer n the number of oscillatory motions are In- detrimental effects. distinct challenge to the designing en- creased, the amplitude must be decreased For example, in voice recording, it is gineer, for here it is necessary to carefully so that a constant distance is covered by imperative that the attack time be reduced balance performance against cost. If these the cutting needle within a given time. so as to prevent clipping of initial syllables. considerations are not kept in mind during This arrangement, however, is usually For music, fast or slow selections may re- the design. the cost may soar. or the per- restricted at the lower frequencies (below quire individual adjustments for ideal re- formance may be inadequate for universal 330 cycles, which is known as the "cross- sults. Recordings that have both low and application. over frequency"), so as to avoid overcutting rapid tempos should have the timing control It was ths -tore decided to develop a within low - frequency ranges. As most mag- set for some arbitrary average. mediums- priced amplifier capable of provid- netic pickups (which is the type commonly Son -Frequency-Discriminating Scratch ing more than sufficient flexibility of opera- employed for constant- velocity recording) Suppressor.- -The scratch suppressor is tion required to cover all unusual recording have existing frequency response deficiencies highly desirable in order to effectively re- applications. The desirable features in a which vary directly or inversely with fre- duce background recording noise. The cir- truly flexible amplifier of this type should quency, it is advisable to employ a type of cuit employed decreases scratch by 10 include at least the following: egmlirer which will most rapidly compen- db,(C) Variable Equalizer for Constant-Velocity ,,i,te for such deficiencies.(*) Feedback Push -full Output Recording Amplifier.- I'n.,sblc F.gpatitei for Constunt-:tutpli- The use of a balanced type of feedback pro- \',.ruble Equalizer for Constant -A mpl i- huly Iteeordiny. --In constant-amplitude re- vides for looping the output transformer, Recording tudc cording, the velocity of the cutting needle push -pull driver, and push -pull output Stage. Variable Push -Pull Expander is directly proportional to the recorded This feedback circuit, plus a generously - Variable Expander Delay signal. Under these conditions, the ampli- designed output transformer, provides Variable Time-Delay for Control tudes of all frequencies are recorded of a flat frequency response from 20 to 20,000 Non - Frequency - I)iscrinnioatting Scratch equal magnitude. cycles ±1 db., which exceeds the most strin- Suppressor Where equaliratisin is desired for normal gent requirements of professional recording Feedback Push -full Output Amplifier (20 deficiencies in ±1 the recording head, recording equipment. This type of a circuit also in- to 20,000 cycles, db.) blank, or associated equipment, it is desir- sures low hum, noise and distortion levels Low Runs and Noise Level ( -30 V.l'.) able to equalize with a constant-amplitude Adequate Reserve Power.- Although tin Adequate Reserve Power (30 watts i equalizer which is nothing more than the amplifier is rated at 30 watts, shoul.. Correct Level Indicator Meter -audio it spectrum equalizer" familial' to normally be used as a 20 -watt unit at which Output -Stage Plate Current Meter Rodin- Craft readers.(t) This type of equal - level it produces less than 1 2' . total dis- izer accentuates or attenuates a given fre- tortion. At recording FEATURES -AND WHY levels up to - 30 V.U., quency band, equally. its distortion is practically unnseasurable! Variable Egnolizce for Constant-Velocity 1oriabie Time Delay. -in automatic vol- Correct Level Indicator Meter. -This Recording.- In constant-velocity recording, ume expansion (A.V.E.) and automatic meter is of the new V.U. designed volume type in the amplitude of the recorded signal varies control (A.V.C.), the attack and re- accordance with specifications set up by inversely with frequency. That is, higher !This our .4 equalizer has been completely describe.' N.13.('., Bell Labs., and C.B.S. frequencies have a lower amplitude swing. in , the Nos-endsr. 1939, issue of Radio -Craft. pg. 2,:%. This condition is brought about by main- a +iAwiio Su,eetram Control was described in Uw De- 1,The operating prinrtples Invoked were complete') e, mho. pan.. i. sue of Radio -Craft. pg. 42. ers rlbcd In the July, 1940, Issue of Radio -Craft. 280 RADIO -CRAFT for NOVEMBER. 1940 a/Hakim Cep aeapheial H Progressive Series Plan

HOWARD'S revolutionary direct factory conversion set -up enables you to own at all times the The World's Finest! equipment -without risk of obso- receiver that finest receiving these d- .:. -i a single unit :°.:nunication the new l t tube trade -in deals. It is ,!- ,blishes new standards cf performance, lescence loss or unfavorable Built to the ii )W.1RD 490 is outstanding in every respect. the 490 the most flexible and all -in- your -favor purchase ...'.t exacting electrical and mechanical spncifieations, sensitivity that never knows "crowding " and selectivity in existence. If you want the finest receiving sharp position plan ..-it may be varied nt will from the hairline cf equipment your money can buy -with the advan- luired for CW signals to the wide band requiremants Ih fidelity reproduction. tages of adding to your investment at any time Series you desire - -the HOWARD Progressive Plan provides the answer. You can start the HOWARD Progressive Series Plan with basic Model 435 for a protected investment of only S29.95. Model 436....539.95. Model 437....554.50. The total cost for the entire Ideal Receiving Layout pictured above. _5138.35. For complete details see your local amateur distributor or write the factory direct. (E.po and Pafic Coast P- :ar Sightly Higher(

See the Howard Progressive MODEL "490 " -With Crystal Series Models at Your Distributors! Filter and Separate 10 Speaker '1 495° RADIO COMPANY HOWARD HOWARDCO., U. S. A. 1731-35 Belmont Ave., Chicago, I11. Cable Address: % o a n ug a c t u t a t 4 in a t i c a . 1 Ql d a 1 ! 2 a d i /i{

281 RADIO -CRAFT for NOVEMBER. 1940 SOUND

ASS.LP-4 SOOMLIF .006-MF LOW 05 6511 MEG 05F5 1 1 / 65C7., _J MEG. HIGH ASSN} l EOWI I0F A

1 O (EACH) 0 5- L J PA55.BP1 01- BAND MEG. --1 -0.5- MEG. 1 OHMS/25.000 R DIO AUDIO JACK 05- SWITCH L 05- 11.000 MEG OHMS '- O E 0.5- 5 EXPANDER MAW) 10000 \ 6L6G ONMS SWITCH 000 EOUÄL HON

SCRATCH SWITCH TO GAINER CONTROL 100f OHMS

C ADJUST 0nA15

SVIÚE 65J1 LIGHT

DC A C. RECTIFIER 10000 1ttlJ.l5. ONMS NOTE: 12S MA. ARM ON Bp.ABLELANK CONTACT PREN BUTTON LS FUSE ESSED. - i;'TIti

STAND VAC.) (EACH)ÇÁC.íE SW ME11IA Cry A îvIioT rIÓR j o j-17,111 TO-i SW ITCH S0V AOV 500 pIM 0 5\'H I

MASTER Al 11.2' LIGHTY 1 BASIC DETAILS OF METER SWITCHING ARRANGEMENT, schematic diagram of the 30 -W. Direct- Coupled Recording and Playback Amplifier.

It is equipped with a variable illuminating tubes, one of which is used as a push-pull RECORDING EQUALIZING TECHNIQUE control so that the intensity can be adjusted expanding amplifier and the other as a full - for any given set of conditions without wave expander rectifier. As there are a number of variable factors which tend undue eye- strain when a program must be The direct -coupled portion of the ampli- to prevent the attainment of constantly and accurately monitored. In fier follows conventional design which has perfection in recording work, it is desirable order to insure against output tube unbal- been described in past issues of Radio -Craft. to have a suitable number of compensating ance, a switching arrangement is employed For simplicity circuits to offset as many detrimental con- of circuit arrangements ditions whereby the meter is switched into the the values and the circuit of the complete as possible. If we assume that the plate circuits of each of the output tubes V.U. meter have been omitted. The attenu- amplifier itself will not introduce any fre- for plate current balancing adjustments. ator employed in the V.U. quency discrimination, we have the follow- meter is of the ing additional The switching circuit is arranged so that "T" type. Resistors R1 and R2 represent elements to consider: the meter cannot be damaged when push- "T" attenuators to provide any degree of (1) Microphone -its type, response, and buttons are indiscriminately operated. attenuation desired. Resistor Rx is a shunt placement. across the meter for changing the basic movement to read the high (2) Cutting Head -its type and asso- ELECTRICAL CIRCUITS plate currents ciated driving of the output stage. Resistor Rxl is a series mechanism. A 6SC7 dual triode tube is employed for resistor of approx. 3,600 ohms and RA is (3) The Recording Material -its type the phono and radio input. Electronic mix- a variable 500-ohm adjustment for absolute (degree of hardness) and its surface cut- ing is most easily accomplished in the man- calibration of the V.U. meter. ting speed. ner indicated in the circuit diagram. For The power supply microphone work, is composed of 2 in- As an infinite variety response an additional stage should dividual supplies. A 5Ú4G supplies bias of vari- be ables may be 3 added. This may be a conventional 6SJ7. voltage for the preamplifier, voltage ampli- introduced by the elements This tube should preferably have D.C. fier and driver mentioned it is naturally desirable to locate amplifier, while the 5V4G and classify applied to its heater (use 12SJ7) which supplies voltage for the output stage. This major frequency discrepancies may be obtained within the recording system. This is from the common return latter voltage Is added to the bias voltage task of the high -voltage winding. in order to attain the comparatively simple when modern labora- The high voltages re- tory facilities are available. For components employed for the audio quired in the the record- spectrum circuit follow direct- coupled portion of the ing enthusiast, however, who has limited conventional design. circuit. A standby The audio pilot. in series with the facilities, the relative quality of the fin- spectrum is split up into the fol- plate supply of output stage, insures lowing 3 the ished record may easily be bands: (1) 20 to 200; (2) 200 to against damaged checked against 2,000; and output tubes should one its original sound source, and noticeable (3) 2,000 to 20,000 cycles. The of the driver tubes he thoughtlessly removed audio spectrum switch enables the inclu- during discrepancies can easily be detected by sion or operation. The power supply is built trained listeners. exclusion of this portion of the cir- on a separate chassis to minimize inductive cuit. Electronic mixing of the audio spec- hum pick trum signals -up between the power transformer If the recorded signal can not be easily is accomplished through the and the audio spectrum circuits. differentiated from original following two 6SC7 tubes the signal, it which are in turn Although this amplifier has been con- is safe to assume that no noticeable dis- coupled to a 6SF5 degenerative inverter. structed for rack panel mount front crimination The output of (its occurs within the entire repro - the inverter in turn couples panel measures 1414 x 19 ins.) it may be ducing into a pair system. If noticeable discrimination of 6SK7s which are used for built in any standard cabinet for semi- is present, various expansion in conjunction "shades" of equalization with two 6SC7 professional use or home use. (utilizing either the constant- velocity or the 282 RADIO -CRAFT for NOVEMBER, 1940 SOUND constant -amplitude equalizers. or both) should readily correct any noticeable discrepancies. It should be borne in mind that a constant -amplitude cutting head may re- SELL MOBILE quire constant -velocity equalization, because the frequency losses encountered in cutting a soft material will vary propor- tionately with frequency. When a crystal P. A. cutter is cutting high frequencies in a relatively soft material, all of the material is not cut away. A good portion of the needle displacement may simply be pushing the TO THE POLITICOS material from side to side. This "pushed" material nearly completely returns to its original form because of its resilient nature. This phenomenon, in itself, introduces an this year . . . appreciable high- frequency loss. tinder these conditions the constant -velocity equalizer should be placed into the circuit so as to provide a gradual high- frequency boost. A greater degree of equalization will be required, as the needle approaches the center of the record, because of the decreased surface record speed. For 33 1/3 r.p.m. record- MR. JOHN ERWOOD ing a similar type of equalizer is required President in order to maintain good high -frequency says "Model 1120 -M mobile system- designed by the originator response. The degree of equalization should, of mobile equipment has plenty of course, be gradually increased as the of power with ample reserve cutting mechanism approaches the center capacity." of the record. The Sound Engineers' biggest problem is stressed in all Erwood designs. Each Automatic electronic equalizer circuits item has been designed to insure sound may be incorporated into this amplifier so satisfaction under various acoustic con- as to provide for automatic equalization ditions and wide variations in power once exact losses have been established supply. the (frite for pour fr.,. copp of arm rota- in some standard recording material. IO volt Ing hot off the press. This article has been prepared from data Advanced design in combination 6 volt -I mobile equipment results in low hum and noise Be sure to enter the ERWOOD Slogan supplied by courtesy of Amplifier Company level, high overload capacity. Hear this new Contest. $350 in merchandise. Write for of America. amplifier. free information. RADIO SHORTS Erwood SOU N D EQUIPMENT CO. Berlin.- Factories have completed the change -over for the manufacture of army 2 2 2 W. HURON S T. CHICAGO, ILL. radio equipment on a mass production basis. the American Commercial Attaché to Berlin reports. Midget sets are being made in quantity for Germans repatriated from the The NEW East. Denmark. -The American Commercial 9 DOENUT Horn Attaché at Copenhagen reports the invention of a "living ear" automatic microphone said to be a "revolutionary innovation in Who Makes this Provides the recording and reproduction of sound." System is applicable to radio sets and elec- AM AMPLIFIER Wider tric phonographs. FM and London.-The Monitoring Service in oper- FREQUENCY RANGE: 13- 30,000 c s. 2 db Angle ation in Englund (illustrated and described in a past issue of Radio-Craft), which 24 MUSICAL RANGE: 11 Octaves Coverage hours of the day receives and analyzes DYNAMIC RANGE: BO db some 500,000 words from broadcast stations Model to 30,000 Milhnatts in all parts of the world, has added dual POWER RANGE: 0.003 DX8BX services that will speed the delivery of This new amplifier was specifically de- interception summaries to Government designed for frequency modulation tuners, s36.4o partments. These services, Intelligence and standard amplitude modulation receiv- , News, pass information to Govt. depts. by repro- from ers and absolute fidelity phono 15 Watts phone; and answer inquiries these frequency depts. ducers. Actually has e greater It is an out- range than FM transmitters. Spreads high frequencies over a to the amplifier A bill, with a lift of 2 years, passed by standing contribution wide angle. Congress recently gives Army and Nary art and will be vastly appreciated by representatives authority, heretofore only fastidious listeners, musicians, and tech- Weatherproof. available with the United States at war, to nicians. Wide frequency range. examine applications pending in the Patent Guaranteed foe FIVE YEARS Office. Declared within the jurisdiction of No metallic sound. AMPLIFIER CO. OF AMERICA a "secrecy order," any patent application High conversion ratio then could be withheld from the public as a 17 West 7utli St., New 1 ark. N. Y. war defense measure; and any subsequent Write for literature describing this feed -back ratio £111,13I Amplifier Low premature disclosures of the application by unusual the inventor would render him liable to hoe- Sturdy steel constructioi, ing his patent application held "abandoned," Write for complete detail, which would prevent his ever again getting HAND/ -MIKES a patent in America. Advantdges to the An tipptennenl of all riotta'. n,a,udo .part Nowt,,i.mitter.. WRIGHT -DECOSTER, Inc. patentee however also accrue from the new l trucks. transmitter.. .1 lear. crisp ,1 2211 Unlver,ity Ave.. St. Paul. M inn. arrangement. i oiM snap arm. pot. chrome plate, Export Dept.: M. Simons 5 Son Co.. New York t ft. flex. cord. Choice of ircuitc alt i '(trite., ingle and double button Cable Address: Simontr ire" carbon. crystals. dynamics, all im. Jobber. Representatives: SERVICEMEN , tdances. At your dealer or Canadian ITO. Wm. F. Kelly Co.. 1207 Bay St., Toronto, Ontario UNIVERSAL MICROPHONE CO., Taylor & Pearson. Ltd.. Edmonton. Alberta Keep posted on F.M. Read the feature articles Calif., U. S. A. on this -ubjeot in December ltodio- (raft. Inglewood. RADIO -CRAFT for NOVEMBER, 1940 283 SOUND

NEW 2 -WAY DYNAMIC PHONO PICKUP .4 comparatively recent addition to the sound -on -disc field is the Western Electric type PA permanent -magnet dynamic phono pickup which without any. structural changes will reproduce with equal facility either rcrtical- or lateral -cut records. The response of this pickup is "essentially flat" to about 10,000 cycles! Its precision construction is here briefly analyzed.

AUNIVERSAL-PURPOSE phonograph stylus of the pickup front its groove in the coil structure. carries the stylus at its lower pickup which plays both the so- called record. It also results in obvious economies end. "vertical cut" and "lateral cut" records in equipment costs. During the reproduction of vertical -cut with a performance said to excel the records, the rise and fall of best single- purpose pickup commercially the tube carries FREQUENCY both coils up and down simultaneously with available has been introduced by RESPONSE the West- it. Lateral -cut records, on the ern The 9A pickup, as the new instrument is other hand, Electric Company. swing the tube sideways known, is built to exceedingly close toler- like a pendulum. At the flip of a switch, the new pickup Consequently the may ances. It is rectangular in shape, somewhat coils continue to move up be converted for either type of "cut." and down; but with lateral This smaller than a safety -match box (see photo records they convenience simplifies operation and travel in opposite directions, or alternately, maintenance. It also eliminates all at lower right). It is finished in satin alumi- chance after the fashion of a see -saw. Hence, by of selecting an incorrect pickup when num and fitted with plug -in terminals. When shift- switching the electrical connections of the ing to records of different types because not in use, a protecting guard is snapped the coils (series aiding or series opposing de- transfer can over its diamond stylus. The diamond stylus be made without lifting the pending upon the "cut" of the disc), exerts a pressure of but 30 grams. This the pickup becomes bi- functional. feather -light touch prolongs materially the useful life of records. MAGNETIC CIRCUIT The response of the 9A is essentially flat The magnetic circuit consists up to nearly 10,000 cycles for both types of of a rectangular bar of magnetic alloy which recording. Most lateral -cut records are made to are riveted 2 soft -iron, "U "- shaped at a slightly higher level than those recorded yokes, one of which carries the center pole l'y the vertical method. Bell Telephone Lab- -piece. The oratories, 2 yokes are secured directly to the outside therefore, designed the 9A pickup pole plate with increased which serves as a mounting for sensitivity for vertical re- the vibrating system. cordings and thus made the output volume of Since good studio practice calls for the the instrument approximately the saine introduction for both types. of varying amounts of equalization during the recording process to over- Two amain assemblies, a self -contained come the effects of noise originating in the vibrating system and a permanent magnetic record material and other distorting factors, circuit, comprise the internal mechanism. an equalizer capable of introducing a series of complementary characteristics has been VIBRATING SYSTEM designed for use with the 9A pickup. (This unit is known as the 171A Repeat Coil Here an operator is shown using the new 9A pickup The vibrating system of the 9A differs as a and K.S. 10066 Switch.) part of the 1300A sound -on -disc equipment. basically from conventional dynamic pick- It serves not only The pickup by exerting a pressure on the record of as an adjustable equalizer but as a means only about 30 grams (0.9 ups in that it employs 2 adjacent voltage - -os., approx.), minimises of snatching the impedance of the reproducer record wear and stylus noise. The diamond stylus generating coils instead of 1. has practically unlimited life. The output to the input of the amplifiers. These input rating These (equalised) is about -70 db. coils are mounted on n common values may be 30, 250, 500, or 600 framework ohms. of duralumin and vibrate axially The 9A pickup works into a 5 -ohm impe- in a radial magnetic field. Supporting this dance and has an output (unequalized) of structure and mounted midway between UPPER POLE MADE WITH STEEL SPRING the -45 sib. from lateral records and -40 db. Two LOGS THAT FIT INTO 2 coils, is a flat, COIL SUPPORT triangular- shaped spring from the vertical records. Since it is a dy- MOLE IN LOWER POLE TO that can flex up or down and FORM A MAGNETIC twist axially namic unit its impedance remains constant AIR GAP but cannot flex sideways because of its wide over its useful frequency range. Use with- cross -section. Recorded sound vibrations, in out the associated equalizing equipment is the form of undulations in the record groove, not recommended because the response would impart motion to the coil structure through be so nearly linear that a true image of the a thin duralumin tube. This tube, which ex- recording characteristics would result and tends downward from the midpoint of the this is undesirable.

LOWER POLE PIERCED TO ADMIT COIL ASSEMBLY L STYLUS

FLAT SPRING (STEEL) FLAT SPRING (STEEL) SUPPORTS COIL ASSEM., SUPPORTS COIL A55EHr., C TWISTS UNDER TORSION F FLEXES UPL DOWN WHEN PLAYING WHEN PLAYING HORIZONTALLY VERTICALLY Lees P ASncr me MN PLASTIC D4C \ { DISC ..- STTWS STYLUS I -LATERAL - VERTICAL ACTION- ACTION -

A. -The magnetic system in closeup. B.- Latera Action. When the stylus moves laterally the coil fermateltl move up and down the magnetic poles This phantom view of the universal phono pickup reveals its unique use of 2 balanced The coils are "speech coils." connected in series aiding. C. -Ver The 4-prong terminal permits changing the phase of the coils 180 degrees when shifting tical Action. When from vertical to the stylus moves vertically the lateral recordings. The view at left shows the vibrating system enlarged. The circular vane viscous coils move up and down of eimultnrlcouely. One coil material carried by the stylus support damps -out unavoidable high -frequency resonances caused by is now reversed so they still act in series aiding the elastic properties of the record material. 284 RADIO -CRAFT for NOVEMBER, 1940 TELEVISION

RECTION OF IELEVISION RAILWAY ;l-¢I TRANSMITTER a \ \1dl' l',.'O.p, DEEP CUTTING \\ \ \ \ \ \\ \D\ \ \ \\ \\ \ l( {IIII111111 \ \\ 11111\ lilllllllllll i / \\ \ \ \ NIGH MILLS is the best I, HIGH WILLS Realizing that "Experience is happy to be able rniniiri// teacher," Radio -Craft to present the following article. It de- "RAILWAY // / /l l IINUIIIIQ lineates the service problems that beset ARMS" English Television and shows hots these pitfalls may be avoided by those who are DEALER developing American, Television. STATION "PLOUGH ni INN" D A

Eq. I. The effect of a railway and hills upon television reception. TELEVISION SERVICING PROBLEMS M. E. SOUTHALL An Env ish Telcrisian Service Engineer

as many England's largest radio manufacturers. I PROLOGUE reasons but for staff considerations depart- fellows are joining the colours and others had been transferred to the research WARTIME RADIO AND TELEVISION secret research ment for 2 years while the first commercial are working on government and T has now been definitely ruled that there work in connection with the many uses of television receivers were being designed is to be no resumption of the English for war pur- tested prior to line production, and when the ultra -short wavelengths com- Television programmes (see Footnote) poses. real Cathode -Ray Tube television Corpora- with the disc type of which the British Broadcasting engineer which has been menced (as compared tion had to cease radiating at the beginning The type of radio system which had been running for some hit most severely by the cessation of tele- Service de- of the war with Germany. In time), I was put back into the vision is the television service engineer. in charge of television installation There is only one station available for the not the academic quali- partment the transmission most cases he has and maintenance. London Area and therefore fications necessary for a good research job be ideal for direction finding and hard as we were would and yet he feels that going back to ordinary The work was terribly would surely be used by the navigators of very much in pioneering and running into new troubles to our radio service work is a step very enemy aircraft for directing then direction. It is not surprising every day. Transmission tintes were Also, there is much ac- the wrong for them to Capital. of course, therefore, to find that many good fellows limited which meant waiting tivity on the television wavelengths for of- of depression which only start in order to check the receivers ir- programme radia- had a bad attack which the ficial purposes and the hard work or joining one of the Services respective of the time of day at tions may interfere with these transmis- eliminated. job was started. sions. And finally, it would be costly to keep demon- I had graduated through Installations for royalty, press the service going not only for monetary In my own case etc., all came in the ranks of service engineers and super- strations, exhibitions, etc., work. Late nights and constant Footnote -TLe English spelling of the author's words visors to be the senior and most experienced the day's and the Engl i,lt terla 1. awkward but important jobs 11.19 been retained, to this article, of the television service engineers of one of worrying over cal terms It contains are selfeiplutator . wore one's nerves to the very edge. Time passed and as 1939 came in, television was becoming more and more stabilised and we 4 had most of the answers to difficult installa- TRANSMITTER tion problems. The public interest was grow- I ing; prices of receivers were falling to II every man's level and the B.B.C. pro- II from the scien- II grammes were developing tific interest phase to real entertainment value acceptable to all classes of the grow- I HIGH I television set owners. INTERFERING ing army of The R.M.A. decided that the main theme " STRUCTURE at Olympia I, of the annual radio exhibition in August was to be Television and we set I I I to work to put it over in a big way, but as I II Fig. 2. The effect of high we worked the war clouds gathered and it structures upon television was hard to keep one's mind on the job. Would there I I I signals. Was it worth going on with? be war? Well, we all know the answer now II and there is no point in this article to go over those unsettled early (lays of the war. I \\ Television stopped dead and we television CONFUSED \ AREA-24,\ engineers found ourselves with absolutely nothing to do. After years of unrelenting i HI strain and endeavour it is not surprising that nerves broke down and hatred for the war which had blighted our hopes of the future blurred our common sense. We tried to join up and the younger ones below 30 years of age were able to do so but those of us who were older just could not get in. RADIO -CRAFT for NOVEMBER 1940 285 TELEVISION

Thirty is the calling -up age limit in the fiectors were experimented radio industry; with; extra -high careful survey had been nmde and receiv- this means that for men masts were erected; costly extra -low -loss ing tests carried out. over that age radio becomes a reserved oc- .town lead was cupation tried and finally with the aid As installations are carried out and ex- and the fighting services cannot of an expensive, multi -stage aerial line accept you as the perience gained, mark the location of the Ministry of Labour say amplifier fairly good images were obtained. installations on that a certain number of experienced the map by drawing a small men Even so the signal strength was hardly suf- urcle with a number inside. Near must be kept in radio otherwise the indus- ficient the map to maintain synchronization and have a sheet of paper with a Key on it to try may break down thus throwing out of everything had work to be up to the very top 1.11 the colour coding and a list of the num- thousands of operatives and similar limit to keep things going. Valves bered types of labour. In had only locations with notes against them. For other words we were not to drop a little in emission to give rise to a example: wanted except in our own place in the in- service call and the job was a regular No. 1. -Mr. Jones. Type 50d Console dustrial scheme to maintain the home nuisance. front. Model. Good reception area but reflector I left the firm I was working with and The reason for these contrasting results necessary because of took "ghost" from control of the Service department of a was soon established when a colleague and gasometer. High buildings near here. large Rest End of London store. There I were sent down to thoroughly map out the No. 10. -Mr. Smith. are Type 409 Table many of these jobs going as the ma- town with field strength measuring gear so Model. Although in normally bad area jority of dealers employed young, low - that the Sales Department could decide results prod due to high building salaried service on engineers and got properly whether or not to "boom" television in that which aerial could be erected away let down when these youngsters were called town or to advise the dealer to frankly from interference. up and they found themselves with in- admit to the public that his results were, Such notes are creased sufficient to call to mind service work coming in but no unfortunately, freakish and only to be the details of the installations skilled and the map labour to cope with it. In fact many taken as a guide to what television recep- becomes extremely valuable when a prospec- snail! radio firms have had to close down tion would he like when more transmitting tive customer discusses because the type of receiver of lack of staff. Girls are being stations were erected giving good field he wants and asks what the installation trained as radio service engineers by some strength all over the country. charge is likely radio to he. A glance at the map manufacturers to help their dealers after getting his address enables an hut that's another story. accurate estimate to be given and enables th TRANSMITTER engineer helping the salesman to take along with him SERVICING TELEVISION RECEIVERS just the equipment required for i v a home demonstration. (letting lack to television, here ain I back PATH Cr. When making tests for compiling on a radio job with boxes t v, such n of television serv- RE-,ECTED asap and when carrying out demonstrations icing and installation equipment and piles ,/AS E lit of notebooks prospects' houses a pocket compass is and service manuals waiting very useful. It for the war to end. CATH enables a note to be made of the apparent direction of the transmit- Meanwhile you fellows across the Atlantic C,RECT ting station are going at any particular location so ahead with television and many r.A:E that an engineer following of you will bump up against on to make a the troubles permanent installation knows in what we have had when you start installing tele- CIPOLE r direction to mount a dipole with reflector. The vision receivers every day so I don't see term "apparent why I shouldn't direction" is used because open up some of those note- merely- laying out a I line on the map between books and pass on any hints and tips which the transmitter I think may and the receiver will not be of value to you together necessarily give the direction with a description of the equipment `--- ,7==LECTOR in which best used by signals are received. There may television service engineers in England. be large steel structures between the 2 points; Some of the gadgets were on show or at Fig. 3. A patches of ore -hearing earth Olympia for the first time last August cause of ghost images. that deflect the but waves from their normal straight path so have never been used in the field. You may that they arrive get some ideas from at the receiving point from my notes about them As will be seen from a glance at Fig. I. quite an unexpected direction and sometimes which will help you to make tap gear for there was a deep cutting following a natu- from y"u isolves. 2 directions at once! ral cleft in the hills to the north of the Such a state of affairs town and cutting, can occur on the this the transmitting sta- roof of un office building in town surrounded FREAK tion and the dealer's shop were all in a RESULTS by taller steel structures. Figure 2 illus- Every straight line. There was thus a narrow trates the position. service engineer and those dealers "beam" or The waves from the who have the future of area of good signal strength run- transmitter encircle the interfering television at heart ning across the town from North to South struc- should resolve not to create a boom in a ture and arrive at the receiving dipole from certain and the dealer's shop and the Railway Arms 2 directions. If district based on a report of a freak were they were both exactly in- reception. It has in this area. The Plough Inn was phase nothing unusual would happened in England and, outside freak zone be noticed but believe me, it is this hence the difficulty this is seldom the case and the rottenest job out, to try in getting one wave is to get the same results results up to the standard ob- distorted or has a slight lag from one receiver tained at the Railway Arms and dealer on the other a few hundred yards away from another the giving rise to a blurred or double image. that is giving had n difficult time trying to collect from This problem is tackled perfect results because of the by using a dipole some freak phenomenon. landlord of the Plough Inn the heavy with reflector in such a way An example will extra cost of the additional equipment that the re- help to illustrate what I mean. neces- flector "shields" the dipole from one wave sary to give even the meagre results ob- enabling the dipole itself Figure I is a neap of to receive the other a country town on tained. wave weakly but clearly. the fringe of the television station's service An aerial boosting area and bully amplifier may be necessary to bring the shielded from the station by SURVEY YOUR DISTRICT! weak signal at range of hills. General up to a strength sufficient to reception is out one of the first things n efficiently of the question but by that service en- operate the first stages of the a strange freak of gineer or dealer should do directly he television receiver. locality the dealer's shop in finds the High Street that television ix likely to be n roarmercial which ran through the town from the sta- proposition in his district is to buy a large TEST ANTENNA tion was within an area in which excellent Neale mop of the area and hang it on n television images could be wall A type of test aerial very useful for ex- received. in his office or workshop. Then the district perimenting is one shown at the Radio - Without troubling to investigate the should be cnrefnlly surveyed by making te- reason lympia Exhibition by a firm specializing in for these unexpectedly good results, reirer texts one u sheet at tine noel mark- television aerial equipment. It comprised a and against the advice of manufacturer's hog nap the results after analysis on the strong sectional bamboo mast in three S- technicians, he held demonstrations and got liu,pe scale map. many people foot sections with a bolt and thumb -nut on interested. The proprietor of ('olor rode your markings something like the top section. the Railway Aram near the station arranged On the bolt may be fas- this: draw a green line alongside streets tened a cross -bar of wood on which can be for a trial installation and the dealer was in which you find reception .delighted at is good using mounted as desired a single dipole or a the results obtained at the a simple dipole aerial; use an orange - dipole tavern and the consequent with reflector. publicity and, colour line on streets where installations The total height of naturally, it was not long before another the aerial when ex- will probably require a dipole with re- tended is about 30 feet yet it is light enough large "house" at the other end of the town flector because of the Plough - weak signals; a red line to be held by one man or lashed to any Inn- ordered an installation. could indicate that interference is bad Then the and convenient support such as a chimney stack, trouble started. no promise of results should he given to fence, etc. In use, Results were hopeless. Dipoles a dipole is put up first with re- prospective customers in that area until a and if signals are not good the reflector 286 RADIO -CRAFT for NOVEMBER, 1940 TELEVISIO elements are added. The mast can be turned in any direction until the best aerial signal MODEL TROUBLE is received or a satisfactory compromise reached between signal and static. If the 432 SHOOTER latter is bad, the aerial may be moved about -still connected to the receiver -until a location is reached that gives minimum pickup of interference. When these tests have Pocket Size been completed a rough sketch map of the Individual location is drawn and the compass bearing of the dipole and reflector taken and noted Ohm Scale on the sketch. The survey is then complete and a permanent installation may be made from the data obtained. 2 people are It will be appreciated that fiere is the lowest priced "legitimate" required for this type of test, one to manip- tester on the market. Multi scale D'Arson- ulate the aerial and the other to watch the val meter 0.1 mil accurate within 2Ç ;.. image on the screen of the receiver and to Individual low ohm scale as on expensive to the other engineer. If instrumenta. DC volts 0- 51040/0 -500/0 -1000 give instructions volt sensitivity. DC mil- is available, or at 1000 ohm per a table television receiver liamperes 0- l'0 -10. Ohms 0- 500 /0-50.000 /0- can be made up with a rough but sturdy MODEL 500.000. Self -contained batteries for easy transporta- AC -OC ohmmeter ranges. J cabinet with handles MULTITESTER for all $.9Y tion, a long mains lead will enable the re- 446 ceiver to be operated fairly near to the Net aerial location so that shouted instructions 25 instruments will suffice. On the other hand, where the MODEL distance between receiver and aerial is to. in one! SIGNAL great for this method of cooperation other Convenient selector GENERATOR means must be provided and one way that switch operation 702 the writer has found satisfactory is to use a cheap 2 -way telephone set running from $9.95 a drycell. The communication lead may be temporarily tied at intervals to the screened Net milliam meter aerial cable as both leads follow the same DC voltmeter 0 5 50,250.500;2500: DC no electrical effect upon 0 /1'10 100 /1000; DC ammeter 0'10: AC voltmeter route and will have 0,10 100;'500 /1000; 3 range ohmmeter 0,100 A00.000/ I Meg.; each other. Meter sensitivity I Milliampere or 1000 ohms per volt. The engineer managing the aerial can 3 inch square D'Arsonval meter accurate within 2';. of 25 different complete instruments. wear headphones so that both his hands are The equivalent free as he needs to speak back to his colleague only on comparatively rare occasions. MODEL For this purpose a hand -mike will suffice and TESTER can be strapped to the mast mouth high. TUBE 309SC Capable of even finer performance than RCP'; For sales demonstrations at customers' famous former signal generator. Has all latest information Improvements in circuit and mechanical design. homes in districts which, from Tests all new Extremely wide all wave coverage continuously supplied by the map, should be free from miniature tubes variable front 95 Kilocycles to 100 Megacycles. at will. 30°6 modulation at and in a good field min- Output modulated serious interference Tests all tubes-new wave from self -contained Inde iature. regular receiving. 400 cycles. sine strength area, a more simple dipole aerial vendent p cycle circuit. olttenua ballast. and tubes with cale may be employed. One sold in England com- filaments up to full line tine in app microvolt step ladder $2295 in 2 sections voltage. Indicates noisy bration by means of five prises a dipole of aluminum tubes that would other attenuator. Net each half the length of a normal dipole. also test mood. Hat inter - These sections screw into sockets on a element short and leakage Send for neri Catalog 124 doeribing rhr test between all individual complete RCP line of 1940 Dependable wooden cross -bar which is used as a winder elements. Spare socket pro- Test Equipment. Writs today. vision for future tubes to accommodate about 100 ft. of screened with new base arrange- lead -in cable when not in use. ments. Individual tests of each section of full wave On the end of one section is a large, in- rectifiers. duo diodes and all multi - purpose tubes. sulated hook which allows the whole aerial High sensitivity neon in- hung from a gutter, coping. tree dication. Accurate calibra. to be lion. Continuously variable adjustment for all branch, etc., during the demonstration. This line voltages from 105 to 135 volts by means which should certainly find a of a 25 watt power rheostat. Double fused line, device is one celluloid covered tube charts. $1616 place in every television service engineer's a cnaable kit. See Fig. 4. Another instance of the use of test aerial INC. is shown in Fig. 3 where 2 waves are re- RADIO CITY PRODUCTS CO., instruments ceived at the receiving point. The reflected 88 PARK PLACE NEW YORK CITY wave takes a slightly longer path than the direct wave and therefore arrives later at the receiver and the video signal affects the scanning line a little behind the signal be tackled. They allow anti -static aerials to A NEW BOOK ON AUTO RADIO caused by the direct wave. The result is a be erected and moved about until a zone of See Page 305 "ghost" or second image on the screen. minimum or zero static is found in which a permanent aerial installation may be carried The reflected wave is generally much Television weaker than the direct wave and a direc- out. can be positioned to pick up ARE TOC prepared to take advantage of the opportunities tional aerial Industry i. creating? Train An efficient dipole SAFETY FIRST that Use new TELEVISION only the wanted wave. 3oursvif nosy. while Television is young. for a better joli. with reflector is good enough for most jobs Other kit items not essential but used by Write fur FREE ILLUSTRATED BOOKLET. "A Testy' although special aerial arrays must be used many English service engineers are rubber Plan for a Future In ibelln & Television." CAPITOL gloves and safety -glass goggles. It is a RADIO ENGINEERING INSTITUTE. Dept. ltC-11. in bad cases. The portable mast and aerial St.. ti.W.. Washington. D. C. enables the correct direction of the dipole matter for argument whether major re- 3221.16111 and reflector to be quickly determined and pairs on a live chassis should be carried even if a suspended wire type of directional out in a customer's home. Many receivers Attention Dealers aerial has to be eventually experimented have safety devices which cut off the main is Sell Wright Speakers, Ward Leonard Re- with, the mast itself, without the dipole and supply when the back of the receiver lays. Resistors. Flechtheim Condensers. Su- reflector elements, forms a useful support removed but there isn't a fellow among us preme Instruments. J. F. D. Ballast and Dial for the high end of the aerial wire during who has not at some time or other short - Belt kits. Music Master record players. rhang- out ere. recorders. Champion Radio Tubes. Pocket the preliminary investigations. circuited such devices in order to carry trouble light free with first 35.00 Order. By the way, 1 or 2 of these lightweight tests and therein lies the danger. Familiar- ANCHOR RADIO DISTRIBUTING SERVICE masts are very useful for ordinary radio ity breeds a tough hide and many of us 213'2 Dryden Road. Dept. RC. Ithaca. New York work where interference problems have to don't make much fuss of getting a shock RADIO -CRAFT for NOVEMBER, 1940 287 TELEVISION

from :r few hundred volts but there are Agaisam much higher voltages in television receivers and a fatality is it distinct possibility if real contaet is made with an extra -high- voltage supply. Rubber gloves, therefore. are an insurance and many English firms insist that their engineers wear them when BIG handling live chassis. MODEL With regard to the safety -glass goggles, these, of course, are supposed to be worn 860 by anyone handling a cathode -ray television tube in case it "implodes ". Whether or not they are worn depends mostly on the individual or the first for which he works while in the latter case this again may depend upon the insurance company which will have to pay any compensation in the case of accident. Personally, I have not stet a case of personal injury caused by a tube going off on its own although f have been mightily thrilled when I saw a colleague let one slip from his hands on to the floor. We huddled up and waited for it but the tube didn't break! Fig. 4. A portable television antenna solves problems for Servicemen and Servicemen- dealers. AERIAL AMPLIFIERS -micr certain ordinary broadcast wavebands where it is l conditions t he -ignul passed often by the down lead found that using the tone control to to the television receiver cut may be too weak to give the higher frequencies makes the pro- good results but a gramme "Booster" Amplifier will generally correct tolerable. The high -note interfer- Big in Value ence is this state of affairs sold allow satisfactory more penetrating to the ear and its suppression, although Big in Performance reception under what were almost impos- admittedly destroying sible conditions. the fidelity of the reproduction, makes far more pleasant listening. Sensationally Priced at $17.85 Bad conditions ... may be due to: ( 1) low In television reception, the signal strength views on the area; (2) use of a very screen comprise a high percentage of dark Here is an AC -DC Volt- Ohm -Milliam- long lead between aerial and receiver; (3) or medium tones and a low percentage of meter with all the ranges you want . . . weak residual signal after combating local really high lights so that white flashes easily readable on the large 7" instru- static; (4) show comprehensive line network in up over a large area of the screen. Revers- ment with extra -long 6" scale in a sales demonstration ... roost with many points ing these to black spots or streaks causes new up -to -date three -tone case you will for connection to various models; etc. be proud to use in your panel, bench or them to be practically invisible in the large In England, service engineers on calls to the home. Check Readrite Big had 2 types areas of dark or grey tones comprising the Boy's adaptability for your requirements: of amplifiers in their stock to deal with image and the eye is not troubled by them these situations. One comprised u 2 although from DC V. 0- 10 -50- 250 -500 -1000 at 5000 -stage the high -fidelity point of flat- frequency- response amplifier of some 30 view the image on ohms per volt; AC V. 0- 10 -50- 250 -1000 the screen is not perfect. db. gain housed in a metal case with its The effect of reversing white at 1000 ohms per volt: DC Ma., 0 -1 -10- flashes to own power supply. Being thus independent dark streaks has given 100; Resistance ranges: 0 -1500 ohms to the unit its slang of the receiver it could be located the name of "Black shunt type circuit and 0-750,000 ohms; 7.5 at Spotter." A potentiometer aeritil end of the down lead cable in control on the and 15 Megohms. Battery a loft device enables just the right furnished for or other convenient situation whence amount phase a 0 -1500 ohms range. Maroon with it of reversal to be achieved case could be fitted and forgotten. otherwise red and silver panel, attached 85 the effect may be overdone and The second type of amplifier the whole image turned into an appearance handle . . . Dealer Net Price consisted of a single valve in a small metal case only an of a photographic negative. inch or two larger than the valve all round * * * w ith the necessary resistances and con- LEAD-IN CABLES MODEL 510 (leasers to make up a single -stage amplifier Most engineers and dealers carried in of about 15 db. gain. The unit was fitted their stock 3 or 4 different grades of aerial A Handy Pocket - with Size All- Purpose lugs so that it could be screwed to the lead -in cable for the following reasons. inside of the receiver cabinet and leads Volt - Ohmmeter In areas of very good signal strength or were provided so that electrical connection Ranges 0 -300 where only a short length of cable is re- could be made to the receiver chassis which DC Volts; 0 -10.- quired between the aerial and receiver a provided the necessary L.T. and I1.I'. sup- 000 ohms. Com- plies. cheap lead- covered cable is all that is plete with Battery needed. A type of shielded bell wire This cheap and compact little is quite Dealer unit was suitable. It is not necessary to employ ex- $.2.25 very effective in dealing with less severe Net Price pensive low -loss cable where no appreciable cases of the troubles mentioned above. Apart benefit is gained by its use; and from these there were also installation large amplifiers costs can be kept low by using for feeding blocks of flats. cable suitable * * * tenements, etc., for its job but no Letter. but this type does not eoueerr: us here. MODEL 432 -A The other 3 grades of cables were im- TUBE TESTER "BLACK SPOTTERS" provements on this economical type. (1) First was a braided screen coaxial The Outstanding Another useful little gadget similar in cable with a stranded conductor and solid low - Tube Tester Value physical appearance to the single -stage loss dielectric. (2) Then a thicker cable with . . . Checks all aerial amplifier was the "Black Spotter" or an air dielectric maintained by a spiral t y p es including interference limiter. it was used in cases thread wound round a crinkled solid con- Loctals, S i n g l e where complete static suppression could not ductor could be used for be achieved longish runs of Ends, Bantam jr.. and was the means of satisfying cable or in areas of poor signal many an unhappy strength. and the new Mid- customer living in an (3) The final grade of cable was for very gets, Gaseous area of chronic interference which Rec- the most long runs, large networks for flats or dem- tifier, elaborate aerial systems failed Ballast, to clear. onstration rooms, and for use as an aerial High Voltage Series, etc. Filament Vol- The unit derives its power from the re- cable in areas of weak field strength where tages 1.1 from to 110 volts. Direct Read- ceiver chassis and it employs a single valve the signals from the aerial must be con- ing GOOD -BAD Meter Scale. Counter or for phase reversal of the interfering signal served to the utmost. This cable was very Portable Leatherette Case with 85 voltages. Thus the vivid white flashes on expensive and comprised a crinkled solid roomy compartment the screen due for toolsOO to interference are made conductor within an air dielectric and an dark and are much less conspicuous and insulating layer of special paper. A solid seetinn 1116 College Ave. irritating to the eye. lead screen with a waxed paper and a In a way, it is similar to the method of weatherproof outer braiding made READRITE METER WORKS, Bluffon, Ohio up a dealing with uncontrollable interference on cable of very low losses and wide frequency 288 RADIO-CRAFT for NOVEMBER, 1940 TELEVISION characteristics -essential features for high - quality rcpreduetion. Television installation and service prob- OF lems are not so very difficult to solve. It is GET THIS BOOK only- their novelty which cloaks then in mystery but if a calm analysis of the symp- toms is nut do the cause is soon apparent and VALUES the cure applied. Even if a cut -and.dried cure is not known the line of investigation RADIO is generally sufficiently obvious to point the Now way- to the type of experiment most likely to succeed in eliminating the trouble. THE ALLIED CATALOG SHOWS EVERYTHING IN RADIO

CALCULATING IMPEDANCE AT A GIVEN FREQUENCY of the rather DURING the construction .:.41 Radio Hit s1 complicated Public Address System at 'tcty style plastic "rood table and Frank Wiggins Trade School in Los An- teorld -wide models necessary to check Camera" sets geles, we found it vitally and 3 -way the impedance of a number of lines, trans- Portables; Phono_ P j Radio-Recorder., devices. For this par- i Cum - formers, and coupling - binations, Auto of Sets, ticular work we had a standard bridge etc. --all at amazingly 83 NEW low prices a well -known, expensive make; however, MODELS -in a big soc. GREATEST CATALOG ciel 4o -page one impedance that was checked was found RADIO'S sectival to be so glaringly impossible that we were FOR SERVICEMEN-DEALERS- readings determined by SOUNDMEN- AMATEURS: led to mistrust the 1941 P.A. design- bridge. for every the If you're in Radio, you can't plication. Sound ap- of construction were 24 new Sys- The men in charge afford to be without the new tems-7 to 75 of re- new watts- immediately faced with the problem 1941 ALLIED Radio Catalog! features through- e 1 out!ew Lowest checking these impedances by some other 21'! prices t when It's the biggest ever - Attractive Time the work was done Par- means; and since the ..- ment Plan and value- packed pages -and 15 Day most other places which had a bridge of Trial Offer. Complete closed, we were best ever. Shows everything NEW P.A. SYSTEMS P.A. this type available were 8-pag line- of sonic accurate in Radio. Send for your copy sect confronted with the need uni- measuring device of this type. This was now. You'll see why it's finally accomplished according to the fol- versally known as the one the lowing diagram. reliable Radio Guide - More than Pages, 120 most complete index to all value-pee ked ,t -devoted to Everything in Radio you'll Equipment, new copy is tools STrice find anywhere. A books, etc. More than 15,000 yours, FREE for the asking! 'i. quality parts for every radio purpose -all at prices that sere BIC SERVICE SECTION sou money( 18,000 PARTr Radio's most complet' Catalog -with everything for everyone FREE Depend on ALLIED the Don't in Radio. - miss the aped". World's largest Fowlush-a Huilders' SEND Radio Houacl metters' and F.xper ¡_ COUPON section and The oscillator was n standard audio fre- complete Amateur the fion eels.. quency- oscillator of a common and inex- of communications RADIO CORP. Sets, ALLIED pensive make with an output of about 3 etc. 833 W. Jackson Blvd. Dept. 2 -L-1 watts. 'flte milliammeter, indicated at t', Chicago, Illinois I had a 5 -mat. movement which we found in . .,,a11uci.ingrtar Felt Radio Cata:ng 1n II+lip. most cases to be ample. Two types of volt- E meters were used, first a vacuum -tube voltmeter and later a 0 -15 V. voltmeter of 20,000 ALLIED RADIO ohms resistance was used, and in each 'volt Address ,wise the results were so similar as to be immaterial which was used. If n resistance- CHICAGO, ILLINOIS t ype voltmeter is used in Position B, it is _I necessary- to find the current drawn by the meter and subtract from the total reading. If the meter is used in Position A, the resistance of the milliammeter (C) must be NEWS SHORTS . . . known in order to be included in your cal- TURNER . Orrin E. Dunlap, , ulations. formerly Radio Editor of the New York any type This method works with almost Times, is now Manager, Information Dept., of oscillator or meters if reasonable care R('A Mfg. Co. Here's congrats to one of have also for free new literature good judgment are used. We radio's old -timers who has earned whatever Write be used with (mind that this method can bounty radio has to offer. . . Dr. Paul The TURNER CO. Cedar Rapids, Iowa as most people can bout the same accuracy Nipkow, inventor of the television pinhole 4, ab LumJ.N. p .. Frt h...sv .. t. . -e the more expensive and more compli- scanning-disc which bears his name, last must :tted bridge. Since most service shops month died in a Berlin hospital, the New have these instruments and the few times York Times reported last month. He was is taken would a measurement of this kind 80 years of age 2 days previously.... The a bridge, hardly- warrant the expense of New York Y.M.C.A. schools are planning a 1940 RADIO DIAGRAMS will no doubt be welcome to to this method G- 8 -week radio course designed 'ss - , icr ..fl y,i new to . . i i i give 1 .v , of a measuring tigl....lune 9 ..1. nt cads. those needing this type amateurs to pass Federal circuits cvt- n-arled. (2) c u .py equip radio taclopments. and 13) teach you ` how to m device. radio operators who wish and efficiently millions of acte sold last year. 1c examinations for Inclues ice hints. arnment, and $150 into the communications field as it Ilea-. art` 1 (rt.large J. D. WEISS, to step S._` `,l] la. mPostpaid. w only - llaves. il'iggins Trade School, is now being shaped to suit America's Na- Frank SUPREME PUBLICATIONS Ciushe Illinois Los Angeles, Calif. tional Defense Program. 289 I;ADIO -CRAFT for NOVEMBER, 1940 ELECTRONICS1

The following article de- scribes the new and remarkably ingenious Solovox, invented by Laurens Hammond who created the Hammond Organ and the Novachord, and tells how this 14-tube device may be used as an electronic musical supplement to any piano.

4 The photos at left illustrate various elements of the Solovos. At A, the attachment in use on a grand piano, a set of 12 control tablets giving any piano an indefinite variety of tone colors that simulate the organ (Note individual volume control.); S, close -up of upper portion of the Solovos showing how the control tablet add-on device is tilted to produce a desired effect; C, the Solovos keyboard being attached to the piano keyboard by thumbscrews, THE ELECTRONIC "SOLOVOX // La tad %2ad10- Mai ¿cal 'd unct to the Piano THE Solovox is a new 14 -tube instrument lator. This new frequency corresponds to a master- oscillator by varying the inductance -invented by Laurens Hammond. crea- note of pitch one octave tor of the Hammond lower than the of a small coil (Li in diagram) connected Organ and the first controlled oscillator. across it. Novachord, and expressly designed as Similar cascaded oscillators a musical provide pitches The volume of sound from the speaker is supplement to the piano -that of 2, 3, 4 and 5 even octaves below that of the controlled by a knee -operated rheostat a child can play perfectly. Operated master oscillator. In this way, entirely by electricity, each time which acts to control the amount of am- the Solovox is a the master oscillator is tuned to sonic one plification. 3- octave keyboard which is attached to the of its 12 possible frequencies (one for each The Solovox piano so that the fingers of one hand can note will remain in tune in- of the scale), each of these 6 con- definitely. However, as the pitch easily span the 2 keyboards. A total of 12 trolled oscillators of the immediately follows it to piano with which it is to be played control tablets give the Solovox a 6- octave produce outputs which are will range as well as the lower oc- vary considerably, a tuning adjustment an indefinite variety of taves of this pitch, to form a series tone colors, and being smooth, of 6 knob at the top of the tone cabinet has sustained and frequencies in exact octave relationships. been provided capable of "swell," its tone colors with which the instrument make an Now the particular oscillator outputs de- may be easily effective contrast to the percussive brilliance sired for passing tuned by the pianist in 10 of the piano. through the amplifier and seconds' time, to the piano. It is not neces- A knee lever controls the speaker, depend upon the volume. A slim particular play- sary to tune each note -the single tuning tone cabinet containing the ing key depressed (for instance on which electrical equipment, including knob provided simultaneously tunes then the loud- one of the 3 "C" keys) and also, upon which all by varying speaker, is set alongside a vertical piano the inductance (L2 in dia- or of the "BASS- TENOR -CONTRALTO -SO- gram) that resonates the master- underneath a grand piano. PRANO" controls oscillator This instrument are employed. circuit. represents a new source The selection of the desired oscillator of income for Servicemen and Servicemen - occurs when dealers. a second contact under each USES key closes. This second contact operates an The electrical relay having Solovox, which can be played by MODUS OPERANDI contacts to make even the self -made pianist without any the desired oscillator selection. It is to be All the notes of special instruction, adds singing voices like the Solovox are controlled noted that there are 3 relays, one of which orchestral by a single radio vacuum is common instruments to the tones of the tube master oscil- to each of the 3 octave groups piano. The player carries lator (see diagram) operating at one of of keys. Thus, we the melody on the the see that a playing key Solovox with the right hand and 12 audio frequencies in the highest octave functions in 2 ways -first, it the left of the instrument tunes all of hand accompanies on the piano. The right (2,093 to 3,951 cycles). the oscillators to the pitch of the key being hand Each time a key is depressed, depressed, can easily encompass notes on the Solo - a switch and then selects the output of vox and piano keyboards under it tunes this oscillator to the pitch the particular sub- octave simultaneously, associated frequency con- considerably enlarging the pianist's scope. with the key in this highest - trolled oscillator desired. octave range. This On the front of the Solovox are the pre- occurs regardless of A further function of the second key viously-mentioned, whereabouts on the keyboard contact tablet- shaped tone selec- the playing is to transmit the signal to the tors and all that the player key is depressed. Thus, whenever any one speakers with a controlled must do is to of rate of attack, push them in various combinations to the "C" keys is depressed, this oscillator so as not to be musically abrupt. Tuned ex- is tuned to 2,093 cycles, tend the range of the instrument to 6 which is its lowest electrical circuits and tone controls follow, octaves and create frequency. If any "B" key is depressed, which control hundreds of exciting new its the quality of tone over a tone -colors. Some of these e frequency will be 3,951 cycles, which is its very wide range. tones resemble highest flutes, strings, brasses or woodwinds, while frequency. The effect of the "MUTE" is produced by The output of others have never been heard before! this master oscillator con- passing the signal through a vacuum tube The trols the frequency of operated exceptional versatility of the Solovox another oscillator non-linearly so as to suppress the makes it a flexible called the buffer oscillator which sharp curvature addition to the studio operates of its input wave, and equipment of any radio station. at the same frequency as the master oscilla- thus render the tone more mellow. With the tor. The output of this Solovox attached to the piano, ensembles first controlled are heightened and dramatized (buffer) oscillator in turn controls the fre- PERMEABILITY TUNED by its smooth quency of a second attack. The rich variety of its tones ranging controlled oscillator, so The "VIBRATO" effect is produced by a from a interconnected with the first brilliant, string -like effect to a deep as to oscillate vibrating reed (which is put into motion and penetratingly organ -like at one -half the frequency of the first when quality make oscil- the volume control lever is brought it a new and different instrument for music See "Announcing the 'Rorachord'- forward in starting the instrument) which Rea Ica Electronic Music's lovers to hear and enjoy. -Tube 'Baby' ". Rattle-Craft. April IJ39. intermittently changes ' the pitch of the For a vocalist, the Solovox provides a 290 RADIO -CRAFT for NOVEMBER, 1940 ELECTRONICS

291 RADIO -CRAFT for NOVEMBER. 1940 ELECTRONICS

ELECTRONIC SOLOVOX (Continued front page 290) full, well -rounded background. The fact that all the technical difficulties, such as perfect pitch intonation, smooth vibrato, smooth tonal attack, and quality control are all taken care of in the design of the in,tïu- ment makes the Solovox the easiest of al orchestral instruments to play. No special training is necessary, for anyone who can pick out a tune by ear on the piano can 5 play it effectively. In the studio where space is precious, the Solovox is especially adaptable, for it takes up no extra room. It is entirely electrical in operation and by means of 1 tuning knob can be tuned to the piano with which it has been assembled. The 14 standard, Dealer Net inexpensive radio tubes -the heart of the Cash Price instrument S.L('. Time Payment -may need replacement only in Plan the course 85.00 cash and 10 monthly of several years' playing time. payments of $3.90. Radio men will note that the comparatively low cost In Meist ('ase of the Solovox (under $2001 places it within the range of small as well as large want radio stations, (Dealers give to purchasers, without charge, what little instruction may be nee, s.sary)

ELECTRONIC VOLTMETER Model 549 is the result of a long p..iiod resraivh in designing of l' "attu',s incorporated a !millimeter which is ill accuracy are the extreme fulfill the serviceman's needs of acquired by adjusting the tomorrow today and ter at "sem' position ohmme- at a price he can afford tu pay. and "full scale" posi- The instrument mill take tion. After this is once set iceman's care of all the serv- justments there are no ad- multinleter requirements since to be matte between ranges. The has standard provisions it low range has a center volts for A.C. and output scale resistance of current deflec- addition to select tion in checking resistances rronicvcircuit S fort! i).( . coils. of radio frequency voltage and resistance measurements. You will like this type of ohmmeter its speed and for accuracy. Being of an elec- 0.1 TO 6000 D.C. VOLTS- .covered tronic type the meter is fully protected overlapping !anses by six accidental application and of 0/2/0/20/60/2u0 /cote ohmmeter of the voltage to the volts. These ranges may be will not injure the Instrument. volts. at .mall extended to OAS/ extra cost, by use of a VOLT SUPREME Type 4875 Probe. The input 500 VOLTS-covered dance of all ranges impe- ng ranges 05//1:50/1.0/500 up to and including the In circuit vloverappots 600 volt range is 11.000,(NNl t whose calibration is guaranteed Impedance ohms. The Input to +3%. Copper of the 6111111 volt oxide rectifier is fully pro- 000 ohms. range Is 150.(M0.- tected and carries the Both probes for measuring U.C. other same guarantee as all volts have a built -in resistance parts in the instrument. Temperature U.C. volts so that the error of rectifier is corrected developed across oscillator grid range of over a working leak can be measured without materially 40° F to 100° F. Laurens Hammond at work on his newest inven- fecting the af- }ion, she 14 -tube Solovos, which oscillator. Also all plate, screen 10 51111t11AMPERES TO was recently bias. A.Y.C., and A.F.C. voltages l'l ERF;N'f- 15 AMPERES D.C. introduced simultaneously in Chicago to the measured can be covered by 7 direct ranges of National Music Merchants without upsetting the operation of 11 / :01 microamperes.; 0/5/15/:.0/150/500 Association conven. the receiver. Voltages M.A. tien and in New York to music notables positive of either negative or and 0/15 amperes. Such a wide selection and polarity with respect to chassis or ranges was incorporated of to members of the press. ground may be measured to meet all current by setting the cir- measurements necessary ro m cuit selector switch to " volts or microamperes -t the few volts. The low " +" found In control circuits to the wise to do the work in range of 2 soft fail scale gives ampere drain of automobile receivers. the customer's home. a Sensitive meter necessary In measuring 95% Are Simple small control 0.1 Ti) Cases -As you will voltages. 500 OUTPUT VOLTS -can be used discover with any good signal generator when you become acquainted with 0.5 OHMS Model (SUPREME TO 1000 MÉGOHMS- covered by 5 or 5011 for receiver alignment. television receivers, they are quite different, overlapping Covered E1 ranges of 0/IO0S) /i00.000/1 by five ranges of 0/5/15/50/150/500 electrically and mechanically, from broad- megohm /l0 niegohms /1000 megohms. This Volts. electronic circuit permits cast sets. Since the slightest deviation from all resistance The Model 549 is ranges, including the 1000 megohm range, to also available in beauti- extremely high standards be operated ful oak case as illustrated for $42.50 cash of precision de- by the self -contained 3 volt bat- 15.00 or sign cash and 10 monthly payments of 31.1t. shows up in the "picture" tube, such compromises in specifications and tolerances RN as have been adopted widely in sound re- SEND FOR NEW CATALOG ceivers cannot be made in television circuits. SUPREME The use of high voltage -just off the press. Iatrge, two color exerts an im- SUPREME INSTRUMENTS illustrations, complete descriptions of portant influence in television set design. GREENWOOD. MISSISSIPPI. U. S. A. "2 new 1941 del SUPREME quality If parts break down in sound equipment, testing instruments. Write today! it is easy to replace whatever has gone ! 1MR - -- - M Mt wrong, but when several thousand volts get loose, expensive damage may result. Finally, SERVICING TELECEIVERS cheap materials and inferior designs are PATENT S- TRADE MARKS not suitable for ultra- frequency circuits. SERVICE work on television receivers Booklet concerning Inventions & Patents can Thus, the superior materials and con- be divided into 2 Form "Euidenee of Conception" with parts: 95% can be struction necessary for television equipment !!ruction toc use and ".Schedule of done with the conventional Government and instruments eliminate the source of ninny Attorney. Feel ' -b'ree which every failures com- Serviceman has already, plus mon to the average sound LANCASTER, ALLWINE & ROMMEL an receiver. There is ultra -frequency oscillation; 5' requires a sufficient Ileristered latent Attorneys instruments background of experience al- 436 Bowen that individual Servicemen and ready to indicate Bldg. Washington, D. C. most that service work on an dealers would not be justified in buy- average good television receiver ing, Andrea Radio is almost Corp. has found. entirely a matter of tube failures. It appears, therefore, that the jobbers From the foregoing, will you can see that have to take upon themselves the in- there is no high- voltage hazard involved vestment in instruments required for the in 95% of the television service work. The 5r . part of service SCOTT problems. Dealers and 5',/c to be done by the jobber's service Servicemen will handle all this very small department may require special tests to be part of the work, and when a condition made with the current on, but the Service- CUSTOM BUILT arises which they cannot meet, they will man who makes the conventional tests for have to deliver the set to the jobber's serv- which he is equipped does not need to take RADIOS ice shop, since the equipment needed in such any risk whatever. He can do his work cases is hardly, portable, nor would it be with the power switched off. 292 RADIO -CRAFT for NOVEMBER, 1940 F.C.C.

WHAT IS THE F.C.C.? the major portion The following items are abstracts from, and constitute Commission en- of, the recent release of the Federal Communications titled "ABC of the FCC."

by radio, and to the licensing and regu- of all radio stations as hereinafter lating is provided. . ' Communication which wholly intrastate is not included. the F.C.C. CONFERENCE Is the Communications Act limited to One of many conferences, continental United States? No, it applies held before a license is also to Alaska, Hawaii, Puerto Rico, and granted to a new radio to the Philippine station is staged here by other possessions, but not the FDIC Rules Commit- Islands or to the Canal Zone. tee; at head of table activities of the Telford What are the major G I Counsel for all Taylor Others are: Wm. FCC? Allocation of frequencies J. Norfleet, E. K. Jett. classes of radio stations, except Govern- T. J. Slowie, A. D. Ring, ment; licensing and regulation of radio A. W. Cruse, Edward L. other radio serv- White, Wm. P. Massing, broadcast stations and all Joseph Rauh, James A. ices, including the common carrier services, Kennedy, Theodore Bart- international, television, facsimile, educa- lett, Florence Stretch, and and de- Gerald C. Gross. The tional broadcasting, experimental F.C.C. considered 7,500 velopmental; licensing of radio operators; applications last year. promotion of safety of life and property rho, n-- Cmute.v the use of wire and radio corn - Washington I n. .i Post. through munication by requiring compulsory use of radio, and licensing and regulation of ship and shore, aviation, police and forestry radio services; investigation of complaints as to matters coining under the provisions of the Communications Act; encouraging effective use of radio. of the United States a rapid, the larger and more THE following items are presented here the people conduct of special studies and efficient, nation -wide, and world -wide wire including the in order to clarify many misunderstandings with ade- engineering research; and regulation of the functions and and radio -communication service engaged of radio men concerning at reasonable charges, for telephone and telegraph companies of the Federal Communications quate facilities in interstate or foreign limitations the purpose of the national defense, for as common carriers Commission. This body has been authorized of life communication by wire or radio. all com- the purpose of promoting safety by Congress to license and regulate of wire and What is a "common carrier "? The Corh- Radio in the and property through the use mean munication - principally - and for the purpose munications Act defines this term to States of America and its posses- radio communication, as a common carrier United of securing a more effective execution of "any person engaged sions, except the Philippines and the Canal hire, in interstate or foreign communi- over this policy by centralizing authority here- for Zone. To date this control extends several agencies cation by wire or radio or in interstate or (our tofore granted by law to A approx. 65,000 radio transmitters additional authority with foreign radio transmission of energy." receivers do not come within the and by granting in radio broadcasting is not 46,000,000 respect to interstate and foreign commerce person engaged province of the F.C.C.). A staff of 600 per- is deemed a common carrier under this act. of in wire and radio communication, there sons is required for proper functioning be known Broadly speaking, a common carrier for hereby created a Commission to without the Commission. Communications Commis- hire must render a public service as the 'Federal to all who may apply. icotions sion,' which shall be constituted as here- discrimination What is the Federal Com Mil execute What does "wire communication" mean? Federal agency inafter provided and which shall Commission? It is the provisions of this act." The transmission of writing. signs, signals, licensing and regulating inter- and enforce the of all kinds by means charged with whom does the Cons /nn,iratinus Act pictures, and sounds state and foreign communication by means To wire, cable, or other like connections. (in- apply? Section 2 (a) of the act says: "The of of electric energy, principally radio apply to all What does "radio communication" mean? other radio services), provisions of this act shall signs, cluding broadcast and foreign communication by Transmission by radio of writing, and cable. interstate and and sounds of all kinds. telephone, telegraph, or radio and all interstate and foreign signals, pictures, la the FCC under any Government de- wire does "broadcasting" mean? Dis- transmission of energy by radio, which What partment? No; it is an independent Federal within the semination of radio communications intend- by Congress, and, as originates and/or is received establishment created and to all persons engaged ed to he received by the public. Congress. United States, By 7 Com- such, reports directly to United States in such com- How is the FCC administered? did the FCC start functioning? within the appointed by the President, sub- When munication or such transmission of energy missioners July 11, 1934, when the Commissioners took their oaths of office, at which time the Federal Radio Commission was abolished. Under what authority does the FCC operate? The Communications Act, signed by President Franklin D. Roosevelt on June 19, 1934, as amended. How were cotnnun,icatio, matters administered before the FCC was created? Juris- RADIO DETECTIVE CAR shared by the Post Office De- Specially -equipped auto diction was field serv- partment, the Interstate Commerce Com- used in F.C.C. Radio Commission, and ice for tracing unlicensed mission, the Federal otherwise agencies. The Communications Act of stations and other hunting unlawful transmis- 1934 not only coordinated supervision under The car is equipped a single agency, the FCC, but established the sions. communications policy. with a direction -finding basis for a national loop antenna. What is the basic purpose of the FCC? This is best explained by section 1 of the Communications Act of 1934, as amended, which reads: "For the purpose of regulating interstate and foreign commerce in communication by wire and radio so as to make available, so far as possible, to all 293 RADIO -CRAFT for NOVEMBER, 1940 F.C.C.

ject to confirmation by the Senate. The President also designates the chairman. 117tat is the term of an F('(' Commis- sioner? Appointment is for 7 years except in filling out an unexpired term. MONITOR STATION Florac does the FCC function? From 1934 to 1937 the Commission functioned with Typical Monitoring Sta- three divisions -Broadcast. Telephone. tion similar to 6 others, and strategically Telegraph -but today it operates as a unit loca led with direct supervision of all activities. throughout the U. S., Besides sitting at hearings, and at formal operated by the F.C.C. and informal meetings, it assigns Includes a Standard of various Frequency, commissioners to make special studies, and Interpolation carry out particular functions. Though Equipment, Receivers, Re- routine work is delegated to qualified corders and Oscillo- offi- graphs. cials, policy Working is retained ter the Permits measure- Commission as a whole. ments of frequency from 100 kilocycles HOW is the FCC's normal to 100 nrinrinixtrative megacycles with a high work handled? By 4 departments: aecoucc r. ing, degree of accuracy. Statistical, and To riff Depot air e, 1, which handles matters of accounting regte - lations, compilation and analysis of statis- tics, and tariff analysis and regulation: Engineering Department, which attends tu the engineering phases of broadcast. corn- mon carrier, and private and ship service 11' /rat is the F('C doing in the field of police radio stations, 526 forestry radio sta regulations and enforcement, international engineering? It is investigating nanny tech- and tions, 55,000 tentateur radio stations, 263 interdepartmental matters. supervision niques and refinement: in all branches of coastal of the field staff, communication. radio stations, 36l fixed radio sta and technical engineering It has held public hearings tions, and the rest research; Law Deportment, on the new FM (frequency miscellaneous. Last fiscal whose work in- modulation) sys- year 7,500 applications for cludes the legal phases of broadcast tem of brorulcast. ami on various classes licens- television develop- of broadcast stations were received ing and regulation and of common ment. It is working out engineering by the carrier meas- Commission. Of this number 1,630 were licensing and regulation; administration ures to carry out provisions of for the North increased facilities, and 2.3e)0 were renewals. (including legislation, rule making, und in- A ¡apnea n Regional Broadcasting Agree- ternational ment. It A total of 29 new standard broadcast sta- matters), and litigation before has Iaunched the most significant tions were licensed, the courts; and the Secretary's study of sunspot effect 76 applications were Office, which on communication denied, need 8 licenses were voided. has charge of internal administration, cer- yet undertaken. It is working to reduce tain routine interference Hone mn s ry commercial tridin stations are licensing, and promulgation of to radio front electronedical there in this formal and like country.' About 5,000. More orders and decisions. apparatus, and has contributed to than 15.000 commercial AU the C'ommission's effective use of directional operators were li- rules and amend- antenna. Fac- censed last fiscal year. There are ments thereto are published in the simile transmission, and new approxi- Federal type carrier mately 50,000 commercial operators of all Register. Also, copies of the various parts, telephone systems are also receiving the classes. in convenient pamphlet form, can be ob- close attention of Commission engineers. Hato tained from the The act requires MOO violin oneate,,r:s are there in Superintendent of Doetn- the ConuuissMI1 to "study this country? Nearly 53,000 nïents, Washington. D. C., new uses for radio, provide amateur opera- at nominal cost. l'or experimen- tors have been licensed by the FCC. To what extent (FOCS the FCC cooperate tal use of frequencies:, and generally en- with Hoar many radio receiving sets are there other public bodies? In international cour:tge the larger and more effective use in matters of radio this country? More than 45,000,000. These it collaborates with the State De- in the public interest." are not licensed partment; in national Does the FCC by the FCC. matters with the charge for liccnsing? The Hou' aunty persons are employed various Government departments Government exacts no fee by the and agen- or charge of any FC('.! Slightly more than 600, cies concerned, usually through kind in connection with Fr(' licensing about 200 the Inter- and being in the field service, tell under Civil department Radio Advisory Committee, and regulation. Service. in State natters with the State regulatory Hua' Many radin sttNj,nrx n,' titrer i, bodies, largely lh is Coat t,'a Hine many field offices has the FCC? At through the medium of the About 65.000 radio stations of present, National Association of Railroad all types are licensed by the FCC. 27, located throughout the United and Utili- This in- States and its possessions, ties Commissioners. cludes 826 standard broadcast stations, 600 augmented by Does broadcast stations other seven monitoring stations. In the field some the FCC assign channels to Gure,vt- than standard, 33.2 115 inspectors enent radio stations? experimental stations, 3.900 ship regularly inspect and inves- It has active participa- radio sta- tigate all classes of radio tion on the Interdepartment tions, 1,894 aviation radio stations, 1,100 stations, examine Radio Advisory radio operators for various classes Committee which advises the President of li- making in censes, look for unlicensed operation, and such allocations. Of the present inquire into 9.500 such assignments complaints of interference to to Federal stations, radio reception, etc. 5,500 were made last year. Ilea the FCC Were FCC radio rules and regndations anyt /vin /) to do with national changed last year? defense? Besides performing important FCC rules and regula- functions tions governing all forms in connection with preservation of radio service of neutrality, the Commission were completely revised. More than 2,500 is expressly pages of testimony charged, ley its creative act, with carrying and 200 exhibits were out "the purpose considered as a result of hearings of the national defense." on the The act gives the President subject of the standard broadcast rules and special powers standards of good in respect to communications in the event engineering practice gov- of war or erning standard broadcast stations. national emergency. Hone is the FCC rnneerned ilhat dors FCC rcp,dutinn of radio em- with safety brace? Granting or of life and property? A 1937 amendment denial of applications to for construction permits or the act stipulates: "Fur the purpose of licenses to use obtaining maximum radio frequencies, classifications of stations, effectiveness from the allocation use of radio and wire of frequencies und assignment of communications in call letters, licensing connection with safety of life and property, of radia operators, the Commission inspection of equipment and regulation of shall investigate and study its all phases of the problem use, prescribing the nature of the service and the best to be rendered methods of obtaining the cooperation by radio stations, making and regulations to prevent interference, coordination of these systems." Ship radio and installations otherwise carrying out provisions of the and operations, shipboard auto Communications alarms, and police and forestry protection Act. systems iFhat clogs FCC are in this category. Last year the regulation of COMM, le Commission made 15,500 ship inspections, carriers embrace'? In addition to licensing and MARINE SAFETY WATCH functions, its regulation authorized 350 new police radio sys- Section of F.C.C. Marine Safety Watch where includes super- tems. and 230 forestry systems. observers listen -in 24 hours of the day for distress vision of all charges, practices, and classi- calls and other radio signals. fications; prescription of "just and reason - 294 RADIO -CR AFT for NOVEMBER, 1940 F.C.C.

Mlle charges "; prevention of discrimination; authorization of new construction, extensions and improvements, and changes in ownership; passing on applications for in- RADIO TRAINING terlocking directorates; and the formulation and prescription of rules and regulations AMAZING REDUCED PRICE and manner of to the form exact reprint of regular $39.00 pertaining 9 5 Tai. Is your chance to get keeping accounts, and pertaining to the Radio Technical Institute course for only $1.95. the full is latest Radio and Television Course, and other 1 rice Titis the preparation and filing of annual complete in every way, end exactly the same as the much reports. The rates and regulations of tele- ?OSRAID higher priced original lessons. companies covering phone and telegraph ABOUT RADIO interstate and foreign communication serv- EVERYTHING and are The training is remarkably complete. You quickly ice are on file with the Commission learn radio sen icing (tom simple circuits to signal open to the public. The carriers are re- tracing. From the very start you are Intraiueed to and real radio melba's and equipment. .After finishing quired by law to observe these rates this course you will be able to expertly .` nice every Last year about 17,000 new radio set. Take aitarta ve of this unusual bargain In regulations. radio education. tariff schedules were filed with the Corn - GOOD REVIEW COURSE mission. TELLS HOW TO USE INSTRUMENTS, M. H. Reitman. enforceable? The radio How are FCC orders TRACING, TELEVISION FOR THOSE IN RADIO Instruc- the Commission may be enforced SIGNAL tor in Chicago orders of Many active servicemen have found this reduced-Price Learn i spend- oink: of radio fault Tecchh. the United States District Courts. course excellent for brush up and study of new servicing schools. through on finding, { servicing short -cuts. case his- Institut course methods. Reprinted In 1940, with added information What is an FCC monitoring station? visual alignment, P.A. appli- tories of e on troubles. extra profit signal tracing. television, of regu- ëead Innáaáio` a equipped to listen in, ob- cation. photo -cells. etc. All about A.V.C.. how to use Ideas. Two large lessons on use I believe this This is station resonance action. and lar test equipment, explanation of signal is the biggest frequen- an ocdllostcope, what is feedback bargain in radio serve, and measure the operating other fact you must kisses to he the best service- tracing test methods, telesislon to the every to training. of radio stations, to deter- nun. Forty -three radio m' ns ft ttirett heisted prepare minute. recording dope. with this in cies of all classes sit es you facts and job on assigned course. This practical tt¡innrng formation you will save enough time on one radio operating . mine that stations are dteal to pay the special $1.95 price for the -emplete course. channels, and that the character of service laws, and PREPARED FOR HOME -STUDY EDITION is in accordance with treaties, This complete, low.priced course will give you all the NEW LIMITED needed to get ahead to the growing field of Rush your order to us today. You may not have another The FCC has 7 such stations. training experience regulations. Radio. No special education or previous opportunity like this. Only a small number of courses Baltimore; required. astertraadliuse. lessons s They are located at Atlanta; master and use ells Just likeenyou have reprinted to sell at the reduced price. You are protected Lakes, found this r the with our money back guarantee. Catch up with your radio Boston; Grand Island, Nebr.; Great stepping s to better Pedro, Calif. education. Begin studying this course this very week. Ill.; Portland, Ore.; and San final examination and to own or operate uarantee diploma Are foreigners licensed You must be satisfied course Is finished. Special 'radio stations in this country? No; this or your money will be price for en- FREE EXAMINATION COUPON privilege is extended to citizens only. Sta- refunded immediately. the first" hour tt of work. "of SUPREME PUBLICATIONS. Agents tion licenses are denied corporations LIST OF LESSONS 3727 W. 13th St.. Chicago. Illinois is an alien or PARTIAL Sh'a the complete Radio Course at the special reduNM which any officer or director Elementary Electricity. Radio Parts. latteries. Circuits. money back. 's Lew. Radio Math, price. 1 must be pleased. or will get my 1/5 of the capital stock Magnetism. Elesttvmagneta. Coils. 1.F. of which more than malice. Wattage Calculation. Induction. R.F. I am enclosing $1.95, the full price, sent postpaid. by aliens or Transformers. Condensers. A.C. Filter.. Reactance. is owned of record or voted Mixed Circuits. Vacuum Tubes. stare Gain. Detector.. Ship C.O.D. pay postman $1.95 and a few R F. Amplifiers. Superhet Principle. A.V.C. Ballast centsmp postage. their representatives." Tto es. Meten. Testing Methods. I,tsttuuInsota. Semi. Fundamentals. V.T. Voltmeter. Using the Oscilloscope. Can amateurs use secret radiotelegraph Alignment. Sound and Hearing. Public Address. Ampli- Naue The tien. Loudspeaker Placement. Microphones. Inverse code in international communication? Feedback Methods. Reef/1111M, Power Supplies. Auto Sets. servicing Short-Cuts. Case Histories. Rt loo Trans Address only code permitted amateurs is the Inter- mission. Modulation. Crystal Oscillators. Phouroll -. majority of li- Television Pei a .'I City State 233 national Morse Code. The BBuusiness. Extra Profit Ide Andres.many others. censed amateur stations use radiotelegraphy Commission's jurisdiction under the provi- exclusively. sions of the act. in international For what period of time are broadcast DATAPRINTS How does the FCC figure TESLA -OUDIN HI -FRED. matters? The Commission is charged with stations licensed by the FCC? In 1939 the COILS administering communication provisions of license period was extended from 6 months 20e Ea. in order for 10 agree- (Data and Drawings only.) certain treaties and international to 1 year. 40e States is a the FCC inquired into network broad- 36" Sp'k Tesla -Oudin Coil ments to which the United Has 11 K.W. Exc. Trf. Data. in many international casting? During the last fiscal year. a com- included FREE!) party. It participates IOe conferences involving mutual radio, tele- mittee of the Commission sat for 73 days, 8" Sp'k Tesla -Oudin Coil 700 (s1í K.W. Exc. Trf. Data. graph, and cable problems. In 1939 the listened to 100 witnesses, examined included FREE!) Commission established fundamental rules exhibits and 9,000 pages of testimony in se Sp'k Oudin; 110 Vt. international broadcast service inquiring into so- called "chain" broadcast- "Kick Coil" type 40e governing 3" Sp'k Tesla Works on and, for the first time, opened these chan- ing policies and practices. Ford Sp'k Coil 40e nels to commercial programs. Domestic 1" Sp'k Violetta Hi-Freq. Coil 40e pick -up and rebroadcast of noncommercial Model Warships -Get List of Plans international programs on a nonprofit basis JUMPER FOR CURRENT TESTS by the Commission in 1940. Induction PIPE ! was authorized I find it handy to use also licenses radio equip- For test circuits, ORE LOCATOR The Commission of tip -jacks which break the circuit, on and ships departing from a pair ment planes permanently fastened under Induction Type. Data 40e country. and a jumper this one of the jacks. Radio Type 40e Can the FCC censor radio programs? For current tests have the jumper free No; the Communications Act states: "Noth- jacks. For voltage tests, or con- and use the tip- More DATAPRINTS 40c each! ing in this act shall be understood plug the jumper into the tip -jack and use Commission the power strued to give the the free one for your meter. 5 Meter Superhet. Electric Refrigerator of censorship over the radio communications R. FRAZEE, % Meter Tr. & Rec. Resistance Measuring or signals transmitted by any radio station, New York, 20 A.C. Probs. & Ans. Bridge or condition shall be pro- 20 Telephone Hook -ups Weld. Transf. 2 K.W. and no regulation 100 Mech. Movements Armatures or fixed by the Commission which Hook -ups Rewinding mulgated 20 Motor Galvanometer shall interfere with the right of free speech Television Hook -up String 20 Elec. Party Tricks 20 Simple Bell Circuits by means of radio communication." Solenoids and Magnets Steel Wire Recorder! On what basis are broadcast stations -get list. Water Wheels or serve the {`public Fry Eggs on Ice! Turbines licensed by the FCC? To Photo - Cell and Relay and necessity," ac- Experimental Photo interest, convenience, phone Ring 4 bells : 2 Wires cording to the act. Because the broadcast Radio Control for 20 Tesla Tricks that Models channels are limited, it is important Diathermy Apparatus Polarized Relay they be entrusted to stations which have a Inductor Organ Induction Balance high sense of public responsibility. What hatter is definitely barred front the Special Prices: 4 prints $1.00: 10 for $2.00; air by the Communications Act? Lotteries Single, 40e each. Get New Catalog 100 A. and kindred enterprises, and obscene, in- decent, or profane language. The DATAPRINT Co. iVill the FCC consider complaint about a particular radio program? Yes; if the com- Lock Box 322C, Ramsey, N. J. plaint deals with any matter within the 295 RADIO -CRAFT for NOVEMBER, 1940 EXPERIMENTERS

HOW TO ELECTRIFY THE 2 -TUBE SUPERHET. The addition of a 2-stage, single -tube amplifie r, and a ruelilier and filter, convert into a full-fledged 3-way portable that gives ance 'worthwhile perform- anywhere the 2-tube experimental superheterodyne first described in Radio -Craft for June, 1940.

LEONARD LASKY

RECTIFIER , since it provides so much usable value in so little space at a minimum power cost. The 117Z6GT likewise wits chosen for the rectifier because it can operate directly front the line without a transformer or drop - PENTAGRID _- ping resistor. CONVERTERS The 1D8GT has a filament current of 010- ampere, while that of a 1A7GT is 0.05 - ampere, These tubes cannot therefore be hooked -up in series. If the two IA7GTs und one 11)8GT were hooked LOUD- -up in parallel, their total filoutent consumption would be 0,2- SPEAKER, ampere, which is more Rear view of the 3 -way than the 117Z6GT is rated to deliver; the series- parallel ar- (battery -electric), 4 -tube rangement portable, Comparatively finally adopted requires only 0.1- ampere :3 large batteries ensure at volts. A 3 -V, "A" battery long operating life was chosen to replace the 1.5 -V, cell used throughout in the original receiver. The plates and the summer, cathodes and long shelf-life during of the 117Z6GT are hooked -up in the winter period when parallel. in which connection they can supply a operation is mainly with total rated current of 0,120 -ampere, light -line power. which exceeds by a small margin the current requirements of the set t0.1-A. for the filaments und 0.011 -A, for the plates). The 1A7CT filaments are shunted by u 200 -ohm resistor, R9, which curries the plate current of the 1D8(;T hack to ground. One preen/Ilion MUNI be ohncv'rccf with Mix filu- 'Meut nrot n!yemedt: the set should not be turned on unless all the tubes are gout! and all sockets are fill' I. The reason for this is that if one of the IA7GTs is miss- ing or defective, the remaining one will have an excessively lange voltage applied to its filament, which may damage it. In operation from the power line, whether NU A.C. or D.('., honte -umde long remains OoSsCSSCS he following additional attri- the filament and plate current static. It is generally. sonner or later. boles needs of the set are supplied by the rectifier changed. A -tnór serper/'l. having independently of the batteries (except the 11 t Completely served faithfully for a self- contained 113 -volt "( " battery). A switch, Sw.2, on summer under A.('. 1),('. or battery the front varied conditions ut home and in the operation, using panel provides for change -over from field. only .1 tubes battery in its turn became u including the rectifier. operation. The switch is problem. To tear it (21 Jlinintunt arranged tu turn down or build it up, that was question. current consumption on off the filament of the 117Z6GT when the !tottery or power line. the In its original foret the set showed so nue), set is operating on batteries, even though 131 high - quality resistance - capacity promise as to be worthy of further develop- the line cord may be plugged into the 115 - ment. coupled amplifier. Only one trans- volt line, An amplifier providing loudspeaker former operation was an obviously -the output transformer-in The rectifier is followed by desirable im- the entire set. a filter of the provement; and the advent of winter. with resistance-capacity type popular in port:tblc (4) Generous 4 -in. P.M. dynamic speaker the return of radio activity indoors. receivers. Actually there are 2 filters, maul, provides excellent tone. one eleetriticntion as necessity, for the filaments :awl one for the plates. 131 headphone reception using the first The resistors in the filament stage of the audio side of the FEATURES amplifier provides filter serve also to ,Iron the voltage (app rox. ample volume and d;,turbs no one. 125 yoltst ut the output of The !.'ilion of these features to the Perfect the rectifier to tone quality if used with :1 volts for the series -p; .rules) many 1osstsse1 by the origi nul set results crystal headphones. Wooten t s. An in an all- purpose portable whieh is equal 161 Trtansformerless, ;attempt was aua,'t- to use the diode in performance choke-bs., power plate of the 111s('í' to sonic eommerei;al outfits supply saves weight. ,:nice. and iu an ANA'. circuit. employing 3 and 6 tubes. 'l'he A.V.C. cation vV;lS not ptu'ticulau'ly sat- stoney. The filament of the I 17Z' ('l The original isfactory. since only 1 2 -tube superhet. included the rectifier operates directly front the tube, the Ist- detec- following outs ta radin g fettu res: power line. tor - oscilhtor, was controlled, and the sen- flt The use of pentagrid (7) limn -free operation sitivity of the set was too -greatly reduced. tubes for both on A.t'. supply, The use of A.V.C. was converter curd 2nd- detector applications. (8) Compact. therefore aduatdoned truly portable construction, in the final version of the hook -up. (2) Electron -coupled, stable, non- radiat- is actually- less bulky than most coming regeneration at the fixed intermediate mercial port:ode- of comparable per- CIRCUIT frequency (hence the degree of regeaera- tion remains fixed, at any predetermined The circuit diagram. Fig. 1. shows the complete circuit level, regardless of adjustments of the DESIGN CONSIDERATIONS of the entire set. Prac- tically no changes are necessary tuning condenser gang). The IDBGT in the was an emus -t obvious choice original 2 -tube sul,cria-t. wiring. The completed set, as described herein, for the amplifier section Advan- of th. rec,.iver, tage is taken of the 1st stage of the audio 296 RADIO -CRAFT for NOVEMBER, 1940 EXPERIMENTERS

C13 `PENTAGR,D CONVERTERS AF PI R3 REG 1( S1T Al- t(Y'3)r 1ST t 2Na )) 1NDDÉT ME OHM0 05C. L 15T- OCT Bll1! W ROL "I 365 GREEN / MF. 134 'CRYSTAL 111 PHONES LI -M I-_ 4 IN. RIA S SPEAKER R11 CA. 7 USED C4iV OHMS MEG. BATTERY 10W. ÁOO.IE RED I COnTRNTROL c5 TICKLER -I `230 - ME, 2C-540 MMF RIO RLS C MMW, \ 30 OA- MW 130V. 150V. I _cu GRES IMF L2 \ a.1- C2 MF .1 1 MPz2-EG / M E C". r(as A C-DC-BATT REGENERÁTION CONTROL - CIO I CB ... RI, 1,5;500 1.000 MMEj , W. LACK Cl O. NOTE. R4 CI C22GANG 20.--- SECT. EitD (7,SaGT a C u FROMSú CHASSS) 1 t RTi 'RE R12 C21. C15 ^4.F.4561.C", ppp 200 ,5000 0. 5- 0.1- .30 OHMS. OHMS. MEG. MEG., MF- A.C.-0C. MF ÓÑMS ÓV. ., T W. /xW. 'nw. VIM,. 11W. 150V. FIG. l

the filament and panel by incans of fibre washers. Ninety carefully checked, particularly amplifier to provide greater volume for wiring. The set should be made to work jack may volts of "B" battery should be used to test headphone reception. The original and successfully on batteries first before opera- be insulated from for grounds in the wiring of the set he used, but it must now observable between tion on A.C. or D.C. is attempted. An ad- chassis and front panel. no continuity should be of the metal of the set or of the wiring, justment is provided in R15 by means requires 9 volts of "C" bias any component at The 1D8GT and panel. which the filament current may be set 90 -volt plate supply operating con- and the chassis pur- for the shown in the photographs, its proper value. For most practical It was decided to use a separate "C" In the set to set R15 dition. R13. R14 and R15 were mounted poses it is sufficiently accurate battery and leave the entire 90 volts pro- resistors However, anyone who below the chassis. It is suggested, however, at about 150 ohms. vided by the "B" batteries available for wishes to be super- precise may connect a would provide that they be mounted above the chassis plate supply, because this must collectively millianuneter in series with R15 and adjust power handling ability on the because these resistors is exactly maximum 11.5 watts. In any case, R15 so that the filament .current part of the 1D8GT. However, only a 71G- dissipate about this adjùst- they should be mounted as far from "the 100 milliamperes. Theoretically volt battery is necessary because the 1.5- nrent should be made when the line voltage filaments of the batteries and condensers as possible. volt drop across the be drilled in the back is 117 volts, according to the R.M.A. be used for the balance, mak- Some holes should 1A7GTs may of the cabinet to provide 'ventila- The completed set will operate in much ing a total of 9 volts. and top tion and let out the sound waves coming the same manner as the original 2 -tube from the back of the speaker. superhet., with the added pleasure of loud- CONSTRUCTION speaker reception. (The article on the orig- In rebuilding the set some rearrange- OPERATION inal set should be consulted for details and ment of parts was necessary to make room Before placing the set in operation for information not given here.) for the loudspeaker on the front panel, and the first time, the wiring should be very herein, shifted The completed set, as described consequently the batteries have been portable which anyone can of the cabinet. The speaker is a universal to the rear be proud to own. It is certainly a remark- opening is finished off with an escutcheon bears out the conclu- a piece able performer and plate taken from an old dial, and tests on the 2 -tube The D.P.D.T. sion, reached after the of coarse, open -weave, cloth. superhet. showed its possibilities, that the switch, Sw.2, in the lower- left -hand cor- better and more eeo- -hand cor- wog in now clear for ner, and a hole in the lower -right oomical xnperheterodynes. cord, complete the front ner for the line here given includes panel arrangements. See Fig. 2B. The List of Parts on only those parts necessary for adding the The 1D8GT und 117Z6GT are mounted original as shown in the drilling diagram. amplifier and powersupply- to the the chassis For the List of Parts for Fig. 2A. The socket of the latter tube is 2 -tube superhet. and 2nd -detector stages. sec 1a -in. above the chassis by the converter raised about June, 1940, p. 747. spacers on the mounting screws in order Hadio -Craft for to clear the potentiometer, Pl, and switch, Sw.1, which are below the chassis. The LIST OF PARTS by filter condensers are bunched together CONDENSERS a rubber -band and held against the front Two Aerovox paper tubular. type 284, 0.01 - panel next to the speaker by an aluminum mf., 200 volt, C13, C14; strap. The output transformer is mounted One Aerovox paper tubular type 284, 0.1- directly on the speaker on lugs provided inf., 200 volt, ('15; on the speaker frame. One Aerovox electrolytic type PRS 150, 40- To prevent the possibility of short -circuit mf., 150 volt D.C. working, C16; or shock should the ungrounded side of the Five Aerovox electrolytic, type PRS 150. power line be connected to the "A -B" -side of 30 -mf., 150 volt D.C. working, C17, ('18, the receiver circuit at the same time that C19, C20, C21. the ground terminal, chassis, and cabinet to ground, it was decided to RESISTORS are connected One IRC type BT'._, 200 ohms, 12- watt. isolate the wiring and parts of the receiver from the chassis and cabinet, and R9; entirely Two IRC type BT1i2, 1 meg., ',-watt, RIO. to provide an R.F. bypass condenser, C12, of the wiring and R11; between the "A -B" -side IRC type BT1_, 0.1 -meg., b,-watt. the chassis. The ground binding post is not One the front If the R12; insulated from panel. 1RC type AB, 500 ohms, 10 watts. were used as part of the Two chassis and panel R13, R14; wiring of the original receiver, this should ohms, 10 watts. condenser One IRC type ABA. 300 he corrected. Also, the tuning Front view of the completed superhet. It differs but adjustable, RIS; and dial must be insulated from the chassis slightly from its original appearance. 297 RADIO -CRAFT for NOVEMBER, 1940 EXPERIMENTERS

FIG. 2 The chassis and front panel layouts of the electrified 2 -tube superhet. show the locations of new holes required for ampli. fier and rectifier tubes. (For locations of other holes in both chassis and paner, see preceding article on the original 2 -tube superhet.)

Two IRC type BTitz, 1 000 ohms, i,z -watt, Two Amphenol R16, R17. octal sockets, type MIP; One Burgess 3 -volt "A" battery, No. 2F2H, TUBES B5; One National Union type 1D8GT; One Burgess 7'.s- volt "C" battery, No. 5540, One National Union type 117Z6GT; B4; I * "It's the best way I know to MISCELLANEOUS One Cutler -Hammer D.P.D.T. toggle switch, I be sure of top performance!" One Utah 4 -in. permanent magnet dynamic Sw.2; speaker type 4PY1, with output trans- Yes, sir -servicemen, former Line cord and plug, escutcheon plate for amateurs, No. 8772; speaker hole, hardware, i engineers all know that Ohuiite etc. Resistors work for you day in and day out - dependably! F.C.C.'S MAILBAG They're standard, too, with de- (No. I I signers and manufacturers of o f a Series) NEW YORKER amateur, commercial and broad- A inquires "whether a cion. You will be interested company operating a commercial to know that cast equipment. Next time, in- radio all Federal employees under Civil Service station is under a duty to quote rates for have stall "Cordohms," "Dividohins." time not been required to submit fingerprints sold and to sell such time if its for a number of years." "Brown Devils," or other Ohm - rates are met." Under the Communications Act a radio Under the circumstances, the Commission ite Parts. See Your Jobber. broadcast station is expressly regrets declared not to be a "common that it is unable to accede to re- carrier." quest by a MAIL COUPON NOW! Accordingly, except the provision which New York transformer firm relates to candidates that exceptions be made to permit amateur for public office ex- communication rOHMITE MANUFACTURING COMPANY plained in an earlier information release, with various scientific ex- 4895 Flournoy peditions outside St., Chicago. U. S. A. a radio broadcast station is under no of the country. obligation to quote rates or sell time. Hence Although the Commission can not, as a SEND FREE CATALOG 17 a radio broadcast station is unlike some rule, interfere in local interference prob- Name other classes of radio stations-notably lems, so many residents of Dennison, Ohio, radiotelegraph complained about Address and radiotelephone -which serious interference to have the status of common carriers and local radio reception that the Commission City State are required to furnish service in accord- has asked the Ohio Power Co. to cooperate ance with tariffs filed with the Commission. in remedying the local situation. From the same city conies a lone letter A West Virginian wants to obtain a protesting certain restrictions imposed upon transcript of a certain radio broadcast. Sta- amateurs at the present time. By way of tion licensees are not required explanation, under law the Commission replies in to furnish program transcripts to the part: public, nor is the Commission empowered "Although it is realized that these orders by law to secure copies thereof for in- will probably cause inconvenience and an- dividuals. noyance to some of the amateur operators, To a Pennsylvanian who complains about the Commission feels that the recent restric- interruption of programs for station iden- tions and requirements are not only en- tification, the Commission points out that tirely justified but that they are necessary whereas such announcements are normally actions in the interests of neutrality and required on the hour and half -hour, these national defense. From the responses re- may be dispensed with if they would inter- ceived from amateur organizations and in- rupt a single consecutive speech, play, reli- dividual amateurs throughout the country, gious service, symphony concert or operatic it appears that the amateurs themselves rendition. are appreciative of the reasons necessitating A Chicago woman objects to a program the adoption of these orders and that they broadcast by a Dr. Brinkley. The program will fully cooperate in their enforcement. emanated from a Mexican station, over As you are undoubtedly aware, this Corn - which the Commission has no jurisdiction. mission is cognizant of the valuable services Since rendered the Commission lacks jurisdiction to radio and the nation by its in the matter, it suggests amateurs and has to a Palm Beach on numerous occasions woman that she submit to independent sta- made public its appreciation of those serv- tions and networks ices. The Commission a prayer that she wants does not believe that to be broadcast twice daily throughout the the order requiring more detailed proof of United citizenship States. than has been required in the In response to a query past can be construed from Chicago, the as an indication of Commission advises that there is no rule distrust of the American amateurs. This is or regulation pertaining also true as to the to the solicitation ©HMllT1E commercial operator to of funds over the air, and that the matter RHEOSTATS RESISTORS whom that order also TAP WITCHES applies. Requiring is one within the discretion of station man- fingerprints is not an indication of suspi- agement. 298 RADIO -CRAFT for NOVEMBER, 1940 RADIO DEVELOPMENTS YOUR JOB IN THE AVIATION INDUSTRY

of this article is to acquaint the reader, especially the novice The purpose with the and any radioman not working in the Aviation Radio Industry, the Aviation Radio Industry with which they may many branches of the in a very profitable way: and to outline generally, associate themselves Radio qualifications and training necessary for specific fobs in the Aviation. Industry.

CHARLES J. SCHAUERS Taco,uu, 11-ash. Staff Sgt., 7Jrd Bombardment Squadron (M) GHQ AF, the specific job. This may he accomplished in following manner: by giving a test in gen- and eral radio principles. a code speed test, proficiency test; and then, if possible, typing prin- a teletype speed test, shop practice ciples test, and a psychological examination for determining the prospective aviation public service. Left, modern installation radioman's adaptability for also be conducted Sperry Automatic Di- An investigation should of education and rection Finder, In a Doug- of the applicant's previous Plane. Spe- habits. las Transport the training is needed to After this has been consummated, cial choice these instruments tests are graded and the applicant's service our young no "slip- shod" me- is considered. It is found that . in a ground chanics wanted here! radioman desires to operate radio station for the airliners, a specific -met ya,. Co. Plato job. We then look up the qualifications necessary in order to obtain such a position. The applicant's appearance is 'way above were average, and his scholastic marks investigated and found satisfactory. Most airlines require a 2nd Class Radio- telegraph license, with a 2nd Class Radio- one telephone indorsement. Ile must obtain that every- the past few years, most radio This doesn't mean, however, of them. DURING this field on Servicemen, amateur radio operators, one who is desirous of entering We now find that he saust "brush up" But it does mean working generally in the need be a college graduate. his theory in order to puss the examina- and those industry is in need radio industry, ut one time or other that the aviation radio tion given by the Federal Communications who have properly qualified income in contact with Aviation Radio in of those only, Commission. Ile could plug diligently, have and who have and it be at air shows, visit- by obtaining proper training, dividually, at different textbooks, some form. Whether "build -up" ex- ing airlines offices, aircraft radio factories, also obtained the necessary peruse volumes upon volumes of radio or attending experiments conducted by many perience. theory, but this unsystematic method leads manufacturers of aviation radio equipment. This "build -up" experience is obtained in to partial and improper training. They have realized too, that the aircraft various ways, but all in all, the aviation What shall we do? offers many opportunities, but radio industry is looking for men who will We decide that he needs a school, pref- radio field a most of them were at a loss as to what they need no large amount of extra training in erably u resident school, which offers know, what jobs are actually order to qualify them for their position well- rounded course in general radio theory, should in the cer- available, the specific qualifications neces- after acceptance. along with specialized training where to apply for those jobs. There isn't a job in the entire industry tain branch that he has picked and found sary, and operating. After conducting an investigation as to that isn't a responsible one! to be fitted for, viz., airline radio the opportunities offered in the aircraft EFFICIENCY is the key -note of success After his graduation from school, and radio industry, the author compiled the data here! after passing the government examinations, contained in this article. The average radio technician not only does he belong to the fold of the "full must he a quick, systematic thinker, but fledged" airlines radio operator? Decidedly is TRAINING he must also possess a very retentive mind, not! Now, some of us wonder, "Where neces- Throughout the investigation, it was as there are many small, important details he going to obtain the experience inex- found that there are many radiomen in the that he must know from time to time, sary?" Most airlines will not take radio industry today, who Wray, with various which much to his sorrow are not often perienced radio operators unless they show amounts of training, qualify themselves for repeated. This may be attributed to the more than the usual initiative and learning very pleasant as well as remunerative posi- rapid progression of this highly specialized ability. tions in this industry. But the outstanding field. If our young novice shows evidence of the point of the entire investigation disclosed virtues, he may be put to work systematic two above this important fact: proper, SAMPLE ANALYSIS as an extra operator, working with one or a branch MUST be who at training for specific we were to take a young radioman, more experienced radio operators, If This is obtained. say an amateur radio operator who has the same time, act as instructors. in conjunction with general a standpoint This training, had, let us say, I years' experience, and often quite impractical, from will adapt many radiomen every day. radio experience, start to train him for a specific position in of efficiency, but is being done gigantic, but highly S to positions in this aviation radio industry, how would we When our radioman has spent from industry. the operator in technical do it? months to a year as a student made (by training), never a Radiomen are There are many ways in which the may the station, he may be employed as regular born! accomplish this, but for the sake of brevity, operator. radio Serviceman or the general operator! The let us limit ourselves to one method. We've made our airlines radio who contemplates entering the not show radioman, would be to give On the other hand, he may radio profession has many things The first logical step and learning aircraft an examination in order more than usual initiative i.e., his training, experience, the young man to do? to consider, adaptability for a certain ability, then what are we going adaptability, and his general qualifications. to ascertain his 299 1940 RADIO -CRAFT . for NOVEMBER, RADIO DEVELOPMENTS

OTHER RADIO DUTIES There are a number of answers to that question. But the logical one is, to take whatever job is offered him in the aviation radio industry until such time as he may be able to take the job for which he was trained. This is the secret to obtaining a specific job in aviation radio, Day in and day out. there are men who come to me and ask, "What are the general qualifications necessary for an aircraft Can YOU put one of radioman ?" these together? Picture Well, to tell the truth, there are very at right shows construc- few "general" qualifications, they're all tion of loop antenna for specific. This is true because there are many radio compass receiver branches in the . this takes aviation radio industry - .. training! which require different training. different Photo -CCs Mrs. experience, and different interests. Cu. There can be no set rule as to what a man should know generally; his knowledge must be specific when working with aviation radio. However, there are radio operators in airline stations who could readily qualify as a line technician, servicing aircraft radio equipment in aircraft. There are others who can repair and install equipment, but who cannot efficiently operate a station, or they do not have the ator, he should hold a Weather Observer often pressed general appearance necessary to work certificate, for properly trained installa which is easily obtained after tion men. Those around u ground station. a few hours' study. possessing the following, For simplification. qualifications should have no we will list the many The pay of airlines radio operators trouble in positions offered in the Aviation varies "landing" a job with aircraft manufactur- Radio In- from $85 per month (beginner) to ers employing dustry, the qualifications necessary, and the $185 per month, aircraft radio installation approximate and advancement is de- technicians. remuneration. We also will pendent upon ability and initiative. list most of the duties performed. One must possess a Radiotelephone 2nd Radio Operator in Aircraft (Airlines Class license, Airlines Radio Operator (Ground Sta- Commercial Transportation - preferably with Code indorse- tion). Companies).- ment, if he is to obtain work in final -The applicant must possess at least The applicant should possess assem- n 2nd Class Radiotelegraph the sunre bly and testing of the aircraft radio license, if code qualifications as the ground station oper- transmitters. is used, with a Radiotelephone indorse- ator. However, he need not have had tele- He should be a graduate ment. type experience. But of a recognized Some a "must" is. that he technical school which has given "get by" with 3rd Class Telephone should possess a 2nd Class training licenses, the new restricted Radiotelegraph in aircraft radio installation and main- license. How- license with 'Phone indorsement. The ap- tenance. ever, 1st Class licenses are preferred. plicant for Ile must have had at least 3 years' this job must be healthy, and be experience as a radio The appearance of the applicant must be able to pass the "flying" service technician; considered because physical exam- must be mechanically inclined, and under- of his contact with the ination required, before acceptance; and stand public. He must present a trim, clean -cut those thoroughly the intricacies of aircraft susceptible to air -sickness, are barred. radio installation; and appearance at all times, and should have Many times during he must be able to had at least a flight, the aircraft follow blueprint instructions and the 2 years' experience either as radio operator must assist the navigator com- an amateur radio operator, commercial in plicated wiring diagrams. ship taking bearings by utilizing the radio com- The pay operator, or as a Serviceman, and be pass for the above job begins at a or the radio direction finder. This is about 48c per hour and reaches graduate of a recognized technical school. one of his many important a high of His code speed, if code is tasks, besides $1.96 per hour. used, should be in obtaining advance weather reports, trans- Aircraft Electrical the neighborhood of 30 to 35 words -permitting arrival Technician. -Every ra- minute. schedules and messages for dio technician employed either in passengers. His job is the main- He a very responsible tenance or installation of aircraft should have a typing speed of from one, and is not be looked radio 50 to 75 words -per- upon with dis- equipment, is u potential aircraft electrical minute, and if possible, favor because of the flying element. and quite desirable, should technician. This is a branch of the field not have had tele- Flying today is the supreme in trans- very often type training and be able to operate the portation! explored by radiomen. standard machine between This is the field that all radio Servicemen 30 and 45 words - The salary paid aircraft radio operators should seriously per- minute. usually starts consider, and snow is the He at $125 and sometimes climbs time for consideration. should have some business ability, and as high as $350 per month, depending should be able to converse intelligently upon The average radioman with his under- the company and the duties. standing of the general principles about the services that his company offers Factory Radio Installation of radio the public, when asked! Technician.- as a whole may. with a certain amount of Aircraft manufacturers, making airplanes study, make himself In order to be a "top- notch" radio oper- for military eligible as an air- and commercial use are quite craft electrical technician. The many things which he needs to study and understand are: Ignition systems, electrical wiring diagrams, methods of electrical wire installation, the working principles of gauges which are electrically operated; and, the general principles for the proper installa- Modern lest equipment tion and maintenance of electrically -oper- like this illustrated at ated controls. left is needed for the If the applicant has had previous ex- proper installation and perience in wiring radio receivers, wiring maintenance of aircraft modern homes, or /and working with elec- radio equipment . . . trical wiring in other branches of the in- you have to "know your dustry of aviation, it doesn't take an im- stuff" when the radio mense amount of time nor effort to make equipment you service is himself eligible for work in the electrical to be operated aloft. department of an aircraft factory. Photo-11e .r >Ifg. co. Although the electrical department is not specifically an integral part of the radio installation and test departments, it aloes have a bearing indirectly upon the completed radio installation, and it is well that the radio technician employed as a factory 300 RADIO -CRAFT for NOVEMBER, 1940 RADIO DEVELOPMENTS

control towel man, have partial understand- has the job of designing installation ground radio station equip- ing as to the methods used in wiring modern equipment, and ment for communication with flying aircraft. aircraft, even though he is not directly con- starts at about with the work. The pay for this branch cerned a year, and sometimes will reach a The salary for the electrical technician $1,750 the factory radio high of $6,500 per year, depending upon averages about the same as the the designer. technician. key position assigned to installation is assured those who show In any aircraft factory, the work on most Advancement basis. initiative and more than usual ability. equipment is performed on a piece From might have the job Aircraft Instrument Mechanic. - That is, one radio man working with air- installing the receiver, another the trans- time -to -time, radiomen of receive the opportunity to work mitter, another the antenna; still another craft radio in delicate instruments, such as thermo- All the latest developments has the job of actually connecting up and with radio couple ammeters, voltmeters, and milliam- nationally advertised testing the equipment. by working parts, plus many items out of be remembered here, that no meters. The experience gained It should the radioman Everything you specific job a radioman might with these instruments, gives manufacture. matter what for further train- now within he should know something about a splendid background need in radio, be doing, mechanic. what is actually going on around him. This ing as an instrument arm's reach. Easy to order ... acquaint himself in a The duties of the instrument mechanic easy to have what you want! means that he should repair, cali- general way with work somewhat closely are concerned mostly with the his, because in aviation ra- bration, and installation of aircraft instru- Choose your favorite test associated with indicator, auto- dio, every part is "inter- dependent." ments such as the flight equipment here. Enjoy real rate -of -climb indicator, and the The Aircraft Radio Service Technician. - matic pilot, savings. Every known name is is a field not yet flight indicator. Aircraft radio servicing and represented. Stocks are always by men who know their This is a very highly specialized field overly crowded The aircraft complete and up -to -date. This is the branch where training special training is needed. "stuff." man for the job if Order by catalog -it's quick is a dire necessity, and constant study a radioman is the logical requisite. The qualifications for he obtains that extra training. and it's thrifty. particular in factories, the job of aircraft radio servicing, if a job Work in this field is to be had airports. More models to choose from is desired with one or more of the large for the airlines, and at private servicing agencies established throughout The pay for this job varies between $1,400 and more P. A. for your to $3,700 per year, and it should be seriously money! In features, perform- the country, are: familiar with The applicant must have had at least 2 considered by those who are ance and watts-perdollar, on home and auto sets; sensitive radio instruments. leads. Three com- years' experience gen- Lafayette have been, or is, an amateur radio Aviation Radio Merchandising. -The portable, per- should here are that the appli- plete lines of operator; and above all, should have had eral qualifications manent and mobile sound either a good cant have had specialized training in gen- specialized training from systems. A model for every or a reliable school offering eral sales and service. residence school planned busi- purse and purpose. an extension course covering aircraft radio He should have had a well- ness education coupled with a technical as a whole. fea. for a radio Service- education in aircraft radio. Compare Lafayette Radio It is quite possible line, in aircraft radio service The pay for this job depends upon tore for feature, line for man to engage field for Why from his own shop if there is no immediate ability and is a very lucrative and dollar for dollar. service agency in the vicinity of the home those who are willing to work. pay more when Lafayette but this requires an immense Aviation Radio Civil Service Jobs. -The offers all the wanted features airport, and other gov- amount of equipment and parts approved Civil Aeronautics Authority and beauty of styling for so hold periodical exam- for aircraft radio equipment. ernmental agencies less? In this book, 64 which afford many radiomen the much of the radio service technician inations beautiful models to choose The pay opportunity to better themselves. The ninny for an established radio service -day Trial. working jobs offered are: from. 30 Home agency varies. Depending upon the amount on air- usually runs be- Radio operator (senior & junior), of work done, his salary mechanics working in Nowhere else will you find so as high as $300 per month. ways, instrument tween $150 to government depots, radio repair technicians, complete an array of nation- Aircraft Radio Design Engineer.-This maintenance amateur transmit. the applicant have a aircraft radio installation and ally-famous branch requires that and many engineering jobs. ters, receivers and ham equip- college education in radio engineering. technicians, for these jobs are ment. It's a catalog within a -set" design engineer, The qualifications Unlike the "home obtained by writing to the CAA and catalog, and low Lafayette the aircraft radio designer must be able readily consulting the Civil Service Secretary in prices make it a book you'll to design equipment which must stand up under very strenuous and trying conditions, your district. want. Time payments. and which must come up to the Civil Aero- Authority standards governing air- MILITARY AVIATION RADIO nautics Last but not least on our list of positions BIGGER IN Be sure to see the corn- craft radio equipment. are the mili- plete line of low- priced, branch of the in the aviation radio industry EVERYTHING! The qualifications for this States. The United auto radios, the newest rec- industry are high. They have to be! tary forces of the United easy -to- attach aviation Army Air Corps, the Naval Aviation ord players, radio tubes, tools and guide This is the branch for the man who has States Section, Coast Guard Aviation Services, books. They're all here and priced to save worked in aircraft radio for at least 2 the Marine Aviation Section. These you real money. years; who has graduated from college, and the and who services offer the young men of today NOW send for your copy of the majoring in radio engineering; obtain the neces- RIGHT 1st Class countless opportunities to in radio -this year bigger has at least a Radiotelephone for qualifica- greatest catalog This is sary education and experience The coupon below, license with Code indorsement. and the field offers than ever. the final testing after tion in civilian industry, moiled of once, will bring o RUSH necessary if he does with good pay. good security FREE copy to ou. design. COUPON Due to the steady trend in aircraft radio The qualifications of the Army Air Corps. be a equipment design, and the many exacting generally, requires that the applicant y NOW CAA, it is individual, able to pass the physical e' standards as set down by the healthy quite necessary for the engineer working examination given; with no dependenta, as a designer to be constantly "on his toes" have at least a high school education or M In MI ages of ® as new innovations and aids to its equivalent; and be between the insofar RADIO CORP. Dopt. 3L concerned. 18 and 35 years. LAFAYETTE - safer flying are ILL. applicants, The United States Army Air Corps offers 901 W. JACKSON BLVD., CHICAGO, When manufacturers desire NEW YORK, N. Y. they usually choose neat -appearing, well - training of the highest standards in Avia- or 100 SIXTH AVENUE, and Repair. experienced, keen -thinking young college tion Radio Operating I Rush FREE Catalog No. 82. students who have had the prerequisite ex- Actual operating aboard aircraft, in perience. ground stations (control towers), teletype NAME design engineer not training, weather forecasting and observa- The aircraft radio ADDRESS only designs aircraft radio receivers, trans- tion, and a complete, well -rounded training program, is constantly in session for keep- mitters, interphone equipment and radio cIT'S STATE well of the times, and VA$TE ON rENNY aids to navigation, but he also sometimes ing the men abreast IN COUrON RADIO -CRAFT for NOVEMBER. 1940 RADIO DEVELOPMENTS

well- trained in the field of Aviation Radio. of the jobs offered in your particular line. SERVICE The Army Air Corps also offers a special It isn't necessary MANUAL course in instrument for the applicant to write training, and an op- a lengthy letter giving details of his DIAGRAMS YOU NEED portunity to learn also, the ex- operation of periences, qualifications etc.; everything is the Link Trainer, etc. This education is covered in 4AGRAMS had detail in the application blank. by passing prepared examinations After the application blank OF MOST which determine the applicant's is filled out and adaptability mailed it is usually from 1 3 and speed of learning. to weeks until SERVICED acknowledgement is received. .0.1 The Coast Guard, Marines, aor rapar, slim. and Navy, If it is possible for one to visit the RADIOS also have about the sane training as the main office, and obtain HOW TO SAVE TIME Army Air Corps. an interview with e the irruit data, hints, Information After Communications Superintendent and Ot 5 t- time-steers and Loney- makers considering the many advantages personnel tut you. Let manager, much may be accom- 9y, this diagram manual offered by the military forces it is readily 4 Its your guide b. bigger pn,a, s and plished. e ire t ark. Whyy pork apparent that these advantages should be For ndf ulded hen` t out f 5 dla employment in any branch of the G YOU r taken into consideration )ou will turf reed are in - by every able - aviation radio industry, the personnel man- i,4 -.1 ht thi. new, low- prittl bodied young American who u.d. C,anplll by M. ftelwian, desires the ager of the different concerns should be h idle err, ¡Mina., Tailed author, best in training and who has the desire to consulted, with a final :other of Radio in Chicago Scioto!, better himself. talk with either the shop superintendent or plant foreman. In COMPLETE NEW EDITION Information concerning the training of- these interviews with either the communica- kt your rutty of this radioman's fered by Iuerst tirar-sacer. Na need to the Military Aviation Services tions superintendent or the shop foreman, vend big money for bulky, spare- may be sitting had by consulting the recruiting it is well to bear in mind their position. manuals. Only $1.152 lu- office t,rings your eoPY of lie in your city. They know their jobs or they wouldn't be 95 bandies( on- the -lob" handbook there. ,f useful diagrams. (Outlets tteN A brief outline of your experience date. l Well printed diagrams, EMPLOYMENT APPLICATIONS and training, with your intentions u Li, alignment data. and part: should Il:,s be given, with OSTPA ID Large sin. 81;,. x It In, he,. Many of you readers will begin to wonder your past record speaking :111 127 rdhegra,u -. b: pa_e- mfg. as to the method used in getting most of for itself. Your prospective employer's time FREE EXAMINATION COUPON the jobs mentioned so far. "Any road which is important, yours is also. Don't waste it by talking about Sapnme Publiemtion. leads to a good end, is always the hard one your "Cousin Tim's trans- 3717 W. 13th St.. Chicago. 111. mitter, .shin complete Service Manual. I may return the to travel." or your ideas on a new type of n,.:a1 for a full cash refund if I am nut satisfied. Commencing antenna. C I ion with the airlines: it is $103, send postpaid. known Above all, be brief, and be yourself. (Pre- send e.o.n. I It I.,y , .,,man that each large concern $1.03 and a iow throughout tentiousness. no matter the nation has u personnel department.'l'he how small, is always noticed. i If you Name first proper step would be don't know your job. to either drop your interviewer will usually in personally and see the personnel manager know that 115 ton. The Aviation Radio on appointment, or to write a letter Industry is the giving one branch of the industries of your qualifications. The former is quite today that proper, but it roan cannot walk into by a "bluffy" sales - the latter is to be discouraged. talk. ELEMENTARY The addresses of the different airlines You must know your job when you may be had by consulting work the aircraft di- in Aviation Radio, because radio is being rectory, or by visiting your local airport depended upon mare MATHEMATICS where this information and more every day may usually be to add to the safety of modern aircraft as obtained by asking the airport manager; they fly over land and water. EASY - SIMPLIFIED PRACTICAL or it may be obtained - at a branch airlines If you are now working in the aircraft office. radio HERE is a book- for the business man, the tech- field, you can feel justly proud, be- nician and Each concerti throughout craftsman explaining and answering the United cause even though you may be just a small every operation and meaning with lilt lag States having a personnel office Illustrations and examples. has printed "cog" in the wheel of a big industry every It le the key to a simple understanding application blanks which are perplexing of many usually sent little bit that you do, helps problems in daily life. to an applicant upon to publicize In clear, positive and definite language. the author request. Usually the the slogan, "AIR TRANSPORTATION, clarifies application blank SI' :: y n ill have a list reader toeovereome study ONWARD WiTH THE AID OF RADIO!" of mathematic. the A real home study - course in mathematics for the student or the man who wants to achieve proficiency or desires to brushup on hie knowlsdgs. Entire Chapter we Special Math- AN INEXPENSIVE TEST SPEAKER OW ematic. roe. the Radio Technician SOME Serviceulc: do not use as test CONTENTS OF 800K speaker at all, and a large number of LL CNAnaa 1. ArithmetlyAaaitlon- fion -Division Subtraction- etultlpll then: do not use one that is truly universal. CHAPTER 11, Factoring and Cancellation- leraetlonr As for myself I certainly is penvosetro. Nano -and troN,rtion. -Dcl would not be with- CHAPTER 111. The Metric System. out one, and I would not CNAn[R IV. Now to Measure sorteee put up with one v.c. IGoeltt 1Power and Capacity that was not universal or that wastes CMAeT[ YV and tnrolutlon -ROOt tini,- urn. and avow. when this one can be CHAPTER fee Ma built in half an hour ,s.10 P-ae-P ual Technical Man- .: Craften - at a cost of about $4 for new rconversionsn 1eil th asapha the speaker, VC. Curve Plotting-Logarithms-Use of parts and (rM5 AN the Slide Rul ONLY all. úaOóCó CHAPTER VII. fienta' Mathematics Any good the for -grade, permanent -magnet dy- SPEAKER FIELDS) CNAn[R RadioVIII. Technician. CommercialCaleulatiene- 50e namic speaker rated at 5 watts or VC '.b,p pBe- P interests - DI.ounte - Short Cut POSTPAID more Arith with a voice coil impedance of CHAPTER mIX. Weights and utaur- 6 to 10 ohms Deeful Table.. will do for the speaker itself. The output RLw..viry .Hathemnrini cos S. serf' d ad:r., se y.ste pool. ^lpletes the twin:_ Send Stamp., transformer is a good -grade Cash or Money rder. universal out- All parts are mounted on plywood put unit, 1 end of whose output is (vall- connected Soardl, Parts used other than the speaker IEI:NNIFAX to 1 side of the voice coil. All the other taps and transformer I017 S_State .-s are 10 -jacks. RC -1140 Chitapo. Ill. are taken to nn tip 4 phone tip -jacks the panel, while tip:, and 3 alligator the other side clips. The alligator clips of the voice coil terminates and 3 of the phone tips in a phone tip to match different are used in making tubes. the 3 leads to connect the test speaker to Leads are also brought out from the voice the set being tested. coil itself to 2 tip -jacks on the panel. Bring- W. T. iIkl.t.OWKLL, ing the 3 primary wires out to tip -jacks Idabel. Okla.

BOOK REVIEW the tit tell (bon of its Pete lens. The book has been written for students with net elementary knowledge A TEXT Ls of Light who are read- 11006 ON 1.11./11', A. W. Barton ing for university (1939). Published by Longmans, scholarships, etc. The first part Green & Co. of the book treats geometrical Sire. 6 x 9 inn., cloth cover, 272 optics lia n Reien- illustrations, 426 lific analysis of lenses pan. Price, E3. and mirrors. The remainder of the hook is devoted to answering the question. To some technicians is book of this title might "What is light:"'. The lank concludes with seem far afield from radio. However an the rapid account of the photoelectric effect and Compton expansion of television and other types opera- of effect which demand a revival of the corpuscular tion in the ultra -shortwave region. and develop- theory in :a new form. Note that ments in the use of the electric the book eye, make it assumes a prev-iols elementary acquaintance with necessary that Radio-Cm jt bring this hook to the snbjeet. 302 RADIO -CRAFT for NOVEMBER, 1940 RADIO DEVELOPMENTS

S.S. AMERICA'S RADIO

. ß..1,,r "', $17,500,000 flagship of the U.S. Lines.

'i`nnst liner ever built in the U.S. is now on the S.S. Aaurira. Main radio room of the S.S. America. Emergency set -up aboard The Wrgtstnand A 50 -watt emergency transmitter operates at alarm, give the America u code and voice reserve RADIO equipment -valued altogether and cities on either emergency generators or a aboard the S.S. America, this link with all the important ports batteries; an emergency $50,000- world, and other ships at sea. 2 sets of storage country's new queen of the seas, is of the crystal receiver operates without batteries the finest and most comprehensive ever in- A switching panel affords selection of or tubes! stalled on an American luxury liner, any of the 5 receiving doublet antennas A 75 -watt radiophone on 2 to 3 mc., in- Charles J. Pannill, president of the Radio - for either of 2 high -frequency receivers. stalled in the ship's chart room, is used only marine Corp. of America revealed last Switches also control 4 loudspeakers for for shipping business (communicating With month coincident with the vessel's arrival monitoring by speaker or earphone. Other tugs while docking, and with the pier and in New York harbor. It is the first case in switches enable a connection between any home office while the ship is in the harbor). which an American passenger ship has had of 4 receivers and a loudspeaker on the The 13 antennas aboard ship include the its radio installation planned and designed ship's bridge. 2 lifeboat antennas, radio compass loop in advance of the vessel's construction. main radio- antenna, 75 -watt radiophone antenna, 5 is in charge of 5 Still other panels contain the main flat -top The ship's radio room including u speech in- doublet receiving antennas, A total of 8 radio trans- telephone controls -V and the forward in- radio officers. verting or "scrambling" device to obtain antenna, horizontal O receivers, a radio compass (see antennas. mitters, privacy in radiophone conversations. verted-V photo on cover), and a radio automatic

BROADCASTING AN AQUAPLANE RACE WITH 2 land stations, an airplane station and a seagoing station in operation, the Don Lee Broadcasting Sys- tern for the 6th consecutive year last month again established one of the most elaborate set -ups ever devised to cover un outdoor event - the Catalina -Hermosa- Manhattan Aquaplane Race. The "ironing -hoard derby" is aired coast - to -coast over Mutual. Frank Kennedy, Chief Engineer of the Don Lee net, maintained headquarters with 100 -watt KABB at Hermosa Pier, with cueing and communication facilities to all points. The KILT remote pick -up truck was used as the base for u 60 -foot antenna. In addition to this, elaborate amplifiers and switching systems were used to coor- dinate all points and several receivers were used to monitor. With Kennedy at this point were technicians Robert Murray and Robert Bullock. At another spot -Manhattan fier, a mile away -were announcer Stu Wilson and technician Roy Raglan at an announcing and Game cutter Marlon did its part in a land-air- and receiving set -up. 100-W. transmitter aboard the Cali!ornia Fish Technicians This Catalina Pacific Coast. 3rd broadcasting unit Kennedy hookup to . For the ocean TurnerAman the equipment in the cabin established KABD, a 100 -watt shortwave left, and 303 RADIO -CRAFT for NOVEMBER, 1940 RADIO DEVELOPMENTS

transmitter aboard the California State Overhead, APORTVNlTY AD-LETS Fish in at trim Beachcraft high -speed Adverthiementa in this and Game Cutter Marlin. This section colt 15 rents a not l trans- airplane toe each Insertion. rode technician Bob Moody at the -Neale. addreaa a d initials must mitter was fitted with complete cueing facili- be Included at me above rate. Caeñ should m.o., ties manned controls of KAOG, an 8 -watt pack trans- Pony SU classified advertisements unless placed by by technicians Glenn Turner ea accredited advertising agency. No advertisement and mitter. Dave Young followed - fee ('harles Sherbourne. the ironing lee. than ten words accepted. Ten percent dis- boards with field count for six Ileum twenty percent for twelve issues. Homer Welborne and Reid Kilpatrick glasses and circled over Objectionable or misleading advertisement. nu[ - handled the mike. the Pacific Ocean as the riders held on cepted. Advert t.emrols for Demnber, 19 IQ issue to must reach u. not Esser than October 7th. They broadcast the start of the gruelling their aquaplanes with grim determination. Male-Craft 44 -mile 20 Vesey St. New York. N. Y. race from the Catalina isthmus and Pilot was Ted Brown. The ship had a followed trail- the racers, to describe aquaplane ing wire antenna and complete cueing AGENTS WANTED riders taking hard spills into the blue water facilities for the announcer. The airplane 300% PROFIT SELLING GOLD LEAF LETTERS FOR when their muscles could no longer stand served admirably More windows; Free samples. in broadcasting the 5 -lap North Metallic Company. 454 the pounding of the rough Clerk. Chicago. sea against their portion of the race between Manhattan and wooden sleds towed by i';, BOOKS AND MAGAZINES =t ilermos :a. GREATER doing radio servicednÌE jobs mro qu kly. Authentic guides chew you the way to locate and correct troubles in any radio receiver. Oernsback °metal Radio Service Manuals .how you how to complete more repair lob. In RADIO FOR DEFENSE las time -how to earn mure money by faster servicing. Read the adveri t mint width apptare on page :8;2 of this (See Editorial on page 263) 1310e. THE RADIO f- WE NAVE A FEW HUNDRED RADIO ENCYCLO- INDUSTRY P.A. Rental Business podia. by S. Oernshack. second edition. at $3.98. originally sold (1) MANUFACTURING g- Stereophonic Reproduction Rook has 312 pages, weight 3 lbs.. size 9 12 Inches. Red morocco keratol flexible binding. Send a -Radio Equipment (16) RAILROAD $3.4l1 in stamps. (including Sets, RADiO cash Cr norney order and book will be Tubes forwarded express Collect.Tr...hairax, 19I7. So. State Street. and Parts) a -Train Dispatching by Radio Chicage, Illinois._ b-P.4. Amplifiers b- -Radio Reception ( for entertainment DIATHERMY MACHINES c-Testing Equipment on trains) (I-Transmitters c DIATHERMY. SHORT-WAVE THERAPY. AND ULTRA -Radio "Barkers" on Trains ehtwt mare therapy marhi lies custom built by radio engineer g-Communication Receivers (1--Radio Communication with at ing in meters Trains 16 c meters or any freä envy specified can (2) MERCHANDISING (17) ELECTRONICS Machine. substantially built h high Patient warty factor. wit a -Mail -Order 250 -:a0u watts omput. Neat professional and Supply Companies a- Photoelectric Devices- -')'here are, appearance. Automatic safety time switches. All neces- It -- Distributors, Jobbers over 500 sary pads and electrodes. For sale only to physicians. and Retailers :applications of photo- hospitals. and sanatoriums. Prices from $195.99 In $300,1111. (6) RADiO SERVICING electric cells in commercial and Not for sale to our general piddle. WHO.. Own specification. giving you other devices and recut riment s. No literal fire avail- (4) RADiO PUBLISHING of all types able: canton ttmst Mel ban only. Allan Stuart, Teaneck. P. O. Roc 56, t'- -Elect runie Music N. .1. (5) RADiO BROADCASTING Telescope EDUCATIONAL c- Controls COURSES a -Radio Engineering d -- Photographic Aids b -Sound Effects USED CORRESPONDENCE COURSES AND SERVICE Engineers -"Lie" Detectors Bodes Bought. Sold or Rented. Catalog Free. Vernon }:s. c Transcriptions t hangr. Henag; r. Alabama. f -- Research d-- Maintenitnee Engineers t: CORRESPONDENCE COURSES g- -Insect xte rnl inatu rs . looks. AND EDUCATIONAL It Radio Talent slightly turd. Sold. Rented. Exchanged. sub Electric reefs. Rallsfatdlon All h- Fence Controllers gm rsitt eed. Cash for used I.-- - Oomplete paid .wows. Elducatiollal details and bargain catalog I TCEE. Write Nehon (18) 1tADi0 TELEME('IIANiCS Company. 500 Sherman. Ilpt. 1a -212. Chicago. g---International Shortwave a- Remote Control of Ships, INSTRUCTION h-- -Rennote Pick -ups Planes. i-- Police Radio Cars, etc. RADIO OPERATORS LICEENC tRUES. COMMERCIIAwLrs (6) TELEVISION (19) RADiO IN 3IEDI('INE 65W F Washington filed.. TO., Okla. a- Microwave Experiments a-- Shortwave Diathermy b-Radio Surgery MANUSCRIPTS WANTED b- _-Cathode-Ray Research c -Color Television c--- Radio Stethoscope WANTED -MANUSCRIPTS. POEMS, SONGS FOR d gebHcattan. }'Ortmny's. n, Fifth --Radio Diagnosis Ale.. New York. (7) FA('SIMiLE e-('aa rdioscope MISCELLANEOUS (8) RADiO ('OMMUNiC'ATiONS (20) RADIO SCHOOLS WANTED: TEST EQUIPMENT. TRANSMITTER. a- -Wired -Radio (Carrier) a--- Engineering Walter WI.unr. SI. ax F;lu.. Sunrb Intko a. b- -Radio Typewriter b- Servicing PHOTOGRAPHY c-- Trautst1(0110ir. Marine and Aviation c--Communications d- -Police Radio (/100.1)00 OF A II-Broadcasting I SECOND SPEED FLASH UNIT FOR including Talent a Strobbsroplc Photography. 32ít pu. Apt. (9) POLICE RADiO lkad 61 782 west (21) TALKIES .Are.. New York City. a -Via .Amplitude Modulation (ilome. industrial. School, b-Via Theatres) RADIO Frequency Modulation Design. (10) FiRE PATROL, RADIO a- Installation and Servicing WE BUY AND SELL USED RADIO TESTING EQUIP- FREQUEN(Y ,ant. Time payments if desired. Harold Darts. Inc., Ill) AMATEUR RADIO (22) MODULATiON Jackson. Mies. a- Shortwave and Fit rat-Shortwave ca- Transmission and Reception It- WILL SWAP ARVIN AUTOMOBILE RADIO RECEIVER. Research Police Radio rasa.. hooka eiperlmeul;il reeehers. tern era- t whorl du c- Emergency Services you wa t 12) AVIATION -for magnet le del eel or airplane -cloth speaker. RADiO Adame -Morgan oOdtsvr 'arlable condenser. loaeecoupler. naix-type a--Automatic Radio Landing Systems (23) EMERGENCY SERViCES dePorea Audios control log or whoa old apparett& have you; R. Bernard, 40 Manning 1)--Radio Compass a- -Utilities ( Electric. Gas and Water N. Ave., flannel, N. ,1. c -Radio Direction Finding (24) - -WIRED RADIO (CARRIER. HARD- TOGET RADIO DIAGRAMS. TRY USUAL d Radio Robot Pilot Systems It-- Communication s If If you y,ai: try e- --Radio Beaeons $1.50 `ne charge we don't. Vou It- -Broadcasting lees nothing! Send no money --write I- -Communication Information. first giving fullest C- Remote Control Enclose returnaddressed, stamped envelope. Facsimile We have helped many Servicemen, experimenters and g- (I- home Phono radio fans. We may help you. Allan Stuart. P.O. Box 56. ( 13) MARINE RADiO Teaneck. N. J. a--Communication (25) FORESTRY ANI) PARKS RADIO STAMPS b- Marine Radio Direction finding (28) PERSONAI. RADIO c -Radio Compass a- Jlininture Sets and Pasts THREE SCARCE SETS. NOW OBSOLETE. 25e. WITH new customer. gift: Rog 211. Malden. Mass. d- Ship's Public Address System (27) METAL LOCATORS TECHNICAL ART SERVICE e- Automatic SOS Alarm System u- l'ipclines

14) I,- 1 SOUND RF:('ORDiNG AND l'L.AY- "Treasure" bulk metal r DRAFTING AND ART SERVICE -A COMPLETE Service for the Ior llplani aladesignnge BACK (28) GEOPIiYSI( Ai. PROSPECTING If your business `afford drafting can't or. :1 -Disc IIEVit-ES star. don't let this atop you from `going ahead with that new product you Intend marketing. or tint le-Filin a- -Ore and Oil Locators Analog mechanical or electrical line e- Steel -tat pc detailedeta drawings and highlyretouched phntgrphaox. (29) INTERFERENCE SERVICING electrical radio problem (I-Transcriptions (30) TEST INSTRUMENTS Tor you by our ostaff of essnersm draftsmen and artista and 15) I'UBLiC ADDRESS technical copywriter& write for any a- Laboratory and Production nddltiunal information as to methods and price for this Inter -ONice Communication .ervlce. Ter -Art Drafting Service. 225 Charlotte Terrace, a- b- Servicing (A.M.. F.M.. Televis i. n., Roselle )'ark. N. J. h- Hearing -Aids Electronics) c -Sound Movies DRAFTING SCHEMATIC DIAGRAMS (31) PLASTICS ouch SEND US A sketch of your circuit. 1:aim:atcs by return nla il. d -P.A. Systems on Ships (32) TOOLS Jut prices are nie -b -rate: o.,r w.uI. g rato.ed. its No jra,a e Systems in big or small. Wm. Kadlei ek. .h.. (dill }::al gill, St.. -P.A. Schools, hotels, nt-- Manufacturing ': w Yost. N. Y. Night Clubs, Auditoriums. etc. (33) RADiO ADVERTISING 304 RADIO -CRAFT for NOVELISE R, I94 ;- -s ACV E TO 50% Out /hú 7frJi'/P4 ME ,v FREQU ENCY MODULATION N/P/f/ST AfsfdTELEVISION ADAPTATION RADIO FACTORY-TO -YOUmiq fAS Y TERMS

CHASSIS WITH TUBES

I AND SPEAKER

'GET THRILLING - WORLD -WIDE

FOREIGN NEWS DIRECT! appears in your local paper or is announced over your local radio. We say: You can get will out -perform ordinary sets, you news, sports broad- with the thrilling world -wide foreign Radio enthusiasts will be particularly delighted' casts and musical programs better and more brilliant performance, beautiful tone and merchandising of these clearly with a Midwest t who have seen the sensational and world-ranging ability Fifteen tubes include experts imagine being Control and 1941 Midwest Radios say that super Midwests. Just THIS Rectifier., new distant broad- Eye Tubes. they represent today's outstanding able to pull in world- Tuning a big "kick" out of casts from the capitals of Europe -to values! If you get the making before it owning a super powerful radio that hear history in 15-TUBE TRADE -IN ALLOWANCE* CABINET MODEL UP $2500 OLD RADIO ONLY TO ON YOUR *Now, you can not only save up to 50% by $2995 buying direct from the Midwest factory -but, Midwest allows you up to $25 on your old radio --on many models shown in the big, FREE Midwest Catalog. Send for this catalog and see COMPLETE for yourself that it actually brings the Midwest Just think! Here's a super factory to you, that it pictures and dramatizes powerful 15 -tube radio -com- 1941 factory -to -you radio plete in cabinet -at a price you many beautiful, pay for a 7 or to 5 wave bands would ordinarily values -from 6 to 18 tubes -up 8 -tube set. Never before have -including Automatic Record -Changing you been offered so much Radio- Phonographs, Home Recorders, etc. radio for so little money! (Model 2 -I8 MAIL TODAY OR JUST shown at left) FILL IN COUPON AND AND ADDRESS ON IC POSTCARD 18-TUBES SEND YOUR NAME 5-BANDS I Our famous 30-day prove - MIDWEST RADIOS it- yourself plan fully SINCE 1920 protects you and enables MANUFACTURERS OF QUALITY RADIOS you to prove Midwest's super performance in the privacy of your own home. Midwest Radio Corporation Absolutely no obligation. Cincinnati, Ohio, U. S. A. Name -. Dept 12 -cc MAIL COUPON Send me your new FREE Address --- .. 1 complete details of 1 FOR FREE Catalog, State your liberal 30-day Trial offer Town has ( ) lei details CATALOG and factory -to-you prices. Ufa.Apets Meks Easy Ms Mossy. Check . 30S RADIO -CRAFT for NOVEMBER, 940 LATEST RADIO APPARATUS

"UNI -VEL" MICROPHONE 10- or 12 -in. records with the lid closed. pulse -type noise (this is in contrast with The Webster Co. All audio circuits especially designed for record previously- available test equipment for this 5622 Bloomingdale Ave., Chicago, III. reproduction. Measures 11 x 1G,4 x purpose). 13' ins. deep. -Radio -Croft Specifications: 15 to 150 megacycles in 5 bands -dial HIGH -FIDELITY directly calibrated in mega- SPEAKER cycles; 1 to 100,000 microvolts measuring RCA Manufacturing Co., Inc. range across 70 -ohs, line; 1 to 100 micro- Camden, N. J. volts on semi- logarithmic output scale. Bal- anced resistance attenuator with ratios of 10, 100, and 1,000 ahead of all tubes; accurate gain standardization from internal "shot noise" diode. Special calibration dial eliminates need for charts. Tuned R.F. amplifier eliminates image response -all circuits accurately tracked. Provision for direct operation of a 5- milliampere recorder. Pushbutton switching throughout for rapid operation. Built -in dual regulated power supply for operation from either 115 V. A.C. or 6 V. D.C. Radio -Craft - I-NNE of a new line of microphones, the "Uni -Vel" velocity microphone claims SOLDERING true cardioid characteristics; wide -angle MACHINE pick -up in front and "dead" in back, "full - Electric Soldering Iron Co., Inc. range frequency response," unidirectional Deep River, Conn. characteristics, operation 30 %é closer to ATREADLE -OPERATED speakers, soldering ma- etc. Mike is housed in modern chine, model F, used where small parts streamline black and chrome case.- Radio- must be soldered Craft and particularly where it is necessary to hold the 2 parts together until the solder is applied. Feeding of "WIRELESS" AUTOMATIC solder may be exactly regulated. Solder up RECORD CHANGER to s -in. diameter may be used. The average "extended industrial AN range" loudspeaker de- soldering iron is adaptable to Galvin Mfg. Co. s gned especially this machine. Ideal for work 4545 Augusta Blvd., Chicago, for use with com- where both Ill. munications receivers. Its frequency range hands are required to hold the object being is from 60 to 5,000 cycles and its power sol dered.- Radio -Cra f t handling capacity, 10 W. Voice coil impedance is 2.3 ohms at 400 cycles.- Radio- Craft ELECTRIC ETCHER Ideal Commutator Dresser Co. NEW SELENIUM CELL Sycamore, Ill. Bradley Laboratories, Inc. New Haven, Conn.

MODEL 23RC is a "wireless" automatic record changer with a capacity of 8 10 -in. or 7 12 -in. records. The unit has an automatic "reject" button, crystal pickup, tangent tone arm, constant speed and self - starting motor, rim -drive turntable. Plays through any radio set by radiating signal. APORTABLE Plugs into the A.C. light line. No connec- electric tool for permanently marking tools, parts, dies, tion to radio receiver required. Size, 2'42 x bear- 8'á x 12 ins. -Radio -Craft ings, saws, drills and similar apparatus. Etching heats available are rated as 120, 240, 420 and 700 W. -a red indicator lamp VICTROLA burns brightly as the higher heats are turned on. Standard "Universal" RCA Manufacturing No. 13 unit Co., Inc. available for 115 -V., 60 -cycle A.C. operation. Camden, N. J. Other voltages and frequencies available upon request. -Radio -Craft

PORTABLE POWER AN entirely new t -pe of Selenium Barrier SUPPLY Layer Photoelectric Cell for use with Electronic Laboratories, Inc. light measurement and control instruments. 122 W. New York Sf., Indianapolis, Ind. A new sensitizing process it is claimed gives DESIGNED especially for use with marine these cells high current sensitivity as well transmitting and receiving equipment. as high internal impedance. The cell is avail- One section of the power supply delivers able in standard sizes or constructed to in- filament current for the transmitter and re- dividual specifications.- Radio -Craft ceiver while the other 2 sections deliver high- voltage D.C. This model S -482 "Porta - TELEVISION AND F.M. powr" is constructed for either 12, 32 or 110 NOISE V. marine application. -Radio -Craft METER Measurements Corp. CODE PRACTICE L Boonton, N. J. THE band -pass of the model 58 square "OSCILLATONE" MODEL V -100 is a combination radio - and wave signal generator is sufficiently T. R. McElroy phonograph. This instrument is one of wide for field- strength measurements of 100 Brookline Ave., Boston, Mass. a series of 14 just introduced. Receiver is frequency modulation a 5 -tube signals; wobbly radia- AN electronic instrument for reproduc- broadcast instrument with built -in tions of diathermy machines; loop antenna. The phonograph and television ing the dots and dashes of radio teleg- uses a con- signals. Permits closely determining the raphy. The oscillator stant -speed self- starting motor and plays true nuisance may be hooked up value of ignition and other for practice or plugged into a circuit for 306 RADIO -CRAFT for NOVEMBER, 1940 LATEST RADIO APPARATUS

is heavy- Switches on the front of mou ground. Type "T" switch actual receiving. type, non - regulate tone and vol- duty press -to -talk. vertical toggle the plastic cabinet also non -locking. unit operates on 115 V. A.C: I).(% locking; and "P" switch, ume. The type. Other circuits avail- and provides a choice of a 600- or 1.000 - is pushbutton -( ru ft cycle not e. Circuit includes a key -click able.- -N.ndi,d climin t.r. Irddid,_f,,drt NEW BALLAST TUBE TUBE TESTER Amperite Co. 561 Broadway, New York, N. Y. The Triplett Electrical Instrument Cc Bluffton, Ohio

LESS Time to Repair Radios ... Means MORE Time to Build Business! RCA RIDER CHANALYST

Tills model 1620 instrument feature "free reference" for all tube elements, a spare socket. 4 separate panel sections Q Q t socket, meter. roll chart, switching and powersupply)- -entirely replaceable at 00111- THE new shape and smaller size of this inns cost to prevent obsolescence due to resistor permit it to be used practically new tubes, and a new level -type switching anywhere. It puts approx. 80 V. on the which affords individual control for each receiver when first turned on- increasing of receiving Equipped with a CI et tube prong. 'ft sts all types to 110 V. at ter 4 seconds. tubes on the market. Designed for 110 -V., new fuse which automatically burns out A Kndio- Cr0)'t is connected to set having a +! 60 -cycle operation.- when ballast connection to the ballast socket. ..ral 110 -V. tie After fuse burn- out the ballast tube automatically adjusts itself to the set, keeping tube filaments between 6 to 6.6 V. with a Yesterdays servicing methods were line voltage variation of 80 to 140 V. It good enough ...for yesterday. But pro- is claimed that for A.C.-D.C. sets 4 types gressive servicemen today demand meth- of these ballast tubes will replace 90'; of ods that fix sets quicker. They spend the 1.500 types of resistor tubes now on time bending over receivers -more the market. -Kadin- ('raft time going out after business... developing business -getting ideas ... building MODULATION their business. FREQUENCY the Rider Chanalyst GENERATOR Signal- tracing with SIGNAL takes less time! The Hickok Electrical Instrument Co. in radio servicing in- Ohio Greatest advance 10514 Dupont Ave.. Cleveland, struments since servicing began, the RCA Rider Chanah st uses the newest method of attack: t/ie signal itself, common to every radio. It's an investment worth investigating! Ask your RCA Dis- tributor for on- the -circuit proof of the Chanalysi s effectiveness by means of the Dynamic Demonstrator. "Line 'em up" Faster, Easier, Better! NEW RCA A. C. TEST OSCILLATOR No.167 ... $34.50 to servicemen * New, Accurate, Las) -Reading Dial * 1(10- 30,00) KC.Funda mentals: 6 Bands *Full 1.0 Volt Maximum Output * 30%, 400 -Cycle Internal Modulation Over 380 million RCA Radio r'1'.=!Ir Tubes have been purcha sed by radio users. In tubes, as in parts and test tit equipment. it pays to go RCA All the Way. \VIDEBANII crystal- controlled signal Ageneratar. model 188X, specifically designed for F.M. but also applicable to amplitude In.'Jula,tidn0 is illustrated. Complete range: Ion kc. to 13:1 etc. Twelve output selections are available including electronic control wideband F.M. output with 750 kc. sweep for alignment over F.M. and television receivers; F.M. out- with H. 1. put, modulated internally, at 900 cycles RCA Manutacnuing Co.. Inc.. Camden. sweep of America F.C.C. standard frequency modulation A Service of the Radio Corporation (150 kc.I for surviving F.M. receivers. Also, ?p7 ER, 1940 LATEST RADIO APPARATUS

A.F. outputs of 400 cycles fixed and 50 to and 10,000 include hot inter -element short and leak- in splicing cycles variable are available; crystal - age and phone-jack adjustments. controlled tests for individual elements; also, all The old outputs, modulated and unmodu- filament voltages. bug -bear of cable extensions and lated, with accuracy Mechanical roll charts make -shift splices may now better than list test data for tubes.-Radio -Craft be totally and with frequency coverage from 100 kc. eliminated. -Radio -Cra ft to 10 mc. in 100 -kc. steps and from 1,000 kc. to 150 me. in 1- megacycle steps. Signal NEW LINE OF CABINETS MIKE CABLE TRANSFORMER generator includes a built -in power supply Insuline Corp. of America Thordarson Electric and is Mfg. Co. designed for the 110 -V. A.C. line. 30 -30 Northern Blvd., Long Island 500 W. Huron 40 to 65 cycles.-Radio -Craft City, N. Y. St., Chicago, III. AN entirely new and COMBINATION SET AND improved line of TUBE TESTER metal cabinets, Radio City Products Co., Inc. chassis, amplifier 88 Park Place, New York, N. Y. chassis, panels, etc. The r ODEL 803 M "portable cabinets are all serv- streamlined and ice shop" combine, are embellished with chrome in one instrument molding and chronic air -gate ventilators. Finish is marine the functions of gray ripple enamel.-Radio-Craft tube tester and set tester. The instrument is compact. UNIVERSAL CONNECTOR KIT measuring but 12sa Selectar Mfg. Corp. x 13 6 x ins., and 30 W. IS St., New York, N. Y. weighing but 12t. lbs. A single meter, fused against burn -out, is used for all functions. Set tester func- THIS transformer makes it very ,imple tions include ranges 0- 10/50/500/1.000 D.C. for the sound man to adapt his present voltages at 1,000 ohms /volt, and ranges for amplifiers to the new -type low- impedance A.C. and output voltages. Direct current dynamic or velocity microphones. Cable ranges are 0 -1 /10 /100 ma. /1 /10A. transformer mounts directly on the ampli- Ohm- fier and meter ranges include 0- 500 /5,000 /1 meg. 10 is available in 2 types; one is a 30 -50 megs. Decibel ranges: 8 -15, 15 -29, 29 -49 and ohm unit designed for voice -coil con- 32 -55. Self- contained battery serves for the nection of dynamic or velocity microphones Medium Ohms range and a built -in power which have self -contained line output trans- supply for the other ranges. Tube testing formers. Hum pick -up is reduced to a mini- facilities include those for all old and new mum by the use of magnetic shielding. The tubes including the transformer connects between the micro- miniature, bantam THE kit is designed to expedite servicing. junior and ballast types. The well -known Consists phone cable and a 'n ut connector. "Dynoptimum" of 10 gadgets which it is claimed -Ra circuit is utilized. Test, are will save time in making at standard R.M.A. plate voltage speaker micro- and loads, phone and chassis connections as well as JUST PUBLISHED

A NEW BOOK TO ADD TO YOUR TECHNICAL LIBRARY AUTOMOBILE RADIO - Principles & Practice by B. Baker Bryant

ACO\II'LETE eompllatlon of pertinent data on btu to install and service the modern atilt, a detailstxhlchahaverrcreptrintol the perofession been needed tl halve out. Each topic is treated so s to contain a precise statement of the fundamental principle involved, to assure the reader's Near un- dentandhng of this principle. without distracting attention his by the discussion of a multitude of details mathematical are furl the d and tend to sconfuse ratheir than rpify attreemateinst fboar Aa cticalt e s practica texperience by practical radio people for the technician. practical radio - Brief Outline of Contents - Introduction -The Auto -Radio Art. Features of the Modern Automobile Rae eiver. Installations of Automobile Radios Antenna. and The Automobile High and Low Tension A tomobile Electrical Disturbances. Vibrator Converters and Motor Generators. Service Hints, Classi lied Automobile In- stallation Notes, and Conclusion.

50c Send sue check. money order. un used l -. S. stamps. or coin for y'unr POSTPAID copy of "Antoumbllr Itadio- ITUnri pie. & Pratt ire' -it will be sent t. n you postpaid upon receipt of your Inches remittance. e4 Pea. Stiff, naible RADCRAFT Numerous illustrations PUBLICATIONS, Inc. dieoraam. 20 Vesey Street, New York, N. Y.

308 RADIO -C -nits 0011$1 ó0DFSK

WITH ANY REMINGTON PORTABLE TYPEWRITER will fit into the A beautiful desk in a neutral blue -green which made 1 Q decorations of any home -trimmed in black and silver -and ($1.00 of sturdy fibre board --is now available for only one dollar Type- extra) to purchasers of a Remington Noiseless Portable without COMBINATION writer. The desk is so light that it can be moved anywhere (600) pounds. LITTLE AS trouble -it is so strong that it will hold six hundred FOR AS Portable this combination of desk and Noiseless Deluxe With the Typewriter. you will have a miniature office at home. Learn 10' A DAY details of this offer. mlail the coupon today. of desk and complete How easy it is to pay for this combination Deluxe Noiseless Portable Typewriter! Just Remington terms as low as 10e imagine, a small good will deposit with once! You will never miss a day to get this combination at small sum can actually make you im- 10e a day. Yet this home the ossessor of this amazing office at mediately by sending the combination. You assume no obligations coupon.

LEARN TYPING FREE this To help you even further, you get free with booklet, prepared by ex. special offer a 32 -page by perts, to teach you quickly how to typewrite you buy a Noiseless the touch method. When that you get this free Remington Rand gift increases the pleasure of using your Remington Remember, the touch Noiseless Deluxe Portable. holds. typing book is sent free while this offer SPECIAL CARRYING CASE is The Remington Deluxe :Noiseless Portable easily carried about. With this light in weight, beautiful offer Remington supplies a sturdy, carrying case which rivals in beauty and utility the most attractive luggage you can buy. SPECIFICATIONS FEATURES of large stand- ALL ESSENTIAL Noiseless ard office machines appear in the 4 -row keyboard; back spacer; Rand Inc., Dept. 189.11 Portable-standard shift Remington margin étops and margin release; double 465 Washington St., Buffalo, N. Y. and shift lock; two color ribbon and auto- Free Trial of a key spacer; pa ,cr Tell me, without obligation, how to get a matic ribbon reverse; variable line Noiseless Portable, including as seven carbons; takes new Remington Deluxe fingers; makes as many and Free 32 -page Typing Instruction Book- wide; writes lines 8.2" wide. There Carrying Case paper 9.5" at- let on terms as low as 10e a day. Send Catalogue. are also extra features like the card writing tachment, black key cards and white letters, touch regulator, rubber cushioned feet. These Name make typing on a Remington Deluxe Noiseless Portable a distinct pleasure. Thousands of fam- Address ilies now using the Remington Deluxe Noiseless State Port able know from experience how wonderful City it is! LATEST RADIO APPARATUS

AUTOMATIC MINIATURE SOLDER POT Vulcan Electric Co. 10 BEST Bóßs i 0¢. 600 Broad St., Lynn, Mass. RADIO FANS EVERYWHERE fine -these amazed at the wealth of information ten cent text books give you an contained excellent foundation in these handy books. Ex- for the study of cellent for reference -ideal for every RADIO. They are clearly written, profusely technical library. YOUR MONEY BACK illustrated and contain over if you are 15,000 words not satisfied. in each book. You'll be PROMPT SHIPMENTS

No. I No. 2 HOW DOERLE SHORT WAVE TO MAKE THE MOST SETS POPULAR ALL.WAVE I and radio 2TUBE RECEIVERS bbuilt °the °famous Short Wave Radio Receivers. Sr, This book rnnti e a number of has been sets. some oe the demand excellent these receivers, a well as appeared In past iwhichssue of this RADIO-CRAFT. These is have unusually compact books has °obeenf° speciallyipecrsúyt carefully engineered. They thernstaticthermostatic con- I ished. not experiments. trol solder pot EVERYTHING these sets described measuring %-in. inside that has book, 111 the dia. and % deep. famous rece Nee Illustrations, of -in, Holds 1% ozs. of 50/50 leers hookups, etc. solder. Current consumption is 75 W. Sup- plied for use on tither AA'. or 1).C. Rudie- No. Craft 3 No. 4 ALTERNATING CURRENT ALL ABOUT FOR BEGINNERS AERIALS This book explains the theory underlying: inInvëvarious TECHNICIANS' WATCH ftden electricity the ° "Ltd°' the electitid uLooholi Doublet, Electric ircuits re explained.Ro the Double Doublet, ohms oretc. It explains noise Jules Racine 8, Lae f the funda. -free racer. Co. mental laws of radio, lon, how low.impedance Irene. pDlanned; Is . mission lines 20 W. 47 the generation of al- trans. St., New York, N. Y. ternating current: sine waves: posed ead - are Ile amperes. aa in detail (the constructionnsWctionl of vol Condensers. .rials suitable for long-wave fr . broadcast receivers. for short- and generator. wave and for llwav eners

No. 5 No. G BEGINNERS' RADIO DICTIONARY HOW TO HAVE FUN WITH Are you puzzled RADIO image? by radio Ian- stunts for Cal, you define Fro. jokes. Ponies. practical le 7;r Kilocycle? leer d,? scientific ca ter amusementssets which can he ode? Pole? Ionization? Joule'. done are law? Harmonic? In 'this fascinating Gravity Cell? um e. vol. If cannot define Ihem veer It tells how to make a tou o and domino sipaper talk -how to produce of the ore technical,trde terms lew'nt music for dances -how to ce d In all radio magazine, and make visible uric 4sow to instruction book°, you need make ilent radio" unit, Hi :ItE is a sturdy watch Look in your library. this mUsable by deafened -how of special design ake toys which dance to radie which meets needs etc..tc.. etc. of radio technicians. Servicemen may wear it in the vicinity of loudspeakers, choke coils, etc., without fear No. 7 that it will become magnetized; public ad- No. S dress HOW TO READ RADIO men can use it, for example, to check DIAGRAMS RADIO FOR BEGINNERS reverberation liuto Gernsback. periods; anti, commercial All f the scommonlymbols ally the Internatlon, sta- used ° In radio diagramsdiagram. famous radio pioneer, author tion operators and studio In editor. famous Olen, and radio this book. toggether sines NAND amateurs, tIth pictures f the apparatus and RADIO.CRAFT VISION will find it adequately accurate hey represent and lanations millions. are read by gving method to mein- 9 another triumph for split- second timing of programs prim mem. book this new Any be, and Eichberg, This by Rert with who peads it will test emissions. writer the well-known radio thorough qro get and member of the edl. theory. clearly tonal staff of RADIO -CRAFT simple explaÌed1fdin Known Magazine. also tains !mynas.. and through as the style 2301713 Multichron, dozen picture-wiring two of many illlustratiot .. radio caof n the use maim be this 17 -jewel timepiece has the following LnOd. f estht)uu mysteries of radio cle r. features: the dial is divided into 5th -seconds for timer purposes; it has regular hour and minute watch indications; circles in the No. 9 center No. IO constitute a terhomefr: gauge to SIMPLE ELECTRICAL record EXPERIMENTS TELEVISION miles- per -hour speed; and an outer Every track indicates distance- Over 100 interesting and brae. one is asking the question per -second traveled Ural electrical experiments How does television work, This by sound. described Look explains 1l of in tyeem. the different every oft ele1icpcttityY%room otfp television the simple experiments with frommost complex. One button controls the start and stop Rets to high fregu atuntas A.0 syllut of All the experiments how imagee i' scanned. a sweep- second hand; termed ae. ho,. another returns it can be crried out with television carriers up by the to simple to a ,east zero. Hairspring of Nivarox, eau be °foundLYabmostut thef home. your home. etc. l' pima and bal- of television systemss y s ance -wheel acribed. t e m s die. of Glatidur metal, reduce temperature effect; and, in conjunction with the stainless -steel case, eliminate magnetic effects. BOOKS ARE ALL UNIFORM This new model has :t black dial (an earlier. 15-jewel model, still available, has :)a to 6600ikn LIBRARY ls.has a number. Each tlatlervloolumEDUCATIONALe containsi illustrations varying from white dial ),- Radio -Craft do not think oerover Positively these honk, worth the asked. radio's greatest book price return them in iI hours and your i money will be Instenthy ref coded. QUICKLY- SERVICED SOLDERING IRON RADIO PUBLICATIONS 20 UESEY STREET NEW YORK, N. Y. Drake Electric Works, Inc. I. 3654 Lincoln Ave., Chicago, III. RADIO PUBLICATIONS, Dept, RC -ll -40 20 VESEY STREET. NEW YORK. Gentlemen: N. Y. Please send Immediately, POSTPAID, the -each hook being lot. book numbers circled below, I am melding 4 1 3 3 T s 0 IO A N t lrct tic soldering iron with an C Ran FREE NEW NEW ele- listing of 19 new IO C ment publications. that can be replaced in 30 sec - Name on,s; to remove, simply loosen a lock address -nut. Element and handle assembly are connected Cite electrically Remit by Cheek State by means of spring contacts. or money Order - ...leer latter If Inn eenA neA or umaeA V. S. raues Soldering MAIL sumpf irons from SO to $00 W. are avail- COUPON TODAY!. J able. -Rudio -Craft 310 RADIO -CRAFT for NOVEMBER, 1940 CLASSIFIED RADIO DIRECTORY

SF.1:1'IO\ II whet¢ to Euy Jet CLASSIFIED RADIO DIRECTORY Addresses, for the Entire Rodio Industry Handy Buying Guide, by Products and Manufacturers' Names and sections section per month. This method of publica- This DIRECTORY is published in -1 revisions and the DIRECTORY to be constantly up -to -date since necessary tion permits asterisk ( *) indicate that corrections can be made 'monthly. All names preceded by an names. they are trade -published If you cannot find any item or manufacturer in this section or in previously sections, just drop us a line for the information. 1940 issue. Presented here Section 1 of this DIRECTORY was published in the October, is Section II. t cannot guarantee against While every precaution is taken to insure accuracy. Radio -C raj and omissions in the preparation of this Classified the possibility of occasional errors and omissions at the Directory. Manufacturers and readers are urged to report all errors earliest moment to insure corrections in the very next issue.

LABS. INC., 55 Park Row, Ne.. MFG. CO. INC., 150 Exchange PREMIER CRYSTAL JAMES MILLEN York, N. Y,-A, BC, FS VARIABLE Malden, Mass. -AT, Mt, RT, TT CONDENSERS, St. Front & Cooper Sts., J. W. MILLER CO., 5917 S. Main St., Los Angeles, RCA MFG. CO., INC., Calif. "Miller " -AT, MT N. J., "RCA " -A, BC, FS, H Chicago Camden, Ave.. MONTGOMERY WARD & CO., 619 W. SCIENTIFIC RADIO SERVICE, 124 Jackson Ave., Chicago, III. -AT, MT, RT, TT Park, Hyattsville, Md. -A Chicago, University Mass. THE MUTER CO., 1255 S. Michigan Ave., VALPEY CRYSTALS, P.O. Box 321, Holliston, 111., "Muter " -MT -A, BC, FS, H, IF NA -ALD, Alden Products Co. CO., NC., 4014 State Line, Malden, WILCOX ELECTRIC NATIONAL COMPANY, 61 Sherman St., Kansas City, Kans. -A, tS Air trimmer AT Mass., "National " -AT, MT, RT, TT MFG. CO., 1260 Clybourn Ave., Chicago, Mica trimmer . . . MT OAK PARTS RT III. -RT DIALS 8 Receiver tuning . . . PHILCO RADIO & TELEVISION CORP., Tioga & C Transmitting tuning . TT Sta., Phila., Pa. -MT, RT, AT Transmitting (compressed-gas- RADIO CONDENSER CO., Davis St. & Copewood, Ave., Camden, N. J., "R.C.C. " -RT. AT TTC Cor. filled ) RADIO ELECTRIC SERVICE CO., INC., N. W. TT 7th & Arch Sts., Phila., Pa. -AT, MT, RT, CORP., AIRPLANE & MARINE DIRECTION FINDER RADOLEK COMPANY, 601 W. Randolph St., TT dials CD Clearfield Pe. -AT RT, Ill. MT, RT, TT Complete CO. 715 Center St., Brockton, Chicago, -AT, C ALDEN PRODUCTS Co., Inc. Crystals Mass., ""NA- Ald " -Mt, RT RCA FARADON, RCA Mfg. D & Cooper St., Decalcomanias ALLIED RADIO CORP., 833 W. Jackson Blvd., RCA MFG. CO., INC., Front DC Faradon Dial cables á cords Chicago. 111.-AT, MT, RT. TT Camden, N. J.. "RCA." * "RCA "- DL PACKAGE CO., Squire Ave., Dial lamps AMERICAN STEEL MT, RT DP Defiance, Ohio, "'Defiance " -RT Radio Condenser Co. Dial pointers INC., 900 Passaic R.C.C., AUTOMATIC WINDING CO., RELIANCE DIE & STAMPING CO., 1260 Clybourn Escutcheons E Ave., East Newark, N. J. -AT, MT III., "Reliance"-RT Pa. Ave., Chicago, Faces or scales . FS BARKER & WILLIAMSON, Ardmore, -TT SCHWARTZ & SON, 710 -712 Broadway, INC., 750 Main St., MAURICE scales (machine en- BROWNING LABORATORIES, Schenectady N. Y. -AT, MT, RT TT Feces or TT Mass. FSM Winchester, Mass. -RT F. W. SICKLES` CO., P.O. Box 920, Springfield, graved) RADIO, INC., 5205 Cedar Ave., Cleveland, BUD MT . IL -AT, Indicating lamps . Ohio, "Bud " -AT MT, RT, TT N. J., "Soler" MFG. CORP., Bayonne, . . KM ALLEN D. CARDWELL MFG. CORP., 81 Prospect SOLAR Knobs -molded . . Brooklyn, N. Y. -AT RT, TT -MT KS St Y. Knob springs CARRON MFG. CO., 415 fo. Aberdeen St., Chicago, SUN RADIO CO., 212 Fulton St., New York, N. Knobs wooden . . . KW 111.-AT MT RT -AT, MT, RT, TT - DEFIANCE American Steel Package Co. TELERADIO ENGINEERING CORP., 484 Broome Nameplates N -Jur- -AT, MT DE- JUR -AMSCO CORP., Shelton, Conn., "De St., New York, N. Y., "Teleradio" Nameplates (machine engraved) Amsco"-MT NM DE WALD RADIO MFG. CORP., 436 Lafayette St., New York, N. Y. -AT (QUARTZ) Pilotlight assem PA INC., 7421 S. Loomis CRYSTALS DOOLITTLE & FALKNOR, Rubber drives . RD Chicago, III -TT Blvd., dials & windows SS D -X RADIO PRODUCTS CO., 1575 Milwaukee Ave., Silk- screened Chicago, III. -MT FINDER CORP., Park AIRPLANE & MARINE DIRECTION ELECTRO- MOTIVE MFG. CO., INC., So. & Pa.-CD Sts., Conn., "Elmenco -MT Clearfield John Willimantic, PRODUCTS CO., 715 Center St., Brockton, 644 W. 12th St., Erie, Pa. N'tv\Vrio ALDEN RESISTOR CORP., ERIE Mass. -D, DL -MT 833 Jackson Blvd., GENERAL INSTRUMENT CORP., 829 Newark Ave., Amateur A ALLIED RADIO CORP., W. DP, E, FS, KM, Elizabeth, N. J., G.1. " -RT Blanks B Chicago. III. -CD, C, D, DL, GENERAL RADIO CO., 30 State St., Cambridge, types Broadcast BC KW, N Mass., "G -R "- Special- purpose CO., INC., P.O. Box 116 -J, GENERAL WINDING CO., 254 W. 31st St., New Frequency std FS AMERICAN EMBLEM Utica N. Y.-CD, DP, E FS, C, N York, N. Y. Gen- Win " -AT MT Holders H CORP., New Freedom, Pa. GEN -WIN, General Winding to. AMERICAN INSULATOR I.F. filter IF -KM "G.1. ", General Instrument Corp. HARDWARE CO., 476 Broad- ", General Radio Co. -control ovens TO AMERICAN RADIO "'G-R Temperature New York, N. Y., Ancco "-CD, DP E. I. INC 400 S. Peoria St., Chicago, way, ' GUTTHMAN, MFG. CO., 1265 Broadway, Neww York, 833 W. Jackson Blvd., ANGELL ALLIED RADIO CORP., N. Y. -N HAMMARLUND MFG. CO., INC., 424 W. Ill., "Knight " ARHCO, American Hardware Co. Chicago, -A N. Y. 33rd St., New York, N. Y. -AT, MT, RT, TT AMERICAN LAVA CORP., Cherokee Blvd. & Manu- AUBURN BUTTON WORKS, INC., Auburn, MFG. CO., Guelph, Ontario, Canada Rd., Chattanooga, Tenn. -H -KM HAMMOND facturers Columbus, -TT WM. W. L. BURNETT RADIO LABORATORY, 4814 D. L. AULD CO., 5th Ave. & 5th Sts., RADIO CO., 12 W. Broadway, New St., San Diego, Calif. -A, BC FS Ohio -E. N HARRISON Idaho York, N. Y. York, N. Y. -AT, MT, RT TT COLLINS RADIO CO., 2929 1st Ave., Cedar Rapids, O. AUSTIN CO., 42 Greene St., New HEINTZ & KAUFMAN, LTD., South San Francisco, BC -D, FS la. -A, Roches- Calif. -TT, TTC GALVIN MFG. CORP., 4545 Augusta Blvd., Chicago, BASTIAN BROS. CO., 1600 N. Clinton Ave., K, & Kaufman, Ltd. " ter, N. Y. -CD H Heintz Ill., "Motorola -BC Baltimore, ICA, Insuline Corp. of America HARVEY RADIO LABS.. INC., 25 Thorndike St., BENDIX RADIO CORP., 920 E. Fort Ave., INSULINE CORP. OF AMERICA 30 -30 Northern Mass., "Harvey " -A, BC Md .-C Cambridge, Ave., Detroit, Blvd., Long Island City, N. Y., "ICA "-AT, MT, HIPOWER CRYSTAL' 2035 W. Charleston St., BOND PRODUCTS CO., 13139 Hami'ton RT, TT Chicago, Ill., "Hipower " -A Mich. -CD INC., 750 Main St., E. F. JOHNSON, Waseca, Minn., "Johnson " -TT ICA, Insuline Corp. of America BROWNING LABORATORIES, LAFAYETTE RADIO CORP., 100 6th Ave., New INSULINE CORP. OF AMERICA. 30.30 Northern Winchester, Mass. -CD Blvd., Long Island City, N. Y., "ICA " -A, H BUD RADIO, INC., 5205 Cedar Ave., Cleveland, York, N. Y. -AT, MT, RT, 11' N Allied Radio Corp. Ohio, "BUD " -CD, DP, KM, 512 Market St., *KNIGHT, LAMP CORP., 811 30th St., Union City, M & H SPORTING GOODS CO., 'MOTOROLA, Galvin Mfg. Corp. CARLTON Phila., Pa. -AT, MT. RT, TT Radio Co. N. J. -DL P. R. CRYSTALS, Peterson MFG. CO., INC., 285 N. 6th St., P. R. MALLORY & CO., 3029 E. Washington CRYSTAL LABS., LibertLiberty St., CLAROSTAT INC. PRECISION N. Y St., Indianapolis, Ind., "Mallory " -MT Mass. BC Brooklyn. -KM Springfield, -A, WIRE & ASSOC. CORPS., Peoria MEISSNER MFG. CO., 7th & Belmont Sts., Mt. PIEZO SERVICE, 427 Asia St., Baton CONSOLIDATED PRECISION & Harrison Sts., Chicago. Carmel. Ill., * "Meissner " -AT, MT, RT Rouge, La. -A, BC, FS, H, TO 311 RADIO -CRAFT for NOVEMB ER, 1940 CLASSIFIED RADIO DIRECTORY

CONTINENTAL -DIAMOND FIBRE CO., N ,.., TUNG Del. -SOL LAMP WORKS, INC., Radio Tubo Div., "Dilopha -e " -FS 95 8th Ave.,Ave. Newark, N. J., Sol Photocells (oxide) . PO COTO -COIL CO., INC., 71 W;'lard Ave., urq- " -DL Ps. WOODITE, a dente R. I., Or' - -e tal Co. Remote controls . . RC "Coto-Wheel"-CD, KM P. YAXLEY, R. M r1!r, & Cc., 1- r. COTO -WHEEL Coto -Co :l Co. Robot electronic controls REC CROWE NAME PLATE & M. CO.. 3701 R. Photocell wood multipliers . . PM Ave. , Chicago, III., 'Crowe " -CD, C, E, FS, KM, N, PA ELECTRIC FENCE CONTROLLERS Power rectifiers PR DAVEN CO., 158 Summit Power S. Newark, N. J.- E supplies, vibrator . PSV HARRY DAVIES MOLDING CO., 1428 N. We. s Chicago, III. -E, KM DILOPHANE Continental D'an -c d Fibre o ADVANCE ELECTRIC 1260 C-. CO.. W. 2-d S'. I- DUAL REMOTE CONTROL CO., 31776 W. SVarre A..geles, Ca lit. --RC St. Wayne, Mich., "Donon " -E, KM ALLIED RADIO CORP., DUGON 105 833 W. Jackso, Blvd., C' Dual Remote Control Co. cago, I:1. -EL, CR, M, LS, PS, PCA, PCS, PV, HUGH H. EBY, INC., 4700 Ste -ton A. h'a. PO, RC, REC Pa. -KM Condensers AMPLIFIER CO. OF AMERICA, 37 W. 20th St.. EMPIRE n C NOTION CC.. 105 E. 2 .h St.. '. New York N. Y. --EL, CR, PS, PA, RC, REC N. Y, -KM KW THE BENWOOD -LINZE COM -ANY, 1838 Woshiegt ENAMELOIDCLOISONNE Ave., St. Ge -.Ic :u Cc- e-ROVOX CORPOPATICN N..- Louis. Mo. -PS ER4E RESISTOR Bc r,-J Mass.--C CONTINENTAL ELECTRIC CORP., E"e, Pa. -C, DP, E, CONTINENTAL ELECTRIC CO., Gcrc:a, 1:1. -P'J, KM, N CO., Go-en, i FEDERAL PO FEDERAL SALES CO., 2126 Soh JeHe-sor SALES CO. 24.26 S. J_:.,.so St-, CH- St. CHARLES JACK MEG, CORP., 27 E. Cnicego, :ego , 11. Philadelphia 1:1. -KM St., FLOCK PROCESS HARMAN ELECTR',CAL York, Pa.- 'PS. RC CORP. 17 W. 3 st St., New York MEG. CO.. Ma-sric'd, THE N. Y. -SS Ohio DAVEN CO., 158 S. -:t S., Newark, N. J. LAFAYETTE -PS .GC, General Cement Mfg. Co. RADIO CORP., '00 6th A,e., New York, N. Y. DE VRY CORPORATION, II!I '2'EMLITE CORPORATION, 79 -I3 A--:itago A.c., Ch: A c:c E.' cago, 111. LS, PS, I- ..rst, L. I., N. A. RADOLEK COMPANY, -E, PCA, PCS Y., "E-a- elci,'CIc's,.' " --r'D, C. 601 W. Rondo S'., Chi- HUGH D, FS, KM cago, Ill. H. EBY. 4700 Ste ton Ave., Phi',., Pa. -CR M, PCA, PS, RC GENERAL CEMENT MFG. CO., 1041 Kübo..n Ave., CO., 1901 Clybcur Ave., Rockford, Chicago, Ilt- ELECTRONIC CONTROL CORP., 2667 East Gra'.l III- "GC' --KM, KS. KW, DC RD Bc,:levard, THORDARSON ELECTRIC Detroit t.!'C- -CR, M, LS, PS, PCA, CENERAL ELECTRIC CO., I MEG. CO.. S . ' River Read, Scher ec- S.. Huron PCS, RC, REC tady N. Y.-C, DL. E, FS, KM, N Cnicago.11, GENERAL ELECTRONIC PRODUCTS CO., St. Charles, III. RADIO CO., 30 State Si., Cnr ordge, PCA - Mass. -CO. KM FARNSWORTH CARL GOOR PRINTING TELEVISION & RADIO CORP., 3702 CO., 26i3 N. Ash'a J Ave., E. Po -tlac St., Chicago, ELECTRIC -GENERATING Fort Wane I -d: -PM FINCH TELECOMMUNICATIONS, 'NC., 1819 GORDON SPECIALTIES CO., 1104 Broad. S. Waoas- A.. way, New York, N. Y. - -L5, PS, PCA Chicago, III. -CD, DP FS, KM, N MACHINES FISCHER SMITH INC. 162 State West L. F. GRAMMES & SONS, INC., St., Engle- 366 U -! ' St. wood, N. J. -CR, PCA RC, REC Allentown, Pa. -DP, E FS. N G -M LABORATORIES, HARRISON RADIO INC. 4326 N. K-os Ave.. CO. 12 W. Broadwa. rl.. Chicag,, III. -PCS PV Po York, N. Y. -CD, C. DL, DP, KM, N GENERAL ELECTRIC 'ICA, Insuline Corp. of A ^erica CO.. Soh,.. ectady, N. Y., INSULINE Bridgeport, Conn. -EL CORP. OF AMERICA, 30 -30 No GUARDIAN ELECTRIC Blvd., Lon MFG. CO., 1621 -27 W. Wal. Isla -d C:v, N. Y., "ICI " -DP r. ;t St., Chicoge I FS, KM --CR, RC REC KW HARRISON RADIO INSUROK, The Richarasun CO. 12 W. Broadwa :. N ^w Co. A.C. plants (gas . York, engine) ACP N. Y. -EL, CR, M, LS, PS, PCA, PCS, E. F. JOHNSON, V /aseca, PC, PO, PV, Mi, r '.,1' ' --D' Converters C RC, REC INDUSTRIAL INSTRUMENTS. KAAR ENGINEERING CO., E INC.; 156 Culver 6'9 -eso^ St., Palo D.C. generators . . . DCG AY'.. AIo, Calif. -FSM, NM !ersey City, N. J. CR PS Dynamotors D KAAR ENGINEERING H. R. KIRKLAND CO., 8.1) K'-g St., CO., 619 Emerso., St., Pa', N. J.-PAJ. -PA, IL Gas engines GE Alto, Coi . -PSV 'KNIGHT, Allied Raa'o Co'r. Vibrators LAFAYETTE RADIO CORP., 100 611, Ave., New York V N. KUPZKASCH, Y. -EL, CR, M, LS, PS. PCA, PCS, PC, RC, REC INC., 1421 S. 8,1.1., V, Da,tc, Ohio--D THE LINCROPHONE CO., INC., 1661 Howard Ave., Utica, N. Y. -PCA LAFAYETTE RADIO CORP., 100 6th Ave. New. York, ALLIED RADIO CORP., '33 W. Ja -.s 3: d., Chi. LUMENITE ELECTRIC CO 407 5. N. Y. -CD C. DL. E, KM, KW, N cage, Ill. -AC? C. DCG, D GE Y Dearbor.. St., Chicago, III. -CR, M, PCA PV. L EOTONE RADIO CO., 63 Dey S. N... York, CARTER MOTOR CO. ,628 M' -'.,. .e- A.. RC Chica- P. R. MALLORY & CO., 3029 N. Y.-CD, FS go, 111. -C, DCG D INC., E. V /ash;rg.-- S St., Indianapolis. I -d. -P5 'LIBERTY ENGRAVING & MFG. EICOR, INC., 515 S. La' -. CO., 2911 S. Ce -tral T. R. McELROY, 10) Brook!,- Ave., Los Angeles, C. DCG, D Av'., Boato-, Mass - Cali. -C, DP. E. N, FS -EL, PCA, PS, PV, 'A & H PC, PO SPORTING GOODS CO., 512 1.lorket St., ELECTRONIC CONTROL CORP., 2667 E. Gra -d MELLOPHONE CORP., 65 At o- ti = Phila., Pa. -CD .DL, KM, KW. N Blvd., Detroit, Mich, -C Ase., Rockiest -, N. Y, -EL, PS, PCA, PC. P2 MAJESTIC RADIO & TELEVISION CORP. 2600 ELECTRONIC LABORATORIES 122 W. N W. 'Nr. MILES REPRODUCER CO., INC., 812 SDth St. Chicago, 111. -CD C York St., Indianapolis, Ind.-C, V Broadway, N- .v York, N. Y.- PS PC,A RC P: R. MALLORY & CO., INC., 3029 E. Wasui -gto, FISCHER DISTRIBUTING COR' 222 F. to- St., NATIONACOMPANY,L INC., 61 Sher -a St.. M,I St.. Indianapolis, Ind., "Ya.lev " Kh+ New York, N. Y. -ACP C. DC D. GE V MANUFACTURERS -DL, der, Mass. -PS SCREW & SUPPLY HOUSE, 215 GENERAL ELECTRIC CÓ., Sc--e'ectad¡, N. Y., PHOTOBELL W. Illinois Bridgeport, CORPORATION. 123 Ube -ty St., New St., Chicago, I11. -KM Conn. -C, DOG, D York, N. Y.- CR, MEISSNER HARRISON t.1, LS, PS, PCA, PCS, PV, PO MFG. CO., 7th & Bel -o -t S's.. Mt. RADIO CO., 12 W. Broa,twa;, Nev York, RC, REC Carmel, N. Y. III., .C'Meiss- et" -CD, KM -ACP, C, DCG, D GE, V PHONOTONE LABORATORIES, JAMES MILLEN JANETTE MFG. INC., S. E. ISt- MFG. CO., INC., 150 E:.cha -.ge CO., 556 W. Monroe S.. C- icago, S., Washir gto-, Ind. -PCA St. Malden, Mass. -CD, KM; OL D' III. -ACP, C, DCG, D PHTOSWITCHO INCORPORATED, 21 Chestnut St., J. W. MILLER CO., 5917 S. Mai- St_ Los Arq r' es, KATO ENGINEERING CO., INC., 530 N. Fro' t St., Cambridge, . Markato, Mass. -CR, LS, PS. PCA, PV, RC Calif. "Mmm'..r " -CD, KM Minn. -- -ACP, C, DCG, GE RADIO ELECTRIC SERVIE CO.,. INC., N. W. MONTGOMERY WARD & CO., W. MONTGOMERY WARD S. CO., 6i9 W. Cor. 619 Chicago Chicago 7th & Arch Sts. PhiIa., Pa, -EL. CR Ave. Chicago, 111. -CD. Ave., Chicago, III. -C, D, GE C, DL, KM. N RADOLEK COMPANY, 601 W. NATIONAL COMPANY, D. W. ONAN 43 Rando.h St Ch' 61 She' -a. St., Made, &-SONS, Ro,alsc Ave., M'n. cago, 111. -EL, Mass., nefs, Mi- -ACP CR MLS. PS. PCA, PCS, RC, REC "Nation! " -CD, KM. C -. RCA MFG. CO., INC.,C 'NATIONAL PIONEER GEN -E Co' -de-, N. J. -EL, PS. UNION RADIO CORP., 57 State 5t-, -MOTOR CORP., 466 W. S..perior PCA, PCS,PCS PV, RC Newark, N. J.. ' N.atio -al St. Chicago, III. --ACP, C, DCG. D MAURICE Uric " --DL & SON 7'0712 'ARISIAN NOVELTY CO., 3510 RADIO ELECTRIC SERVICE CO., INC.. Brcadw,,. S. Wes'^- N. W. Co, Schenectady, N. Y. --EL, CR, M, LS, 111. 7th & Arch PS, PCA. PCS, Chicago, -CD. C. DP, N Sts., Ph'',,., Pa. -AC ?, C, DCG, D. PV PC, PO, RC, REC PHILCO V RADIO & TELEVISION CORP., Toga GE, S. O. & C S. CINEMA SUPPLY CORP., 636 Ilth Ave. Ss.. Phila.. Pa. -DL. KM, CD, D. DP, E. FS, RADOLEK CO., 601 W. Ra- :- - St., Ch' -ago, III. New KW York, N. Y. -EL, M, LS, PS, PCA, PCV, PO P HILMORE MPG. CO., 113 Ur iyes. PI. N. - -ACP, C, DCG, D, GE. V SUN RADIO -y Yc' CO., 212 Fol' , St., New York, Y, N. Y. -C MAURICE B 7;0. N. SCHWARTZ SON 7,7 B- adwo :. EL, CR, PCS, RC, REC PREMIER CRYSTAL LABS.. INC., 55 Park Row, Ne.: Schenectady. N. Y. -AC' D DCG., D GE, V TAY BERN EQUIPMENT CORP., 135 Liberty St. York, N. Y. -CD. F5 SUN RADIO CO., 2'7 F, . . N y Y. N. Y. New York, N. Y. -REC RADIO CITY PRODUCTS CO., INC., P9 Park Pl., -ACP, C, DCG D GEE THORDARSON New ELECTRIC MFG. CO., 500 W. York, N. Y.- -DP, KM TECHNICAL PRODUCTS INTF- '.4T,ONAL, 135 Lib- Heron St., Chicago, Ill. --PS RADIO ELECTRIC SERVICE erty St., New York. N. Y. " - CO., INC. N W. Ce. C DOG D, GE TRANSFORMER CORPORATION OF AMERICA, 7th & Arch Sts.. Pu''a. Pa, --CD, v,'INCHARGER CORP. S': _ I.- ,,,__DCG 69 C, D. DL. D'. E Wooster St. New York N. Y,- PS PCA FS, KM, KW, N WEBSTER ELECTRIC CO C'ark & D, Ksrc' RADIO KNOB CO., 43 E. Oh'', Raci -c, Ave., -KM St., Chkogo, III. Wis. -RC, RED RADOLEK COMPANY, 601 W. Ra-do!oh St., C.C' ELECTRONICS Ill. -CD, S. DL, E. FS, KM, KW, N RCA MFG. CO., INC., Ca',de" N. J C: ELECTRONIC MUSICAL INSTRU- D', E, FS. KM, KW '!YARD MFG. CO., Toledo, Ohis -DC MENTS & PARTS ', /ALTER L. SCHOTT COMPANY, 5264 W, Blvd., Los Arne' -s Ca''i. -DC 1 0/ 1 'AURICE SCHWARTZ & SON, 710 -712 Broadway, v. Schenectad., N. -CD C. D. DL. D', E, FS, KM, KW. N Exciter lamps EL S-AR MACHINE MFRS. l'IC 137' E. 81. A. Capacity relays . . CR Bro ^v, N. Y. -KM Mirrors M F. W. STEWART MEG. COP'. 347 W. Hurd- St Chicago, III., "Stewart ' -CD, C, D', E. KM PA Lens systems LS Contact mikes . - . . CM SUN RADIO CO., 212 FuHor St., New York, N. Y. Power supplies . PS Electronic chimes . . . -CD, C, D. DL DP, E. FS KM KW N EC SYRACUSE Photocell amplifiers PCA Electronic ORNAMENTAL CO., Svra. use, N. Y., piano . . . . EP "S ocowood," "Wcodite,' c Photocells . ' -E (selenium) PCS Electronic organs EO SYROCO, Syracuse 0- rame -ta' C'. Photocells (vacuum) PV Electronic piano attachment EPA SYROCOWOOD, Syracuse O-- a -e-ta Co. Photocells (chemical) , PC Electronic reed instruments ERI 312 RADIO -CRAFT for NOVEMBER, 1940 NOW READY FOR DELIVERY! to You 'receive Valuable subscrirtion RADIO= GRAFT

PLUS A FREE COPY o6 /940 )2adio- 1Qlevi3ion .NeketencQ 4nnual J TELEVISION REFERENCE ` TITH or ompliments, we want to send a copy of the 1940 RADIO- of RADIO -CRAFT magazine's special contents VV ANNUAL you FREE. if you will simply take advantage Read the summary of subscription offer NOW. This offer is being made for a limited time only. has 68 large tire B'r x Ilyz, with BOOK! The 1940 RADIO- TELEVISION REFERENCE ANNUAL pages. in this FREE never appeared before in handy book form. Its pages over 170 illustrations. The contents of this book has articles every of radio sound. public address. servicing. television. construction over practically branch wrinkles. useful circuit informa- REFERENCE for advanced radio men and technicians, time and money -saving kinks. THE 1940 RADIO -TELEVISION tion. "ham" transmitters and receivers, and a host of other data. ANNUAL contains a collection of the best and of radio as do a standard reference work for every practical branch most important articles. Covering they The Annuals have always been regarded as man wants copy 1940 edition ably sustains this reputation. Every radio nearly every branch of radio, they form a handy operation and service. This value to you. so. too, will every of this valuable book. lust as this hook will be of unquestionable you reference works. ln addition, many time and labor- warty and tested Youeverywant ethe news. saving kinks, circuits and wrinkles, tried n developments radiogsand utelevisionvalue intelligently informRADIO-CRAFT.informed u RADIO -CRAFT regularly. by practicing Servicemen, experimenters and radio fully but concisely. want it first -that is why you should read be subscriber. 'the fans have been included. This book cannot is for lust one purpose -we want you as a regular This very special offer made you you c eoAnnual. bought anywhere at any Yet It is yours by right, Rot avid, but a ropy it FREE to price. whose contents appears at the is merely suhscribing. Use the convenient coupon SAME SIZE AS beh w. RADIO -CRAFT BEGINNER'S SIMPLE INEXPENSIVE CONSTRUCTION ARTICLES Beginner's Breadboard Special - a 1-Tube High -Gain All - R'ave Reeelrer -- airing Pointers for Radio Beginners -A Watch Charm Rizo. 1 -Tube Set-Beginner's Simple Volt - Mllllammetrr- Making a 1 -Tube Iti-oudeast Loop Receiver Poser Supply for Battery Portables -A I -Tube Short-Water with Hand Coil Swathing. MORE ADVANCED SET CONSTRUCTION The "High-Seas 1" Broadcast Lamp }Islip-How to Bun.l a R -Tube I.1 -t olt Short- tt'ave Superbes for the "Ham" or Short-Wase Fan -Build the "Lunch Boa 5" Super Net - Broadcast Battery Portable-ilow to Build a Plug - Together 8 Tube Broadcast Set -The "!i-In -4" All- ts'ase Radio for A.C. Operation -.%n Easily -Built 3 -Tube Midge: Broadcast Superbeterod)ne Receiver. THE SERVICEMEN'S SECTION Base Tone Control-Simplified Variable Selectivity -Prac- tical Servicing Pointers- Srniring Universal A.C. -D.C. Re- ceivers-Killing the "Intermittent" Bug -A Service Shop A.C.-to D.C. Power Supply -Sideline Money for Service - tues-Adding A.T.C. to any Screen -Grid T.S.F. Receiver --Iron Particles In Speaker Air Gap. TEST INSTRUMENTS .k Useful Neon lawn Traer-An Inerpenslre Output Meter -Making Miilianuustsr Multipliers- Home -)lade Frequency Modulator -The Busy S siretuen's V.T. Volt- Meter. PUBLIC ADDRESS AND AMPLIFIERS Build this Combination A.C. -D.C. Radio and Inter-Com- municator-Speaker Placement in P.A. Work-The Dalgn and Construction of an Inexpensive All -Push -Pull 10 -Watt Amplifier- Obscure Sources of Hum In High -Gain Ampli - tiers -Row to Build a High - Fidelity 5 -Watt Versatile Amplifier. 11HAM" SECTION Ultra-High Frequency Antennae -The Beginner's Low -Cat emitter- Modulator Meter -Phone Monitor -The Begin - "11am" Receiver -g!fi Meter Acorn Transceiver. TELEVISION lies to Bull.l a 441 I.pe T.A.F. Television Receiver -Cn- fal Noves u 'tels islnn Antennas. MISCELLANEOUS mpin l'hoto.Cell Relay Set Up- Making Burglar Alari-How to Build A.C. -D.C. Capacity Relay -How to Make a Modern Radio Treasure Locator. USEFUL KINKS, CIRCUITS AND WRINKLES Making a Flexible Coupler-Two -Timing Chime -A Simple Portable Aerial -An Improvised Non-Slip Strew-Driver. s oTI-:: The book contains numerous other useful Minn. Circuits and Wrinkles. not. listed here. (approximately) 45 ARTICLES (approximately) 170 ILLUSTRATIONS BRINGS YOU THE ANNUAL THIS COUPON 68 BIG PAGES RADIO -CRAFT 20 VESEY STREET NEW YORK, N. Y. Gent]ea., n: Enrio=eti you will find One Dollar for which enter my subscription to RADIO-CRAFT Magazine for Eight Months. Send me ABSOLUTELY FREE and POSTPAID, my copy of 1940 RADIO-TELEVISION REFERENCE ANNUAL. Thia is a new order D Extend My Present Subscription RADIO -CRAFT NAME ADDRESS 20 VESEY STREET CITY STATE NEW YORK, N. Y. DON'T DELAY - MAIL. TODAY! RC -1140 RADIO -CRAFT for NOVEMBER, 1940 313 CLASSIFIED RADIO DIRECTORY

Electronic string instruments L. S. BRACH MFG. CORP., ESI 55 Dickerson St., Washers, fiber Harmonies H Newark, N. J. -AR AT . . . . FW BROWNING LABORATORIES, INC., 750 Main St., Washers, lock . . . WL Pedal volume controls . PVC Winchester, Mass.-AA, C, D, R Grille cloth GRC Musical amplifiers . . . MA THE CLOUGH -BRENGLE CO., 5501 Broadway, Chi. capo, III. -FSG Coil dope CD ALLIED RADIO CORP., 833 W. Jackso- Blvd., DELTA RADIO CORP., 115 Worth St., New York, Fuses & Mountings FM Chicago N. Y.-C 111.-CM, EO, EP, ERI, ESI, H, PVC Engraving & Bakelite AMPERITÉ ESPEY MFG. Panels EBP COMPANY, 561 Broadway, New York, CO., INC., 350 E. 63rd St., New York, Bakelite N. Y.-CM PVC N. Y.-AA, CA, CR R sheet tubes & rods BSTR ANSLEY RAISIO CORP., 4377 Bronx Brvd., New FARNSWORTH TELEVISION & RADIO CORP 3702 Rubber bumper feet . . RBF York, N. Y. -EP E. Pontiac St., Fort Wayne, Ind. CA, R, T Spring Washers . . . . SW THE BRUSH DEVELOPMENT CO., 3311 Pcrki -s Ave., M. M. FLERON & SON, INC., 113 N. Broad St., Cleveland, 0.-CM Trenton, N. J. -AR Push on knob spring . . PKS CHARLES JACK MFG. CORP., 27 East Philadelphia GENERAL ELECTRIC CO., Schenectady, N. Y. Special washers . . . SPW Bridgeport, & St., York. Pa. -EO Conn.-AT, AA, CA, CR, R, T Miscellaneous screws, washers, CRACRAFT, INC., 28 Grove St., New York, N. Y. E. 1. GUTHMAN & CO., INC., 400 S. Peoria St., -CM, EP, ESI, PVC Chicago, 111.0 etc. MISC ELECTRONIC SOUND & MUSIC CO., 10 Sruyvesant HALLICRAFTERS, 2611 Indiana Ave., Chicago, III, St., New York, N. Y. -CM, EO, -CA, R EP, ERI. ESI, ALDEN PRODUCTS CO., 715 Center St., Brockton, H, PVC D. H. HARRELL, 1527 E. 74th Place, Chicago, III. Mass. -BP, C, P. SKT, SL, T, CD, J ELECTRO -VOICE MFG. CO., INC. 1239 -AR, AT South Be ^d ALLIED RADIO CORP., 833 W. Jackson Blvd., Chi. Ave., South Bend, Ind.-CM, PVC HARRISON RADIO CO., 12 W. Broadway, New cago, 111. -BP, CD CS, C, GC, G, J, MB, P, EVER -NU PRODUCTS, 919 N. York, N. Y. -AR AA, C, DA, DR. D R Latrobe Ave., Chicago, T SKT SL, TS, T, MISC 111.-CM HARVEY WELLS COMMUNICATIONS, INC., Box AMERICANEMBLEM CO., INC., Box 116 -J, Utica, FISCHER DISTRIBUTING CORP., 222 Fulton St., 100, Southbridge, Mass. -R, T THE N. Y.-G, MB, SKT New York, N. Y. -CM HICKOK ELECTRICAL INSTRUMENTS CO., AMERICAN HAMMOND 10514 Dupont Ave., PHENOLIC CORP. 1250 Van Buren INSTRUMENT CO., 2915 Non^ W^-st- Cleveland, Ohio-Test Appara- St. Chicago, ern Ave., Chicago, III. tus (see Test Eouipment) III., ' Amphenol "-C, GC, G, P. -EO ("Ham -ond" organ), T, CD EP ("Novachord ") EPA ( "Solovoe' E. F. JOHNSON CO., Waseca, Minn. -AR, AT AMERICAN RADIO HARDWARE 476 - HARRISON RADIO 12 LAFAYETTE RADIO CORP., 100 CO., Broad CO., W. Broadway, New 6th Ave., New ay, New York, N. Y., York N. Y.-CM, PVC York, N. Y. -AR, AA "Ancco " -BP, C, CS, GC, G, MB, P, S, SKT, SL, T, TS, WF, WL LAFAYETTE RADIO CORP., 100 6th Ave., New JOHN E. LINGE & SON, INC., 28th St. & Buren AMPHENOL, American - York, N. Y.-CM, PVC Ave., Camden, N. J. Phenolic Corp. ARHCO American Rado Hardware Co. LEOTONE RADIO CO., 63 Dey St., New York, N. FRED M. LINK, 125 W. 17th St., New York, N. Y. -CM Y. -PEU ATLAS SOUND CORP., 1447 -39th St., Brooklyn, N. Y.-C, GC, P MONTGOMERY WARD & CO., 619 W. Chicago MAJESTIC RADIO & TELEVISION CORP., 2600 W. 50th AUDIO DEVELOPMENT CO., 123 Bryant Ave., North, Ave., Chicago, 111.-CM, PVC St., Chicago, III -C, CA, CR, R Minneapolis, Minn. -J, P NATIONAL DOBRO CORP., 400 S. MARINE RADIO CORP., 117 -19 168th St., Jamaica, Peoria St., BANK'S MFG. CO., 5019 N. Winthrop Ave., Chi- Chicago, 111 -ESI, PVC N. Y.-R, T cago 111. -BP, C, RADIO ELECTRIC SERVICE MEISSNER MFG. CO., Mt. CS, GC, G, MB, P, S, SKT, CO., INC., N. W. Cor. Carmel, 111.-AA, C, SL, 1' TS, WF, WL 7th & Arch St. Phila. Pa. PVC CA CR, D, R -CM, BELDEÑ MFG. CO., 4647 W. Van Buren RADOLEK COMPANY, 601 W. Randolph JAMES MILLEN MFG. CO., 150 Exchange St., St., Chi. St., Mal. Chicago, 111. -SL cago 111.-CM, EO, EP, ERI, ESI, H, PVC den, Mass. -C, R, T MIMS BIRNBACH RADIO CO., INC., 146 Hudson St., RCA MFG. CO., INC., Camden, N. J. -EP ('Story. RADIO CO., P.O. Box 504, Texarkana, Ark. New York, -AR, AT N. Y. -BP, CP, FS, P, S, SKT, SL, T. tone' ERI WF, WL ROWE INDUSTRIES) INC., 3120 Morroe NATIONAL COMPANY, INC., 61 Sherman St., Toledo, St., BOND PRODUCTS CO., 13139 Hamilton Ave., Ohio-CM, ESI, PVC Malden, Mass. -C, CA, CR, D, R MAURICE PACENT ENGINEERING Detroit, Mich.-C, CS, P, SKT, SL, T, TS, BP, G. SCHWARTZ & SON, 710.712 Broadway. CORP., 79 Madison Ave., J, MB, MISC Schenectady, N. Y. New York, N. Y. -AR, -CM, EO, EP, ERI, E51, H, CR, R BRANDYWINE FIBRE PRODUCTS PVC RADER CORP., 1733 MiIvaukee Ave., CO., 14th & Wal- Chicago, Ill. nut Sts., Wilmington, Del. -G, WF MARK SIMPSON DIST. CO., INC., 16 Hudson -AR, C St.. THE BRUSH DEVELOPMENT CO., 3311 New York, N. Y. -CM, PVC RADIO ELECTRIC SERVICE CO., Perkins Ave., INC., N. W. Cor. Cleveland Ohio -P, SKT SUNDT ENGINEERING CO., 4745 Ravenswood 7th & Arch Sts., Phila., Pa. -AR, AT, Ave., AA, C, CA, BUD RADIO, INC. 5205 Cedar Ave., Chicago, 111. -EC CR, D, R, T Cleveland, SUN RADIO RADIO ENGINEERING Ohio, "bud " -CS, G, MB, P, SKT, SL, T, TS, CO., 212 Fulton St., New York, N. Y. LABS., INC., 35.54 36th St., J, C MISC PVC Long Island City, N. Y. CM, -AT, R, T CANNON ELECTRIC DEVELOPMENT TRANSFORMER CORPORATION RCA MFG. CO., INC., Camden, N. CO., 420 W. OF AMEP'CA, 69 J. -AR, AT, Ave. 33, Los Angeles, Calif.-ft SKT Wooster St., New York, N. Y. MA CR R, T -CM, CARRON MANUFACTURING 415 THE VEGA CO., 155 RADOLEK COMPANY, 601 W. CO., S. Aber- Columbus Ave., - Randolph Bos' Mass. St., Chi - deen St., Chicago 111.CD, CS, GC -ESI, PVC cago, III. -AR, AA C, CA, CR, D, R CINCH MFG. CORP., 2335 W. Van Buren MAURICE SCHWARTZ& SON, 710-712 St., Broadway, Chicago, III., " -BP, P, Schenectary, N. Y. -AR, AT, "Cinch SKT, SL, C, G, AA, C, CA. CR, J, MB, T TS, MISC, D, R. T GC, SP FREQUENCY CINEMA ENGINEERING CO., 1508 S. Verdugo MODULATION SUN RADIO CO., 212 Fulton St., New York, N. Y. Ave., Burbar.k, Calif., "Cinema " T, J -AR, AT, AA, C, CA, CR. D, R, T -P EQUIPMENT TECHNICAL PRODUCTS CONTINENTA L DIAMOND FIBRE CO., Newark, INTERNATIONAL, 135 Del. -G, SKT, WF Liberty St. New York, N. Y. -T CONSOLIDATED WIRE & ASSOCIATED CORPS., TELERADIO ENG. CORP., 484 -90 Broome St., New York, N. Y.-C 512 5. Peoria St. Chicago, 111.-CD, J CRESCENT TOOL & DIE CO., 4140 TILTON ELECTRIC CORP., IS Belmont Ave., E. 26th St., New Chicago, 111,, York, N. Y.-AR "Crescert " -MB, T, WF CRUMPACKER DIST. CORP. 1801 Fannin UNITED STATES TELEVISION MFG. CORP., St., 220 Houston, Tex. CS, C, GC, lam`, J, MB, P, E. SIst St., New York, N. Y. -R SKT, SL, VERTI FLEX ILLINOIS T, TS, MISC SEATING CO., 2138 N. DAVEN COMPANY, 158 Antennas . Summit St., Newark, N. J. (receiving) AR Racine -Ave., Chicago. 111.-AR WARD PRODUCTS -BP Antennas (transmitting) . AT CORP., 1523 E. 45th St., Cleve- land, Ohio -AR DUAL REMOTE CONTROL CO., 31776 W. Warren Add -on adapters . . . St. Wayne, Mich., " AA Vy!NCI- tAeGER CORPORATION Stour "Decos -P Coils C -AP A' C'y, Iowa DUGON--Dual Remote Control Co. EAGLE Combination A.M. -F.M. ELECTRIC MFG. CO., INC., 59 Hall St., adapters Brooklyn, N. Y, -SKT, C, P, T CA HARDWARE- CONNECTORS EASTERN MIKE -STAND CO., 56 Christopher Ave., Combination A.M. -F.M. receivers Brooklyn, N. Y.-P AND MISC. PARTS EDWIN 1. GUTHMAN & CO., INC., 400 S. Peoria CR St.. Chicago, III. -T Dials D HUGH H. EBY, INC., 4700 Stenton Ave., Phila., Pa. BP, P, SKT, T, Receivers R - J ECCO HIGH FREQUENCY CORP., 120 W. 20th St., Transmitters T New York, N. Y.-P Test apparatus (see Test Equip- k 4 41 GEORGE D. ELLIS & SONS, INC., 309 N. 3rd St., ment) Phila., Pa. -CS, TS EMPIRE NOTION CO.. 105 E. 29th St., New York, F.M. amplifiers (audio) FMA N.Y. Binding posts BP -BP, G, MB, SKT, MISC Police, emergency services, utility ERIE CAN CO., 816 Erie St., Chicago, III., "Erie" Cable connectors . . C -CS, TS PEU Coil shields EX STAT- Tilton F.M. Signal generators CS Electric Corp. FSG Coupling CP FAHNESTOCK ELECTRIC CO., 46.44 Ilth St., Long Lead -ins LI Island City, N. Y.-BP, C, J, SL, T Flex. control shafts . FS Cable CA FEDERAL SALES CO., 26 S. Jefferson St., Chicago, Grid clips GC 111.-G, MB, SL, T, J, P, SKT, MISC FISCHER DISTRIBUTING CORP., 222 Fulton ALLIED RADIO CORP., B33 W. Jackson Blvd., Chi- Grommets G St., New York, N. Y. -BP, CD, CS, C, GC, G. J, MB. cago, III. -AR, AT, AA, C, CA, D, T, R Jacks CR, J P, SKT, SL, TS, T. ALPHA WIRE 50 MISC CORP., Howard St., New York. Mounting . N. Y. -CA brackets MB G C- GENERAL CEMENT MFG., CO. GENERAL CEMENT MFG. CO. 1041 Kilburn Ave., AMERICAN COMMUNICATIONS CORP., 123 Plugs P Lib- Rockford, 111.-CD. G SKT, MISC erty St., New York, N. Y.-AR AT, T Rivets R AMERICAN EMBLEM GENERAL ELECTRIC CO,, Schenectady, N. Y.- CO., INC., P.O. Box 116, Screws S SKT, TS Utica, N. Y. GENERAL ELECTRIC 1285 AMERICAN PHENOLIC Self -tapping screws . SS CO., Boston Ave., Bridge - CORP., 1250 Van Buren port, Conn., "GE " -P St., Chicago 111. -LI Sockets SKT GENERAL RADIO CO., 30 State St., Cambridge, AMPLIFIER Cb. OF AMERICA, 37 W. 20th St., New York, Soldering lugs SL Mass. -BP, SKT N. Y. -FMA GENERAL ANSLEY RADIO CORP., 4377 Springs SP WINDING CO., 254 W. 31st St., New Bronx Blvd., New York N. Y. "Gen- Win " -BP York, N. Y.-CR Spring clips SC MFG. CO., 4647 GEN -WIN- General Winding Co. W. Van Buren St., Chi- Terminal GOAT RADIO TUBE PARTS, cago, 111. -AR AT strips T INC., 314 Dean St., Brooklyn, N. Y., "Goat Form -Fitting " -GC, TS BOND PRODUCTS CO., 13139 Hamilton Ave., Tube shields . . . . TS SL, Detroit, Mich. -R GORDON SPECIALTIES CO., 1104 S. Wabash Ave., Washers, felt . . . . WF Chicago, 111. -G. RBF 314 RADIO -CRAFT for NOVEMBER, 1940 Order your copy NOW the only 1st Edition Almost Gone! ORDER TODAY

P. A. HAND B 00K A Resume of the Contents of the AMPLIFIER HANDBOOK AND PUBLIC ADDRESS GUIDE FOREWORD INTRODUCTION Definitions -decibels, frequency, in- output, etc. n' EC TI ON OURCEce, Carbon microphones (single-button and double- button) Condenser microphones Velocity (ribbon) microphones Dynamic microphones Crystal microphones (sound -cell types, crystal diaphragm types) Cardioid microphones Contact microphones Phonograph pickups (magnetic types, crystal types) SECTION It- AMPLIFIERS Voltage Amplification Design of resistance -coupled voltage amplifiers Commercial voltage amplifier The Power Stage Class A amplifiers Class AB amplifiers Class AB: amplifiers Class AB, amplifiers Class B amplifiers When to apply class A, AB, and B amplification Power Supplies Half -wave rectification Full -wave rectification Voltage doublers Filter Circuits Power supply regulation, etc. Practical Hints on Amplifier Con- struction Microphonism Placement of components Tone compensation Inverse feedback Remote control methods SECTION III -DISTRIBUTION The Loudspeaker Dynamic speakers Speaker performance (frequency response, efficiency) High -fidelity speakers Speaker Baffles and Housings Outdoor speaker installations Power cone speakers MOST COMPLETE Radial (360° distribution) speaker AND AUTHENTIC baffles SECTION IV- COORDIN.ITIOX P.A. BOOK PUBLISHED Input impedance matching to P.A. installa- MATCHLESS VOLUME Matching speakers roA't no book s let bean published hick ers A amplifiers andcompleta systems (also d As complete as you unuld expect to find any engineer- tions tnbelievable.in h ntic volume i. lmoost ing handbook -this is how the din P. A. speakers Yet. it le fart. there Is book in finds the AMPLIFIER MAMDSOOK ANDrPUBLIC AD. Phasing '''1tint which Covers Public Address from A to E. DRESS GUIDE. With essential technical( data rcompiled Effect of mismatching speakers to bridge this wide.spread gap. lO.CRAFT will exceptionally Magnificent e' nearlyn hundrtel different subjects amplifier output publish volumes or aub.division na o/ magnitudfl completee aneañut rda iita -- coordinating ceivable branch P.A. installation (in a IN-Dat every man in radio have both of Public Address". A typical a theoretical pSactical knowledge ofthe function THE CONTENTS sound systems. The editorial re. skating rink) and operation of µ show the opt and magnitude of the th To tuallr PUBLIC ADDRESS SECTION V- USEFU1. PUBLIC he t volume fullyld Justifies Itstitle AMI'l.t FtF:Ít IIANDDOOKC AND the lstralInnstatu lleht vuÓ stis AD. huIDE. an analysts of the is fnund at ADDRESS DATA AND IN- LIFICO MAMDEOOK AND PUBLIC the breakdownc. of the material featured OASES.5 1*4 GUIDE. great HAl'DSOOKtlon Put,),e Ad- right. shnsotng thorough of ATTON dress should bee read within,, book. FORM e t i ceornoleeess f this . n....t 11.n. .ss t . 'cttl tientls 1,lit. n i, .'_ d ..II sound ,.,,rn Is l,,ua Speaker matching technique The ABC of Db., VU, Mu. Gm and RADCRAFT PUBLICATIONS 20 VESEY STREET NEW YORK, N.Y. Sm to the MO SIMI - Charts and forntulbs useful I------practical P.A. sound man RC -1140 Handy index to important articles RADCRAFT PUBLICATIONS. INC. * 20 VESEY STREET * NEW YORK. N. Y. NF.w- on public address and sound llanos En, heed find my remittance of 23c for which tend ms POSTPAID. one MY of your I 1940 AMPLIFIER HANDBOOK AND PUBLIC ADDRESS GUIDE.

Find me others. for friends. also POSTPAID MI 2;c each. I Order Your Copy NOW- I Name Address 1 State fits 1 gip &upon and Remit by check money nrdrr: e Pottage St .hits if you send cash or unused l' r giltetr mail Today! !_ J RADIO -CRAFT for NOVEMBER. 1940 31S CLASSIFIED RADIO DIRECTORY

L. F. GRAMMES & SONS, INC., 364 Union St., SYNIHANE CORPORATION, Highland Ave., Oaks, MAURICE SCHWARTZ & SON, 710.712 Allentown, Pa. -SL T Pa. -SKT T Broadway, HEGELER Schenectady New York -C, D, HA, HABC, ZINC CO., P.O. Box 599, Danville, III. - 'TEFFT RADIO CO., Plymouth Mich. M CS, TS -S SUN RADIO CO., 212 Fulton St., New York, N. Y.- TELERADIO ENGINEERING CORP., 484 Broome St., C, D, M HARRISON RADIO CO. 12 W. Broao.ey, New New York, N. Y., "Teleradio "-C, MB, T, CD, CS, TRIMM RADIO MFG. 1770 York N. Y. -BP, CD, dS, C, G, F, MB, P. SKT, SKT SL CO., W. Berteau Ave., SL, TS, T, MISC Chicago, III., "Trimm " -HA, M TILTON ELECTRIC CORP., 15 E. 26th St., New York, UNIVERSAL MICROPHONE HAMMARLUND MANUFACTURING CO., INC., N. Y. CO., Inglewood, Calif. "Ex- Stat " -T -C, D 424 W. 33rd St., New York, N. Y.-CS, TS THE TRIPLETT ELECTRICAL INSTRUMENT CO., WESTERN ELEC. CO., 300 Central Ave., Kearny, A. G. HINTZE, 300 W. Adams St., Chicago, III. Bluffton, Ohio -BP, J -GRC N. J. -HA M, D UNITED RADIO MFG. CO. 191 Greenwich St., WESTERN SOUND HERBERT H. HORN 1201 S. Olive St., & ELECTRIC LABS, INC., 311 W. Los A ^geles, New York, N. Y. -E8P BSTR Kilbourn Ave., Milwaukee, Calif. -BP CD, dS, C, P, Wis. -HA GC, G, J, MB, SKT, RADIO PRODUCTS CO., 820 Orleans St., ZENITH SL, T, TS, MISC UTAH RADIO CORP., 6001 Dickens Ave., Chicago, Chicago, III. -GC, P, TS I11.-HA HUNTER PRESSED STEEL CO., Lansdale, Pa. -SP S. S. WHITE DENTAL MFG. CO., 10 E. 40th St., ICA- Insuline Corp. of America New York, N. Y.--FS, CP IDEAL COMMUTATOR DRESSER CO., S,ca' -re, WILCOX ELECTRIC CO., INC., 4014 State Line, III. -SL Ka-sas Cry, Kars. HEARING INDUSTRIAL -T5 AIDS SCREW & SUPPLY CO., 1439 N. Wells WILMINGTON FIBER SPECIALTY CO., Wilrnirgton, St. Chicago, III. -BP, G, MB, S. SL, WF, WL Del.-WF INSULATING FABRICATORS, INC., 12 E. 12r- St., X.L RADIO LABORATORIES, 420 New York, N. Y. -BSTR West Chicago Ave., Chicago, 111.-BP INSULINE CORP. OF AMERICA, 30.30 Not -em YAXLEY -P. R. MALLORY & CO., INC. Blvd. Lon Island City, N. Y., "ICA " -BP, C, ZEIRICK MFG. CORP., 385 Gerard Ave., New York, CS , C MB, P, SKT, SL, T, TS, CD. MISC, J N. Y. -C, GC, MB, SL, SC, T J. F. D. MANUFACTURING CO., 4111 Fo Hamil- ton Pkwy., Brooklyn, N. Y.-CD, C, TS, MISC Complete (desk E. F. JOHNSON, Waseca, Minn., "Jo- -s:- " -P, type) CDT SKT SL, J HEADPHONES Complete (portable, personal) HOWARD B. JONES, 2300 Wabansia Ave. C'..-.ago, CPP III., "Howard B. Jones" -C, P. S, SKT S - Wearable vacuum -tube aids LAFAYETTE RADIO CORP., 100 6th Ave., Ne, W York N. Y. -BP, CD, CS, C, GC, G, J, MB, P. SKT, Ladies' comb. vanity . . LCV SL T TS, MISC LITTELEUSE, INCORPORATED, 4745 Rave -sood ALLIED RADIO CORP., 833 W. Ave., Jackson Blvd., Chi- Chicago, 111.-FM Q?st-0 cago, 111.-CDT, CPP LEOTONE RADIO CO., 63 Dey St., New Yo%, AMPLIFIER CO. OF AMERICA, 17 West N. Y. -MB 20th St., -'a:-. Crystal C New York, N. Y.-CPP M. 6 G. HEARING N. = AIDS CO., 30 l' Dynamic D AUDIO DEVELOPMENT CO., 23 Bryant Ave. N., Avenue, Chicago, III. -P. SKI . Minneapolis, Minn.-CPP, GEC M & H Hearing -aid SPORTING GOODS CO., 512 Ma e St., HA AUDIOGRAPH SOUND SYTEMS, 1313 W. Randolph Phila. Pe. -BP, CS, CD, C, GRC, G, J, MB, P, Magnetic M St. Chicago, 111.-CDT SKT, SL, T, TS, MISC Hearing -aid (bone conductor) CRYSTAL EAR, INC., 2007 S. Michigan Ave., Chi. MAJESTIC RADIO & TELEVISION CORP., 2600 W. cago, 111.-CDT, CPP 50th St. Chicago, 111. -MB HABC ELECTRONIC SOUND & MUSIC CO., 10 Stuyvesant P. R. MALLORY & CO., INC., 3029 E. Washi -gor St., New York, N. Y.-CPP St. Indianapolis, Ind., "Yexley " -C, G, MB, P, ALLIED BURNS CO., 1008 Madison Ave., Toledo, ERWOOD SOUND EQUIPMENT CO., 224 W. Huron C, J Ohio-HA St.. Chicago, 111. -CDT MANUFACTURERS & SUPPLY HOUSE, 215 ALLIED RADIO CORP., 833 W. Jackson Blvd., Chi. ESPEY MFG. COMPANY INC., 305 East 63d Street, W. Illinois St., Chicago, Ill. -BP, G, S. SL, WF, cago, III., "Knight " New York, N. Y.-CDT WL -M, C, D, HA, HABC AMPLIFIER CO. OF AMERICA, 17 W. 20th St., New EXECUTONE INC., 415 Lexington Ave., New York, MEISSNER MFG. CO., INC., 7th & Bel -o -t Sts., York, N. Y. -HA N. Y. -- CDT Mt. Carmel III., ''Meissner" -SKT AUDIO DEVELOPMENT CO., 123 Bryant Ave., GLOBE PHONE MFG. CORP., Reading, Mass. - MICARTA FABRICATORS, INC., 4619 Ravenswood North Minneapolis, Minn,-HA CDT, CPP Ave., Chicago, III. -GC, SKT T WF AUDIOGRAPH, John Meck Industries CHARLES JACK MFG. CORP., 27 East Philadelphia JAMES MILLEN MFG. CO. INC., I50 Exc -a -qe St., BRUSH DEVELOPMENT CO., 3311 Perkins St., York, Pa. -CDT Malden, Mass. Ave., -BP, C, CS, SKT, T, CD, T5 Cleveland, Ohio-C, HA LAUREHK RADIO MFG. CO., 3918 Monroe Ave., J. W. MILLER CO., 5917 S. Main St., Los Angeles, C. F. CANNON Wayne, Mich. -CDT, Calif., Miller " -BP, CO., Springwater, N. Y.-M CPP CS, MB, SKT, T, TS CARRIER MICROPHONE CO., 439 S. La M & G HEARING AIDS COMPANY, 30 N. MONTGOMERY WARD Bree Ave., Mich- & CO., 619 W. Chicago Inglewood, Calif., "Carrier " igan Ave., Chicago, 111. -CDT, CPP W Ave. Chicago, III. -BP, -D CD, C, G, J, MB, P. SKT, CARRON MFG. CO., 415 S. Aberdeen St., Chicago, MAJESTIC RADIO & TELEVISION CORP., 2600 W. SL T, TS MISC CS III -"Carron " -M HA 50th St., Chicago, III. -CDT, CPP MUELLER ELEC. CO., 1583 E. 31st St., Clevela -d, CHICAGO TELEPHONE SUPPLY CO., 1142 W. MILES REPRODUCER CO., NC., 812 Broadway, Ohio, "Mueller Universal Ceps " -C Beardsley Ave., Elkhart, Ind., " New York, N. Y. -CDT, ¿PP MUTER COMPANY, "Frost -M 1255 S. Michigan Ave., Chicago, CONNECTICUT TEL. & ELEC. CO., 70 Britannia St., MONTGOMERY WARD & CO., 619 W. Chicago III., 'Muter' -SL Meriden, Conn.-C, M Ave., Chicago, III. -CDT CPP NASH RADIO PRODUCTS CO.. 6267 Gravois Ave., CRUMPACKER DIST. CORP., 1801 Fannin St., Hous- E. A. MYERS & SONS. 306 Beverly Rd., Mt. Lebanon, St. Louis, Mo. -GC, P, SL, WF ton, Tex. M Pittsburgh, Pa. -CDT, CPP NATIONAL -C, COMPANY, 61 Sherman St., Malden, DE VRY CORPORATION, 1111 PARAPHONE HEARING AID, INC., 4300 Mass, Armitage Ave., Chi - Euclid -CS, SKT, TS, BP, CD, J, MB, P, SL, T, cago, 111.-HA Ave., Cleveland, Ohio -CDT, CPP MISC RADOLEK ELECTRICAL INDUSTRIES MFG. CO., Red Bank, COMPANY, 601 W. Randolph St., Chi - NATIONAL VULCANIZED FIBRE CO., Wilr.l -go', N. J. -M cago, 111. -CDT, CPP Del. -WF FISCHER DISTRIBUTING CORP., 222 Fulton St., ROTOPHONE CORPORATION, 26 Journal Square, NEW ART SPECIALTIES, INC., 816 W. Erie St., New York, N. Y.-C, Jersey City N. J. -CDT, Chicago, D, HA, HABC, M CPP, LCV III. -MB, SL, MISC, SPW, PKS SW FROST, Chicago Telephone Supply Co. SHURE BROTHERS, 225 W. Huron St., Chicago, III. A. OLEK, 4759 Melrose St., Phila., Pa. -GC GLOBE PHONE MFG. CORP., -M PARKER -KALON Reading, Mass. - CORP., 200 Varick St., New York, HA, HABC, M TAY BERN EQUIPMENT CORP., 135 Liberty N. Y.-SS St., HARRISON RADIO CO., 12 West N. Y. -CPP PAUL 8 BEEKMAN, Broadway, New 4250 Wissahickon Ave., Phila., York, N. Y,_.C, D, HA, M HABC TELEX PRODUCTS CO., Minneapolis, Minn.-CDT, Pe.-05 TS, MB, MISC HERBERT HORN, 1201 S. CPP PHILCO H. Olive St., Los Angeles, RADIO & TELEVISION CORP Tioga & C Ca Hf .-M TRANSFORMER CORP. OF AMERICA, 69 Wooster Sts., Phila., Pe. -CS, SKT, TS, BP, C, G, J. P. GRC, ICA. Insuline Corp. St. New York, N. Y. -CDT, CPP MISC, of America SL, T INSULINE CORP. OF AMERICA VACÓLITE COMPANY, 3003 N. Henderson PHILMORE 30 -30 Northern St., MFG. CO., 113 University Place, New Blvd., Long Island City, N. Y., 1 "ICA " -M Dallas, Texas -CDT, CPP York, N. Y., "Philmore " -BP, P, J, SKT KNIGHT Allied Radio Corp. WEBSTER ELECTRIC CO., Racine, Wisconsin -CDT, RADIO ELECTRIC SERVICE CO., INC.. N. W. LAFAYETTE RADIO CORP., 100 6th Ave., New CPP Cor. 7th 6 Arch Sts., Phila., Pe. -BP, CD, CS, C, York, N. Y. -C, HA, M GRC, G, J MB, P T, TS, SKT, SL, MISC LAUREHK RADIO MFG. CO., 3918 Monroe Ave., RADOLEK CÓMPAN11, 601 W. Randolph St. Chi- Wayne, Mich, -HABC HEARING -AID PARTS cago, 111 -BP CD, CS, C, GC, G, J. MB, P, M. & G. HEARING AIDS COMPANY, 30 N. Mich- SKT, SL TS, MISC t igan Ave., Chicago 111.-C, HA, M, HABC REMLER CO., LYD., 2101 B;ant St., Ser Fra -dsco, M & H SPORTING GOODS CO., 512 Market St., Calif., "Remler"-SKT Phila, Pa. -C, M WALTER L. SCHOTT CO., 5264y W. Pico Blvd., MAJESTIC RADIO & TELEVISION CORP., Los Angeles, 2600 W. Calif. -CD SOth St., Chicago, 111.-HA, HABC MAURICE SCHWARTZ & SON, 710.712 Broadway, MAPCO COMPANY, INC., 83 S. 9th St., Min - Schenectady, N. Y. -BP, CD, CS, C, GC, G, J, MB, eapolls, Minn. -D, HA P, SKT, SL, T, TS, MISC JOHN MECK INDUSTRIES, 1313 W. Randolph St., Cases C SELECTAR MFG. CORP., 30 W. ISth St., New Chicago, III., "Audiogreph " Earphones York -HA and bone conductors N. Y.-C, J, P T. R. McELROY, 100 Brookline Ave., Boston, Mess. SHAKEPROOF LOCK WASHER CO., 2539 N. Keeler -M E Ave., Chicago, III -WL, MISC MONTGOMERY WARD & CO., 619 W. Chicago Microphones M H. B. SHERMAN MFG. CO., 22 Barney St., Battle Ave., Chicago, III. -HA, M, Resistors, Creek C special ultra- midget Mich. -C, SL E. A. MYERS & SONS, 306 Beverly Rd., Mt. MAXWELL Lebanon, variable R SMITH CO., 1027 N. Highland & Holly - Pittsburgh, Pa. -D, HA, HABC, M land Aves., Hollywood Calif. -SKT, T PARAPHONE HEARING AID, INC., 43® Euclid Tubes T SORENG- MANEGOLD do., 1901 Clybourr Ave., Ave., Cleveland, Ohio -HA, M Transformers & chokes . TC Chicago, III.-P, SKT, I PHILCO RADIO & TELEVISION SPAULDING CORP., Tioga & C Condensers, special ultra- midget FIBR CO., INC., 310 Wheeler St., Sts.. Philadelphia, Pa. -M Tonawanda, N. Y. -FS PHILMORE MFG. CO., 113 University Place, New STANLEY TOOLS, P. O. Drawer 1316, New Britain, York N. Y. "Philmore' -M Batteries, miniature . . . BM Conn. -G RADIO ELECTRIC SERVICE CO., INC., STEWART STAMPING N. W. Cor. Amplifier lamps (home use) AL CORP., 621 East 216 St., 7th 8 Arch Sts., Phila., Pa.-C, D, HA, M, New York, N. Y. HABC -MB, SL RADOLEK COMPANY 601 W. Randolph St., Audiometers A F. W. STEWART MFG. Chi- CORP., 340 W. Huron St., cago, 111. -C, D, HA, M, HABC Chicago, III., "'Stewart " -FS RCA MFG. CO., Front & Cooper Sts., Camden, AEROVOX CORPORATION, New Bedford, Mass. SUN RADIO CO. 212 Fulton St., New York, N. Y. N. J., RCA " -HA, HABC -S CD, CS, O, GRC, G, J, MB, P, S, SL, TS, T, ROTOPHONE MISC CORPORATION, 26 Journal Square, ALLIED RADIO CORP., 833 W. Jackson Blvd., Chi- Jersey City, N. J. -HA, HABC cago, III. -C, E, M, R, T, TC 316 RADIO -CRAFT for NOVEMBER, 1940 CLASSIFIED RADIO DIRECTORY

Wilmington Fibre Speciait Co. & WILLIAMSON, Ardmore, Pa. -C, PL, SO OHMOID, AMPLIFIER CO. OF AMERICA, 17 West 20th St., BARKER PARISIAN NOVELTY CO., 3510 S. Western Ave., BEE ENGINEERING CO., 7665 Grand River Ave., New York, N. Y. -C, E. M, R, T, TC 111. Detroit, Mich.-PL, SO, T, VC Chicago, -PL ARLAVOX MFG. CO., 430 S. Green St., Chicago, F. PETTINOS, INC., 1206 Locust St., Phila., BENTLEY, HARRIS MFG. CO., Conshohocken, Pa., GEORGE III.-TC Pa. -F MICROPHONE LABORATORY, INC., 830 "B -H " -T, FG Vulcanized Fibre Co. ASIATIC RADIO CO. INC., 145 Hudson St., PHENOLITE National St., g BIRNBACH Niagara Falls, N. Y.-SO Market New York N. Y.-C, SO, T, VC PREMAX PRODUCTS, DEVELOPMENT CO. 123 Bryant Ave. N., Glass Works AUDIO BOND PRODUCTS CO., 13139 Hamilton Ave., De- PYREX Corning Minneapolis, Minn. -C, E, TC, A RACOÑ ELEC. CO., INC., 52 E. 19th St., New PRODUCTS CO., 13139 Hamilton Ave., De- troit, Mich. -T BOND MOLDING CO., 326 Myrtle Ave., Boon- York, N. Y.-PL Mich. BOONTON 27th & Lake Sts., Mel- troit -C ton, N. J. -PL RICHARDSON COMPANY, THE BRUSH DEVELOPMENT CO., 3311 Perkins Ave., rose Park III., "Irsurok " -PL L. S. BRACH MFG. CORP., 55 Dickerson St., Cleveland, Ohio -E, M RADOLEK COMPANY, 601 W. Randolph St., Chi- 6th St., Newark, N. J. -SO VC CLAROSTAT MFG. CO., INC., 285 N. 111. F, FG, M P, PL, SO, TCF, TR, T, WM. BRAND & CO., 276 4th Ave., New York, N. Y. cago, -C, Brooklyn, N. Y. -R RADIO ELECTRIC SERVICE CO. INC., N. W. Cor. 1239 South Bend -M, T M, PL, SO, ELECTRO -VOICE MFG. CO., INC., 14th & Wal- 7th & Arch Sts., Phila., Pa. -G, FG, Ind. BRANDYWINE FIBER PRODUCTS CO., Ave., South Bend, -M Del. -F TCF, TR, T, VC ELECTRONIC APPLICATIONS, Brunswick. Maine- nut Sts., Wilmington, CO., 27th & Lake Sts., Mel. BUD RADIO, INC., 5205 Cedar Ave., Cleveland, THE RICHARDSON TC rose Park, 111. -M, PL, HR Reading, Mass. Ohio, "Bud " -PL SO GLOBE PHONE MFG. CORP., - 40th St., New MAURICE SCHWARTZ & SON, 710.712 Broadway, CELLULOID CORPORATION, 10 E. SO, C E. M, T, TC Protectoid " -PL Schenectady, N. Y.-C, F, FG, M, P, PL, RADIO CO., 12 West Broadway, New York, N. Y., "Lumarith HARRISON PAPER TUBE & CAN CO., 137 So. TCF, TR T, VC York, N. Y. -T THE CHICAGO RUBBER CO., INC., 605 W. Chicago, 111. -P, F SELF -VULCANIZING CORP., 500 5th Ave., New Albany Ave., 111. HYGRADE SYLVANIA FIBRE CO., Newark, Washington Blvd., Chicago, -PL Y. --T CONTINENTAL -DIAMOND 310 Wheeler St., York N. " -F, M, PL SPAULDING FIBRE CO., INC. RESISTANCE CO., 401 N. Broad Del., Diamond," "Dilecto, Y., "Spau)dite," "Armite," INTERNATIONAL GLASS WORKS, Walnut St., Corning, Tonawanda, N. St., Phila., Pa.-R CORNING P Y., FG "Spauldo " -F, LAFAYETTE RADIO CORP., 100 6th Ave., New N. "Pyrex " -SO Spaulding Fibre Co., Inc. COTO COIL CO., INC., 71 Willard Ave., Provi- SPAULDITE, York N. Y. -E M, R, T, C Spaulding Fibre Co., Inc. RADIO MFG. CO., 3918 Monroe Ave., dence, R. 1.-C, SO SPAULDO, LAURtHK L. Crowley & Co. Wayne, Mich. -C, E CROLITE -Henry STUPAKOFF LABORATORIES, INC., 6627 Hamilton HENRY L. CROWLEY & CO., I Central Ave., West M & G HEARING AIDS CO., 30 North Michigan Ave., Pittsburgh, Pa. -C N. J., "Crolite " -F St., New York, Ave., Chicago, 111.-C, E, M, P, T, TC Orange, SUN RADIO COMPANY, 212 Fulton DIST. CORP., 1801 Farrin St., Hous- TCR, TR, T P. R. MALLORY & CO., INC., 3029 E. Washington CRUMPACKER N. Y. -C, F, G, M, P, PL, SO, Indianapolis, Ind. -R ton, Tex. -TCF, TR SYNTHANE CORPORATION, Highland Ave., Oaks. St., MOLDING CO., 1428 N. Wells MONTGOMERY WARD & CO., 619 W. Chicago HARRY DAVIES Pa., "S thane " -PL R, T, IC St., Chicago 111.-PL TAYLOR FIBRE CO., Norristown, Pa. -F, PL Ave., Chicago, 111.-C, Fibre Co. COMPANY, INC., 61 Sherman St., DIAMOND, Continental- Diamond CORP., 484 -90 Broome NATIONAL Diamond Fibre Co. TELERADIO ENGINEERING Malden, Mass. -TC ' DILECTO Continental- New York, N. Y.-C F, M. PL, T NEMOURS & CO., INC., Plastics St., 601 W. Randolph St., Chi- E. I. DUPONT DE 191 St., RADOLEK COMPANY, N. J. -PL UNITED RADIO MFG. CO., Greenwich R, T, TC Dept., 626 Schuyler Ave., Arlington, cago, III. -C, E, M Tona- New York, N. Y. -HR 26 Journal Square, DUREZ PLASTICS & CHEMICALS, INC., North OTOPHONE CORPORATION, " HOPE WEBBING CO., P. O. Box 1495, Providence, Jersey City, N. J. -C, E, M, AL wanda, N. Y., "Durez -PL MFG. CO., INC., 424 W. 33rd St., R. I.-FG SELECTAR MFG. CORP., 30 W. 15th St., New York, HAMMARLUND ELEC. & MFG. CO., E. Pittsburgh, New York, N. Y. -SO WESTINGHOUSE N. Y. -M Pa. EBY, INC., 4700 Stenton Ave., Phila- -PL SOLAR MFG. CORP., Avenue A & 25th St., Bayonne, HUGH H. FIBRE SPECIALTY CO., Wilming- Pa. WILMINGTON N. J. -S delphia, -PL "Ohmoid " -PL, F CO., 105 E. 29th St., New York, ton, Del., "Fyberoid," TAY BERN EQUIPMENT CORP., 135 Liberty St., EMPIRE NOTION MILLS, INC., 112.130 26th St., Brooklyn, N. Y. -TCF, T, VC ZOPHAR New York, N. Y. -E, M, T, TC, BM Pa.- N. Y.-PL, W TELERADIO ENGINEERING CORP., 484 -90 Broome ERIE RESISTOR CORP., 644 W. 12th St., Erie, St. New York, N. Y.-TC PL 26 S. Jefferson St., Chicago, TELEX PRODUCTS CO., Minneapolis, Mirn. -C FEDERAL SALES CO., 42 W. 48th St., New I11, -T TRANSDUCER LABORATORIES, Fulton Si., INTERCOMMUNICATING York, N. Y. FISCHER DISTRIBUTING CORP., 222 -M P, PL, SO, TCF, THORDARSON ELECTRIC MFG. CO., 500 W. New York, N. Y. -C, F, FG, M, SYSTEMS Huron Street Chicago, III. -TC TR, T. VC 113 N. Broad St., UNITED TRANSFORMER CORP., 150 Varick St., New M. M. FLERON & SON, INC., York, N. Y. -TC Trenton, N. J. -SO 4638 Grove 5221 -27 Greere St., Phila., FORMICA INSULATION CO., Spring WIRT COMPANY, "Formica " -PL Pa. -R Ave., Cincinnati, Ohio, FYBEROID Wilmington Fibre Specialty Co. GENERAL CEMENT MFG. CO., 1041 Kilbourn Ave., Rockford, 111.-T, VC, TCR, R INSULATION GENERALCERAMICS CO., 30 Rocke?eller Plaza, New York, N. Y. -B, C, SO Wired W GENERAL CERAMICS CO. PLANT NO. 3, Keasbey, Wireless WS N. J.-C, SO GENERAL ELECTRIC CO., Lynn, Mass. -M GENERAL ELECTRIC CO., Schenectady, N. Y.- "ACA ", Amplifier Co. of America. C, F, P, PL, SO T, VC, MY RADIO CORP., 833 W. Jackson Blvd., Chi - New ALLIED HARRISON RADIO CO., 12 W. Broadway, cago, Ill., 'Knight " -P, R York, N. Y.-C, F, G, d, SO, TCF, TR, T, VC AMERICAN COMMUNICATIONS CORP., 123 Lib- Bushings B HAWLEY PRODUCTS CO., 201 N. 1st Ave., St. erty St., New York, N. Y. -W Ceramics C Charles, 111. -IC AMERICAN TELEVISION CORP., 130 W. 56th St., ICA, Insuline Corp. of America New York, N. Y. -W WS Enamel E INSUROK, Richardson Co. AMPLIFIER CO. OF AMERICA, 17 W. 20th St., 3030 Northern Fiber F INSULINE CORP. OF AMERICA, New York , N. Y., "ACA " -W City, N. Y., "ICA " -C, SO, T, Ave., Fiber -glass FG Blvd. Long Island AUTOCRAT RADIO CO., 3855 N. Hamilton VC, F PL Chicago, III., "Autocrat -Phone' -W Friction Tape FT INSULATION MANUFACTURERS CORP.. 565 W. BANK'S MFG. CO., 5019 N. Winthrop Ave., Chi- Mica M Washington Blvd., Chicago, 111. -F, FG, M, P, cago, III -W, WS Paper P PL, TCF, TR, T. VC BARKER & WILLIAMSON, Ardmore, Pa. -WS INSULATION PRODUCTS CO., 504 N. Richland St., BELFONE, Bell Sound Systems, Inc. Plastics PL Pittsburgh, Pa. -PL BELL SOUND SYSTEMS, INC., 1183 Essex Ave., & INSULATOR CO., 18 Stand -off insulator . . . SO IRVINGTON VARNISH Columbus, Ohio "Belfone " -W Irvington. N. J., "Iry -O- Volt " New Tubing (varnished) T Argyle Terrace, - DAVID BOGEN CO., INC., 663 Broadway, FG, PL, T VC York, N. Y. -W . . . VC Co. Varnished Cambric IRV -O -VOLT, Irvington Varnish & Irsulator BRUSH DEVELOPMENT CO., 3311 Perkins Ave., 233 Broadway, New Tape (cloth friction) . . TCF ISOLANTITE INCORPORATED, Cleveland, Ohio-W York, N. Y., "Isolantite " -B, C, SO SOUND SYSTEMS CO., 200 E. Illinois Tape (rubber) . . . . TR "Johnson " CHICAGO E. F. JOHNSON, Waseca, Mi,n.. - St., Chicago, 111.-W, WS Hard -rubber HB C, SO 'CLARION, Transformer Corp. of America PO KELLOGG SWITCHBOARD & SUPPLY CO., 6650 S. Polystyrene TEL. & ELEC. CORP., 70 Britannia St., 111. -TR CONN. MY Cicero Ave., Chicago, Conn. Mycolex RADIO CORP., 100 6th Ave., New York, Meriden, -W LAFAYETTE DIST. CORP., 1801 Fannin St., Hous- Insulation cases . . . . IC N. Y. F, FG, M, P, PL, SO, TCF, TR, T, VC CRUMPACKER -C ton, Tex. -W LAMICOIó, Mica Insulator Co. Armitage Ave., Chi- PROTECTOID. Celluloid Corp. DE VRY CORPORATION. IIII ACME WIRE CO., New Haven, Conn. -VC LUMARITH cago, Akron, SO MAAS & WALDSTEIN CO., 438 Riverside Ave., THE AKRON PORCELAIN CO., Ohio -C, WALDLID RADIO MFG. CORP., 436 Lafayette St., ALDEN PRODUCTS CO., 715 Center St., Brockton, Newark, N. J.-E York, N. Y. SCREW & SUPPLY HOUSE, 215 New -W Mass. -PL, T MANUFACTURERS INDUSTRIES MFG. CO., Red Bank, W. Illinois St., Chicago, 111. -T, VC ELECTRICAL ALLIED RADIO CORP., 833 W. Jackson Blvd. Chi- N. J. T, MFG. CO., Mt. Carmel, 111.-SO -W cago, 111.-C, F, FG. M, P, PL, SO, TCF, tR, MEISSNER 2667 East Grand 200 Varick St., New York, ELECTRONIC CONTROL CORP., VC MICA INSULATOR CO., Mich. -W FG, M, P PL, T, VC Blvd., Detroit, ALPHA WIRE CORP., SO Howard St., New York, N. Y. -F, CO., St. Charles, III.-WS MICARTA FABRICATORS, INC., 4619 Ravenswood ELECTRONIC PRODUCTS N. Y. -T ELKAY MFG. CORP., 200 5th Ave., New York, N. Y. American Lava Corp. Ave. Chicago, III. -F, PL, T ALSIMAG- MFG. CO., INC., 150 Exchange -W AMERICAN LAVA CORP., Cherokee Blvvd. & Mfrs. JAMB MILLEN INC., 305 East 63d St., Malden, Mass. -C, PL, SO ESPEY MFG. COMPANY, Road, Chattanooga, Tenn., ' Alsimag St., New York, N. Y. -W 1250 Van Buren St., J. W. MILLER CO., 5917 S. Main St., Los Angeles. AMERICAN PHENOLIC CORP., EXECUTONE, INC., 415 Lexington Ave., New York, Chicago, III., "Amphenol "-C, PL. SO, PO Calif., 'Miller " -SO WARD & CO., 619 W. Chicago Ave., N. V. -W AMERICAN RADIO HARDWARE CO., 476 Broad- MONTGOMERY CORP., 222 Fulton St., 111. PL, SO, CF, TR FISCHER DISTRIBUTING sy New York, N. Y., "Ancco" -PL, SO Chicago, -C, York, N. Y -W WS MYCALEX CORP. OF AMERICA, 7 E. 42nd St., New AMPHENOL, American Phenolic Corp. THOMAS B. GIBBS & CO., 900 W. Lake Si., Chicago. ARHCO, American Radio Hardware Co. New York, N. Y. -C -C, National Company 111. -W ARMITE, Spaulding Fibre Co. Inc. N RADIO CORP., 118 E. 25th St., New York, Y. NATIONAL COMPANY, 61 Sherman St., Malden, GUIDED AUBURN BUTTON WORKS, INC., Auburn, N. Y. Mass. PL, C N. W, WS -PL -SO, 12 W. Broadway, New NATIONAL VULCANIZED FIBRE CO., Wilmington HARRISON RADIO CO., EAKELITE CORPORATION, 247 Park Ave., New York, N. Y. -W, WS York, N. Y. -P Del., "Phenolite " -F, P, PL 317 RADIO -CRAFT for NOVEMBER. I 9 4 0 CLASSIFIED RADIO DIRECTORY

" INTERCALL SYSTEt.';, - & No..00d, Day- TALK -A -PHONE MFG. CO., 1847 S. ton. Ohio Millard Ave., CRUMPACKER DIST. CORP., 1801 Fannin -W Chicago, 111. St., Hous- -W ton, Tex. R CHARLES JACK MFG. CORP., 27 E. Philadelphia -P, TELEMOTOR CORPORATION, 260 5th Ave., New ELECTRO PRODUCTS St., York, Pa. -V/ York N. Y.-W LABORATORIES, 549 W. Ran- JONES -ORME CO., 2233 dolph St., Chicago, 111. -P, R University Ave., St. Paul, TELERADIO ENGINEERING CORP., 484.90 Broome Minn, -W St., FISCHER DISTRIBUTING CORP., 222 KARADIO New York N. Y. -''í Fulton St., CORPORATION, 2233 University Ave., St. TELEX PRODUCTS CO., hl -nrolis, New York, N. Y.-P, R Paul Minn. -W WS Mir.n, -W TRANSDUCER LABORATOv M. M. FLERON & SON, INC., 113 N. Broad St.. KELLOGG SWITCHBOARD & SUPPLY CO., 6650 42 W. 48th St., New York, N. Y. Trenton, N. J.-R S. Cicero Ave., Chicago, 111.-W -W TRANSFORMER CORP, dERICA GENERAL ELECTRIC CO., Schenectady, N. Y. -R *KNIGHT, Allied Radio Corp. OF 'r 69 Wooster St., New York, N. Y. GUIDED RADIO CORP., IIB E. 25th St., New York, LAFAYETTE RADIO CORP., 100 6th Ave., New TRANSMARINE RADIO, !NC., 1184 Broadway, N. Y. -P York, N. Y. -W Hewlett L. I., N. Y. WS -W, HAMMOND MFG. CO., Guelph, Ontario, Canada LAKE MFG. CO., 2323 Chestnut St., Oaklard, Calif., UNIVERSAL MICROPHONE CO., Irglewood, Calif. -R "Voycall " -W -W HARRISON RADIO CO., 12 W. Broadway, New MAJESTIC RADIO & TELEVISION VIBRALOC MFG. 1273 CORP., 2600 W. CO., Mission St., San Fran- York, N. Y. -P, R 50t11 St. Chicago, III. -W WS cisco, Calif. -W HERBERT H. HORN, 120! S. Olive St., Los Angeles, MILES REPRODUCER CO., INC., 812 Broadway, VOYCALL, Lake Mfg. Co. Calif. -P New York N. Y.-W, WS THE WEBSTER CO., 5622 W. B.comi -gdale Ave., INSULINE CORP. OF AMERICA, 30 -30 Norther MILLION RADIO & TELEVISION LABS., 685 Chicago, 111.-W W. Blvd., Long Island Citi, N. Y.-P, R Ohio St., Chicago, Id., WEBSTER ELECTRIC "Million " -W CO., Rac:'e, Wis. -W KENYON TRANSFORMER CO., INC., 840 Barry St., MONTGOMERY WARD & CO., 619 W. Chicago WESTERN ELEC. CO., 300 Ccrtral Ave., Kearny, Bronx, N. Y.-P Ave., Chicago III. -W N. J.-W LAFAYETTE RADIO CORP., 100 6th Ave., New C ?ERADIO MFG. CO., 13th & I' d.ana Sts., St. WESTERN SOUND & ELECTRIC LABS., INC., 311 York, N. Y.-P, R

Charles, 111. W. : -W Kilbourn Ave., Milwa :' Wis. -W MEISSNER MFG. CO., Mt. Carmel, 111. -R PACENT ENGINEERING CORP., 79 Madison Ave., P. R. MALLORY & CO., INC., 3029 E. Washington New York, N. Y., "Pacent " -W St., Irdianapolis Ind. -P. R PHONOTONE LABORATORIES, INC., S. E. 15th St., LINE FILTERS M & H SPORTING GOODS CO., 512 Market St., Washington Ind -W Phila., Pa.-P, R RACON ELECTRIC CO., INC., 52 E. 19th St., New MONTGOMERY WARD & CO., 619 W. Chicago York N. Y. -W Ave., Chicago, I11. -P, R RADE,< CORPORATION, 1733 Milwaukee Ave.. Chi- OHMITE MFG. CO., 4835 W. Flournoy St., Chicago. cago, 111. -W WS III. -P RADIO ELECTRIC SERVICE CO., INC., N. W. Cor. PHILCO RADIO & TELEVISION CORP., Phila., Pa. 7th & Arch Sts., Phila., Pa.-W, WS -P R PHILMORE MFG. RADIO RECEPTOR CO., INC., 251 W. 19th CO., INC., 113 University Place, St., New York, Y. New York N. Y. -W N. -R Power filters (industrial) . P RADEX CORPORATION, 1733 RADIO WIRE TELEVISION, INC., 100 6th Ave., Milwaukee Ave., Chi- cago, 111. New York, N. Y. -W, WS Radio set (for the home) . R -R RADIO ELECTRIC SERVICE CO., INC., N. W. RADOLEK COMPANY, 601 W. Ra-dolp' St., Chi- Cor. 7th & Arch Sts., Phila., Pa. -P, R cago, III., "Radolck " -W WS AMERICAN COMMUNICATIONS CORP., 123 - Lib RADOLEK COMPANY, 601 W. Randolph St., Chi - ey St., New York, N. P, RCA MFG. CO., Fro -t & Cooper Sts.. Ca-d5., Y.- R cago, 111. -P R AMERICAN CONDENSER CORP., N. J. W, WS 2509 5. Michigan MAURICE SCHWARTZ & SON, 710 -712 Broadway, Ave., Chicago. 111. -P, R Schenectady, N. Y. --P, R REGAL AMPLIFIER MFG. CORP., 14 W. 17th St., AEROVOX CORPORATION, Nu.. B- s Mass, New York, N. Y. WS od, -R SPRAGUE PRODUCTS CO., North Adams, !,lass. -W, R BELDEN MFG. CO., 4647 W. Va- B -e- Si., Chicago, -P, REMLER CO., LTD., 2101 Brya -t St., San 111. Frarcisco, -R SUN RADIO CO., 212 Fulton St., New York, N. Y. Calif., "Rernler " -W BUD P, RADIO. INC., 52]5 C' : - A C'evrla-d, - R SETCHELL CARLSON, INC., 2233 University Ave., Ohio -R TECHNICAL APPLIANCE CORP., 17 E. 16th St., St. Paul, Minn. -W CARRON MFG. CO., 4,5 S. A6 ^-i,-- St.. C'cago, New York, N. Y. -R III. -R TOGE DEUTSCHMANN S'LLCOX RADIO & TELEVISION CORP., 60 Wall CORP., Washington St., Tower, New York, N. Y.-W, WS CONTINENTAL CARBON ¡NC., 13900 Lorain Ave., Carton Mass. -P Cleveland. Ohio -P, R UNITED TRANSFORMER CORP., 150 Var;ck SUN RADIO CO., 212 Fulte St., New St., New York, N. Y.- CONSOLIDATED WIRE & ASSCC'ATEJ York, N. Y. W, WS CORPS., 512 -P S. Peoria St., Chicago, I11. -R (Continued wart month.)

Mr, Radio Serviceman: RSA MEANS BUSINESS!

New business promotion plans and new member -helps spell increased profits for RSA members at the start of the new season. Watch for the RSA Replacement l'arts Guide -New Broadcast Promotions -New Member Helps! Don't be the last man in your neighborhood to join RSA. Send the coupon Today!

Let's =mom MAIL THIS Grow Together COUPON NOW!ammels, in 1940! RADIO SERVICEMEN OF AMERICA, INC. Dearborn St., Chicago, Ill. I am interested in RSA Membership. Tell rue about it. RADIO SERVICEMEN Name OF AMERICA, Inc. ' \ddress Reliable Service Assured I JOE MARTY, JR., EXECUTIVE SECRETARY , City Statc 304 S. DEARBORN STREET, CHICAGO, U.S.A.

313 RADIO -CRAFT fer NOVEMBER, 1940 SHOP NOTES -KINKS -CIRCUITS

HUM ELIMINATION touching the chassis; or in the case of form- I fitting shields, bend the grounding prong 1941 OUTPUT the shield has KNEW TRANSFORMER away from the shield so that no contact with chassis. PROFIT pGUIDE Next fasten a short piece of wire from the center of a 2,000 -ohm potentiometer (1IIdu'1 volume control to chassis, and connect another piece of insulated wire from one of UNIT the outside connections of the control to the r DELIVERS HUM- tube shield. When the control arm is rotated COMPLETE SELECTIONS SUCNIN all resistance between the GUARANTEED QUALITY VOLTAG so as to remove shield and chassis the tube circuit will not Faster Delivery oscillate as before, but when rotated so as \lost complete stocks of t'nt- rsal and Exact Ihgd leate Ile - OHMS. to introduce resistance between shield and ¡h rrment and Repair l'aru. POTEN. chassis it will regenerate, and if turned far Radio Sets, and Amateur Sup - L will go into oscillation. `LOW- VOLTAGE WINDING ON enough P. A. EQUIPMENT POWER TRANSFORMER SUCH Many radio amateurs who use ordinary Separate amplifiers or complete AS 2.5V. SECONDARY. )'stems with any desired as- receivers will find this a very inexpensive ointment of speakers. horns, and quickly- constructed beat oscillator for athes and microphones, Ever).- HUM has always been one of the Service Thing from 5 to 100 watts. I've receiving code and locating weak stations; Prices that save metro for you. man's problems in radio repairing. receiver twice as sensitive found one way, here illustrated, of effective it also makes the ELECTRICAL APPLIANCES by the regeneration. -., for you! Standard Brand Electric Irons, especially when it originates Irons, Vacuum hum reduction, Receiver circuits which will not oscillate 'i -. T, a.rers, Percolators, Warne The trick is to feed a small 1.., _, r., Clocks, Mixers. etc.. at lowest prices. in the speaker. from tube, will do s' voltage to the voice coil in an opposite with the shield removed A.C. is on the tube but insulated MAIL THIS ¡COUPON TODAY to hum voltage originating in the so if the shield phase the Receiver using metal tube., The RADOLEK Co. speaker. The amount of hum voltage fed to from the chassis. can be used this way also by substituting n ,1 W. Randolph SI., Chicago, Dept. C -47 can be adjusted by means of New 1041 Profit Guide FREE the speaker glass tube of the same number (called the 's 'id the Radio the potentiometer's slider in order to bal- Name G series) and then putting a shield over it ance -out the unwanted hum voltage. It has Dc:dc, . as illustrated. proven very helpful to me, especially in the .,r, iceman r tmateura (MRS.) OLE FUGLESTAD, older sets. Lake, North Dakota. HAROLD R. KUNTZ, Powers Brooklyn, N. Y. WARNING TO RADIO -CRAFT READERS UNIFORM HOUSINGS FOR TEST Radio -('raft has no representatives in the field ,oliciti ne subscriptions, in the "door -to- door" EQUIPMENT fashion. Pay no money to any person who cornea to your home, store or service shop and represents himself as being an agent for Radio- Craft. Subscriptions may be safely obtained only from authorized subscription agencies, whose names we shall be glad to furnish, or directly from us by mail. Address your letter to Subscription Dept., Radio- Craft, 20 Vesey St., New York, N. Y.

get -nil £I¢cttic l7tyShavet ABSOLUTELY FREE!

TO bring testing instruments of different JUST THINK OF IT-you can get absolutely panel sizes to a uniform height, and above FREE, the useful DRY ELECTRIC SHAVER the level of the receiver under test, the which is shown at the left. This ELECTRIC in cabinets DRY SHAVER is sent to you by the publishers re- installation of the instruments RADIO- CRAFT, of identical height and fitted with drawers with a one -year subscription to for test leads, etc., offers a practical and Here Are the Features of The inexpensive solution. Utilizing separate cab- ELECTRIC DRY SHAVER inets, rather than combining the instru- Constructed of metal with attractive red bronze ments on one panel, permits rapid inter- finish. Scientifically constructed to give perfeetiy clean shave. 5 -foot rubber Insulated cord and plug. change of their positions to meet the con- Constructed to last for many years. venience of the technician. Operates from 110volt, 60 cycle A.C. elec- EDDY RADIO SERVICE SYSTEM, tric line. Carries two -year manufacturer's guarantee. A fine quality, self- sharpening Springfield Gardens, N. Y. toilet necessity. Send your subscription to RADIO- (7tAFr for Ono Year (12 issued and receive ab- IMPROVISED BEAT-FREQUENCY solutely FREE one of these remarkable Electric Dry Shavers. New subscribers OSCILLATOR are accepted or you may extend your cres- t subscription another twelve months. OPERATES ON Mall your remittance of $2.00 (plus 25c for shipping charges on Shaver) to the 110 -VOLT, 60 -CYCLE publishers. (Canada and foreign A.C. LINE 22.75.1 You will receive your DRY ELECTRIC SHAVER immediately by return mall. Use coupon betas to enter your subscription. RADIO -CRAFT 20 Vesey Street. New York. N. Y.

N 41050"* RADIO- CRAFT. 20 Vesey Street. New York, N. Y. Gentlemen: Enrinsed find my remittance M 12.00 for which enter my o,bsrrlptIon to RADIO.CRAFT for one year 112 Issues). Send me immediately FREE, ELECTRIC DRY SHAVER (Canada and foreign s. 52751. In t'. S. add only 25e additional to corer shipping chose. on WE SHIP ELECTRIC DRY Shaver. way to add a beat O New Subscriber O Extend Present subscription HERE is a simple SAME DAY oscillator to any superheterodyne receiver SHAVER THE SUBSCRIPTION Name with only the addition of a 2,000 -ohm vol- YOUR ORDER IS RECEIVED. ume control which any one can put on ex- Address ternally without interfering with the receiver circuit. Simply raise the tube shield City State (Rend remittance by check, money order or unused L1.8. Postage Stamps on the 1st intermediate -frequency amplifier CLIP COUPON - Ih :i..0 b.f.,. Ir Pas °,nd . -'Il ar ,t:anp'.1 RC -1140 tube and use some tape to keep it from AND MAIL! RADIO -CRAFT for NOVEMBER, 1940 319 BOOK REVIEWS

PERPETUAL TROUBLE SHOOTER'S MAN- GEOPHYSICAL UAL, Vol. Xl. Published by John F. Rider (1940). Size. 9 x 11t_, hard cover and loose -leaf PROSPECTING OUTFITS binding, over 1,600 pages. Price $10, Newest addition to the well -known Rider's Service Manuals is the 1.600 -pg. volume No. XI which differs from preceding manuals in 2 re- PUBLIC ADDRESS EQUIPMENT spects; the text structure been has changed to r Co. of America 263 afford more complete service information in less ' -'oi wund Equipment space; and, a new principle of indexing has been Co 953 : ,, applied which makes it easier for Servicemen to Merk Industries 279 TrnaRIFAx spot desired ci aeons. Included with the manual 13'4+ ltrprodueer Co. 279 is a aptrial IS-pg. booklet combining a con- ',I ic Master Mfg. Co venient index to circuits; and, an analysis of . \ Mfg. Cu., Inc circuit features in the new radio sets. (.. Turner ('umpnny - u gy IdM.nP' Also included with this manual is a "vest parket .nl Microphone Co., Ltd manual supplement" containing a con- 'r Laboratories venient index to the manual and important in- -1/eCost, -r. 171e. formation such as transformer. resistor and condenser color codes, etc.. for which the Serviceman finds everyday tsse. PUBLISHERS FF.SSENDEN- BUILDER OF TOMORROWS, Auld, Publisher 261 by Helen M. Fessenden (1910). Published by Data Print Co BLUE PRINTS and INSTRUCTIONS Coward- McCann. Inc. Size. 6 x 9 ins., cloth cover, Miller, Wayne 362 pgs. Price. $3.00. National flans Insu for Building the Follow ing 'Pressure In the biography. "Fessenden- Builder of To. Iü,,leraft Publications, Inc 262, 30s Finders and Prospecting Outfits morrows," the wife of the former professor of Radio & Technical Pub. Co 260 Folder 1. electrical engineering at Purdue University, No. The "Rndinfiector Pilot " --con- In- Radio Publications 310 sists of a 2 -tube diana and Western University transmitter and 3 -tube at (University of Supreme Publications receiver. Principle: radiated Wave from Pitt -borghi, has erected a monument to the work "9 295, 302 transmitter loop is reflected back to receiver of Technifax 302, 320 loop. Emits visual Reginald A. Fessenden, one of the pioneer and aural signals. Tubes builders of the Radio Empire. used: two 1A5G-two 1N5G -one 1H5G. Folder No. 2. The "Harmonic Frequency Lo- He is perhaps best known for the system of RADIO PARTS radio telegraphy cator"- Transmitter radiates low frequency and telephony which bears his Amperitc wave to receiver, tuned to one of Harmonics name. The Fessenden System of communication Co Inside Front Cover of transmitter. Using regenerative circuit. included only some of his 500 patents, others Bright Star Battery Company 269 Emits aural signals. Tubes used: one 1G6G Dumont Electric Cu.. Inc -one 1N6G. widely known being for example a marine depth 27 Folder No. 3. The "Beat -Note Indicator" -Two finder and a system of -submarine signaling. Hammarlund Mfg. Co 271 oscillators so adjusted as to produce beat - Here for the first time is presented the inside International Resistance Co 267 note. Emits visual and aural signals. Tubes life story of the trials and problems that beset Nu ti "nab Union Radio Corp. 277 used: Three type '30. a man who as early as 1900 Folder No. had demonstrated Ohmite Mfg. Company 296 4. The "Radio-Balance Surveyor' his own system of radio telephony; and in 100 -a modulated transmitter and very sensi- Solar Mfg. Corp 273 tive loop receiver. Principle: Balanced 2-way transatlantic radio telegraphy. loop. Emits visual and aural signals. By tri- angulation depth of objects in ground can TELEVISION RECEIVING EQUIPMENT. by RADIO SETS be established. W. T. Cocking (1910). Published by Iliffe & Sons Tubes used: Seven type '30. Guldentone Radio Folder No. 5. The "Variable Inductance Moni- Ltd.. London. England. American agent: Norde- Co 273 tor"-- single tube oscillator generating mann Pub. Co., Inc. Size. 3 x 7' ins.. cloth Howard Radin C'o 281 fixed modulated signals and receiver em- cover, 167 illustrations. Son pgs. Price, 7 10; Midwest Radio Corp. 305 ploying two stages R.F. amplification. in U. S.. $2.25. E. H. Scott Radio Works on the inductance principle. Emits Lab.. Inc 292 aural signals. Tubes used: six type '80. Here is a meaty book on television which pro- Folder No. 6. The "Hughes Inductance -Bal- serves for posterity the advances in television RADIO SUPPLY HOUSES ance Explorer " -a single tube Hartley os- which took place in England to cessation cillator transmitter sensitive prior Allied Radin Corp 989 and 3 -tube re- of activities "for the duration." The book is ex- ceiver. Principle: Wheatstone bridge. Emits :Anchor Radio Distributing Service 257 aural signals. cellently illustrated. The following chapters se- Tubes used: two type '30- Burstein- e lected at random impart APPIetst Co 2 -1 one type '32 -one type '33. an impression of its Lafayette Folder No. 7. The "Radiodyne Prospector" - runtents. Radio Corp 301 a completely shielded instrument. Principle: Chapter 1- General Principles of Television; Mukluk Co. 31 n Balanced loop. Transmitter. receiver and Chapter 12- Superheterodyne Interference Prob- batteries enclosed in steel box. Very large lems ; Special SCHOOLS field of radiation and depth of penetration. Chapter I6- Telcvis Cireuit:t; Emits aural signals. Tubes used: two 1N5G Chapter 19- Faults and Their Remedies; Chap- Capitol Radio Eng. Inst 257 1H5G ter 20-Television Servicing. -one 1G-1G-one -one 1Q5 -one 1G4. Lincoln Engineering School 261 With any one of the modern geophysical MOTOROLA AUTO -RADIO SERVICE MAN- National Rudi,, Institute 257 methods described in the Blue -Print patterns. National Schools Radio outfits and instruments can he con. UAL-1941 Edition. Published by Supreme Pub- 21 structed to locate metal and ore deposits lication.. Size. 81/2 a ll ins.. stiff paper rov:r. New lurk Y.M..C.A. Schools 261 (prospecting) ; finding lost or buried treas- 96 pgs. Price, SI. Radio Training Assoc 261 ures; metal war relics; sea and land mines This diagram, alignment RCA Institute- and "duds "; mineral deposits; subterranean and tronhle- shunting 261 water veins; oil elelosita (under certain manual is described as containing "information Sprayberry Academy of Radio !61 cir- for repairing every Motorola radio." cumstances; ; buried gas and water pipes ; tools or other metalli' object- sunken in wa- In addition to a large number of Motorola TEST EQUIPMENT ter. etc.. etc. (Galvin Mfg. Corp.I radio receiver diagrams. the Meissner hlfg. Company Lath set of blueprints and instructions b,s,k contains individual sentions titled no fol- enclosed in Rodin City Products Co heavy envelope 19,,' x 12''-). Blueprints 22" x lows: service hints, coil color voiles. alignment 34'; elpht paste illustrated S',' x II- fold. Readrite Meter Works - er of procedure. installation of the Magic EIiminnde instructors and construction data . CO0 Add ic tor postage for eI imianti,,n of ignit interference, eliminat- I(CA Manufacturing Co.. Inc ing other types of interference, servicing Simpson The complete set of seven folders push- Electric Company..Inside hark C Shipping weight 2 lbs. (add button tuning controls, ti-e of oscilloscope in Superior 23e for ship - iJle Instruments Co 271. 273, was anywhere in 1.1.4 .A.1 alignment. and service details on the electric Supreme Instruments Corp automatic tuner. book The euro9robs with a Triplett Electrical Instrument i E:I:IINIEí1X general diseussiun of tin s. Co... Back C. RCI t4) 1417 S. STATE ST. CHICAGO. ILL. NOTIONS COMPI.EMEN'rAIR:S SIR LES TUBES TUBES ELECTRONIQUES, hp M. Chauvierre Hygrade Sylvania Corp...... 7 (1940). Published by Dun'd, Paris. France. Size, TECHNIFAX 1917 So. State. Chicano, Ill. x 8S:_ ins., stiff paper cover, profusely. illustrated. 201 pin. Price. 91 francs. MISCELLANEOUS Enclosed herewith S for which mail to address below: This newest look, 1.y a profes -or at the (vent rd Barber & Howard Sehoel of Radio and as tunsslting engineer. sup- C'I: Treasure Finder N. I. 7, 3, 4. 5. 6. 7. soi lied Section plements the previously -published work of Mes uy Lancaster, Allw ine & Rommel Complete set of seen folders. in France. Chaffee in America and Itarkhnnsen Radio Servicemen of America in England. The bos,k discusses in theoretical Remington vaME terms the elements of elect roan ie upon ti,,n. Rand. Inc Essentially mathematical. the Iok is tie, heavy Woodstock Typewriter Co for nog resist ion except by those who are familiar ADDRESS with technical French. The following are the titles ( While every precaution is taken to insure of a few chapter headings select rol nt random: accuracy.cy. we cannot guarantee against the Chapter I CITY . STATE ...... , is a study of lannps in general; Chap- possibility of an occasional change or omis- RC -1140 ter III, distortion; Chapter IV, power amplifica- sion in the preparation of this index.) J tion: Chapter VI, detection, 320 priie..l et Ole U.S.A. RADIO -CRAFT for NOVEMBER, 1940 You can't find it in the dictionary . . . . but you can find if in AMY'S SIMPSON LINE IF you saw Simpson Instruments at the show you saw something that ordinary words can't describe. In Hollywood they call it "oomph"

. . . today's fast way of saying "more of everything ". The Model 400 Tube tester (opposite) is typical of these Simpson Testers that have more of MODEL 400 TUBE TESTER everything more class, more precision, more NEVER before have so many ... advanced features been corn- engineering against obsolescence. We studied bined in a tube tester. These features include: your right -now testing problem; then solved it UNIT DESIGN the socket panel and the roll chart can be individually all the way in an instrument as modern as to- removed. Replacement units can be ordered for those needing recondi- morrow. tioning or replacement while you keep right on using the tester. Obsolescence effects only individual Right down the line Simpson Instruments have units -not entire tester. Old units can be returned for credit so that you can keep the tester up to date been designed by and for your needs. A few at low cost. in the 1940 hit SPARE SOCKETS -Two spare sockets leaders Simpson parade are (one large and one small) are provided in addition to sockets for 4, briefly described here. All are covered by the Model S00 5. 6, 7 and 8 -prong tubes, loctals, bantams, midgets and miniatures. handsome new catalog. VISUAL GUIDE -Note guide lines that "tie in" roll chart with switches, preventing errors. Ask for your copy THREE-WAY SWITCHING --Each toggle switch has "off" position so that any prong can be left open. Valuable in testing tubes like ILNG or tapped filament tubes like 35Z5: also SIMPSON ELECTRIC COMPANY various sections of multipurpose tubes in present or future groupings. 5216 -18 Kinzie Street, Chicago, Illinois SPEED ROLL CHART -- Smoother, better operation than ever before. In addition to regular listing has numerical index which speeds up reading. Also has window for writing MODEL 310 data for at least 50 new tubes on blank portion of roll chart. Entire chart easily and inexpensively replaced. SIGNAL GENERATOR YOUR NAME ENGRAVED ON THE PANEL -Simply send us the Reports from inde. plate. No charge whatever. pendent laboratories Your price on Model 400 $ 36.00 prove this to be the with most stable and ac- MODEL 500. Same instrument in display cabinet big, curate direct- reading 9.inch meter (see illustration)-a remarkable tube $43.00 signal generator merchandiser ever offered at a price you can pay $37.50 MODEL 450 "TEST MASTER" Service men have called it more for the money than any all -service tube and set se-ealhz44v, tester on the market. Has new Simpson 3.way switch- y ing as described above: sockets for 4. 5, 6 and 7 -prong tubes. loctals and bantams. As set tester has 8 A.C. voltage ranges; S resistance rances: 5 milliamp ranges: 5 Decibel ranges. Your price only $39.75 11;71F1')LEt

Atomatic

VOLT-OH - MILLIAMMETER

PUSH BUTTON TYPE MODEL 1200 -F

Push- button switching by a new, simpler way makes the Model 1200 -F an entirely automatic Volt- Ohm -Milliammeter with maximum speed and minimum switching. GREEN Only one button need be pressed for any OCV range and test setting. Ranges: DC 0 -10- 50- 250 -500- 1000 at 25,000 ohms per volt. AC 0 -10 -50- 250 -500 -1000 at 1000 ohms per volt. DC Milliamperes 0- 1- 10 -50- 250. . . . 0 -50 DC Microamperes. . . . Resistance 0 -1000 Low Ohms, shunt type circuit; 0- 300,000 ohms; 0 -3 and 0 -30 Megohms, series type circuit. Self -contained batteries for all ranges. RED DOT Lifetime Guaranteed Instrument, rectifier type. Plug -in rectifier simplifies replacement in case of accidental damage. Metal case with rich brown suede enamel finish. $27.84 Panel with attractive three -tone finish. DEALER NET PRICE Dealer Net Price $27.84 Model 1200 -A . . Selector Switch Oper- ated . 2,000 Ohms per Volt DC . Model 1203-E . . Volt -Ohm -Milliammeter . . . Dealer Net Price Selector Switch Oper- $21.84 ated ... 25.000 Ohms Model 1200 -C . Selector Switch Oper- per Volt DC ... Volt - ated . 5,000 Ohms per Volt DC . Ohm- Milliammeter .. Volt- Ohm -Milliammeter . . . Dealer Net Dealer Net Price Price $22.84 $25.84

1160.....01111111111111110-t 6 0 É ' SENSITIVE 25.p0 0 °h's ULTRA 5p-1000 at 1000 allots 0 at VOLT- 0 voit.--o-io-50-250-000oltao'1 10h0 ox d obtain AL p efi v is Microamperes: METER per olt. Plug-in f°opoverload. OHM- per cas e Resistor nc 00 P in Current res. 20.0 AMMETER hm- replaced s. Milliamperes.hiampe Por MILLI Volt- cocus.ohm 1n$25,50 Ohms, M cone° 0-1-10-50-250-500g00, Low 2sancl 20 e - Milli- to Bing less c,i$21.CJ Milliammes: 0-10-50-250-500-1000 20,000 °h Dealer No age per and t 1000 ohms 50-25 ; of ablel 1600 -E for Panel amperes for higher Price Net Ohms with Pó °visons ealer Dealereler write for catalog external batteries on 250.000 complete line of test by . $14.00 equipment. Triplett also manufactures elec- readings and panel trical measuring instruments in more than 25 Molded case styles. Section loll Harmon Drive, Net Price

THE TRIPLETT ELECTRICAL INSTRUMENT COMPANY Bluffton, Ohio