t. r

ELECTRONIC USIC ON LIGHT B MS SEE PAGE 2

Re- Orienting the BC -625

Vest - Pocket Multítester Lamp Bulb 3051K3SC Modell-Tester w lpsotsTobe ,, "No Backlash Roll Chart

t With the addition of the new Simpson "No Backlash "* Roll Chart to the 1947 version of 4 our Model 305, this famous instrument becomes i beyond question the finest tube- tester on the market in its price range. Read the description of this new Roll Chart in the panel below. Model 305RC provides for filament voltages from .5 volts to and including 120 volts. It tests loctalc, single ended tubes, bantams, midgets, miniatures, bal- last tubes, gaseous , acorn tubes, Christmas tree bulbs, and all popular radio receiver tubes. Like other Simpson tube -testers, the Model 305RC incorporates 3 -way switching which makes it possible to test any tube regardless of its base connections or the internal connections of its elements. This method, the result of exhaustive research and expensive construc- tion, protects the Model 305RC against obsolesence to a degree not enjoyed by competitive testers. No adap- ters or special sockets are required. In addition to hav- ing a complete set of sockets for every tube now on the market, this tester has a spare socket, to provide for future tube developments. The Model 305RC has provision for testing pilot. lamps of various voltages as well as Christmas tree bulbs. It tests gaseous rectifiers of the OZ4 type -also tests ballast tubes direct in socket for burnouts and opens. Has neon bulb of proper sensitivity for check- ing shorts. This tube -tester is fused, and has the latest improved circuit. It provides for line adjustment from 6Exclu,jv. Features Make 100 to 130 volts, with smooth vernier control. This the Finest Roll Chart Ever Model 305RC is distinguished for its beautiful ex- Designed for Tube -Testers terior. It has a two -tone metal panel in red and black on a satin- finished background. Sockets and controls "No Backlash" feature of this Roll Chart auto- are symmetrically arranged for quick operation. The matically takes up all slack in the paper chart large, modern, fan -shaped instrument has and, by keeping it in constant tension, makes it an excep- impossible to turn the selector wheel without tionally long scale. It has "good" and "bad" English turning chart. Gives precision selection at all markings, also a percentage scale for matching and times. Also p is chart from tearing or get- comparing tubes. Cases, both portable and counter ting out of alignment. style, are made of strongly built hardwood, durably Gearing is such that only 6 turns of selector and beautifully finished. wheel will run the entire length of the 12' s ft. chart. Size, "xll "x6 ". Wt. 10 lbs. Easy to read. The clear Lucite window is just ll Shipping wt., 15 lbs. wide enough to show 2 tube settings, or both Dealer's net price, portable or counter model $59.50 settings on a multi -purpose tube. For 60 cycle 115 volt current only. Entire unit removable by taking out four screws. Just lift from receptacle to make new entries or For 220 volt or 60 cycle, add 7.50 install new chart. Standard Model 305, with hook -type speed chart 49.50 Chart ingeniously fastened fo rollers, affording easy replacement and constant alignment. Counter Model 305RC. Same instrument Rigid, lightweight construction. Gear driving mechanism in corp heavy -duty precision as portable model, but set in fine walnut brass gears and ports. finished hardwood case, with tilted, easy - a e, to -use panel. j-Finished hardwood cases are standard on port- able models. When these are not available, the instrument is housed in attractive simulated -leather covered case.

SIMPSON ELECTRIC COMPANY 5200.5218 W. Kinzie Street, Chicago 44, Illinois In Canada. Bach. Simpson, Ltd.. Landon, Ont. Building this A. M. SIGNAL GENERATOR gives you valuable experience. Provides amplitude modulated sig- nals for test and experiment pur- poses.

RADIO SERVICING pays good money for full time work. Many others made $5, $10 a week EXTRA fixing Radios in spare time. VETERANS You can get this training right in your own home under G. I. Bill. Mail coupon for full details.

with Big Kits

Radio Parts I Send You 'You build this SUPERHETERO- of DYNE CIRCUIT that brings in Do you want a good -pay job in Radio your local and distant stations. You get -or practical experience putting this own money- making Radio Shop ? Mail Coupon for set through fascinating testa. a FREE Sample Lesson and my FREE 64 -page book, "How to Be a Success in RADIO -Television, You build this Electronics." See how N.R.I. gives you MEASURING INSTRUMENT practical yourself early in the course -use it for practi- Radio experience at home -building, testing, re- cal Radio work neighborhood Radios to pick pairing Radios with BIG KITS OF PARTS I send! up EXTRA spare time mnmoney I Many Beginners Soon Make Good Extra Money In Spare Time While Learning D The day you enroll I start sending EXTRA MONEY JOB SHEETS. You LEARN Radio prin- SuC CESS i" R ciples from my easy -to- grasp, illustrated lessons - A PRACTICE what you learn with parts I send - at Home _. USE your knowledge to make EXTRA money fix- you ing neighbors' Radios in spare time while still learning! From here it's a short step to your own 1 dill full -time Radio Shop or a good Radio Job! Future for Trained Men is Bright in Radio, Television, Electronics Sample Lesson FREE probably easier to get started in Radio now Gives hints on Receiver Servic- It's ing, Locating Defects, Repair of than ever before because the Radio Repair business Loudspeaker, I. F. , is booming. Trained Radio Technicians also find Gang Tuner, Condenser, etc., 31 profitable opportunities in Police, Aviation, Ma- illustrations. Study it-keep it- rine Radio, Broadcasting, Radio Manufacturing, use it- without obligation! Mail Public Address work. Think of even greater oppor- Coupon Now for your copy! tunities as Television and Electronics become available to the public! Send for free books now! Find Out What N. R. I. Can Do For You CE/ 801/7 MPPIEEIEf ON FREE Mail Coupon for Sample Lesson and my 64 -page book. Read r the details about my Course. Read letters from men I trained. Mr. J. E. SMITH, President, Dept. 7DX telling what they are doing, earning. See how quickly, easily National Radio Institute, Washington 9, D. C. you can get started. No obligation! Just MAIL COUPON NOW in an envelope or it on a penny postal. J. E. Mall me FREE. without obligation. Sample Lesson and 64 -page paste Doak about how to win success in Radio and TelevisloElectronlca. Smith, President, Dept. 7DX, National Radio Institute, (No salesman will call. Please write plainly.) Pioneer Home Study Radio School. Washington 9, D. C. Age My Course Includes Training in Name Address TELEVISION * ELECTRONICS City Frequency Modulation APPROVED FOR TRAINING UNDER QI SILL RADIO -CRAFT for APRIL, 1947 SYLVAXIA XEWS RADIO SER`''I(.AE EI)I"hION

1[ R. Prepared by STLVANI:1 ELECTRIC PRODUCTS INC., Emporium, Pa. 1947

A PERFECT COMBINATION FOR A COMPLETE SERVICING JOB: SYLVANIA TUBES PLUS SYLVANIA TESTING EQUIPMENT

Now, in addition to selling the best in tubes, radio has been incorporated into these accurate, new in- servicemen can simplify their testing and trouble- struments. This Sylvania high -quality combina- shooting job with the latest and finest in testing tion - tubes plus testing units - means that you equipment. will be able to give methodical, dependable service The same high standard of manufacture that easily and economically. Remember to take ad- has always distinguished Sylvania Radio Tubes vantage of this combination now.

COUNTER TUBE TESTER POLY (MULTI- PURPOSEl METER OSCILLOSCOPE, TYPE 131 Here's the last word in counter testers - The Sylvania Poly (MULTI- PURPOSE) This instrument is especially useful in made by the men who have tested tubes Meter Model 134 provides, in a single rapid receiver alignment and trouble- by the million. Not only does it test every compact instrument, the means of making shooting. Controls are easily accessible. type of radio tube in common use today, a multitude of electrical measurements Hood shades face of 3 -inch cathode ray but provision has been made to permit and tests. Electrical values measured in- tube permitting use of instrument in quick adaptation to new tube types. clude audio, A.C. and R.F. voltages (up well- lighted room. The cathode ray tube The Sylvania Counter Tester Model 139 to 300 mc) ; D.C. voltages from 0.1 to is shock -mounted and shielded against 0.1 fields. is styled as carefully as it is engineered. 1,000; direct currents from milli- stray Its smart two-tone green panel, with its ampere to 10 amperes; resistances from Cabinet is steel construction, ventilated white dial markings, is in harmony with Y2 ohm to 1,000 megohms. with louvers, and finished in attractive the surroundings of the most progressive Instrument is oompactly built, at- pearl -gray baked enamel. Easily carried; radio store. Compact, Portable Tube tractively styled, includes all essential weighs only 18 pounds. Eight -foot power Tester Model 140 also available. accessories. cord provided for quick installation.

SEE YOUR SYLVANIA DISTRIBUTOR, or write to Radio Tube Division, Emporium, Pa. SYLVAN I A E LE C TRI C MAKERS OF RADIO TUBES; CATHODE RAY TUBES: ELECTRONIC DEVICES: FLUORESCENT LAMPS. FIXTURES, WIRING DEVICES: ELECTRIC LIGHT BULBS t RADIO -CRAFT for APRIL. IV47

new -tube characteristics

C -D's ANSWER TO

THE SERVICEMAN'S NEED PUBLISHED FOR SERVICEMEN-ABSOLUTELY FREE MAIL COUPON BELOW FOR MONEY- MAKING IDEAS

Yes Mr. Serviceman-"The " is the maga- How can I step up store traffic? Where can I sell zine that's published solely for you -to help you that spare signal generator? Eyery serviceman asks speed up servicing procedures -to help you build questions like these almost daily. "The Capacitor" up a profitable business. is the place to find the answers. It is the ideal magazine for servicemen because it "EASY READING- SIMPLIFIES CIRCUITS " - "I want to isn't cluttered up with lengthy how -to-build -it ar- thank you for mailing me copies of 'The Capacitor.' ticles for experimenters and gadgeteers. Instead its The special items are of particular interest because articles are down -to-earth, condensed, factual - of their easy reading and their simplification of dealing entirely with situations that face profes- otherwise complex circuits." A paragraph from one sional servicemen -and approaching these situa- of the many servicemen letters received every day, tions from the serviceman's viewpoint. THE TRADING POST -Free ads for servicemen! Put "The Capacitor" to work in your shop build- - Whether you have something to sell, want to buy ing your income -NOW. Don't wait. Mail coupon something -or if you're looking for a new helper TODAY -your free subscription will start im- -send the information to "The Capacitor" and it mediately. will be published in The Trading Post which ap- DO YOU ASK THESE OUESTIONST- What's wrong with pears in each month's issue. that new FM job that came in last week? Why does t -r -f set keep into that old breaking oscillation? GET THIS COUPON IN THE MAIL TODAY 1947 1 Cornell- Dubilier Electric Corporation Dept. RC -4 South Plainfield, New Jersey Please start my FREE subscription to "The Capacitor" P APER at once.

Nomo .. O VIA NOL

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RADIO -CRAFT for APRI(. 194' 3 TELEVISION Learn RA D 0 ELECTRONICS I'LL TRAIN YOU IN YOUR SPARE TIME AT HOME Pay fob or a GoodGo OWN! r'. Of p BUSINESS My Proven 2-Way Method Helps You Get HERE'S PROOF OF THE QUALITY OF into Radio N.R.T.I. TRAINING Find out about the money- making op- fascinating tests and experiments. You 1st, 2nd and 4th Prizes Won by portunities Radio offers you. Learn how learn the "whys and hows" of radio first H. R. T. I. Students In Open Contest you can qualify for a good -pay job or start hand, by doing. Thus, you learn more thor a business of your own without capital. oughly, faster! With over 250 students and graduates Send below coupon for my big FREE well as ex- MANY H.R.T.I. STUDENTS EARN MONEY from many Radio schools, as book, "Your Opportunities in Radio & perienced radio men, competing to find IN SPARE TIME WHILE LEARNING Television," which tells of radio's vast op- From the very start, through special the best Radio Technicians in Cuba ... and how HOLLYWOOD portunities "Spare Time Work Sheets," I show you 7 out of the first 10 prizes were won by RADIO &TELEVISION INSTITUTE H.R.T.I. Graduates! These PROVEN how to earn money in spare time by doing has been training men for success in good -pay radio jobs that abound in nearly RESULTS speak for themselves! You Radio for over 17 years, in over 40 differ- to with your future. every neighborhood. Many students earn can't afford gamble ent countries, through its proven 2 -WAY Choose the Radio School with the suc- $5, $10, and more a week while learning. METHOD -LESSONS PLUS HOME A mighty good way to lay the foundation cess record ... H.R.T.I. SHOP PRACTICE! WHAT WINNER OF FIRST PRIZE SAYS: for a future radio business of your own. "Your training methods are YOU PERFORM OVER 300 RADIO TESTS Now is the time to start preparing for so practical, and so clear, AND EXPERIMENTS YOUR career in this fast -growing indus- that no one should have dif- I send you 9 kits of radio parts with try. Take the first step -send coupon for 1 I found ficulty in learning. interesting, my big FREE Book today. everything so easy that it which you make hundreds of makes me fecl that anyone ,,fwho takes your course can YOU GET 9 KITS OF RADIO PARTS WITH WHICH be sure of success." Ç PERFORM OVER 300 EXPERIME S Luis ILLADA, Havana, Cuba YOU y Lc t: ou SECOND PRIZE WINNER SAYS: WHAT build this "I am very happy abcut my transformer success, but it is to you and coupled the H.R.T.I. staff that I owe audio stage. my success. I am deeply (Experi- grateful to H.R.T.I. for I ment o. have received all and 2Óo) MORE than you promised Left You when 1 enrolled." build this Above: You build this ALFREDO RODRIGUEZ, Oriente, Cuba Itlulti- ur- tuned radio stage, re. pose Shop generative detector and WHAT WINNER OF FOURTH PRIZE SAYS: "Pest Panel. audio . "The Ist, 2nd and 4th prizes were won by 5 Test (Experiment No. 329) H.R.T.I. students! This shows that H.R.T.I. instru- Left You build this A is one of the best schools! Over 250 radio tech- ments C. Power Supply. nicians competed. Among them were real ex- in onc. perts of established radio shops as well as stu- dents of nearly every known school. You will TOU LLAkrv from the enclosed newspaper, that the notice, build these and many other radio circuits 4th prize was won by me, and I owe it all to You and testers with the q kits I send you, to help your easy method of teaching." you leans faster, more thoroughly All kits GODFREDO REYES, Oriente, Cuhn r- -- become your property. 1 C. H. Mansfield, President, Dept. F -I BIG FREE BOO -K I Hollywood Radio & Television Institute 14, Calif. HOLLYWOOD IS A WORLD CENTER 810 West 6th St., Los Angeles Of radio broadcasting and manufacture -television- motion pic Send me your FREE book, "Your Opportunities in Radio, Tele- turc production. Thus, H.R.T.1. is in an excellent location to vision & Electronics" which explains your 2 -way training method. (No bring you modern, up-to-the-minute instruction. salesman will call) Before you decide on any course you owe it to your future to I find out about H.R.T.I. training. Read what graduates in 40 Name Age different countries say about this famous course. Just paste coupon I ca a postcard or send in envelope. No salesman will call Addres 1 City Zone- State I HOLLYWOOD RADIO & TELEVISION INSTITUTE 810 West 6th Street, Los Angeles 14, California DON'T PUT IT OFF, MAIL THIS COUPON AT ONCE!

4 R A D I O - C R A F T f,,, APRIL, 1947 Old -Timers say: "Keep up the good work!"

" PHOTOFACT Seasoned Servicemen get all FOLDERS are " PHOTOFACT FOLDERS but human. Thsy're vice far exceed best I've the data I ever saw in any ser- ever seen -and in the radio my IS years' experience seen everything Eve Invaluable Help from field. Keep up the days since the early Edmund H. Barnard, good work!" of radio." -Ben Davis, Gloucester, N. J. - lena Park, Texas. Ga- PHOTOFACT FOLDERS

"In 20 years of servicing radios, "Have diagrams so clear I've never seen never seen anything and easy to read, like it in 20 in every detail. so comp /ate Exclusive years of servicing. for How can you put A gift from heaven. so little?"- Hollis out se much dens " -Seun Zone. L. Hicklin, Cristobal, Radio & Sound Co., Canal P HOTOFACT more, Md. Balti- Features

COMPLETE Hundreds who have been in radio sample sets that are brought to Everything you need in one handy, unified servicing for ten years and more express our laboratories. They cover all the form -large schematics, pictorials keyed to complete satisfaction with PHOTOFACT latest radios, phonographs, record parts lists and adjustment data, complete FOLDERS. They say it's the best service changers, recorders, communications listings of parts values and replacements, they've ever found for saving time and systems and power as they alignment, stage gain, circuit voltage and money -and they ought to know. resistance analysis, coil resistances, dial cord hit the market. And they come to you stringing, disassembly instructions, record Whether you're an old -timer or in sets of 30 to 50 at only $1.50 per set. changer analysis and repair. newly established, you'll find PHOTO - This low cost includes membership in FACT FOLDERS indispensable ACCURATE -equal to the Howard W. Sams Institute, which another man in your shop for less than entitles you to free service on special All sets are actually taken apart and an- 9c per day. They will save you hours of problems affecting your business. alyzed by experts in the Sams laborato- time and effort: place at your finger- PHOTOFACT FOLDERS actually cost ries. Every part is measured, tested and tips the information quadruple -checked all you need to do you nothing because they pay for them- for accuracy. All data is a better job original. This means the data you get is right. -information compiled selves over and over again in time from a personal analysis of each re- saved. CURRENT Spend less time, do better work ceiver. at more profit. Order your PHOTOFACTS PHOTOFACT FOLDERS are issued twice PHOTOFACT FOLDERS are the result today. See your distributor, or use the monthly, as the new receivers come off pro- of actually examining and testing convenient coupon. duction lines. You don't have to wait for in- 'Trade Stark Reg. formation. As receiver changes are made, you get correction and addition sheets for your files. Your data is always up to the minute, EASY TO USE Set No. 1S Due March 10-Set No. 16 Due March 25 All diagrams are coded to numbered parts lists. Everything is positively identified for MAIL THIS ORDER FORM TO YOUR DISTRIBUTOR fast work. All folders know TODAY. If you do not are set up in uniform, 6 his name and address, send it directly to Howard W. Sams & Co., Inc., 2924 East -to- follow Washington Street, Indianapolis 6, Indiana, easy style: big type, big illustrations I and we will see that your nearest distributor gets it. In Cenada write to A. C. SIMMONDS & SONS, 301 King Street East, -no hunting, guessing or eye strain -no more Ontario. Canadian Price, Toronto, loss of time and temper. 1 $1.75. Send Set No.15 Send Set No.16 Send me Volume I (including Seta Nos.l to 10 inclusive) with De Luxe Binder, $18.39. (Circle one or more of following) Send Set No. 11, 12, 13, 14 ($1.50 set) HOWARD W. SAMS a CO., INC. (Circle one or more of following) Send Set No. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ($1.50 a set) My (check) (money order) (cash) for is enclosed. RADIO (If you send cash, be sure to use registered mail.) PLEASE PRINT PHOTOFACT SERVICE 1 Name In Canado -writ to A. C. SIMMONDS 6 SONS, 301 King Street Eon, Toronto, Ontario Address City Zone State

RADIO -CRAFT for APRIL, I 9 4 7 5 WIIG` you spin the dial of the latest type of telephone system - known as "common control switching" -you order into action a giant nervous system. It sends electrical impulses through an intricate maze of circuits: more than t o,000 contacts can be opened or closed in a single dial call. This system takes your order, remem- bers it, translates it into its own elec- trical language, throws out sensitive "feelers" to find a through route, plans how to make the connections, makes them, puts through the call -and, if the preferred paths are busy, finds an alter- nate route to take the call. The complex art of telephone - ing is brought to a high state of devel- opment at Bell Laboratories to serve the Bell System. Some day through "com- mon control switching" a dial in San Francisco may set up a connection through to a subscriber in New York.

Left: Backstage on your dial telephone call - some equipment in a typical "corn- mon control switching" office.

Bell Telephone Laboratories

EXPLORING AND INVENTING, DEVISING AND PERFECTING FOR CON. TINUED ECONOMIES AND IMPROVEMENTS IN TELEPHONE SERVICE RADIO -CRAFT for APRIL, 1947 NOWI An Amazing Opportunity to

I SEND YOU 8 BIG KITS OF RADIO PARTS ind m9 COMPLETE 6 TUBE RETERDDTNE RECEIVER

I TRAIN YOU RIGHT by PUTTING to, YOU TO WORK with REAL PROFESSIONAL EQUIPMENT!

LEAK" BUILD CIRCUITS! TEST! HOW 70 REPAIR! YOU DO OVER 175 INSTRUCTIVE EXPERIMENTS

YOU BUILD THIS USEFUL TES QU/AMFNT!

I give you a fine. moving. coil type Meter Instrument on Jewel Bearings - with parts for a complete Analy zer Circuit Continuity Test HERE'S THE EASIEST, MOST PRACTICAL WAY OF ALL TO PREPARE er. You learn how to cheek and correct Receiver defects FOR GOOD PAY in RADIO ELECTRONICS and TELEVISION! with professional accuracy and speed. I train your mind by putting you to work with your A BUSINESS OF YOUR OWN ... OR A GOOD RADIO JOB hands on a big 6 -Tube Superheterodyne Receiver. You'll End out how to get and do neighborhood Soldering. wiring. connect. And, believe me, when you get busy with real Radio repair jobs for nice profits and rich experi- Gig Radio parts .. . build- ing circuits can't beat Rodio Parts - 8 big Kits of them you really ence while learning. This sort of work can easily - you - this method of learning. LEARN Rodio and learn it RIGHT! You get the pave the way for a Rodio Service business of your When you construct this practical stuff you need to with Sprayberry Training, you're not and Filter, Resis. be useful in Radio, and tot. and Condenser Tester, limiButted. You con swing into that's whet it takes to make money. You don't any one of the swiftly etc.. you get a really peat expanding branches of Radio - heal slant on Radio. have to worry about what to do with these 8 Kits Electronics INCLUDING Rodio, of Parts. Step by step, I you show how to build Television, FM, , Indus- -1 circuits, test, experiment, trouble- shoot. And you trial Electronics. You'l, get valus lie et Be wise! periente and practice don't need any previous experience. The Spray - Decide now to become building this Signal and multi- berry Course starts right at the beginning of a fully qualified Generator Tester. RADIO - purpose Radio! You can't get lost! Simplified lessons, ELECTRONI- Makes s breeze out CIAN. Get full details of fixing Radios and coupled with real "Shop" practice, makes every about my Training at you don't have to subject plain and easy to understand and remember. spend morey en once! Mail coupon be- outside. ready - Soon you begin Sprayberry after Training, I'll low for my 2 big FREE made equipment. sand you my sensational BUSINESS BUILDERS. Books.

SPRAYBERRY ACADEMY OF RADIO CET THESE vAC UABE E F. L. Sprayberry, President, Room 2047, Pueblo, Colorado I Please rush my FREE copies of "How to MAKE MONEY in RADIO, I ELECTRONICS and TELEVISION," and "HOW to READ RADIO I FREE BOONS I DIAGRAMS and SYMBOLS." "How to Read Radio Diagrams and Symbols" Here's a valuable and wonderfully complete new book which explains in simple English how to read and under- Name Age I stand any Rodio Set Diagram. Includes translation of all Address Radio symbols. Sand for this volume at once. Its (reel .... I Along with it, I will send you another Big free City book describing in detail my Rodio- I State I Electronic Training. (Moil in envelope or poste on penny postcard) I= fa =1111=1=11=11111=11111111=111=111111

RADIO -CRAF' APRIL Iga 7 C err u Ean AddYour Income with a SOLDERING IRON!

S, it's a fact that you may not have realized ... but every minute your soldering. iron is busy, you are busy making money. And you can make even more money if you will suggest to your customers a complete "FIND AND FIX" treatment for sets. A complete "FIND AND FIX" reveals parts about ready to go as well as those that are shot, saves your customers extra trips, prevents the embarrassment of parts going sour right after leaving your shop. IRC's Volume Control Cabinet, Assortment Kits and Basic Kit cut down unnecessary trips to your dis- tributor for parts, give you more time for soldering ... for making your time pay. Order from your local IRC Distributor today. International Resistance Company, 401 N. Broad Street, Philadelphia 8, Pennsylvania. In Canada: International Resistance Company, Ltd., Toronto, Licensee. rouR

The IRC Volume Control Kit 18 All -purpose controls, 6 and 5 special shafts in an attractive factory- packed steel cabinet.*

The 3 IRC Balanced Resistor Assort- ments in Resist -O- Cabinets` No. 1. 59 assorted insulated composition and power wound resistors, 'T!/tRl ! including adjustable types. The IRC Basic Kit 471 "basic' resistors in a wide variety No. 2. 100 of the most used ranges in 'h of types and ranges, plus 6 additional t watt insulated composition and bands for adjustable types. insuloted wire wound resistors. All metal cabinet' _ No. 3. 83 top quality resistors in the 'Cabinets are furnished at no charge, not 1 -west range. sold separately. ;

INTERNATIONAy CEANCE COMPANY 1 Wherever The Circuit Says II Copyright, 1947, 1nnMeetieeel Resistance Ceweeny 4 RADIO -CRAFT for APRIL 1947 ZAleci IN YOUR OWN HOME 44442

RA I i ELECTRONICS P2QaúQe "HOME- TESTED" Nore "A -B -C" ZZ

WITH THE HELP OF A EIGHT Big Kits of Actual "Learn -by- Doing" Radio O y Parts and Assemblies with which you make 133 fascinat- ing SHOP METHOD EXPERIMENTS in your own home! Imagine building 7 different Radio Receivers that operate!

B A 16 mm Home Movie Projector and Twelve Reels of "Learn -by- Seeing" Home Movie Films ... for picture= NO PREVIOUS RADIO 501":,4 clear, fast understanding of Radio Fundamentals! OR ELECTRICAL 11. Re tobe C Modern, well- illustrated, Loose -leaf Les- EXPERIENCE NECESSARY ,0 et sons, prepared in clear, simple, understand- DeForest's Training, Inc. provides .j, ec every major home study aid to help you one3Averc`I able language ... to guide you throughout learn Radio-Electronics rapidly and thor- te e oughly ... to give you the experience and et your training! confidence needed for a responsible, Good - oa°O- ce°J Rece°J Pay Job, or to Start a Business of Your Own! R 1Re e a Here is a REAL opportunity field for YOU 4104 ayre THEN GET THE HELP OF . when you are a trained Radio- Electronics Di°o n t man! Just think of the tremendously exciting Sh° tbetet OUR EFFECTIVE future ahead of FM Radio, Aviation and pa `Rece ne Broadcast Radio, Sound Motion Picture Equip- EMPLOYMENT ment, Servicing and Sales of Radio Equipment, 5' Eve etc. Put yourself in this picture ... See how you 0011 e SERVICE can benefit from a PRACTICAL training in this SSoper0 fascinating work! Think, too, of the coming possi- Motio SGO bilities ahead of Radar, Facsimile and Television. 5 t10h S Send TODAY for the interesting, opportunity - 1 vG, revealing book, "Victory for You!' See how others Rprobably no more talented or ambitious than you, o1NNS clAG ave advanced in earning power after this training . . how YOU can do it too! Mail the coupon NOW! VETERANS!

Big things are hu;;. - IC inget DeForest's I ra.::- F PS po`XPa` YOU USE ing. Inc. for nNarans! See how you can prop r, " 16 MM "LEARN -BY- SEEING" yourself WIT " MOVIE COST for a COQ or a !MINE-, PROJECTOR MOVIES YOUR OWN in the cot E. B. DEVRY, President 1 Radio -Electronic op- DeFOREST'S TRAINING, INC. portunity field. 253541 North Ashland Ave., Dept. RC -D4 DEFOREST'S TRAINING, INC. INCLUDES Chicago 14, Illinois, U.S.A. L. INSTRUCTION IN MOTION PICTURE "VICTORY FOR YOU!" BOOK, showing how SOUND EQUIPMENT, FM RADIO AND Send FREE I may' TELEVISION ... RESIDENTIAL TRAIN- make my start in Radio Electronics. ING IN OUR MODERN CHICAGO LAB- ORATORIES ALSO AVAILABLE -ASK US Name Age FOR INFORMATION! Address Apt City Zone -State If under 16, check here If a discharged Veteran of for special information. World War II, check here. I RADIO -CRAFT for APRIL, 1947 9 APRIL 1947 Editorial: Superadlo.. by Hugo Gernsback 17 RADIO Radio -Electronics Monthly Review 18, 19 New! Crystron Lapel Radio by Mohammed Ulysses Fips, I.R.E., A.I.E.E. 24 CRAFT Electronics AND POPULAR ELECTRONICS I',corporat,ne Antenna Principles, Part Directional Arrays for 300 and by Jordan McQuay 20 V- Mc Higher. WAVE CRAFT TELEVISION NEWS Television for Today, Part XI- Electromagnetic and Electrostatic Deflection Systems RADIO (SION by Milton S. Kiver 37

Heat -Operated "Radar" 46 -HUGO GERNSBACK Editor- '-Chiel

Amateur Rodio FRED SHUNAMAN Managing Editor The Postwar Radios -Reviewing the Hallicrafters S-40 28 M. HARVEY GERNSBACK BC -625 on 144 Mc by L. W. May, Jr., W5AJG 35 Consulting Editor

Servicing ROBERT F. SCOTT, W2PWG Technical Editor Lamp Bulb Resistors by John B. Perchman 23 I. Radio Data Sheet 345 (Admiral Model 6RT44-7B1 40 QUEEN, W2OUX Editorial Associate Neglected Servicemen by E. H. Ehle 44 ELMER FULLER Sound Shortwave Editor ANGIE PASCALE New "Prismatone" Organ 22 Production Manager A Small Recording Studio, Part II -The Technique of Making a Phonograph Record by J. C. Hoadley 34 G. ALIQUO Circulation Manager Multi- Station Intercoms, Part II- Master- Remote Systems and Circuits. by Richard H. Dorf 33 JOHN J. LAMSON Test Instruments Advertising Director ALFRED Vest -Pocket A.C.-D.C. Volt- Ohm -Milliammeter by William Lyon 26 STERN Promotion Manager New Ideas in a V.T. Voltmeter by C. F. Van L. Weiland 30 On THE COVER: Construction

De Luxe Phono Oscillator by W. G. Eslick 42

Departments

Transatlantic News by Major Ralph Hallows 39 Available Radio -Electronic Literature 47

The Question Box 48

New Radio -Electronic Devices 50

World -Wide Station List Edited by Elmer R. Fuller 52

Radio -Electronic Circuits 54 The "Prismatone," an elec- Try This One 56 tronic musical instrument

which operates with light New Radio -Electronic Patents 72 beams and photocell wands. Chrom(atorbe by Alex Schomburg Communications 76 from photo by W. !flea. Book Reviews 79

RADCRAFT PUBLICATIONS. INC. Hugo Gernsback, President; M. Harvey Gernsback, Vice President; G. Aliquo, Secretary

Contents Copyright, 1947, by Radcraft Publications, Inc. Text and illustrations must not be reproduced without permission of Copyright owners. RADCRAFT PUBLICATIONS, INC. PUBLICATION OFFICE 29 Worthington Street, Springfield 3, Mass. EDITORIAL AND ADVERTISING OFFICES 25 West Broadway, New York 7, N. Y. Telephone REctor 2 -9690. BRANCH ADVERTISING OFFICES: Chicago: 308 W. Washington Street, Suite 1413, Chicago 6, III. Tel. Randolph 7363. Cleveland: Burdette Phillips, Manager, 405 Erie Bldg., Cleveland, Ohio. Tel. Main 9645. Detroit: Frank Holstein, Manager, 307 -8 Boulevard Bldg., Detroit, Mich. Los Angeles: Ralph W. Harker. Manager, 606 South Hill St., Los Angeles 14, Calif. Tel. Tucker 1793. San Francisco: Ralph W. Harker, Manager, 582 Market St., Sen Francisco 4, Calif. Tel. Garfield 2481. RADIO -CRAFT, April, 1947, Volume XVIII, No. 7. Published Monthly on 28th of month preceding date of issue. Allow one month for change of address. When ordering a change, please furnish an address stencil impression from a recent wrapper. All communications about subscriptions should be add d to the Circulation Manager, Radio- Craft, 25 West Broadway, New York 7, N. Y. SUBSCRIPTION RATES: United States and possessions, Mexico, Central and South American countries, $2.50 a year; $4.00 for two years; $6.00 for three years. Canada, 3.00 a year; $5.00 for two years; $7.50 for three years. All other foreign countries, $3.25 a year; $5.50 for two years. $8.25 for three years. Special rates for members of the Armed Forces in U.S., or those addressed by A.P.O. or F.P.O. mail, $2.00. Entered at Post Office, Springfield, Mass., as second -class matter under the Act of March 3, 1879. FOREIGN AGENTS: Greet Britain: Atlas Publishing and Distributing Co., Ltd., 18 Bride Lane, Fleet St., London E.C.4. Australia: McGill's Agency 179 Elizabeth Street. Melbourne. France: Brentano's, 37 Avenue de l'Opera, Paris 2e. Holland: Technisch Bureau Van Baerle Bemelmans & Co.. Heemsteedscl(e Dreef 124, Neemstede. Greece: International Book & News Agency, 17 Amerikis Street, Athens. So. Africa: Central News Agency, Ltd., 369 Smith Street, Durban, Natal. Universal Book Agency, 70 Harrison Street, Johannesburg. Middle East: Steimafzky Middle East Agency, Jaffe Road, Jerusalem. India: Magazines Distributors, 5 Bombay Mutual Annexe, Gunbow Street, Fort, Bombay I. 10 Grasp the NEW OPPORTUNITIES iñ

Modern Radio -FM Broadcast and Reception - Television - Industrial Electronics; Power, Control, Communications - new equipment and methods demand new technical ability and experience. Keep up to date with the latest.

MODERN RADIO Shop Method Home Training EQUIPMENT FOR YOU By a Real Established Resident School TO USE AND KEEP with its own FM Studios, Shops and Laboratories. TRAIN WITH ADVANCED much r than ever before! TECHNIQUE Radio Is expanding with far- reach- The good Jobs In Radio Electronics ing improvements in reception. No one now go to the men who are equipped t0 knows yet how great the Television handle them. It takes training and ex- market will be. Eleotronics will touch perience. National Schools. one of the almost every walk of life -In industry oldest and largest trade schools In the and in the home. country, makes it possible for you to TURN YOUR INTEREST IN get this training right in your own RADIO INTO A CAREER THAT home IN YOUR SPARE TIME. WILL ASSURE YOU SUCCESS AND National maintains modern resident SECURITY. training Studios, Shops and Labora- tories where instructors and engineers FIND OUT WHAT NATIONAL. are working constantly to Improve TRAINING CAN DO FOR YOU training methods. SHOP METHOD Where do you stand today in mod- HOME TRAINING is a logical non- ern industrial progresal What does the Mon of this practical system. future hold for you? You owe it to A FREE lesson that shows you how yourself to investigate this opportu- practical and systematic this new train- nity. With National Training YOU ing method is will be sent you without GET AHEAD FAST -you may step The very essence of National Shop Method obligation. You may keep and use this into good position or start a busi- Home Training is EXPERIENCE. You get lesson to arose to yourself just how ness of your omis. with little sandal. actual experience by working with modern practical National Training really is. even before you Complete your National Radio and Electronic equipment-building Get one of the many NEW JOBS Course. many types of circuits. You may build a that demand new techniques and meth- Fit yourself for a career of inde- fine, distance ET- ods in Modern Radio. Oct your share of pendence, good earnings. success and long MODERN SUPERH that servicing signal the NEW BUSINESS security in one of the fastest growing ERODYNE, generator. miniature the new seta and equipment demands. fields in industry. For full information, radio transmitter, audio oscillator, etc. - Experts agree that Radio, Television Just send your name and address on the many other standard actual operating and Electronics present opportunities coupon and mail it TODAY. Pieces of equipment -conduct cathode ray and other experiments. This practical work advances with your training -YOU LEARN APPROVED FOR Get This Book BY DOING! TRAINING UNDER Cl BILL FREE Thia big book presents the tacts about the field of Elec- tronics and your opportunitles in it together with toll Infor- mation about the advanced Na- See What National Training tional Training. Read it and make up your own mind that National Training will equip Has Done For These Men you for a great future. No salesman will call on you Irons National. The book is FREE National Shop Method Romo t'IIRo rd Hannah, with your sample lesson. Clip Training wins good Jobs. 1n- Portage La Prai- and mail the coupon TODAY! dependence and security. Take rie. Manitoba. the word of National men who Canada. writes: have established records in "My training has their favorite Radio, Televi- brought results as sion. or other branches of Pm In line for NATIONAL SCHOOLS Elu:trealca another raise thanks to Na- los ANGELES i7, CALIFORNIA EST 1905 tional's encouragement and From O. K. Trey, thorough training." MAIL FOR ACTION Washington, OPPORTUNITY COUPON QUICK D. C., comes this Joseph Michel, National endorsement: I Schools. Dept. 4 -RC (Mall In envelope or paste Jr., Granite City. 4000 Figueroa believe National Illinois. writes: South Street. Los Angeles 37. California On penow poet card) offers the beet I am enthused counts to be had with National MeH me FREE the two books mentioned In your ad including a sample lesson of your course. . Keep up the good work." training. I am I undentaod no salesman will call on me. now esrning $225 Iere's s state- as a mortis radio operator NAME ment from R. B. and technician and $20 a week AGE Yright. Black - more :n my shop at lAme. oot.Idaho: "Due ADDRESS o my training at National I was Read what other enthusiastic selected to in- students have written about CITY STATI' trust to the laboratory work National Training in the big Inr!nde Your zona of of Navy and Marines." 90 page book we will send you. 1 I: Check here if veteran of letherWorld War It L. i RADIO -CRAFT for APRII, 1947 DP 12 NEW U.S. !! Famous Navy NAVY "COMMUNICATIONS High Power MODEL Direction Finder RAK -1 SHIP AT DISPOSAL PRICES! The tP.tS is a Navy direction finder. made by RCA with frequency rang* oI RECEIVER VALUES o01500 ke. The input voltage 1s (115v/ tfil I. The tune Ilneup Is 3.8cß; 4.600; 2.70: 1.6AF6; 1.1523. This unit. Is $69.95 nipped with loop output function une, 15 k.. to 0 hr. 0 -tube receiveriver flexible transmission line, Input trans. AVC-Iland former. der* bearings. cable drums, Ftuwiitigdwith lla Vernier operating pedestal. hand wheel. azimuth dial -Voltage ngula;cd power suPP1Y. PARTS SPECIAL ITEMS loop antenna assembly. and mop with three tubes, for 00 cycle. 115 volts. o Can be battery Visors r ICt'.tel. Tills nit n bar for any operated. Cmplete with AND EQUIPMENT for inch 'acmes $ .75 n,.h, oing VezoI u $195.00 73 Iba.. tube. rube shields for 2AP1 .98 and lostI ñ ibox book. Magnetrons!! Type 2382 3roadcast band moth-hottest tuning units, (JAN.) just released. The Inductile or capacitiva types $1.49 2J32 is designed for 10 CW -3 RACK Test Set EE65 cm. operation. Rated at Helmholz Phase Shifting Coils $2.25 Made by Conn. T & E Corp. 800 kw peak Mushroom rubber earphone mullions for RECEIVER lightweight acts. 2 .89 $29.50 pulse power. pr This unit le used for checking and man,. Complete in- Mental sockets with 1% ft. leads for fining field telephone systems Ly e.t. log for ell types of failure. In the lines, formation 3BP1 and :.Cl'1 $1.20 such a opens. short., ground.. r supplied. with other lines, capacity between 1 l i iee.. Oscilloscope chassis, completely punched. insh latin, resistance. a d any of the Listed at or use with a 2 inch so kens other faults possible in a u tube. Octal phone system. $2u0. O r ncluded 15 011'x8" $1.50 Price $25.50 Army comvlct Microwave Signal Generator -2700 to -Navy Type Head- 2J38 Magnetron, 8240 me., 1000 næ. Regulated power supply - ss'y feedv frequency from X1 1000 Ice. to with magnet $37.50 115V /60e. Contains output meter. Made In. 100 ice. Uses 7 iti e, 0,w-sting fre phones Type HS23 by Western Electric. Value twenty Is determined by xtal. With 2 toi. 3J31's just received. One cm. magne- $400. $75.00 nu Leather covered headband. detachable b. v Liable. to . xluua.u nigh weight h -ads et with tron listed at $95. OUR PRICE $20.00 Microphone element T -30 -K for throat 4Prlced new 9 ithh spare tue 2.000, ohm DCR. 8000 Impedance, with Magnet. for magnetrons, each $1'.0 mike selling 2 for .50 and one set of coils (9.4.16 me.) rev. cord P1.55. 715 -B Pulse Power Tube $9.50 $21.50 New t,, carton. 32.50 Microphone unit MC -419 for lip micro- i Nara art tolls 5.4.10 mc. 1 5.d -In grand condition 1.50 oscillator tubes 21(25/ phone .98 723ab designed for 8 cm operation. 140 mmf split stator variable midget HI- VOLTAGE TRANS- TUBE SPECIALS New, with complete data. Listed at condenser $1.49 Tube AL" Your $38.00 $7.75 reps Cost Silver button mica condensers, 175 -180- FORMERS pl $3 75 Duplexer using 1B24 for 8 cm $10.00 3RP1 I5.00 3.95 724B ATR Tubes, used in duplexera, 185 mmf. each .05 3200 volts. AC 150 11.A. 115 volt. pri- :,tIi 27.00 2.99 each $1.50 Lots of 100 $4.50 mary. 60 cycles. Designed for half wave 5111. 20.00 4.95 Silver button operation with 150 M.A. output each. 5CP 4 20.00 7.95 30 me oscillator-amplifier with 2 mica condensers: 400 and two transformer. hooked up with sec- S PI 5.00 .95 6AC7's. Uses 723ab, Wave guide in- 560 min. each .10 ondaries and in Derai- 'CP4 48.00 6.00 In series primaries SFP74 35.00 4.85 ors of 100 1 put. xtal detector. With 6AC7's $10.00 $9.50 1 will give 3.00.5 volts. output at 300 5F 32.00 3.95 11.A. from wave These With 6AC7's and 728ab $16.50 Feed -through glus insulator 7%° lonne. full rectifier. 48.00 8.98 170396), for use to.uervalhe, continuous commerel,i 2.80 1.35 Beads ID- Beehive external section $1.10 rating. $7.25 ß78772A 7.50 2.45 with UHF and Micro -Wave Equip .le lerson v ,OSA 22.50 6.75 ment sealed Block crackle finished cabinet for relay Power Transformen 115 60ey/ a IBWE 85.00 40.00 (List $3.00). In separate acct mounting 19' W Z 25' H z 15' 1110 sou -85 Ma./6.3v7.3A/5v-2A/6.3v- 301 555.00 85.00 containers .95 U stillt hinged door in back $6.00 ,A $3.59 304TH 8.00 Power supply transformer. Stade by Sub Socket. for SCP1, bBPL. 3111.1, 70 c. Pri. 115/60 cps Sec. 1:750vet. 1135: Pao 0.95 r... 3 CM wave guide section: 2:8.3vet -5a: See. 8:5v -3a. 2500T% Silver Plated Directional Couplers epenally priced at $5.95 Hi -Volt Oil Condenser with a 20 DB drop with: Ohmite Wire -Wound CHOKES .I3-.15mf001111v1r GE".. A. Wave Guide. 90' bend 15 " $4.05 Rheostat 12 try -12 by @ 150 ma., 15 amp .1..1rernii 7óó:ñ céN.so [sing, each price $3.35 B. 16° 4iooia i6 áó3ó : i.7s bend in wave guide 16" $4.40 Mood H 250 Ohms 25 Watt $ .98 12 Iry @ 165 nia 200 ohms DCR .15-.15 mf S000vc C. 80° bend in wave guide 10" Model H 125 Ohms 25 Watt .98 made by Thordarson. Price 2.00 Sprague Vitamin O 5.25 long 11,.r el .1 1800 Ohms 50 Watt 1.25 59 by @ 100 ma 850 ohms DCR G.E.z.P $8.95 Mn', I K 3000 Ohms made by Jefferson. Price 2.00 s3áM400óv 5.23 100 Watt -., 1.98 G.E. Pyranol Lió23E49 D. 90° bend in wave guide 15" 51o'el t. 250 Ohms 150 Watt 2.25 2.6 by @ 800 ma stud and terminals Model N ..t bottom made by G. E 5.95 List 537 4.75 long also 90° bend in 22 Ohms 300 Watt 3.09 C.13 TC b 1mfs 3000v. List 530 4.50 loud P 1200 Ohms 225 Watt 2.75 AUDIO . MODU- G.E. 14E191 .Imf 10000v. List 537 6.75 coupler $5.50 Capacitor 2. LATORS. ETC. 'yïmm3 -tó=ml. IDeitad. eon$4 E. T Section with choke ter- MiOul tins :far: typical for 211', (rted made by GE 90v. 60c. 00 minations $5.00 I.F. XTAL FILTER I 1503V $1.35 Modulation xfmr: pr. 811's to 813 5.00 - NEW POWER G. 160° bend with 90° twist 3i4" I Crystal filter for Re.312. Athgo output transformer Split pd SUPPLY for radius with pressurizing RC -342. Resonant at 470 kc. 1500 OHMS each side. Secondary LM -18 freq. nipple and coax coupler $3.95 l'rystal included. impedance 85 ohms rentetapped -6:1 ratio, 100 -watts output 5.50 meter. Output: H. 2jf= foot 3 cm wave guide $6.95 Line to Voice coil transformer. PH 290 y @ 20 choke to cover fitting $4.95 000 ohms. Sec. 8 ohms. 1200 Test ma; 18 v Q soli 1.45 600 ma. J. 6 foot 8 cm wave guide sec- Input: tion. per foot $1.95 105 -125 v. &$ 60 cps; 260 K. Scm.$4.00 Slotted Dipole Antenna - - ma; 27.6 W. 90° bend in wave guide 15" $5.00 SONAR SOUND DETECTION type 84 rectifier tube; shock L. Choke flange for 3 cm. 1 "x mounted. Complete with input W. 2 for $1.45 UNIT and output (plugs) $14.75 M. 10 cm. Wave guide, per ft $2.00 tubs included 16 Ideal for detecting underwater monde, such se fish swim ft. lengths. ndng in od iuls, within a 15 mile area. Using a Rochelle Send for List salt crystal. which 1s about 1000 times more sensitive Oil Filled Condensers Omit quartz. as the active unit the sound is transmitted 1 mf 300 vde 30.25 up a 00 ft. length of cable. It is completely eneloeed In a 2 mf 300 vde .30 RELAYS solid rubber sheath. This label detector was originally 4 mf 300 ve .35 tused in harbor defame. to an audio amplifier, 4 tot 400 velC .55 A. SPDT Leach 1353 Coupled ; 1f 00 vdc 1.15 4 115V /60 cps. coin his can -be found to have many valuable 2 t 550 vac .30 applications. Ask for SD -1 $695 vdc .25 silver contact 10 A. °rot ñúñ Rating. This relay Is i 000 vdc .35 actually DPDT with f 0 0 d .40 a Bridge between the I mf 000 vde pyr .65 two poles. Easily con- tor vened to DPDT. RA -58 -A HI- VOLTAGE POWER SUPPLY BIÌOO velc ppymT .95 tir nit' á00 vde 1.49 eps $1.25 Ideal for breakdown insolation testing, as " mf BOO vde 1.75 of e poser fore tiapsmiter. This t 1 mf 1000 vele 0.85 C. SPDT contacts; coil rated ..01lee continuously varlahle voltages between 500 A 115r/60 $1.39 and 15.000 volta DC at 35 ma. voltage Double I nhf 1`1n0 ad< 1.05 two 71)30 rectifiers and two 1 mf r D. SPST Latching relay made by circuit using I .30 denser, ta employed. RM.9 ripple voltage n i Korman. Make coil 115v /60c; áó°o°evaio0o !p ower RAT'1 mum Is (I... THIS UNIT OPI I n4 vde DCR 1500 ohms. Break coil 115 FROM 115 v /ó0c. Variable voltage ln ehtaine., by 15n0 l.fn I nlf 2000 vde 1.20 vde 1D ma; DCR 5000 duns 2.95 of n Variar in circuit of h ntearis the priman' rie i o,f 2300 vde 1.20 E. DPST Telephone type; 2 p. 1 cl; voltage (rattan-wine, :I,,' Is 21"x17 iF "x210' Dv Elect. Cond. 1 open cons. rating 5a at 50v. Net ,'eight 314 lbs. This unit sells for nit $ 1 1 200 d; 1.95 coil rating 3.5 Ina tat 12K ohms), the low price of 6 . In nut :lu mr 2.25 11100 vac 1.05 F. DPDT Steatite Insulated 10 amp silvered contacts, made by Leach 1.95 All merchandise guaranteed. Mail orders promptly filled. All prices F.O.B. G. SPOT Struthers Donn sensitive "2 FOR A DOLLAR" New York City. Send Money Order or Check. Shipping charges sent C.O.D. keying relay. 5 MA -De Coll. 110v/ 80 cycles-2 Amp contacts 1.49 SPECIALS SEND FORVLYEN Modulation Xformer 807 10 pr. 807's lop TECHNICAL MANUALS Nformer Single Button to Grid 20:1. COMMUNICATIONS BC 191 (same as 375) 50 %odio Coupling xformer 600 ohms CT SCR 193 (combines 312) no. 4,000, 250 choke 2 Hy. @ 160 ma. RCVR and 191 Txmtr) 50 SCR 528 50 EQUIPMENT CO. SCR 508 50 2 FOR A DOLLAR SCR 538 50 -C New York City 7, N.Y. 7A -1 Landing equipments 50 131 Liberty St., WH 4 -7658,

12 RADIO -CRAFT for APRIL, 1947 What does it take to WARE you up?

Present -day expansion of the radio -electronics industry Is almost UNBELIEVABLE. The tremendous growth of the art is so rapid and in so many directions that already the demand for TECHNICALLY QUALIFIED radiomen has created a condition wherein there are many MORE GOOD JOBS than there are capable men to fill them.

By the end of 1947 the total number of broadcasting stations (AM, FM acid Television) will have almost tripled since shortly before the war. Airlines and airports are rapidly installing new radio communications and radar equipment. Every major railroad has adopted radio communications, as have large trucking and taxicab com- panies. Manufacturing is at an all - time high as millions of home re- ceivers, broadcasting equipment, etc., are produced. Television receivers are now in regular production. All of this means that OPPOR- TUNITY IS HERE ... Note! Every page in this magazine could be filled with such astounding facts con- cerning career opportunities available to trained radiomen. The point is, what are you going to do about it? Just figure out for yourself how many good jobs are waiting to be filled. You can't say, "I don't need more training." EVERY radioman needs to increase his technical knowledge if he l wants to keep ahead of the competi- tion that is_bound to come ... if he wants to go after - and GET - the better jobs that offer good money and personal security. If you have a commonplace job. If you have the ambition to hold a position of greater responsibility with higher pay ... then a CREI spare time pro- gram for self -improvement will help you accomplish your ambition at this opportune time. It costs you nothing to read the interesting facts. Write today for the list of CREI radio - engineering courses.

4

IJ you bave had professional or amateur radio experience and went to make more money, let us Prove so you we have the CAPITOL RADIO ENGINEERING INSTITUTE training you need to qualify for a better U I radio job. To bells 16t13 & Park Road, N. W., Dept. RC -I. Washington 10. D. C. us intelligently answer our inquiry - PLEASE STATE BRIEFLY YOUR BACKGROUND OF EXPERIENCE, ._ Gentlemen: Please send me your free booklet. "CREI training EDUCATION AND PRESENT POSITION. for your better job in RADIOELECTRONICS ", together with full details of your home study training. I am attaching a brief resume of my experience, education and present position. VETERANS! CREI CHECK TRAINING AVAILABLE UNDER THE "G. I." BILL! Q PRACTICAL RADIO ENGINEERING COURSE Q PRACTICAL TELEVISION ENGINEERING Capitol Radio Engineering Institute NAME._..._ An Accredited Technical Institute STREET__ DEPT RC -4, I CITY 16th and Park Road, N. W., Washington 10, D. C. ZONE STATE L I am entitled to training under the G.I. Bill. elm YORK 17): 170 BROADWAY SAN FRANCISCO Ill: 760 MARKET ST. -J RADIO -CRAFT for APRIL, 1947 13 ERSHfI BETTER BARGAINS BIGGER BU a!! o.tdvr, Mu« 7. 0.13. itiln.} Ddiroif 4200

TRIANSM 4110;1,2';s,l;J /,- $11 'amr°mOer TTER N1 ón.n ay ,orna, anr6ar 65 6gn w;d.f refeg E tiad CE l N BC 575. ARFrox.hokes minw° rhel 714 VER / , . yriden. " c$5or°,1nt-Jj f4 MC M!"F otd. 1 KW . No poN. Ca1. MODULATION I $ 9§ BUY NOW S? *- AND SAVE CONDENSERS TRANSFORMER 14 FILAMENT RCA modulation hansformer is conservatively rated at 550 Walt audio to modulate TRANSFORMERS Cal. Cop. Working Your that new KW rig. Thordarson 6.3 V-4 amps., No. MFD. Volts Cost Really rugged construction with protective flashover gaps, which are adjustable. 6.3 V-4.5 amps., 9.7 V-.5 mounted on a "M colox" terminal board. The laminations amp., pd. 110 V AC 25 or C110 1 5000 Oil $395 Terminals and gaps are $1.95 C111 3 4000 011 $4.95 that mot. up this transformer a of high audio quality and are extremely thin, 60 cy.--Cat. No. FT-11 the core to or talk." C112 1 1000 011 440 making it impossible for "chatter Thordarsnn psi. 110 V 60

Thordarson B HY ISOM choke, Cal. No FC-201 95c +IW 39c Da. for $100 Thordarson 8 HY 175M choke, Cot. $1.49 No. FC-201 BUTTERFLY CONDENSERS Thordarson 12 HY 25M choke, Cal. Ideal for high fre- No. FC-203 39c quency work.

8 choke, Cot Type A -fregaoncy Thordarson HY 350M 0-1 Westinghouse meter, 0.1 No. FC-204 Westinghouse meter, range 76 to 300 MA movement, 2' round RF amps, 2' round case, to be internal thermocouple. in megacycles cose, cale calibrated W Electric meter, used with 955 TH OR DA R SON In. ' original box. Includes 0.140 and 0 -500. tubes. Cat. No. round, zero enter, 0.'/s MA reg hardware. T 48003 s mounting hard- BC -1. won.ia Cat. No. M -101. each side, Cot. No. M -102. Col. No. I M -103. MA swing choke Type B- -Negeency 2H -7H 530 rang 300 to 1000 Ise 4'/s x 5'LS 3 Sez 5900ra $295 $395 $295 megacycles to be crackle caw. Cal. No. black e used with 368AS FC.205. door knob tube. $595 READRITE 2'r SQUARE METER O -5 59c Cat. No. BC-2. 95c PIN STRAIGHTENER ea. For miniature tubes -Gov't osi $4.80 our price --Cal. No. 49c MICA CAPACITATOR BC -375 -E GENERAL ELECTRIC .002 MFD 3000W VDC. Cat. No. 49c RT.101 SELSYN MOTORS MOPA TRANSMITTER In bombers and ideal way indicating the position of Used as liaison transmitter IF TRANSFORMER The of ground stations. Frequency range of 200 -500 rotary beams, wind Indicator, etc. (400 in aluminum shield and 1,500 -12,300 Kc. Is covered by Mounted DYNAMOTOR cycle). line cord and Kc. can 1500 KC, with sur , V. output means of 7 tuning units furnished. P ow.. waply -Inpoh 6.. IS 110 plug-in on box ctlans for operation on 10 and 20 Impedance coupled typa. Cal. 500 VDC of 160 MA, mounted VIruAC operarae far- $395 By slight modification No. T -19 95c with dreult brtoktrs, meters is Oscillator is self-excited niched. -Cat. No. SM- possible. rt . foi temperature compensated type. Power amp. a na two 10 n.. $095 100. 30MC IF TRANSFORMER Mwe Is neutralized class "C" using 211 tube and re al... D. S. Oov1. coupling circuit to In square ale ninum ran, Silver No. DM- Is equipped with antenna tie.. Cat. any antenna. Modulator le w slug tuned. Cat. No. T -20 29c 10 match practically L tel. class "B" using two 211 tubes. Power supply Is 24 V. DC dynamotor which furnishes 1,000 V. of 350 M. A. However, transformer is ideal for construction RECEIVER AND TRANSMITTER of 110 V. AC power supply. Transmitter out- resisters '4 wen fully Insulated, Sockets for tubes. Cat. No. 42.5 watts, phone MC receiver Asst put conservatively rated at SCR-522. 100.156 Cat. No. R -5- AT -10 with in popular abniegas. I9 75 watts CW, but may be pushed to 150 wons. and ha sminer completeplete ,g$/r per 100 $1.49 8 -8 MFD 350 WVDC. 20 MFD 150 WVDC. Complete with tubes, dynamotor, tubes. Used, In good condition. L con. Cat. No. RC 69c No. C and -88 n units, and Cat. No. RT -10.. AuY mica condensers, Cat. -12- sa tuning per 100 $1.93 Hailicrafter volume knobs -SX 28 15c cable connector plugs Wafer sockets, 4 -5 -6.7 and 8 prong. Pots -screw driver shaft 2 meg., 1 Brand now 2M, Cat. No. WF-4 -per 100 $2.95 meg., 150M, 50M, 25M, 5M, HALLICRAFTER RECEIVER 200 ohm -ea 29c 12' Utah P. M. Speaker, Alnico r5 A 144 MC Radar Osc., u es 15 E or R44 /ARR -5 HIGH FREQUENCY R45 /ARR7- -contains alai filter, variable FF. with 6F6 output transformer. Cot. Hy 75. Enclosed silver s plated lank selectivity A.V.C. and A.N.L. Osc. patterned ahem No. ST -100 $6.95 receiver. Patterned after 5.36A by HallicraMn. with variable coupling. Complete Receives FM and AM signols In the spectrum 5X28A Hallicrafter, voltage Asst knobs on wood and plastic. regulator completo with tubes push less tube $3.95 between 28 and 145 megacycles. Circuit has Cot. No. KP- 100 -per 100 $1.95 1Sc for high d powe.se panent. Jacks Pl. 55, PL 68 14 tubes including for pow operation. Cat. No. $1 614 $1.50 616 95c Powdered iron slug with Isolanlite coil frequency oscillator. Has two position setec- power 5X28A Johnson sockets 4210 -25W. Cat. No. form to match, ideal for broad tuning tivity control. Contains no internal 3950 Osc., and 15 -210 49c E.C.O 25c supply.ply. H as s corn tubas RF., Mixer. Complete with components tubes. Cat. No. T -99 65c Powderediron sA dug 10c 955 -9004 for power supply including transformer, choke, filter VV Mich. Sales add 3% Sales Tax condensers, and rectifier Write for FREE Bulletin tube $10000°

.- MNR4SAG A RADS 5249 GRAND RIVER DETROIT 8, 20% DEPOSIT REQUIRED ON ALL GO D. ORDERS

14 RADIO -CRAFT for APRIL, 1947 Start Your i gERV Choose one of these RADIO 3 GREAT NEW DEALS Includes TEST EQUIPMENT, TUBES, PARTS, TOOLS

3 complote going- in- budness packages. (If necessary they con be changed to suet your needs.) There never was o better opportunity thon now to start a profttaltlnj' business of your own. No fuss, no worry. Here's everything you ne Mails upon request. Write, wire or phone! / /. TURNTABLE STAND V. M. AUTOMATIC CHANGER a

TEST INSTRUMENTS Compact - Accurate - Priced Right! Jeweled Meter Range Selector Switch All multipliers bridge tested for 1 "' o y Zero od,ustment - built in batteries Molded bak elite case only 3- 15/16' y 2 -7/8' a 2' MODEL 450A Volt - Ohm - A Two Post Changer with well -made mechanism - Millionweoter plays 10' or 12' records intermixed. Low pressure crystal pickup. a 14' s 14'. lacked a \ hur instrument having a two to factory- sensitivity of 1000 ohms per sealed carton. factory guaranteed. R,It. CARTON aneeer Volts DC, SPECIAL 1595 µ All steel - adjustable holds turntable 15' above óF q95 0- 5/10/50/500 /1000; - bench EACH tilts to any position- speeds work saves NI ills DC. 0 -1; - - time - prevents damage to parts pays for itself on first ohms fill! scale, - job you need several at this low price. (1- 5000/50.000'500,000; - Ohms center scale. INTERFERENCE 30/300/3000. FILTERS A plug type filter eliminates noise when NET mplete with batteries 9.75 used in line cord of small motors, vacuum PHILCO BEAM OF LIGHT cleaners, etc. A "natural" for increased Selenium cell only, no holder. postpaid... $ 1.80 sales. MODEL 451A net eaeh 82c (Puts new life into Philco Changer- AC -DC Sapphire needle only, no mirror, postpaid $1.20 Volt - Ohm - Milliemmeter SLIDE RULE A dependable instrument of DIALS wide utility - sensitivity 1000 Crowe No. 534 -direct ratio ohms per volt. SHORT WAVE RECEIVERS drive - antique bronze Ranges: Volts AC, DC, and cutcheon Yr Output Ranges, travel 3'4'. 0-10/50/100;500/1800; NET with plot A. Ohms full scale, 500,100. lamp bracket.. -i 1 47. Ohms center scale, 7200. NET complete with batteries 13.65 JEWELLED PILOT MODEL 451B LIGHT ASSEMBLIES Same instrument xs above but has 25100 ohms fer veli Candelabra screw base sensitivity. Hall icraf ters S-38 ...... $47.50 for 110 volt NET complete with batteries lamp. 15.15 S-40 ( Replaces S-20R) 89.50 Mount in l' hole. SX-42 (Replaces SX-28A) 275.00 Lampe removable from frort of panel. MODEL 452A Available marked 1 -2 -3 or 4 on back Volt- Ohmmeter of lens. A superb instrument -1(N) microampere meter gives SELENIUM RECTIFIERS YOUR CHOICE net 19c 10000 ohms per volt sensi- tivity. Ranges: Volts DC, f vert permanent replacement for 117Z0 0-10'50,/ 100 500, 1000; -117Z3. etc. No filament-no socket- Ohms full scale. no trouble. 0-20W/20,0001200.000/2 hlees; 50 or moress0e Include IulL remittance with orders of /.3.00 or less. Ohms center scale, ""1 08 net 49 98e net 7 30/300/3000/30.000. Include 25% deposit with all C.O.D. orders of 2.3.00 or more. NET complete with batteries 13.65 MODEL 312 RADIO TUBES Veit -Ohm- SEND FOR FREI Milliemmter BARGAIN BULLETIN An economy' pocket meter featuring a 2' moving vane 1 i 1 meter. Get our monthly list Reads: AC -DC volts, of vailable tubes 0- 25/50/125'250; and discounts. Larg- Mills AC -DC. 0-50; est available stock of standard brand KMVIV SUPPLY & Ohms, 100,000; mfd..05 -I5. tubes maintained at Jacks provide range selection. all times. ENGINEERING NET Complete with cord and plug 6.00 CO., Inc. 125 SEIDEN AVE. DETROIT 1, MICH.

RADIO -CRAFT for APRIL, 1947 15 SPRAGUE TRADING POST

SPRAGUE RADIO NOISES FROM IF -31 FLUORESCENT LAMPS! FILTER STOP Radio noises caused by fluorescent lamps CAN be sup - a pressed -easily, Quickly and effectively. No lost time or WRITE for motion. Just install a Sprague IF -37 Filter on each fixture, copy of the complete connecting it directly across the incoming leads. IF -37's are 40 page Sprague Catalog especially designed for the job -and you'll be pleasantly of , resistors, surprised how effective they are in suppressing "hard-to- interference filters stop" interference that is so often conducted down the á test equipment. power lines, even to remotely located receivers. Buy them from your nearest Sprague jobber today.

FOR SALE- Rleknk 'SAX signal genera- FOR SALE -Seventy -Ore 3' meters, all tor rauplete with D.B. alrtput meter and kinds of amateur radio pans. The Radio 100 /1000 KC crystal calibrator, new con- Laboratory. 912 W. 151st St.. Ent Chia- SWAP - BUY - SELL dition. $1011. Precision 9121' tube checker go, Indiana. complete with latest charts. less than old, down. balance year $37.50. 25% Oscillo- FOR Stanror :510 P.P. ampli- FOR OR EXCHANGE -Magnavox C.O.D. Cupples Radio Service, 2007 WANTED -Used tube tester and SALE- SALE scope. Cash or trade. What do you need? fier transformer input with N' 15w P.M. 33 -1/3 rpm record player and playback Broadway, Galveston, Texas. Robert Heckman, Earlvllle, 111. speaker. Want Rider's manuals t Il and machine. Has built -in 35 nun. .1111 Pro- 10: station set-up alloator: 4. 6 or N jector. Complete with tubes. loud speaker power binoculars. 'scpe what have rad connecting cable. I( salient for class WANTED -Input I.F. transformer and FOR SALE -W.R.L. MT100 multlteeter rua? John It epa, Jr.. Main St.. Rldl- lecture work. etc. LEWIS B. Thornton. roll assembly for Majestic 15. Cash o wt $18.75, brand new with pair Whin do you landtown, Pa. 138.25 Union Turnpike, Flushing, N. Y. orr trade. need? Riddle Radio $1 test leads. Will send postpaid for $15. Service, 15 George St., Milford, N. Il. Adam Palmer, P.O. Box 63, Blacklick. Pa. WANTED -Complete set of Rider man- WANTED- Stanmr halters eliminator to recorder he used as power car radios uals: also Wilcox -Gay portable FOR OR TRADE -L1112 Precision for when Radio Serv- SALE FOR SALE-Closing out all my stack at testing on bench. Young Radio Sallee. A -103 dual speed. Herman's tube tester. perfect condition; 5 -tube 1947 list less 40% or better In quantities. All 729 W. Dominick St.. Rune, N. Y. ice, 803 W. Locust St., Bloomington, III. moth.' ECA radio & automatic record new tubes including 1N5; IHS; 6A? changer, walnut cabinet. cost $99.50, sacri- 6SK7 ; 6SQ7; 6ßJ7: 7Y4; 7t7; 12AH7 FOR SALE -Triplett radio teeter to W.J. WANTED fice at $79.50. Like new. Phillip.. 12J5; 9001: 128A7: 128117: 12807 -any numbers. v -Rider manuals- carrying case Including -o -m. signal Rog 433, lielington, W. Va. OAKS: 25143; Fu sale: Itt'.4 'steps' :1611: also OAK5: 6AK6; SALE: 25Z6 generator anti tube tester in cover. Used 3575; 15 u;; 2E24: 501.6; 11728; 27; 30 l'hilro ig. 1170, new. E. ten. like York- very little, $25. H. J. Krausen, 416 Wilson 95: 41; 42: 46: 55: 75; 78: 77: 78; 80 aunt,. 1746x N. SI., 47. Campbell Chicago Ave., Green liar, Wisconsin. FOR SALE -Radio-Craft and Service XXFM, rte. Write far details. Eddie III. 1936 1940. 15c copy or magazines, to per Howell, 'tote :2, Dillon, S. C. WILL TRADE latest Y.R.I. mures on $1.50 per year. All have corer.. Radio Ohm News, 1922 to 1930, 10e per roil'. m $1 FOR SALE -Appliance tester complete Radio and Television for cut amen bat- with instructions. Tests irons. toasters. M Ilene recorder. Stanley J. Radwanski, per year Majestic Steals 420 ac -de WANTED - Table model tele -receiver. ten' portable. all new tubes, $24. Also. Name, make. model, condition, and elastic clocks, efe. Only $5. Sal Radio 1531: S. Stumbling Ave., Chicago 23. fil, pria phonograph cabinet. Se. for de- covered. Have for sale 75 50L8's, .erne., 1131 Ave., Cranston, lt. I. Write channels lark tails. Lawrence Roeehot, 77 Church St., new; 50 35Z5'e, new. 30% off list. J. W. WANTED -Tao tube., 6516 or 6Aß8 or Wilkes- Barre, Pa. Smith, 1602 W. Pratt SL. Baltimore 23, WANTED--Capacitor checker. any make 6115. 11. & W. Radio & Appliance CO., Md. in goat mainline such ss BCO. 11150, Julius J. Horwlh, P.O. Box 1105. San 14'-1 -6ll or 11N. Also need a point -to- Angelo, Telas. WANTED -Short wave receiver. Have pdnt analyzer and speaker tester. E. Su- Argue A2F. 35mm. F4 and other camera URGENTLY NEEDED-Now or fairly new egpt. to trade. Also scarce tubes and 3' or 4" magnetic speaker In good con- IA, 5321 W. 30th Place, Cicero 50, !IL FOR SALE -Following tubes at 20ck off sensitive weak aig- IE7GT, parts to trade or sell. IL Ourshawita, 147 dition and highly to list: 11)001': 395; 1LD5: 1ß4T; nals as used tr some circuits shown In sci- 6117G; 61'50; 6165 Chester St., Brooklyn 12. N. T. PART TIME WORK WANTED -Raclin 1117G: 75: 26; 8K8: ence magazines before the war. Herod mech. wishes part time job 1214('7: 128E5; 695: ßP8; B; 46 Stepanian, Rt. :3, Box 449, Tulare, Calif. graduate 2.t40; 1223; 57.36 62670: 6A4 t Saturdays & evenings' in radio servire FOR SALE -U.T.C. typo P.\ -2L6 output slop. Gerstein, 5F7 : 51'40: 39/44; 42 and 43. Joseph lien 958 Brooklyn Ave.. Sweden. tansformer, Sil; Halllcrafters S -41W re- FOR Cooke electrical course, Rroukbm 25, V. Y. 4- 20.51. A dersut, New Maine. SALE -L7. 11'r, ceiver. $28; Simpson 5240 vo-nt meter 75 lemons, $18; 8 vols. McGraw -Hill with case, new, $90: Chekatube #Ciel 7 vola Pow- FOR SALE -Weston analyzer, brand new, "Practical Electricity'. $17; FOR SALE -Radio City Products 702 tube checker. $10. Eugene Wille, 9435 N. er Plant Operation. $15; 7 vols. Hawkins :772. 555. Peler P. laden, 8749 Crleplo 97th St., Milwaukee 10, Wise. Electrical Ed. sir. generator, good as new, $45. or what St., Philadelphia '36, Pa. Guida. $3.50. Tistaler, 56 have von? il. W. Colp, Bridgewater, Carey Ave.. Mika-Barre, Pa. Nina Scotia. Canada. FOR SALE OR SWAP -Radio engineer- WORK WANTED --Want spare timo radio ing, electrlal and radin servicing books. ervice work in shop or appliance atoro FOR SALE -Gen. Ratio arm box. 7 step, WANTED for rash or trade: 1 fil. trans. also assorted Audels books. All new, 1/3 in Racine, Kenosha, Milwaukee area of ach side cat. 11100 ohms. Type RIO, $15. 1.1 to 120V sec. 120v. pre. AC. Also off list. or will swap for test .apt. Walter Wisconsin. Saturdays or evenings °Y. Gen. Radio rariometer type 107F total parer trans. 120r PRI -70, and 6.5v sec- Israel. 97 Washington Ave., Winthrop 52, Myron C. Jonas, 924 Racine St.. Racine, Ind. at 100' 0.37 mlillhen., $15. W.C. ondary. Also 50 ma. 3%' meter, 1 -600v Mass. Wisc. Nielson, 60 Kay SL, Newport. IL I. DC. J. lt. (teed, 217$ W. $rd St., Dur- ango, í'a10. FOR SALE -One 5Y3 tube: 700v 90 ma. CT. transformer with 5 and 6.3v CT. FOR SALE-- 0111rardl's "Ratio Physics windings tat 2 -3 amps.): 10 11Y 100 ma. Course" $2: various other book, and filter choke: 10 mh. 50 ma. choice; two magazines. Write for list. lhilro Swl 100mmf. var. sing. spaced midgets; 5w table 111.10 radio. broadcast and short tuna. var. midget; 15 mmf. doublespace var. wire. $12: 1119 tank receiver und Denm- condenser. Lee Kent, 6507 N. Bell Ave., YOUR OWN AD RUN HERE FREE entio -e, new and complete. $59. Write for Chicago, Ill. list of cher radio article, for sale. Alfred Livinastime, L" of Ellis Are., Fair Lawn. FOR SALE -400 new and used tubes at The Sprague Trading Post is a radio subjects. Make sure your low prices. Will sell all or In small free advertising service to our meaning is clear. No commer- Also have s le pans and a few radio friends. Providing only cial advertising or advertising Arnold WANTED- -Zenith chassis 5905 with or tonus.meters. Write for details. that it fits in with the spirit of offering merchandise to the Cedastrer. P.O. lins 297. Hillsboro. N. H. t i bout l ob.: :r ld speaker. Cash. State this service, we'll gladly run highest bidder is acceptable. price :wd audition of set. Mullins Radio your own ad In the first avail- Obviously. Sprague assumes no Service. 152 Ella Ranson. Tullahoma, HELP WANTED -Need radio service man able issue of one of the six responaihility in connection Teo, for thriving shop In small midwestern city. or Witte giving full details of experience radio magazines in which this with merchandise bought and educational background. King's Radio feature appears. Write CARE - sold through these columns or POSITION WANTED- Eleetrnnle tech- Servire. P.O. Box 361, Montpelier, Idaho. FULLY or print. Hold it to 40 the resulting transactions, nician. Melville grad.. A,F radar, fleet words or less, and confine it to class 'phone license. $40. New York area Sire WANTED -RCA Victor serrire sors for Altmann. 1110 College Ave, New or What do you neetI7 Yolk 56, N. Y. 1939. Call trade. Send your ad to Nadyhnl Radio. 2710 No. Central ''ark Ate., Chicago 47. Ill. Dept. RC-411 SPRAGUE PRODUCTS COMPANY, North Adams, Mass. WANTED -- Flash -O -Graph Inrnai tube. pan 3 -1424 MS belonging to Fada Radio. FOR SALE- Rlrkok :4900 _S radio set (Jobbing distributing organization for products of the model 1tA. a elf"- old receiver. WIII pay tester. ac & de soils 0 to 2500, 1M Per Sprague Electric Co.) ash. Bevemourt's Experimental & Radio colt; ohms 0 to 10 meg.. also nap. and Shop, 75 Rockland St., S. Dartmouth. O.P. Adam W. Miller. First St.. Mead- Mus. elite, Pa.

ASK FOR SPRAGUE CAPACITORS and *KOOLOHM RESISTORS by name! 'Trademark Reg. U. S. rat. Ott

16 RADIO -CRAFT for APRIL, 1947 SUPERADIO

Recemt Discovery May }leralQa New Radio Era

By HUGO GERNSBACK

ON December 18, 1946, Johns Hopkins University Fahrenheit. These are well -known facts, and have been of Baltimore announced the discovery of what known for years, but the experiments of excessive de- they termed a new method of radio reception. grees of cold by Professor Kamerlingh Onnes at the By using it, radio broadcast waves may be University of Leyden, made during the past few years, picked up and detected without the use of radio tubes, have given us a great deal of food for thought. Professor electric current, antenna, or condensers. Onnes, by means of liquefying helium, has been able The discovery was made accidentally by Dr. Donald H. to approach absolute zero closely, reaching the low tem- Andrews, Professor of Chemistry, and Dr. Chester Clark perature of minus 457.6 degrees F. At such extremely of the University staff, with Peggy McEwan, a labora- low temperatures, a number of astonishing things begin tory technician. They were experimenting with an infra- to happen. red bolometer, developed during the war for "seeing" "It is well known that an electric current heats. If the in the dark. Connected to the bolometer was a .strip of conductor passes enough current it becomes white hot, Columbium nitride. The latter, about the size of a pin, as for instance the filament in an incandescent lamp. But was placed in a cryostat, which is an instrument that if you took the same electric lamp bulb into outer space cools objects down to about 15 degrees above absolute hundreds of miles above the earth's surface and tried zero, or roughly minus 444.4 degrees Fahrenheit. to light it up with the identical current, a most sur- A loudspeaker was in the bolometer circuit because prising thing would be seen. You would find that it no the scientists found this arrangement more useful than longer would light, for the simple reason that at such a more complex visual method of checking their results. extreme colds, all conductors of electricity lose their re- The experimenters were astounded when suddenly the sistance entirely. Professor Onnes was able to send tre- loudspeaker began to emit a radio program from the mendous currents through very thin conductors that local station WBAL. would ordinarily have become white hot and burned up Later experiments confirmed the fact that the strange or volatilized. Under such extreme colds, conductors are phenomenon was due to the tiny strip of Columbium termed supra -conductors, because they become supra - metal, which when cooled to a few degrees above the conductive to the electric current. But that isn't all. absolute zero point, became superconductive. In this Inasmuch as metallic in absolute zero lose all re- state the metal becomes highly sensitive to radio fre- sistance, once an electric current is started in a con- quency currents and acts as a receiver capable of oper- ductor, that current will keep on flowing without ating a small loudspeaker. Other stations aside from stopping. Here we have a sort of perpetual motion, but WBAL were brought in on the speaker in subsequent ex- of course it requires so much power to obtain it that periments. it would not be practical." The bolometer used by the Johns Hopkins scientists The unimaginative will no doubt say that radio is is a copper mounting about one inch in diameter. It con- not likely to be revolutionized by the discovery of the tains a threadlike ribbon of Columbium nitride, con- Johns Hopkins scientists. It may be contended that the nected to two wire leads. This is the heart of the bolom- expensive and cumbersome apparatus to generate the eter, which is exceedingly sensitive to infra -red waves. excessive cold would make such a radio receiver totally But that it was even more sensitive to radio waves impractical. Granted for the moment. But what will the caused a sensation! story be in 10 or 15 years when new research has Said the scientists -with commendable restraint: shown that the same results can be had with com- "No claim is made for the device as a revolutionary paratively simple and inexpensive means? Radio prog- discovery which will change all accepted methods of ress has a habit of picking up unusual odds and ends and radio reception. turning them into spectacular results. Without the old "But the inescapable fact is evident that a small rib- Edison effect, there would have been no radio tube. bon of Columbium which has been nitrided does, under Without Hertz's spark coil there would have been no proper operating conditions, become radio- receptive." electromagnetic waves to detect and consequently no To better understand what happens when metals are wireless nor radio. cooled to a temperature approaching absolute zero, I At this moment the radio phenomenon of the Colum- quote from my article in the February, 1928, issue of bium metal -while superconductive -is not understood SCIENCE & INVENTION (page 883) : at all by scientists. There are several theories on the "Science now knows that outer space contains no heat action, but none so far has given a full explanation. whatsoever, and that all space is at an absolute zero,* In due time the veil will be lifted -and then we will which, expressed in figures, is minus 459.4 degrees have real surprises. When that time comes our radio Recent astronomical researches indicate the temperature in open space receivers will certainly be totally revolutionized -our of the universe is 3 to 4 degrees above absolute zero.-H. G. Source: Professor Donald Menzel. Harvard Observatory. entire concepts of (Continued on page 73) RADIO -CRAFT for APRIL, 1947 17 IRE MEMBERS of New England will meet at Cambridge, Mass., on May 17. This is a postponement of the original RADIO- ELECTRONICS May 3 date announced in this magazine. The group, now known as the North Atlantic Section of the Institute of Items Interesting to Radio Engineers, will gather at the Hotel Continental. planes Six technical papers will be read and AMERICAN BROADCASTING hi JAMMED ILS SIGNALS on was described last La Guardia Field was due a large space devoted to exhibits by Europe month as approaching New England radio and electronic man- "only fair" by Everett Holles, news edi- to image interference, the serviceman's ufacturers. Non -members of the IRE tor of station WBBM, Chicago. In old bugaboo, reports from New York are invited, but advance registration is Vienna, he states, the Russians have a stated last month. The ILS (Instrument considered essential as facilities are station which is listened to by' 80 per- Landing System) signals were "cap- limited. cent of the population, while the Amer- tured" irregularly by FM transmissions ican radio in nearby Salzburg devotes from New York stations, pilots reported. The Cincinnati Section oi; the IRE its broadcasts largely to folk music and are also holding a May meeting. Their Investigators discovered that the 110 - food recipes. He also characterized the mc signals were beat against a 103 -mc technical conference will be devoted to American broadcast station in Berlin as problems of television, and will be held oscillator in the plane receivers to pro- a "crackerbox." 7 mega- May 3. duce an i.f. of approximately Reports of the first broadcast to Rus- cycles. Signals from WGYN, on 96.1 mc, the same i.f. when beaten COLOR TELEVISION licenses have sia from the new station in Munich, produce been granted a French concern by Co- coming through at about the same time against the 103 -mc oscillator. It is pre- lumbia Broadcasting System, it was as Mr. Holies' report, indicate that sumed that the receiver input circuits learned last month. The company, Sadir- overall Russian response was favorable were not sufficiently selective to reject Carpentier of Paris, has been granted but the programs needed livening up. signals from the broadcast station 14 manufacturing rights for television A critique from State Department megacycles off the tuned frequency, the transmitting and receiving apparatus officials in Moscow reported that the an- "mirror image" twice the intermediate under all the present Columbia patents. nouncers' accent was very good, and su- frequency from the channel. perior to the BBC, but the British broad- The trouble, which is suspected to be The company, it was said, will pre- led to the casters, they added, had superior dic- one of the factors which pare proposals to the French govern- crash -landing of an American Airlines ment authorities for establishment of a tion. They also reported that theie was too dramatic DC -3 plane on a beach near New York national color television broadcasting much effort which tended up to overemphasize delivery and distract City last January, has been cleared system in France. by filter circuits in the receivers. A group of the firm's engineers, led attention from program content. Re- ception was described as "only by M. Jean A. Widemann, in charge of fair." STANDARD FREQUENCIES broad- the television department, are due in Russians were reported to feel that cast by the Bureau of Standards station the United States early this spring to although the talk on American histori- WWV have been increased to 8, ranging make a detailed study of CBS tech- cal background was "interesting" it was from 2.5 to 35 nie. The 4 new frequencies niques, it was reported. also confusing and long- winded. are 20, 25, 30 and 35 megacycles. Ac- curacy of the standard broadcast fre- FACSIMILE NEWSPAPERS will be quencies has been increased fivefold, available to the public on a straight sub- LOWER PRICE TRENDS in radio re- and is now better than 1 part in 50 scription basis this Fall, John S. Knight, ceivers were seen last month with the million. publisher of the Miami Herald, declared announcement of a 20- percent cut in the A total of eight radio frequencies last month. His Herald, he said, has price of a popular Emerson model. Low- (2.5, 5, 10, 15, 20, 25, 30 and 35 mc) is already started experimental transmis- er prices have also been set on a num- now given. Seven or more transmitters sions and expects to be the first regular ber of less well -known brands, in some are on the air at all times, day and facsimile newspaper. cases the cut being greater than 20 per- night. This insures reliable coverage of Bringing the morning paper from the cent. the United States and extensive cover- breakfast table to the bed itself, fac- The Emerson cut, according to the age of other parts of the world. simile "is the most radical change in president of the company, Benjamin The services are: 1. standard radio newspaper publishing methods since the Abrams, was made to widen the con- frequencies, 2. time announcements, 3. invention of typesetting machines," he sumer market and step up production to standard time intervals, 4. standard said. a point where suppliers of raw mate- audio frequencies, 5. standard musical Members of the Herald have already rials and components would be war- pitch, 440 cycles per second, correspond- been working several months on prob- ranted in quoting lower bids as a re- ing to A above middle C, 6. radio prop- lems and details of the revolutionary sult of manufacturing and overhead agation disturbance warning notices. new method of newspaper publication. economies on their own volume. All of the frequencies are useful for field intensity recording by persons in- terested in studies of radio propagation. The 4 highest frequencies are broad- cast particularly for this purpose. The radio frequencies and other data are: Radio Time Power Audio frequency broadcast output, frequency The transmitter which me /sec. EST kw. cycle, /sec. broadcasts one of the 2.5 7 pm to 9 am 1. 440 frequencies from 5 7 pm to 7 am 10. 440 WWV. Radio- frequen- 5 7 am to 7 pm 10. 440 and 4000 cy stage is at left, a.f. 10 continuously 10. 440 and 4000 amplifier center and 15 continuously 10. 440 and 4000 4000 the control panel of 20 continuously 0.1 440 and 0.1 440 and 4000 right. 25 continuously 30 continuously 0.1 440 35 continuously 0.1 440 The station call letters, WWV, and other announcements in voice are given each hour and half hour.

18 RAD 10 -CRAFT for APRIL, 1947 IRE. These included: Benjamin DeF. Bayley and Frank H. R. Pounsett of MONTHLY REVIEW Canada; Pedro J. Noizeux of Argen- tina; Sir Robert Watson -Watts of England and the following from the the Radio Technician United States: George P. Adair, George L. Beers, Lloyd V. Berkner, Edward ELECTRONIC COMPUTERS for A PEANUT , recently L. Bowles, Robert F. Fields, Donald G. weather forecasting may be a step to- released by the Radio Corporation of Fink, W. W. Hansen, Capt. David W. ward control of weather according to America, is expected to have new uses Hull, USN; Fred V. Hunt, Karl G. Dr. V. K. Zworykin of RCA. "The hope in industry. The new electron tube, des- Jansky, Ray D. Kell, Charles V. Litton, for effective weather control rests in the ignated RCA -1P42, is the smallest James W. McRae, I. E. Mouromtseff, fact that the condition preceding many phototube ever offered commercially. D. E. Noble, R. M. Page, J. A. Pierce, of the weather processes which it may About the size of a .22 caliber long rifle C. A. Priest, W. W. Salisbury, E. N. be desirable to control is essentially un- cartridge, it has a maximum diameter Wendell and R. S. Burnap. stabl:.," he explained. They are "char- of only 1/4 inch and an overall length acterized by the accumulation of large just under 1 -13/32 inch. It is activated CHIEF SIGNAL OFFICER of the amounts of potential energy during an by light entering through a tiny win- U. S. Army is now Major General Spen- extended period. dow at its larger end. cer B. Akin, who succeeds Major Gen- "Thus, while the energy finally re- Comparing favorably with larger eral Harry C. Ingles, retired. leased may be enormous, that required in sensitivity, the tiny new to trigger the release may be quite mod- tube is expected to find many applica- est. Furthermore, the magnitude of the tions in business and industry, particu- triggering energy required will greatly larly in devices and machines where the depend on the time and place at which size of former phototubes has been a it is applied. Since the electronic fore- problem. In multiple- circuit control de- caster should make it possible to ob- vices, the new tube makes possible either serve the effect of applying given smaller devices or more circuits in the amounts of energy at different points same space. In animated signs, for ex- of the weather map almost instanta- ample, where each phototube is individ- neously, it will point the way to the ually wired to a light in the correspond- most economic measures which will lead ing position on the signboard, many to the desired change in the evolution more of the new smaller 1P42 tubes may of the weather." be used in a given area. When light, Control methods might include black- projected through slides or film, falls ening or whitening strategic areas, on and activates the more closely spaced causing convection currents in the air tubes, sharper and clearer pictures can above them. be reproduced on the lighted signboard.

HOW DE FOREST DISCOVERED and perfected the oscilla- tor is told by F. J. Mann in a story re- viewing the history of the Federal Tele- phone and Radio Corporation in last month's issue of Electrical Communica- General Akin, New Chief Signal Officer. tion. General Akin was born in Greenville, The vacuum tube oscillator, came into Mississippi in 1889. He graduated from being in 1912 while Dr. de Forest was Virginia Military Institute and was ap- head of research in the laboratory of pointed a second lieutenant of infantry the Federal Telegraph Company, prede- in 1910. His career included service ir. cessor of Federal Telephone and Radio the Philippines (1911) at various points Corporation. The had recently in the United States, the Canal Zone, been adapted to use as an amplifier and and, in 1941, again in the Philippines investigation was under way to find area. means of eliminating annoying howls He became Signal Officer of the and squealing which accompanied the U. S. forces in the Far East, later ac- tube's amplifying functions. Dr. de companying General MacArthur to Forest soon determined that the tubes Australia and acting as his Chief were producing not only audible squeals Signal Officer. He also served as Chief but inaudible radio frequencies as well. of Signal Intelligence Service and of Thus was born the device which, togeth- Radar and Radio Counter -Measures Service in the Far East, the Southwest er with the audion amplifier, introduced Lr the science of electronics. Pacific Area and the Army Forces of the Pacific. The new photocell has a diameter of I/4 inch. During World War II, in addition NINE OUT OF TEN PEOPLE in- SCIENTIFIC AWARDS were grant- to his other duties, he established and tend to buy a television receiver sooner ed last month by the Institute of Radio became Chief of the Research Section or later, according to a recent survey Engineers to Dr. Albert Rose of the of General Headquarters, Southwest by students of New York's City College. RCA Laboratories, Princeton, N. J., and Pacific Area. Only 6 per cent, however, were ready R. to J. Pierce, Technical Staff of the Bell For his services in the defense of the buy immediately. Prices they were will- Telephone Laboratories. The two scien- ing pay ranged Philippines he was awarded both the to from $150 to $500, tists were granted the Morris Liebmann Distinguished Service with the majority wanting a set Cross and the at less Memorial Prize for 1946, Dr. Rose for Distinguished Service Medal. General than $250. his work in developing the Orthicon tele- Akin has received no less than 7 other vision camera tube, and Mr. Pierce for U. S. and foreign decorations, including A RADAR - BEACON AIRLINE his development of the travelling -wave the Philippine Commonwealth Distin- across the entire United States will be tube. guished Service Star. Most of these set up this year, according to the Navy Twenty -five engineers and scientists awards and decorations were won dur- Bureau of Aeronautics. were also elected to Fellowships in the ing the Second World War.

RADIO -CRAFT for APRIL, 1947 19 HMTEMMH PRMLE8 Part V- Directional Arrays for 300 Megacycles and Higher By JORDAN McQUAY

designed to operate conceivably be a quarter-mile long and are vertically polarized and can be re- in the u.h.f. region of the radio almost as high! ceived well only by a vertically ar- spectrum -above 300 mega- Primarily for this reason, use of com- ranged receiving array. ANTENNAScycles- employ most of the plex directional .arrays is usually con- Horizontally polarized waves are basic principles of antenna technique fined to the transmission and reception more generally used in u.h.f. practice but also introduce some entirely new of radio waves less than 1 meter in because, unlike their vertical counter- concepts of radio transmission and re- length. And the full range of usefulness part, they are not attenuated when pass- ception. Chief among these is the high of arrays extends down to about 10 ing close to the earth's surface. degree of directivity obtained through centimeters in length.* Thus, the position (horizontal or use of antenna arrays. Radio waves less than 1 meter in vertical) of the various elements of an An array-as described in previous length have quasi -optical characteris- array in any plane determines the articles of this series -is an arrange- tics. They act very ment of antenna elements. One or more much like infra- A/2 radiating dipoles in conjunction with red light waves. one or more reflectors, directors, or With a suitable `BASIC A/2 DIPOLE i ° ne other dipoles, are used to provide, radiating array, 10° 20° 30° 60° through their combined action or inter- u.h.f waves may be B1-DIRECTIONAL PATTERN OF BASIC Art DIPOLE action, considerable directivity and con- confined and fo- 60° 50° 30°20° 10° sequent large antenna gain. An array cused into a very 70° may consist of a large number of ele- narrow beam of ments (Photo A) or a minimum of two r.f. energy, and elements (Fig. 2). then directed to- As in other antennas, a transmitting ward a similar re- array is the same as a receiving array, ceiving array. both electrically and structurally. Their These radio waves functions are reciprocal. travel along direct 80° The size of an antenna array is di- or semioptical rectly proportional to the operating paths. There is no wavelength. Theoretically, an array ground wave. Pro- might be constructed for use at any pagation does not wavelength. Practically, however, this depend upon the DIRECTIONAL PATTERN OBTAINED BY THE USE tends to be impractical for waves longer sky wave, as in the 20° 10° OF EITHER REFLECTOR OR D(RECIUR. R REFLECTOR ; D DIRECTOR. than about 1 meter (or frequencies low frequencies. alters the dipole pattern. smaller than 300 mc) because of the Arrays used for Fig. I -How adding a director or reflector direct relationship between wavelength either transmission and the physical size of the antenna or reception are mounted at least 12 polarity of the sent or re- elements. wavelengths above ground in normal ceived. For instance, an adequate directional practice. Thus, they are considered as The number and structural arrange- ment of the elements determine the pat- array for operation at 100 meters might functioning in free space and independ- ent of ground effects. tern of field strength or field intensity. power gain Dipole elements, whether radiating or Thus they affect the and of the degree of directivity of the array. parasitic, are usually constructed directional antenna arrays conductive tubing. Metal rods can also Extremely microwave en- may have directional patterns only a be used, however, since in meas- is to the outside of such few degrees width (generally ergy confined ured at half -power points). metals. Even though u.h.f. arrays provide a All elements of an array are mount- limited range of transmission, this high ed in a fixed position. If mobility in any degree of directivity is a distinct ad- direction is desired, the entire array is vantage. It permits multiple use of the moved without disturbing the relative same wavelength by countless stations positions of the elements: dipoles, re- having only small geographic separa- flector, or directors. tion. The high resolving power of u.h.f. U.h.f. signals transmitted by an ar- waves has made possible radar and ray of horizontally mounted dipoles are other navigational aids for airplanes horizontally polarized, and such signals and ships at sea. In this uncrowded re- can be clearly and strongly received gion of the radio spectrum, wide bands only by an array consisting of hori- are available for single channels useful zontally mounted receiving dipoles. to television, facsimile, and carrier Similarly, an array of vertically ar- telephony. ranged elements will send signals that Directivity provides either an effec- tive increase in transmitter power or At wavelengths of less than 10 centimeters, arrays are replaced by parabolic reflectors, lens receiver sensitivity, depending upon use systems, horns, and other radiating devices which of the antenna array. The same direc- Photo by U.S. Army Signal Corps will be discussed in the next issue of RADIO - Photo A- Billboard array used by Army radar. CRAFT. tional characteristics apply to receiving 20 RAD 0-CRAFT for APRIL, 1947 as well as transmitting arrays, result- before, or in front of, the radiating di- ing in very large power gain between pole, in a position toward the desired the two points. field of maximum intensity. Neither Use of ultra high frequencies simpli- type of element is electrically connected fies general system design, since the to the radiating or receiving circuit. physical dimensions of the components The simplest type of reflector con- or elements of the circuits are of the sists of a single piece of rod or tubing, same order as the length of the radio very similar in shape and general ap- waves passing through the equipment. pearance to the radiating dipole. How- For this reason, in u.h.f. technique ever, the reflector is slightly longer than it's desirable to have a visual conception the radiating dipole. of the actual length of the radio waves Such a reflector is mounted parallel being transmitted or received. to and about Simplest one -quarter wave behind of all antennas is a half - the dipole. A typical arrangement (Fig. wave dipole isolated completely in free 2) employs space. a reflector 5 percent longer than the center -fed half -wave dipole. If it were possible to feed energy spaced either 0.211 behind the radiator. The to one end or the center of such reflector is entirely parasitic in nature. a theoretical dipole, radiation would It absorbs power from take place the dipole and at right angles to the dipole. then reradiates it, acting somewhat like Since, in normal u.h.f. practice, the a second dipole. Length and spacing radiating dipoles of are usually situated the reflector cause the reradiation to in a horizontal position with respect have a phase and polarity relation to the earth, this theoretical -with dipole (and the original radiation such that the two all arrays that follow) will be con- fields of intensity add in the desired di- British Official Photo sidered in terms of the horizontal posi- rection of power gain and cancel in the Photo B -Radar antenna in Beaufighter nose. tion. (All dipoles and arrays discussed opposite direction. transmit or receive horizontally A typical arrangement (Fig. 2) em- polar- Only a small ized waves.) amount of energy ploys a director 5 percent shorter than travels beyond the reflector, because the the center-fed half-wave The complete shape of the radiation two fields dipole, spaced pattern cancel when they are of op- 0.1). in front of it. of the theoretical dipole in free posite polarity and phase. However, re- space resembles a doughnut, with the The director acts as a second dipole flected energy arrives back at the dipole by absorbing power from dipole passing through the center (RA- with same the radiating the polarity and in phase dipole and then reradiating it. However, olo- CRAFT, December 1946, p. 23). A with the radiating dipole, adding horizontal cross section of the pattern to due to length and spacing of the director the field intensity in a direction opposite the reradiation has a phase and polarity resembles a figure eight in shape, and to the reflector. The resultant is bidirectional (Fig. 1). field - relation with the original radiation strength pattern (Fig. 1) reveals pro- such that the two fields nounced of intensity add Reflectors directivity at right angles to in one direction and cancel in the op- the dipole. posite direction. This bidirectional radiation of a half - The resultant field - strength pattern is similar to the pat- wave dipole may be affected by reflectors Directors - or directors, parasitic elements assist- tern with a dipole and a reflector. A director is similar in shape and con- An example of the practical use of a ing in the unidirectional concentration struction to a reflector, of energy. but is slightly radiating dipole and a director is the shorter than the radiating dipole. The radar antenna (Photo B) used on many A reflector is placed behind a radi- director is placed parallel to and about airplanes, where economy of space is a ating dipole, in a position opposite in one -tenth wave in front of the dipole. factor. direction to the desired field of maxi- It is a parasitic element, unconnected In summary, directors and reflectors mum intensity. But director is placed a to a source of circuit energy, and co,- exert somewhat similar influences on a sists of a single radiating dipole when used separately. DIRECTOR BEFORE piece À/2 DIPOLE of rod or tub - When used in combination, directional ing. (Continued on page 69) h/2 /2-5% MAX

REFLECTOR BEHIND 13/2 DIPOLE

.11 . Fig. 2 -Same directivity is provided with either director or reflector.

DIRECTOR -i 3 " REFLECTOR ott MIS +1 Il o z 0' 111 ZERO AXIS IS FIELD STRENGT OF 3 c h/2 ANTENNA ALONE 3

al `< -2 -

British Official Photo -3 Photo C, above -A 4- element Yogi array under RAF night -fighter nose. .15 .2 .25 3 .35 ELEMENT SPACING N WAVELENGTHS Fig. 3, left -Effect of spacing of parasitic element on antenna gain. RADIO -CRAFT for APRIL, 1947 21 New "Prísmatone "Organ r- LAMPHOUSE TONE WHEEL MOTOR 11 "Ton e-U 7üel" PROJECTOR en and Sün pl i LENS Electronic Musieal lnxtruntent (Wm/pines Sound Wills Striking ('olor Effects;

The projector which produces the Prismatone s modulated light band.

disc is than that pro- celluloid. The pattern was impressed on HE Prismatone promises to be by of the greater 41 far the most attractive of all the jected nearer the center, because of the it by coating the disc with a sensitizing lower -priced electronic music in- greater speed at which the outer parts emulsion and transferring the pattern T struments. Like all electronic in- of the wheel move. Two photoelectric a skilled cells mounted on convenient handles are FRICTION DRIVE struments, however, it requires (RUBBER WHEEL) operator. Music is picked up from its held in the light beam and pick up the keyboard of colored light with a pair of interrupted pattern. They then translate photoelectric cells. The colors, inci- it into electrical voltages of the same dentally, are only for the musician's frequency, which are amplified to pro- benefit -white light would produce the duce musical notes. same tones, but the colors enable the A small lantern -slide projector is the A slotted mask player to distinguish notes more easily. heart of this instrument. PHONO This instrument is the invention of limits the projected light to a broad CLEAR SPACE MOTOR Leslie Gould, well known Connecticut band, which is broken up by the tone FRICTION DRIVE ADJUSTABLE FOR TUNING BY of many electronic devices. wheel. The dark portions of the wheel CHANGE OF POSITION Of MOTOR IN MOUNTING inventor SLOTS. R Izo -CaArr in the has described separate the "keys," while dyes on the past Fig. I -End view showing slot and rim drive. several electronic musical devices in- translucent portion give them their vented by Mr. Gould; last August we color. photographically from a hand -drawn printed his newest development, the Tone -wheel instruments have been negative. The wheel is mounted in a Sonicator, a radar -like instrument for constructed of metal, with holes to pass small lantern-slide projector, as shown small boats. the light. The Prismatone can be adapt- in Fig. 1 and the two photos. The instrument works on the tone - ed to this type of wheel by covering the A small phonograph motor drives the wheel principle. A translucent disc spin- slot with a strip of transparent plastic, wheel. By mounting it on a slotted base, ning ahead of a light breaks up the which can be colored in rows to produce its rubber rim drive can be moved in and light into rapidly alternating patterns the keyboard. out on the tone wheel to vary the speed. of light and shade. If the pattern on Mr. Gould's instrument uses the tone That is how the instrument is tuned. the disc is uniform, the frequency of wheel shown below. It is made of a Such tuning has the advantage that all the pattern projected through the edge heavy plastie resembling transparent (C(mtinued on page 63)

TONE AMPHOUSE ,WHEEL' MOTOR?

'PROJECTOR LENS,

Front view. Friction drive slides in or out on wheel rim for tuning This photo of the tone wheel may be used as a pattern for reproduction.

22 RADIO -CRAFT for APRIL, 1947 IU-625 OAT 144 SIC By L. W. MAY, JR,*

How to Convert the SCR -522's Transmitter to Amateur Use

PERHAPS the v.h.f. set best known and most widely used during the recent war was the ' equipment known under the Army desig- nation of SCR -522. This over-all desig- nation was given to a fairly compact and very efficient little unit operating in the region 100 to 156 mc. The SCR -522 comprises the following units:

Transmitter -BC -625 (Type T.5017) Receiver -BC -624 (Type R -5019) Dynamotor unit PE -94 (Type 5016) Rack-FT -244 (Type 5009) Case CS -80 (Type TR -5043) Control Box BC -602 (Type 5003) Jack Boxes (crew interphone) BC -629, BC -630 and BC -631 Recently, the SCR -522's were turned loose on the surplus market at astonish- Top switches: Oscillator, Frequency Multiplier, Power Amplifier. Bottom: Meter and Crystal. ingly low prices, considering the nature of the equipment, thereby giving the (Oklahoma City) these units sold for rock -crushing signal is wanted. hams of this country an opportunity for $5 each. Needless to say, one could not The BC -625 transmitter has seven getting on 144 mc with excellent rigs. begin to build such equipment at these tubes. These are: Complete SCR- 522's, including trans- prices. The first stage uses a crystal oscil- mitter and receiver as well as dyna- The BC-626 transmitter, with prac- lator tube VT -198 -A (6G6 -G). The motor and accessories, can be picked up tically no changes to speak of, makes plate circuit operates at twice the crys- at anywhere from $25 to $90, depending an excellent little low -power job for the tal frequency-such crystal frequency upon the individual surplus dealer. mobile or home station. Being crystal - being between 8,000 and 8,255 kc to fall Separate units, such as the BC -625 controlled with built -in modulator and within the 144 -148 -mc amateur band- transmitters or the BC -624 receivers, excellent signal stability, it will give an thus bringing the output of the first may be found at some surplus stores admirable account of itself. Alterna- stage to 16 mc. for as little as $10. In one instance tively, it may be used to drive a husky The second stage is a VT -134 (12A6) SWSAJG, Dallas. Texas. power amplifier on 144 mc, if a truly and triples the crystal -stage output fre-

VIAL OSC. VT- 196-A IST NAR. AMP. VT-134 2ND HAR,AMP.VT-IIB P.A,-VT-UB 109-3 109.1 6G6 -G 104 12A6 832 832 21 -I

115 19 132.1

102.62 leAAAr-- 109-4 132-2 151-2 026 154-1 00 121-2 -153-1

023 102-7 106

I48 TO SWITCH ARMS POS 5

147

6SS7140 3 1402 135 2 POS.3 oz 4 102 126 1383 ''-4 10 18V2 105-1 150 2 vT 199 1113159 STRAP 160

54 2 i -a MOO. MD C. 1ST 20 P.A. FJ- SPCN HAR. HAR. ,L 444 T"' 12v. -ISOV. +300V.4 AMP. AMP. AMP. 162 107 -I

2 53.3 SO V7 w PLUG -123-2 PLUG -123-1 BC-625 XMITTER

Complete schematic of the converted BC -625. Very little werk was necessary to make this an excellent transmitter on the 144-me band. RADIO -CRAFT for APRIL, 1947 35 quency of 16 mc. That is, the second - of tank condenser for maximum tripler sists of the speech amplifier tube, a type stage output is multiplied to 48 mc. efficiency, although a butterfly -type VT -199 (6SS7), which is actuated by a The third stage is also a tripler, but split- stator condenser is bridged across carbon mike, a 500 -ohm line from the here the v.h.f.-type tube 832 (VT -118) it for tuning purposes. station speech amplifier, or equivalent. is brought into play. This is a very The final r.f. stage makes use of an- This stage is then coupled to the push - efficient little bottle, by now well known other 832 (VT -118) operating straight pull modulator stage consisting of two to the amateurs, and works wonderfully through for a power amplifier. This type VT -134's (12A6's), which in turn well in the v.h.f. spectrum. This 832 feeds the antenna which can be any- modulates the plate and screen of the stage, being a tripler, converts the in- thing from a 20 -ohm to 500 -ohm load. final 832 r.f. amplifier as well as the coming 48 -mc energy from the output Variable coupling is provided by a screen of the 832 tripler driver stage of the second stage to the desired final swinging link and all coils and lines are which drives the final. This is a trick frequency of 144 mc. The plate circuit silverplated throughout. seldom seen in amateur practice, but of this stage utilizes a hairpin line -type The audio section of the BC -625 con- which it might be well to emulate on the v.h.f.'s. Hardly any changes are required to adapt this Army SCR -522 to the 2 -meter band. Here at W5AJG, these modifica- tions took the following lines, although after a look or two at the equipment, each ham no doubt will have his own l ideas. Since fixed -station operating is de- sired from the home location, and be- cause of a future possibility of chang- ing the role of the 522 from a complete transmitter to a driver for more power ( everybody dreams of more power), it was decided not to use the rack (FT- 2,14), nor the case (CS -80), but to -re- move the transmitter (BC -625) and mount it upon a standard 7x19 -inch relay -rack aluminum panel. Layout and construction The panel was laid out according to the drilling sketch on this page and Note shield on the cover. End view of final amplifier compartment showing 832 amplifier. two mounting brackets were made to bolt to the transmitter chassis. All con- trols are brought out to the front panel and tuning is done in the conventional i 4 -HOLES 10 CLEAR .250 BRASS SHAFTS showing the 5.000 way. The photographs ANT. ADJ. modified views will bring out the details HOLE HOLE FOR 0- I MA METER OBLONG 7 000 clearly. At this point it is well to men- 2.166 Du e6 250 tion the push -button ratchet -type tun- ing system originally used. An ingenious i 1.750 1.750 1.750 1.750 0 to be sure -one that could 1.689 arrangement be applied to ham use, no doubt -but to 1 avoid complications and too heavy brain in of reg- 4-41115 4.125 AL SWITCH HOLE work, it was scuttled favor TESL METER ROLF ular tuning knobs. As well as shifting to any of four preset channels, this push- button ar- r, rangement also selected the proper 19.000 1 STANDARD 7 X 19 RELAY RACK crystal at the same time and also tuned it as a drilling sketch. This front panel drawing is dimensioned so the constructor may use the BC -624 receiver -but that is an- other story. A new 4- position crystal switch is brought out through the front panel for o selection of any one of 4 crystals from 8,000 to 8,225 kc. The original crystal switch was removed and the wiring merely substituted on the new switch. In the old arrangement, the 3 crystals not in use were grounded. In the modi- fied arrangement, this was not done - mainly to simplify the contact arrange - ment needed. The oscillator and frequency-multi- plier tuning knobs as well as the final amplifier plate tuning are lined up in a group of four along the middle right of the panel. These shafts were made by sawing the correct length of '4 -inch brass welding rod and drilling and tap- ping one end for 8/32 threads. Each shaft is thus merely screwed down tight to its proper tuning -condenser control in the original transmitter, since each shaft 75) to the original dials. (Continued on page Top view of transmitter. showing how extension shafts are fastened RADIO -CRAFT for APRIL, 1947 36 TELEVISION FOR TODAY Part XI- Electromagnetic and Electrostatic Deflection Systems

ACOMPLETE electrostatic de- By MILTON S. KIVER The method of centering the electron flection system, combining the beam is simple. Two parallel 1- megohm synchronizing and deflecting nized by a negative pulse, which drives form a resistance net- circuits is shown in Fig. 1. De- one half of the multivibrator into cut-off work. A third parallel branch across tection and clipping occur in the syn- and forces the other half into conduc- the potentiometers contains two 470,000 - chronizing pulse detector which is one ohm resistors in series with each other. half tion. This discharges the saw -tooth of a 6H6. The time constant of Rl generating condensers C2 and C3 and From the connection between the two and Cl, in the detector load network, causes the beam to retrace into position 470,000 -ohm resistors, leads run to one produces a bias across Cl which permits for the following line. C2 is the charge - horizontal and one vertical deflection conduction through the tube only at the discharge condenser in the horizontal plate. From the movable arm of each of synchronizing pulses. At these moments, circuit; C3 performs the same function the 1- megohm potentiometers there is a the charge on Cl is replenished and the in the vertical circuit. Condenser C2 is connection to the other vertical or hor- pulse of current develops a pulse across charged through the 470,000 -ohm re- izontal deflection plate. As long as the R2. From R2 the pulse is transmitted sistor and the 500,000 -ohm width con- movable arm of each is through L1 and the .05 -µf condenser to trol during the interval that the half of at its midpoint, no difference of poten- the 1852 pulse amplifier. Ll maintains the multivibrator to which it is attached tial will exist between either the two the high -frequency response of the is nonconducting. The position of the vertical or the two horizontal plates. transfer network from the detector. movable arm of the potentiometer de- If the beam does not position correctly, Square waves contain many harmonics termines how fast C2 charges. This in adjustment of the proper centering or and loss of the higher -frequency corn - turn controls the horizontal sweep of positioning potentiometer will bring the ponents would round out the steep sides the electron beam. In the vertical sys- beam to its proper place. of the pulse and destroy the sharp, clean tem, there is no direct control of the The centering controls are placed as trigger action. The 1852 amplifies the charging of C3. Instead, the height con- close to the highest cathode -ray tube pulse while completely removing any trol is connected as a volume control and potential as possible to avoid affecting vestiges of image signal that may still the proper amount of saw-tooth voltage adversely the electron beam. Physically, be attached to it. The output network of tapped off. in the cathode -ray tube, the deflection the 1852 consists of a 5,000- and a plates are located well within the elec- 20,000 -ohm series resistor. The pulses The sweep circuit amplifiers tric field of the second anode. To reduce are separated by R -C filters in the The 6F8 -G horizontal sweep amplifier distortion of the field as much as pos- branches leading to the horizontal and is a conventional double func- sible, static voltages on the plates are vertical sweep oscillators. The grid cir- tioning as an amplifier and phase in- at the second -anode voltage. The saw - cuit of the horizontal oscillator has a verter to develop a balanced output for tooth deflection voltages then vary the high -pass filter composed of a 50 -µµf the horizontal deflection plates of the deflection -plate potential for a linear de- condenser and a 2,200 -ohm resistor. Be- cathode -ray tube. Tracing the leads flection of the beam. cause of the extremely low time con- from C4 and C5, we note that, besides In certain television receivers, with stant, only the sudden changes at the going directly to the horizontal de- small screens, single -ended amplifiers start and end of each.ulse are effective flection plates, they are also attached, are used. In such a receiver, one plate in producing pips across the 2,200 -ohm through 2.2- megohm resistors, to a of each deflection set must be tied di- resistor. centering network. The saw -tooth de- rectly to the second anode while the At the input to the vertical sweep flection voltages are placed across the second plate of the set is varied above oscillator, we find a long time- constant 2.2- megohm resistors while a d.c. center- or below this fixed potential for deflec- filter, determined by a 2.2- megohm re- ing voltage is fed through the resistors tion of the beam. When the beam is at sistor and a 0.001 -µf condenser. A sec- to the plates. either edge of the screen, the potential ond 2.2- megohm resistor is shunted to In the vertical deflection system the of the second plate may vary consider- ground to complete the d.c. path for any layout is almost identical, the only ably from that of the other plate or electrons caught in the grid circuit. difference, necessitated by the variation the second anode. The accelerating field Both sweep oscillators are cathode - in saw -tooth frequency being in values is then distorted and the beam is thrown coupled multivibrators. Each is synchro- of certain parts. out of focus. The visual result is a

HORIL 1/2 0E61-16 DEFL.PLATES 6SN7 6F8- G VERT. DEFL. PLATE S DET. 14ORI2.SWEEP OSC. HORIZ.S'WEEP AMPL. C4I.00V2SKV.

11 1.001 47K C2I500uuI I 39K 47K/IW. (5ff1J0V25KV 2. 68K TOOK WIDTH T.1 CONT. 2.2 4.7K IOOK MEG 1CC lI .t----- e8t300y, Bt0300V. 3.3K 13+ 3.3 MEG -112 2.2M.G = HOLD SKV-v LI CONT. VERT. SWEEP AMPL2 50Mh 5(uµí 6F8 "G VERT. ME ME 5R SWEEP OSC I00K IMEG t.1c3 rtla rI HEIGHT 39K g4701t 1W. .05 .005 2.2 MEG CONT. I S 47K IN CENTERING 70K CENTERING 2.2 20K .2 MEG IMEG 4.7K CONT MEG 00K 0+300V. ALL ML B-1- ,}IMEG _ I00K FOCUS C.R.T. 1! 500uy( OLD CONT. MEG -4 a+300V. I MAS.Bt OF H.V. SUPPLY

Fig. I -A typical system for electrostatic deflection of the cathode ray. This method is employed in many small television receivers.

RADIO -CRAFT for APRIL, 1947 37 6H6 6SN7 ,Rp. VID.DET1 SYNC.CLIPPER TO IST VIDEO AMPL. VERT.OSCs (VERT. DISCH. IK .025

I MEG 100uh VERT. 3300] 1 rl DEFLECTION V r-y 8+300V. COILS `l a3 1 220K NEARITY CONT. IOn 25 MEG _ / .2jI_ =100K HEIGHT CONT. B+300W .2MEG 48K 8+300 - H D CONTCHARGE-DISCH.COND. 5V4 -G 1852 SYNC. AMPL. 8.2 K B.2 K 180u0FA/ 80 7HORIZ.OUTPUT DAMPING IOOK .05 .005 2.2K2K 50uuf "5A0 '`.005 470K II LH 1 OK 2.2K r I I T 6SN7 50K 6-) HORILOsc. 20K I00K B+ HOLD CONT. B-3K 100Z 2r 12.2MEf, B+300V Fig. 2- Complete electromagnetic deflection system. This is better adapted to larger tubes and is used in most commercial receivers. blurred image at one edge. With bal- fleeting coils. Each is shown in Fig. 3, ously, for the electrostatic case, only the anced deflection, the field is symmetrical together with an equivalent diagram of condenser voltage was necessary. and beam defocusing at the edges does the output circuit. In the triode am- The importance of obtaining proper not occur. plifier (Fig. 3 -a) the resistance of the wave form cannot be overestimated, E tube (about 10,000 ohms) represents a especially with large- screen tubes. An Magnetic deflection systems significant amount of resistance. The improper wave form will show up as A complete electromagnetic deflec- inductance L is the reflected impedance nonlinearity or bunching together of the tion system is shown in Fig. 2. Essen- of the coil and, for all practical pur- elements, producing a distorted image. tially it contains the same sequence of poses, is purely inductive. Hence, the Since it is difficult to generate exactly circuits found in the electrostatic sys- load into which the tube must work con- the right wave form, a correcting net- tem and, as such, requires little ad- tains a resistance and an inductance. work is generally included between the ditional explanation. However, we are The current through the inductance point where the deflecting voltage is now dealing with a set of deflection coils must be a saw -tooth current, since this, generated and the final sweep amplifier. instead of deflection plates, so certain transferred through the transformer The control provided for adjustment is differences do exist. One is the type of to the deflecting coil itself, will deflect known as the linearity control. In Fig. 2, voltage that must be applied across the the beam in the proper manner. The ob- the 5,600-ohm potentiometer in the deflection coils to obtain proper deflec- ject, then, is to determine what form of cathode circuit of the 6F8-G output tube tion of the electron beam. With deflec- voltage, applied to the input terminals is the linearity control. With it, the tion plates, a saw -tooth voltage varia- (in this case, the grid of the tube), will operating point of the amplifier can be tion across the plates produced a corre- produce a saw -tooth current through shifted along the curved portion of the sponding variation in the electric field the transformer primary. tube characteristic until the deflecting between them. Since the electron beam The development of this voltage is voltage is "distorted" into proper form. follows in step the electric field vari- shown in Fig. 4. The separate voltages Close inspection of the entire deflec- ations, the proper pattern is traced out. necessary for the resistor and the coil tion circuit of Fig. 2 reveals that while Suppose we apply the same deflection are shown. By combining both voltages the vertical network conforms to the voltage to a set of deflection coils. The within one wave form, we will obtain a preceding discussion, the horizontal net- pattern, as seen on the cathode -ray saw -tooth current when applied across work does not. Here we find only a screen, will have marked traces of non- a combined resistance and inductance. charge- discharge condenser, without the linearity because a saw -tooth voltage This, then, is the voltage that must be series resistor. It would seem that the across an inductance does not produce applied to the grid of the final amplifier. proper wave form is not being generated a saw -tooth current. The electrical in- The problem of developing this wave in this branch of the circuit. Let us ertia of inductance will not permit the shape from the synchronizing pulse of examine the output tube of the horizon- current through the circuit to change the incoming video signal can be de- tal system. Since the 807 is a , instantaneously. If we apply a rectan- termined by circuit analysis using differ- the circuit of Fig. 3 -b will apply. The internal resistance of the pentode is ex- tremely high and completely dominates impedance. Consequent- DEFLECTION E the plate- circuit IIE DEFLECTION COILS ly, a saw -tooth voltage applied to the COILS grid of the tube will produce the re- quired saw -tooth current in the plate Lt circuit. This, in turn, will be coupled to TRIODE OUTPUT AMPL. PENTODE OUTPUT AMPL. E+ ? the horizontal deflecting coil. Note that Pp Rp entire difference between the vertical the 4 1M t, and horizontal output amplifiers lies in REFLECT ED DEFLECTION (r:)AMPLIFIED SIG. REFLECTED DEFLECTION AMPLIFIED SIG. COIL INDUCTANCE L re- COIL INDUCTANCE L o the relative magnitude of the plate YY sistances. If we replace the pentode a EQUIVALENT CIRCUIT EQUIVALENT CIRCUIT with a triode, the deflecting waveform Fig. 3-Typical triode and pentode output sweep amplifiers and their equivalent circuits. will have to be modified accordingly. guiar pulse of voltage across a coil, the ential calculus. The result indicates that One additional circuit in the electro- current through it will be saw -tooth in if a resistor and a condenser are con- magnetic deflecting networks requires form. In practice, however, we do not nected in series and placed across the attention. This is the damping circuit. have a purely inductive deflecting cir- output of the synchronizing oscillator, Damping circuits are needed because of cuit, but rather inductance and resis- the desired wave form will be obtained. the tendency of the coils to break into tance. Consequently, modification of the Hence, in the vertical system of oscillation when subject to the rapidly square -topped wave is necessary. The Fig. 2, the charge -discharge circuit changing voltages during each retrace exact modification needed will depend (C, R) is composed of a 0.1 -µf condenser period. The distributed capacitance and upon the resistance and the circuit. Let in series with a 3,900 -ohm resistor. Note inductance of each coil forms a resonant us consider the two types of output am- that the full voltage from both resistor circuit which is shocked into oscillation. plifiers which are used to drive the de- and condenser must be taken. Previ- (Continued on page 62)

38 RADIO -CRAFT for APRIL, 1947 Transatlantic News From our European Correspondent, Major Ralph Hallows

triplet of low- capacitance insulators. size of the shoal from the area which At the junction between the two sec- it occupies. The echo sounder is now tions is a platform carrying a variable being used most successfully for loca- . At the top of the upper section ting not only herring shoals, but also are radial booms, each 30 feet long, those of other fish. made of tubular steel and joined at their ends by peripheral wires. The Planes and television booms ends of the are telescopic. The At one time booms it was believed that radio IN Britain there and their wires form an adjust- relays be able capacitance loading. would used as links between are no spon- (Continued on page 67) sored broad- The variable inductance coil is con- cast programs. nected between the upper and lower A l l hopse - pro- portions of the mast. With these and the duced radio enter- telescopic booms at the top the induct- tainment is fur- ance and capacitance loading can be so nished by the BBC in return for the regulated as to provide that distribu- annual fee of $4, which we pay for tion of current in the antenna which the license to use a receiving set. Since gives the desired elevational polar dia- nearly 11,000,000 people take out such gram, with maximum ground wave and licenses each year, the BBC's annual minimum sky wave. income is not too bad. The aim of the The radiator thus can be closely ad- BBC is to put on the air daily three justed to secure the greatest possible alternative programs -high -brow, low- no- fading range. The new antenna has brow, and middle -brow-which can be proved highly successful, perfectly received well in any part of these steady reception being now secured in islands by ordinary sets. The high- large areas where fading was once brow program is a recent innovation prevalent. and one of the big surprises of the day is the warm welcome given to it by all Fishing by radar sections of listeners. Owing to postwar hold -ups we have not yet reached the Around the coasts of Britain swim stage at which the three alternative vast shoals of herrings, which move programmes are available in every re- always in a clockwise direction as they mote corner of the country from triple make their interminable circuits of high -power transmitters. The middle- these islands. So persistent is the in- brow and the low -brow programs, how- stinct inherited through millions of ever, are radiated by 100 -kw stations years that herrings placed in a glass and can be heard well nearly every- aquarium tank continue to circle it where -but not quite everywhere. clockwise as long as they live. The fish- ing fleet follows them round the coast, Britain contains many large Areas in its voyage which deep, valleys starting annual off the north- narrow are sepa- west coast of Scotland and working its rated from one another by ranges of way around. hills. There is, problem right The fishermen have further, the big now pressed into their service the echo- of built-up areas, in which the attenua- sounding machine, which works tion of radio signals is acute. This is on the principle. One of their diffi- particularly true in the London neigh- radar big about culties is that the shoals swim at differ- borhood: 30 percent of our popu- ent depths at different lation lives within a 30 -mile radius of times. When London. they are near the surface it is not diffi- cult to locate them visually; but often The London triple transmitter is they travel considerable distances at situated a dozen miles north of the great depths. Then the fishermen might capital at Brookman's Park. Until re- spend days finding them by ordinary cently its 877 -kc 100 -kw middle -brow methods. The principle of the echo transmission has been poorly received sounder is well known. In the Marconi in homes 40 miles or more away to the Visagraph type an audio oscillator south, though in other directions recep- transmits waves straight downward tion has been entirely satisfactory. from the bottom of the ship. These re- Fading after dark has been the main bound from the sea floor and are picked trouble. To combat this the BBC has up by a receiver. It passes them just erected the last word in antifading. through an amplifier to a visual indica- antennas. tor, recording the travel time of the This takes the form of a 500 -foot waves translated into depths. It has lattice -steel mast which can be readily been found that if there is a shoal of tuned as a half -wave vertical radiator: fish below the ship, two echoes are re- 877 kc corresponds to 342.1 meters, or ceived, a strong one from the sea floor 1,122 feet. The mast is divided into two and a fainter one from the fish. The sections. The lower part, 40b feet in instrument has been adapted to give a height, stands on 3 hollow cylindrical continuous graph, showing the depth insulators, each 1 foot high. Between at which the shoal is moving. By steam- Courtesy British Insulated Callendar's Cables, Ltd. the two sections of the is mast another ing to and fro a vessel can ascertain the The BBC's two- section anti- fading antenna. RADIO -CRAFT for APRIL, 1947 39 RADIO DMA SIilìlì7' 345

ADMIRAL MODEL 6RT44 -7B1

ALIGNMENT PROCEDURE

I. Loop must be connected during alignment. any serious deviation or if there has been any Check the set screws that hold the tuning tampering, turn the adjusting screws until this drum to the shaft fo see that they are tight distance is correct. and that the drum has not slipped on the 4. Be sure both the net and the signal generator shaft. The correct position of the drum can are thoroughly warmed up before starting be seen on the manufacturer's stringing dia- alignment. gram. 5. Turn receiver Volume Control full on. 2. In the closed position the stop on the rear of the dial drum must be against the stop post. 6. Use lowest output setting of signal generator that gives a satisfactory reading on meter. 3. With the gang wide open, all slugs should be IYs inches out of their coil forms. If there is 7. Proceed in sequence as outlined below.

Adj. Trimmers Connect Dummy Antenna Signal Tuning Gang Step Signal Generator Between Radio and Generator Setting in Following To Signal Generator Frequency Order to Max.

Set Change Switch to Broadcast Set I Band Pointer B, C, D 455 ke to Upper Limit FEATURES: 1 6SA7 Pin No.8 I 0.1 Mf Automatic Record Changer 2 Before proceeding to step 3 check pointer travel as outlined in manufacturer's data 7-Tube Receiver under "Pointer Adjustment." 2-6SK7 E, F, G 6SA7 3 Black Loop Lead 20 MMf 1605 ke to Upper Liimrit If not available wrap 2-6SQ7 several turns of gen- Set Pointer 6V6 4 Black Loop Lead erator lead around 1300 ke to 1300 mark H, I, J 5Y3 the black loop lead. on Slide Rail Aeroscope Antenna 5 Set Band Change Switch to Short Wave Position. Two Tuning Bands 535 to 1600 kilocycles Set Pointer IC, M 9 to 12.5 Mc. (25 end 31 meter short- 6 I Black Loop Lead 400 ohms 12.5 me to Upper Limit L, wave band) I I Cabinet Set Pointer 7 Black Loop Lead 400 ohms I 12.0 me to 1300 mark N, O, P 20 inches wide, 123/4 inches high, 185/g on Slide Rad inches deep

END FRONT f1 f1 TUNING SLUG DL- PILOT LIGHTS IST AUDIO REPLACING ® If it becomes necessary to change a tuning slug proceed in 8 A the following manner: Set the gang to its wide open position, unsolder and remove the old slug. Set the slug adjusting screw ® `O about half way down. Place the new slug in such a position that ANT G M 1ST I.F. 2ND I.F 13/4 inches of its length is above the coil form. Solder it in this ® position, making sure that it does not slip during the operation TOP OF CHASSIS B.C. S.W. and that the slug wire is straight. Proceed to realign the set as B.C. S.W. SPKR PLUG shown in the chart. TUBE AND TRIMMER LAYOUTS

=100 IMEG .01 0 400V. IMEG. .01uf 2 M 40oK -v.0 s-1 71( 390 C20 100 r--VVr .02uf 470KIW 20 270K uf 47K ç 254

INK IOMEG IMEG { 5Y3-G T3 ' `PHONO INPUT F-444"--!----4m7.. 115W.3R.F. .2400V.1 D< FILTER CH 550.. 117V. OSC.SW.2 ISOK 12K AC o 060s--- P0S.2 ° B< - 5W -wC20 POS.' B.C. POS.3 1C7 . II PHONO S.W. 3 I.F. 455 KC _`.35ov.' 2 6SK7 6SA7 6SK7 6S01 6507 6V6 2DL1 DL2 vsII L6 OSC. MJo C23 Cr C12 ° CATH. / g g MOTOR ; °a C HC 1 eV.C.TAPPED AT 0(p° PHONO F 120 0 500K APPROX. II Ì 100 - CONDENSERS GIVEN IN upf ARE MICA, THOSE CODED ARE IN SILVER MICA. COND. VALUES INJ'yf UNLESS NOTED. 40 TRIMMERS. (20 =31N1. VALDESINiyf OF CODED CONDENSERS: C2, 140; C3, 25;C7,65;C8,420 ;C11,65;C12,200. C21,C22,C23= 3- APRIL, 1947 40 RADIO -CRAFT for Television today is clearer, sharper, and brighter - thanks to the improved kinescope, of picture tube, perfected at RCA Laboratories.

The Picture Tube that brought'Yife "to television

The screen on your Iloilo. tcliv -ision citeutcut that cow J enjo\ it von were table model receiver is the face of a at the event in person -and on top of large picture tube. And the skater you that it's all brought to you in the com- see on the face of the tube is the iden- fort of your own home ... you don't tical twin of the skater being televised. have to move from your favorite chair. Pioneering and research in RCA RCA Laboratories has made pos- Laboratories led to the development of sible outstanding advances in every this tube which allows none of the prig- phase of television. And for television ; inal realism to be "lost in transit." It at its finest, be sure to select the re- reproduces evervthing the television ceiver bearing the most famous naine in I:ulusicc "li e -Wanes," feature camera sees, shows you every detail, television today -RCA Victor. on all RCA \ t or home television keeps the picture amazingly lifelike receivers "lock.' the picture in tune with the seudin, station. It assures and real. Radio Corporation of America. RCA Build - you brighter, clearer, steadier pic- ing, Radio City, New York 20. Listen to An RCA Victor television receiver tures. If television is available in the RCA Victor Shame. Sundays. 2:00 P. M., brings you all the action, drama and your vicinity, ask your RCA Victor ex- Eastern Standard Time, NBC Network. dealer for a demonstration.

RADIO CORPORATION of AMERICA

RADIO -CRAFT APRIL, for 1947 41 DE LUXE PHONO OSCILLATOR TRANSVISION RECENTLY we constructed several with a very sensitive portable receiver phono oscillators using the 6A8, and a good signal was heard up to 80 TELEVISION KIT 35L6, and 117L7 in various circuits. All feet. At 100 feet, it could hardly be to be in heard and it was inaudible at 125 feet. Offers you a High Quality of these were found lacking some respect. An oscillator of this type may radi- It occurred to us that an electron - ate for quite some distance. The FCC TELEVISION RECEIVER coupled oscillator with a resonant plate formula (157,000 divided by the fre- Ready for Easy. should work well when high -level modu- quency in kilocycles) is used to deter- maximum legal radiation dis- Rapid Assembly lation is applied to the . mine the In its final form, the oscillator was a tance in feet. If the unit is operated on 12SA7 with a tapped coil in a conven- 1500 kc, the distance would be 157,000 tional e.c.o. circuit. The plate circuit 1500 kc or 105 feet. If the signal can was fed through the secondary of a be heard at this distance, the length single -layer broadcast - band antenna of the antenna should be reduced. Un- coil. The grid and plate coils are mount- der no circumstances can it be allowed ed at right angles to each other to pre- to interfere with any other person's re-

pNONO 12J5 .01 12F5 .of I2SA7 3'-0- ANT. _-1-- t600v. 10016 [LI - I 100K A05 MIKE /Li\ I 30w1 60K 75 to MEG R6 Easy -to- Assemble: No knowledge j 150V 505 of television required. COMPLETE 2K 0 75K 1.55 4-W1rT 40K MICA easy -to- follow INSTRUCTION 25v. Sv. SHEET gives you all the knowl- edge you need. This Kit INCLUDES SOUND, all component parts, and the follow- s 12F5 1235 125A7 OsC: ing:- L Specially desicned Televi.+inn An- tenna. vent interaction between the circuits 2. A $30.00 Lectrovision seven -inch which will cause unstable operation. Picture Tube ... plus ALL other The microphone amplifier is a well - tubes. shielded 12F5 which feeds into a 12J5 3. Pre -tuned R -F unit. phono amplifier. The output of this tube 4. Finished front panel. appears across a 60,000 -ohm resistor t 5. AU solder and wire . and silty and modulates and tone control network II7v.AC/DC feet of low loss lead -in cable. oscillator control grid. 220a LINE CORD SW.ON R6 the 1 Operates on 110V.: 50 -60 cycles A.C. Plate and screen grid voltages are COMPLETE KIT $159.50 supplied by a 35Z5 connected in a half - lour cost wave rectifier circuit. All parts are mounted on a 10 -inch reiver, even within the 105 -foot dis- PLAY THE chassis to prevent crowding. Shielding tance, as such interference immediately grid leads and running filament wires makes it illegal. In almost every case, much radiation is caused by too long Sdk close to the chassis and well away from too grid and plate leads will reduce hum in an antenna. Cut it down or take it off A 9 YOU LIKE-a//um. YOU LIKE altogether! It is also a good idea to op- with the tutu PwiL- ttltut. the microphone amplifier circuit. No fader control was used since we did not erate the oscillator as close to the re- plan to use the microphone and phono- ceiver as convenient, making strong G. Eslick WEBSTER graph at the same time. When the phono radiation unnecessary. -IV. Mnd.c 50 jack is plugged in, the output lead from the 12F5 is opened. U.H.F. RECORD REACHED $21.60 The oscillator is turned on and al- this new record Compact and efficient, lowed to warm up for a short period. Highest frequencies used in television changer gives trouble -free operation. clear transmission have now attained almost true fidelity of reproduction, and is A broadcast receiver is tuned to a some a billion megacycles, according to a re- gentle to records. channel around 1,500 kc. (/n areas port from the Allan B. Du Mont Labor- IMMEDIATE INSTALLATION a. suitable clear channel cannot be found end the case atories. The high -frequency waves are, We can now add phono-music to on the high of band. In this your radio or replace your old record a 3.50 -itltf trimmer should he used across of course, ordinary light which is being changer with a new Webster Model the ¡flute coil and tt 500 -futf trimmer used in a new system of relaying tele- 50. Drop in today and talk it over. across the oscillator coil.- Editor) vision programs. A cathode -ray tube is The oscillator trimmer is tuned un- used to transmit the television -modu- 10',', (DEPOSIT WITH ALL ORDERS7' til the carrier hiss is heard. Modulation lated light beam, and a photocell to re- is applied from a phonograph and the ceive it and turn it hack to electric im- plate trimmer adjusted for maximum pulses for retransmission from local volume. If the radio has a tuning indi- television stations. cator, the trimmer adjustment is made The light -beam technique, according for maximum needle deflection or mini- to Dr. T. T. Goldsmith, director of re- Covers the Globe mum shadow. An antenna less than a search for the laboratories, will make reduction in cost ARCH STREET yard long may be connected to the pri- possible a marked the 509 mary of the antenna coil. of inter -city television broadcasting, PHILADELPHIA 6, PA. The audio amplifiers provide more will simplify the sending of color, and LO 3 -0513 LO 3 -4559 than enough output to modulate the os- will improve the fidelity of telecast cillator fully. The oscillator was tested images.

42 RADIO -CRAFT for APRIL 1947 4t100481E0/0/Nedea910,/ THE NEW MODEL 670 sup E R MET E R eornbination

VOLT -OHM MILLIAMMETER

plus CAPACITY REACTANCE INDUCTANCE and

DECIBEL MEASUREMENTS

19dded 7ecztute: The Model 670 includes a special GOOD -BAD scale for checking the quality of electrolytic condensers at a test potential of 150 Volts.

2peciPcation9:

D.C. VOLTS: u tu 7.5v 15,75,150/750/1,500/ 7,500 Volts A.C. VOLTS: 0 to 15/30/150/300/1,500 /3,000 Volts OUTPUT VOLTS: 0 to 15/30/150/300/1,500 3,000 Volts D.C. CURRENT: 0 to 1.5/15/150 Ma. 0 to 1.5 Amperes RESISTANCE: 0 to 500/100,000 ohms 0 to 10 Megohms CAPACITY :.001 to .2 Mfd..1 to 4 Mfd. (Quality 7'hs Model 670 co arcs hoaxed in test for electrolyties) a.negged,crackle- /in alb edsteel cabinet complete with test REACTANCE: 700 to 27,000 Ohms 13,000 Ohms leads and operating instruc- s289 to 3 Megohms tions. Size 5'í" r 7'_" INDUCTANCE: 1.75 to 70 Henries 35 to 8,000 Henries DECIBELS: -10 to +18 +10 to +38 +30 to +58

PLEASE PLACE YOUR nRDER \\ I'l'H 1 i 11 R REGULAR RADIO PARTS JOBBER. IF YOUR LOCAL JOBBER CAN- NOT SUPPLY YOU. KI\UI.Y \\ IUTE Full 1 LIST OF JOBBERS IN YOl R SPATE WHO DO DISTRIBUTE OUR 1 \'1'R1 IIF: \'l'S Mt «I \U l ul Il nIlUF 11 I)IIiE(:TI.1 TO 15. SUPERIOR INSTRUMENTS CO. Dept. RC 227 FULTON ST., NEW YORK 7, N. Y.

RADIO -CRAFT for APRIL 1947 43 I'll Train You Quickly -at NEGLECTED SERVICEMEN Home -in Your Spare Time 7ln appeal for more service from the Distributor -to Make More Money in the Fastest Growing By E. H. EHLE' it Industry in the World! WHAT is the most important indoor plumbing unless we were con- tool or piece edustry? in fident that both repair parts and a the radio parts industry? The plumber were immediately available. soldering iron! Most indus- The same holds true. for electronic de- tries depend on certain fundamental vices. methods of connection: the plumber re- lies on screw threads; the electrical in- dustry clamps its connections. In our industry (with the possible exception of tubes to sockets) every connection nt:rst be soldered. Ghirardi's Recognition of the relationship of the number of soldering irons in use and the Famous RADIO length of time each is functioning to the volume of business done by distributors PHYSICS COURSE and parts manufacturers leads to a toolte you series of interesting questions and con- nf`. compleñc clusions. What are we, as an industry, r fie and it IS complete! doing to keep the soldering iron hot in operation? What are any of us doing to make certain that more parts are soldered in more places hourly? Over 70 distributors in 22 states agreed that: 1. The serviceman spends about half FOR BEGINNERS! his time -4 to 5 hours a day -at the No previous experience needed bench. Send coupon t,,,lny! Examine Ghirardis big. 2. Most servicemen could use addi- 972 -page RADIO l'HYSICS COURSE for five full tional personnel at the bench. E. H. Ehle, author of this article. days. See hu so titi o g.: nt hook at ONLY $5 Mr. can give you eentplet. basic training to pave the 3. Servicemen have an average of way for a brilliant future in Television. Radio. of them. Frequency Modulation. Facsimile. Broadcasting. about one week's work ahead The serviceman will grow to what- Communication. Servicing, Industrial Electronics, 4. Less than 10 percent are aggres- ever stature necessary, or, if the occu- etc. Prove to yourself that training doesn't need selling radio service. to be expensive to he really sively pation is established as a legitimate 5. Those who sell appliances probably community function with industry back- 9 OUT OF 10 RABE WRONGIN'T will go for the quick dollar when ap- ing, others will be attracted who can Actually, this fang nit book has given more pliances are available and consider the be counted on to do their share in the people their start iu Radio- Electronics than any relation." electronic era. One of the other book or course ever published. On an actual bench a "poor forthcoming survey among 817 men already in radio. 724 of Remember, these are averages, but best places to secure such trained man- them 9 OUT (W lo-- answered that Ghirardi'a averages exceptions -make up our power is from the ranks of the amateur RADIO PHYSICS COURSE is their choice as the -not finest, easiest to understand training on the mar- national volume of business. or-to define him more clearly -the ket slid far better than any other book or wants to work from Here again the industry as a rou rse th,- have ever seen! The serviceman hobbyist. 8:30 am to 5:00 pm, but he is in a fast - whole is neglecting a golden oppor- LEARN FAST! moving industry full of new ideas. He tunity. LEARN RIGHT! wants to see new products! Must he be The average man with a few extra . . as fast as you can read! forced to do so during his productive. dollars and a hobby works from 9:00 You'll be pleasantly sur- nrlsrd hoar RADIO l'IITBII's time? Or should distributors take a leaf am to 5:00 pm. He can't find time to e0I -RSE helps yml ma.t,, from the books of our most successful talk to a distributor about a rig or nhieel.c that other ennr.e, ,rkr a nnplie:nrd. merchants, and arrange to open at noon parts to buy. No one is available to help Inc e elth Basle Electricity and stay open till 10:00 pm once or or encourage him. In a very few in- 31111 pie r, II IIke. n athrough the en! he Itadio twice a week? stances is the distributor's "ham shack" Elertrnnles field. EnrvlhIng a look Is made etysta! clear. Nothing The serviceman wants an adequate open one night a week. Take at is Milted or condensed. You supply of parts. Has he had them? No! the other hobby stores in your com- buy It for only complete- ON OIR 110NEV RAPE Why are his inventories -and those of munity! They are holding their custom- GUARANTEE. You progress his distributor-lean? Because he and ers by merchandising methods geared as fast as spare mall ng tline permits, \!any siodrats hale the distributor recognize that some to customer needs. Are we? 9+nnpleted I t Ina M, s ', parts prices may be too high. If true, 78 pages. 505 illu.tl at 'sis Consider these facts: :unl 81,; c, -If I,.1 I. 'm,s- lie corrected. If not. l'i' the condition should 1. is a respected man in . The plumber , Iluec ', - "Id both distributor and serviceman should Y..,1 , la,.? his community who has a place of busi- be told, so they may rebuild inventories ness, operates his shop on a businesslike safely and have available parts on hand, basis, and isn't afraid to look his bank- Coupon the bench. MAIL ORDER -Rush thus saving man-hours at er in the eye. ur.t pc-47, aturrr.r HUI Books. Inc.. The sale of vacuum -tube devices will Mal,ise.a Ave., New York IG, N. Y. 2. The same is true of the filling sta- .rLnrI nl i5 ,sa. np fomlanl M1r I. expand only to the degree they can be l tion business, the electrical contractor, lall PHYSIC, corn, . .i. - Llu 0, . kept in service. Industrial and commer- In either :f' 11 the painter, the plasterer, the paper .:rl. ,e :, "J1 , dal applications for cl, etronic time- My.ay hanger, the carpenter, and a host of and money- savers nmct depend on the ether small businessmen. availability of standard repair parts 3. What you as a or Adore- and an organization of men who can are distributor use these parts intelligently and quickly your organization doing to: 24 hours a (lay. None of us would use (a) Provide adequate business and technical MONEY -BACK GUARANTEE ;Vice-President. International Itesistunce Co.. training to sers-icemen and would -be serv- Philadelphia. Penna. icemen7 44 RADIO -CRAFT for APRIL, 1947 r- lb) Select with care servicemen you sell? (e) Help those servicemen you do select to handle their operations on a businesslike basis? (d) Help them develop more business? le) Encourage the interest of a higher -type personnel in electronic service as a pro- fession? If) Elevate the standing of the service business to a professional status? 4. Are you training your salesmen to NEW `"` "`° help their service accounts in such prob- S lems as: ALLIED' M.OG (a) Proper stocking of repair parts. iT (b) Improved appearance of their stores. (c) Proper window and store decorations. I 0 Id) How to greet and handle customers. R le) How to go after the hundreds of thousands of radio sets requiring servire now. If) How to justify and get a loan at the bank. (g) Proper charge for repairs. Ih) Proper setup of shop including recommend- ed test equipment. (i) How to collect overdue accounts. These are but a few questions and suggestions concerning a rapidly de- EVERYTHING IN RADIO veloping business. I hope they will serve to stimulate further thinking and action FOR EVERYONE IN RADIO! which will benefit the service profession Send for FREE and the independent parts distributor, your copy of the handiest, most complete Buying Guide for Everything in and will accelerate the introduction and Radio! Packed with use of many new electronic devices. the latest, finest values in radio and electronic supplies ... parts, tubes, test instruments, communica- Condensed from the NEDA Bulletin. tions receivers, Ham gear, Public Address equipment, home radios, tools, books ... more than 10,000 items of nationally known, guaranteed quality ... the world's largest and most complete stocks. For faste.t service, expert help, lowest prices, depend on ALLIED! Send fir FREE Catalog now ... BRITISH AMATEUR CALLS American radio fans have curious ideas about certain aspects of British ham life. Even the Call Book blunders MORE THAN 10,000 ITEMS. Everything in radio and electronic supplies to serve the needs of engineers, servicemen, dealers, badly in referring to our "Districts" soundmen, amateurs, and builders. Complete stocks of all the based on the number contained in the leading makes. Guaranteed quality. Lowest prices. Get every allotted call signs. These numbers have thing you need from one dependable source- ALLIED- Radio's Leading Supply House for everyone in Radio! no significance, and thus it is possible to find G2, 3, 4, 5, and G all in the same town! Don't ask why! That's the way the Postmaster General issued them; HAM GEAR HOME SETS they started with the 2's and worked Earliest delivery on New 1947 radios up! latest communica- and radio -phonos. tions receivers, trans- Radios for radio Then again, there are the three- letter mitters and Amateur men! Handsome calls, another source of perplexity to station equipment. styles. Wonderful Timo payment plan; performance. Out- U.S. hams. Prewar transmitting licenses trade.ins accepted. Es- standing complete were issued without examination, other pert Amateur Service. line of radio values! than the applicant satisfying the Post- master General that he needed it for experimental purposes. If everything NEW P. A. EQUIPMENT. Entirely new line of complete Pack- was satisfactory, an A.A. (artificial aged Sound Systems for every public address requirement. New aerial) license was issued together with styling, new design features. Everything in amplifiers, speakers, microphones, accessories. New intercom systems. New proles. a three -letter call. This permitted play- sional -type sound apparatus. Everything for the Soundman! ing round with transmitting gear using an artificial aerial only. Further appli- cation was needed for a full radiating HANDY RADIO BOOKS HELPFUL license and this was CALCULATORS usually granted Radio Formulas and Data.. lac These radio reference aids provide valu after six months or so, following a code Dictionary of Radio Terms.. ..15e able data quickly: Radio Circuit Handbook.. 25e test. Radio Builder, Handbook 15e Panl!el Posistanr and Series Simplified Radio Servicing 10t Capacitance Calculator. No. 37- 960...25e Radio Data Handbook.. _ .. 25e A.A. licenses now have been discon- R -F Resonance and Coil tinued and applicants have to pass t ALL 6 BOOKS No. 37- 799... $1.00 Winding Calculator. No. 37 -955 25e tests. technical and code. Exemption may be permitted in either or both. if the applicant can produce recognized ALLIED RADIO CORP. qualifications proving his proficiency. FREE =° 833 W. Jackson Blvd., Dept. 2 -D -7 Many of the three -letter calls now tot Chicago 7, Illinois ALLIED tht. air are prewar A.A. license holds r.- Send FREE 1947 RADIO CATALOG who do not have to take the technical Cl Send Books checked above 1 test. Send 6 Books No. 37 -799 `.g enclosed Send Calculators checked above RADIO The examination consists of a 3 -boor paper set by the City and Guilds or Name cíe ,Radio London Institute, and is held periodical- £cre'z ly at a number of centers throughout Add,. a cd E11ectzew ea the country. In the first, 145 of the 189 candidates passed.- R.F,.G. Coop. ..City ...... Zane Crate

RADIO -CRAFT for APRIL, 1947 45 HEAT -OPERATED "RADAR" THE idea of using heat radiation to detect the presence or approach of a body was presented to the Patent Of- fice in April, 1934. A patent for it was recently issued to Harold A. Zahl of Fort Monmouth, N. J., who has assigned it to the U. S. Government as repre- sented by the Secretary of War. The IMITATION .. . length of time involved suggests that SINCEREST OF this idea may have been kept as a war secret for some time. FLATTERY The detection of a target by heat - wave radiation seems entirely feasible. The greatest distance known to have

The true worth of ' VOMAX" been covered by radio waves is only is proven not alone by over- from the earth to the moon and hack, whelming preference by service technicions, by research labor- whereas for a number of years astron- atories. It gets top rating omers have measured the heat radiation through the copying of its new from stars too distant to be visible. inventions by at least four manufacturers! No imitation Heat radiation is indicated by a ther- provides the ronge, utility or mopile which consists of a large num- universality exclusive to "VOMAX ". Recognized by ber of thermocouples in series. Either those "in the know ", sales of antimony and bismuth or bismuth and "VOMAX" for exceed those silver are sensitive couples. It is pos- So superior as to be imitated, "VOMAX" stands unequalled. It of any would -be competitor. sible to measure a less than .000001 -de- alone gives you the astronomically high meter input resistance so So, cost to you of the genuine, necessary to servicing AM, FM and TELE receivers - a feature original "VOMAX" is from gree change by suitable circuits. Ordi- not attained by imitations. Add a total of 51 voltage, current, 10% to over 05% lower than narily the thermopile works into a sen- resistance and db. ranges. That's why "VOMAX" is the over. its imitations. Only $59.85 net. sitive direct-current meter, but when whelming choice of experts - be it for use or copying. Can you afford less than the best -- when the best cosh you least? the d.c. is interrupted and amplified much greater sensitivity is obtained. To eliminate the background of am- bient temperature which would be meas- ured otherwise, Mr. Zahl has conceived the idea of using two similar thermo- piles to buck each other. Therefore. "SPARX" when no heat -emitting or heat -absorbing body is present, the indication is zero as shown in Fig. 1. The two collectors are parabolas resembling microwave 2). "QUICKEST TROUBLE radar antennas (Fig. FINC:R EVER" says I. P. FITZGERALD

. of his new "SPARX" visual -aural dynamic signal tracer, writing front

Madison, Wisc.: " . cannot afford to be without this valuable instrument one minute. It is the quickest trouble-

finding apparatus I hove ever used." To repair any rodio you've first gat "SPARX" is the some greet "buy" at only $39.90 as to find the trouble. "SPARX" will lo. "VOMAX ", world's most popular, most copied, universal HEAT WAVES cate r.l., i.1., a.l. trouble in 30 seconds uum -tube voltmeter. Of matching size and style. per tube! Think what that means in thousands in use prove its vital worth to every service profits to the thousands of your corn. technician interested in guarding his profits. "SPARX" petitors already using "SPARX ". It troces signals through a receiver from antenna to Speaker, points, both audibly will boost your profits, too . . circuit by circuit, locating trouble and visually. Its speaker switches to panel jacks for shop test use - another SILVER plus- value.

Send Post Card for Catalog for new measuring equipment, communication receivers, transmitters, kits, parts. See them at your favorite Jobber. 47

OVER 36 YEARS OF RADIO ENGINEERING ACHIEVEMENT The presence of a body is indicated in one of two ways: either through di 7&"7744.1d-.5'44. rect radiation from the body, such as a smokestack of a ship (See Fig. 3.) or 1249 MAIN ST., HARTFORD 3, CONNECTICUT through absorption of temperatures when the reflector is aimed at sky, landscape or sea.

46 RADIO -CRAFT for APRIL, 1947 The waves detected include those of infra -red frequencies, and the method is effective at night, during fogs, etc. ...THE NEW TURNER The possible range is equal to that of radar u.h.f. systems. A disadvantage of heat detection is MODEL 20X HAND MICROPHONE that the distance of the object is un- known unless two stations are used and triangulation resorted to. On the other hand, this method is far more simple and less costly than radar.-I.Q.

AVAILABLE LITERATURE You may secure copies of these bul- letins simply by listing their numbers on your letterhead (do not use post- cards) enclosing remittances where necessary, and mailing to Available Literature, c/o RADIO -CRAFT, 25 West Broadway, New York 7. This saves the work of writing separate letters to each manufacturer.

265 -RADIO SYMBOLS GUIDE A two -page pamphlet prepared and distributed by Sun Radio and Electron- ics Co. It reproduces symbols that have been standardized by the ASA and in- cludes symbols for such late electronic developments as velocity modulated tubes, and magnetrons. -Gratis 266- STANDARD RATE BOOK a little mike A booklet suggesting standard rates for radio servicing, based on Chicago. Published by Oelrich Publications. Labor is calculated at $3.00 per hour, and various bench and minimum with a BIG future charges suggested. Of the 44 pages of the booklet, 26 are devoted to proposed We're mighty proud of this new addition to the line of Microphones charge schedules for various types of by Turner. Small in size yet big in performance it inherits those radio apparatus, with listings of gener- qualities of sound engineering and careful workmanship that have al service $1.00. to be performed.Price made the name Turner a symbol for precision and dependability. 267- ELECTRON TUBE GUIDES The New Model 20X is designed to appeal to owners of home Two 15 -page tube guides are pub- recorders and amateur communications equipment. It has innu- lished by RCA. Form PG -101 gives merable applications in offices and factories and for paging and call characteristics and tube -base connec- tions for transmitting-type power am- system work. Sound pressure tests reveal remarkable performance plifiers as well as voltage regulators, characteristics for a low priced unit. Its circuit features a Metalseal , ignitrons, and gas rectifiers. crystal which withstands humidity conditions not tolerated by Form No. 1275 -C lists socket connec- the ordinary crystal. Response to voice and music is smooth and tions and characteristics of receiving - flat within ±5db from 40 -7000 c. p. s. Level is 54db below I type tubes and some kinescopes. Light - face type is used on tube designations of volt /dyne /sq. cm. Finished in lustrous brown baked enamel, the discontinued tube types to indicate those Model 20X is light in weight and natural to hold. It may be hung tubes that soon may be obsolete.-Price on a hook. Furnished complete with 7 ft. attached shielded cable. r 10 cents each. CORRECTION WRITE FOR BULLETIN An error appeared in the diagram of the "Multitester" Plus V.T.V.M." on page 83 of the January issue. The dia- THE TURNER COMPANY gram shows the center terminal of the 902 17th Street N. E. Cedar Rapids, Iowa lower section of Swl connected to J1. This connection should be open and the line from Jl connected to the right - hand terminal of the lower section. This terminal was shown open on the orig- inal diagram. BY TURNER In the third paragraph of the first column of the same page, Swl is called a d.p.d.t. switch. This is actually a double -pole three-position switch. "THE PASSWORD TO SOUND PERFORMANCE" Our thanks to Mr. Joseph Jahoda, of LICENSED UNDER U. S. PATENTS OF THE AMERICAN TELEPHONE AND Maspeth, N. Y., for calling our atten- TELEGRAPH COMPANY, AND WESTERN ELECTRIC COMPANY, INCORPORATED. tion to the error in the diagram. CRYSTALS LICENSED UNDER PATENTS OF THE BRUSH DEVELOPMENT COMPANY.

RADIO -CRAFT for APRIL 1947 47 r nlnnnnnnnnnnimmum nnmmn mm uomo; inuuunmmunmminuntimmminnunuimininimmmmmlwtnuminnmmno mimmwm

Question Box queries will be answered by mail and those

of general interest will be printed in the magazine. A fee

of 50c will be charged for simple questions requiring no

schematics. Write for estimate on questions that may require diagrams or considerable research.

hq'a.eA 041- 6- the 6H6 as a.v.c. rectifier and add a 6U5 tuning. indicator. H.R.E., Toronto, should serve your purposes. The 1 -ltf - paper condenser charges at a rate de- Canada. BATTERY ELIMINATOR termined by the setting of the 500.000 - A. The circuit shown has been drawn to your specifications. If the 6U5 over- Please print a diagram of an a.c. 6K6-GT loads on comparatively weak signals, d.c. power supply to be used with o LI try connecting its grid to the opposite Phi(co Model 37 -38 battery receiver. 003 .01 500K II side of the 500,000 -ohm resistor. The filament drain is 0.72 ampere at 2 volts. The high- voltage supply should 7K -l0Kn. UTPUT TRANS COIL DATA give 135 volts tapped at 90 volts. The 30 MA current drain is 20 ma. Bias require- 10/25V. Please print coil dot,, for the 1 -tube ments are 3 and 9 volts.E.P.R., Cin- set on page 467 of the :l grit 1946 issue, cinnati, Ohio to cover the broadcast band with a 365 - .5W NEON /400v. 50015 TIMING CONTROL B.A.G., Tuscaloosa, TI lItf condenser.- A. Here is a power- supply circuit that Ala. has been drawn to your specifications. 13.75 MEG Filament voltage is supplied by con- A. The loop antenna may be wound 6.3V /IA.TO 656 -GT 5H with about 50 turns of No. 16 to No. necting a dry -disc rectifier across the ow000 output of a 6.3 -volt 1- ampere filament 000 22 insulated wire. It is assumed that AC-DC CH+ you are using a case which would give transformer. CH 1 is made by removing frs the windings from a small choke and 20_ a loop size of about 3 by 4 inches. Turns 450v.. replacing this winding with as many SW. ó 240v. may be added or removed to get proper >40MA coverage. The feedback is made turns of No. 22 enamel wire as can be 111 KAC tap at 240V. 80 wound in the core space. A 2 -ohm vari.- ó a point between 12 and 16 turns from able resistor permits the filament the grid end as required to give stable voltage to be adjusted to 2 volts. ohm timing control. When the charge regeneration. The other tuned circuit on the condenser equals the ignition may use a standard r.f. coil. fl7Z4-GT of the neon bulb, the bulb ignites 25 voltage +I V. and discharges the condenser. The 1,000 -CYCLE OSCILLATOR II71LA CH2 10K ADJ FOR B+90Vu again and will charging cycle begins I would like to have a, diagram of 4- and it continue indefinitely. The charging a simple 1,000 -cycle oscillator to use will react on the SMt 40 10K W. 20 discharging surges with the Electronic Multichecker de- 6K6 to produce 150V. 15016 grid circuit of the scribed in. the 1946 Radio Electronic audible pulses with a tone determined 05 40 Reference Annual.- C.J.H., Kansas the 600V. 250V. 00 BC+ by the inductance of choke and City, Mo. of the shunting condenser. 55 capacity 10K 13+300K 25K C 3K may be any high - f 1 The tone choke Ll 6J5 6 IOW. ADJ.fOR U1V.AC AUJ.FOR 9V. 3 C-9K. impedance a.f. choke or one winding of 1--1450v. FIL.TRANS CHowomI 2ADJ.FOR 2V. an old a.f. transformer. If your power TI J WK CONNECT AT FIRST V transformer does not have a 6.3 -volt 16u1 COND.NEAR winding, a small filament transformer 60 TUBE so 1000.2000 should be used. ú o 00 Il oc I aII W 3v. 3v. I KC NOTE T0 BRIDGE I TRY ANY I AMP. DRY RECT. .] TUNER ALTERATIONS 2 Was) ALL F NAL VOLTAGE ADJ. MOST BE MADE AT FU41. LOAD A I ant planning to construct the hi -fi A. Here is a circuit of an oscillator Variable controls are provided for f...i. tuner described on page 401 of that may be used as a source of 1,000 - adjustment of intermediate B -plus vol- the March, 1946 issue. Can you si ggest cycle current. The value of Cl will de- tage and bias voltages. All adjustments a means of replacing. the detector termine the frequency of the tore. If the should be made under load. with a 6J5 connected as an infini e im- inductance of Ti is 25 henries, the Many of the exposed metal parts of pedance detector? I would like to etain oscillator will tune to the required fre- this eliminator are live and should be 3RD quency with a insulated from bodly contact. Do not 0.001 -pf condenser 6SK7 0o5 5 , 6H6 6J5 c76,6P5, ETC.7 use an external ground on the receiver OF UNFIT- for Cl. connected 47K ( SO 1.0001 e unless a blocking condenser is IVL l OK T1 may be a in the ground lead. push -pull inter - L 1.453 stage transformer DARKROOM TIMER 6+2704. one designed to I would like to have a circuit show- .25 couple a pair of ing how I may construct a. visual and 2oK push -pull plates to audible tinter for use in a darkrooms. It'1 a AVC 500K universal line. I have a small a.c. power supply that IOOK TO AUDIO AMP. Any two leads on delivers 240 volts at 40 ma. Can this be the output side of used to supply power for the timer? - t h e transformer F.D., Jersey City, N. J. may be connected A. Here is a diagram of a timer that to the bridge.

48 RADIO -CRAFT for APRIL 1947 NEW! CRYSTRON LAPEL RADIO (Continued front page 25) áry MANES 90001 OF 100 RADIO The converter tube, like the types, is a multi -element device TROUBLES Easy to Repair! A small Columbite rectifier crystal in its control -grid circuit rectifies the in- Complete, Easy Instructions for Repairing coming signal and permits it to modu- Common Troubles in Practically Every late the oscillations produced in the tri- Model and Make of Radio in Use Today ode circuit. The oscillator is a modified Hartley, with plate at r.f. ground potential. Be- Eliminates Needless Enables cause a condenser direct from plate Testing- to ground produced too strong oscilla- You to Repair Two Radios in the Time tions, it was tapped off at a point on Ordinarily Required for One the plate resistor determined by experi- What's wrong with the radio you want to repair? A defec- ment. tive transformer^ Wiring insulation trouble? A faulty capacitor or resistor? Don't guess I Don't waste time is After mixing in the converter, the needless, tedious testing! Just look up that particular make signal goes to second tube, an i.f. and model in Ghirardi's famous RADIO TROUBLESHOOT- the ER'S HANDBOOK. Nine times out of ten, this big book amplifier hooked up in a bridged -T will tell you exactly what is wrong -and exactly how to circuit, which is tuned very sharply to repair it. You don't have to be an expert to use the TELLS WHAT HANDBOOK- and there's no better way of getting in- 100 kc. Gain measurements with a valuable. practical service training, vacuum -tube voltmeter are hard to make TO DO EXACTLY because the meter loads PAYS FOR ITSELF ON THE FIRST JOB! the high- resist- HOW ance circuits, but the stage has a gain TO DO IT Over 40 pages are chock -full of this factual Case History of at least 100 and may be nearly twice As valuable to a radio repair data on over 4,800 receivers, auto radios and record repair man as a recipe ehangera of 202 different manufacturers- practically every that. The measuring difficulty is prac- radio set in use today ! Over 300 additional pages contain tically the same as that the serviceman book is to a hundreds of repair charts. tube charts, data on tuning cook! alignment, transformer troubles, tube and parts substitu- experiences in ordinary receiver circuits tion data, color codes -all designed to help you repair any with the old 1,000- ohm -per -volt meter. 74' bin, man. radio ever made EASIER, BETTER and FASTER. Ideal for unl -size pages! either busy service shops or for be- The power amplifier has a larger ra- ginners. Only $5 complete -on our dioactive element in its crystode, and 5 -Day Money -back Guarantee basis. has a lower amplification factor and DO EVERY JOB EASIER, BETTER, FASTER internal /e" resistance than the other tubes. Ghirardi's RADIO TROUBLESHOOTER'S HAND- I revived the almost- forgotten con- BOOK (above) is the ideal book for training new denser speaker for the little radio. This helpers, repairing either cheap or expensive sels (Continued on page 67) quickly and profitably, eliminating needless test time and equipment -and MAKING MORE MONEY. ;6 MORE SMASH BUYS at National Radio Distributors' ALL THE SCIENCE OF RADIO - FAMOUS NATIONAL RADIO KITS GIANT B00K' NOW -Immediate Delivery from ELECTRONIC SERVICING stock COMPONENT PARTS MOUNTED ON CHASSIS FOR EASY WIRING LEARN AT HOME without an Instructor All Radio Kits complete. Including ... beautiful plastic cabinet. built -nt Alfred A. Ghirardi's MODERN RADIO SERVICING loop antenna, new Alnico xpcuker. Pages and full inatnartlons for assembly. gives you a COMPLETE, MODERN EDUCATION in truly 1300 For 110 -125 volta AC /DC.e professional radio -electronic service methods of the kind Over 500 White Plastic Cabinets now ail:ld... 51.00 ad.l ti!nal. that be the big -money op- illustrations! MODEL N.R.-7-6 TUBE SUPERHETERODYNE. use. 12SA7, will your "Open, sesame!" to 125157. 12SQ7, SUIS A 35%5 tube.. Your bet 511.05 portunities that only well -trained servicemen are in a posi- Kit of 3 Matched tubes Your net 4.50 MODEL M.R. -5-S TUBE "TWO BAND" SUPEItHETF]t0- tion to grasp. It is a complete, scientific servicing course ENDORSED BY EXPERTS DYNE. uses Tubes as above. from A to Z. You'll be surprised how easily understandable RAND 1- 330/1600 K.C. Rand 2-0/18 Megacycles MODERN RADIO SERVICING brings Your net 513.95 it makes every phase of the work even if you have had no Kit of 5 you the kind of professional "Know Matched tunes Your net 4.50 are in the MODEL M.R. -5-6 TUBE SUPERHETERODYNE, uses 2- previous service training. And, if you already How" that will pay big dividends for 12SK7, 12SA7, 125Q7. 35E6 A 3535 tubes. business. you'll be learn big 1300 -page r pleased to how this years to come. Covers test instruments Kit of 0 Matched t otes Yournnet51 5.50 book will serve as a "refresher" course. Not only will it MODEL N.R. -1-4 and their use, trouble TUBE T.R.F., uses 125E7, 125.17. help you handle repair jobs quicker, better and more preliminary A 35Z5 tubes. Your net 510.95 checks, scientific circuit analysis and Kit'oLeof Matched tubes Your net 3.50 Profitably, but it also will give you the necessary basic THIS MONTH'S SPECIALS trouble -shooting, parts repair and sub- RADIO TUBES, R.C.A.. training to equip you for profitable industrial electronic Kent-ad. National Union. Sylvania. how a successful 1 : 1A7OT. 9.99; 117L7, $1.81; SoLo. 5.83; work. Specifically written and designed for home study. stitution, to star; 2525. tubes alabl: service business and hundreds of other MAO. 151.81. hese and oiherJhaid.to.ge RVL tubes available 1300 pages ; 706 clear illustrations. 720 Self -Test Review now. Questions make it easy for you to check your progress subjects. F.T.R. Selenium Rectlsers -75 mn. Ea. 5.88. 0.49 Ea. 5.80. SPEAKERS: 4^ r 5- P.M. Alnico Y Ea. 1.49. 6^ P.M. even' st.p of the way. Fully indexed. Only $5 on our Alnico V. Ea. 51.95. Case lots of 20 deduct tory. CONDENSERS: 100 Am,' by-pass tubular tree q.r Taman. f. In,,. I, nev -hark G,larnnit.._ condensers. .00025 to 1 mfd. Absolutely fresh stork. Ì rutty guaranteed: all 600 volt. Net 53.uá. PROMO MOTORS: Rim drive. self.starting. 0^ turn.tat.l.- for 110 V. AC. Alliance Ea. $3.75. Itunsell Dallautl'v MONEY -BACK GUARANTEE Ea. $4.28. VOLUME CONTROLS: All sizes: from 5.000 ohm to Megohms, WITH /WITCH. Ea. 5.59. 10 f, -r $5.50. HURRAY HILL BOOKS. Inc., Dept. RC -17, PORTABLE RECORD CARRYING CASES: Tab index; hold, 50 records. Fa. $2.25. ,, 232 Madison Ave., New York 16, N. Y. PORTABLE RECORD CARRYING CASES: Slid Wood coo. struction; leatherette covered. With index: holds ro ?,closed find for books checked: or CI send records) brasa t SPECIAL OFFER! Sturdy fittings; with lock & key. ti i). (U.S.A. only) for this a uouat I filas' Ea. $4.30. Plus postage. the btldts refund within 5 days if not fully ROILER CORDS: 6' Hugh & Low sides. Heavy duty ty'p.. rrwrn for Let TROUBLESHOOTER'S for all type broilers. Ea. 5.69. 10 for $,1.50. +.alsfird. AUTO ANTENNAS: 3 ection 0Ìi^ long. A triple chrome.) n RADIO TROURLF.SIIOOTER'S HANDBOOK 15 HANDBOOK save you time Admiralty brass finish. L,nv bras lend. List 54.11(5. fon'ignl YOUR NET Fa. $1.79. Lots of 3 ,':a. $1.75. (55.50 on common service jobs! Let E SSILO SOLDERING IRONS: 65 Watt. Plug Tip Ea. $1.55 n MODERN RADIO SERVICING 15 ($5.50 foreign) Ìo0 Watt. Plug Tip. Ea. 52.35 n MONEbY -SAAoV IINGCOMBIdNA SION SOFoFER: Both of the MODERN RADIO SERVIC- for NEW FREE out. atte Pinse send least order. We will ship balance ING train you for complete C.O.D. We ship all over the world, usually me day as order is received. Cable address: Enardee. N. Y. work. Name, professional, electronic Get BOTH BIG BOOKS at National Radio Distributors Address the special price of only 59.50. City & Dist. No. State Send coupon today! 899 r Southern Blvd., New York 59, N. Y. RADIO -CRAFT (Cr ,APRIL, 1947 49 RA010ELECTROIIIC DEVICES

FM -AM TUNER ELECTRONIC MULTIMETER Browning Laboratories, Inc. Hickok Electrical Instrument Co. Winchester, Mass. Cleveland, Ohio The Model RJ -12 FM -AM tuner is The new Model 203 electronic multi - designed for high -fidelity reception in meter measures wide ranges of capacity, the new high- frequency FM band as resistance, inductance, a.c. and d.c. L well as the standard broadcast band. voltage and current. The d.c. and a.c. ARMY RADIO PHONES Separate r.f. and i.f. systems are used Thay'ra Waathar -Water and Shock Proof for both bands. The r.f. section for FM When we say they are made to Army specifi- uses miniature tubes. The tuning range cations, that's enough assurance they must be on FM from 87 to 109 of best quality. These Army Radio Phone' the band extends are perfect and were O.K.'d by Signal Corps megacycles and on the broadcast band Inspectors. These Dynamic Mikes and Re- 1650 kilocycles. The Arm- ceivers, were used on aircraft and tank inter- from 630 to communication systems. Use them for record- strong circuit employed in the FM sec- ing, for hatteryless phone, for pocket size set uses cascade limiters to ensure loud speaker or talk through your radio set. tion two We bought a good many of these Radio Phones, maximum noise rejection. Bandwidths they are brand new, and cost a great deal such high - more than you can them for. of i.f. amplifiers are that A complete dynamic hand mike, fidelity audio output is realized. A stage 2 earphones, headband, cord set of ri. is used on both FM and AM. A wonderful buy for only One Antenna is used for FM and AM. G.E. 1/25 Watt neons With wire leads or impedances are 15 megohms and Min. Bayonet Base. Specify. 10 for 80c input J -37 Telegraph Key Pik" Contact 69c 12 megohms, respectively. Voltages, a.c. Co -ax Cable 52 ohm per "C" ft, $4.50 and d.c., and milliamperes, d.c., are NATIONAL =646 measurable in ranges of 0 -3, 12, 30, 120, POWER SUPPLY SELSYNS 300 and 1200. Resistances are measured VIBRATORTYPE in seven ranges from 1.0 ohm to 10,000 Input 6VDC, Out- 115VAC Type 5 put 165V 50 Ma. megohms. For your Battery per pair $5.00 or Mobile Receiver Operating from a 105 -125 volt a.c. List price $56.93 115VAC Type II -1 line the power consumption is 20 watts. Your cost 9.95 per pair $9.00 Five tubes are used, including two rectifiers and a voltage regulator...-. OHMITE Adjustable 50 Watt 25 OHM Re- sistor 15e RADIO-CRAFT 10 FOR $1.25 Circuit Breakers -Heineman Magnetic, 115 V.A.C. Choice of 5, 7, 20, 35 amps each 95c PLASTIC EARPHONES 0 -1 Ma. McClintock 2" Bakelite Meter $2.15 0 -3 Ma. Gruen 2" Bakelite Meter 1.95 Telex, Inc. NATIONAL ACN Dials $2.9s The dimensions of the tuner exclusive Minneapolis, Minn. NATIONAL XR50 slug tuned Coil Forms 1.00 of power supply are; height 7%, width NATIONAL AR2 75 The Monoset is worn under slug tuned to 220 13%, depth 9 inches. The power supply Telex the me Coils 1.70 chin rather than over the head. De- NATIONAL AR5 slug tuned 37 to 110 is a small separate unit. -RADIO -CRAFT me coils . 1.45 signed like a stethoscope, the set has OIL CONDENSERS two hollow tubes stemming from a tiny 10 MFD 600 V.U.C. Cornell Dubilier 5 ,98 MIDGET VOLUME CONTROL round speaker and adjustable to the 2 MFD 2000 V.D.C. Cornell Dubilier ...1.75 8 MFD 1500 V.U.C. Aerovox 3.25 Centrelab, Div. of Globe- Union, Inc. IO MFD 1500 V.U.C. Cornell Dubilier 3.45 Milwaukee, Wis. 0.1 MFD 7500 V.U.C. Aerovox 1.50 IN 23 XTAL DIODE 3 for 5Ic The Model 1 Radiohm is specifically 4,112 Black Crackle Steel Cabinet. Removable designed as a high -quality volume at- top and bottom complete with screws....49c 10 FOR $4.00 tenuator for hearing aids, pocket radio receivers and miniature amplifiers. It FREE and RATE GYRO is smaller than a dime and is designed to accommodate many variations in specifications. It is a perfect companion for sub- miniature tubes, batteries and other components. The new unit will be available in 500-ohm to 5 -meg sizes. Other features are three mounting

Schwein 24 Volt Gyro. Complete in case, $5 .00 proper head width. The ends are tipped If not rated 25% with order, balance C.O.D. with clear plastic earpieces which fit All prices F.O.B. our warehouse New York. No order under $2.00 directly into the ears. We ship to any part of the globe The entire unit, including speaker and miniature plug -in cord attachment, LEEDS RADIO CO. weighs only 1.2 ounces. This device can positions, optional cam for external be used in practically any application 75 Vesey St., Dept. 45 switch and internal rotation stop. - where conventional earphones would be COrtlend 7 -2612 New York City 7 RADIO-CRAFT employed. -RADIO -CRAFT

50 RADIO -CRAFT for APRIL. 1947 RADIOMEN'S HEADQUARTERS it WORLD WIDE MAIL ORDER SERVICE ! ! ! SERVICEMEN GENERAL ELECTRIC RT -1248 15 -TUBE Check This Column for Lowest Prices on Quality Parts TRANSMITTER -RECEIVER TERRIFIC POWER watts) on any TUBES: A warehouse full. Including the new miniatures. -(20 two instantly selected, easily pre -adjusted fre- order all types yell need. We'll try to bunny you completely. quencies from 435 to 500 Mc. Transmitter uses 5 tubes including a Western Electric 316 A Special this month: Sylvania 6Vfigl -3 for $2.00; RK -75 or :07 ae final. Receiver uses 10 tubes including 955's, as first detector and oscillator, and 3- uumilting tubes only $2.50 each: 6LOG-99e; 68D7 teenier," ,K7 -59c. 7 H7's as IF-'s, with 4 slug -tuned 40 Mc. IF transformers, plus a 7H7, 7E6's and 7F7's. In POWER TRANSFORMERS-Half -shell type. 110V. f,0 ey. addition unit contains 8 relays designed to operate any sort of external equipment whr n Centertapped 11V winding. Specify either 2.5 or 6.3V fila- actuated by a received signal from a similar set elsewhere. designed 12 ment when on.ering. Originally for For 4.5 tube sets -650V. 90MA, 5V & 2.5 or 6.3V $í.49 operation, power supply is not included, as it is a cinch for any amateur to connect For 5 -6 tube acts -6;01', 455L'.. 5V & 2.5 or 6.3 t 1.75 unit for 110V AC, using any supply capable of 400V DC at 135 MA. The ideal unit for 1: For 6 -7 tube sets -675V. 5o51Á, 5V & 2.5 or 6.3V 1.9.) in mobile or stationary service in the Citizen's Radio Telephone Band where no license For 7 -8 tube sets -700V, 70MA. 5V & 6.3 or two 2.5 2.35 For 9 -11 tube sets 700V. 100MA. 5V & 6.3 or two 2.5V 2.85 necessary. Instructions and diagrams supplied for running the RT -1248 transmitter For 9 -15 tube sets-6oOV, 150. A. 5V & 63V 2.95 either code or voice, in AM or FM transmission or reception, for use as a mobile pun.. TRANSFORMERS--All types in stock. AUTO.TRANSFORM- address system, as an 80 to 110 Mc. FM broadcast receiver, as a Facsimile transmitter ERS; Step. up 110v to 221.1v. or steps bowri 220v to IIOv- $1.95. FIL. TRANS.: 6.3e, 8 Amps.- $1.96: 5v, 10 Amps. -- $1.98; receiver, as an amateur television transmitter or receiver. for remote control relay hook- Universal Output Trans. R Watt -89e: 18 Nett- $1.29; 30 Watt UPS. for Geiger -Mueller counter applications, and it sells for only $29.95. 10% less if or- $1.69. AUDIO TRANSFORMERS: S. Plate to S. Grid. 3:1- dered in lots of two or more. desired marine 78e: S. ''late to P.P. Grids -7k; Heavy Duty Class AB or If for or mobile use, the dynamotor which will It. P.P. Inputs -$1.49: Midget Output for AC -DC sets -69e: work on either 12 or 24V DC and supply all power for the set, is only $15.00 additional. MIKE TRANSFORMER for T -17 Shure microphone, similar ouncer to UTC Ups- $2.00. BENDIX SCR 522 -Very High Frequency Voice Transmitter- Receiver -100 to 156 MC. This M:CROPHONES -All typa. nationally known brands. Bullet job was good crystal- 45.45; Bullet Dynamic-- $7.45: Mlle Jr. -60o; 'tan,. enough for the Joint Command to make it standard equipment in everything )like -9e0; Lapel Alike -93e; Shure T-17 Mikes, with push to that flew, even though each set cost the Gov't. $2500.00. Crystal Controlled and Amplitude Ik Itch- --99e. Modulated -HIGH TRANSMITTER OUTPUT and 8 Microvolt Receiver Sensitivity gave CONDENSERS -PAPER TUBULAR 800 WV-. 001- Be:.002- good communication up to 180 miles at high altitudes. Receiver has ten tubes and trans- 8e: .U15 -8c; .01 -9e: .02 -9e! .05 -1Oe: .1 -10e; .25 -23e: mitter has seven tubes, including two 832's. Furnished complete with 17 tuba and four .5 -38e; ELECTROLYTICS: 8mfd. 200v -20e; lOmfd. 35v -20c: crystals for $36.00. Dynamotor is $8.50 additional. None Bold without dynamotor. We 30m fd. 150v-23e: 20 /2u mfd. 150v --35e : 30/ tom f d. 150v -46e: in- 50mfd. 150v -43e; 8mfd. 475v -35e; 16mfd. 339v -65e: OIL- clude complete diagrams and instructions for the simple conversion of the 622 to 110V AC CONDENSERS: 9m(d. 800r -49e. oicr tir.n. FILTER CHOKES: 200. 300. 900. 500 ohm light duty-595: 200 or 300 ohm heavy duly-99e; 250 MA. 35 ohm, made for Ü.B. Navy, fully sldeided -$1.95: 75 duo. 125 MA -25e. or 25 tar $4.25; 8 amp. iron core A- filter -25e. GENERAL ELECTRIC 110 V. CIRCUIT BREAKERS of Magnetic type: Following Current Ratings In Stock; 1.25, 3, 4. 8 Amps. Please specify. $i.95. 150 WATT SEVEN ASSORTED I.F. TRANSFORMERS -$1.98; Foce Ass'l. Oscillator Coils -69e. TRANSMITTER PERMEABILITY TUNERS -- Attractive slide -rule dial. com- pactly repines dial. tuning conuonsers, oscillator and antenna cods in broadcast band receivers. Special $3.43. Cost the Government $1800.00 WILLARD rechargeable 2 volt storage batteries for O.E. pct-tabl- radios $2.95. Now only $44.50! SPEAKERS -PM dynamic type -4'- 41.55; 5" $1.55; 6 "-$I.95; it $3.95; 10"- $5.95: 12-- $7.50. CRYSh AL PICK -UPS-Two nationally known makes. one $1.90. This is the famous transmitter used in U.S. the o. her at 5229. Army bombers and ground stations. during PROMO- MOTORS -110V. 60 Cycle, with turntable- $4.25. the war. Its design and construction have HEADPHONES- highest quality Signal Cops headsets with been proved in service. under all kinds of sponge rubber ear cushions. l'Y cord and plug $1.00. 5' rubber conditions, all over the world. The entire frequency range is covered by means of seven coveted patchcords with phone plug and socket -25e. plug -in RELAYS -Guardian SP ST 12 -29v. has heavy duty 15 Amp. tuning units which are included. Each tuning unit has its own oscillator and Contacts- $1.25: Guardian 13 to 24v D.C. triple make. single power amplifier coils and conden,ers, and antenna tuning circuits -all designed to operate break relay, 5 for $3.75; Sigma supersensitive 2000 ohm D.C. at top efficiency within its particular frequency range. Transmitter and accessories are SPDT Itelay. (May be adjusted to upstate on less titan 1 finished in black crackle. and the milliammeter, voltmeter. and RF ammeter are mounted M illiamper 1- $2.50. on the front panel. Here are the specifications: FREQUENCY RANCE: 200 to 600 KC 6. Type 2000 POLE. DOUBLE THROW. Telephone ohm Re- and 1500 to 12,500 KC. operate on 10 and 20 meter band lay.. Super Sensitive, $2.50 each. or two for $4.50. (Will with slight modification). compensated, 1 SELENIUM RECTIFIERS-Drs disc type l%" by 1 ". ].2 OSCILLATOR: Self -excited. thermo and hand calibrated. POWER AMPLI- Amp. maximum. suitable for converting DC relays to AC. for FIER: Neutralized class "C' stage, using 211 tube. and equipped with antenna coupling suppb'Ing filament source In portable radios. converting DC circuit which matches practically any length antenna. MODULATOR: Class "B" -uses meters to AC applications, and also may bo used In low current two 211 tubes. POWER SUPPLY: Supplied complete with dynamotor which furnishes rlmrgrs- -90e. 1000V at 350 MA. Complete instructions are furnished to operate set from 110V AC. METER RECTIFIERS -Full ware. may bo used for replace- ment. or in construction of all types of test equipment$1.25. SIZE: 21 %F1x2389% inches. Total shipping weight 200 Ibs., complete with all tubes, dyna- I lull Wane -90e. motor power supply. seven tuning units, antenna tuning unit and the essential plugs. FILTER CHOKES -200. 300. 400. 500 ohm light duty -59a: These transmitters are priced to move fast: Order today and be the proud owner of one 200 ohm hvy. duty -99e; 250 MA. 35 dams DC res. Made for of the finest rigs obtainable. U. S. Neu. Fully shielded- $1.95. LINE FILTERS-110V-each unit rentable two 2 mfd. oil Oiled condensers and a 15 amp. Ir,sh core choke. This filter has Innumerable uses such as oil burner line filter. etc. A ten 6 -BAND COMMUNICATIONS RECEIVER dollar value for 98e. PHONO AMPLIFIERS-A real AC, 110V. 60 Cycle. 6 Watt BC Amplifier suitable for PA systems and phonographs; with -348 husky power transformer. Complete with tubes- $12.95. Featuring coverage from 200 to 600 Ec. and 1500 to 18.000 Kc. on a direct reading dial PUBLIC ADDRESS AMPLIFIERS -25 Watts peak output. 5 with finest be tubes. separate controls for 3l1crophone and Phone Inputs. the vernier 'drive to found on any radio at any price-extreme sensitivity $85.00 value for only $32.00. with a high degree of stability- crystal filter -BFO with pitch control -standard 6 volt tubes. Contains a plate supply dynamotor in compartment within the handsome black WIRE -NO. 18 POST, 2 conductor parallel zlpcord, brown. 250' pools- $5.25. 500' spools-$9.45. No. 18 PO brown rayon crackle finish cabinet, the removal of which leaves plenty of room for installation of a emoted parallel lampcord, 500' spools -$12.25. No. 18 SV 110V, 25 or 60 cycle power supply. These receivers, which make any civilian communica- round rubber covered double wire for wash machines. vacuum tions receiver priced under $200.00 look cheap and shabby by comparison. are only $44.50. cleaners. etc. 250' spools$O.95. Rubber covered mike cable Power supply kit for conversion to 110V, 25 or 60 cycle. is only $8.50 additional. 250' Spools -$25.00. All kinds hook -un wire le per ft. Single stranded conductor shielded lead with brown rubber over shield. super special. $1.20 per 100 ft., $10.00 per 1000 ft. SCR -274 N COMMAND SETS, including 3 separate 6 tube superhet receivers, 2 separate 20 ASST. COIL FORMS-Including 11 Ceramic, 3 Polystyrene, transmitters, each with 40 watts output, modulator and DC power supply. Bargain price and 6 Fiberall useful sizes -46e. for all 6 pieces complete with tubes $39.95 VARIABLE CONDENSERS--350 MMFD, 5 Gang-$1.95; 4 2 Gang -61.49: 3 Gang-83e: Gang - -79e: 7.5 to 20 MMFD. 1730 V., extra long shaft Ilammariund -49e: miniature vari- INSTRUMENT BARGAINS OF A LIFETIME! ables -25 MSIFI) -39e: 50 51MFD-49c; 75 M511'D -595; 100 5,M7-D --69e; 190 MMFD -795. BC -22I FREQUENCY METERS with calibrating crystal and calibration charts. A pre- TRANSMITTING R. F. CHOKES -4 pie. 350 MA -25e or 5 cision frequency standard that is useful for innumerable applications for laboratory tech- for $1.00. nician. service man, amateur, and experimenter, at the give -away price of only.... $39.95 INTERRUPTION FREQUENCY COILS for super -regenerative RADAR OSCILLOSCOPES -Complete with 27 tubes including 5 -inch cathode ray tubes - receivers or the tremendously popular F5í adapters for standard $39.95 broadcast sets. Iron Core with 50 KC resonant frmuenry -39e; Air Core. with 100 KC resonant freq. -29e. 30 MC IF TRANS- FORMERS--Double slug tuned -25e. VIDEO AMPLIFIER PLATE Coils -Slug tuned -25e. 300 MILLIAMPERE METERS-G.E. or Westinghouse, 31/4 inch diameter. flush mounting. REMOTE CONTROL UNIT -Aluminum Caso rani!" con- Priced at $2.25 each. or 5 for $10.00 taining 2 potentiometers. triple pole switch. 4 knobs, gear mechanism, counter and phone jack -59e. AIR CRAFT MARKER BEACON -Complete with 3 tubes and sensitive relay to control 110 Volt Power Plant external . circuits from received signals. Just the receiver you have been waiting for to control models, open doors from a etc. 110V. 60 Cycle generator direct -connected to gasoline engine. distance, Priced at only 6 4.96 Worth a million for emergency or standby servire for hospitals. AIRPLANE INTERCOM AMPLIFIER- Complete with 4 tubes in aluminum case- theaters. hotels or for general service in hunting lodges. camps $ 4.95 or boats. A gift at $175.00. We can also supply the above unit for the same price with a direct coupled 32 volt D C. generator. In which ease we include absolutely free our $29.95 32 \all O C. to 110 felt A.C. converter which can also be used to sup- BC -654 TRANSMITTER-RECEIVER--Complete with 17 tubes and 200 Kc. calibrating 1,1v 110V. a. C. from batteries or farm lighting plants. crystal $39.95

BUFFALO RADIO SUPPLY, 219 -221 Genesee St., Dept. 4C, BUFFALO 3, N. Y.

RADIO -CRAFT for APRIL, 1947 51 /ÌJQw lQtJQy o . . WORLD -WIDE STATION LIST

it'1VARIETY -. Edited by ELMER R. FULLER Sensationally New TELEVISION AFEW changes have been made land on VLC10 on 21.680 megacycles, in schedules since the last is- VLB6 on 15.200 megacycles, and VLA4 RECEIVER KIT sue. Paris, France is now on 11.770 megacycles. These programs Ready for heard best from 2100 to 2245 are conducted by Ernest Suffolk, who easy, rapid as- hours EST on two frequencies, 9.660 welcomes reports, which will be ac- sembly. No megacycles and 11.840 megacycles. Pro- knowledged over the air on his pro- knowledge of grams are in English, and are beamed grams. television re- quired. Com- to North America. Moscow is being XGOY in Chungking is now being plete easy -to- heard on the east coast on 7.240 mega- heard from 1045 to 1145 hours on 6.140 follow instruc- cycles from 1300 to 1800 and from 1815 megacycles. News in English is given at t Lion sheet 2100. Saigon is gives you all to Radio reported on 1100 hours. Chungking is also heard on the knowledge 11.780 megacycles from 1800 to 2000 11.900 megacycles from 0500 to 0630 you need. hours, with very good reception. Colom- and from 1045 to 1145 hours. Reception is clear and sharp ... com- bo, Ceylon, is now being heard on a new The ten- and twenty -meter ham bands parable to a moving picture. All necessary components are included: frequency, 15.120 megacycles from 1330 have been very active but with the usual nothing is required except a screw driver, to 1530 on Sundays only. Other hours run of hams being heard. Nearly every cutting pliers and a soldering iron. Only may be in use soon, so watch for them. South American country is represented. the highest quality standard parts are Radio Martinique has moved from An American ham was heard recently used-the list price value of these parts alone is more than 9.170 megacycles to a new spot at 9.360 from Calcutta using the call VU2AY $300. 110 volts, 60 cy- megacycles. They are heard signing with 84 watts on 20 -meter phone. This cles A.0 $15950 off at 2100 hours. Switzerland is now is what we call dx, and is the best re- heard from 2030 to 2200 on 9.650, 9.630, ported here for some time. Let's have Federal Teleco Selenium Rectifier and 6.160 megacycles directed to North some reports on these ham bands, as Replaces Rectifier Tube $1.09 each America. A program of tips on dx listen- well as the commercials. Several G.I.'s 0 or more 99c each ing is being presented from Australia at are being heard from Europe and the 2010 on Saturdays from VLA9 on Pacific. Guaranteed Volume Controls 21.600 megacycles; at 0025 on Sundays Keep up the good work, and let us VLC4 Less Switch ...48c io for $4.45 from on 15.320 megacycles, VLG7 hear from you. Send all correspondence on 15.160 megacycles, VLAI4 on 11.770 to Elmer R. Fuller, Shortwave Editor, With Switch ...59c 10 for $5.45 megacycles, and VLB9 on 9.610 mega- c/o Radio -Craft, 25 West Broadway, 500,000, 100,000. 50,000, 25,000 ohms; 44 neg, 1 meg, 2 mega. cycles; and at 1715 Saturdays to Eng- New York City, 7.

RESISTOR CABINETS Freq. Station Location and Schedule Frei. Station Location and Schedule All wood construction. Sig .helves, 24 Compartments $3.89 11.700 HP5A PANAMA CITY, PANAMA; 0700 to 12.210 VIENNA. AUSTRIA; 1145 to 2090 2300 12.250 WXFD ADAK, ALASKA; 1800 to 0100 R.C.A. -T65 CABINET 11.700 GVW LONDON. ENGLAND; 2300 to 0030: 12.260 TFJ REYKJAVIK, ICELAND; Sundays. 0600 to 0715; 0830 to 1015; 1180 to 0900 to 0930 Packed In original carton. Beautiful Inlaid veneer 1600; 1800 to 2330 with grill cloth. Speaker ItSMO for 5' speaker. 12.440 HCJB QUITO, ECUADOR: 0600 to 1000; 1400 Runner feet. 11.700 SBP S TOCKHOLM. SWEDEN; 2000 to 2100 to 2330; Sundays. 0700 to 1630; 1700 11.710 VLG3 MELBOURNE. AUSTRALIA: 0230 to to 2200 0345; 0100 0145 $4.95 each. Three for $14.00 to 15.060 beam. 11.710 HE15 B ERNE. SWITZERLAND; -WNR1 NEW YORK CITY; European Tuesdays 0600 to 1800 and Friday,. 1000 to 1130; Satur- days, 1550 to 1625 13.050 KCBR SAN FRANCISCO. CALIFORNIA; Bargain! Guaranteed! 11.720 KIEV, U.S.S.R. Oriental beam, 2215 to 0100 100 11.720 PRIS RIO DE JANEIRO. BRAZIL; heard at 14.510 WNRX NEW YORK CITY; European beam, Assorted Bypass Condensers,600 V 0500 0600 to 1800 15.000 WWV WASHINGTON, aue 11.720 CKRX WINNIPEG. CANADA- 1000 to 2000 D. C. U.R. Bureau $11.00 11.720 OTC LEOPOLDVILLE. BELGIAN CONGO: of Standards; frequency. time, and 05311 to 0730 musical pitch; broadcass contanuoua- Special $6.95 11.740-000Y HAVANA. CUBA; 0630 to 0100 ly day and night 11.740 CEI174 SANTIAGO, CHILE; 1700 to 2400 15.110 QWQ LONDON. ENGLAND; 0000 to 0400; 11.740 NVl VATICAN CITY; 0015 to 0025; 0830 0600 to 1015; 1100 to 1315; 1500 to 20 x 20 150 WV. Electrol5t le 0900; 1600 eondonnen, Preen rock, guaran- to 1100 to 1145 SPECIAL! 11.750 MID LONDON. ENGLAND: 1215 to 1600: 15.110 HCJB QUITO. ECUADOR; 0500 to 1200; 1330 to 2230 Valuetee'. 68.75 10 for $4.95 loll to 1200 11.770 VLA4 MELBOURNE. AUSTRALIA; 1100 to 15.120 HVJ VATICAN CITY; 0830 to 0930; 1100 1200; 1530 to 1830: 2345 to 0045 to 1145 11.780 HP5G PANAMA CITY. PANAMA: 0745 to 15.140 GSF LONDON. ENGLAND: 2300 to 0400: WELLER SPEED IRON 1000; 1200 to 2230 0600 to 0815; 0830 to 1745 Saves Time and Morley 11.780 MOSCOW. U.S.S.R.: 0900 to 1000; 15.150 SST STOCKHOLM. SWEDEN: 0130 to 0215; 0600 to 0700: 1000 to 1315 Soldering heat In 5 , eende. 2000 to 2130; 2200 to 0100. 1730 1815 4 For Radio, Electronic, Telephone, d' 1 2 9 11.820 GSN LONDON. ENGLAND; 2300 to 0090; 15.160 /ZK TOKYO. JAPAN; to Telegraph, Test, Repair. Laboratory, etc. W 0100 to 0500: 1030 to 1430; 1700 to 15.170 IOWA GUATEMALA CITY, GUATEMALA: 5 1200 Complete with 2 extra tips. net 2090 to 2000 11.830 MOSCOW. U.S.S.R.: 2200 to 8600: 15.180 GSO LONDON. ENGLAND; 2300 to 1200; 0730 to 0845; 1100 to 1600 1230 to 1745 11.830 CXAIO MONTEVIDEO. URUGUAY; 0600 to 15.190 CKCX MONTREAL. CANADA; 0800 to 1200 2200 15.190 TAG ANKARA. TURKEY; 0000 to 0200: SUPERIOR 11.890 CONSTANTINE, ALGERIA; 0050 to 0415 to 0730 0300: 1200 to 1800 15.220 JTL3 TOKYO. JAPAN; 1800 to 0230 Model 670 11.840 VLC7 SHEPPARTON. AUSTRALIA: 0800 to 15.230 VLOf ME3LBOURNE. AUSTRALIA; 2100 to Mill Super -Meter 11.640 PARIS. FRANCE; 0000 to 0045; 0100 15.230 MOSCOW. U.S.S.R.; 2200 to 2400: to 0145; 0545 to 0615: 1045 to 1130: 0530 to 0830: 0915 to 0930; 1030 A Combination Volt- 1315 to 1730: 1830 to 2345 to 1730 11.880 MOSCOW. U.S.S.R.; 2200 to 0600; 15.260 GS1 LONDON, ENGLAND; 0400 to 0430; Ohm Milliammeter plus 0720 to 1900 1030 to 1400 DELHI, Capacity Reactance In- 11.880 LRR ROSARIO. ARGENTINA; 0600 to 1800 15.290 VUD3 INDIA; 2245 to 0030; 0130 11.880 MOSCOW. U.S.S.R.; 2200 to 0230 to 0145; 0200 to 0400; 0445 to 0815 ductance and Decibel 11.800 XGOY CHUNGKING. CHINA: 0500 to 0630: 15300 GWR LONDON. ENGLAND: 0600 to 0900; Measurements. 1041 to 1145 1045 to 1330; 1400 to 1430; 1700 to 11.900 0XA19 MONTEVIDEO. URUGUAY; 1830 to 1800 2115 15.310 GSP LONDON, ENGLAND; 2345 to Complete with test leads and 0030; $28.40 I I.ai0-IiVX LONDON, ENGLAND; 0515 to 0530; 0100 to 0500; 0600 to 0815: 1200 instructions 0600 to 0630; 0700 to 0730; 0745 to to 1315: 1615 to 1845 0900 15.310 VL04 SHEPPARTON, AUSTRALIA; 2045 to 2145; Write Dept. C -4, for our FLYER. 20% 11.960 HEK4 BERNE, SWITZERLAND; 1645 to 0010 to 0095: 1730 to 1800: Deposit with order required. Please 1715 except Saturdays 1900 to 1915: 2200 to 2225 add 13.910 sufficient postage. Excess will be refunded. 11.970 FZI BRAZZAVILLE. FRENCH EQUA- HERE BERNE. SWITZERLAND: Saturdays, TORIAL AFRICA; 0000 to 0230: 1000 to 1200 0445 to 0800; 0930 to 1030; 1100 15.320 MOSCOW, U.S.S.R.; 2200 to 2300- to 2020 0000 to 0500; 0530 to 0800: 0830 11.900 CS% LISBON. PORTUGAL: 0800 to 1000 to 1100 ?/gaiety ELECTRIC CO., Inc. 12.000 CENSO SANTIAGO. CHILE: 0600 to 0800; 15.340 MOSCOW. U.S.S.R.: 2200 to 0800; 1600 to 2300 1000 to 1100 601 Broad St., Newark 2, N. J. 12.060 MOSCOW. U.S.S.R.; 0800 to 1100 PARIS. FRANCE; 0700 to 0900 12.090 GRF LONDON, ENGLAND: 2300 to 1615; 15.350 LONDON. ENGLAND: 0100 to 0500; 1700 to 2030 15.450 GRD 9600 to 0700; 1700 to 1845 52 RADIO -CRAFT for APRIL, 1947 Frog. Station Location and Schedule

15.590 FZI BRAZZAVILLE FRENCH EQUA- TORIAL AFRICA; 11115 to 0800; 09311 to 1030 17.440 HV1 VATICAN CITY; 0715 to 0815 17.530 FZI BRAZZAVILLE. FRENCH EQUA- TORIAL AFRICA; 0000 to 0130; 0115 to 11745; 1100 to 1700 17.700 OVP LONDON, ENGLAND; 0600 to 1115; 12011 to 1600 CONCORDS 17.710 GRA LONDON. ENGLAND: 0600 to 0815 17.730 GVQ LONDON, ENGLAND: 0100 to 0500; mom to 1215 17.760 PARIS. FRANCE: 0700 to 0900; 1100 LATEST CATALOG OF to 12311 17.770 OTC LEOPOLDVILLE. BELGIAN CONGO; 0500 to 15311: 1130 to 1045 17.790 GSG LONDON. ENGLAND; 0100 to 1050 17.800 01X5 LAHTI, FINLAND; 0130 to 0200; 051111 to 0515; 0800 to 1700 17.810 GSV LONDON. ENGLAND; 0100 to 0400; 115110 III 1430 17.820 PARTS CKNC MONTREAL. CANADA; 0830 to 1500 RADIO 17.830 VUDIO DELHI. INDIA: 00110 to 0130; 0115 to 11700 17.840 BRUSSELS. BELGIUM: 0500 to 0630; 0011 to 0115; 1010 to 1245 AND ELECTRONIC EQUIPMENT 18.020 GRO LONDON. ENGLAND: 0100 to 0500; 00311 to 0845: 0900 to 1130 18.080 GVO LONDON, ENGLAND; 111311 to 1215; 13011 to 1500 18.130 PMC BATAVIA, NETHERLANDS INDIES: 23311 to 0930 21.470 G8H LONDON, ENGLAND: (1500 to 1215 21.530 GS1 LONDON, ENGLAND: 0500 to 0815 21.640 GRZ LONDON. ENGLAND: 0600 to 0900 21.550 GST LONDON, ENGLAND; 1030 to 1130 21.750 GVT LONDON. ENGLAND; 0100 to 0500; 1030 to 1130 26.100 GSK LONDON. ENGLAND: 0615 to 1000

A 300 -volt dry battery which weighs only 1 pound has just been announced by National Car- bon Co. Known as the Eveready Mini -Max No. 499, it is 2 11/16 inches long, 211/32 inches wide and 315/16 inches high.

WIRELESS PHONO OSCILLATOR Transmits recordings from phono pickup or role* from mike to radio Without use of wires up to 500 ft. Ne illy designed. SPECIAL VALUES Complete kit, lest tubes 53.49 Above kit assembled and tested 4.49 HAM GEAR Tubes for above kit 1129.17. 35Z5) 1.49 IMMEDIATE DELIVERY Jobbers. Write for Quantity Discounts on Amplifiers AMPLIFIERS A ant Oscillators. CONSTANT ELECTRIC, Dept. C 112 Cornell. Street Brooklyn 21. N. Y.

LATEST TELEVISION RECORD CHANGERS COMPONENTS PLAYERS 4e

Thousands of Newest Items! Immediate Shipment! Just off the press -48 exciting pages of radio parts, Largest stocks equipment, and supplies for dealers, servicemen, ama- AS USED IN THE NEW of all leading teurs, maintenance, testing, building and experimenting lines of -Thousands of items NOW IN STOCK and ready for RCA 1011 RECEIVERS nationally - IMMEDIATE SHIPMENT! Big feature sections of SII deflection yoke $14.75 known Radio Radio Sets, Communications Receivers, Amplifiers, Re- 1 acusing coil 7.95 Trap 5.10 Parts and placement Parts, Ham Gear, Record Players and Port- V. rtical output Transformer 8.50 Electronic ables, Record Changers and complete Sound Systems. Il,rizontal output Transformer with Equipment on Page after page of bargains i.n top-quality standard - :11100 V. and I V. windings for sec- ond anode supply 18.00 hand at all make radio parts and electronic equipment. rive band RF Switch and Coil assembly 5.60 times at lowest 1lthode Ray tubes for Television and Oscil- prices for the Mail Coupon NOW for FREE COPY loscopes from 1" to 16" amateur and Also Mail coupon below TODAY tor your FREE COPY of Receiving Tubes Capacitors (Ceramic. professional this latest Concord Buying Guide and Bargain Catalog --,lrkete oil filled, mica. etc.) radio man. and other television of Radio needs you can order for SAME DAY SHIP- Coaxial Cable components MENT from complete stocks in Chicago and Atlanta. Send 50e for complete catalog including dia- grams for RCA. GE. Dumont, Stromberg- Carlson, Andrea, and Viewtone Television Receivers. 47 OPI. ¡i. World's First Specialized DCOO.,rylcega 8, House in Television O k Blvd., new 90oaVII. Jackson Per f Yes, rush E COPlos TELECTRONICS SERVICE î Concord B ...... AND SUPPLY CORP. R A D I O C O R P O R A T I O N Name LAFAYETTE RADIO CORPORATION ¡tddress...... State 264 West 40 St. New York 18, N. Y. CHICAGO 7 ILL. ATLANTA 3, GA. -...... Phone PE -6 -8730 901 W. Jackson Blvd. 265 Peachtree SI. City

RADIO -CRAFT for APRIL, 1947 53 SURPLUS RADIDELE(TRODI( (IR(VIT$

SURPLUS TRACER FROM BLOOPER TIME -DELAY CIRCUIT While planning a new untuned signal The specially designed time -delay cir- tracer, I decided to see what could be cuit illustrated operates a control relay done with an old seldom -used regenera- a predetermined length of time after tive receiver (Fig. 1). The plug -in coil the control voltage has been applied. SURPLUS was removed and a tube base connect- Upon removal of the control voltage, ed as a jumper to connect the cathode an equal time interval will elapse before the relay is deactivated. RADIO With switch Si in position No. 1, the TRANSMITTER bias developed across the cathode re- BC 1306, complete with two tubes, sistor charges condenser C through the 2E22 and VR 105 uses two R. 3A4's that are missing control resistor This biasing voltage reduces the plate current of the tube to a point at which the relay contacts MINE DETECTOR s- Complete with 9 tut- new I to ground. A shielded probe was made and connected to the antenna post. The regeneration control became the gain With the tracer (Fig. 2) in NAVY INTERPHONE control. AMPLIFIER Type R -7, complete with tubes less dyna- motor (dynamotor 75e ex- open. When the switch is thrown to po- t ra) $ O sition No. 2, the cathode resistor is shorted to permit the charge to leak off the condenser through the variable re- sistor. The relay closes when the plate KEYER current has risen to the proper value. TG -10, with photoelectric cell, has com- action it is possible to follow a signal JOSEPH A. SIDERMAN, plete 20 watt amplifier, also 1/20 horse- from the antenna to the detector of a Eatontown, N. J. power, 60 cycle AC motor enclosed in receiver. black crackle case 15" x 21" s 101/2 ". 110 volt, 60 cycle using a When the coil is replaced the unit A.C. -D.C. PHONO MOTOR pair 6L6is in the output becomes a tuned tracer or signal gen- Portable a.c. -d.c. phonographs are (less tubes) erator. often equipped with a.c. motors which WESLEY NEELANDS, make them useless in d.c. districts. I Toronto, Canada heve converted a portable unit so that POWER TRANS (Continued on page 77) 25 AMPLIFIER 100 mill 2 -6.3 5V 700 ct -WATT 60 cy -I 10V $1 5 An output of 25 watts by the ampli- fier described is produced with mini- mum distortion. It can be constructed on a relatively small chassis. A push - RESISTORS pull input stage is used to eliminate (assorted) $7.50 phase inverters and coupling transform- 4P. D.T. SW. SHOWN Per thousand ers. 6SQ7's were used in the input stage. IN DC POSITION but 6SF5's may be used. Input from a No order accepted pickup or high -gain mike is through a MOTOR WINDING less than $5.00

Thousands of parts and tubes in stock. Tell us your needs. í500n URN SHIELDED I INPUT-

order or I 3 Send check, money I merely enclose currency (at your risk) 1

1 1500n

RADIO IOH/ISONA 2- conductor shielded cable. The conduc- tors are connected to the high sides of CENTER the ganged volume controls and the inverse AI .01 2530 EAST DAVISON shield is grounded. If desired, feedback may be used by connecting two Phone TUIsa 3 -0355 2- megohm resistors as shown by the dotted lines. DETROIT 12, MICHIGAN FRANK GUE, S Edmonton, Canada untAc 54 RADIO -CRAFT for APRIL 1947 CS St sfteceatil

THIS EQUIPMENT HAS BEEN REMOVED FROM SURPLUS AIRCRAFT -AND IS SOLD AS USED

w... O / , t? :

SCR-522 100.156 Me. PE -103 DYNAMOTOR UNIT TRANSCEIVER REC. RECEIVER AND TRANSMITTER - - e,w ,w. uw to oow+r .,w rola o. ea,. TRANS. BC -620-H O,s el Kw most lnlwnw,r w wlp 2240.1 of tu.oba. transnowlw. Dmrw to. ow wub w. BC-654 p1s lec phew w pw.b stew., plc Portable, low power, fre-wuency modulated twwwwwww Inpw-6V DC 21 amo.. o , bur oK Range of approxmutely S miles. 2 channels. 12 V. DC t 1 amp. O0pw-500 V DC 160 M, mtJ

5 -TUBE AIRCRAFT RECEIVER 200.400 KC operation. Complete with tubes for 24 V. operation. Price _....__...... $4.95

INTERVALOMETER Used to release bombs at pre- deter- mined intervals -adaptable for use as a timing device in photography. etc. BC-375-E GENERAL ELECTRIC Price MOPA TRANSMITTER . _..__ ___.....$2.75 ea. wd. p 200.500 K< w 1.500.12 500 ec we.eOrbe mewls p 7 pur« vu,. u.na I,.m.pN B J.I`a.i ,edlw.,w. oone,en n 10 w 20 met.n ut w. TRANSMITTING AN 07,c 0e.141> n wl..n.ua rw,p MISCELLANEOUS Orr: npnr.va

RADIO -CRAFT for APRIL, 1947 55 TflY rugs DISCARDED STARTERS One of these transformers should have Discarded fluorescent starters can be core -type laminations; the other a shell - used in radio and electronic apparatus type core. Remove the secondaries from either as voltage regulators or as a.f. the one with the shell -type core, then oscillators. carefully unwind the primary. Remove Remove the can and condenser and the secondaries from the transformer PROFITABLE connect the terminals across a source of with the core -type laminations and in 0 variable d.c. voltage. Measure the volt - their place rewind the primary from the ADDITION TO agI across the terminals as the voltage other transformer. In some case a wind- is varied. Reverse the connections and ing may be found which can be slipped ANY RADIO SERVICE repeat the tests to find which connection on the core leg "as is ". BUSINESS gives the best regulation. When the Apply 117 volts a.c. to one of the best connection has been determined, primaries and measure the voltage mark the terminal that is connected to across the other while working into a the B -plus lead. The tube will fire at light load. Reverse the windings and approximately 115 volts d.c. and ex- again read the voltage under load. If This big tinguish at 80 volts. It will carry a 10- the voltage is low on the output wind- book shows ma current with a change of 5 volts ing, add a few turns to it to bring the you how -every from 0.1 ma to 10 ma, and is applicable voltage up to 117. A 200 -ohm, 200 -watt step of the way - to conventional voltage -regulator cir- potentiometer inserted at the point X, cuits. A starter may also be connected and a 150 -volt a.c. meter across the out- only put winding will decrease the output f voltage to any required level. 2 .05 The unit may be improved by re- winding one of the low- voltage sec- ondaries over either of the windings IT PAYS TO SPECIALIZE SUPPLY VOLTAGE OUTPUT to supply voltage for a pilot lamp. IN .005 HYMAN HERMAN, SOMETHING DIFFERENT Flushing, N. Y. There's good money in electric motor repair! GAO- The field is not crowded-and what could be a finer more profitable addition to your already SOLDERING KINK established radio service business? Every home you visit on radio work has many motor- driven as an a.f. oscillator whose frequency Strongly soldered joints, especially appliances. Be the man who can repair them! may be controlled by plate voltage or where several components are tied to- ELECTRIC MOTOR REPAIR, the unique new book by the publishers of the famous Ghirardi the value of Rl plus R2. The output gether, can be made by using a spiral Radio-Electronic books, teaches you the work from voltage is determined by the ratio of connector. A spiral connector is made the very Explains every detail of motor trouble diagnosing, repair and R1 to R2. The table gives the values of by winding bare copper wire in a tight rewinding. Covers a-c and d-c R1 plus R2 to give a 400 -cycle note for motors, synchronous motors and generators and mechanical and different supply voltages. electrical control systems. Supply Volts (d.c.) Rl plus R2 (ohms) 110 90,000 A "BENCH" BOOK 140 200,000 Based on what you can learn 180 500,000 from this big book alone, you can train for prompt, profitable 250 1,000,000 motor service. Quick reference The tubes from starters are also use- guides for use right at the bench show exactly how to ful in power supplies with poor regula- handle specific jobs. Invaluable tion. Connect one of the units in series for beginners or for daily refer- ence in busy shops. Unique Duo- with a resistor connected as a bleeder Spiral Binding divides book in- across the 250 -volt tap. This reduces to 2 sections permitting text and the more than 900 diagrams the high starting voltage that often and illustrations to be seen AT plays havoc with filter condensers. THE SAME TIME. When the load is applied to the supply, "BORROW" IT FOR the tube extinguishes, removing the 5 FULL DAYS! bleeder load. springlike spiral about 3!s inch long. Send coupon now Practice The diameter will depend on the number from ELECTRIC W. Z. BUCIELSKI, MOTOR REPAIR Grand Haven, Mich. of wires to be joined. Leads from the for 5 days. If not components may be inserted into either more than satisfied, le. ends and solder flowed return book and /s ti ISOLATION TRANSFORMER or both into the every cent will be spiral. This makes a good electrical con- cheerfully refunded. When servicing and operating a.c: d.c. radio and electronic equipment there nection that is mechanically strong. is constant danger of shock or injury MARCEL STRUDLER, unless line polarity is strictly observed. Tel -Aviv, Palestine. This danger may be avoided by using an isolating transformer. One may be FADED TUBE NUMBERS built from two power transformers with Many schemes have been suggested Dept. RC -47. Murray Hill Books. Inc. reading on 232 Madison Ave., New York 16, N. Y. burned -out or shorted secondaries. for type numbers glass Eneln.ed Is s5 4 5.50 foreign) for a copy or Select two transformers, preferably tubes after they have faded. I find that ELECTRIC MOTOR REPAIR Book; or D send C O for 55 plus postage (no foreign C.O.D.'sl. t ' with capacities of 100 watts or greater. placing the tubes in an icebox for a either eve nt. If no satisfied. It Is understood t may return book In 5 days for complete rem, short time will cause moisture to form of my money. on the tube, and the numbers will AC VOLTMETER stand Nane 117104AC out clearly. Be sure to mark the number , permanently on the base. A scratch awl Adates. I50V.AC or china marking pencil can be used. I LAMINATED CORE City & Dist. Na. BILL KEENE, JR., 2.51.FOR PLOT LAMP Wichita, Kansas 56 RADIO -CRAFT for APRIL 1947 NEW CRYSTRON LAPEL RADIO (Continued from page 49) Alettap alitaii. old speaker never had a fair chance, demanding as it did a high polarizing voltage at a time when there was nothing better than B- batteries to supply it. It NO LOWER PRICES ANYWHERE! consists of a thin metal sheet suspended close to in front of a metal plate, and THE NEW MODEL III We carry nearly 5,000 instruments with a high polarizing voltage between in stock. AC -DC Quality MULTITESTER All models listed below are available for them. The voltage on the thin sheet is immediate A New Pocket -Size Volt- OhmMilliammeter with delivery. varied by the signal, causing it to be features never before available In an instrument attracted and repelled by the heavy of this size and price. PRECISION APPARATUS back plate. This vibration back and forth D.C. Voltmeter: 0 -5 -50- INSTRUMENTS reproduces the speech or music. I used 210- 500 -2,500 volts. A.C. 8320 -31 Range Al. -IR' Multi Range Tester 823.04 Voltmeter: 0 -10. 100 -500- 844P -34 Itange AC -DC 808 trolls AC and DC VOLT- an electret for the back plate, and thus 1,000 volta. Output Volt- OHM MILLIA5ISIETEIt 32.20 meter: 0- 10.100- 500 -1.000 8561' -14 Range Super -Sensitive. 000 volta AC -DC kept a voltage higher than 600 between volts. D.C. Milliamme- TESTER 20.000 aluns per volt DC 49.94 864 -AC 011S1- DECIBEL- it and the sheet of aluminum foil which ter: 0 -t -10 -100 milliam- -DC VOLT- MILL1AMMETEIt peres. D.C. Amperes: 0 -1- with large 9' meter 59.60 10 amperes. Ohmmeter: 9121' -Dynamic Mutual Conductance Tube Tester . 61.20 formed the diaphragm of my improved E- 200 0- 5eo - 100,000 ohms: 0.1 -A.M. -F.SI. and Television Signal Generator 64.15 speaker. Instead of the perishable rub- niegohin. Decibel Meter: EV -10P-6000 volta AC und 1K' Vacuum Tube Multi - -8 to +55 db. The scale Range -Meter 71.81 ber which was used in the old speakers is calibrated for line of 9219'- Combination Dynamic Mutual Conductance Tube as an insulating cushion between dia- 500 ohms impedance. For Tester, Battery Teeter and 33 Range AC -DC Multi- other impedances corree- Range Met Tester 84.20 phragm and back plate, a war -developed tinn charts are supplied. 954P- Combination Mutual Conductance Tubo Tester, Model IIIP. In portable Battery Tester and 37 Range Super- Seneltive AC- plastic was used. case (not illustrated) In- DC Multi- itango Set Tester. 20,000 ohms per volt cluding testing leads and rompleto Instructions 819.85 UC 99.20 As soon as I finished the construction Model 111A, open face as shown. of the complete with Crystron Lapel Radio I took it instructions $6a WESTON ELECTRICAL over to the Editor of RAt:go -O n' and INSTRUMENTS proceeded to demonstrate it to him. It The New Model 8-45 697 -Volt -Ohm Milllammetcr 826.45 779 -Super Sensitive Analyzer 78.45 (Contim(ctl on pays (31) Battery Operated 785- Industrial Circuit Tester 103.66 SIGNAL GENERATOR 796 Mutual Cond. Tubo Checker and Analyzer 187.10 B for servicing AM. FM and Television Receivers SUPREME INSTRUMENTS Instructions So Complete ..51(:- 5l ulti -Tester $18.95 589 -Tube and It.,l ter> 3',' -ter 48.95 599 -Tube and Set 'l.. ICI- 62.50 515- iacuum Tube V,:lt Meter 63.50 Anyone Can Build Our 578 -Signal Generator 68.95 804 -Combination Tube and Set Tester 89.50 516- OSrlltincnpe 89.75 NEW MODEL S -5C RADIO McMURDO SILVER CO. 9.5 U;^...Mir . ! 'fia a39.90 9 I-t'p.,i1,a Ii.l,u,r,:wL'r dn 49.90 rV'a o,un Tub,. A 59.85 atYl 89.90 RADIO CITY PRODUCTS Multi Tester 517.95 * Ú -- MUAI- Tester 24.50 ltynoptImum 41.51 It-F. frentrneles from I:A I iLryclrs tt 7,0 Alera Tube Tester 'yclea 1150 Kc. to l2.5 51e. on F'undalnentals 1:.d i -l'- Sensitive Multi- Tester 42.63 I- Electronic 45.110 tran 11 Mc. 10 50 Mc. on Dannouic,l. Cons Multi- Tester Signal Generator 49.50 Idete will shielded test lead. self- .,_Itollehart contained. batteries and Instructions. S27.75 Tube Tester 59.50 Net L I -N- Combination Tube & Set Tester 59.55 V.T.V.O. It Steter 73.01 Combination Tube & Set Teeter 89.50 Our model 5 -5C uses the universally accepted ",.\ -V.'r. "Billionaire- Itisulat ion Tester plus VTVM 92.61 super -heterodyne circuit containing the follow- The Model 689 -IF ing tubes: 125.47. 125K7, 12597, SOLE, 3525 and WESTON OHMMETER SUPERIOR INSTRUMENTS tunes from 550 Kc. to 1600 Kc. Model S -SC t'.\ -11 -CI gnat Tracer 818.75 6: ii-Super Meter 28.40 (Illustrated) . . . complete kit less tubes. A convenient, pocket Biro ohmmeter for chasing dr- CA- 12- Audible -Visual Signal Tracer 34.85 Bakelite cabinet and brand now illustrated cultr by the resistance and 450-Tube Tester 39.50 650-shoal Generator 48.75 instruction sheet, showing simple detailer. mnlnuity method. The ener- gy fOr the resistance read- 4.-- F :lertrnnie Multi- Tester 52.50 6, e - Combination Set step -by -step diagrams. ings Is supplied by a self. Tube & Tester 62.50 contained 1.5 volt No. 2 standard OUR INSTRUCTION SHEET COVERS large flashlight cell. Built to meet D.B. SHALLCROSS MFG. COMPANY EVERYTHING Army Requirements for Ac- Brade Bes ietuiee sbires 513.50 curacy and Durabilityl Portable Galvanonteters 27.50 Pictorial Diagram 630-Wheatstone Brldgo 75.00 This Ohmmeter also has a 637- Kelvin Wheattone Brider 100.00 Schematic Diagram double range 0 -10 and 0 -1000 638- 2 -Keldn \Vh,.t. teco ltt t.t,t. 150.00 Photographs ALLEN B. DUMONT Step -by -step wiring instructions LABORATORI ES aluns for the accurate measure- switch Wave Available at your local distributor ment M low resistnner values. ]65A- F.Irrt rivi),' and Square Generator. 106.00 or write to us for catalog M Model 689 -IF rotors connote! 279 -5' Oscilloscope 6115.50 tc lth operating instruction. test SVATF.1tMAN 'Pocket" Oscilloscope 55.00 I-ads und LEATHER CARRY- MONITOR Crystalline,. Signal Generator 57.50 Other Models ArnildLle ING CASE. 131.1LEY Crystal Controlled Signal Generator 69.50 List price 525.50 201, -fiert come Measurements Mutual Conductance Our Price 514.85 Tobe Trier 49.85 RADIO KITS COMPANY 120 Cedar Street New York 6, N. Y. ORDERS FILLED SAME DAY RECEIVED! NNNsNNNNNsNNN TERMS: 25`ìó Deposit, Balance C.O.D. Or Full Payment with Order. I'd like to dots,' çou SEND FOR FREE CATALOG 110 aV I've sold nay unpatented INVENTIONS GEORGE PEARCE ELECTRONIC & 47J Bartholomew St., PEABOI)Y, MASS. QfZ4eetaft INSTRUMENT CO. 1f five thousand people in America will benefit from your invention, you can sell it within Dept. C, 6 MURRAY STREET, Cable Address: METRONICS sixty days. NEW YORK 7, N. Y., U. S. A Phone: BArclay 7 -5556

RADIO -CRAFT for APRIL, 1947 57 LAMP BULB RESISTORS :New- Guaranteed "TAB" Electron it Parts (Continued from page 23) That's A Buy at the measured voltage. By the simple RCA 828 JAN -CRC New Gt'd 81. now BC -746 -B DUAL CRYSTAL TUNING UNIT 7.5V /4amp. plate 1500V/200 watts application of Ohm's law you can Rated 140wetts output each "UHF" determine the power output of the de- (List $7.75) "TAB" prise .$2.75@, Contains Two for $5. with sockets. capa $5.40 vice. For example, let's consider that Two plug 807 JAN Old new, 2 for 32.00 829I1/3E29 Boxed GUI new 2.90 a voltage of 100 volts a.c. r.m.s. was in 2 CRYSTALS 304T1. Cid new. for 7.81 measured across a 100 -watt lamp bulb. F1243/81 955 JAN Old. 2 for 1.44 Cut & 1625 (8'807) New, 2 for 1.30 This corresponds to 760 milliamperes coils. 3ßP1 new Otd & SOCKET , 2.99 Variable 51111 or 50'l new (ltd 3.96 and a resistance of 132 ohms. Ohm's cona 2C26 Boxed new 10 Watts law, when applied to alternating cur- 140mmf. L'Unie, 2 for 1.50 I ,3 Mal socket 954 Boxed new (Rd @ 50e. 5 for 2.00 rents and voltages in a purely resistive complete OAKS new Old @ $1, 10 for 8 90 71A., 1.25 0,.105 Boxed new JAN @ Ble. 10 for 7.49 load, is the same as for d.c. Therefore, 2050, 2X2 11K60 /1641, 6SL7. 1E7(4 @ 1.25 3'L8, 01.6. 3525. 128Q7, 121,117. 2 for 1.80 the power output would be: power = Wit 11 earla.Inulum linisldng lane, Two IVE 717A DOOR KNOB tube new, 2 for 3.85 volts times amperes or 100 x 0.760 B(74 -B units $2.25 WE 703A UL'HF DOOR KNOB tube new 5.95 = CRYSTALS AMATEUR FREQ'S FT243 /BT EDISON TIME DELAY RELAY I15V /10A,op 1.49 76 watts. Four for 3.00 446A/2C40 Lighthouse tube (LP $13.50) 2.85 CRYSTAL STD 200KC-!- lOcye- Vacuum 5.95 956, 957. 938A. 959 & socket. each .90 If resistances or dissipation ratings 872A JAN (Rd new & socket, 2 for 5.75 GE TRANSF 1I5V /00cy PO HV lnel as follows 666A JAN Otd new & socket. 2 for 2.00 desired cannot be found in the tables, 4000V/2ms Shielded Nary C'Ray cared $3.95 31124 1IV RECTIFIER 20000V /60ma 3.00 arrangements in series, parallel, or Auto trans( 115/160/170/180V/1.95Amp eased 2.95 PULSE TRANS 0.4211J SEC IIORIZ BTO Traust GE Cased 90 /80 /70V /1Amp 2.95 TELL V $1.49 series- parallel can be worked out to give )1 almost any value. 6.8V- 4V /10A, 6.5V /6A, 5V /3A. 5V /3A $3.95 2V30 JAN ITV RECr 16500V ($3.40), 2 foe.1.50 750VCT /22Om Cased 3.25 6AL5 Boxed new Otd 3 for 2.25 Currents in circuits can also be meas- 7.5 & 10V /8A -Pri 105 to 120V easel 4.95 6150 dÁ4. 6C4, JAN Gtd new, 68c @ 2 for 1.25 ured with incandescent lamps when a I0V /,.25A, 2.5V /10A 6.3V /2A. 5V /3A & SA7, Iß80, 6SN7. 6.78, 6%'6, 9006 New .64 700VCT Gael llullie,ofters 11V In 6.95 /,07. 65(17. VR105,VIt150, 90e, 2 for 1.60 suitable milliammeter or ammeter is CONDSR oil 3mfd /330VA(' /1000WVDC. 2 for 2.50 Y3OT RECTIFIER new Ctd. 59c @ 2 for 1.00 NAVY Si'3' SYNCIIROSCOPE NEW 59.50 not available. The lamps are connected 614 JAN GTD. 2 for $2.96 in series with the load and the same OSCILLOSCOPE r KIT 3BP1 Includes 805 or 845 JAN & sockets, 2 for 8.98 Trend 115V 60ey Prl, 375VCT /I loua, 5BP4 JAN & SOCKET, 2 for 6.49 procedure as outlined for determining 1320V /8ma. 5V/3Á. 2.5V/3.25A. 6.3V/ VRI27A /100th new & Conetrs, 2 tor 5.98 2.75A. 3BPI, 5Y30. 2V3G Tubes GE Vacuum delay switch 15000V /10 Amp 3.95 power is used. The voltage drop across CONDSRS, CHOKE, RESIST, LOW& SYLVANIA INS{ GERMANIUM CRYS- HV SUPPLY NEW GTD- THORDAR- TALS 1.39 the lamps is measured and the value of SON NAVY PARTS SPECIAL $16.95 current can be determined from the PRI TRANSF 230V Inpt. 117/112/103/ StrohoSash Condenser, 24mfd /660VAC/2000w 93V/7A $19.95 VDC (4 section) ($301 Special 57.95 tables. For instance, with a voltage of GE CONDSR PYR 28mfd /660VA0 /2000 CT(' 6L6 PP. 3800ohreCT 18toi5Watt, SEC VDC /4 9.90 25 across a 200 -watt lamp, the current 2.5. 6.5, 15.5, 62, 250 ohms H1 -F1 $3..95 WElnpt & PP Driver tranefs 6C6/805 6.95 from the tables would be 765 milli- UTC LINE AUTOFORMER LVM- 11 /30watt FOXBORO Mechanical Recorder with I10V /60 up to 10/500, 250. 167. 125, 100, 83. 71. cy motor -mech & Elect Recording 152001 69.95 ampere. (Continued on faring page) 62, 50ohmL 3.95 WE Ounoer min PP /P to PP /O HIFI 1521) 1.49 TRANS? LINE TO LINE 500/333/250/200 / H1 -1311' SC Headsets with 8' cord & plug 3.25 1.25 50ohma ±1DB Cased Thermador mfger 1.95 A.C. KEY with 6' Rubber cord & P1.155 plug .75 STANCOR 2100V /loma C'Ray cased 11V ins 5.95 CHOKE GE 0.5Hy /lAmp, FOUR for 1.98 IF'S 7%mc's. STAGGER TUN ). 3me'a band width VIDEO TELEV IF'S 7 UNITS 6.95 COLLAPSIBLE ANT: AN -30 Talasen,.. ta F3 RCVR RELAY RACK MTD 81/2'i GR VARIAC 200CÚ /860WATT $14.96 I9', FIXED TUNED XTAL SUPER TRANSTAT 110V Inpt, VAR. 88 t HET uses 6K7RF&IF, 6K8 MIXER, 132V/I8.2 AMPS 29.50 8C8DET&BFO. 6F7DETAVC. 6C8au- BAT dio&NoiseL 80RECT, 115V/80ey par V 4V/40AH OUTPUT 58V 30.L3V/375 supply. ase, !olla, tutea, manual, no ma, 1.5V /200ma, 7.5V /20ma, NAVY 'tal- NEW -use as tumvtr. VFO $13.45 MANUAL new Complete TRY 9.95 F3 Complete with extra eat of tubes 18.45 TBY VIBRATOR & CK1005 TUBE 2.50 TRANS? & CHOKES CASED 500V^P /00 TRANS? OUTPT 6V6's-PP/LINE /lOWatts $1.49 ma. 6.3V /4A & CHOKE 141I)s & Two 8mfd/ TRANS? LINE TO VOICE COIL CASED 1.2 450V Elect $4.95 HAYDON SYNC MOTOR 12V/604/24 UTC PI' /P to PP /G 1:1 Radio eased 1.95 RPM /4W, 2 for 1.49 UTC Lemke 250ma /2Hy & 2I1y cased 1.95 Constant IMP ROTARY BEAM COUPLER 3.95 UTC CHOKE 1814 /50ma need 1.00 W.E. DYNAMIC MIKE 20' ('ABLE & STD 9.95 TRANS? 14 or 20V/8A -210 to 240V /50 -60cy 4.95 I.4. -3 PSI 8'SPER CASE & Transi 4.95 TRANS CASED PRI 105 to 250V /50 -e0cyn ANTENNA SECTIONS SC. MS -50 -3954' long. Sep 2240VCP/500ma. 12V/14.5A. 19.2V/ 12 for 1.00 2.5A, 2.5V /10A. 30V /50ma. wgt 50 Iba 11.50 WESTON 796 OAK CAKE SX' so, 2 comp's 4.50 KNOB KIT ASSTD BAK' &RUSA. 25 for 1.25 ROTARY SWITCH KIT. SIX TYPES for 1.75 W.E. KS5825 SELENIUM RECTIFIER TRUNKS 22:16x12' SUPPLY. Variable Inpt IIS/230V50/ NAVY SEA LN. 3.00 Ripple CONTROL KIT ARJ SOto^megahm pote. 10 for 2.50 0Oeya. Outpt 0.4Amp. I15VDC, ASSMNT 300 BUSS & LITTEL 0,S%RMS- outpta up to 1.5Amp DC. FUSES 4A, 250 &200ma 3.95 POWER SUPPLY RELAY RACK EXT CORD LEVY DUTY BI 18' & MALI & MTG. TELETYPE Sy. $25.00 EM plugs $1.00

Precision Wire Wound Resistors V OHMS IRC, SHALLCROSS es 1000 MEPCO, INST. RES. CO., 0-10 10000 OHMITE FOR METERS BRIDGES, AMPLIFIERS 0-30 100 M 0-100 I Meg. ',:°.:. 5% TI0% (REST 1 %) 10 Meg. 5Ó0 2000 4000 4300" 0-300 co. 5000 100 7500 7950* 10000 15000 17000 300007 50000 75000 100000 130000 Electronic Volt- Ohmmeter brand new U.S. Army 140000 147000 166750 201000 Type 1 -107.F Precision Unit. 'Tab" special $19.98. 229000 250000T 950000f Mlo_C EOUI E CONDSR oil 3mfd /2000WVDC, 2 for $5.00 CONDSR oil 2mfd /5000WVDC. 2 for 14.50 "TAB" SPECIAL 3 for $1.00 «tt O & P CAPS NATIONAL&ALDI:N%,%- 25000 294000 314000 333500 9/16'. 70 for 1.96 CO. \ 353500 400000 402000 422000 SOCKET KIT 25 ASSTD Ceramic. mica, B, 2.35 RADIONIC EQUIPMENT Y. \ 458000 478000 THREE for $1.50 CONDENSER KIT SILVER & MICA 170 Nassau St., Dept. 104. New York 7. N. \ 500000 600000 700000 3 for $1.95 ('ONDSRS, 50 for 2.00 1947 RI74ISTOR KIT BT%&IWatt SOto2megohm Please send me a FREE COPY of your 1 MEGOHM 1% uey THREE for \ for loo 2.50 \ Catalog. f understand It has thnueands of Items \ I0Mee Ten KV MEGOMAX MFAI 1.75 W.N. RESISTOR KIT VIT TYPE. 20 for 1.00 s. Illustrated, described and priced and will be a 12Me9 12KV MEGOMAX MFAI -to- 1.95 Min. order great help to me In my search for "hard W W % ofl % H'metell Sealed Navy Resistors $2 FOR N.Y.C. Add Poahge all orders \ nod" radio equipment. (324) one megohm 1.69 and 25%/0 depoelt Worth 2 -7230. Send for catalog 99. Specialists In International Export. School. Col- WRITE FOR OTHER FROM STOCK lege and Industrial trade. Mmeybeek "TAB" Guar- Name SIZES antee. \ N. Address TAB" Dept. RC4, 6 Church St., New York 6, N. Y., U.S.A. "TAB" \ CORNER CHURCH AND LIBERTY STS., ROOM HO \\ CRY\\ State 58 RADIO -CRAFT for APRIL, 1947 This technique can also be used to determine voltages in the absence of an a.c. voltmeter. Of course, it is neces- sary to calibrate the source of supply GET YOUR voltage for the standard lamp before beginning testing. In this case, the bril- Commercial liance of the lamps is matched and the voltage read from the calibrated supply used for the standard lamp. FCC Radio Operators'

'2525 25L6 65K7 SOW. LAM

TcO LINE

Fig. 3 -Lamp used as a high -wattage resistor. IT'S EASY IF YOU FOLLOW OUR PLAN Possibly one of the oldest uses for Thousands of new jobs are opening up -FM, TELE- incandescent lamps is as an inexpensive VISION, MOBILE COMMUNICATION SYSTEMS, of are only a few of the radio fields which require means obtaining voltage drops. For licensed operators. example, we have a piece of apparatus which uses three tubes and desire to TIME IS IMPORTANT TO YOU! operate it from the regular power source You can get your License quickly with NILSON'S MASTER COURSE in RADIO COMMUNICATION and exclusive CIRE with a series resistor or ballast lamp. Workbooks of Instructional Aids. Saves you many hours of ran- The tubes naturally should be selected dom, undirected study. Assures a [MINIMUM of time in getting your have same 300 ticket. to the current rating, FREE BOOKLET tells you the Government Requirements for all classes of milliamperes, 150 milliamperes, etc. For commercial licenses-Sent Immediately upon receipt et coupon. the sake of illustration, suppose a 25L6, Approved for Veteran Training Under G -I Bill of Rights, 25Z5, and a 6SK7 tube were to be oper- CLEVELAND INSTITUTE OF RADIO ELECTRONICS ated from a 115 -volt a.c. supply. These RC -4 TERMINAL TOWER CLEVELAND 13. OHIO tubes all draw 300 ma of filament cur- MAIL THIS COUPON rent and have a combined voltage drop CLEVELAND INSTITUTE OF RADIO ELECTRONICS, of 56. Therefore, a drop of 59 or 60 RC -4 Terminal Tower. Cleveland 13. Ohio Gentlemen: Please send information about your Home Study Course for preparation for volts at 300 ma must be obtained in a FCC Commercial License Examinations. (This book does not cover Examinations for dropping resistor. By referring to Amateur License.) drawn from given in curves the data NAME the tables, it is found that a 50 -watt lamp would give a resistance of 204 ADDRESS ohms and a current of 295 ma for a voltage drop of 60. (Fig. 3.) CITY Zone STATF For accurate measurement of power If a Veteran Check here.

Olson Gives You a Big, Authoritative Book on How to Operate a Radio Shop Successfully 200 pages of practical advice and informa- operation with the Radio Manufacturers tion, to help you make a go of your Radio Association. If you are in business for your- and Appliance Shop. This book was recently self, or planning to open a shop or store, prepared by recognized authorities in co- YOU NEED THIS VALUABLE BOOK.

HOW TO GET IT: We will send you a FREE COPY CONTENTS: Business For Yourself - Selecting a Location - Build- of this book with each order for $10 or ing, Equipment, Layout- Financing, Legal Organization, Regulation more, during the next 30 days. Your - Buying - Sources of Supply - Receiving and Stocking - Retail order must be written on one of our Salesmanship - Advertising and Sales Promotion - Window and official order blanks, which is sent Interior Display - Repair Services - Major Appliance Sales - with our FREE Confidential 48 -Page Traffic Appliance Sales - The Farm Market - Personnel - Record Radio Repairman's Price Guide. Just Keeping Credit Management Expense - and Control - Develop- mail the coupon! ment and Growth. OLSON RAp10 WAREHOUSE 73 E. MILL ST., DEPT. 75, AKRON, OHIO

Please send me Official Order Blank and Confidential Radio Repairman's Price Guide. No charge, of course. PASTE ON A PENNY POSTCARD AND MAIL TODAY NAME ADDRESS

CITY STATE

RADIO -CRAFT for APRIL, 1947 59 SENSATIONAL SALE OF NEWARK'S LAMP BULB RESISTORS SURPLUS RECEIVERS and TRANSMITTERS (Continued from. page 59) 6 -Band, 8 -Tube SUPERHET FREQUENCY output, current, and voltage, a series of BC -348 METER $1050 power -measurement devices are avail- RECEIVER BC -221 39 able on the market. Examples of these A really beautiful pred are the power -measurement lamps made lion outfit that every by Sylvania Electric (RADIO- CRAFT, $4950 amateur should own. This March, 1944). These lamps are desig- Frequency Meter can be PMT, Here's the perfect rig for Hams ... for aircraft, used as Signal Generator nated PM3, PM4, PM5, PM6, marine, mobile use, etc. Has 6 Bands covering 200 and VFO. Helps you meet PM8, and PM9. They have two filaments kc to 18.0 mc (excluding BC). Highly sensitive re- FCC Regulations.. in one bulb and operate on the prin- ceiver with extremely low noise level. Meter has Crystal Calibration in all ranges, 125 ciple (brilliance comparison) described original Calibration F Include: Crystal Band -Pass Filter, Volt - kc to 20,000 kc. Includes in this article. Their resistance ranges ge Regulated Osc., 2 Stages RF Mixed, 3 IF's, Charts and Crystal, which alone is worth almost on 110 VAC, from 36 ohms to 310 ohms. Their power Bands, B Tubes, Built -in 28 volt Dynamotor our price for the entire unit. Works Electrically Vibrapock, or Batteries. Electrically Perfect and 0.005 to 25 watts at fre- r easily converted to 110 volt operation. ranges from (Perfect and Guaranteed -removed from unused o Guaranteed- removed from unused aircraft. Com- quencies from 15 to several hundred ,craft. An Amazing Buyl Approx. 50 lbs. plete with Tubes, ready to operate. Don't miss it1 megacycles. Their voltage drops range from 0.5 to 55. flceat 74.14caeeeoe' `r'alue! Table No. I SCR -274 N COMMAND SET RESISTANCE IN OHMS What a Buyl All this valuable gear for practically a song! Use thew units Voltage e.c., r.m.s. as stand -by rigs or salvage the precision components. Either way you Lamp get phenomenal value. Sire (Watts) 25 50 75 100 120 Ice; 3 -6 me; 6-9.1 mc, YOU GET ... 3 Receivers covering 190 -550 6 1315 1670 1970 I220 2400 3 mc and 4 -5.3 mc, 4 -24 2 Transmitters with Crystals covering -4 10 758 1020 1210 1350 1440 volt Dynamotors (easily c rted to 110 volt operation), Coupling Box, 29 15 500 675 790 890 960 Modulator, 2 Tuning Control Boxes, Antenna 25 302 394 475 530 576 Tubes included. A small mountain of equipment.. 40 160 217 275 327 360 from Electrically Perfect and Guaranteed - removed 50 132 177 220 263 288 unused aircraft. Parts alone worth many times the auras. 60 108 149 185 217 240 in Mg price. limited Quantity, Get your order NOW 75 91 124 151 174 192 100 71 97 IIS 132 144 ISO 44 62 77 88 96 75 WATT PHONE RIG All- Purpose 2 -METER RIG 200 33 47 57 65 72 BC -375 E SCR -522 Table No. 2 RECEIVER sir AAF CURRENT IN MILLIAMPERES Voltage a.c., r.m,,. TRANSMITTER Lamp 1114 IIIP XM ITTER She x3850 (Watts) 25 120

A complete transmitting outfit for CW or phone op- 30 38 1 45 SO eration. Cost over $2,000 to make. You pay less 10 33 49 62 74 83 meant get this than 50f a watt ... while stocks last! Byáll 15 50 74 95 112 125 swell VHF Transceiver ... 158 188 208 7 Tuning Units, 200 -12000 kc; 24 25 83 127 You Get ... one of the finest and 40 157 230 272 305 335 volt Dynamotor (easily a tied to 110 volt most economical 2 -Meter 415 with Relay, filter, and fuses/ An. 50 190 282 340 380 operation) rigs you can bey today. 60 232 335 405 460 500 Tuning Unit BC -306A; the original cost. tonne Now available for o small fraction of 75 277 402 495 575 625 Set of Tubes. Electri- Complete Consists of 10 -Tube Superhet Receiver with 100 350 517 650 760 835 rally Perfect and Guaranteed - x3250 squelch 7 -Tube %Mister, Remote Control ISO 565 807 980 1130 1250 removed from unused aircraft. Wgt. circuit, 28 Dynamotor (easily converted to 110 200 765 1070 1320 1525 1670 lbs. A wonderful buy Box, volt about 400 volt operation). Complete outfit with 17 Tubes, 8 for any Heal Crystals. Perfect and Guaranteed -removed from un See Newark's famous used aircraft. About 100 lbs. All for one Bargain Price BARGAIN COUNTERS! NEW YORK CHICAGO Offices 8 Warehouse 323 W. Madison St. BIG PROFITS 242 W.55,k St., N.Y.191 Chicago 6, III. On These Fast -Moving New York City Stores: 115 -17 W 45th St. & 212 Fulton St. Electrical Appliances 4 Travel -Maid Traveling Electric Iron. . 4.15 TELEGRAPH KEYS Improved Steam Electric Iron 8.48 ,/ursyin9 fvety Mercury Automatic Electric Iron 3.29

No. 1 106 Dominion Push -up Toaster 5.98 flecttoaie Need Faraday Electric Broilmaster 2.39 FOR THE- O RADIO SERVICE MAN General Mfg. Automatic Elec. Iron 4.97 D AMATEUR 2.37 STUDENT Streamlined Electric Iron EXPERIMENTER I- Burner Electric Stove 1.22 INDU STRI AI. WRITE FOR ILLUSTRATED PRICE LIST Neco Stain. Steel Flip -Flop Toaster 2.94 Novel -Aire 5 Tube Super. Radio 13.79 Write for Illustrated Catalog on Radios. RAB1REE'S Made to government specifications Lamps. ete. Phonographs, Electrical Appliances. Bakelite base -ROc ea. postpaid üIHOLESRLE ROO THE GATEWAY CO. Psry with order -Balance C.O.D. DALLAS 2608 ROSS AVE. TEXAS P. 0. BOX 926 BROCKTON, MASS. RADIO AND APPLIANCE, INC. Three new atomic age elements have stable," and francium, element 87, was SHEFFIELD now been named. Element 43, the first named by its discoverer, Mlle Perey, Wholesale Distributors is technetium, after France. Only element 61, discov- to be artificially made, 916 W. Belmont Ave.. Dept. RC4, Chicago 14, 111. from the Greek word "artificial." Asta- ered in the atomic pile, is now without tine, element 85, is from the Greek "un- a name. for APRIL, 1947 60 RADIO -CRAFT ALL ITEMS LISTED BELOW NOW AVAILABLE FOR

IMMEDIATE DELIVERY átam STOCK D/67.42/8 1T/NG COMPANY I- Our policy: All units are sold subject to one year guarantee THE NATION'S HEADQUARTERS I except when components are damaged through misuse. We do not solicit orders for any unit that does not meet our re- FOR TEST EQUIPMENT ! quirements for accuracy and honest value. Any item purchased from us is sold with the understanding that it may be returned for fun( refund after L a 10 day trial. The New 450 The New Model B -45 Model The New Model 670 SIGNAL TUBE TESTER SPEEDY OPERATION SUPER assured by newly de- signed rotary selector GENERATOR switch which replaces the usual snap, toggle. METER Self-modulated- pro- or lever action switches. vides a highly stable Specifications: 1 Combination ', OLT- signal. RF frequen- Tests all tubes up to O H M MILLIAMME- cies from 150 Kc. to 117 Volts. TER plus CAPACITY 12.5 Mc. on Funda- Teats shorts and leak- mentals ages up to 3 Meg - REACTANCE INDUC- and from 11 ohms in all tubes. TANCE and DECIBEL Mc. to 50 Mc. on Harmonics. Mu,iulation Tests individual sec- MEASUREMENTS. is accomplished by gridblocking action - tions in multi- purpose tubes. equally effective for alignment of ampli- New type line voltage adjuster. tude and frequency modulation as well as Noise Test: Tip jacks on front panel for plug- Added Feature: for television receivers. Self- contained ging in either phones or external amplifier The Model 670 includes a special GOOD - will detect microphonic tubes or noise due to batteries. All calibrations faulty elements and loose internal connec- BAD scale for checking the quality of elec- are etched on the front tions. trolytic condensers at a panel. Works on 90 to 125 volts 60 test potential of 150 Volts. Complete, ready to Cycles A.C. Complete with Complete with test leads $40 all operating instruc- operate tion=. and operating instructions 20' DEPOSIT REQUIRED ON ALL C.O.D. ORDERS GENERAL ELECTRONIC DISTRIBUTING COMPANY Dept. R. C. 98 PARK PLACE, NEW YORK 7, N.Y.

NEW! CRYSTRON LAPEL RADIO Nationally Known AUTOMOBILE ANTENNAS (Continued front page 57) Side Cow1-3 Section 66" Top Cowl (Fender Mount) -3 had worked exceedingly well in the Sturdy, Rustproof Section 56" aboratory and brought in every station $4.75 LIST $2.13 NET $5.95 LIST $2.58 NET within 200 miles with earsplitting vol- Deluxe Side Cowl -4 Section 100" Universal Cowl or Fonder ume. Fiercely proud of my revolution- Sturdy, Rustproof Mount -3 Soction 68" ary invention, I expected a fat check $7.45 LIST $3.36 NET $5.95 LIST $2.58 NET for my article. I explained the new principle of the All are comploto, ready for installation. Crystron to the Boss, who listened in- All aro chromo -plated. terestedly, if incredulously. Finally near the end of my technical talk he inter- rupted me impatiently, as is his VIBRATORS -Standard 4- Prong, CONDENSERS -.005 mfd. 1200 rather V DC Buffor Condensers habit. $1.40 each Taking the big cigar from his mouth 19 CENTS EACH -10 FOR $1.50 he snapped, "Well, Fips, let's hear that 10 FOR $12.50 100 FOR $12.50 -1000 FOR $100.00 Lapel Radio, and make it snappy." Smilingly I turned the knob. Nothing STANDARD DISTRIBUTOR AND SPARK PLUG SUPPRESSORS happened. I muttered, "Loose connec- 17 cents each Io for $1.50 100 for $12.50 tion, probably. It worked O.K. half an STANDARD VIBRATOR TRANSFORMERS $0.98 each hour ago." I then opened the set and fiddled around with it, while perspira- tion began to CROWE REMOTE SPECIAL-SPECIAL -SPECIAL drip from my forehead Vacuum Voltmeter and hands I St. Clair Tube -6 -but couldn't get a sound CONTROL AUTO HEADS DC Voltmeter Ranges-6 AC Voltmeter from the damned thing. In this excruci- Ranges -Ohmeter Range from 0.1 Ohms For All Makes, All Years $3.82 each ating predicament, every poro now to 1000 Megohms -Accuracy 2% Plus exuded hot, burning perspiration. My Tone Controls 1.71 " or Minus fingers and hands moved like a slow - Volume Controls .73 " FORMERLY $52.50, NOW $42.50 motion film -it seemed tortuous minutes before I could straighten out my body A COMPLETE LINE OF TUBES ARE NOW AVAILABLE from its previous bent position. *CORRECTION-HOLLYWOOD BROILERS-List Price $19.95 All the while the Big Boss, his face now an apoplectic purple, kept ad- Write for Our Latest Catalogue vancing menacingly. Already he had grabbed my precious Crystron Lapel RADIO PARTS COMPANY Radio, which -as if by magic -had now 612 W. Randolph Dept. "C" Chicago 6, Illinois (Continued on page 80)

RADIO -CRAFT for APRIL, 1947 61 ELECTRICIANS! RADIOMEN! TELEVISION FOR TODAY (Continued front page 38) Here's thBo kstoeBigger Pay! f these oscillations extend beyond the simple R -C circuit is satis- & RADIO damping ELECTRICAL blanking interval, they appear on the factory. In Fig. 2, this R -C filter is com- image. In the horizontal system, a bright posed of a 0.025 -pf condenser and 1,000 - TROUBLE bar of light will be seen at the left -hand ohm resistor across the secondary termi- side of the screen. In the vertical system, nals of the vertical output transformer. Il tpou the effect will he at the top of the image. An R -C filter is not feasible in the hor- SHOOTING ° U .1 M4 " In either instance, the oscillations must izontal network because it would pre- be killed before the blanking voltage vent building up the much larger releases the electron beam. voltage required to bring about the re- MANUAL In the horizontal system, the best versal of current during the retrace method of damping the oscillations is interval. 1001-E01 A with a diode tube. Yours for BIG Book In the circuit of V RN MORE with more than Fig. 2, a 5V4 -G is by quickly spotting troubles! lip,. ,;,. 500 large, 8' :- tells you look -how b, l r; I vlzkv book whereto x 11' Electrical shunted across the TIME -9- TIME - -- hat to do! 612 pages -8'.' z IF - really 4 books in one: (1) New Step -by- and Radio Shop secondary of the - StepTrouble Shooting. (2) 600 Shop Prints. (3) Electrical and Radio Diction- Prints! output transform- -NV\- R-ÖrIÚ`- ary. 44) Spare Time "Fill In" Job=. Take R it with you on every job- let it take you into the higher cr. The tube be- money bracket -put you in demand as "doctor" for troubles. a low- resist- Written by the Coyne School -an Approved Veteran Train- comes IRL ing Institution -and backed by 48 years shop experience. ance shunting path \/\ Coyne wants you to see for your- IRI1L TIME TIME-+ TIME SEND NO MONEt self how others have increased whenever the plates ,/3 their earnin through this hook. Read our FREE TRIAL - OFFER COUPON below, and rush it to us today. become positive. Fig. 4-How sawtooth voltage is obtained for magnetic deflection. During the nega- 7-DAY FREE TRIAL COUPON tive half of the transient wave, the tube One final word about the electromag- COYNE ELECTRICAL SCHOOL Dept. 47-12 Educational Book Dlr., SOD S. Psalms St., Chicago 12,1x. is non -conductive and its resistance is netic deflection system. The electron Send poste.. prepaid. r n Coyne Electrical and Radio Trouble Shooting Manual. Acier? days Free Trial. I'll -her infinite. Hence, with proper connection beam is centered by passing a direct return s óbw onths (Srr I'llpay 4d.96 crash pine.i 7days..nPsrie of the tube across the secondary wind- current through each coil. The current edition -thousands veld at $5.00). reduced on new large ing, there will be no loss of energy dur- may be reversed by rotation of the NAME ing the saw -tooth current build -up, but centering potentiometer, or no current be absorbed dur- at all supplied if there is no need for I AnuRESS___-- 1 sufficient energy will 1 1 ing the retrace period to prevent sus- centering. The centering potentiometer 'ITl'_ ,oxFv STATE I iPhn here'fr tM ule 1'.O.U. YuaMi t I tained oscillations. has a fixed tap. When the movable arm ierÌÑd,,,.v LerM =-._.-. : In the vertical system, the change in is at that tap, no d.c. flows through the coils. Opposite are obtained \ new "mena iry tube" multiplies two current during retrace is not as rapid as potentials in the horizontal s) -li i , therefore a on either side of the fixed tap. I ' :irit numbers in 0.00000001 second. Use these low-priced Diagram Manuals To simplify and speed -up radio repairs

trAr i .,rw`,V

Covering 1946, 1942, 1941, 1940, 1939, 1 1926 -1938 Each manual contains between 192 and 240 pages. Price each $2.00 _IL This volume $2.50 Service radios faster, better, easier. save money and time, use these most -often. needed diagram manuals to get ahead in radio servicing. Clearly ORDER COUPON printed circuits, parts lists, alignment data, service hints are the facts NO RISK TRIAL every day, you need to improve your servicing ability. Save hours each day, SUPREME PUBLICATIONS, 9 S. Kedzie Ave., Chicago 12, ILL. let these six volumes furnish diagrams for A0',ß of all sets you will service. Ship the following manuals: (Money back guaranteed) See Your Radio Jobber or Send Coupon+ '] 1916 G 1942 D 1941 D 1940 1939 1 1928 -1938 Price each volume only $2.00, postpaid 1 l $2.50 J

I am enclosing $ Fend postpaid. Supreme Publications 17 Send C.O.D. I am enclosing $ deposit.

PUBLISHERS OF RADIO ROOKS. VANUAi.<. ,, -::L DIAGRAMS Name:

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62 RADIO -CRAFT for APRIL, 1947 NEW "PRISMATONE" ORGAN ee (Continued from page 22) Two New

notes are tuned in one operation. A clear MUST space is provided at the edge of the disc. The wands below contain a pair of photoelectric cells and have holes Books drilled in their sides near one end to permit light to strike the cells. By inter- cepting the beam of light to a given key, the operator can produce any desired note. The shadow of the tube on the key acts as a guide. By turning the wand slightly, so that more or less light enters, volume can be controled. Output of the wands is to the high -impedance input of a high -fidelity amplifier. Since By R. L. Duncan Well -known educator and Radio.Elecnonms author, Colonel, Sir. Corps Res.; Member. Amer. Inst. o/ E.E.. Inst. of Radio Engineers, Veteran Wireless Operators' Asan. This Quiz Book is of inestimable value to This Dictionary of RadiaTelevision -Radar students, trainees and those with experience is prepared especially for technicians, stu- as a mean; for checking knowledge and dents, mechanics, operaltors, experimenters, training. It is tops as a pre- examiner for trainees, amateurs and others associated PHOTOCELLS radio license examinations. A highly practi- with the radio -electronics industry , . . ar- cal "True or False" type of question and ranged for ready reference and practical ap- answer treatise containing more than 1200 plication in one streamlined up- to-date book quizzes, plus the required circuit diagrams. containing Formulas, Symbols, Conversion This book points the way ... acclaimed as a Tables and various essential data, as well as superior means for determining the scope definitions of terms and technical expres- of your Radio-Electronics "know how ". sions encountered in the broad field of Radio -Electronics. *ea 7teed'744e $oe Es .. Orales ?ion Now! Only $2.00 for the Quiz Book and $1.50 for the Dictionary at your dealer, or if he cannot supply you, order direct. Remit by money order or check The two photocell operating wends. -do not send cash. RADIO -ELECTRONICS PUBLISHING CORP DEPT, RC4, 15 PARK ROW, NEW this may be any standard commercial YORK 1, N.Y. model, no mention of the amplifier is made in this article. For more spectacular effects, the LOOK! operator may wear finger rings with COMPARE! BUY! small selenium barrier -cell photoelectric SPEAKERS CONDENSERS Volume Controls Tubular Paper (600 V. Test) cells instead of the regular wands. 5" Alnico 5 Magnet, $125 oumontrol Mee. Price Ea. Per 100 C The present model has two full oc- p.m each wvitlh swe itcch and .01 .08 S 6.50 m" Minimum order, 3 i long shaft, ea. 59 .02 .38 6.50 taves, including sharps and flats (25 .05 .10 8.00 Alnico 5 Magnet, 90 Minimum order, 6 keys). A larger instrument can be built each .1 .12 9.00 .25 .17 13.50 6" ' "" Minimum order, 3 by using a larger tone wheel with a 15 ASSORTED .001 .38 6.50 suitable motor and projector. Two or All other sizes in stock, at money- Volume controls t195 .002 .08 6.50 saving prices. (less switches) .005 .08 6.50 more projectors can also be used, with .006 .08 6.50 as many keyboards as desired. By .5 .26 22.50 Money KITS .5 l Vinous" Electrolytics superimposing these keyboards on the AUTO RADIO Saving Ma. vDC Pr,ce screen many new effects be SUPPLIES Ieesisnsulaty,d R - Io 25v .25 can secured. 100 tart, , I s 2 $1.95 100 25v .55 4 PRONG Universal Watt 12 50v .38 non -sync. VIBRATORS.$] 39 Wire 16 I50v .35 20Aosorted 20 the BEST BUY Minimum order, E. Wound resistors 1.95 I50v .38 24 150v .38 in a COMBINATION TESTER 0Z4 TUBES, each.. P o p u l a r Assorted Minimum order, 6 1.07 50 Mica Condensers 2.50 30 150v .40 50 150v .50 RCP Model í02N A s t o r t e d Tube 8 450v .38 SPARK Plug SUPPRESSORS 11 20 Sockets 1.00 COMBINATION 10 450v .43 See our Catalog for full line of 16 450v .55 auto aerials. 20 Assorted Trimmers 1.00 20 450v .60 TUBE -SET I.F.'s 455 KC .45 40 450v .88 100 15v .49 PHONO SUPPLIES Illinois" Duals TESTER 16.16 I50v .58 Immediate Delivery Phono Motor & Turntable ...53.39 WIRE 20 -20 150v .65 30-30 150v from stock. Crystal Pickup Arms 2.49 .70 40-20 I50v .70 A complete tube tester and a complete set tester, Webster No. 50 Changer.. 21.17 50-30 I50v with 400 ft. (approx.) .70 only 5 simple switches to operate for both Webster No. 56 Changer.. 26.66 of 8 -8 450v .65 tube and set tester combined. Webster No. 70 Changer .. 43.20 wire in assorted colors 10.10 450v .70 RANGES and gauges, solid & 20-20-20 150v .99 Free $2.50 permanent needle with DO VM. 0/10/50/500/1000 at 1000 per a. stranded in 2 to 4 feet 10% discount on all eleetrolytia If ohms each changer. 99c \,' VM. 0/10/50/500/1000. lengths, per pkg. .... Purchased In lots of 10 er more. DO MA. 0 /1 /10 /100 /1000 DC Ammeter 0 /10. Mio Condensers, all sizes, Sc each. ohmmeter 0/ 500 /5000 /1,000,000/10,000,000. Lew ..hut center. COMPARE TUBES SAVE! D.B. Mater-8 /15/15 to 29/29 to 49/32 to 55 db. Four range output meter -same es AC volts. Size: 0Z4 $1.07 1T4 $ ñJSGT ..5.58 7Y4 5 .85 5085 5 .90 12%:12s5j6 inches. Weight: 11% lbs. Complete In IA7GT .85 395GT 1.00 6J7G .72 35W4 i handsome .50 17L7GT ... . 1.50 hardwood rase, with test 50 IRS .90 3S4 .90 6K7GT .68 leads, self -contained batteries, ready S39ar/-va MINIMUM ORDER, to operate. NET ISS .90 6F7 .90 6SK7GT .70 10 TUBES Minimum Order. $3.00 -20'/o with order, Balance C.O.D. -WRITE FOR CATALOG ADSON RADIO CO. Dept. C4 622 W. Randolph 221 FULTON ST., NEW YORK 7, N. Y. ELECTRONIC PARTS, Inc. St., icago 6, III.

RADIO -CRAFT for APRIL, 947 63 NEW IDEAS IN A V.T. VOLTMETER (Continued from page 32)

which are too far from the desired value should be replaced by others; those near enough can be padded by placing anoth- er resistor in series or parallel with them. As the ohmmeter range switch will measure resistors as high as 100 megohms, its insulation should be of ceramic material or equivalent to pre- vent undue leakage. There are two minor departures from conventional ohmmeter construction. The first is a provision made for an ex- ternal battery and the other is the addi- tion of a potentiometer, marked Battery Resistance Equalizer in Fig. 1. The standard for the 100 -ohm range is a 10 -ohm resistor and consequently, the current drain from a 1%-volt dry cell is 150 ma when there is no other resistance in series with it, as when ad- justing the meter for "infinite" indica- tion before each resistance measure- ment. Frequent repetition of this might exhaust the small meter battery in a short period. Therefore, insertion of a No. 6 dry cell is made possible for the lowest ohmmeter range by the jack (a regular phone jack with a "normally closed" break contact). The internal resistance of a dry cell increases considerably with age. This battery resistance is placed in series with the standard for the lowest resist- ance range. It actually forms part of the standard, and therefore, the internal Two more titles in this popular new battery resistance may greatly impair series are rolling off the press. The two the true readings before the meter bat- latest -described below -like the others, is Hence the give you the most recent, reliable tech- tery entirely exhausted. nical information and are as modern adjustable standard for this range in appearance as 1947 radios and cars. which should preferably be used with The type is fresh, clear -cut, easy to read. The books are bound in flexible covers, an external cell and the need for a re- smartly designed. In short, everything connected with these volumes is up-to- 5O each the-minute and practical to the nth de- OHMS Titles gree. You'll find them constructive helps 6 10 15 Nine Recent ¡n building up your knowledge of radio. KINKS NO. 31 RADIO QUESTIONS 29 HANDY CUTS AND SHORT AND ANSWERS 29 PATENTED Here are the answers to questions most UNUSUAL Box" CIRCUITS 19441946 frequently asked of the "Question 30 editor of RADIO -CRAFT. The material RADIO QUESTIONS selected is well diversified and chosen for AND ANSWERS practical application to workaday prob- 31 lems. Circuit diagrams are supplied with the answers. MARKD TECHNIQUESERVICE DC SCALE EVERY 2°s ROSS 100° 32 AMATEUR RADIO AMPLIFIER GUIDE NO. 35 33 BUILDERS BUILDER'S GUIDE RADIO the amateur operator who Fig. 5- Drafting details on the meter scale. AMATEUR GUIDE A book for BUILDERS builds his own. Practical and down-to- 3C.J earth, it tells you how to build trans- RADIO TEST mitters, receivers, and other ham gear. adjustment of the battery resistance :: INSTRUMENTS Construction data on a 430-mc trans- equalizer each time a new measurement 319 HK -24G c.w. transmitter, a r-7 ELEMENTARY mitter, an or a series of measurements is made. SERVICING miniature communications receiver, an 3/ RADIO acorn -tube preamplifier, and many others. p HOW TO BUILD Whether you're an amateur now, or just Hints for the constructor :- RECEIVERS studying for your ticket, you'll want 3RADIOv this book. to the grids short SEE YOUR DEALER Keep all input leads IF HE CAN'T SUPPLY YOU, USE COUPON to minimize stray pickups. Avoid shielding, especially in close RADCRAFT PUBLICATIONS, Dept. 47 quarters, to prevent shorts. 25 West Broadway, New York 7, N. Y. ( ) ALL NINE When going through the chassis use Send me the volumes (50c each, postpaid) checked. My dealer is unable BOOKS preferably of to supply. feed -through insulators, 29 35 the ceramic type (I -1, I -2, and I -3 I enclose S in the diagram). 30 Your Name 38 Use only the very best quality of mate- (Print Clearly) 31 rial available; mica condensers of Address 17 37 32 the working voltage indicated, even Dealer's Name if this voltage will never be ap- 0 33 38 excellent in- Address proached. This provides 64 RADIO -CRAFT for APRIL, 1947 snlation. For the same reason, hook- up wire, resistors, etc., should all be of the very best; they will be cheapest "ROBERTS" in the long run. Before starting, plan and make a COMBINED PORTABLE TUBE and CIRCUIT ANALYSER sketch of what you want to make; a The Most Modern Service Instrument Leer Offered to the RadioService. test bench instrument such as the one described here or a portable unit. For Test Tubes for Current. is any electrode, A/C & a portable unit which to be used D /C, 11 ranges 0- 2.5 amps. MEGS IOOK OHMS Tests electrodes for Volts, 10 000 any electrode, A/C & D /C, 16 Ranges 0- 1000. 1000 Does the above testa SI- MULTANEOUSLY. Checks resistance any elec- 00 100 trode, Tube to Chassis, 3 Ranges 0- .5 megohm. Can he used as Universal Meter, 2000 ohms per Volt. (NOTE: MARKINGS EVERY 30° ACROSS IBO °) Meters protected against overload. B.S. Stan- RESISTANCE dards. Moving Coif 25 10 Movements. Meters Glass Toughened, S Scales 31/4", e a s i l y READ. Invaluable for testing loo A/C & D/C Radio Re- ceivers. All the ADAPTORS sup- plied with the "ROB - ERTS" are ready wired. Guaranteed for 12 (NOTE: MARKINGS EVERY 30° ACROSS 150 °) MONTHS. 12":12": - 6'A ". Weight Approx. 13 tbs. VOLT;, Pig. 6- Markings for Volts and Ohms switches. Until now, the fastest and most reliable Method of Analysing faults In Radio, has been the Signal Tracing method with the aid of PRODS. We have gone one better In our endeavours to give the radio serviceman BETTER ANALYSER. Our ADAPTOR in small quarters the following omis- SYSTEM worked In conlunction with the "ROBERTS SWITV'B" (World Patents) putt this ANALYSER right sions are suggested, some of which at the TOP as the MOST MODERN & EFFECTIVE ANALYSER ever produced. have already been indicated in the The "ROBERTS ANALYSER" has made the prod system in circuit testing OBSOLETE. By the "ROBERTS" Method every Tube Circuit Is fully tested without even disassembling the Chassis & aB foregoing text: Radio Service-men will appreciate the simple and effective method of operation, apart from the time saving element so often the difference between Make the instrument do profit and loss. "fixed," i.e., Some 35,000 "ROBERTS ANALYSERS" have been sold or ordered In the past six months by Radio men In away with all the readjustment po- countries abroad. We now take pleasure in offering this ANALYSER to American Radio Service-men. tentiometers for the low- voltage cali- Pries, F.O.B. Verdun. Canada, $129.00 complete. All orders C.O.D. For further information write for our Bulletin:- brations and the volts x 10 adjust- JOHN AMBLER, ADVANCED ments, using fixed resistors instead. RADIO PRODUCTS 330 SIXTH AVE., VERDUN, QUEBEC, CANADA

ARMY -NAVY Come to the famous HEAD PHONES SHOPS OF $249 COYNE Or whereyou'learn by doing" ,.p.

buy; "FOR RADIO ¿énmode ELECTRONICSTELEVISION Cotp FREE Catalog IN A FEW WEEKS polor &%'polt k9sct,gs. o Prepare For A s2 .A9 pna 0. S11' Good Job Now With e A Lifetime Future! Reó9O,der No,\T Trained Radio men needed now. They will be needed too, in the years to come. Don't be caught napping. Get a Radio training now and be ready. Learn by GET THIS Doing. Free employment service for life after grad- catalog, lotest devel- uation. Many earn while learning. If you are short The voltage of range adjustors are well seen here. opments in rodio and money, ask about our Student Finance Plan. Now r added Training in Electric Refrigeration. We are electronic ports and de also equipped to train those who alify under G. I. Modify the probe support so that it vices, newest ham gear, Bill. Men with Physical Disabilities may qualify gadgets and bargains. for training at no cost to them for tuition and sub- can be mounted flush with the front . sistence. Mall coupon for detalle. panel. Omit the regulating .r.i.. SEND COUPON FOR FULL DETAILS tubes BURSTEIN.APPLEBEE CO., and replace them by a wire -wound 1 1012 McGee St., Kansas City 6, Mo. B. W. COOI(E, Director, Radio Division (:DYNE ELECTRICAL SCHOOL center-tapped voltage divider. ._ . - .. Send me your new FREE catalog ll 500 S. Pauline St., Dept. 47.8H. Chicago 12, III. . -Send me pairs of phcr ..> or -end Big Free Book; also details about Coyne Patt- Calibration and scales 52.49 plus 20c pair postage. I enclose i one Employment and Student Finance Plan. 1 G. I. Bulletin Physical $ _- __ -in poyment RC Send Disability Fig. 5 shows the scales for the com- 1 NAME NAME pleted instrument and Fig. 6 the mark- 1 AGE ings for the VOLTS and OHMS range 1 ADDRESS ADDRESS switches. 1 STATE (Continued on page 66) la -W-elm PITY STATE

RADIO -CRAFT for APRIL, 1947 65 NUMBERS 2 and 3 OF THE NEW IDEAS IN A V.T. WALSCO STAPLE VOLTMETER R CjEßO -flit Parade DRIVER (Continued from page 65) Pays for itself on the first job For a voltage supply of ITS HERE THE NEW, COLORFUL A Tonal tool calibration, for installing wires 100 and 10 volts both a.c. and d.c. of EASY TO APPLY and cables, that sufficient current output, together with saves time and FELT mosey. a reliable standard meter for 100 volts Used by Radio. a.c. and d.c., is required. Public address and FLOCK Intercom Techni- The 100 -volt and 10 -volt potentials cians. can be subdivided by decade resistor di- FINISH Staples Into and other Inacess viders: These dividers can be made up ibis places. for the 100 -volt and the 10 -volt sup- COMPLETE FELT FLOCK SPRAY OUTFIT Staples on hard surfaces such as plies of 10 wire -wound resistors, com- Now you can do your own finishing of: Radio cabinets plaster, hardwood, pared and equalized by using an ade- and speaker grilles, phonograph turntables and record etc. Can be loaded in quate reading on a regular ohmmeter Cases, novelties, crafts, hobbies and numerous other 10 seconds. scale. Remember that the higher the Items The Walsco Staple Driver Is a current capacity of the supply, the low- tool colors available. The kit (as pictured) con. real time and trouble saving er the resistance of the resistors of the IO brilliant for the radioman. Also extremely tains patented WALSCO Felt Flock Spray Gun, together useful for general stapling. decade units can be and the smaller the with necessary materials, such as undercoats. Ivory and This device automatically positions error will be when shunted by a high - which it is driven brown felt flocks, brush, instructions, etc., the staple after to a pre -adjusted depth with one impedance meter to be calibrated or CATALOG NO. K -50 -List Price $10.75 or two strokes of the palm of the checked. hand. A small trigger controls the Write for full information on these Items. Dept. 41 feeding mechanism. Wires and With the above equipment available, cables up to 1 /4n in diameter can precise readings are obtainable on the be quickly installed with the Walsco Staple driver. vacuum -tube volt- ohmmeter or other Price $4.95 Dealers Nef lie meter to be calibrated from 100 to 0 eluding box of staples) u p T h R o d i o/ M a n volts in steps of 10 volts and from 10 to 0 volts in steps of 1 volt. A nice test bench and calibrating source of voltage and power, either reg- VOLT- OHMMETER ulated or nonregulated, may be easily de- EASY TO LEARN CODE ELECTRONIC vised when a few old power transform- 110 VOLTS AC 20 RANGES ers, preferably with 5 -volt and 2.5 -volt It Is easy to leans or increase speed 0/5/t0/50/í00/500 /1000 /5000 volt. DC and with an Instructograph Code Teacher. 1185 AC. 0- 1.000.000.000 ohm. In six over center -tapped windings, a rectifier tube Affords the quickest and most prac- lapping ranges. Seosltivity: over MILLION for the high -voltage d.c., and copper - tical method yet developed. For be- POSTPAID OHMS per Your on 5 volt range. ginners or advanced s t u d e n t s. Complete kit includes all component parta, tutee oxide rectifier for the low voltage are Available tapes from beginner's drilled beautifully enameled alphabet to typical message. on all punch edPaand lechaand wÌnd handy. The author made one out of subjects. Speed range 5 to 90 WPM. t elideback circuit developed during war by three transformers, supplying 150 Always ready -no gaUL scientist at the California Institute of Technology give. senaitivlb and aexibtlity while completely Ilm- ma 250 d.c., 0 20 ENDORSED BY THOUSANDS! imasingnating necessity of abatteria and ive meter. Each at volt to volts a.c. instrument to individually calibrated.Dial scale over The Code Teacher nine Inches long! (by putting the 2.5- and 5 -volt windings terally [takes tehplace an and enables to In addition to performing the usual volt -ohm functions. in series) and 250, 500, 750, and 1,000 Ì a and master code without fur. this Instrument easily measures these voltages: SUPER. Nern sistance. Thousands of su sful one ton bays. HET volts or more a.c. at about 100 ma. red Ule code n the Ineanretegraph System. GRID BIAS CELLS withwithout affecting the circuit MeasurresMeasures ',wine for convenient rental and marcha.. Diane the exact leakage resistance of INSULATION. TUBES. CONDENSERS. It can be used with a signal generator ter SIGNAL TRACING. The paste -up meter markings INSTRUCTOGRAPH COMPANY STERLING ELECTRONIC COMPANY Professional- looking scales and mark- 4701 Sheridan Rd.. Dept. RC. Chicago 40. III. Its N. Sierra Denies Ave.. Dept. 2, Pasadena 4. Call /. ings as shown for this meter were made by careful drawing of the scale or marking at twice or more its original MYSTERY ONLY MOTOR The of SELF ELECTRIC size. For the lettering, paste -up letters CONSTRUCTION KIT used in making show window signs and Unlock the secrets of Sei/i ' Explore your mental world. EASY TO ASSEMBLE price tags were used. These were ob- Receive the keys to the bid- tained in New York from the Tablet den laws of life. Become the FUN EDUCATIONAL master of your affairs...the - and Ticket Company, but as they are creator of your own happi. IDEAL GIFT used by all stores, no doubt a local mess. FREE book explains. Runs on a Single Dry Cell source of supply can be found by asking Write: Scribe O.T.V. lest ;winded). Use It to run Toy Pumps. Paley., Eto. your store manager. 9úe ROSICRUCIANS CHECK-MONEY ORDER or After these India -ink drawings were (AM ORC Wen rink) to CASH (at your finished, a photostat negative of the ex- Sao Jose California 17. N.Y. The Haydn Chem. Co., Dept. Ul, Box27, Kenmore act size required was made, from which any number of black-on -white scales of SERVICE MEN! WAR SURPLUS the correct size may be obtained at any RCA Radioiren states.. Lathes, Milling Machines. Drill Pressee, Sawing time. The markings were left in the Sylvania QT-1 55.24 miscellaneous Raytheon Nylon Crya- equipment. Stators and thousands of on helicopters. Sleeper Trail - deep brown background of the negative Tubea. Part, Equipment tats ach BMA Also Information i ers, Power Lawn Mowers. Welders. t Dept. C2 Garden Tractors, with white lettering by making a nega- Write for our late tulletin, Jet Impulsion for Care and Tractors. Farm Conveyors. Distributors of RADIO EQUIPMENT Dump hoists for trailers and wagons. etc- tive from a reduced positive. The re- THE WAYNE ENGINEERING CO. duced scale was pasted on the original ELECTRONICS DEPT. 1120 GREENVILLE. OHIO metal scale plate of the meter. 104 MAIN STREET, POUGHKEEPSIE, N Y The Sauar. Dal supply Haufe No expensive drafting equipment or $3.00 FOR CARTOON IDEAS lettering sets were used in the making ItADIO- i7tAIT prints several radio cartoons every of these items, and they can be simu- SURPLUS mth. Readers are Invited to contribute humorol ritti. ideas which can be used in cartoon form. lated easily by anyone with average 12 lbs It is not necessary that you draw a sketch. unless you wish drafting skill. A gold mine of parts for repairmen. amateurs, and ex- IDEAS NOT WANTED perimenters . sockets, condensers, resistors, trans- No electrical or radin definitions wanted. Some of Should there be sufficient demand. a future former., coils, hardware. wire. etc.. etc. An outstanding !belie were published in the past, but the subject is article will be devoted entirely to the making of oaritain In usable parts! Send $2.00 cash, check or M.0. about exhausted. such scales and markings and the calibration of All checks are on today! (Pay small express charges on receipt.) payable publication. meters of high input resistance in general, using Address RADIO CARTOONS. RADIO- CRAFT, 25 the meter here described and some other simple ELECTRONIC PARTS, Inc. West Broadway. New York 7. N. Y. but generally useful equipment. as a practical Dept. C4. 622 W. Randolph St.. Chicago S. III. example.

66 RADIO -CRAFT for APRIL, 1947 TRANSATLANTIC NEWS HAS at (Cmifitttted jrohl gage 39) HARRISON HAS 1T! HARRISON the transmitters of the television chain soon to come into being here. Now, it We are Factory Authorized Distributors for the top quality manufacturers and we is almost certain that this will not be now have in stock lots more new, latest improved production ham gear! Visit our stores so. The reason? Interference caused by today, for everything you need. We promise you fresh, clean material- quicker-at aircraft in flight. Have you ever seen the lowest current prices -and, above all, our sincere desire to be of friendly, helpful it on a television screen? I saw a strik- service. ing instance the other day. The scene As one of the world's largest distributors of Communications equipment, we are on the screen became blurred and rather delivering plenty-right now! ALL MAKES -practically all models. If you want yours muzzy. It was particularly noticeable in the quickest possible time send your order to HARRISON! that well -lit stationary objects had a Send in your parts orders, too-If it's new, if it's good, if it's made by a leading double outline. Moreover, the rather manufacturer- faint shadow outline of each was grad- Harrison Has It! ually moving in toward the real one. That reflection was caused by a low - RECEIVERS flying plane, passing near an imaginary COLLINS: HAMMARLUND: line between my 75A-1 $375.00 IIQ -129X. with speaker In cabinet $173.25 aerial and the trans- SPC -400X New "Super -1'ró' .55 to 30me, with mitter. The reflected waves, HALLICRAFTERS: pack, and speaker in cabinet 347.25 arriving by SX-42 now NAI-.tAl .54-116 mc NATIONAL: a longer path, produced the displaced $275.00 240 -D, with speaker 241.44 leas speaker NC- secondary outlines. These moved in- NC -46. with speaker 97.50 8-06A, b91-AM-CW 27.8-143 111tO -5TAI. with pack and speaker 306.71 me 307.50 ward as the plane's approach reduced 1 -10A, with tubes 67.50 the difference in B-37, BAS-AAs 130-210 mc 591.75 RME: length between the 5-40 89.50 RAIE. 45. with speaker 198.71 direct and reflected paths. Trials have s-58 47.50 RME 84, with speaker 98.70 shown that this sort of interference TRANSMITTERS would be widespread with radio links COLLINS: TEMCO: and for that reason the television trans- 32V -1 $ 475.00 80K -i, complete 75GA s 498.00 mitters in different parts of the country with 310A -1 ox- 5000.t 6800.00 citer 1.250.00 ARROW TR -411. New 2 meter will be interconnected by co-axial cables. MEl'K 60T 150.00 transiuitter- receiver, with tubes 59.80 OTHER MODELS AND MAKES WILL BE IN STOCK AS THEY BECOME Television screen sizes AVAILABLE Some extremely interesting informa- Complete stock -quicker deliveries -lowest prices-top trade -in allowances -easy tion about television picture sizes was 6% Budget Plan, if desired -and my personal attention to your wishes, all insure your complete and produced during the recent discussion lasting satisfaction with every transaction. I guarantee you'll like doing of the subject by the Radio Section of business with me! the Institution of Electrical Engineers. Send me your order, today. A small deposit (you name it) will bring There can be no doubt that people want you your new equipment. Balance C.O.D., or tell me what Budget Plan a larger screen than is now available terms you want. and that there will be no rush to buy Twenty -two years of experience serving Am- televisors until they get it. Hitherto no HARRISON one has been able to say why ateurs in all parts of the world is at YOUR com- this SELECT SURPLUS mand. should be: a 12 x 10 -inch image viewed Bead our ads real at about 8 feet has exactly the same surplus material. priced - hon- angular dimensions to the eye as a home estly described - gtunn- Vy 73 de P Y7 r' moving picture 3 feet x 2 feet x 6 inches "take chance.'i you buy Hammon Select Sur - viewed at 24 feet. But there is no ques- pluel !S[ t77i1on. W2AVA tion as to which is the more pleasant to watch. Why should this be? One speaker hit the nail on the head, I thought, clearing up a point which has not previously been explained. At 24 t ARRISON RADIO CORPORATION -', feet the eye adjusts itself to infinity I. focus, a restful condition. At the short- 9 WEST BROADWAY NEW YORK CITY,'7; ?'T er distance it is always rather strained. PHONE- eA.tlay- 7`9ß'S4 E*PORT DIPT.-CAa1E- "NARRISORAD" } The argument was clinched by another JAMAtA -,6Rj4 HT172-31 Hillside Ave.- REpublic- 9.4104 I speaker who had tried cine pictures of 10 x 8 inches -viewed at a distance of 6 to 8 feet -on his family. Their objec- tions were violent! There is no doubt AC. CURRENT ANYWHERE! PREPAID ASSORTMENTS in my mind that television With will always Katolight Plants and Getleraton be a semi -flop until we can give the Furnish GUARANTEED FIRST QUALITY Curren as ' theen highleen . 100 1/3 Watt Realetnn All Insulated.... 52.98 viewer a screen measured in feet rather Sizes 500 mate to 100 KW. 100 4k Watt Resistors All Insulated 1.95 Also Manufacturers of Rotary 100 1 Watt Resi stop All Insulated 4.45 50 2 Watt Resistors All Insulated 3.98 than in inches -and we cannot do that Changers. 32 'and 0n Voit 50 200 Volt Paper condensers 2.49 D.C. Motors in ta,i 1/3 and 50 with the cathode -ray tube. Never in his- 49 R.P. A.C. Nolan. afitgle 0 Dry Electdrolytic Filter Condensers 5.75 phase in 112 and 2 R.P. 25 ft. tory has there been a bigger opportunity ha 10 nd TooneControl No Switches 1.98 100 ft. Spaghetti and Vlnylite .95 than the one which now awaits the in- KATOLIGHT Coils 120 Rock St.. Mani ato, Minn. 20 Wafer andCeram' c Band Switches 3.95 ventor of a system which will 20 Auto Su n 2.98 emanci- 50 Electrical Devices. Plugs. Taps pate television from the cathode -ray Bases, emnts Funs. 5.00 SEND FOR TEUTON, COMPLETE RADIO AND tube screen and the scanning time base ELECTRICAL LIST Terms: 25í'F deposit required with order. Helene. NEW HANDY LAI. DIAL. Simply turn the movable C.O.D. Merchandise sent prepaid If full re. Miniature Spot -Welder dial to the tube number desired onn the ROTA -RASE immure accompanies order. and complete corms Instantly Indi Some months ago rated on the "prong' diagram. Filament. End. piste, TRUTONE PRODUCTS CO. rumors circulated mode, etc.,etc. to o ttan 300 tube types given. 303 W. 42nd St. Dept. C New York 18, N. Y: of a small -welding No more time Itrt on lengthy reading o spot apparatus, suit- thumbing of pages. ROTA -BASE. actually ives r "Meng" pictu f th. e connection.. PRICE: NOW able for making the connections usually ONLY 51.00. Postage prepaid or sent C.O.D. plus soldered in radio gear, which had been postage. Money back If not delightfully pleased. REED MFG. CO. i249:1«." The most common trouble in television seta (Continued on page 68) reported to date is rectifier failure. RADIO -CRAFT for APRIL, 1947 47 TRANSATLANTIC NEWS SCOOP! (Continued front page 67) ARMY BC -645 ., ' I.F.F. UNIT. Nat eta. Fa` ' $16.95. ka ly in the evolved in Germany during the war and the fingertip (remember that the fin- ei. 1 Qe oar. nhru radar .., picket uP a plum, used for the construction of delicate ger pressure mast be light), bringing #~. note, was traya into contact with the Il 14 k owins nuwhether electrical appliances in which complete the carbon again a j-_A -, 11 was friendly or reliability was essential. To track down work. The result is an intermittent arc, A L t.KL .., not. That was be- fore BC 695 was the makers and to obtain technical de- between the carbon and the work, of . -.. invented. BC -695 out a signal tails proved a long and difficult business, heat sufficient to make the metal parts 13. r. .- 1 : I. : :.r, American. It probalilY I been able to do flow and become firmly welded together. initial nu el lites 111.111 any otite piece of electron', but have at last this. equipment made. With some mot illations the set can Here, published for he used for 2 -way communication, voice or code. on the following bands: ham band 920.450 me.. citizens the first time, are ELDING HEAD NSULATED HANDLE CTUATING KNOB radio 460.400 ter.. fixed and nubile 450 -460 ma, television experimental 970.500 mc. Equipment unable particulars of a de- METAL TUBE IRON CORE of doing the Jolis of the modtfl d set sella for hen- ',,i9 and hundreds or dollars. T le 15 tuba alone are vice which played Ih toto-e than the sala price. 4 -741, 4 -7117. -7E6, an important part 7.;Fd. 2 -955 and I -Wr ltA. It now covers 960 to 490 r LEADS TO TRANS. toe. I:ach 1C -615 is shipped wl It a Belmont factory in the production of printed conversion diagram. shooing how to make AC power sup :dy moiulator and how to make Transmitter several of Hitler's ILUG CARBON INSULATION SOLENOID and receiver changes. Slat llama and experimenters weapons. already have tito few parts necessary. New 111'-045 secret Fig. I- Cross -section view of the small German radio spot- welder. with tubes less hover Supply $16.95 The cylindrical Two for 32.90 The lug at left end is the work being done, not part of the fool. handle of the tool is SENSATIONAL SURPLUS BUY made of plastic material and is about ' Parts made of most of the commonly - - BC- 654 -A. Transmitter- . Receiver 12 watts CW. 8 10 inches in length by 1 inch in diam- used metals and having cross sections watts Phone. 3800 to 5800 - KC $19.95. Used but in eter. Fig 1 shows the working parts. A not exceeding a diameter of 1/4-inch can :.pparently good order. 2 nnrered with 3-307A tubes kind of steel nozzle at the end of the be welded in this way in from 'á to * L a Inn less receiver tuba. handle forms the welding head. Free seconds, according to their nature and The 7 tube superset re- Sei sir Iras 2 It? stags. to move in the aperture of the head is size. The only common metal that can- N' volt ..... Resigned for 1% - aril tubes. Could be con- a rod carrying a carbon electrode. On not be welded at all is zinc. Some metals, vened to heater tuba. such not weld Has built in 200 KC crystal calibrator. The 200 KC the rod, which can be pushed forward as bronze and silver, do costal and 0 -3 BF thermocouple ammeter and 3-307 into the aperture of the head by pres- easily ; when they do have to be joined, tubes are worth the price we are ask nit for the whole unit. First come first served. IBC -651-A transmitter- sure on the actuating knob, is mounted this tool provides a ready means of rat leer less power supply. Eaclt $12.95 With all tubes and opera 16.95 the iron core of a solenoid. Two leads making firm, secure joints by the proc- run through the handle to the low - ess of hard -soldering. 1947, COMPLETE RADIO KITS voltage side of a line transformer. One SENSATIONAL PEE WEE AC- The ordinary soft- soldered joint is OC KIT Model KPW. Size 614x of these is connected direct to the rod to be a spot in 5x3% inches. Very small In size; always apt weak radio uses pee ore tubes 1115. IT4. carrying the carbon; the other is con- and electrical apparatus. With spot - 185 and 3S4 and new dis- disc rectifier. Convent fatal superhrt nected through the solenoid to the weld- welding dry joints just do not happen circuit with AVC; 2 gang con- ing head. denser. Receives broadcast 550 and, as no flux is required, there is no to 1700 KC loop ant. This set The aperture of the head is placed fear of subsequent corrosion. when wired according to our over work and tool diagram will make a hot little the the is pressed Mechanically-minded readers may personal radia This kit is priced complets; Jest as well down so that the head makes good all our kits are. with tubes. cabinet and speaker: like to try their hands at making up nothing else to buy Net $11.95 electrical contact with at least one of small spot -welders on these lines. For 5TUBE AC RADIO KIT the two parts to be welded. The actuat- their guidance, the carbon should have superhet circuit using new pressed permeability tuning unit. ing knob is now gently with the a diameter of about 6 millimeters and Covers broadcast 550 to forefinger. This causes the carbon to 1700 RC. Beautiful wal- the low -voltage winding of the trans- nut cabinet 12g7ze 5' AS travel toward the work until contact is PSI speaker. Loop ant. former should be able to supply up to Everything complete. In- made. As soon as this happens, current 10 amperes of current at 20-35 volts. cludes 88AT. 68H7. 88QT. passes through the windings of sole- 6K6 and 61-3 and diagram the This seems a heavy load in comparison Model H -5A. noid, which now exercises a pull on the 516./6 with the electric soldering iron, un- iron core mounted on the rod. til you realize in welding no current KIT K -7A T tube AC Superhet 550 to 1700 KC. llaa The rod is retracted and an arc push -pull eudho staco with tone control and 6% in thus whatever passes except in the brief alnico 5 I'M speaker. Conventional circuit with AVC. is formed on the "break"; but the ac- Similar in appearance to male) K -SA exc.pt has periods in which a weld is actually in slightly larger cabinet. Loop ant. Everything complete tuating knob rebounds from the pad of including diagram and tuba 6807. 68K7. 6K6, 68NT progress. 2-608, 5Y3. A real value Net SI9.9á DRUMS AC -DC KIT J -De Beautiful all teporto to buttÌ CANNON -BALL a broadcast 550 to 1700 KC 5 tube AC -DC radio. Superhet with aide rule is a good Headset dial. 2 gang tuning woo denser and loop aerial. guaranteed to satisfy Everything you. For sensitivity, paranderle iui s 12K8, 128E7. 12607, 5525 and 50,0 and dia- clarity of tone, de- gram. Kit J -D5. pendable performance, Net 9í1.9B use a Cannon -Ball BARGAINS IN TUBES NSW PLASTIC CABINET Eoiittlrltaaalli' Headset. Folder R-4 BRAND NEW Cabinet size? Btlal0 ¡T. - Neavy Aar mat. illustrates complete Attractive elide rule dial. f nets greatly is. INDIVIDUALLY BOXED 2 gang tuning wow, amif w-.l, crease Decir SIR - line. Write a broadcast 550 b, I,.g., 00 000. 114 List $2 9 Your Cot S .99 1050 KC. lise latest Al- 1316 List 2._h9 Your Cost 1.09 5 PM speaker Loup - 1.09 antenna:tonna: all parts anion- a C. F. CANNON COMPANY 185 List 2.20 Your Cat Red diagram and tube,. - 'IV:. Y. 1T4 List 2.20 Your Cat 1.09 i _ 6PRINGWATER, N. 2117 1.90 Cost .99 12E8, 125K7, 12v07. - - List Your 50L6 and 2525 furnlaned. 2x2/879 List 3.20 Your Cat 1.50 Kit P -48 Net 513.96 3A5 List 2.20 Your Cost .99 ilQadsat #12a4uaztarl 3914 List 2.20 Your Cost 1.09 Taro -Tuba Phono Oscillator, $3.69 3S4 List 2.20 Your Cost 1.09 COMPLSTE. WIRED and TSSTS°. 5Y3OT List .95 Your Cat .55 SOO to 1500 KC. Model 0 -4. Has BAC7 List 3.20 Your Coat 1.60 t audio stage for pmt e 6A05 List 3.50 Your Cost 1.90 power output. Complet with OAK; List 3.20 Your Cost 1.99 musa sil to operate... 63.6e OPER Is List 2.6$ - Your Cat 1.40 Mike Oscillator -noel Is 8R40 added noel e -4 or et has RADIO BOOKS 125 6B7 List 1.80 Your Cost .99 added gain tags for TITLES BBB List 2.65 Your Cost 1.40 mike. tube,. 6C8 List 2.20 Your Cat 1.09 faderermoro 54.95. Crystal BY MAIL IN STOCK Your .69 mike 54.90 extra. end List 1.35 Cost Thousands of other tubes and radio supplies on hand. zoo'. DEPOSIT. BAL. C.O.D. WRITE FOR FLYER. ISAME -DAY SHIPMENT ON 987,, OF ALL MAIL ORDERS. Write for bulletin No. 28. Backt of nearly all radio pubtdwrr. If you do: t Eno. price, sad deposit red well shop C.O.D. McGEE RADIO CO. Ze SOUND EQUIPMENTCO. 1225 -C McGee St.; KANSAS CITY; MO. `rá1car Lao To EDITORS AND ENGINEERS, LIA. aile 911 -913 Jefferson Ave., TOLE00 2,0Hí0 13051tonwood Road Santa Barbara, California

68 RADIO -CRAFT for APRIL, 1947 ANTENNA PRINCIPLES (Continued from page 21) Make Money In Radio These publications will show you how to do radiation and consequent power gain it are almost doubled because both re- HOW TO MAKE MONEY IN RADIO by Ivan D. Long, president of Western Radio In- stitute, Inc. A complete manual for opening and flector and director influence radiation conducting a money -making Radio Service business. How to choose a location, How to similarly. The reflector element is gen- Advertise, How to Keep Records. How to Handle the Customer, How to Relieve the Service Man of Un- skilled Jobs. How to Service Radios by the Step -by -Step Method which is easy erally 5 percent longer than the half - to follow and covers every type of radio receiver ; includes a proven Schedule of Prices. wave radiating dipole; the director 5 No radio man can afford to be without this book. Postpaid $495 percent shorter in length. The im- SERVICING THREEWAY PORTABLE RADIOS, by Lyle C. Treakle, Chief Instructor West- is by ern Radio Institute, Inc. A simple discus- portant factor of phase controlled sion of how to handle these tricky little portables and make money from servicing them. these dimensions plus the structural Breaks down the circuits of each type. shows how to service each difficulty and how spacings between the parallel elements. NOT to damage the set while repairing it. Available for immediate delivery. Postpaid 62.911 FCC SIMULATED PRACTICE EXAMS -By Lyle C. Treakle. If you can pass these tests Spacing is important. And optimum you can be reasonably cure of passing the official FCC spacing -in terms of relative field examinations. Available for Elements 2. 8, 4, 5, 6. Five different "multiple choice" type exams for each element, with answer sheets for checking your results. State element strength, or power gain -may be de- for which exams are desired. Per 6 exams for any element, postpaid S125 termined from the design chart, shown QUICKREPAIR CHARTS- Short-cute to repair any radio receiver. By Lyle C. Treakle. in Fig. 3. State whether for AC- Superhet, AC- DC- Superhet, AC- For maximum power gain use of a TRF, or AC- DC -TRF receivers. Per chart .SO AVC MADE EASY, By Lyle C. Treakle. A simple analysis of Automatic Volume Control reflector with a dipole requires a spac- service problems. Covers Delayed AVC, Amplified AVC, and Quiet ing between 0.2X and 0.25X. When a di- AVC. Has descriptions and circuits of various systems used. Each, postpaid .75 rector is used, the spacing is more criti- Order from cal, the optimum value being about O.U. Combining a director and a reflector DALE'S OF DENVER to influence the radiation of a half -wave Publishers dipole causes a two -fold increase in both 510 15th Street Denver 2, Colorado field intensity, directivity, and power gain. Because the three elements are

REFLECTOR DIPOLE DIRECTOR CODE CARD SYSTEM

Removable Self- Starter Strip exposes ends of 1 +5els far you to peel!

er i DON'T PICK. USE SELF -STARTER STRIP TO PEEL LABELS k-.26 +h-,I A I - 3\ 4 5 6 7 8 9 10 REFLECTOR DIPOLE DIRECTOR DIRECTOR tue so 2 3 4 5 6 7 8 9 to 4:ó0 12 3 4 5 6 7 8 9 IO t a i a8 1 2 3 4 5 6 7 8 9 St 1 2 3 4 5 6 7 8 9 1 Cf 3 1 2 3 4 5 6 7 B 9 101 g\ a DON'T PICK. USE SELF -STARTER STRIP TO PEEL LABELS. (t,ISA 4..1A -4J5/t+1 REFLECTOR DiECTOt. DIPOLE

LIKEWISE ONF[AT SURFACiS

\\Ile-JA -144-35A 4,15A+J5A+I Fig. 4- Directivity is increased by increasing number of elements. Paso Pend Iny arranged parallel and in a horizontal mately 15 degrees QUIK- LABELS code Wires, Leads, Circuits, Relays, Parta, etc.. faster and cheaper. Pre-cut to exact size. QUIK- LABELS come on handy cards. plane, they are known as horizontal in width. Ready to use, they stik -quik without moistening, replace slow and costly arrays. The array (Fig. 4) produces a Four directors string tags, roll tapes, decals, stencils, metal tabs, etc. Resist dirt. grease, oil, abrasion. Self Starter Strip automatically exposes ends of Labels horizontal radiation beam with a width with a dipole and for you to grasp instantly -no more finger -picking. of about 60 degrees, measured at half - reflector are used power points. on each of four W. H. BRADY COMPANY Established 1414 Addition of a second director provides "legs" of the ex- Manufacturers of Self-Sticking Tape Products greater power gain and more directivity. tremely directional 802 N. 3rd STREET, MILWAUKEE 3, WISCONSIN array of a U.S. I'm interested. Send me all the facts on QUIK -LABELS. Dimensions of the second director are Name Title the same as those of the primary direc- Army combat ra- PLEASE ATTACH TO YOUR COMPANY LETTERHEAD tor, but the greater spacing between the dar set. Consisting two directors should be noted. Beam of 4 phased sets of horizontal arrays, Do you nee width of 40 degrees is typical. the antenna can be considered as an array of arrays. The combined radia- BINDING POSTS? Such an array is standard equipment tion pattern provides a very narrow Th XL PUSH POST with Its Sprint Astton r.e Constant Contact nd for radar -equipped RAF night- fighters beam less than 8 degrees in width. uulck soonest Ion. Mani.factnlr.a In All Aluminum Typ. M (Photo C), and is also used for other Almost any number of directors can iit I3e .. types of radar installations on Alum mum n .akIlta Top Typ I aircraft, be used with a reflector and single ill 1Se . where TyY CPt NP. ALL BRASS -STAIN. available space is limited. radiating dipole. Some radio amateurs SPRING A PIN. PRO'EN by 2aí1 HR. AI .T SPRAY TEST e. NON. Use of three directors with a dipole have used as many as 8 or 10 directors CORRnTVR t 2110 ear, tsnutaavr.r. and Doe'.,. Lbnt and reflector further improves the di- in a horizontal array. The practical DIaccunt. rectional effects of the horizontal array limit is about 4 or 5 directors, all of the X. L. RADIO LABORATORIES and provides a radiation beam approxi- same dimensions. 420 Wart Chicago Ave., Chicago 10. III.

RADIO -CRAFT for APRIL, 1947 69 Missing MULTI -STATION INTERCOMS (Continued from page 33) Values The Talk -Listen switch is just be- switch plate may be cemented to the In Radio? neath this, on the chassis apron. The wood, over the selector switch shaft, cabinets come with speaker grill all cut with Duco or similar cement. FOR THIS NEW and covered, so mounting these two While the veneer on the cabinets is switches just halfway between the right not bad wood, putting on a coat of clear S edge of the speaker opening and the shellac is a good idea. It helps protect right edge of the cabinet will give a the wood and gives a polished look. balanced appearance. The rear of the cabinets can be left If the time necessary is justified, the open, but better voice quality, volume FREE and appearance will result new Millen panel- marking transfers from closing TALOG 1101111 may be used to mark the On -Off switch them. White Bristol board or any fairly heavy cardboard is CA satisfactory. Do not SF+R measure the board Here's the handiest, most complete and cut it; the cab- radio buying guide in America. Contains inets are not abso- over 10,000 items of nationally known 4n LISTEN lutely square. Lay quality. Brings to your door step the z the back of the cab- world's largest and most complete stocks inet on a sheet of of radio and electronic equipment. Save RECTIFIER i the backing and time, work and money-send for ¡our TALK trace the outline. free copy. OFF co Then cut with a ra-

STATION SELECTOR X I zor blade and trim ó to fit. A miniature 1 20 wood screw in each g 3o corner will hold the so: 0- back in place. Be X CONNECTS ó TO LINE CORRESPONDING =.OS F IL. 7 So careful to make the TO STATION NUMBER = Y ILAC /DC guide hole for these

Fig. 4-A simple system which uses I tube at each end of the circuit. screws in the cen- ter of the ply to avoid splitting it. A hole may be cut in the backing to accommodate t h e PARTS. America's biggest stock line cord and the of quality parts and equipment. interconnecting ca- Everything for hams, sound - ble. However, it is men, engineers, servicemen, ex- and as perimenters. All leading makes easier just at economy prices. satisfactory s i m - ply to cut away RADIO SETS. The new Lafay- about 2 inches of ene Catalog is a regular pa- rade of all the latest 1947 the bottom all the models, including phono- way across, thus radios, portables, communica- avoiding having the tion receivers. Latest styling - outstanding performance - backing torn by the wonderful values. cables. It will be noted P.A. Sound systems for every type of public address instal- that a multiconnec- lation. Complete listing of am- An under -chassis view of 3 -tube master unit of Fig. I (March issue) tor plug and socket plifiers, microphones, speakers, are used to plug accessories. Many new develop- If not, the line system into the master units, ments listed for the first time. and the station selector numbers. a standard Off, 1 -to -5 position circular while the remotes are simply connected Send and Receive Code RADIO WIRE TELEVISION. INC. ICD Sixth Ave. N. Y.13 wctk ekL:t 2 WAY PROFESSIONAL 110 Federal Dt. Bo.,ton 10 07 TELEGRAPH 24 Central Ave. Newark 2,ftJ. PRACTICE SETis' Paste Coupon on Penny Post Card Son,, and by U. S S,gnol Corp(. --1 Learn code quickly and hone bad, of Substitution" r. sun with your' 'private intercom system. Ssrvieing by Signal LAFAYETTE RADIO, Dept. JD -7 Learn about this modem dynamic approach Price YOUR Ave., New York 13, N. Y. to radio with ONLY BASIC TEST 100 Sixth $9.95 COSTad,$59 servicing Co.NN -.,k .Mh.ne EQUIPMENT. Please send new Lafayette Radio Catalog Includes 2 Lionel lep, 2 Speeder HE ... fully described in o 120 page book ":2 code battery, wire, etc. at once. busters. plates, available horn your Precision Distributor or and nstruct.on sheet. Send check or MO. factory at 35e. ...Schools are invited to inquire regarding Nome,....- ...... » l, WAAAEN ST, quantity orders from our Educational Division. AUDIO S A L E S CO. 7, I NEW YOAK Address I P R E C I S I O N I Temperature rise of water through which v.h.f. APPARATUS COMPANY INC. waves are passed is used to measure their power ELMHURST 4, N. Y. Zs..._..State..,...... ea ...... I in a microwave wattmeter invented at Brooklyn Manufacturer, of fine Te.t Equ.pment 5DIO TELEVISION ELECTRICAL LABORATORY .-1h.»...._....w ...... ,.e J Polytechnic Institute. 70 RADIO -CRAFT for APRIL, 1947 TO OTHER STAT11 00 r

INPUT SPKR AMPLIFIER LISTEN 1 2i,stioztion 1 Maiced OUTPUT o- o''r WITH ABSOLUTE FIDELITY TALK

OFF AMPLIFICATION DESIGNED By A. C. SNANE7 STATION SELECTOR o

2_ i STATION N °I ó A new and spectacular development 30 o3 v're a Identify all the instruments in a ('R'or<6'ct- 4 k-,/y 04 05 50 L J . suit of nearly 20 years of specialized audio nn, i ment, we con now place in your hands o new means to male the moi

INPUT ioaclnating, uplifting, and enjoyable journey info the realm of pert - AMPLIFIER sound reproduction - through the medium of the most sotisfyint music - OUTPUT amplifier the world hos ever known.

If you are one of those discriminating persons for whom anything less'; TALK 1 than the best is a disappointment, you are one for whom the ACA -100DC OFF - Amolifior was designed. Send for literature. STATION SELECTOR _I o 2 I( 2 o STATION Na 2 3 3 1 AMPLIFIER CORP. of AMERICA

I 4 4 1 D 398 Broadway, New York 13, N. Y. 5 5 L_ 0 0 A. C. Shaney's FM -AM AMPLIFIER MANUAL is still available at 25c Fig. 5- Wiring diagram, I -tube master system to two leads on a convenient terminal strip. Connections to these remotes may be so made that a solid cardboard or Masonite back can be fitted perma- "So may the outward shows be least themselves nently. The world is still deceived with ornament[" The next article of this aeries, to appear in an early issue, will show in detail the junction William Shakespeare boxes and connections and will deal with the actual problems of installation and servicing. VERIFIED SPEAKERS DIP1roRTNNITey AD-LETS Advertisements nn this section cost 20 cents a word Do not come in fancy cartons for each insertion. Name, address and initials must be Included at the above rate. Cash should acrwm- pany all elanlaed advertisements unless placed by an accredited advertising agency. No advertisement for leer than ten words accepted. Ten percent count alit Woes, twenty percent for twelve issuer. Everything goes into their objectionable or misleading advertisements not C vented. Advertisements for May. 1947. issue must v. h us not later than March 25. 1917. Efficient and Sturdy construction Radio -Craft 25 W. B'way New York 7. N. Y.

"TELEVISION RECEIVER COIL. KITS INlLUDINO complete set of 10 matched coil. for a or 7' Television That's why RADIO SERVICEMEN like them Receiver. instructions wrapped around each roll Include typical circuit application. Kits are shipped prepaid, $4.95 each. Vision Research Laboratories. P.O. Box 52, Kew Gardens 15, New York." TELEVISION RECEIVER EASILY (ON'TRI {TED from our plane. Vision Research Labe announces new lino of television booklets written especially for the ham WRIGHT experimenter. Booklets now available (8200 each): "Design and Construction of 7' Television Receiver" and "Visual Alignment Sweep Generator." Booklets con- tain theory. practical details, illustrations, schematic di- INC. agrams. etc. Vision Research Laboratories. P.O. Box 52, Kew Gardens 15, New York. SPECIAL OFFER BRAND NEW SURPLUS 2232 UNIVERSITY AVENUE ST. PAUL 4, MINN. General Electric 3 -Inch Meters, I Milliampere Move- ment. Antiglare Olas,. 83.25. Box 4P. REPAIRMEN. HAMS! GET NEEDED RADIO -ELEC- lronlca books by mail. Send stamp for illustrated catalog. D. B. Nephews Publishing Company, Dept. C4, 300 Pa- ciac Street, Brooklyn 2. N. Y. BUILD RADIO PHONOORAPII. COMBINATION, COM- Wets kits: catalog. Radion, 69220. 21st Ave., Brooklyn CORIIESPONDEICE COURSES ANI) SELFINSTRUC- tion books slightly used Sold. Rented. Exchanged. All AMAZING NEW subjects. Satisfaction guaranteed. Cash paid for used Pocket or A GREAT MONEY SAVER. COMPLETE WITH TUBES. RADIO ! courses. Complete information and 100.page illustrated si 0.95. Details Radio. 9418 Ave A., Brooklyn, New York. Puree size bargain catalog Free! Write- Nelson Co., Dept. 29, Chi- sMA1.1. AS A TACK OF C.IC- weighs only few cago 5. Ill. MAGNETIC WIRE RECORDER KIT. 8200 value, $19. P. -Beaus n! black chrome WE REPAIR ALL TYPES OF ELE(TRIC.tt INSTRt'- O. Box 363, Hoboken, N. J. pinngec rase. Uee new r tom meeta, tube checkers and analyzers. Marlton Instrument crystal diode. 11141.t1de dial. NO Meter Laboratoty ), 140 RADIO MEN -LOWEST PRICES IN AMERICA. BIO tubes, batteries or electric "Plca- Io. (Electric Liberty Street. New Stock Write for Ye -k. N. Y. Telephone- RArclay 7 -4239. latest Catalogue. McGee Radio. 1330 Ins." Usually es local IRcstdway, Denver, Colorado. broadcasts withoutoutside aerial MAGAZINES (BACK DATED) -FOREIGN. DOSfESTIC wires. arts. hooks, booklets, subscriptions. pin -ups, etc. Cates GUARANTEED TO PLAY lug 10c (refunded). Cicerone's. 863 First Ave.. New when used according to inetruc York 17. N. Y. SUPER -HET KIT, $9.75!! Lion sent with each dio! You Plastic Cabinet-uses SOLS. 3525. It at home, omees,in AMATEUR RADIO LICENSES. COMPLETE CODE 12557. 125A7 huseotels, cabins, In bed, etc. -Iota and theory preparation for passing amateur radio ex- of fun aminations. Kit of 4 ra:tched tubes for above kit $3.55 -real entertainment! Home study and resident courses. American Wireless Phono Oscillator kit (..h, money order, check) and pay Radio Institute, 101 West 69rd Street. New York City. 2.95 send only '100 Above kit, wired & tested 3.95 mival See Mr ad on page S0. Kit of matched tubes for wireless or send .90 for postpaid delivery. Com 2.35 p rte as shown Ready to Play with self contained per- FREE WHOLESALE. BULLETIN. TUBES PARTS. 3 -Tube phono amplifier kit 2.75 nal phone. For Glfta-chlldren will love it-grown. Bargain price.. Renshaw Radio Supply, 3313 Delaran Above kit, wired & tested 3.75 lo..; too, An a ceptl onal value-order yours and enjoy City, Kansas City. Kansas. Kit of matched tubes for phono 3.15 y good radio programs coming! Don't be with All kits are complete instructions. out your Pa.Kette Radio another day! (All foreign or. USED CORRESPONDENCE COURSES AND F.DUCA- with 55.00 U.S. cash.i Oonal Bouta Bought. Sold. Rented, Catalog Free, Edu- RADIONIC DESIGN Pa.Kette Electric Co. Dept. RC -4 Kearney, Nebraska cational Exchange, Hmagac, Ala. 700 g. 5th Street New York 9. N. Y.

RADIO -CRAFT for APRIL, 1947 71 Chemical Laboratory New Radio -Electronic Patents Dial Cable Kit By I. QUEEN

Dial Belt Kit - Alignment Kit WIDEBAND COUPLING GC NO. 5025 Ahmet H. Nevzi, Philadelphia, Pa. PROFESSIONAL Patent No. 2,405,515 much higher efficiency. The small coupling con- ALIGNMENT KIT It is difficult to design a good video amplifier because of stray coupling and loss in the coupling denser is placed within the larger paper wound Complete alignment and neu- between stages. To flatten out the frequency condenser. The two ends of the unit are carbon tralizing kit to eteel box. Has discs which are actually the two resistors used every tool to service any set; response it is necessary to reduce stray capaci- 30 tools. List $19.95 tance between components, leads and ground. at either end of the network. Not only does this method simplify the assembly of the unit but it G -C ELECTRONIC reduces the capacitance to ground of the several CHEMICAL components and their leads. The result is a higher gain over a wider band of frequencies. LABORATORY Ideal for all se Ienmm 19 linntues and chemicalsr in TM. (free) steel rack. e No. 998 List $11.12

GC SERVICEMEN'S EXPLODED VIEW DIAL CABLE KIT NO. I Contains four 25 ft. spools of pot tar dial cable with tree .003, bltcSDOK,dt25 assortment of eyelets and clamps. No. 77SK List $4.76 A typical coupling network is shown within the G -C SERVICEMEN'S box in the first figure. It is composed of an DIAL BELT KIT R -C network in which the stray and distributed capacitance to ground must be kept low to Fine woven re- plarement, for all avoid resonance effects and power loss. Typical sets. Easy to install. component values are shown. Supplied with steel new box in kiln M vari- The figures show how the design per- ous quantities. mits the construction of components having COMPLETE UNIT

Na G25 -kit of 25 belts List $6.70 Available at leading Jobbers. Write for catalog. NEUTRON DETECTOR SEE OUR EXHIBIT -BOOTH = 96 William E. Pa. 1947 RADIO PARTS CONFERENCE Shoupp, Pittsburgh. (Assignor to Westinghouse Elec. Corp.) Stevens Hotel, Chicago May 13 -Ifi Patent No. 2,408,230 RADIO DIVISION DEPT. D The Geiger- Muller counter is widely used ns a existing equipment. The inner glass surface Co., Rockford, U.S .A. of ionized particles. Only very recently, a Geiger -Muller tube is coated an atomic GENERAL CEMENT Mfg. detector of with of over 3,000 products however, the uncharged particles of an atom, fission material, such ae uranium or thorium. Manufacturers pass in prinnpol cif." the neutrons. have become important in atomic Since neutrons readily through the glass note, offfs. .. physics. They have an essential role in the pro- envelope, they will break up atoms upon bom- duction of atomic energy by nuclear disintegra- barding the inner coating, thus making available tion. ionized particles. As in conventional devices, This invention permits the detection of un- these particles are readily detected. It is neces- charged particles through a modification of sary, however, to use a comparatively low volt- age across the Geiger-Muller RADIO PARTS IGER-MÜLLER TUBE tube to prevent it from record- ing unrelated particles or radi- SYSTEMS ation such as gamma rays or SOUND X -rays which may be present. ELECTRONIC FISSION Each ionized particle within MATERIAL the counter chamber causes a APPARATUS pulse of current through it with a resultant voltage drop across the grid resistor of the first tube. on Resistor R is designed to pro- Depend IIF+-_IgHI duce a sufficiently large drop RADOLEK no that the voltage across the WAR SURPLUS Radolek's big Free Profit Guide Catalog and Profit `C4/6 SPECIAL $25.00 OFFER Bulletin supplements keep ee;;04 abreast of the RADIO PARTS On receipt of $25.00 we will ship you freight you collect a large assortment of choice govern- rapidly changing radio ment surplus radio items, subject to your situation. Buying from inspection and approval. After inspecting them, if you are not completely satisfied, re- P.adolek means greater turn the shipment to us freight collect and $25.00. But we know SERVICE KIT values, better service SOUND SYSTEMS we will refund your assortment of: after you see our choice assortment you will, Kit includes 1 (screws. and more profits. Make want keep it, therefore, we can af- Joe Resistors, a/a and Ib. Hardware surely to nuts, lugs, etc.) be I watt. Radolek your buying FREE ford to make this offer. You should able Connectors & Plugs of the items that you do not 50 Condensas. paper. 25 to sell enough mita and can. 10 Jacks (Phone) headquarters. CATALOG need the entire lot. 12 Condensers. to pay for 10 Switches. toggle and Pacifier 12 Terminal Boards with Our warehouses are filled with thousands gang. Resistors. of choice surplus radio items. 100 ft. Spaghetti. va- government rious sires. 25 Ceramic Insulators. Large Stocks Many of them we do not have in sufficient I Screw Driver. 12 Knobs, round and we I Puller. quantity to advertise nationally. And if bar. Tube them, their cost 2 Allen Wrenches. Fast Service inventoried and cataloged 2 lbs. Hookup wire. Holders. would be increased. In this way you 2 Penal Fuse greatly 20 Fuses. 4 Binding Post Strips. can purchase desirable war surplus radio ma- 6 Volume Controls. and many other val. terial at the lowest possible price. 10 Tube Sockets. uable items. Therefore we make you what we consider a Your Cost Complete RADOLEK CO.. Dent. C -Ilt highly advantageous offer. If you mention a $9.95 LOI W. Randolph St.. Chicago 6. III. few items you prefer, we will try to include Please send your FREE Profit Guide Catalog. them in the shipment. State whether you want Free -Experimenter'. ham assortment. Kit with First 500 orders. Name our commercial or Write for our catalog. Address....___ THE ABELL DISTRIBUTING CO. AMERICAN SALES CO. Maryland 111. SAVE AT RADOLEK S E. Biddle Street, Baltimore 2, Mil W. 47th St. Chicago 9. 1947 72 RADIO -CRAFT for APRIL, Geiger -Muller tube becomes too low to sustain the ionization. Therefore each pulse is detected separately. The greatly amplified pulses in the SCARCE TUBES second tube plate circuit energize an electro- magnet and operates the plunger which is coupled At Good Discounts to a mechanical recorder. All Popular Standard Brands New l:uaranteed Scaled Cartons a Advertised 0Z4, ILA6. ILN5, IP5. 2A3. 5Z4, 6A8, 2A5. 2A6, Save on Nationally 6E5, 6F5, 618. 6K5. 6KB. 6F5. 6Q7. 7A8, 788, 785. SUPERADIO 7B7. 7C5, 7F8, 7G7, 12A8, 12F5. 1217, 12147. 12Z3. LIGHT 14Q7. 1487, 25A7 25L6. 25Y5. 2525, 2526. 30, 32L7. (Continued from page 17) LASH Two -Cell 33, 35, 35A5, 35%4, 3523. 43. 45, 47, 50A5, 50Y6. R 1.19 55. 57. 58, 59, 70L7, 71A, 84, 1170. I17M7. I17/47, g I17P7, 11723, 11726, XXL and many others. Flashlight Uteility t side radio may well be changed completely. type. Convenien THIS MONTH'S SPECIALS! It is even possible Army with bulb. Fivetube All-American Kit that the radio phe- clip. Complete 50L6, 3525, 125Á7, 12SK7, 12511" $3.65 nomenon of superconductivity may be Strong beam. 2.Y5 es.mt replacement for 25Z5. List urine linked with 63.20 Your cost 75e another imperfectly under- Rescó s Price Acorn Tubes guaranteed 954, 955, 956, 937..49, each stood old radio phenomenon: OAKS tubes guaranteed 75e each -Cell Hearing .1h1 tubes. All Wes. 1.30 Two 501A_C, 509AX 49c each Ever since radio broadcast started in Reg 6A116 Tubes 49e each the early twenties, newspapers from all Industrial Flashlight Condenser. Brand New. Individually Boxed. Fully over the world ribbed cose. Guaranteed for one year. Used by leading radio man- reported most unusual Durable beam. Com- ufacturers ut a Klee you can't beat Throws strong 20/20 and unorthodox radio reception. In Bos- bulb. MFD at 190V 45e ecazrh plete with 8 MF» at 4501 3'c each ton, for example, a cold -water 18 31FD faucet at 450V 45e each s Price 20 MFD at 150V 32c each a block away from a radio broadcast Rescó above SPECIAL DISCOUNT ON ALL LARGE ORDERS transmitter gave out music or speech Batteries for 61 /no WRITE OR WIRE each FOR CATALOG when turned on. A few blocks away a WE SHIP ANYWHERE -Size housewife almost fainted when a frying Reg. 45c Pocket pan on a gas stove emitted music and Flashlight "Bantam Fits lectures that could be heard throughout alum i nu m case. 3 -inch Civet plenty the flat. Similar pocket. and strange radio sounds into With battery COMMERCIAL RADIO have been reported in the press for et light. years. bulb. Price 36 BRATTLE ST., BOSTON 8, MASS. The radio engineer shrugs Rescó s 3 9c. p,.,,... N this off as "an imperfect contact effect ". But it is not too easy to understand just why a RESCO'S FAMOUS faucet or a frying pan should become a 10,000 -PLA Y sonorous loudspeaker without any radio Phonograph NEEDLE PEN -OSCIL apparatus and electric current -even if With sapphire -LITE jewel tip. Extremely convenient test oscillator fnr all radin near a broadcast station. 85 alRaange Small as Self Reg. $5 . , . Resco's Price Po,.,eredg "from 700 les audio to over Many years ago, on 1 000 colt a trip from New Resco owe cost Used by Signal "Corps Write for York to Bermuda I was on deck of has all informati n. ' PERMEABILITYtypes or TEST EQUIPMENT a steamer in a somewhat foggy night. 38 Argyle Ave. Buffalo 9, N. Y. Suddenly the overhead two -wire antenna TUNERS became very audible! The operator was color All dial scale; transmitting with an old de Forest units prefracke o huff, brown Tunel from Id't spark transmitter. I was far away from Individuallydle 340 Factory pocked,l6 the wireless shack, consequently I could ready fo Electron ics Made Easy I not hear the lire transmitter itself. But the NO, A -230 antenna gave out peculiar, weird, crack- Superhetrodyne ling sounds and ''.J! I could follow the code with #11?- easily. This phenomenon has been veri- Completeoscil laf MOICh- Smooth °' coil . J. 1fie fied by others. It doesn't occur drive. at all hook In- times, but only when grams -up f/ conditions are diag right. end instruction d'o- ' sheeramt. P Others have heard speech and music Priceeo'x Magl -Klips KIT issue from overhead radio antennas of Build 18 Experiments at Home broadcast stations at certain times. NO. A -210 - Superhetrodyne No Tools! All this proves that there can be radio RADIO RECEIVER, HOME BROADCASTER, Slide PHOTOELECTRIC reception without 'orthodox radio re- Rule Type RELAY. CODE PRACTICE scale. OSCILLATOR. SIGNAL TRACER. REMOTE ceiving instruments, such as radio tubes, drive,5 Smooth CONTROL RELAY. Phonograph Transmitter. In- includes ex_ tercommunication Amplifier. Code Transmitter. conventional tuning devices, and elec- traded Radio Frequency Oscillator. Telephone Line Am win- pllOer. tric current. dow and Electronic Switch. Phonograph Amplifier, hook-u;p Temperature Control Relay. Contact Detector. Electrmie Metronome. Interval Timer (one- shot), Evidently there is more to radio re- Reno's Interval Timer (repeating). ception than meets the eye. To quote Price 405 With a Magi -Kilos kit yot encer the entire field No. of eleetronlr en:Am-owing Iheory quickly In y ut spare Shakespeare: A -260 t lme. It's slmp'e to arrange the romnnnenl s(orn each No 1: np- Regenerative ci real. soldering - No tedious wiring. it "There are more things in heaven and erles on 110 v Ar or DC and inelodes 3555 recli- earth, ner, 50T.6 power a ' Ilfier. 12S' 7 double triode. poN- Horatio, Tuner erful 4' speaker -mike. plate relay. broadcast and SW Than are dreamt Replaces single rolls. tuning condenser and generous supply of re- of in your philosophy." variable g Islnrs, ron,'ensera, chokes. extra wire. Parts worth Complete conden stir.n double the price of kit. Mth coil. lilt's 49 -page manual has emmnlete Instructions and diagrams easily followed by the heglnner. Re- Price member, you need AMPLIFIER Price no tools. except possible a screw- 1447 driver, with a Mail -Kilns elertronle ex- $39.95 perimenter's kit For Call System or Write complete for BM, Value- Packed Bulletin. Phono. Amplifier Include Postage with Cash Orders DEER & TAYLOR COMPANY 1340 Mi!via St. Merkeley 9. Calif. $2e95 Please ship MagiKlipe electronic kit (s). 1 enclose B.. Complete with tubes C Please mall Illustrated folder on the Magi-Klies kit Compact -wired Name Ready to Operate Uses 35Z5-50L6. Street N. J. INDUSTRIAL CO. 7TH AND ARCH ,STREETS. PHILA. 6, PENNA City vial, 309 ELM ST. NEWARK 5. N. 1. branche, of 5133 Market Si. and 3145 N. Brood St., Phila. Also In W8mingtots, Deo Easton, Pa., Allentown, Po, RADIO -CRAFT for APRIL, 1947 73 A SMALL RECORDING STUDIO AMATEURS and METERS (Continued from page 3.4) RADIO REPAIRMEN ticularly efficient way to ruin sapphire AT BARGAIN PRICES needles, as they are likely to shatter 10 lbs. of Useful Radio Parts their points by digging into the base Look at this list! material. Only $1.79 A. C. VOLTMETER Triplett Model 331 J.P., 31/2". The shavings are a particularly an- round flush bakellte case. white scale. 0 -150 volts. INCLUDES: Complete with external wire wound precision resistor noying part of recording. In a profes- to surreale range to 300 Volts. sional set -up they should be picked up * 1 Back Geared Motor A. C. AMMETER Triplett Model 331 7.1'. (same as above/ 030 Amps A.C. with a suction pump and directed to operate on 24 volts D.C. SPECIAL through a piece of hose to a metal con- or 110 volts A.C. OFFER ONLY $8.95 BOTH METERS tainer filled with water. These highly Resistors Chokes Condensers D. C. MILLIAMMETER Dour Ammo Model 310. inflammable shavings are a fire hazard. Contact Points Sub Assemblies 354 ", found flush behehte case. 0 -1. M.A. movement with 0 -4 Klloolt. white scalp. Complete with paper They may be brushed toward the center Tuners, etc., etc. toit ohm millbunmeU4 scaly und wiring diagram showing how to make an maUzer. of the turntable with a loosely held SPECIAL 93.95 so-called "chip In lots of 10 at $3.50 each handkerchief, or with a 'GEORGE BROOKS & AVOCIATES- MTCROADfMETER General Electric. Model D0.41. chaser," a brush so placed on the table 220 SOUTH HALSTED STREET CHICAGO 6. ILLINOIS 354", round flush bekelte case. 1511-e -130 microampere, the 75 ohuu resistance, zero center movement. (Hank Sale as to direct the shavings toward marked "Balance -Sol. Power" center. For recording for professional EACH 94.50 with SIICROAMMETER O.E., DO -41. 354 ". 0 -500 micro- users, the discs may be recorded from Make any record player wireless ampere. Sale 0.20 K.V. with paper V .M.A icy inside out so that the needle is moving these brand new MILLIAMMETERS away from the shavings. O.E., DO.41. 31/2". round flush bakellte case. 04 TWO -TUBE PHONO M.A. movement. Knife edged pointer. Spec. Black Cutting Speed and Record Size scale with paper V.O.M.A. scale EACH $4.00 G.E. DU -41. 354 ", round flush bakellte case. 0 -1 The recording- frequency characteris- M.A., Standard white scale EACH $4.99 OSCILLATORS O.lt.. DO -53, (354" Square flush Bakelite easel 0 -20 tic will depend somewhat upon the speed M.A EACH $3.25 O.L. DO -41, 354". round flush bakelite case. 0-50 at which the recording is being made. ..s.A. Black Scale EACH $3.25 r.p.m., the disc can be cut in to a G DU 41. 3W, round flush bekellte case. At 78 M. -200 4-inch diameter, and the high -frequency U.C. KILOVOLTMETER 1)0-41. 354 ". round flush bakellte case. 0 -2.5 KV., Black scale. with ex- response will be good. At 33 1/3 r.p.m., ternal precision. wire wound resletor EACH $6.95 to re- A.C. VOLTMETER G.E. AO-22. 31/2 round flush it is considered good practice not bakellte case. 0 -150 lolls A.0 EACH $5.50 below an 8-inch diameter. With A.C. A5151.-TER G.K. AO-22, 31/2.. round flush bake- cord tie case. 0 -80 Amperes EACH 54.50 any lower speed of the record past the RUNNING TIME METER O.E.. 3Yi" rotted flush bakellte cue. Up to 9.999.9 hrs. Operates on cutting head, the high- frequency excur- 10.12 volt. 60 cycle. Ideal for counting the total Operates as far as 100 feet from a radio and an be hours of operation of the power tubes on trans- sions would be crowded together closer used with Automatic Record Changers, Players or mitters. etc. EACH $3.50 Microphone. Uses 2 tubes. than the radius on the tip of the cutting Complete with tubes NET $5.95 MILLIAMMETER needle, which is in the order of .002 Supplied In kit form with "easy -to- follow" instruc- WESTINGHOUSE. 354 ". 10A -35. Square Bakelite The playback pickup would not tions for assembly. Complete with all parts. instruc- 0 -1 inch. tions and tubes. ease. white scale, tong narrow Spade pointer. NET $4.95 M.A. movement, 55 ohms resletance with standard follow these extremely crowded excur- 0 -1 M.A. scale as illustrated. Complete wills paper This meter was made sions. The closer you get to the center Volt -Ohm Mllilammeter scale. D. Cr D. RADIO for the Gov't to be used in various types of ladle of the record, the closer together the transmitters and receivers. EACH $4.95 163 Owns SL. Dept. C. New Yerk IS. N. Y. M 10,000 -cycle variations will be. When old Bakelite Becase. Ó200 M.Á .EACH`3runflusl $95 D.C. VOLT\IETEit Westinghouse. NX -35. 31/2". round they are closer than .002 inch, the flush bakellte case. 0 -50 Volts. 200 ohms per follow them. It BE YOUR OWN BOSS! volt EACH $3.95 needle obviously cannot D.C. VOLTMETER Westinghouse. NX -35 354, round is desirable, therefore, to increase the flush bakellte ease. 200 Volts, 1000 ohms per MAKE MORE MONEY volt EACH $3.95 high -frequency amplitude by equaliza- In "CASH IN you NE-35. 354 S1.00 D.C. KILOVOLTMETER Westinghouse. tion, when nearing the center of the disc vALUE now get THE real round flush bakellte ease. 0 -1.5 K.V. Complete money -makers - dms with external wire wound precision resistor and at 33 1/3 r.p.m., to counteract the fall- ems of profitable tested mounting el ine. EACH $6.95 mail order plans- con- D.C. KILOVOIJrSIETER Westinghouse. NX -35. 354. ing high -frequency response of the fidential business se- round flush bakellte case. 2.0 K.V. with two 25C creta. dozens of pram external wire wound precision 1 Kilovolt resistors, disc. On some machines this is done con- tira) tested formulas. to make tine dual range 0 -1 & 0 -2 Kilovoltmeter. by a mechanical arrangement. 40.000 successful tested Complete with mounting clips EACH $7.25 tit.uously schemes - actual ex- A.C. VOLTMETER Westinghouse. Type NA -35. 354. be done, however, by advancing WORDS perlenem of loen who round flush bakellte case. 0 -15 Volt A.C. It can tuve staved on a shoe- EACH $3.95 the high -frequency boost control in IN string -with lees than A.C. VOLTMETER Westinghouse, NA -35. 354. round TEXT 510 espial. 25e a flush bakellte case. 0 -150 Volt A.C. EACH 55.50 small smooth steps to produce a record- copy A.C. AMMETER Weetinghouee. NA -35, 3%'. round U.. S. stamps, money flush bakellte rase. 0.75 Amp. A.C. EACH $4.50 ing in which the high -frequency re- NO ADS arder, or coin. DECIBEL METER Weston Model 301. 354. round ALL flush bakellte case. General purpose type. Black sponse seems constant. Money Back dial. white markings. Seale marked "-20 to 0 When you have cut a disc, see that it "MEAT "! Guarantee DB" Zero DB equals 1.73 volts. 0 Mldliwatts. Calibrated for 500 ohm load. Lower Seale marked is protected from dust, which will cause NATIONAL PLANS COMPANY attenuator -15 to +5 DB. which can be used if an York 23, N. Y. or resistor network is ',melded EACH $4.50 a great increase in surface noise in a Bea ZSRA. Assents Stalin New SIGNAL STRENGTH C'S") METER Simpson Model very short time. It is wise to instruct 25. SW'. round flush bakellte case. The thin on the plate circuit of your receiver to show the relative your customers to so protect their re- strength of Incoming signals. Seale alibrated- RADIO SERVICEMEN! 1 cordings. 9 to 100 DB above microvolt. 5 M.A. Zero right EXPERIMENTERS - INDUSTRIALS movement with translucent scale, l'or internal male Attractive labels can be printed or Illustrated Illumhatlon from rear Of meter. Complete with Send trains for our ' Illustrated socket, lamp A circuit diagram. For further details made photographically to provide free 1947 CATALOG of RADIO and F3.F.C. Catalog refer 10 I,1 I -105 & Fig. 730 II of Radio TRONIC PARTY rd SUPPLIES. Just c:w.,.' oir the Write today! FREEt Amateur IL,, C EACH $4.50 advertising and to remind your custom- press! ers where to come when they require NATION -WIDE RADIO SURPLUS -NEW additional recordings. i Copt. e, 572 W. Randolph St.. Chicago a. III. GUARANTEED Other equipment, such as a cathode - ray oscilloscope for distortion observa- Amateurs of the Midwest meet for Gov't Inspected tion, audio oscillators, vacuum -tube volt-. a two -day hamfest May 24 and 25, at All orders F.O.e.. N. Y. 25% Deposit required on Hawkeye Downs, home of the Iowa C. 0.0,',, Be sure to include sufficient postage, encase meters, portable recorders, sound trucks, .01 be refunded. etc., would be desirable in a completely State Fair. equipped recording studio, but that out- The program calls for technical pa- MARITIME SWITCHBOARD lined here is adequate for a good job of pers, banquet at Cedar Rapids, with 336 Canal Street commercial recording, and constitutes ARRL President George Bailey as speaker, entertainment and special NEW YORK 13, N. Y. the basic set -up to which cell be added all the many refinements. events.

74 RADIO -CRAFT for APRIL, 1947 BC-625 ON 144 MC (Continued from page 36) RADIOMEN! Here's the Way to Bigger Pay was threaded for a preset locking de- ed. A loop absorption wave meter is vice. The original ratchet tuning ar- still a most useful and handy gadget rangement need not be removed at all, to have around just to make sure. A Complete Practical Set of but merely disengaged from the tuning Using a power supply which delivers condensers. 300 volts and around 260 ma, repre- In the original transmitter, a pair of sentative currents as read on the test pins was provided for plugging in a meter will be: 0 -1 -ma test meter for tuning. Each cir- Full Scale Actual Normal Heeeesonto Curant Study and cuit was then selected by a 6- position Pes'tion Reading (MAI (MA) RADIQHome meter test switch. The test meter was No. 1 0.4 50 40 Books PRICE external and used only when the set No. 2 0.5 100 50 Reference was in for repairs or a retuning job. As No. 3 0.6 to 0.7 100 , 100 modified, this meter is made permanent No. 4 Not Used on the panel and the leads permanently No. 5 0.6 to 1.0 2 2 soldered to meter Yours FREE the receptacle pins. No. 6 Not Used 4 WD This meter FRSA pUI test switch also gets a 1/a To Try 7 Days inch extension shaft This will represent a power input to through a brass NOW -- new 1947 set coupling, so that it projects through the the final of 20 watts and it is safe to of practical, "down to front panel. assume of this amount, 12 earth" books for the that watts man who wants to get is being delivered to the antenna. ahead in RADIO and The meter switch positions BRAND realizes he must know modern radio and tele- The six positions of the meter test Power and bias supplies NEW vision to handle a big- switch correspond following A word regarding the 1941 Edition ger job. 'Applied Prac- to the cir- filament and tical Radio" gives the cuits: bias requirements: The filament energy JUST OFF radio worker the informa- Position No. I: is most easily obtained by connecting pRESS tion he needs to advance in his lit frequency -multiplier plate circuit. job or radio business. Yet. this Position No. 2: two small 6.3 -volt filament transform- great set is written simple enough 2nd frequency- multiplier plate circuit. ers in series to provide the 12 volts re- for th, h, ginner. This is the only set of its kind Position No. 8: in Amr ricu today.' Power Amplifier plate circuit. quired by the set in its original condi- Position No. 4: tion. No changes are required in the fila- APPLIED PRACTICAL RADIO Not used (some earlier models used this ment wiring. Since the Tells All in 3 Handy Volumes position as antenna indicator; it was dis- total drain is continued on later seta). only around 1% amperes, small trans- Here is practical, working knowledge of RADIO Position No. 5: as it is used TODAY -from Power Amplifier grid circuit. formers are quite capable of handling basic -principles to latest Position No. 6: the work. advances in Television. The Not used. facts are boiled down. in- The plate supply can be any pack de- cluding the "know tow" to FREE! Incidentally, panel lettering was done livering 300 volts at 260 ma and the construct. install and serv- 1 year of Con- with the new Millen decalcomania ice all types of Radio and panel bias requirements is- -150V. This nega- Television apparatus. sultation Service marking kit (No. 59001). This probably tive bias voltage may be obtained by Unique picture instruction & Tech Bulletins is the best bet for panel marking yet de- method takes equipment tapping below ground on the B- supply apart to show what makes included vised for the average amateur without or by using B- batteries. While it is en- it work and how to keep it other facilities. Nice work results if a tirely feasible to reconstruct the cir- going. little care is used in applying the letters. cuit to provide for this necessary bias Everything New in Rodio The antenna coupling is variable with by various RI drops through additional Made Easy circuit resistors, it The hundreds of interesting up- to-thc- minute sub- is strongly recom- jects covered include Fre- quency Modulation, Tele- mended that the vision. Auto Radio, Public 10 to 1 GUARANTEE original specifica- Address Systems. Multi- Set must earn 10 Band Receivers. High Fre- times tions be adhered to quency and Short Wave - its cost or -that is, provid- everything in radio today Coyne sends money from A to Z. Over 1000 bock o its return ing this amount of pages with 600 illustra- at end n of 1 year external bias by tions and new diagrams. t h e method de- Send Money scribed. No -See Books Free nut ont take our word for what Ih,m -.d hooks tin a for Olt-- 8e them )'ourself. Just till In coupon be- Efficient h a r - low and mail It fanny. Coyne monic multiplica- sends you "APPLIED PRAC- TICAL RADIO" to look over Backed by tion 7 days FREE. feel act depends a It you Coyne School's Bottom view -First 832 and its hairpin tank line are well shown here. Isn't everything we nay AND great deal on YORE. just return it et n 20 years of the proper expense and you owe nothing. bias If you keep the Set you need Radio shop a setscrew. This is adjusted through the and drive, and most problems in get- pay only $3 after 7 days and $3 per mash (see mupail. You experience oblong hole which is shown on the right - ting on the 144 -mc band and higher can't lose on this offer, so don't hand end of the panel. A screw driver stem from insufficient and incorrect delay -send that coupon NOW. adjusts this feature. The final tube is drive and /or bias. This set is engineered COYNE ELECTRICAL held in place in the BC -625 by a piece properly, SCHOOL and furthermore has proved Radio Division. Dept. 47.71 of Mycalex strip which is bolted to the itself in long and gruelling service. CHICAGO 12, ILL. right cover plate enclosing the final am- Should B- batteries be used for bias, one plifier compartment. The photograph may expect long periods of service from FREE TRIAL COUPON showing the final amplifier tube- and them. tank circuit makes this clear. By turn- EDUCATIONAL 0001( PUBLISHING DIVISION. As it stands, the unit is a dandy little COYNE ELECTRICAL 6 RADIO SCHOOL. Dept. 47 -T1 ing four locking screws, tubes are easily 500 S. Pauline St.. Chicago 12. III. 12 -15 -watt crystal -controlled 144 -mc Send nm Coyne's new 3- Volume Set. 'APPLIED changed, antenna coupling adjusted, etc. PRACTICAL RADIO" for FREE. examination. After 7 transmitter. It will also serve nicely as álay. 1'11 either return il and owe thing. or low 3h total a driver for more power later. As a Irae Ìn 7nclaa r.FREI, Consulta. Tuning procedure lion Service. Technical Bulletins and 10 to 1 Guar- mobile job, the unit is unsurpassed, antee. Tuning up is quite simple and and, in the event that occasion should NAME AGE straightforward. The circuits are de- ever demand emergency operation it ADDRESS TOWN ZONE.... STATE signed so that there will be little likeli- should do a fine job as a QRR trans- acme C.O.D. VII pay postman $0.75 plus C.O.D fee. Same money back guarantee after 7 -day trial hood of incorrect harmonics being select - mitter.

RADIO -CRAFT for APRIL, 1947 75

PROMPT SERVICE ON ALL Minimum Order 52.00 -20% Deposit Required on all SPEAKER AND PHONO APRIL olden. Please Add Sufficient Postage. WRITE UP. REPAIRS ONE DEPT. RC4. LEO SPECIALS TUBES: Perfeet condition, but not In sealed cartons. ! ! I SURPLUS SPECIALS ! ! ! p'r Guaranteed for 90 days. ELYYN 3G SYNCHROO.TRANSM hi. 1151,: 0 s 26, 27 or 56 .29 pairs SERVICEMEN'S KITS s 24. 42, 75. 77, 74. 80. 5Y3, 615. 6116, or follower. 31/2"x5 ". Per pair 112 Its/ n 310.49 111(7 .39 UHF BUTTERFLY TUNING CONDENSERS. Silver - 1-R.F.. Antenna and ose. coils. 10 woad .98 s 50, 0A3, 6A8. 6SA7 or 12SK7 .59 plated, twin rotors. ball bearing shafts. Ranges: s 2dede asstd. Brand RCA UX -200 tubes In sealed cartons moulded anda r ne-edveulnetie Inch " 135.485 MC :0.D.41/4í1 or 240.1200 MC (0.D. l Ideal 1X1045 detector. a clac 1.00 21/2.). Either type 2.49 Less volto a °LI.. 2.00 AMPLIFIER WAFER SELECTOR SWITCHES. Alt with shafts 5 .29 l electronic supercharger control. 110V 1 400ycle. Iouble pole. position Black crackle finish cale & elide -in chassis. Con- Double pole, 6 position. 2 decks .39 taint. power trans. 7 mira and il cond. 7 re- single prole, II Position. 3 decks .49 sistors. 4 foetal rockets plus other components RADIO HARDWARE TREASURE. Over 1000 sm worth several times the price. 83/.'x449- x34.1". twher.. lugs. etc. PLUS handy 36 com- tu 1.19 partment cardboard kit box .59 POWER RHEOSTATS. Hey duty, standard brands. 25 watt-20. 50. 100. 200. 375, 500 or 1000 EXPERIMENTAL TUBES. 20 asstd. sine and base -39 types for testing. research, etc. Fil. tested 1.00 ,u watt -2, 40, 75, 250, 500. 3E. 7.5K or CAN AND CHASSIS FOUNDATION. 5 tuba punched 10K ohms 1.29 cover. Cadmium plated Steel. 11-a 1411CIAL! -SO watt -15 ohm .9S ( "xsÿ'd .95 Cathode Ray . 14 prong .. .49 Celotex speaker Baffles. 14"x14 "xv9 ". Specify size O ft. Whip Antenna. Flexible, lightweight (B 6:.) x k .35 10 sections. Weatherproof finish 1.39 BAKELITE MII I I '\I,: 'rAS1 80 ALUMINUM PANELS 1.072 .1: 8ti40" .39 Antenna Base. 180 degrees. II 3- \ Heavy duty. adjustable asstd. .000o)11 to ._mil. 200000WV 8"xS" -.lee; R'xlM' 59: S "15^ .79 Mtg. 6Vx44y ". C..mplete with hanlware .49 clearly marked 2.95 BAKELITE PANELS: g glossy brown. 7 "xl0" .59 Binding Post. (TM 175) Hey duty plated brae, 4-Tubular Condensers; 7"x14 " -.69; 7"í18e-.79: 9 144 .85 needle contact, knurled bead. ley" O.D.. 44" high II .001 r.2inf6. . SStandard Vs. Linen Bakelite Strips, 11"xl Va "-3 for .25 -12 for 1.00 2.9 Speaker Grille Cloth.afuDDeorative gold r silver ltt'ADITIONES-Ana 115 -33. 2000 how. Leather s 55514. stmts. weave. .20 Rubcovered, adj. forks. With PL -54 plug 1.73 slide- rule Sand glass nclded) 2.98 Victor Power Transformer for models 8-32, 45. 52 ber phone cushions for above. pair .20 II 7- Escutcheon Plates: 23 W. airplane or 75. Unshielded 5.95 Headbands (HS33) only. with 1'1. -54 & eon' .39 slide-rule and full- vision ty es. 2.95 UI'DT TOGGLE SWITCHES (HAH) 6A /125V. eater- 17:54 plug t 13' tipped double phone N .11 II s-- Knnoba: 25 mind. wood and bakelite slat lugs, bakellte caw. Split ball .39 jack (N Tho"T .23 push-on, setscrew and pusInbutton Frequency eterf Tech. SManManual (Navy) & l.on . 15 WPea operation. 30 Ulna. A .h:,rramc. 53 C 0-Wafer Socketa: 12 asstd. 4 to 7 prong .15 '1' \I'ra Tech. 51.mu..1 \r ^rr)'r rare niant.. In li.410.110 10- Voltage Dividers; 10 agent standard. .39 multi-tapped. HI- wattage's included 1.98 leo N.B.C. RECORDINGS. For hors. P.A. II -Shield Cans; 15 s.,tal. for coils. tubes, systems. aemonetntion. etc. Each transformers, etc. 1.00 tam. 2 complete. different 15 min. ALNICO MAGNETS 12 -M1en Padden and Trimmersl 1553514 Voice of the Arany" dramatic pn- 1.49 multiple and ceramic base .89 music. different 141.-Volume d mToneControls: IUtykes asstd. ttemuxles, such the Beam,e Dinner .ire-wound and carbon. Leas switches 1.49 Urate. elf-33-1/3 RPM. 15- Wire -wound Resistors: 15 asstd. ohm - .. assW. records ages,S 20 watts: Incl. enameled sad nn to .98 10-1 F Coll.; O asstd., Including shielded and lug -tuned. Peaks unmarked 1.95 17 -Dial Window s; 12 avoid. x . incl. II 1-tMr hat and moulded acetate and convex glass 1.29 irr 1,irtar s lengths, per inch IS-Bakelite Coll Forms: 18 asstd. point. 22-Face it:ea1:1e"xT's' ht., far mixes up to 3" diem. 8 s3 -Healy dut bar. 2y§"x14tr '15 /16" .93 In -high Resistance Units: 25 wad. car. t4 -Fare Ittesiry5 xB/ high bun, ferruleended. 25000 to 5 moxohms. .49 II 5- Polished. y 4A9y high ,35 8- Polished bar, 9/16.9(14.204.. 20 for 1.00 20-SPEAKER REPAIR KIT. A real money #7 -Fare 49.xi/ex49" high .10 and time saver. Contains: 20 asstd. paper CO. ¢6.- ALNICO V, shoe, poles We' M. We high .75 rings, asstd. voice RADIO g0- ALNICO Y.h shoe. Poles 9/18" e4. 119" fo s. 3 yd.. felt 2gtrps.. 20 chamois high ,98 leather segments. kit of 16 shims and MAKERS OF CONES AND FIELD COILS tube of Spkr. cement All for 2.9 II 10-ALNICO V,h',hoe. poles 1"alL'a"x2 d" YORK 7, high 5.95 .. 21 -Metal Cased BPase C,nrlensers: 20 85 -67 Orr STREET. NEW N.Y a 11 hoe ea. pole 11 /16r" 0.13.. 21/4" anent. paper-wound, multl-sectlon: 200. 1.29 .1nOWV .98 WORTH 2. 0284 -5 -high .35 a 12- ISlmllar to s5) 4 cx.%tit7 /18- 21 Itass -nlï, ^na An n mar 2 carbon and (mag- 3. s 14-Polished red rl. 1'3 le 0.0.1. 12,000 SO FT. OF RADIO PARTS netisedetiduty lengthwise. w1 eona"is) p rrow 1.29

Another MILO First! COMMUNICATIONS The Sensational New SHOULD SAPPHIRE NEEDLES BE USED? EDWARDS FM TUNER FOR IMMEDIATE DELIVERY Dear Editor: and to prolong record life. A new steel The otherwise excellent article by needle, being relatively sharp, has a $52.50 J. C. Hoadley entitled "Sound System point pressure on the record of from 20 Fedoras: Improvement" was marred, in my to 100 tons per sq. inch. In a matter of * New Type Tunet (Three High O Tuned Lineal opinion, by the writer's contention that seconds, this needle point area is so re- * Full FM Band Coverage 87.5 to 109 Megacycles is lowered to * All tuning itnee and contacts silver plated sapphire and diamond tipped phon- duced that the pressure * Permeability tuned ceramic I F and discriminator ograph needles are "easy" on the rec- about 5 tons per sq. inch. It would there- lrans(ormers fore seem obvious that a jewelled point * AC operated 105-130 Volt--60 cycles ords. Self contained power supply Several articles in recent technical (which is practically immune to wear B Tubesl GAGS, 610 two 6557. 65117. GALS. 5E5, 754. Shipping vreight ñpproaimately 10 pounds. publications have served to show that by.the record) will cause very large Orden shipped Rotaonti f Receipt. a needle point However, maybe If not rated. 20.4 with order, records can be easily ruined after few pressures. balance C.O.O. Dept. C. plays with a hard -tipped needle. I be- some other considerations enter into the Milo Radio and Electronics Corp. lieve a past issue of RADIO- CitArr car- picture. 200 GREENWICH ST., ried a testing laboratory's report that Perhaps, Mr. Editor, RADIO-CRAFT BEekman 3.2980.1 pointed needles were "ex- could carry some scientific analysis of address 'MIlolectIa New York" sapphire Cable cessive" in their record wear. The Bell this controversial question. Until then, RADIO SERVICEMEN Telephone System's Monograph B -998 this writer will continue to use fibre Mels1ner I.F. Coils 465 K.C. lai. Gain 50.59 needles which cannot injure the records, Meissner Osnll. Coils 463 K.C. 3 Tap .39 (on recording and reproducing ma- Speakers, Tenor Alnico V 4" or 5" 1.69 terials for disk recording) states that and apply treble accentuation in the Mallory 10 -10 450V-20--25V F.P. Cord .85 Cadet 20- 20-159V lklydensors .49 an abrasive material is included in com- interests of high fidelity. By l'ut Cond. -600V .005- .01-02 .07 NEEDHAM, Centralab Vol. Cont. with switch -6 Meg. .59 mercial phono records, in order to grind EDWARD R. Resistor Hit -100 Asstd -1/3 to 1 watt. BA A- 1.95 needle of Drummondville, Quebec Tubes -1T4-1115- 185 -384 .97 the to fit the groove the record, Nationally known S and e tube radios Write today for oetr lise soec&Is JOYCE RADIO OIBTRIB. CO.-Hollywood 28. Cal. MR. HOADL EY REPLIES RADIO TUBES Dear Editor: needle." Transcriptions consist of either Moat Critical Types in Stock S0L6.1A7,35Z5,etc. or Brand New, in Sealed Cartons In reference to Mr. Needham's letter, soft vinyl acetate original recordings 100% GUARANTEED I would like to quote directly from page vinyl pressings containing no abrasive. Repairmen and Dealers, Write For 52 of the November RADIo- CRAFT: "In It is not considered good modern prac- Available List at Trade Discounts the case of transcriptions, it is nec- tice for a needle to fit the entire groove, RADIO -EXPERTS essary to use a light weight pickup, but rather it should ride approximately 178 E. 33rd St.. Dept. C. Paterson 4, N. J. preferably with a sapphire or diamond half way between the top and the bot-

76 RADIO -CRAFT for APRIL, 1947 U. S,i SIGNAL CORPS 2-WAY TALKING SYSTEM 10 METER CONVERTER A Western Electric product. Use them for inter-office com- 27 to 30 Megacycles munication, house to garage, mother's room to baby's room, on the farm and many other places. Sensitive enough to pick up the slightest whimper. Sturdy all steel con- Designed for Army surplus receivers struction. Has push-to-talk switch. Speaker is built in. such as the BC 342, BC 348, BC 312, Tube line -up 5Y3, 6SJ7 and 6K6. Can be used as a 4 -watt etc. Uses a single 6SA7 fixed oscillator modulator for your ham rig. The small unit is a speaker - at 16 megs. Adjust plate output and receiver. Connect as many as 10 speakers in parallel. Comes grid input signal for maximum. Cali- ready to operate. Just plug into 110 volt AC line. 100 ft. of A and entire band on speaker cable is supplied. Complete with master and brate tune the onesspeaker-receiver 3 250 your receiver. The power for the con- verter comes from the receiver. Our special adapter secures the power from Extra speaker -receiver $495 the receiver by a plug -in arrangement. When this is not possible instructions will indicate the .,onset tapping point. RADIO PARTS HOT SPECIALS In ordering be sure to mention the ASSORTMENT model receiver. Pfundrede of valu- 1619 Tube. Characteristics Complete Instruc- able and useful ra- same as 6L6 only with dio parts. Trans- a 25,6 volt filament. Use as a replacement tions and formers, coils, con- fora 47 or a 2A5 $ 69 plans $1.00 densers, sock- Kit of parts and ets, escutcheons, 20.7 Megacycle double iron core tuned IF trans- plans for lugs, etc., etc. formers. Four to a complete set. Use them for FM complete $12.00 or Video. Can easily be trimmed down to 10 Mega operation. 1A0 nu. á1.6r9 with a single ceramic condenser, $298e . Set of four matched coils iß Complete unit HS -30 HEARING AID wired 61.6 Output transformer $1.79 and TYPE HEADSET tested... Hi- fidelity, flat, from 100 to 2500 Ohm 100 Watt adjustable resistor.. $ 049 10,000 cycles, impedance 128 Kit of 50-1 and 2 Watt resistors, sizes 25,$1.008g8 Ohms, will operate across low 1(A), 1000, 3000, etc impedance voice coil. With w matching transformer imped- BC-312, 342 I.F. Crystal Transformer, resonant BROADCAST BAND ance is 8000 ohms. Brand at 470 KC. Replace new, complete with plug that 1st I.F. with this unit CONVERTER and thOseavwded $6.49 transformer 51.98 an- 100 KC te 1660 KC For owners of Amy -Navy surplus Double Button Mike -to-Grid Trans $ 59 receivers. Adapter supplied uses 6SA7 tube miser -oscillator. Kit of 10 R.F. & Osc. Coils $ .98 Beats BC signal against 3 Mess. Tune In on short wave. 1 esud Pwr: Trans.350 350, 60Mils,6.3v ® 3a,$2.15 with BC-312, 342, NCIOO-Atilt, HS -16 HEADSET (a 2a BC -348 and others. In 5v ordering state mode... $15.00 Noise -proof, rubber-cush- RA -20 Power Supply -for Signal Corps Receiver Cash, Check or M.O. Write Dept. C -A ioned, equipped with 2 match- BC-342. Replace battery pack on BC -312$1 4. 8A ing transformers, magnesium to convert to 110v, AC operation -N+ 7 earcaps. A superior headset. THOR ELECTRONICS 8000 ohms imped- Output Transformer -Pri. 10,000 Ohms, 5051 N. St., III. ance. Brand new... 52.98 Sec. 4,000 250.4 CM= $ 69 Clark Chicago 40 tom of the groove. Modern pickups the next needle. It is interesting to note designed to play these transcriptions that broadcast stations replace their POWERFUL ALL- PURPOSE operate at pressures from 0.3 to 1.0 sapphire playback needles as often as ounce and consequently do not cause once every four months, showing that INDUCTION MOTOR such high pressures to be exerted on they are not as hard as one might think. IDEAL FOR MAPERIMENTLRS -101 USES Sturdily eo tructed to pclaleanself the walls. standard.. 8M1Ì. -starting shaded groove Furthermore, it is an Authorities for the information on pole A.C. Induction r is pow- verified erful number uses. easily fact that sapphire has the shape of playback styli are Isabel L. of h.see are: u d Tim- ing Devices. Current Interrupters. the lowest coefficient of friction of all Capps, owner of the company which Electric Fane. Electric Chimes Window Displays. Photo-ell Conb-ei the needle materials. The best Devices, Electric vibrators. Small pickups grinds all the recording needles and Grinder.. Suf.,, and Polishers, Miniature Pumps. Mechanical Mod - all use jeweled styli and you will find jeweled playback needles, and Howard 1.. Sirens. and other ilou.. Spollea- that broadcast stations play both tran- A. Chinn, Chief Audio Engineer, Colum- Consumes scriptions and shellac pressings with bia Broadcasting System, Inc. (Elee- power oa a nete5d of 3.000 sturdy unit swillconstantly con oper- sapphire -needle pickups almost exclu- troni.,Industries, November, 1946 issue; ate . turntable loaded Wit 200 lbs. dead weight-THAT'S POWER! sively. A very popular high by pickup with pages 64 and 65). ha.. a uewwient iw studs: shaft is tidlon`p by 3/160 diameter and in self-aligning Mt- these stations is the Western Electric The situation is further clarified by retaining bearings. aigned volts. 50 -60 cycles. A.C. 110.20r 9A pickup which uses either a sapphire the release of the new series of Vinyl ITEM NO. or diamond needle (Western Electric pressings. The old shellac pressing is YOUR PRICE $2.95 builds Bell Telephone equipment). They on the way out. These new pressings HUDSON SPECIALTIES have brought out a new pickup, the 9B, contain no abrasive, will yield almost 40 West Broadway, 7ept. RC4 -47 for use with shellac pressings, and it noiseless reproduction with a light NEW YORK 7, N. Y. also contains a sapphire needle. weight jewel -point pickup and will last The use of a sapphire point pre- almost indefinitely in the process. supposes a light pickup, preferably one J. CARLISLE HoADLEY, ORDER NOW with a built -in needle. West Newton, Signal Corps 1 -222A Signal Generator Mass. 8 to 15, 150 to 230 MC 869.95 In conjunction with the use of fibre 300 Ohm Amphenol Twin Lead, per 100 ft 2.90 75 Ohm Amphenol Twin Lead. per 100 ft 2.00 needles, where do you suppose the P2223 Army Bead Set. 8000 Ohm with 5 ft shavings needle RADIO- ELECTRONIC CIRCUIT Cord nd plug 2.95 from the go? They are 3 Gang 110 MSIFD. Per Section Condenser. Ex- forced into the smaller groove modu- (Continued from page 54) cellent Quality 2.95 2' I'M Speaker (Bakelite cased) used ln Walkle lations and firmly fixed there by the Talkie 240 Transmitting Tube 1.49 high unit pressures of each new point. its motor can be used on either type of National ACN Dials 3.00 This effectively removes the 4 MFD seo Volt Olialled condenser. standard higher fre- current by adding a small 117 -volt a.c. can mountin 1.59 quencies from the record and causes inverter and a 4 -pole 2- position switch JAN Uwe 2c40 Lighthouse tube. new in canons 3.95 Complete line of RCA, TAYLOR, OE, and EIMAC distortion of the remaining lower ones. to cut in the inverter for d.c. operation. Tubes. Write Us Your Needs in Any Nun Equipment, A new steel needle does very much the If the entire unit is designed to oper- DOW RADIO same thing except that it leaves micro- ate from a.c. lines, a heavier inverter 1769 E. COLORADO PASADENA 4, CALIF. Pasadena Phone-SYcamore 7.1196 scopic sharp steel cutting tools em- may be used and the amplifier power Les Angeles Ryan 16663 bedded in the record material. This in- cord connected across its output. creases the surface noise and is in- GEORGE A. FELIx, Cost of television antenna installations strumental in more quickly destroying Valley Stream, N. Y. may run from $35 to $50."

RADIO -CRAFT for APRIL, 1947 77 HIGHBRIDGE'S BEST BUY INDEX TO ADVERTISERS NEW DYNAMICNAMIC Abell Distributing Company 72 National Radio Institute Adson Radio Company 63 Van Sant, Dugdale & Company TELEVISION KIT Bass & Weber Company, Inc. National Schools II Advanced Radio Products 65 The Mayers Company Allied Radio Corporation 45 N. J. Industrial Company 73 George Brodsky Advertising Newark Electric Company 60 Almo Radio Co. 42 The Charles Brunelle Company E. L. Brown Advertising Olson Radio Warehouse 59 American Sales Company 72 Jessop Advertising Company American Television Laboratories, Inc. Opportunity Adleits 71 Inside Beck Cover Pa -Kett" Radio Company 71 Turner Advertising Agency Arrow Advertising Company Amplifier Corporation of America 71 Pearce, Jr., George W. 67 Sternficld- Godley Precision Apparatus Company -- 70 Audel Publishers 79 Shappe- Wilkes, Inc. Grant & Wadsworth Audio Sales Co. 70 RADIO SCHOOL DIRECTORY Bass & Weber Company, Inc. (See Page BO) Labs 6 Bell Telephone American Radio Institute N. W. Ayer & Son 69 Stern field- Godley Brady, W. H. Baltimore Technical Institute Brady. Parkinson Company George 74 Boston Technical Institute Brooks L Associates. Candler System Company The Schram Advertising Company 51 Rand -Ries Advertisi g Buffalo Radio Supply Commercial Radio Institute International Advertising Agency Applebee Company 65 Don Martin School of Radio Arts Burstein- Hollywood Sound Institute Frank E. Whalen Advertising Company COMPLETE $15950 68 Nelson Advertising Service C. F. Cannon Lincoln Engineering School With Tubes -Parts- Cabinet M. J. Werner Advertising Buchanan-Thomas Advertising Capitol Radio Engineering Institute 13 Associates Melville Radio Institute Exclusive Mail Distributors Henry J. Kaufman & Seidel Advertising Chief Electronics Milwaukee School of Engineering Cheek These Outstanding Features: Company of Advertising The Graphic Klau -Van Pieterson- Dunlap Associates Three stages of yideo I.E. nmpllflcation--3.5 M(' Cleveland Institute of Radio Electronics 59 lane width. RCA Institutes Kenneth Kolpein Advertising United Radio -Television Institute Receiver may be aligned easily without use of Commercial Radio 73 signal generator. voltage analysis chart for Goulsfon Company, Inc. Complete resistance and 12 easy trouble shooting supplied with each kit. Communications Equipment Company Radio Center 64 If transformers are slug tuned for high gain and Borough Advertising Company Radio Corporation of America 41 maximum efficiency. Concord Radio Corporation 53 J. Walter Thompson Advertising with earls untt. Safety Interlock switch auppiled E. H. Brown Advertising Agency Radio-Craft Library Series 84 Simplicity of operation -only 5 controls on front 53 Supply Co. 71 panel. Constant Electric Radio Dealers Schematic diagrams are broken down Into simple Cornell- Dubilier Burke & Wayburne Advertising Agency circuits for easea In wiring. Reiss Advertising Radio Electric Service Co. 73 Picture is very stable -does not Jump or tear out Coyne Electrical School 62, 75 David Zibman Advertising even receiving conditions. under unusual Phil Gordon Advertising Agency Radio -Electronics Publishing Corporation * 63 4 Channels- provisions for six. School George Elliott Advertising Seventeen tubes including largo picture tube. Coyne Electrical is Inches in diameter and gives McJunkin Advertising Agency Radio-Experts 76 Picture tube seven 60 a picture 26 square inches In size. Crabtree Wholesale Radio Radio Kits 67 All parts are unconditionally guaranteed to he D. & D. Radio 74 Hamburg Advertising Agency electrically and mechanically perfect. Dales of Denver 69 Radio Parts Company 61 Set cornea complete with all necessary information Bill Bonsib Advertising Sydney Levitt Advertising sheets. parts. drilled and punched chassis. beam - Deer & Taylor, Inc. 73 Radio Supply & Engineering Company 16 folly anisheil front panel and modernistic cabinet. W. Curtiss Advertising Karl G. Behr Advertising Agency Hardware and other necessary items are also In- Spencer NOTHING ELSE TO BUY. DeForest's Training Institute 9 Radionic Design 71 Louesen & Salomon Radionic Equipment Company U Dow Radio 77 Republic Advertising Agency SONAR SOUND DETECTION UNIT Editors & Engineers, Ltd. 63, 77 Radolek Company n 66 In Original Oversees Parking Electronic Park Inc. 63, Turner Company Ideal for detecting underwater sounds within an Campbell & Reynolds Advertising Reed Mfg. Co. 67 atta of 15 miles. Using a Rochelle salt xtal as the Eue Radio Co. Rosicruciens, The 66 active unit the sound is transmitted up GO ft. Gary A. Ruben Advertising Richard Jorgensen Advertising cable. Completely enclosed in a solid rubber sheath Gateway Company 60 Howard W. Sams and Company. Inc. 6 Originally used in harbor defense. Coupled with Mfg. Company n Aitkin- Kynett Company audio amplifier It has many valuable $7.95 General Cement Sander Rodkin Advertising Agency Schott, Walter 66 General Electronic Distributing Company 61 Ross. Gardner & White Advertising Bass & Weber Company Inc. Sheffield Radio & Appliance Company 60 SELECTRON SELENIUM RECTIFIERS General Test Equipment Co. 73 Sidney K. Lenby Advertising Suzanne Hayman Advertising Simpson Electric Company Inside Front Cover 50 to 99 .85 Harrison Radio Company 67 Kreicker & Meloan Advertising Altomari Advertising Agency Sprague Products 16 6 to 49 Haydn Chemical Co. 66 Harry P. Bridge Advertising Agency Melvin F. Hall Advertising Sprayberry Academy of Radio 7 I to 5 99 Hershel Radio Company. 14 Harry P. Bridge Advertising Agency 66 quotations on larger quantities Hugh Allen Agency Sterling Electronic Company furnished upon request Highbridge Radio -Television 6 Appliance Co 78 Superior Instruments 43 Inc. FOR AC -DC Portables Burke & Wayburne Advertising Agency Bass & Weber Company, USEFUL * * Interesa 4 Power Supplies * Console Rados Replaces 29 Hollywood Radio 6 Television Supreme Publications 62 Types of Rect. Tubes Barton A. Stebbins Advertising Henry H. Teplttz Advertising Gives Instant Reception -Requires No "Warm TJp" Hudson Specialties 77 Sylvania Electric Products, Inc. 2 Replaces Tubo & Socket -Prolongs Life of Set Instructograph Company 66 Newell- Emmett Company Requires Less Space-Increases Sensitivity Turner Advertising Agency "TAB" Technical Apparatus Bldrs. U Made to Last The Lite of Use Set International Resistance Company B Bass a Weber Company, Inc. John Falkner Arndt & Company, Inc. Telectronics Service & Supply Corp. 53 NEW BATTERY Joyce Radio Distributing Company 76 Burke & Wayburne Advertising Agency 77 BOOSTER Katolight 67 Thor Electronics Greve Advertising Agency McGivera- -Child Co. Powerful-Elflelent- Lafayette Radio Trutone Products Company 67 Economical Reiss Advertising Agency Moselle & Eisen A compact. lightweight. Leeds Radio Company 50 Turner Company 47 automatic. constant volt Bass & Weber Company, Inc. W. D. Lyon Company age battery charger which 52 Is especially designed to Leotone Radio 76 Variety Electric Company Bass & Company, Inc. bAdp var. tusk Or tractor owners keep 0 volt storage Altomari Advertising Agency Weber batteries fully charged. 4':4'x5". Weighs 4 lbs. Lifetime Sound Equipment Company 68 Wayne Engineering Company 66 packed. Operates on 105.120 r AC 60 Cy. DC 6 v The Miller Agency Company Wright, Incorporated 71 6 AC cord with molded 4 -2 amp. Complete with ft. McGee Radio 68 Kay Arivefising robber plug and 0 ft DC cord with Company X.L. Radio Labs 69 alligator clips. $1 1.95 Westigate Advertising McMurdo Silver Company 46 Edward Owen & Company NEW No. 631PI /SNA Class Strobotron tubes. Back 53.25 P. R. Mallory & Company, Inc. Cover Each Aitkin -Kynett Company BARGAIN PRICE LIST! Switchboard 74 Laboratory design and construe(ion Maritime Competition is increasing. Write for catalogue for Vision Research Elec. & Instrument Company 57 Radio of modern 5 or 7 Inch television receiver Instruction Metropolitan low price, quality l'arts. Test Equipment, Rook end complete set of coils. Special $6.95. Bass & Weber Company Inc. Kits. end Indio Receivers. Gtorp. 76 Milo Radio & Electronics SUPPLY COMPANY Burke end Wayburn Advertising Co. "loin DEALERS Ail Prices FOB New York City. N. Y. 135 Liberty St.. N. Y. 6. N. Y. Murray Hill Books Company 44, 49, 56 HIGHBRIDGE RADIO - TELEVISION Harry P. Bridge Advertising Name Nation -Wide Radio Company 74 & APPLIANCE CO. The Schram Company Address 74 NEW YORK IS, National Plans Institute 340 CANAL 49 City Zone. State 343 CANAL NEW YORK National Radio Distributors Burke & Wayburne Advertising Agency for APRIL, 1947 78 RADIO -CRAFT ß0(1lí REVIEWS 7 DAYS FREE DRAFTING FOR ELECTRONICS, by The first of its five sections covers L. F. B. Carini, Ph. D. Published by Mc- briefly the basic television system. The Graw -Hill Book Co. Stiff cloth covers, second gives a general over -all picture EXAMINATION 6 x 9 inches, 211 pages. Price $2.50. of the television video signal as it is A book on drafting for radio and picked up by the receiver and the third electronics has long been needed. This section provides a clear -cut step -by -step work is the more valuable because of analysis of the receiving equipment, il- the author's thorough knowledge of the lustrated with block diagrams and basic. principles behind the schematics. As he schematics. The authors discuss briefly himself points out, "knowledge of the the types and properties of television fundamentals of circuit development is receiving antennas in the fourth sec- to be regarded as desirable" to any tion. The concluding section contains 30 draftsman who is to do justice to a pages of detailed reference material on radio schematic. servicing a television receiver.- R.F.S. The book is useful both to the drafts- man who wishes to do electronic or radio drawing and to the radioman who RADIO ELECTRONICS QUIZ BOOK, wishes to learn fundamentals of drafts- prepared under the supervision of R. L. manship. Such fundamental matter as Duncan. Published by Radio -Electronics the selection and handling of drafting Publishing Corporation. Heavy paper tools and materials, covers, 8 1/=x11 inches, 108 pages, type- essentials of letter- writer type. Price ing, and preparation of drawing prints $2.00. are presented. Three chapters are de- This radio quiz book contains over voted to the schematic diagram, and 1,200 questions and answers in a "true two others to patent drawings and in- or false" examination. It is divided into dustrial electronics practice, respec- several sections: Basic Theory and Prac- tively. tice; Basic Radio Law; Radiotelephony; RADIO FACTS Advanced Radio Telephony; Radio- THE AND FIGURES SERVICING OF TELEVISION telegraph; and Advanced Radio-tele- AUDELS RADIOMANS GUIDE -914 Pages, 633Illus- RECEIVERS, prepared and published graph. The questions are numbered con- trations, Photos, Wiring Diagrams, 38 Big Chapters, by the Covering Radio Theory, Construction, Servicing, Includ- Service Division of Philco Cor- secutively from 1 to 1,289. Two ing poration. Hard sections Important Data on Developments in Television, paper covers, 81/3 x 11 in the back of the book give the an- Electronics and Frequency Modulation, Review. inches, 140 pages. Price $2.25. Questions and Answers, Calculations & Testing. swers. -The first states whether the Highly Endorsed -Indispensable for Ready Reference This book is a timely addition to the statement is true or false; the second and Home Study. bookshelf of the radio serviceman gives the correct answers S4 COMPLETE PAY ONLY $1 A MONTH who for the false Step up your own skill with the facts and figures or may have occasion to install and serv- statements. your trade. Audels Mechanics Guides contain Prac- tical Inside Trade Information in a handy form. ice television receivers. The text is so Schematic diagrams are Fully Illustrated and Easy to Understand. Highly provided for Endorsed. ('heck the brook you want for 7 days' prepared that it may be read with equal many of the questions. These are simple Free Examination. ease by a technical or non -technical in form, showing fundamental Send No Money. Nothing to pay postman. circuits, CUT reader. It is exceptionally well illus- single stages, or parts of two stages in pi' - -- HERE - --- trated with photographs and diagrams. transmitters and receivers. MAIL ORDER AUDEL, Publishers,49 W.23 g St. NY. 7.m Moss* Md me postpaid for EXAM NATION poet arke a to, elow. decide to teem I stre tO In goys book ana further 51 mannMr on rSh ook ni y pall mks. rs l... 1 wretln m. RADIOMANS GUIDE, 914 Pages . . . $4. ELECTRICIANS EXAMINATIONS, 250 Pages . I. WIRING DIAGRAMS 210 Pages . 1. ELECTRICAL DICTIONARY 9000 .Tsrms . 2. ELECTRICAL POWER CALCILLAO T IONS. 425 Pas. 2. HANDY BOOK OF ELECTRICITY, 1340 Pages 4. ELECTRONIC DEVICES 216 Pages .. 2. ELECTRIC LIBRARY 1i vol.. 7000 Pgs., 51.50 vol. OIL BURNER GUIDA, 384 Pages ...... 1. REFRIGERATION & Air Conditioning, 10 Ps. 4. POWER PLANT ENGINEERS Guide, 13u0 Pages. 4. PUMPS Hydraulics &AirCompressors, 1658Pgs. 4. WELDERS GUIDE 400 Pages 1 BLUE PRINT READING, 416 Pages . . 2. SHEET METAL WORKERS Handy Book Pgs.338 Pgs. SHEET METAL PATTERN LAYOUTS, 1100 Pgs. 4. AIRCRAFT WORKER, 240 Pages . 1. MATHEMATICS & CALCULATIONS.700 Pgs.. 2. MACHINISTS Handy Book 1600 Pages . 4. MECHANICAL Dictionary, 968 Pages 4 DIESEL ENGINEUMANUL, 400 Pages ... 2. MARINE ENGINEERS Handy Book, 1280 Pages 4.

SHIPFITTERS Handy Book 272 Pages . I. MECHANICAL DRAWING COURSE, 160 Pages I. MECHANICAL DRAWING & DESIGN, 480 Pgs. 2. MILLWRIGHTS & Mechanics Guide, 1200 Pgs. 4. CARPENTERS & Builders Guides (4 vols.).. 6. PLUMBERS & Steamfitters Guides (4 vols.) . 6. MASONS & Builders Guides (4 vols.) . 6.

GARDENERS I& GROWERS GUIDES (4 vols) 6. ENGINEERS and Mechanics Guides Nos. 1, 2, 3, 4, 5, 6, 7 and 8 complete ... 12. Answers on Practical ENGINEERING . 1. ENGINEERS & FIREMANS EXAMINATIONS . 1.

Nome

Address

Sugges ed by: W. D. Moss. Washington, D. C. Occupation _ Every time I tune in Frank Sinatra -it squeals. Employed by- - RADIO -CRAFT for APRIL, 947 79 RADIO SCHOOL DIRECTORY

PREPARE NOW FOR SKILLED JOBS IN RADIO AND ELECTRONICS RCA INSTITUTES, Inc. 11 Offer thorough training courses in all technical phases of technical Radio and Television INTENSIVE COURSES -Thorough, DAYS -EVENINGS WEEKLY RATES RCA Inetitatte h pproved education for progressive men and women. VETERANS: under G. I. BIII of RIghU the State of New York Write Dept. RC -al 1. RADIO TECHNICIAN The MRI General Licensed by For Free Catalog Course. Includes F.M. & Television. Prepares RCA INSTITUTES, Inc. For FCC Broadcast Licenses. A Service of Radio Corporation of A mariea MELVILLE RADIO INSTITUTE NEW YORK 13. N. Y. 2. RADIO & TELEVISION SERVICING-Pre. 75 VARICK STREET pares for employment as Repairman on Stand 45 West 45th St., New York 19, N. Y. and Broadcast, F.M. & Television Receivers. E> GENTLEMEN: RC LEARN 3. RADIO COMMUNICATIONS -Prepares for FCC Operators License. Leads to position os Send me FREE Information about Merchant Marine or Flight Radio OfRcer;Com- RADIO -TELEVISION -FM mercial Operator. your school. Complete courses in all phases given in both 4. FUNDAMENTAL RADIO MATHEMATICS- day and evening classes. The MRI Preparatory Course. Required pre. Name Veterans accepted under G.I. bill training for students lacking a basic mathe- matical background. United Radio Television Institute Address 225 Halsey Street Newark 2. N. J. MELVILLE RADIO INSTITUTE 45 W. 45th St., N. Y. 19, BR 9-5080

"96 . Amiss . - A/aidu Rd4.Maer" L B!I RADIO RADIO Technician and Radio Communications counts RADIO -TELEVISION TECHNICIAN'S COURSE Reoister now for new classes starting first MONDAY of each month. Day and Evening Classes New Classes starting every 5 weeks. Women Students invited. AMERICAN RADIO INSTITUTE Approved for veterans- Public Law No. 346 and No. 16. 101 West 63rd St.. New York 23, N. Y. Write for Free Bulletin on Courses APPROVED UNDER GI BILL OF RIGHTS. HOLLYWOOD SOUND INSTITUTE, Inc. 1040 N. Kenmore Ave., Los Angeles Dept. B MO I-2345

PIS 1 CORRESPONDENCE COURSES IN REFRIGERATION RADIOand ELECTRICAL ENGINEERING Pe a -last' man. tasen bow te nd end I' A N D AIR- CONDITIONING eases in code by telegraph and'vradio. Commerce news thousands ELECTRICAL ENGINEERING ááe `o,°t,tgp ñelá of lobs. Prepare yusfLanne' Eoaeen interesting Learn atyIma..squick: course. So canundetanQuickly. fael.grnwing nIndustry. aadedtdweea for information. 1 through famous Candler System. mpliedy. orsÉ t'rrp:m e,r high pay VETERANS Write for FREE. BOOK. RADIO ENGINEERING g,`,71 :äero.. 'pen io- elecdtlriv art into your Eligible for training sm- CANDLER SYSTEM CO. work. Train. you to be supermervip 1 Y . , Resident der O. I. Dept. 3 -0. Box 928, Denver I. Colo., U.S.A. tuio technician. Servicemen needed badly. Diplomau on 1 CheekBIIM hen u,npletlon. Many graduates t g big pay. for F BOSTON TECHNICAL INSTITUTE PRACTICAL ár8,r o,postcard de iCopies. S Either deferred payment plan. ex- S Course t - i WRITE about 1....n , n TECHNICAL 4 ro, Euci.d' 11.6., e v FOR Lincoln [ á'neeeeringl School. Box 931C-98, Lincoln 2, Nebr. TRAINING YOU COMMERCIAL RADIO INSTITUTE Speriallge 1n Electronics Radie. Eleetrielty. Refriger- alInn, Heating and Air Conditioning. or Welding. A radio training center for Prepare in one year for position as Technician. or in RADIO COURSES two additional yearn secure your B. S. Degree in twenty'six years. Servicing. Broadcast Engineering. Commercial Operating. ELECTRICAL ENGINEERING with major in Ma- Television chinery or Electronics. DOING! INDIVIDUAL LABORATORY WORKI -LEARN BY Write for booklet "Career Building" RESIDENT COURSES ONLY DAY AND EVENING CLASSES Broadcast, Service, Aeronautical, Television and Marine Approved by the Maryland State Department of Edueatlon MMILWAUK££ir telegraphy classes: Preparatory Course now forming. Liter - and the Veterans Administration lure upon request. Veteran training. Classes now forming FREE TO VETS -TEXTBOOKS. TOOLS. TEST SET for July let. Write fur Bulletin CHM of ENGINEERIN "A TECHNICAL INSTITUTE" Y Dept- C. 38 West Riddle St.. Baltimore 1, Md. 5 BALTIMORE TECHNICAL INSTITUTE RC -447 N. Broadway and E. State, Milwaukee, Wis. 1425 Eutaw Plue-Degi. C. Baltimore 17, Maryland SOUND RECORDING SCHOOL A Drartltal n months' course. In Sound Fundamentals. Record !ng. and Hound Transco lesion measunvnent.; in "You slipped on a banana peel and scious ever since. And today, if you a laboratory containing transmission sets. oscillators. be sggaro .avo generator and intermodulation analyzer, and fell down the whole length of the sub- didn't know it already, happeng to other equipment. way stairs -all 32 of them. At the bot- Two complete recording studios assimilating brmi,leaet. APRIL FIRST." motion picture and commercial sound recording. under tom your head hit the steel -clad edge the direction of IT. for Veterana of the last step and DON MARTIN SCHOOL OF RADIO ARTS St., Hollywood. Calif. cracked your skull 1655 Cherokee neatly - but not fatally," said the NEW! man in white. "In- CRYSTRON LAPEL RADIO cidentally, this is (Continued front page 61) the City Hall Hos- pital, and you had grown as big as a coffin. He was holding better rest now." it between his two huge hairy, ape -like "One more ques- hands and with an insane, laughing yell tion, Doctor-when swung it up and crashed it with a fear- did it happen, and ful splintering sound down on my what day is this ?" head.... "The accident oc- a 4 r s curred the day be- When I came to I was in a white - fore yesterday, and walled room, lying on a high bed. My you've been uncon- bandaged head was aching terrifically with a constant high- frequency throb. Minuteness of the re- "What happened ... Where am I ?" ceiver is seen by com- I murmured weakly. parison with the hand. for APRIL, 1947 BO Printed in the U.S.A. RADIO -CRAFT KM MI I -

..... r.x...r,..y,..,,.yr451f0:1y4,,.,w -- - 0011ftI-'r ,

TELEVISION- Does if Wad .4 Fu/upe Fo'You?

SPECIAL INVITATION TO WAR VETERANS With extensive new training facilities under the personal supervision of the famed inventor of the radio vacuum tube, Dr. Lee de Forest, we are able to accept additional applica- tions from Veterans for Television training under the G.I. Bill of Rights. For qualified men who are seriously consider - ing entering a residence school, we have a limited number of Home Study Courses which are available free of charge. Your success with this course will not only help you to de- cide your-own future in Television but will also aid us greatly in qualifying you for residence training. Send your name and address for your Eligibility Question - aire. If you qualify under the simple rules, you may start ur Home Study Television Course at once and entirely hout cost or obligation to you.

can Tele Laboratories, Inc. 5050 BROADWAY AGO 40, ILLINOIS

__. Mallory Contributionsttt to Television

Llu.lune H ry ing the in- ductance in a t manner. it ,,,,, ides Mtn djusUient of iregiencies of the ele%i,. FM, \ircraft, Amateur aid Police Bands -front ii. to 216 megacycles. Grid Bias Cell Assembly: Im- proves picture quality- by aiding low frequency response and effec- tively eliminating stray pick -up. Videocoupler: Widens frequency television sets will be as response, resulting in better picture ANTICIPATING the day when servicing of definition. -day servicing of radio sets, Mallory has long been FP 550 Capacitor: A unique dc- common as present ett I iupling and screen Ilv puss ea itor. component -. engaged in planning, designing and building television 10 Watt Vitreous Enamel Resis- tor: l sed as a voltage dropping or television circuits bleeder resistor in low voltage pm, cr The result of this foresight is shown in the typical supply. in which no less than ten different Mallory If'P 540 Capacitor: Bypass for illustrated above -circuits ertirai renteritg. *, the parts find an important place. Three of these parts -the Inductuner WP 510 Capacitor: Bypass for horizontal centering. Bias Cells of exclusive Mallory design. Videocoupler and the Grid -are WP 505 Capacitor: Bypass in c earl container for video stage to The important point about these products is that they conform eathude circuit. Filter in low right is a 1'P 135 Capacitor: standards for which Mallory is famous. Each in its own voltage supply: rRrtband$ premium les`m60 cycle true "Approved Precision Product." Each has the earmark of tlistorliou. more from Mallory components. Carbon Controls: Used as tone, quality. You expect more and- get volume and ronlrast controls. (Nut That's true, too, of these television products. shown.) *Reg. C. S. l'ut. Off. Wire Wound Controls: Used for horizontal and vertiral centering.

P.R.MALLORYLCO_Inc. VIBRATORS .ORS.. CONTROLS ... SWITCHES ... RESISTORS ... FILTER MALLORY ... RECTIFIERS ... POW ER SUPPLIES. R. U. S. Pat Off

6, INDIANA APPROVP. R. MALLORY & CO., Inc., INDIANAPOLIS