Radio-Electronics in All Its Phases Canada 30, Sil Vanl4 Xews Radio Service Edition

HUGO GERNSBACK, Editor g. o

JUN

1 9 4 7

RADIO-ELECTRONICS IN ALL ITS PHASES CANADA 30, SIL VANL4 XEWS RADIO SERVICE EDITION

JUNE Prepared by SYLVANIA ELECTRIC PRODUCTS INC., Emporium, Pa. 1947

RADIO SERVICEMEN! SYLVANIA'S COLORFUL NEW CLOCK BIG AID IN SERVICE SALES Specially Designed Famous -Make Clock Identifies Quality Stores Stocking Sylvania Tubes

Bright white face ... Fifteen -inch diameterI black numerals! Radio tube in silver e Minute and hour and black...design hands in black ... of carton in famil- unique second iar green and hand in attractive black! red! Telechron movement sealed in The words ir "RADIO oil; case in brown SERVICE" in green crinkle finish with and black. The word silver -colored rim "SYLVANIA" in iden- around face! Nominal- tifying green! ly priced at only $7.501

Once you place this big, colorful Telechron elec- your customers are being advised of the advan- tric clock -with its "Radio Service" face -in your tages of placing Sylvania "quality- controlled" window, you'll have an attractive sales aid that radio tubes in their equipment. By displaying identifies your business ... every second of the this on- the -spot sales help you're telling them you day ... as carrying the finest line of tubes made. sell these highest quality tubes. Get this wonder- Through far -reaching advertising campaigns, ful sales aid now !

ORDER FROM YOUR SYLVANIA DISTRIBUTOR or write SYLVANIA ELECTRIC PRODUCTS INC., Emporium, Pu. SYLVANIAELECTRIC MAKERS OF RA010 TUBES: CATHODE RAY TUBES; ELECTRONIC DEVICES; FLUORESCENT LAMPS. FIXTURES. WIRING DEVICES; ELECTRIC LIGHT BULBS A FREE iEssoN alLL. YOU'RE ALWAYS ` ' I'LL TRY, MARY, I'LL) II WITH RADIO--OUR SEWON T SEE WHAT I CAN OD SNOWED DILL HOW NE CO1111 WORK--WILL VOL) FIX IT? WITH IT TONIGHT MAKE GOOD PAY IN RADIO: iVE BEEN STUDYING' Al HOME WITH THE SAY, I'VE SEEN THEIR HELLO, BILL--GOT YES. JOE -- I'M NATIONAL RADIO INSTITUTE. I JUST ADS BUT I NEVERTHOUOIIT I CAN'T FIND OUT LANDED A SWELL RADIO JOB,TOO LISTEN I COULO LEARN RADIO WHAT'S WRONG A TOUGH ONE STUMPED -- BLT -- FOR THE CLICKS AS I SHORT THE GRID AT HOME TO FIX ? SINCE WHEN ARE GUESS I'LL MAKE A CONNECTIONS.,. HERE S YOUR TROUBLE I'LL MAIL f LET ME YOU A RADIO EXPERT? FOOL OF MYSELF IN THE FIRST I.F. STAGE -- I LEARNED A COUPON i, J~ - HELP YOU y WITH MARY THIS TEST BEFORE I EVEN STARTED FOR A FREE THE COURSE, FROM A LESSON RIGHT FREE LESSON THE AWAY N. R I. SENT ME

THANKS' I WAS JUST OH,BILL--IM $O GLAD YES, OUR WORRIES l'M CONVINCED NOW SOON I CAN HAVE MY YOU CERTAINLY KNOW A TINKERER A FEW I ASKED YOU TO FIX ARE OVER I HAy" THAT THE N.R- I. COURSE OWN FULL-TIME RADIO RADIO. SOUNDS AS MONTHS AGO, BEFORE OUR RADIO' IT GOT IS PRACTICAL AND REPAIR BUSINESS, OR BE GOOD AS THE DAY A GOOD JOB AN I STARTED THE N R.I. YOU STARTED THINKING THOROUGH. I'LL READY FOR A GOOD JOB I BOUGHT IT! THERE'S A BRIGIII COURSE- -BUT ABOUT RADIO AS A IN A BROADCASTING STATION, FUTURE FOR ENROLL NOW. THEN "50 -50 CAREER, AND NOW AVIATION POLICE I CAN MAKE EXTRA RADIO, "GIVES YOU'RE GOING AHEAD N RADIO METHOD A áP +. MONEY FIXING RADIO OR SOME tAi FELLOW THE PRACTICAL Ii SO FAST! RADIOS IN SPARE OTHER BUSY KNOWLEDGE AND EXUERIENCE , TIME WHILE RADIO FIELD TO BE A SUCCESSFUL LEARNING RADIO TECHNICIAN ..

You Build These and Other Radio Circuits with BIG KITS OF PARTS I SEND YOU! I will send you a Lesson on By the time you've conducted 60 sets of Experi- ments with Radio Parta I supply, made hundreds of measurements and adjustments, you'll Radio Servicing Tips FREE have valuable PRACTICAL Radio experience for a good full or part -time Radio job! TO SHOW HOW PRACTICAL IT IS TO TRAIN AT HOME FOR SUPERHETERODYNE CIRCUIT (right) Preselee- tor, oscillator- mixer -first de- GOOD JOBS IN RADIO tector, U. stage, diode detector -a .v.c. stage, audio stage. { Bring in local and distant stations on this circuit you I want to give you a copy of my build yourself! Lesson, "Getting Acquainted with Re- ceiver Servicing " -absolutely FREE I VETERANS And with it, Fil send my 64 -page illustrated book, "How to be a Success in You can get MEASURING INSTRUMENT (above) Radio," also FREE. It describes many this training in you build early in Course. Use it in practi- fascinating Radio jobs, tells how cal Radio work to make EXTRA money. N.R.I. trains you at home in spare your own home Vacuum tube multimeter, measures A.0 -, time, how you get practical experience under G. I. D.C., and R.F. volts, D.C. currents, re- with BIG HITS OF RADIO PARTS I sistance, receiver output. send. MAIL THE COUPON! Bill. Mail cou- Future for Trained Men Is Bright pon for full in Radio, Television, Electronics ' A. M. SIGNAL -GEN- It's probably easier to get started in details. ERATOR (left) build Radio now than ever before, because it yourself! Provides the Radio Repair Business is booming. amplitude - modulated Trained Radio Technicians also find neighbors' Radios in spare time while signals for test and profitable opportunities in Broadcast- still learning! From here it's a short experimental purposes. ing, Radio Manufacturing, Public Ad- step to your own full -time Radio Shop Gives valuable practice) dress work. Think of even greater op- or a good Radio job! portunities as Television. FM. and Find Out What NRI Can Do For You many new, war -developed Electronic Mail Coupon for Sample Leeson and sO/!7 devices become available. Get the facts my FREE 64 -page book. It's packed on all these opportunities. Send for with facts about Radio's opportunities V L/ SAMD EELES OR FREE FREE books now for you. Read the details about my Many Beginners Soon Make Extra Course. Read letters from men I Money In Spare Time While Learning Mr. f. E. Smith. President, Dept. 7FX trained, telling what they are doing, NATIONAL RADIO INSTITUTE. Washington 9, D. C. The day you enroll I sending See how quickly, easily you start earning. Moll me FREE. without obligation. Sample Lesson and 94 -pogo book No ! EXTRA MONEY JOB SHEI;15. You can get started. obligation Just about how to win success In Radio and Television-Electronics. (No LEARN Radio Principles from my MAIL COUPON NOW in an en- salesman will call. l'lesso wrlto plainly.) I easy -to- understand, illustrated lessons velope or paste it on a penny postal. -PRACTICE what you learn by J. E. SMITH, President, Dept. 7FX. 1 building, testing and experimenting National Radio Institute, Pioneer Age with parts I send -USE your knowl- Home Study Radio School, Washing- edge to make EXTRA money fixing ton 9, D. C. I Name I OUR 93RD YEAR OF TRAINING MEN FOR SUCCESS IN RADIO Address I

My Radio Course Includes Training in City Zone Sister I TELEVISION ELECTRONICS FREQUENCY MODULATION APPROVED FOR TRAININÇ UNDER G.I. BILL

RADIO -CRAFT for JUNE, 1947 T /nIHbOhIT CUTS TO SERVICING

"Quick, easy and efficient" ... that's how servicemen describe IRC's 11 Tap -In Shafts.tNo fiddling or fussing with shaft inserts or "build -ups" ... no money tied up in stocks of exact replacements. A smart tip of the hammer and the tapered surfaces of control and shaft lock together, forming a permanently tight attachment. In combination with, the IRC Century Line of Volume Controls, these 11 Tap -In Shafts are the logical answer for over 90% of your replacement problems. Save you time and money. Time saved means extra time for other money-making jobs ... money saved means greater profits. The latest edition of the popular IRC Volume Control Replacement Manual is now available. Contains information on nearly all models up to 1946, complete listings for the 1941 -42 sets coming in now for repair. 156 pages. 25c at your IRC Distributor. International Resistance Company, 401 N. Broad St., Philadelphia 8, Pa. In Canada: International Resistance Co., Ltd., Toronto, Licensee.

YOU'RE ON THE AIR! A sen sational new one minute spot announcement to boost service business has just been released by IRC through IRC Distributors. Listen in and cash in on this promotion !

INTERNATIONAL' ONCE COMPANY lJ Wherever the Circuit say; Q

RADIO -CRAFT for J U N E, 1947 ., '\ y ` tips right out of the horse's mouth mail coupon below The editor of The Capacitor" probably won't like being referred to as a "horse's mouth." However, that's only our way of "plugging" the scores of hot ideas for for your free servicemen that he includes in every issue of "The Capacitor." subscription to the C -D capacitor Here's a magazine that's published for servicemen only. Every month it is loaded with ideas for speeding up service procedures -for increasing store traffic - for adding new dollars to your income. Its convenient, pocket -size pages contain valuable technical data - information on the new type tubes -notes on trouble shooting. Yes, and also dozens of helpful hints that will help you to repair any radio ever made, easier, better and twice as fast. Accept "The Capacitor" with C-D's compliments. Put it to work in your shop speeding up repair jobs - building bigger profits. Don't wait! Mail coupon below NOW, so your FREE subscription will start a once! Cornell- Dubilier Electric Corp.,Dept.RC6,Soutb Plainfield, New Jersey.

TITLES OF ARTICLES IN RECENT ISSUES -These articles are typical of the ones you'll find in "The Capacitor" every month: How to Ore Audio Oscillator and Signal Generator to Simplify Tests -New Requirements of FM and Television Servicing MICA -Hum Elimination - Aligning Superbets. Think how such articles will help you -mail coupon NOW.

TRAMOL FINDS "THE CAPACITOR" OF GREAT INTEREST-Washington, D. C. service shop owner writes, "I wish to thank you for mailing me 'The Capacitor.' The special items are of particular interest because of their easy reading and their simplification of PAPER complex circuits."

FREE ADS FOR SERVICEMEN -Yes, that's right -your ad will be run absolutely ELECTROLYTIC -f Fee in The Trading Post which appears in all issues of "The Capacitor." Use this service to buy that new tester you've been wanting -to sell that spare 'scope -or to work out a swap with other servicemen.

1910 CLIP THIS COUPON -MAIL AT ONCE

CornellDubilier Electric Corporation Dept. RC -6 South Plainfield, New Jersey Please start my FREE subscription to "The Capacitor" at once.

Name

Address

I City Zone Siete L

RADIO -CRAFT for J U N E, I 9 4 7 3

THE NEW ADDITION TO OUR RADIO SCHOOL YOUR OWN OWN GENERAL RADIO COURSE SHOP The course in General Radio is designed RADIO to provide a brood foundation for careers in the technical radio field. Among the BASS, various job objectives ore Radiotelephone AWN Operator (broodcast, police, or airline), BE YOUR Radiotelegraph Operator (marine, zone police, or airline), and Rodio- Electronics Technician (industry). Success in qualifying for F.C.C. Radiotelephone or Radiotelegraph license is a requirement for graduation; therefore, on extensive study of radio theory, essential radio mathematics, and laws and regulations governing radio communications is included in preparation for operator license examinations.

Average Time to Complete Course .. . f2 Months

RADIO MAINTENANCE AND REPAIR COURSE A THOROUGH The Rodio Maintenance and Repair WITH Course offers preparation for a career' os radio receiver repairman, sound system tech- OL nician, and radio service shop operator. SOHO Accurate, up - to - the - minute knowledge 31 RADIO radio principles and practice is essential for future success in this important field of radio.

OUR CoM After a thorough introduction to redid and - FROM electrical principles, emphasis is directed to . modern troubleshooting methods, notable Radio (and its allied fields- electronics, television, radar) now looms as a major industry "signal- tracing." A section on facsimile re- frequency -modulation (FM) receivers in the United States offering a constant and ever- expanding field of wealth and opportuni- ceivers, and television sets is provided to bring the ties. Each new points the way toward further improvements and an increasing development repairman up -to -dote on recent develop- demand for men and women, specialized in this field. ments. A wide ronge of topics is covered in this course, all of which are important' to repairman. The Radio courses offered by the. Tyler Commercial College are highly specialized to the modern

enable you to enter many branches of radio, both as your vocation or your profession. Average Time to Complete Course .. . The present courses listed represent a partial list of the extensive and complete training 10 Months offered by the Tyler Commercial College who have had over 30 years experience in the Radio Training Field.

They invite you to examine the content of their catalogue and determine for yourself send /44 q, how radio training at Tyler Commercial College will enable you to find your own place in one of the many interesting and profitable jobs in the vast radio industry.

For full details and catalogue regarding this unique school, write to The Tyler Commercial COLLEGE College, Radio Department, RC, IA 115 South College, Tyler, Texas. COMMERCIAL Attach this to your letter head TYLER T exas or card. Tyler, MAIL TODAS' South College 115 APPROVED BY A STATE APPROVED VETERANS ADMINISTRATION INSTITUTION

4 RADIO -CRAFT for JUNE, 1947 Like having an EXTRA MAN in your shop

Photo of Dave Krantz, President of PRSMA, Philadelphia, using PHOTOFACT FOLDERS.

PHOTOFACT FOLDERS

HELP YOU EARN MORE MONEY. . code &dd acut 9$ a dart'

"Like having an extra man in my record changers, recorders, communi- shop" . . "The kind of 'specialist' cations systems and power amplifiers I need" . that's what hundreds of as they reach the market. PHOTO- VOLUME 1, containing first ten sets of radio servicemen say about PHOTOFACT FOLDERS come to you PHOTOFACT FOLDERS FACT FOLDERS. Yet this indispen- in de luxe in sets of 30 to SO at only $1.50 per binder, $18.39.Individual seta Nos. l to 10, sable "hired help "actually costs less $1.50 each. De Luxe Binder alone, $3.39. set. Low as this price is, it also includes than 9 cents a day! membership in the Howard W. Sams COMPLETE Here are the straight facts: PHOTO- Institute. FACT FOLDERS offer the best in- Everything you need in one handy, unified formation ever prepared for radio Set No. 19 will be ready for mailing form --large schematics, pictorials keyed to servicemen -complete, accurate, up- May 10th. Set No. 20 on May 25th. parts lists and alignment data, complete to- the -minute, easy to use. They save Sets Nos. 11 to 18 inclusive, also listings of parts values and replacements, you hours of time and effort because priced at $1.50 each, are available for alignment, stage gain, circuit voltage and they place at your fingertips ALL the immediate order. resistance analysis, coil resistances, dial cord information you need to do a better Actually, PHOTOFACT FOLDERS stringing, disassembly instructions, record job. And that means you can earn cost you nothing since they pay for changer analysis and repair. MORE MONEY. themselves again and again. They're ACCURATE The information in PHOTOFACT ready to help you now -at the most FOLDERS is right because it is based difficult time in servicing history. See All sets are actually taken apart and an- on actual analysis of sample sets your distributor or write us today. In alyzed by experts in the Sams laborato- right in our own laboratories. It is Canada, address A. C. Simmonds es ries. Every part is measured, tested and complete and current, too, because Sons, 301 King Street East, Toronto, triple- checked for accuracy. All data is it covers all radios, phonographs, Ontario. original. This means the data you get is right. *Trade Mark Reg. CORRECT PHOTOFACT FOLDERS are issued twice monthly, as the new receivers come off pro- HOWARD & CO., INC. duction lines. You don't have to wait for in- W. formation. As receiver changes are made, you SAMS get correction and addition sheets for your 2924 EAST WASHINGTON STREET, INDIANAPOLIS 6, INDIANA files. Your data is always up to the minute. READY TO USE All diagrams and pictures are coded to num- bered parts lists. Everything is positively identified for fast work. All folders are set up PHOTOFACT SERVICE in uniform, easy -to- follow style: big type, big " ne service that pays fo- itseit over ord over again" illustrations -no hunting, guessing or eye strain -no more loss of time and temper.

RADIO -CRAFT for JUNE, 1947 S Frequency-Modulation radio reception is virtually free from natural static -even thunderstorms do not interrupt.

FM Radio- another world in listening pleasure!

It's as though the orchestra were right FM; are constantly applied to all RCA in the room with you - and the room products, so that each one is always at suspended in the silence of space. When the top of its field. you listen to music over RCA Victor And when you buy anything bearing FM, you hear FM at its finest. the RCA or RCA Victor name - whether Natural static interference ordinarily it's a radio (standard, or FM, or both), caused by thunderstorms does not mar a television reeeiver, Viptrola radio - FM radio reception. You are in a differ- phonograph, a phonograph record or a ent, new world of utter quiet where you radio tube, you know you are getting hear only the lifelike music. Moreover, one of the finest of its kind that science you enjoy the same perfect reception has yet achieved. With the new RCA Victor AM- FM sets you'll hear FM radio -and day or night. standard AM radio too, at their Radio Corporation of America, RCA Building, The vast experience, research and finest. Ask your RCA Victor dealer Radio City, New York 20 ... Listen to The for a demonstration of the fine new skills at - RCA Laboratories, such as RCA Victor Show, Sundays, 2:00 P.M., East- Crestwood series of Victrola AM- aided in the development of RCA Victor ern Time, over NBC. - victrolo" T.M. Reg. U. S. Pot. Oft. FM radio-phonographs.

RADIO CORPORATION of AMERICA Vpir 6 RADIO -CRAFT for JUNE 1947 Haw! An Amazing Opportunity to -1 LEAR RADIO:tM, "+ I SEND YOU 8 BIG KITS OF RADIO PARTS

my SUPER_ HETERODYNE 1 Ind a COMPLETE 6 TUBE RECEIVER

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

BUILD HLEAW rAR"a CIRCUITS! TEST! REPAIR! YOU DO OVER 175 INSTRUCTIVE EXPERIMENTS :er,- iì11

YOU BUILD MS USEFUL TEST fQ U/AMENT!

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 check 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 TOUR OWN ... OR A GOOD RADIO JOB hands on o big 6 -Tube Superheterodyne Receiver. You'll find ou¡ how to get and do neighborhood Soldering. wiring, connect. And, believe rne, when you get busy with real Radio repair jobs far nice profits and rich esperi ing Radio ports . . building circuits you can't beat Radio Parts - 8 big Kits of them you really ence while learning. This sort of work can easily - - this method of learning. LEARN Radio and learn it RIGHTI You get the pave the way for a Rodio Service business of your When you construct this practical stuff you need to be own. But with Sprayberry Training, you're not Rectifier and Filter, Resis useful in Radio, and for and limited. You mn swing into Condenser Tester. that's what i! takes to make money. You don't any one of the swiftly etc., you get a really prac- expanding branches of Radio - tical slant on Radio. have to worry about what to do with these 8 Kits Electronics INCLUDING Radio, of Ports. Step by step, I show you how to build Television, FM, Radar, Ind., - circuits, test, experiment, troubleshoot. And you trial Electronics. Be wise' You'll get valuable es parlance and practice don't reed any previous experience. The Spray- Decide now to become building this Signal VIII berry Course starts right a fully qualified EE rg ,E, Generator and multi of the beginning of purpose Tester. RADIO - ELECTRONI- Radio! You can't get lost! Simplified lessons, El Makes a breeze out CIAN. Get full details coupled with real "Shop" practice, makes every TE of fixing Radios and about any Training at you don't have to subject plain and easy to understand and remember. spend money on once! Mail coupon be- ready - Soon after you begin Sprayberry outside, Training, I'll low for my 2 big FREE made equipment. sand you my sensational BUSINESS BUILDERS. Books. RUSH ÏÓUPON! CET SPRAYBERRY ACADEMY OF RADIO THESE VALUABLE F. L. Sprayberry, President, Room 2087, Pueblo, Colorado I Please rush my FREE copies of "How to MAKk MONEY in RADIO, I ELECTRONICS and TELEVISION," and "HOW to READ RADIO 1 FREE 8001a I DIAGRAMS and SYMBOLS." "Haw to Road Rodio Diagrams and Symbol." Here's a valuable and wonderfully complete new book which explains in simple English how to read and under. IName Age , stand any Rodio Set Diagram. Includes translation of all Radio symbols. Send for this volume at once. It's free! Address ' Along with it, I will send you another Big Free City book describing in detail my Rodio- I State I Electronic Training. (Mail in envelope or paste on penny postcard) II I------BII--- lMI -B. -J RADIO -CRAFT for JUNE, 1947 7 B -19 Radio Receiving and Transmitting equipment. Has 3 different sets -made for SPECIAL ITEMS U. S. tanks. AN /PRS I Mine Detectors for detecting *1. Transmitter and Receiver 2 to 8 Mc. both and non metallic materials. #2. 235 Me. Transceiver. metallic Intercommunication /ffm//!%Cdtkas Indication both aural and visual, slightly *3. system - our used $17.95 price for the B -10 Complete.... $78.50 Power Output Tuning Unit, Ideal basis for E.C O. rig. C'tV 35 Wyatt. MICROWAVE SPECIALS Has ow., final & ant. loading tanks, for Phone 25 Watts TCE or GP -7 in the following frequencies A. -950 to 800 KCs; B.-800 to 1500 Km: RM.29B Remote Control Units to control C-1500 to 3000 KCs: D.- -3000 to 4525 transmitters. Can be used for telephone KCs; E-4525 to 6500 KCs. Plug in units intercom work. lias bell ringer. Two 1131- app: 11" all sides. Contains all coils. eta.. 29 or similar It 51's In combination with for these frequencies. Order by frequency. two handsets Like regular telephone. IO State your lst and 2nd choice ...... $2.75 Total 521.00 Sonar Sound Detection Unit. Couple this underwater sound detector to an audio amplifier. You can hear a school of 0fi7pthí SCR 610 FM Transmitter- Receiver. Fro - MICROWAVE PLUMBING within a 15 mile area. The Rochelle pul( queney range 27 to 38 11c. Crystal Con- crystal used in this unit 1000 trolled. Operates on 6 or 12 V DC or Slat- more sensitive than quarts.is 116. tery input. Complete to last detall Used Three Centimeters cable supplied. SD -I app: 18' condition $69.50 Wavemeter (Maguire Industries #1539TFX -21GA) 8 centimeter Visors for 5 Inch scopes cavity. Vernier Driven Dial 820.00 Tube shields for 2 API Condensers Wave guide 15° bend 16" long cover to cover 3.00 Sliver button mica condensers. 175 alW Wave guide 30° bend 10" long choke to cover 3.00 185 mmf. ea. Pyranols Dykanols - Etc. "T" Section 5.50 Lots of 100 4.60 1 mf 300 v4e $ .20 Silver button mica condensers, 500 mml. 2 mf 300 vae .25 Wave guide 90° bend E Plane 18" long 5.50 121/2" 4.00 Each .10 4 mf 300 vac .30 Wave guide 180° bend with pressurizing nipple Lots of 100 9.50 mf 00 arde .50 Wave guide "S" curve 18" long cover to choke 3.50 e.5 ml 400 vac 1.05 B -29 Computer -Amplifier contains 8 6SN74, SSO .25 Wave guide "S" curve S" long cover to choke 2.50 .25 mf 5 Noas, 8 relays. Completely wired. and de Wave guide 21/2 ft. long 180° bend choke to cover 5.95 in brand new condition 9.95 .85 mf Boo vac .25 4.00 1 ml 600 vae .30 Section Rigid coax 18" 58 ohm Z has 14 wave section Mast Base -Flexible. 18" long. Extreme*. .1..1 mf 7000 ac O.E. PYr 2.00 Pick up loop with adjustable tuning section used in duplexer 1.50 2 ml 600 vde .35 rugged construction. Low capacitance 96.66 mfd 600 V. .60 Brass choke Opening 1" x .60 High Voltage cup shaped insulators 3" 10 rd 600 V. .85 5 feet 3 cm wave guide per foot 1.95 diameter lit on both aides of mounting sur- 1 mf 1000 vdc .7s .1 mf 1000 V .25 face 92.65 2 mf 1000 vac .89 Ten Centimeters Phasing condenser - 4 section. Westeen 1 mf 1500 vde .95 .4 mf 1500 vae .15 Coax rotary joint with deck mounting 8.00 Electric D 150739 (List $20) $2.00 2 ml 660 a /1000 .85 Coax coax s/4" coax magnetron coupler 2.50 Headphones. Leather covered band -8.000 mf 1500 vac 1.20 coupler connects 9/16" to impedance with 6 ft. cord and detachable 1 mf 2000 vac 1 On Standing wave detector Coax 68 ohm 5.00 rubber cushions. Brand new $1.95 Send Load (Dummy Antenna) Wave Guide section with cooling Used -ln good condition 31.00 fins. App: 23" high 35.00 Dipole Antenna (440 MC.) Made for the Tube Special Wave Guide to Rigid Coax at right angle. App: 10" high. Gold ARN -1 F.M. Beautiful aircraft Tubo Your Tube Your altimeter. Type Cost Type Cost plated has mounting flange 25.00 construction. Easily mounted and has coax 2AP! 53.75 837 51.35 10 cm Wave guide -I6 foot lengths -per foot 2.00 connector $2.25 36P1 872* 2.44 3,95 3124 3.95 Signal Generator I -138 made by Western Electric. 2700 to 8000 War Department Technical Manual for 3FP7 3.50 3045 5.95 MC. Operates on 115 V /60 cycles. Regulated power supply and Radio Seta SCR 508 -SCR 528 and 5011 38.1 .95 70SÁ 6.75 meter 75.00 538. 239 Pages of Schematics, Maintenance, 58P4 1.95 341.9 -WE 30.00 has output instructions and theory only 50e 5CP1 4.95 861 39.00 5FP7 4.25 TL 8.00 Selsyn Motors- operate on 115 volts 60 304 1.25 Centimeter New Sockets for SCP1, S1IP1. 35P1, 705A, cycles. $7.75 pair 829 95 ea. "T" Section Choke to cover 4.50 Synchro capacitor to go with Seisms. 10- Mitred elbow-cover to cover 3.50 10.10 mfd. @ 90 V. G.E. Mark 1 Mod. 2 Flexible section 1" -choke to choke 3.00 Type 3C. Greatly improves performance of TRANSFORMERS synchro system $2.30 Combination pair of selsyns and synehro special price Pulse MAGNETRONS - KLYSTRONS, ETC. capacitor $9.50 High Voltage 3131 (one CM) listed at $95.00. Our price $20.00 RELAYS! 2132 Magnetron 110 Cm) 250 KW Peak Pulse Power. Technical data sup- Power Supply plied. Brand new in original packing. Listed at $200. Our price 25.00 720 Magnetron -2760 MC. -Value $200. Our price 20.00 Here are values 2126 Magnetron (10 Cm) 25.00 you'll Audio Magnets for the above magnetrons 12.00 2138 Magnetron (3245 -3263 Mc.) Complete with magnet 37.50 never beat 723 AB (9 Cm) Teohnleal data supplied. Listed at $38 7.75 Raytheon Pulse 4298 E. Klystron-2K25/ TIME DELAY CRAMER- clockwork relay. Transformer UX Sockets for 723 AB Klystron Ea. .35 115V/60 cycle. 10 ante rating ...... $2.95 Pri: 4 KV. @ 1 microsecond: secondary: McNally (10 Cm) with Cavity 15.03 18 KV @ 16 amps. Filament prl: 115 -707B Edison tube type. sealed thermal relay, 45 External Cavity for 707B 3.60 to value V/400 cycles $15 Thermistor Beads -used in microwave measurements. either 1)107332 or 60 second delay. $10 $2.95 W.E. HI Volt Input pulse transformer 1)170396 (W.E.) .95 Struthers Dunn 125 V. DC. 3 amp Type *D169271 $9.95 Thermistors- Button type. either D168391 or 168391 or 1/168392 (WE.) .95 ADBT 8. A rugged relay mounted on bake - Di- Magnetron Stabilizer (3 CM) Assembly Is made up of a 3 CM magnet and lito base. DPST $1.50 G.E. Radar pulse transformer K2731 22.50 ameter app. 11 ". Vertical 000iirtg fins $19.50 magnetron stabilizer cavity. Cinaudagraph Typo UC 210 G.E. Time Delay Relay 115V /60 Cycle. 10 amp rating Type CR I contact Prim: 117 V. /60 Cycle. Secondary: 500- 2790. SPST open; 1 contact DPDT doled $2.10 900-0- 400.500 @ 250 ma. and 6.3 V. @ pulse IFF Equipment. Includes G.E. Underload CR2810- 1265. 1.5 amps. Dimensions 5" x 4" x 6" epp. Transmitter -Receiver IBC 1267 and relay Type $6.95 Operates High amperage. Sturdy construction on Power Supply RA 105A. -loch bakclite base Prim: 117 V /60 Cycle -3.8 amp. Sec- on 117V/60 cycles. Frequency 157 h $1.50 ondary; 980 V. @ 950 ma. no C. T. Di- to 187 Me. Can be used as a low Telephone type DPST: I closed, 1 open. mensions app. 514" x 6" x 5" $4.95 ea.. paver radar unit as is if coupled Contact rating 5 amps at 50 V. Coil rat- $9.00 pr. to a cathode ray tube. Or very ing 3.5 ma $1.05 Prim: 117 V /60 cycle. Sec. 6.3 V. @ 9 easily modified for work on the 2 Leach DPST 1155700 c $1.39 amps. center tapped; 6.3 V. @ 2.2 Aine: meter band. Has 5 stagger tuned and 6.3 V @ 2.2 amps. Three secondaries. 1F stages which makes It easily 6 Voit AC DPDT Dunce $1.50 app. 4" x 41" a 5" $3.75 adaptable for FM or Television 6 Volt AC DPST Dunce $1.20 Filament Transformer Raytheon 517X6839. work. The power supply furnishes DC Primary 115 V /60 cycles. Secondary *I all operating voltages. These two Relays V. units in excellent condition fit Leath. Kurman, Advance and other well - -5 T. @ 5.5 amps. Secondary #2-5 which also @ 5.5 amps. Tested for 29,000 Volts in- into a metal rack is known makes sulation $12.95 provided. O.C. 12,500. Our special price RC148 $59.50 SPST. 12 or 28 Volts. ea 50 2KVA Transformer and choke primary DPDT, 12 or 28 Volts- ea 60 110V /60 Cycles. Single phase. Output TPTT, 12 or 28 Volts, ea 70 17.000 volts @ 144 ma. Choke 4,000 Hy SO RADAR Discounts on lots -100 10°/a 1000, 15;'0 @ 0 current. DCR 4500 ohms. Dimensions 5000, 20% 26" x 29' x 13 ". Amertran $74.50 10 Centimeters. Extensively used by the U. S. Nary for search and blind naviga- politico indicator continuously draws a map of surrounding area an unusual AC tion. Plan Here's transformer special! Range from 4 to 80 miles. New in original crates. including all spare part as In, DC out. A rectifier unit is incorporated Mfg. Co. for installation. Sparo will many supplied to the U. S. Navy by Raytheon ports, MICRO WAVE inside the transformer. You find in many cases preside 4 replacements for each part. moneysaving uses for this rectifying trans- alone former. Made by Federal Tel. *RA 7067 -1. Write for our special low pries ANTENNAS /50 to 62 cycles. Secondary: Primary 117V SO Radar, used. Includes Transmitter- Receiver. Indicator. Motor Generator set. Designed for your directional and experi- 62 V DC @ 3.5 amps. Use it with a EILAND NEW antenna assembly mental work. rhewtat to run DC unite directly from Echo box, section of 10 CM wave guide and $500 your house line. A buy at $3.95 Separate units which make up the SO Radar. SO Antenna assembly (10 Cm) complete in antenna assembly including drive mech- 115 Secondaries: 470V. Them are used but excellent condition. Volt /60 cycle pri.- $85 anism. RF' radiating assembly. parabolic CT @ 60 ma and 6.3 V. and 5 V. $1.50 Motor Generator set Contains the magnetron. the RV assembly. and tho reflector. 24" diameter and mime. BRAND 6 Henry choke ma match above 65c TrnnsmitterReceiver unit. NEW. original -60 -to Revolver IF strip. All tubes included SI50 In crate $90 Utah -small Blocking oscillator type trans- Used, and in good condition $45 former-either 9218 or 9308 ea. 75c Indicator Unit Contains the Plan Position indicator tube. video amplifier and - $100 TDY Antenna includes Parabola, hood. A special buy for you If you can use 400 all video display controls our driving mechanism 30° brans! In original cycle traneformers. We have most of crates $100 small 400 cycle transformers on sale at SEND FOR OUR LATEST FLYER sizes proportionately low. 50e each, Largo All merchandise guaranteed. Mail orders promptly filled. All priees F.O.B. New Parabolic Reflector-mado of aluminum Send un your approximate voltage require - or Shipping charges sent C.O.D. fill your order. York City. Send Money Order Check. ribs. By "Rudd ". Used for 10 Cm. mirk. monts. Well Dimensions app: 41 x 3'. Has a mount- Audio Transformers, modulators, etc ing neck for insertion on piping- ratable. Modulation Transformer, 807 to pair of Ideal for micro-wave relay work. In origi- 807s $1.00 COMMUNICATIONS nal crates $100 Line to Volte coil transformer. Pri: 600 Complete and ohms; sec: 6 ohms. SCR -ß518 Radar altimeter. *CRP 90448 new! In original crate. Contains trans- Sub Sig. Type $1.00 EQUIPMENT CO. mitter, receiver, antennas and 3" calibrat- UTC TYPO #83718 -Primary 600 ohms CT. Secondaries: 4000 ohms and 150 ohms. 131 -C Liberty St., WH 4 -7658, New York City 7, N. Y. ed Indicator. 20,000 ft. range. Ready for Each only 50e complete installation $279

B RADIO -CRAFT for JUNE, 1947 I` ELECTRONICS7 Pate

O WITH THE HELP OF V7 o O ~ A EIGHT Big Kits of Actual "Learn -by- Doing" Radio y Parts and Assemblies with which you make 133 fascinat- a¿/ ing SHOP METHOD EXPERIMENTS in your own home! F OQ- PF R E N Imagine building 7 different Radio Receivers that operate! c F /VING B A 16 mm Home Movie Projector and Twelve Reels of. e; "Learn -by- Seeing" Home Movie Films ... for picture. 110 PREVIOUS RADIO S`pe< clear, fast understanding of Radio Fundamentals! OR ELECTRICAL 1 ßee iobe C ' Modern, well-illustrated, Loose -leaf Les- EXPERIENCE NECESSARY i4e 14°. sons, prepared in clear, simple, understand- DeForest's Training, Inc. provides el Itece ,ed every major home study aid to help you oe°cy able language ... to guide you throughout learn Radio-Electronics rapidly and thor- S FeA t oughly ... to give you the experience and your training! confidence needed for a responsible, Good - 3 ßscs,vg Pay Job, or to Start a Business of Your Own! 'Pc ,°ò Bere is a REAL Opportunity field for YOU e THEN GET THE HELP OP . when you are a trained Radio-Electronics S"° oòy° man /Just think of the tremendously exciting A t°°st ets< pe OUR EFFECTIVE future ahead of FM Radio, Aviation and p Re e eth òy Broadcast Radio, Sound Motion Picture Equip- 5 sae EMPLOYMENT ment, Servicing and Sales of Radio Equipment, JQehtet°9 y .: etc. Put yourself in this picture ... See how you be S SERVICE can benefit from a PRACTICAL training in this GoßE fascinating work! Think, too, of the coming possi- *col' bilities ahead of Radar, Facsimile and Television. 5-0iti Send TODAY for the interesting, opportunity - tv.%)S revealing book, "Victory for You!' See how others Rprobably no more talented or ambitious than you, . o ave advanced in earning power after o ó this training ... how YOU can do it tool Mail the coupon NOW! VETERANS! NátxQGE144 N N Big things aro happen- %o.E 110-E ing at DeForeat's Train- fp5C PA) YOU USE ing, Inc. for veterans! it See how you can prepare 18 MM "LEARN -BY- SEEING" yourself WITHOUT MOVIE COST for a GOOD JOB sr- B17 -t_ - _ _. tr MOVIES or a BUSINESS OF _ PROJECTOR 1 YOUR OWN in the vast E. B. DEVRY, President DeFOREST'S TRAINING, INC. 2535 -41 North Ashland Ave., Dept. RC -D -6 DEFORESTS,. TRAINING, INC. INCLUDES Chicago 14, Illinois, U.S.A. INSTRUCTION IN MOTION PICTURE FOR YOU!" BOOK, showing how may SOUND EQUIPMENT, FM RADIO AND Send FREE "VICTORY I TELEVISION ... RESIDENTIAL TRAIN- make my start in Radio Electronics. . ING IN OUR MODERN CHICAGO LAB- ORATORIES ALSO AVAILABLE -ASK US Name_ Age 1 FOR INFORMATION! Address__ Apt I TRAINING, INC. City Zone -Sta e If under 16, check here If a discharged Veteran of DeFOREST'S CHICAGO 14, ILLINOIS for special information. World War IL, check here. RADIO -CRAFT for JUNE, 1947 9 JUNE - 1947 1[A1/111

Editorial; FM and Altitude by Hugo Gernsback 17 CRAFT Radio -Electronics Monthly Review 18, 19 Radio Thirty -five Years Ago 75 AND POPULAR ELECTRONICS Incorporating WAVE CRAFT TELEVISION NEWS Electronics RADIO i TELEVISION

Color Television, Part I by H. W. Secor 20 HUGO GERNSBACK Pioneer Atom Splitter (Cover Feature) Y2 Editor-in-Chief "Shooting Stars" Tracked by Radio by S. R. Winters 26 FRED SHUNAMAN, Managing Antenna Editor Principles, Part VII -Parabolic Reflectors as Antennas by Jordan McQuay 27 Television for Today, Part Problems of the -Ray Tube XIII- Cathode by Milton S. Kiver 36 M. HARVEY GERNSBACK, Consulting Editor

ROBERT F. SCOTT, W2PWG, Amateur Radio Technical Editor

V.F.O. I. Exciter or Transmitter, Part I- Variable Frequency Oscillators by I. Queen 30 QUEEN, W2OUX,Editorial Associate

ELMER FULLER, Shortwave Editor Servicing ANGIE PASCALE, Production Manager Noise Elimination by Jack King. .29 Demonstration Transmitters by Harold McDuff & George Pyle 35 G. ALIQUO, Circulation Manager Radio Data Sheet 347 (Motorola Auto Radio 1946 CR -6) 38 JOHN J. LAMSON, Advertising Director Sound ALFRED STERN, Promotion Manager A Small Recording Studio, Part IV- Operating the Recording Equipment, In A Future Issue: Speed, Needle and Record Cut Considerations by J. C. Hoedley 32 V.F.O. EXCITER -TRANSMITTER BUILD YOUR OWN DYNAMIC Test Instruments PHONOGRAPH PICKUP USE FOR OLD TUBE Intermittent Alarm ... by J. Jacobson 34 CHECKER - on THE COVER: Construction

' New Subminiature Printed Circuits 24

Battery Superhet Uses Three Tubes by William Hedrich 31

Departments

Transatlantic News by Major Ralph W. Hallows 33 Radio -Electronic Circuits 42 Try This One! 46 Technotes 48 Question Blìx 50 Dr. Enrico Fermi, pioneer New Radio -Electronic Devices 94 research worker in atomic fission, adjusts controls New Radio -Electronic Patents by I. Queen 54 of el e c t r o n i c equipment World -Wide Station List Edited by Elmer R. Fuller 60 in the Argonne laboratory. Communications 76 Chromatone by Alex Schomburg from Book Reviews 80 University of Chicago Photograph.

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., San Francisco 4, Tel. Garfield 2481. Calif. RADIO -CRAFT, June, 1947, Volume XVIII, No. 9. Published Monthly on 28th of month preceding data of iisue. 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; for years; $7.50 $5.00 two 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 thdse 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: Publishing Great Britain: Atlas and Distributing Co., Ltd., 18 Bride Lane, Fleet St., London E.C.4. Australia: McGill's Agency 179 Elizabeth Street, Melbourne. Franca: Brentano's, 37 Avenue de l'Opera, Pans 2e. H olland: Technisch Bureau Van Baerle, Bemelmens & Heemsteedsche, 124, Heemstede. Greece: International Co., Dreef Book & News Agency, 17 Amerikis Street, Athens. So. Africa: Central News Agency, Ltd., Cor. Rissik & Commissioner Sts. Johannesburg; 112 Long Street, Capetown; 369 Smith Street, Durban, Natal. Universal Book Agency, 70 Harrison Street, Johannesburg. Middle East: Steimahky Middle East Agency, Jaffa Road, Jerusalem. India: Magazines Distributors, 5 Bombay Mutual Annexe, Gunbow Street, Fort, Bombay I.

IO MAKE MORE MONEY

OFT rHFSF28eG aooNS You men already in Radio know how great the demand is for trained, experienced servicemen, op- Here's Just a Few of the eratore and technicians. You know how fast the Interesting Facts You Learn how important it is to keep with the FREE MANUAL. PREtI field is growing and up with developments -F.M. Receivers, Electronics I. Routine for diagnosing Radio and Television. You know, too, a .fellow cannot Troubles. much about any industry for REAL SUC- 2. Preliminary Inspection of Re- learn too ceivers. CESS. Whether you have experience or are merely 3. How to Check Power Supply. INTERESTED in radio as an amateur, you must 4. How to Identify Various Stages OPPORTUNITY of Receiver. recognize the WONDERFUL 5. How to Trace the Circuit and right within your grasp to cash In ón your natural Prepare Skeleton Diagram. abilities. Make them pay dividends. Gct into the C. How to Test and Measure Volt. Be F.M. ages. EXPERT RADIO SERVICE FIELD. an 7. How to Test Speaker In Audio and TELEVISION specialist -OWN A BUSINESS Stages. OF YOUR OWN, if you prefer. Fill out and mail 8. How to Test Detector. I.F., R.F.. and Mixer Stages. the coupon below for all the details of our plan. 9. Complete Reference table for Q u i c k l y Locating Receiver Get the Latest Inside Information Short Troubles. SCHOOLS; Cuts -Trade Secrets by ATM. MAL

SHOP METHOD HOME TRAINING PROM A REAL ESTABLISHED RESIDENT SCHOOL Ne,. the f moue National Schools brings its exclusive Shop-Method of training rig ht into your own home. You can learn the most up -to -date, approved projects, systems and circuits step by step in your spare time. This -mss ,4' is the sound and practical training you want and need-the de. of experienced instructors working with thou- P-pvelopment¡r- sands of students right in shops. NEW F.M. broadcast - studios and experimental laboratories of NA- TIONAL SCHOOLS-one of the most advanced trade educational centers in the world.

VETERANS LEARN BY DOING If you qualify for Work with Real training under G. I. Bill, Experimental Equipment check the coupon for a Furnished without Extra Cost Special Bulletin. as Part of Your National Training Experience is the best teacher. You learn by experience with the exclusive National Shop - Be Sure Of Your Success And Security After the War, Method of Home Training. In the course of your Coupon and study you actually build various types of receivers Don't let your post -war ambitions lag. Don't let YOUR future depend prove of others. Build a career for yourself. Never In all history has the return- -a powerful superheterodyne, a signal generator, to ing an audio oscillator and others -You make tests and serviceman, or war work_r been confronted with such a great future yourself what if he roaches out and grasps It NOW. here is a new world opening before conduct experiments that show you the why and you. Get reedy now while you are still in uniform -wh110 you are on your how of things. You understand what makes the YOU can do war job. Then you can soon step into an essential. well Paid position or, various elements of electronics operate because you in RADIO! with little ap:tal, GET INTO BUSINESS FOR YOURSELF. It isn't a see them you. only do you bit too som to start now. Radio men are vitally needed. Fin out and mail actually work for Not the coupon immediately and examine the NATIONAL SHOP METHOD gain marvelous experience by this method of learn- HOME TRAINING COURSE carefully, without obligation. ing but you receive valuable equipment you will use on the job in the practice of your profession as an electronics expert. Mail the coupon and learn what NATIONAL SCHOOLS this means to you. LOS ANGELES 37, CALIFORNIA 857.1905 L i1ll A4(iirY Il4ÿi MAIL OPPORTUNITY COUPON FOR QUICK ACTION FREE LESSON /NCII/DEP (Mail onlrein lste National Schools, Dept. 6-RC n Ex mine the exclusive National Shop Method f Horne Training. 4000 South Figueroa Street, Los Angeles 37, California. See for yourself hew d and prortical it is. Be convinced that can leant Radio, Electronics, Teleeyvisionulckly and easily in Mall me FREE the two books mentioned in your ad, Ineluding a sample lesson of your course. your You This are 1 understand no salesman will call on me. FREE. Fill tout the immediately while are thinking aboiutyit and drop it in the mnli et mice. tell of thetmarvelousonnew system of trainingin dio. Electhetronicscomplete and Teloo-- NAME ACE Tlaion. Least tha facts of this exclusive ehop.methed of home training. See for yourself! DvCmE FOR YOURSELFI This ta the MODERN SYSTEM OF TRAINING: It tches th0 Id progress constantly being made in Radio. Teievlalon andElectOnlra It in ADDRESS TIME. TESTED. too, National Schools ham been training for more than of century. it is tae very same training Mat has helped thousands to pay and greater opportunity. CITY 'STATE You owe it to yourself-your future-to read the book "Your FuWtp In D Cheek here if Vete of World War Radio. Electronics and Television-FREE to you when you send N the omtpmt. . rr on 'RADIO -CRAFT for JUNE, I947 THIS EQUIPMENT HAS BEEN REMOVED FROM SURPLUS AIRCRAFT -AND IS SOLD AS USED

AN /ART -13 COLLINS AUTOTUNE TRANSMITTER A modern. compact, lightweight. high -powered trans.

mister Foe frequency range 2.18 1 Mc on any of Its 11 auto tune crystal controlled or master oscillator channels. December Radio News pees de. tails for converting 24 V. DC operation to 117 V AC. These units removed from planes. Checked and guaranteed. Weight. 67 lbs. Price $134.50

NAVY-CRV-46151 AIRCRAFT RADIO RECEIVER

Four bands, including broadcast 1195.9.050 KC 1 Circuit is six -tube superheterodyne with mechanl cal band change or remote operated electrical band change. Remore band change and tuning controls Included. making this set readily adaptable to mobile ham use Powered Iron self-contained 24 V. DC dynamotor. The sets are complete with tubes. mounting rack and remote controls. Price. Including Cou_.._..

On orders less than $10.00 allow additional charge of 25d to cover handling.

BC-433 ADF RECEIVER

Three bands. 200 to 1750 KC. Complete with 17 tubes required and remote control This see Is Ideal for conversion to home broadcast receiver, addition to ham shack, etc. Reportedly sold for about $2.000.00 when brand new

ARC-4 TRANSMITTER and RECEIVER

Operates any of its 4 predetermined crystal controlled frequencies in the range of 140 MC. Complete with tubes. remote control. junction box, shock mounting base and connecting plugs. This unit is ideal for amateur

UHF or mobiletelephot . Operates from self- contained 24 V DC dynamotor. 12 V available upon request.

Price. as described. Including Cose $39.75

12 RADIO -CRAFT for JUNE, 1947

® .:N t America's Next Gßcgrpt Industry?

U. A. Sanabria Dr. Lee deForest The Men Who Direct r, i, American Television

Billboard Announcing Telecasts of The instructional quality of training is under Boll in Chicago Games the constant personal supervision of two internationally known engineers, Mr. U. A. Today, RIGHT NOW, clear and bright Sanabria, President and Founder of American pictures of great sports events, as well as Television, Inc. and Dr. Lee deForest, the other equally interesting programs, arc being telecast for the enjoyment of thou- famed inventor of the radio tube. sands. Television stations in New York, Chicago, Philadelphia, Washington, De- troit, St. Louis and Los Angeles are already operating on regular schedules. Construe- Lion has started in several other centers and it Is believed that practically every major FREE PRE- ENTRANCE COURSE city in the country will have this wonderful A Short Home Study TclevisionCourse is service before the end of 1948. available to qualified war veterans who are considering residence training. This Who will build, maintain, and operate the any charge or obliga- new telecast stations? Who will design, course is free of tion. Your success with it will help you produce, install and service the receivers? to learn your own abilities in television. It will also aid us greatly in qualifying Men Must Be Trained for you for residence training. Your accep- These New Professions tance of the Home Study course in no way obligates you to enter our residence Alert young men with an ambition to grow school. So we urge you to take advan- with television are training now in the tage at once of the very unusual oppor- greatly enlarged instruction laboratories tunity it offers. of American Television, Inc. A wide choice of courses available. Advanced methods and latest obtainable equipment used. Approved for Veteran Training Under G. 1. Bill of Rights

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ADDRESS

CITY ZONE STATF I am a veteran J RADIO -CRAFT for JUNE, 1947 13 Own Start Your SHOP Choose one of these piO gERVICE 3 GREAT NEW DEALS RA includes TEST EQUIPMENT, TUBES, PARTS, TOOLS

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vi RADIART AERIALS PHONO PICKUP CRYSTALS 7eeztif4JLLGtP.Ilte Quality leader The Recognized by Standard types -Set Manufectwera dose -eut \ everyone Admiralty brass rods - Triple plated Permanently rattle roll Guaranteed \ ; %flcartwte proof // Static muffler ball Polye- Webster F2- Replaces L26.L40. thelene insulated HI Q lead with pro - TEST INSTRUMENTS teetivo vinylite covering Supplied L70 etc. -pin type terminals -1 os. pressure -1 volt output -5000 with single pin (Motorola) connector 149 Compact - Accurate - Priced Right! and adaptor for bayonet style (Delta cycle cutoff. List price 55.00 -you pay us Jeweled Meter Range Selector Switch and Philco) fittings. All multipliers bridge tested for 1 %accuracy TYPE CF3 Zero adjustment -built in batteries -63 SHURE P93 -W57A -pin type Molded bakeiite cote only 3- 13/16' A two insulator aide cowl mount -3 section terminals os. x with -5i pressure -1.6 2.7/e' x 2' 63' rod-supplied 3 insulators and wedge volt output -6000 cycle cut off. 198 adaptor tot 95% of all ear bodies List price 54.45 -our Special -complete with 48' lead. 199 MODEL 451 A List price $4.95 -our price TYPE CFA3 Astatie L- 70-new postwar design AC -DC -63 -solder terminals -1 got. press re Volt -O hm- All angle cowl or fender mount -A modern -1 volt output -4600 cycle cutoff. 198 Mflllamrneter Radiant development -fits all body contours, List price $5.55 -we quote you... straight or curved, cowl or fender. 3 section 03' A dependable instrument of rod easily adjusted to vertical with- 199 wide utility-sensitivity 1000 out tools -complete with 40' lead. PHILCO BEAM OF LIGHT 180 ohms per volt. List price 85.45 we sell for Selenium cell only. no holder. postpaid... Ranges: Volts AC, DC, and (Puts new life into Philco Changers) Output Ranges, GENERATOR 040 /50 /100;500 /1000; CONDENSERS Sapphire needle only. no mirror, 120 Ohms full scale, 500,000. postpaid Ohms center scale, 7200. PHILCO part No. 61 -0177 -.5 mfd.- 3f x lië -4' lead -slotted mounting NET complete with batteries strap for easy installation -Standard ALL RUBBER Merchandise -not war surplus- Present list price 51.00. LAMP CORD MODEL Our special- Underwriters Approved brown rub- 312 over 85% oft 14c ber covered insulated parallel Cord - Volt -Ohm - "Yips" apart easily -non fraying- Milliammeter 200 WATT SOLDERING IRON deluxe-way above average goabty. An economy pocket meter FAMOUS HEXACON ELECTRIC'S MODEL 201 300' featuring a 2' moving vane 989 meter. Ron Reads: AC-DC volts, 0-25/50 //125/250; Mille AC-DC. 0.50; FEATURES. MULTI -USE WIRE Ohms, 100,000; Full 200 watt replaceable dement. W tinned Copper tip, replaceable. One piece drawn casegun metal finish.. Stranded No. 22 tinned wire --glass mfd..05.15. "ROCKBESTOS" 1000 volt insula- 6 heavy duty cord -stand included. Comfortable, well Jacks provide range tion- fireproof aircraft wire -a war. selection. balanced handle. Operates on 110 volts -AC or DC. List Price $6.00 time development -at this low price 675 you can use the best- NET Complete with cord and plug Speed up your heavy work - 369 Save time -save money at 100 389 .A'Y'R- FAMOUS "LITTLE TRIPLETTS" feet 45c ,est...... The little Testers with the big 3' Meters OUTPUT TRANSFORMERS Bakelite cases 31/b' x S%' x 2Ys' Clean stocks - long leads - Range selection switch -long, easy to read mounting feet - mode to fit 4[ JEWELLED PILOT scales. We made a good buy -here they are where-you need them. LIGHT ASSEMBLIES at rock -bottom prices -The greatest buy For GFG -GRf to 4 ohm voice coil ever offered In precision testing equipment. --size 2'x 1%'. Candelabra screw base for 110 volt 50Lr 35L6-25l.6 to 4 ohm voice coil lamp. 1 %'x lW x Mount is l' hole. Model 650SC - OUTPUT METER Specify quantity of each type you need at 49c Lamps removable from front of panel. A 4000 ohm constant impedance Available marked 1.23 or 4 on back AC volt meter with ranges of 0.1.5- of white lens. 6 - 15 - 60- 150 volts. Conversion Order from the Ad chart for reading DB level from - YOUR CHOICE net 19c 10DB to +35 DB. 100 microam- Write - Wire - Phone pere meter. Excellent for receiver alignment, level indicators in recording equipment, general use on Include full remittance with orders of 53.00 or less. electronic apparatus. Regular net Include 25% deposit with all C.O.D. orders of 24.50. A "one time only "1049 $3.00 or more. Pricey subject to change without Special notice. buy at 1 1 SEND FOR FREE CATALOG Model 6068- VOLTAGE TESTER Checks voltage and polarity. Range: 0.440 AC-DC volts-definite indications for 115, 220, and 440 volt lines. Separate polarised at vane for AC or DC indication. KMVI'J SUPPLY Built in test leads. Excellent for checking wiring, fusas, general factory installation and maintenance. Every .plant - every electrician needs several at this low ENGINEERING CO., Inc. price. Regular net 16.67 895 Special at 125 SELDEN AVE. DETROIT 1, MICH.

14 RADIO -CRAFT for JUNE, !947 In This New World of Electronics Better Train- TODAY, the new war - c\snsl la, ing Means Better Opportunities I developed techniques offer greater opportunities than ever existed in the early days of broadcasting! Micro -Wave Relay Systems, Television, FM Broadcasting, Mobile Communication Systems for Trains, Automobiles, Busses, Trucks, many Industrial Applications-these are just a few of the new techniques which offer marvelous, exciting opportunities to you who are alert -and are qualified! `S Let Cleveland Institute Take Over Your Personal Up- Grading

Problem ! Qualified, competent instructors, ample, personalized instructional aids, or- derly, progressively arranged study assignments in recognized, approved technical texts - these are only a few of the many superior advantages of CIRE's plan of personalized spare -time home study training for professional self- improvement. CLEVELAND INSTITUTE COURSES OFFER COMPLETE TECHNI- ENROLL FOR INDIVIDUAL SECTIONS OF COURSES, CAL TRAINING RANGING FROM LOW -LEVEL TO COLLEGE - IF YOU PREFER. LEVEL. If you need only highly specialized training, you can A. )lasser Course In Radio Communication. Covers complete preparation for broadcast station employment study one or more of the following sections instead of Including preparation for FCC License Examinations. e a complete course. R. Advnnced Course in Radio Communication Engineering. 1. Mathematics of Radio. A college -level Radio Engineering Course. C. Specialised Television Engineering. 2. Fundamentals of DC and AC Theory. Including post -war Television Techniques. 2. Essentials of Radio Communication. All Courses Include The Remarkable Workbooks of Instructional Aids, prepared by 4. Communication Networks. the instructing staff of Cleveland Institute. 5. Advanced Radio Telephony for the Broadcast Choose the course best suited to your needs -Start with the Operator. section you are qualified to enter -Use the economical CIRE 6. Audio and Radio Components and Systems (Design "Pay -As- You -Go- Plan." of Receiver and Transmitter Equipment). CLEVELAND INSTITUTE r - (MAIL THIS COUPON) Cleveland Institute of Radio Electronics. RC -6. Terms nI Tower. Cleveland 17. Ohba. OF RADIO ELECTRONICS Genf Ionien: Plea e bend information about amer home enw.v. in Radio Eledren los. I desire training In A a (DC Contractors to the Canadian Broadcasting NAME Corporation 1 hate had experience In broadcasting eenking operating RC -6 Terminal Tower ADDRESS mfg. Cl CAA ArmPNsaf amateur other I sm s CLEVELAND 13, OHIO CITY High School Grad. College Decree Approved for Training under "G -I Bill of Rights" ZONE nT.1TE Cheek here for Veteran Enrollment Information. Commercial y Radio 0 p erators' LICENSE°' ITS EASY IF YOU FOLLOW OUR PLAN! Thousands of new jobs are opening up-F M, TELEVISION, MOBILE COMMUNICA- tNSnn)TE TIONS SYSTEMS, are only a few of the radio fields which require licensed operators. Et1,lyD., itool,oa C>I" TIME IS LO IMPORTANT TO YOU! You can get your License quickly with Assures a MINIMUM of time in getting your t..^d'e- NILSON'S MASTER COURSE in RADIO COM- ticket. MUNICATION and e,clusive CIRE Workbooks FREE BOOKLET tells you the Government of Instructional Aids. Requirements for all classes of commercial Saves you many hours licenses - Sent immediately upon receipt of Don't Delay - or random, undirected study. coupon. for Veteran Approved MAILTH1S COUPON Write Today! Trainingd under "G -I Bill of Rights" CLEVELAND INSTITUTE OF RADIO ELECTRONICS RC -6 Terminal Tower, Cleveland 13, Ohio CLEVELAND Gentlemen: Please send information about your Home Stilly Course for preparation for INSTITUTE PCC Commercial ',Wen.. Examinations (this sourde dued nut cover amateur Mew,. OF RADIO ELECTRONICS exammatluns ), Name Contractors to the Cenadlas BroadeartIng Corporation Address City Zone State RC -6 Terminal Tower {] It a Veteran check here CLEVELAND 13, OHIO

RADIO -CRAFT for JUNE, 194.7 15 SPRAGUE TRADING POST

WANTED- Hellierafters short -wave re- SWAP -BUY ceiver In good condition. Have electronic. vat -ohm- milliammerer. excellent condition for trade. \v'rlte stating pria. etc. Patel Cowing, Blackburn SL. Lynchburg, OR SELL Replacing Va. receiver FOR SALE- Ilallierarters SX -25 WANTED -Tined amateur good also 50 x'mltter In with bass -relics speaker, 8100: ft. condition. Will pay In monthly Install- co-ax cable. $1.75. L. C. Zaret. 6246 ments. Will furnish bank and other ref- N. Oakley die., Chicago, Ill. erences. Louis A. Vas. Rt. 4. Middle lid., Ashtabula. Ohio. WANTED -Circuit diagram for Navy Oaks Wets sonar unit. Have many small parts for FOR Ridge Ave.. SALE -Gordon A -.0 turntable 10 to sale. Peter \Vnukowskl, 344 100 rpm and magnetic radar Pa. pickup: mo- Kingston, tor 28 V. D -C or 110 V. A -C. 12,000 rpm, IS ONLY THE new; Shure P -935 and Aetatle L -75.8. E. WANTED -The following German tubes: Colo, 215 N. Lord Ave., Chicago 44, 'IL DC11-11; DF -11: DAF -11; DL -11; UY11; Arthur Hellmann, 15 Argle ltd.. Brooklyn SELL SWAP N. Y. BEGINNING! OR -Mercury 35 mm. earn- 18, era. F3.5. 1/1000 sec. 18' to Inflo., with leather case, sync, flash gun, attached FOR SALE -National l -10 receiver torn - light meter. Sell for $30, or trade for new plete with tubes and power supple', $40. Sprague Type WR Capacitors BC -875 -E trans., IiC -348 receiver, or Geo. E. Anthony. 878 Gilbert St., Colum- are especially designed can type 11C-654 -A Rea -Tana. G. E. Oden, 217 bus 6, Oho. dry electrolytics having very Marshall SL, Wauseon, Ohlo. WANTED -Melesner pre- aligned tuning high voltage formation. They'll FOR SALE -2 307 -A's, 3 sockets, 95; unit 13-7610. John Wainwright, Green - Simeon 0 -3 /. meter, $2.75; 2- 882's. .. volt- mount, \Id.. .. . stand high surges or peak 2 socket., 87.25: 7010 Ira Mal,. $2.85; ages. They'll handle the strong 815.5.715 ßa staff, $2.25: 28 V. dynamotor FOR SALE -AC SW -3 templets with unit, $6. Ralph N. Huse. 820 Hont Ave., coils for 20.40 -80 mir. bands, power sup - a -c ripples that often cause ordinary 450v. Sumner, Wash. pty; also goal 50-watt rig, OVO Mal one, to pair 61.6's final, 40 & 80 intr. stale, power dry electrolytic capacitors break down. SWAP G11 supple'. F. Boo W3ESX, 3131 N. Percy In short, they're absolutely "tops" for -1 ea. -F lkie- talkie 9875 St., Philadelphia 33. l'a. ka), new, for BC-398-(1 receiver. Need replacing ANY wet electrolytic capacitor not be converted. State difference in price. If any. Also tant eamersion data WANTED --Small relays to operate nt 1 more besides! in a radio set - and a lot for BC -457. 458A series. Francis Corned, or less; tiny motors; tiny Thyratrons. 2224 W. Adana St., Chicago. sub -miniature tube sockets 5AX. GAN, Actually, they're "just what the doctor ordered" Ill. 7AX; tiny 1.f. cans. free. unimporiata. BOXES, television sets or any appli- Buy or swap. L. Kurshner, 1913 Franklin for JUKE SELL OR SWAP- l/alllcraften SX28 -A ,Circle, Hollywood 28. Calif. cation where ordinary condensers have the an- receiver complete with speaker and cabi- habit of breaking down to cause a whale net. Will trade for Speed Graphic 4 it 5 TRADE -Hare mine. radio parts, new and noying or 3% x 4% complete. RCA TMV 97C used in trade for mimeograph machine. of a lot of trouble not to mention dissatisfied 61g, gen.. Rider's manual. 1 & 2, Ab- - bott with legal sire. :d. ]Lowell. Rt. 2, Dillon. S. C. transceiver pwr. pk., 2 mira customers. Buy them from Sprague distributors M. J. Curley Jr., 412 Forest Ave., W.B. SELL OR SWAP -Model airplane and in 8, 16 and 25 mfd. sizes - to fit standard "wet" S.I. #1, New York, N. Y. motor; also parts from Edison power nail: a few radio parts: some midget tubes: mounting holes -and CONSERVATIVELY FOR SALE -Up lo 30 lbs. radio parts. 6C9. OAKS. GAOL. Jim Roche. 3215 Dare rated at 500v. D.C. working voltage and 600v. i.t.. r.f. colle. trausfnrtners, weaken, eta N. C., Cedar ]rapids, lows. f per package $3. as long as they last. Yon surge! Ask for Sprague Type Will pay postage. Rusicka. 924 17th Ara. WANTED- Hallicraftcrs SX_25 Storer Cedar Rapids. Iowa. Defiant. new or used State -price. -Jose Tavares. 2640 S. 9tls St., Philadelphia, FOR SALE- 5letssner 150 -B transmitter. l'a, complete with Meissner sig. shifter. key, mike and spare parts. Operates 0,1_80- FOR SALE -Ultra portable "Lucy" re- 40-20-11-10 mien. II-2120X receiver. oth ceiver. without 11$0, cona,lacly wired. used lese than 50 logged hours, $450, f.o.b. W5HOF, 720 W. Ekberg. Kingsville, with speaker - Navy transformer, including SELL OR SWAP -Several home-study ra- WANTED- BC-610 converted for 10mtre. Texas. phases, 2.5 to 12.5 me, $20. Father Geffen, dio courses; commercial, ample multiple Have IIIISC. radio parts and supplies. B. Norwalk. Cam. choice questions and answers for radin Howell, 501 W. Harden SL, Graham, FOR SALE- llalllerafter FM -AM 8 -8T 'phono 1st class. and radio- telaraph 2nd N. C. WANTED -Technical books or (lam VHF, 130 -210 me. Thrift Appliances, 1891 gear. clam 10 fof 810 Want Rider manuals, Southern Blvd., Brdnx 60. N. Y. Cash or trade. Eddie Howell, 501 W. photo enlarger. commercial i motter. SWAP -Mar. 1932-Dee. 1946 CST's for - Haden. Graham, N. C. WOWIJ, inox 1298. Hollywood 28, Calif. useful A. J. Urban, 283 Garden surplus. FOR SALE -German radio. in good condi- St., Dartford 5, Conn. tion, looks like small suitcase. WANTED -Army and Navy clocks. 12 or SELL OR lnstrudngraph, 10 paru an SWAP- be substituted as well as. tuba. A -C. D -C, 24 hour: chronometer. Cash or trade radio tapes. like new; Federal 219-enlarger, ex- FOR 14 has tone control. 3 -band switch, phono- and amateur radio equipment. Wnt. Han- cellent condition. Want receiver good con- SALE -Used -tube Navy typo FIBS receiver -c operation, complete with In- plifier. Made by Nora Radio Corp. $40. sen, 165 Silverbrook Ave.. Niles, Mich. dition. R. W2I111N, 7 SL, Simon Madison hook, 2 In 4 D. W. Andrews. liox 105. Okle- Washington, N. atruction Covers -20 mc.. Kingfish, Port Y. hands, and of. level control. 1150. WANTED -Code machine with r.f. practice tuned 4 tapes. costluental tilerso. condition imma- noise limiter. precision dial. plato FOR SALE -Neva -band Hallleraftera FOR SALE -New Amcrtran po'eer i former r.f. stage, link coupled to mixer. 875 marine transceiver, 13 tuba. 30- watts, terial. Cush. FIs -it Shop, Bird island. l'F -25A, 100. 110. 115, 120 V. pre., 600 Minn. f.o.b. J. B. Fell. W7111E. 517 Ave. 0, 1051 ire to 2300 kr., $125; 3 Motorola V. sec, et.. 4 -3.75 V. windings at L25 Billings. Mont. SOD transmitters, used. with tubes, dyna- each, Toilage winding at .120 snip. hleh- motor for 6V. operation. $25 each. 8 for WANTED = Instruction manuals on Army amp.. GO cy. Fred Marrow, 3495 Broad- Skell, ham 965. Robert 510 Castanet Ave., San SCR -274N and SC14.522: also want to buy way, New York 31. N. Y. WANTED-Any good x'mitter like Antonio 2, Texas. freq. meter 1iC -221, A.T. AK. or AH. IIC -610; HT -9E or HT -9, have new test J. H. Oxford, P.O. equipment for part trade. Donald Clark, Smitten. Air Services, WANTED -Dead or alive short-wave re- SELL OR issues CST: June- Box 290, Memphis 1, Tenn. Blackfoot Radio Shop, Blackfoot, Idaho. SWAP-Bark ceiver; rohpne expander; large speaker Dec. '33; Jan. -Dec. '34; Jan. -Dee, except with twcole,n or Jensen Co -axial or similar Sept. '35; .Ian. -Dec. '36; Jan. -May,- '9T; WANTED -Speed key (bug) electronic or speakers. liane car radios, manuals and URGENTLY NEEDED -Auburn. (chassie typo 841 tube. Want mise. parte. tubes, mechanical. In ti I condition. J .Inrkmv'- sono testers -what. do you need? Glenn 941) or r.f. or oscillator coil for same; etc. Carl England, Jr.. 50 Lyme Rd.. ski, Iiorseneck Rd., Caldwell. N. J. - Watt, Chanute, Reus. Auburn (chards 320) or I.f. transform- Hanover, N. li. ers for same. Cash or swap. Lewis W. Robinson, Ave.. Nov York 58. 3781 3rd SELL OR SWAP -New 14 -watt p.a. M- N. Y. I om using 6517, ói0'7. 5Y30. Pp 8V6's YOUR OWN AD RUN HERE FREE Phono top with Shure Glider pick -up. 12' FOR SALE -S -38 in perfect condition. 18 -watt Utah uns. speaker, floor mike The Sprague Trading Post is to radio subjects. Make sure $35; also S -41 \V.,r. Colby, 122 Alain St. stand. Cash or trade for 'scope or ham a free advertising service for the your meaning is clear. No com- Oswego, N. Y. root. T. J. Erwin, 3735 Milwaukee Ave., Chicago 41. Iii. benefit of our radio friends. Pro- mercial advertising or the offer- viding only that it fits in with SWAP- Longinee pocket watch, $125 ing of merchandise to the high- value for good communications receiver FOR SALE -Weston meters 301; trans - the spirit of this service. we'll est bidder is acceptable. Sprague. miHing condensers: tubes; transformers: gladly run your own ad in the equal value; also Webster 56 record of course, assumes no respon- changer for harp equipment. Art Meek, other supplies: Collins transmitter S.A. first available issue of one of the 1430 Elton ltd., Jennings, la. 9175. Write for list. Leo F. Kersey. White six radio magazines in which sibility in connection with mer- Sulphur Sprinta, W. Ta. this chandise bought or sold through feature appears. Write FOR SALE -Collins AN/ART-13 mftter. or Hold these columns or for the result- i FOR SALE- llandic- lalkle, complete with CAREFULLY print. it less tubes. power supply. calibration Ntal, tubes, coils, stale. mike, receiver. No ales, to 40 less. ing transactions. -13, words or Confine it 7100; also 3 CFI units for AN /ART $30 pair. Portable amplifier 15 -watt com- dynamotor 28 V., 32 amp.. Send your ad to $1.50 a.: plete with 12. Jensen. Speaker. 6 tubes, 2 d -c/750 V., 0.35 amp., 400 V.. 0.75 amp., Input.. tone control. $35. H. W. glerideth. b-c. $:5. E, Lorick, 907 W. Nevada, Ur- 1492 Granrlllo Ave. Chicago 28, m. DEPT. RC -67 SPRAGUE PRODUCTS COMPANY ana. nl. North Adams, Mass. FOR SALE - Complete sets dating back 10 WANTED -New or used Stentor trans- rra.: CST: Electronles: I.B.F.; Comment - (Jobbing distributing organizntion for products of the formera A4206: A4404; portable recorder rations magoloco. All perfect, - Inset. P. Sprague Rlrrtric Co.) with play bark. Will pay top price. Riley Rosenblatt W2AKF. Box 905,, Hobokaa, r. Parsons \V2Sitf, Raonetto Lake, N. Y. N. J. ASK FOR SPRAGUE CAPACITORS and KOOLOHM RESISTORS by name! 'Trademark Beg. D.B. Pat. Off.

16 RADIO -CRAFT for JUNE, 1947 FM AND ALTITUDE

3414 Race for Altitude ,7s Oit

By HUGO GERNSBACK

FREQUENCY MODULATION, which before the war Granite Peak, Mont. 12,850 170 miles had already made excellent progress, is now going Mt. Elbert, Colo. 14,431 180 miles ahead in earnest with greater and more rapid strides Mt. Whitney, Calif. 14,495 180 miles than ever. Mt. Rainier, Wash. 14,408 180 miles According to the latest. reports of the Federal Com- This, of course, is only a theoretical evaluation. In munications Commission, there are now in operation some cases it will not be expedient to place transmitters more than 200 FM transmitters in the U. S. against over on these or other high 'peaks, for the following consider- 1,000 AM transmitters. The FCC estimates that by the ations: end of this year there will be 700 FM transmitting sta- It is one thing to get altitude for a transmitter but tions on the air. How many more there will be next year quite another thing to place it in a practical and an is not possible to predict exactly at this moment. economical location. Areas around many mountain peaks That FM is going ahead by leaps and bounds is further are often sparsely inhabited, to such an extent that no attested to by the Radio Manufacturers' Association, one would wish to build an expensive FM station just for which in a statement, as we go to press, estimates that the privilege of transmitting to a few thousand listeners. the output of FM receivers for the year 1947 will be As a rule, the higher and more elevated the location, the between 1,800,000 and 2,100,000 units. more extensive the mountain range and the sparser the We have mentioned a number of times in this space population. that to satisfactorily blanket the United States with FM Other factors also make it undesirable or would unwise to transmitters require a minimum of 1,500 stations place transmitters at extreme altitudes. First, we may 1,000 against the odd AM transmitters. As is well known, have difficulty in reaching the peak which may be due to the shorter wave lengths used by FM, the range snow- and ice -bound over large parts of the year. of the is Second, transmitter dependent on its horizon. FM trans- there is the high cost of erecting transmitters on such mission normally does not extend much beyond this point, uninhabitable and difficult elevations. and if there is FM reception much beyond the horizon, It would therefore seem that extremely it is a freak action. high moun- Thus the average FM transmitting tainous regions will not prove attractive for FM trans- tower of about 500 to 600 feet covers a satisfactory range mitters except under exceptional and special conditions. of only about 35 miles. There are other solutions to problem. If a given FM the One of the transmitter wishes to increase its range, most spectacular will be the erection of extremely there is at present only way high one to do so. The transmitter steel towers in various parts of the country. Already, has to gain altitude antenna must go higher. -its The Station KRNT of Des Moines, Iowa, is planning a tower higher the transmitter, the greater the coverage. For 1,530 feet high -280 feet higher than this reason, all FM the Empire State transmitters strive for as high an Building. This, indeed, would make it the highest man- elevation as possible. Thus, in New York City we have made structure in an FM transmitter the world. Even higher towers than on top of the 1,250 -foot Empire State this can be constructed, if there is a demand for them. Building. This immediately gives a larger coverage for There the is no technical reason why towers of this type, transmitter which now can reach an audience within even several times the height of the Empire approximately a 55 -mile State Build- radius from the transmitter. ing, cannot be erected, if the owners are willing to pay Wherever there is a high natural elevation, the FM the price. Needless engineers to say, such towers would be extreme- are anxious to locate on it, if at all practical. ly expensive, but if a much larger For example, in territory can be cov- New England we.have an FM Station ered by the FM transmitter -particularly in a populous on Mt. Washington where its transmitter is at an eleva- district might pay tion of -it to do so. 6,288 feet. This gives the station a transmitting It will be noted that whereas the radius of 120 miles. average broadcast AM transmitter mast usually runs only a few hundred It is probable that the United States will soon be dotted feet high, the average with FM stations FM transmitter antenna already on many mountain tops. We give here runs from 600 to 800 feet, and this spread between their a short tabulation of a few 'high points in the United heights may be expected to increase. States and their location, showing where eventually FM transmitters High mountainous elevations, high man -made towers might be located. The radius of transmis- are not the sole solution to sion is also given. the FM altitude problem. A year ago the Westinghouse Electric & Manufacturing Corporation advanced a plan whereby HIGH MOUNTAINS IN U.S. the entire United States could be covered by a few large airplanes circling Has FM FM Aver- overhead Elevation Ft. Station age Range constantly at a high elevation -five and three Mt. Washington, N. H. 6,288 yes 120 miles quarters miles up. Each plane thus would cover a radius Mt. Davis, Pa. 3,213 90 miles of 200 miles. This scheme (in' conjunction with tele- Mt. Mitchell, N. C. 6,684 yes 130 miles vision) the sponsors term stratovision. This proposal is Cheaha Mountain, Ala. 2,407 85 miles as yet in its developing stage. (Continued on page 74)

RADIO -CRAFT for JUNE, 1947 17 RAILROAD RADIO takes on a new meaning with the introduction of individual speakers for passengers, announced last month by the Budd Co. RADIO - ELECTRONICS Their new passenger coaches are furnished with individual rubber -embedded speakers in the headrests of the seats. Since the speakers are placed at ear level low volume is ample for comfort- Items Interesting to able reception, and passengers in adjoining seats may listen to different FM IN BRITAIN takes its first step of the four stations, then, in company programs. with the announcement last month that with United States deputy marshals, The speakers are connected to a cen- the Marconi company is to supply a entered the four homes at the same in- tral receiving unit which permits pas- 25- kilowatt frequency- modulated broad- stant. The transmitting equipment was sengers to select one of several pro- cast transmitter to the BBC. This is found in all cases. grams with a multiple switch on the expected to be used on a regular service Three were found in possession of ac- arm of the seat. Besides having a num- rather than an experimental basis. tive transmitters. The fourth station had been closed down by order of the operator's mother, who had told her son to store the equipment in the attic till she could ascertain whether or not he Controls of the rail- required a license to operate it. The boys, in view of their youth and road radio sets are ignorance of the possible serious conse- mounted in the arms quences of their activity, were paroled of the seats. Below - by the United States attorney in the custody of parents. how the speakers are their installed in cushions. AMATEURS of the world will now form an unofficial arm of the United Nations, following an agreement signed last month between the assistant secretary-general of the United Nations organization and George W. Bailey, secretary of the International Amateur Radio Union. Chief duty of the amateurs will be to compile reports on the reception and effectiveness of United Nations radio broadcasts to various parts of the world. ber of radio programs on tap, two pro- They will also handle certain news grams of recorded music from a wire broadcasts and other noncommercial recording unit will also be available. point -to -point traffic for the UN, and The same principle of selective listen- will also take part in discussions on ing is being used in the Rock Island United Nations topics. Line's Golden Rocket, in which several Radio amateurs who take part in the low- powered speakers are mounted in new net will be licensed as special the ceiling of each car. The speakers United Nations Amateur Radio Aides. cover only a small space below them; Details of the plan are being worked thus several programs can be received SHIP RADAR will be made more effec- out by a four -man board, composed of without interference at different points tive by new microwave "lighthouses," Brigadier General F. E. .Stoner, chief in the same car. General Electric reveals. A unit tested communications engineer for the United last month at New London, Connecticut, Nations, Peter Aylen, director of the FM RELAYING without special wire sends waves in all directions at a fre- radio division of the Department of lines or relay stations was demonstrated quency of 3200 megacycles. These are Public Information, Kenneth B. War- last month at the first meeting of the picked up by the ship's radar, appearing ner, secretary of the American Radio newly- formed Frequency Modulation on the screen as a very bright ray which Relay League, and Francis E. Handy, Association. The program originated in shows the exact position of the beacon the League's communications manager. a small studio in Yonkers, N. Y., from with respect to the ship. which it was sent by a low-powered It is expected that the 'microwave FM ALLOCATIONS are expected to transmitter to Major Armstrong's sta- units will be installed in lighthouses. be revised drastically following the tion at Alpine, a few miles away. FM Skippers can then use the radar signals hearings of May 8 and 9. The Federal station WBCA, Schenectady, simply in fogs which render the light invisible. Communications Commission proposes tuned in the program and rebroadcast it In either fog or clear weather, they also that stations be spaced four channels for the benefit of the FM conference provide a useful distance indication not apart, because of interference in some meeting, which was in session in the obtainable directly from a simple light. areas where stations are working with Ten Eyck Hotel in nearby Albany. less separation. Even where stations are Major Armstrong pointed out in a ILLEGAL BROADCASTERS who two channels apart, receivers in areas speech that FM's greater freedom from operated a "network" of four stations near a number of FM stations suddenly fading and interference makes it pos- found themselves in the hands of the jump from one station to another. sible for one station to pick up a pro- United States Government last month. The FCC recognizes that the difficulty gram from another in what he called The broadcasts, of phonograph records is to some extent due to receiver design, "the chain reaction" without the help interspersed with musical criticism and pointing out that Operation on alternate of expensive wire lines. It was stated wisecracking in the best "disc-jockey" channels "results in interference in that a chain of stations extending, for tradition, proved to have come from the many of the receivers being produced at of the Atlantic transmitters of four Summit, N. J., the present time." Thus it appears that example, the full length of Coast could pass on the signals from high -school boys. as more is learned about the design and hinted Receiving complaints of interference high- frequency receiving circuits, it will one to the other, it was that channels now a transcontinental network might be on airway and marine safety frequen- be possible to allocate the attempted in the near future. cies, FCC engineers quietly located each to be used as buffers. 18 RADIO -CRAFT for JUNE, 1947 WORLD'S HIGHEST STRUCTURE is to be an FM radio tower, it was an- MONTHLY REVIEW nounced last month by Phil Hoffman, manager of Radio KRNT, Des Moines, Iowa. Construction of the tower depends on approval of the station's application for a construction permit. the Radio Technician The new tower will be 280 feet higher

U.S. SHORTWAVE broadcast activity COLOR TELEVISION on a 71/2- by -10- I runs second to that of Great Britain, foot theater screen was shown public- KRNT the State Department revealed last ly for the first time in Philadelphia, TOWER month. According to a survey made by April 30, by Radio Corporation of 1530 FT. the Department, Britain used 16.5 per- America, in a demonstration of its all - cent of the total broadcasting time for electronic color television system at The the world and the United States air Franklin Institute. Color' motion picture activity accounted for 9.2 percent of films and slides were projected. EMPIRE STATE the time. Dr. V. K. Zworykin, Vice -President BUILDING The third country was Soviet Russia, and Technical Consultant of the RCA 1250 FT with 6 percent. France was fourth with Laboratories Division, who demonstrat- 3.8 percent. Broadcasts from British ed the new system to illustrate his ad- stations were in 46 languages, while dress: "All- Electronic Color Television" American broadcasts were beamed out before the Institute, disclosed that the in 24, with 3 more to be added shortly, pick -up unit used in the demonstration according to the report. incorporates the electronic "flying spot" which has been under development for SUBMARINE TELEVISION was suc- nearly ten years. In this system, he cessfully demonstrated for the first time explained, the flying spot of light is last month when a broadcast was made created on the screen of the kinescope by from the USS Trumpetfish at the Brooklyn Navy Yard. the electron scanning beam. The ship's maneuvers were covered by The light from this spot is projected Image Orthicon cameras as it sub- through color slides or films, scanning merged, conducted a mock torpedo at- the entire surface of the scene or ob- tack, and finally surfaced. The program ject, point by point. As the light beam, was broadcast over NBC's station then tinted with color, emerges from the WNBT, in New York, and carried by film or slide, it passes through a series co -axial cable to Philadelphia, Schenec- of filters which separate respectively tady and Washington, from which cities the red, green and blue portions of the it was broadcast by WPTZ, WRGB and color in the beam. WTTG respectively. Each color then is reflected into photocells which change the light values NETWORK FM on a regular basis into electrical signals for transmission was introduced by the Army Air Forces to the receiver. The flying spot method, The tower the Band in a special series of 7 weekly KRNT and Empire State Building he added, assures perfect picture regis- Building, concerts which began early in April. tration by permitting the transmission than the Empire State present The broadcasts originated at WASH in of the three color values of each picture holder of the height title. Broadcasts Washington and were relayed by land element simultaneously. from it are expected to have a range lines to Major Armstrong's W2XMN- of more than 120 miles, if the full au- At a press preview before the Insti. thorized power of 157,000 watts is used. W2XEA at Alpine, New Jersey. The tute meeting, correspondents asked a programs were then picked up by radio The station is owned by the Cowles WBCA number of searching questions about Broadcasting Co., already owners of by stations in Schenectady and the possible effects of large -screen tele- WDRC -FM in Hartford, Connecticut; the highest radio tower in the world - vision on the present moving- picture the 927 -foot mast of AM station WNAX WGTR in Paxton, Mass; WBIB, New theaters. Haven, Conn.; WIZZ at Wilkes -Barre, at Yankton, South Da'rota, which has Penna.; and WMNE, Mt. Washington, In reply, David Sarnoff, president of been in operation more than three years. N. H. RCA, stated that The FM signals were also carried by as opera and the wire to Rochester and Buffalo, from concert hall had which they were picked up during one found that r a di o or more of the weekly programs by a helped rather than number of stations. Thus the programs harmed them, the were heard in Syracuse, Utica and moving picture in- find Hornell, and in Cambridge, Mass. The dustry might Al R, series ended May 7, after having broad- television a great COOLING cast weekly for seven weeks. Fifteen aid. The moving UNIT stations formed part of the network for picture industry, one or more broadcasts. he commented, had not been responsi- RADIO RECEIVERS in the United ble for the intro- States homes have reached the number duction of the talk- of 52,000,000, the Columbia Broadcast- ies, which came ing System reported last month. This from the electronic figure excludes portables as well as auto- industry. Possibly CONTROL mobile and other types which are not the moving picture PARSL strictly home receivers. industry people to- One in every 5 families bought a radio day are not fully in 1946, bringing the number of radio alive to the possi- homes to 35,900,000. One -third of all bilities of televi- U.S. homes had more than one radio. sion, he suggested. A cutaway drawing of RCA's large- screen color television projector.

RADIO -CRAFT for JUNE. 1947 19 VISION By H. W. SECOR television is that the same apparent white signals over a carrier of suitable definition is attainable with a smaller width. Color is finally restored to the number of lines. For example, with the reconstructed image at the receiver, by PART 1 present 525 -line image used in the spinning a second color filter in front sequential system (color image) the of the picture tube. The rotating color same apparent definition is obtained as filters at the transmitter and the re- when using 900 lines in a black and ceiver must revolve in perfect syn- white image (as explained in Dr. Peter chronism ; not only must the speed of Goldmark's [CBS] report presented to both discs be identical, but they must TELEVISION images in natural the Federal Communications Commis- be in phase. When the red filter is before colors appeal strongly to the im- sion ). the image reflected into the orthicon agination of the radio public. It The two principal methods so far tube at the transmitter, the red filter is not easy for the layman to un- demonstrated for producing color tele- must be in front of the image at the derstand why it is so much more diffi- vision are RCA's simultaneous system receiver. Perfect registering of the two cult to reproduce pictures in color than and the CBS sequential method. In the color filters is secured by transmitting in black and white. That difficulty does simultaneous system all 3 basic colors a synchronizing pulse or signal at regu- exist, but several means of surmount- (red, blue, and green) are transmitted lar intervals. This has no effect on the ing it have been proposed and at least at the same time; in the sequential plan picture. partly developed. the 3 colors are sent one after the other. One 16-me carrier (see Fig. 2 -a) is To begin with, stations transmitting The Columbia Broadcasting System's used to transmit the 3 colors in the color television images require a much sequential method has been tested ex- sequential systeni. One color follows wider frequency band than black and perimentally for a period of about three another in rapid sequence. In many of white (B & W) images. The present years at a cost of $2,000,000. the CBS tests the sound was trans- B & W pictures occupy a band only 6 This extensively demonstrated system mitted by injecting FM bursts or pulses me wide, while 14.5 me is necessary for transmits the 3 basic colors (red, blue, on the picture signal carrier, without the simultaneous (color) system and 16 and green) one after the other. In pick- interfering with the image transmission. me for the sequential (color) trans- ing up a live subject before the camera (Later tests as reported by Dr. Gold - missions. at the transmitter, the scene is brightly mark, have indicated that it is prefer- The cost of color television receivers illuminated and an orthicon tube scans able to transmit the sound on a separate would be about twice that of B & W the scene through a revolving color subcarrier. One of the advantages of sets, according to engineers' estimates. filter. See Fig. 1 -a. The images are pro- the separate sound transmission is a One strong point in favor of color gressively transmitted as black and greater signal -to -noise ratio under all conditions.) STUDIO LIGHTS TIME REVOLVING COLOR DISC REVOLVING COLOR RED BLUE GREEN FILTER LENS BBW IMAGE / 1 -

MIRRORURREFLECTEÓ ALL ON ONE CARRIER; LIGHT

ORTHICON TUBE

L 1 AMPLIFIER 3 .0' to f / 0 COÙ

w IA rr i`i.DPb -- .ra uas -eim MI1 Fig. I- a- Operations in sequential color television, from subject to viewer. The three colors on carrier follow each other in time. 20 RADIO -CRAFT for JUNE, 1947 The sequential system iniages are introduces an objectionable flicker; too transmitte8 at present with 525 lines many pictures per second unduly in- and 48 frames per second. The succes- creases the carrier band width required. sive color tone images follow one another Images with 525 lines have been so rapidly that when they are super- found fairly satisfactory in the tests imposed on one another at the receiver, and demonstrations made by CBS; in- they produce a satisfactory color image, crease in detail has not been found to similar to that scanned by the camera be in proportion to increase in the num- at the transmitter. ber of lines employed. Besides, as the lineage is increased, carrier band width

SOUND CARRIER goes up proportionately, thus reducing GUARD BAND the number of stations that can operate in an assigned band. Photos A and B show the CBS color ONER RED,GREEN OR BLUE /L 1 television receiver; a diagram of the E BAND receiver appears in Fig. 4. This set is - -VIDEO MOD BANDWIDTH arranged for diplex (combination video and sound) reception. A color syn- F 16 MC CHANNEL WIDTH REOUIRED chronizing separator amplifier is used - to maintain the color disc motor in per- SOUND fect step. The balance of the components corresponds to those found in the GREEN \ BLUE RED present black and white receivers. Photo A -Color television receiver by CBS. One of the criticisms of the se- 14.5 MC el quential receiver has been that it sequential receiver demonstrated by could not pick up B & W images CBS was 71/2 x 10 inches, the picture by stations now on the air. The being magnified about 40 percent by a CTURE CARRI Fig. 2 -a (top) 2 -b. CBS report shows (center) and 2-c (at FRAME a dual -band CBS COLOR I /48TH SECOND COLOR FRAME I /48TH SECOND bottom). Sequential, receiver simultaneous, black - that can RED BLUE GREEÑN' and -white bandwidths. receive both color images on the new u.h.f (480 -920 mc) The method of scanning the odd and band and B & W pictures on the low - even lines of the image progressively e b c d e f is shown in Fig. 3. At 48 color frames frequency (40 -220 per second, each color scanning will mc) band, by the Fig. 3 -The color interlacing method used in sequential scanning. occupy 1/144 second. Six color fields addition of four are shown in progressive scanning se- tubes. A later circuit for a dual -band re- lens placed in front of the revolving quence. First the odd lines are scanned ceiver submitted by Dr. Goldmark per- color filter. The standard direct -view- for red (by the red filter) in 1/144 sec- mits the reception of color and B & W ing model color receiver (CBS sequen- ond; next the even lines are scanned imageswithout the addition of any tubes. tial) employs 31 tubes, with a 10 -inch for blue. Third, the odd lines are Suitable ganged switches are provided picture tube. (The image size is 71/2 x scanned for green. In the fourth color for changing the set for receiving ei- 10 inches.) Larger images, measuring field the even lines are scanned for red, ther color or black and white pictures. 151/4 by 21 inches, have been produced in the fifth the odd lines are scanned It is interesting to note that B & W by a projection -type receiver (see Photo for blue, and in the sixth field the even images can be reproduced on the tube C and Fig. 5) utilizing a Schmidt optical lines are scanned for green. used for color images. If the color disc system with a truncated cone revolving A complete color picture takes 1/24 is removed, a black and white image is color filter. A recent model of such a second, as the diagram shows. This observed on the screen of the cathode - receiver produced color images nearly value was chosen as a happy medium - ray tube. the same size and used but 34 tubes. too low a number of pictures per second The size of the color image on the (Continued on page 40)

PROJECTION KINESCOPE MIRROR

LENS XMMITTER --"os.'r3CARRIERS ó% A t `, 1 ` R /CALOR IMAGE t UVE SUBJECT

BLUE 1 1 Í r o©000 GREEN

Fig. 1 -b-The simultaneous system ofcolor vis. Light from the subject is split and transmitted on three adjacent carriers. RADIO -CRAFT for JUNE, 1947 21 "Smrttr.

ICover Feature Pioneer Atom Splittes ELECTRONICS has played and is she and Dr. Hahn had achieved could break up atoms of uranium, releasing playing so great a role in nuclear be due only to actual atomic fission. in the process the hundreds of millions research that it is impossible Meanwhile, Fermi had also been re- of volts of energy that were later to really to separate electronics and pelled from the totalitarian field, and supply power for the atomic bomb. nucleonics. Thus it is not surprising to was in New York when Dr. Meitner and Fermi almost immediately discussed see on our cover one of the world's most the possibilities of atomic power with distinguished atomic physicists checking the U.S. Navy. Armed with the new a piece of obviously electronic ap- evidence of atomic fission, the scientists paratus. were able to interest the government. The pictured equipment is installed From that time little was heard of Pro- in the Argonne Laboratory, University fessor Fermi until after the war. His of Chicago, where two nuclear chain important work on the atomic bomb was piles are now in operation. The elec- recognized by the United States by an tronic end of apparatus used in select- award of the Medal of Merit on March ing, counting and studying neutrons, it 20th, 1946. The citation to Dr. Fermi is still in the "restricted" class. No de- reads: tailed description of it can as yet be "As the pioneer who was the first printed. man in all the world to achieve The physicist is Dr. Enrico Fermi, nuclear chain reaction, and as As- who has perhaps a shade better claim sociate Director of the Los Alamos than half -a -dozen others to be con- Laboratory, Manhattan Engineer- sidered the man who started the whole ing District, Army Service Forces, atomic ball rolling. He it was who first his essential experimental work discovered that by slowing down neu- and consulting service involved trons, they could be made to penetrate great responsibility and scientific the center of even the densest atom. distinction. A great experimental With an extra neutron in its nucleus, physicist, Dr. Fermi's sound scien- the unstable atom of uranium shook tific judgment, his initiative and itself, gave off an electron, and became resourcefulness and unswerving de- the new element Neptunium (No. 93) votion to duty have contributed with an atomic weight of 239 (approxi- vitally to the success of the Atomic mate). Other new transuranic elements bomb project." never before known on earth were pro- Fermi, leader in atomic research. duced as the metamorphosed uranium Dr. Enrico Atomic research apparatus atom tried to settle down. No less important than the personali- Experimenting with the new trans- O. R. Frisch announced from Copen- hagen that the atom had been divided ties involved in the discovery of atomic uranic elements, Drs. Lise Meitner and devices which succeeded experimentally. The news came in a fission are the electronic Otto Hahn of Berlin actually made that discovery possible. The neu- in splitting atoms. Fortunately for the letter from Frisch to Professor Bohr, head of Copenhagen's Institute of tron itself is produced by bombarding future of the world, they did not fully atoms with heavy particles of hydrogen. understand at once what they had done. Theoretical Physics, who was also a police had visitor to New York at the time. The cyclotron in which this bombard- Meanwhile the Nazi secret ment takes place is thus one of the most discovered Dr. Meitner's Jewish an- Drs. Fermi and Bohr determined to leave check the results themselves, and ar- powerful of all atomic fission research cestry, and she found it wise to weapons. the country. Spending some of her new rangements were made to repeat them leisure time in calculation (some say on at Columbia. There, on the 25th of Jan- In its simplest terms, a cyclotron is a the train which took her to Copenhagen) uary, 1939, Professor Fermi had the very large vacuum tube with a pair of Dr. Meitner realized that the results satisfaction of seeing his slow neutrons hollow dee- shaped electrodes connected to a circuit oscillating at a high radio frequency. Heavy positively-charged

GAMMA OR OTHER RAY ions of hydrogen (deuterons) are introduced into the tube from outside, and are aas attracted first by one of the electrodes, wine then the other, as the oscillating field METAL CYLINDER changes in polarity. The whole tube is PULSE ON TAPE situated between the poles of an enor- RESULTING IONIZATION RECORD EIGER OZUNTER TUBE BYTES TUBE CONDUCTIVE mously strong magnet, whose field is in such a direction as to push the deuterons at right angles to their course. The result is that they travel in circles of increasing diameter. Each time they leave one dee and enter the other, they are speeded up by the. at- traction of the voltage ahead of them, caused by the ri. field which changes polarity in step with the progress of t PULSES OBSERVED the particle. Before the end of their AMPUFIER ON CATHODE RAT TUBE D.C. SCREEN veritable RFCTIFlERI course they have become (PROM atomic bullets, or better, super -speed battering rams, ready to -knock elec.- Simplified representation of a Geiger counter using cathode -ray oscilloscope as indicator. for JUNE, 1947 22 RADIO -CRAFT trons, protons or neutrons out of the atoms they strike at the end of their path. Another special type of electron tube much used in nucleonic search is the cathode -ray oscilloscope. The first news of atomic fission was flashed on a cathode-ray tube screen, in the form of voltage indications so high that no known force could have produced them. The scientist (Frisch) looking at the screen knew he could be seeing only one thing -the energy liberated by atomic fission. The Geiger -Muller counter If the cyclotron is a greatly- modified vacuum tube, the Geiger -Müller tube is a very ordinary one. It has been pub- Beam of deuterons emerging from the U. C.'s Laboratory licized to such an extent as to be pos- of Crocker Radiation cyclotron. sibly the best -known piece of atomic research equipment. Well known as a Free electrons immediately move toward ing voltages, the counter may be made safety device to check radioactivity in the central filament, knocking more to register one type of particle and ig- factories which produce atomic fission electrons from the atoms they encounter nore others. materials, the terrain surrounding on their way. The ions thus created drift One of the most important types of atomic bomb explosions, and similar toward the outer shell, and the electrons Geiger tubes counts slow neutrons. The areas, it is more important as a research reach the central wire and create a tube is filled with boron trifluoride gas instrument, and its invention was one brief pulse of current in the external and the voltage is adjusted within cer- of the notable steps in the advance of circuit. The positive ions either reach tain rather critical limits. The pulse nucleonic science. the outer shell or recombine with elec- produced by a slow neutron is then much In its most common form, the tube is trons from other atoms, and the gas is stronger than that produced by any a small metal cylinder with a centrally - again free from ions, ready for another other type of particle, due to the reac- located wire, filled with various gases "count." tion with the atoms of boron trifluoride. and pumped to a low vacuum. A high By properly designing and adjusting The counting circuit may be adjusted to voltage is set up between the elements, the counter and its associated circuits, select pulses caused by those slow neu- with the central wire usually acting as it may be made particularly responsive trbns and ignore the other particles. It the anode. Now any stray electron or to certain types of particles. Thus one is hardly necessary to comment on the negative ion will be attracted toward tube may have a heavy metal shell value of such an instrument in view of the filament -like anode, as in any other which stops anything but cosmic rays. the crucial importance-of the slow neu- vacuum tube, and will appear as a cur- Another may have a thin window to tron in atomic research. rent in the external circuits. facilitate entry of weak, short -range The voltage is held below the critical emissions. Some Geiger tubes have even Standard vacuum tubes point at which the gases in the tube been made to operate in open space at The Geiger -Müller tube was invented would ionize and produce a cold- cathode atmospheric pressure, with no envelope. before amplifiers came into general use. current (as in neon tubes and such recti- A steady stream of helium gas from a Its usefulness on its present level dates fiers as the OZ4 or the old Raytheon pressure tank directed between the two from the day its output was fed to BH). A particle from outside (electron, plates provides the type of gaseous at- vacuum tubes for amplification. With proton or neutron) plowing through the mosphere required. sensitive amplifiers, the tube may be gaseous atmosphere of the tube, leaves By selecting the type of envelope, the made to record on a tape or otherwise a trail of ionized particles behind it. gas content of the tube and the operat- (Continued on page 53)

BOMBARDMENT CHAMBER SECTION OF DEES HELICAL PATH MAGNET OF ION, STARTING COIL AT 'A' ORDINARY PATH Or PARTICIoi

AIR -TIGHT _NAT IVE CHAMBER CHEGARGE THIN ALUMINUM FOIL WINDOW \ DEFLECTION PLATE c=14-* (IF BEAM IS TO PASS INTO AIR. (ATTRACTS BEAM) MAGNETIC PATH OF WITH BLUISH FIELD ION ORBIT GLOW ) 'TARGET' TO BE BOMBARDED PLACED HERE

TARGET OSCILLATOR PLACED I. 1+,1 HERE

WINDOW

BOMBARDMENT METAL CHAMBER TWO HALVES (DEES) INSULATED FROM EACH PATH OP ION OTHER WINDOW \ GAS INLET TOP VIEW OF DEES MAGNET COIL.

How the cyclotron works. Size of the magnets has been kept down to show does path of the electron. See photo above for their Prue size.

RADIO-CRAFT for JUNE. 1947 23 slipped into a package the size of a man's ordinary wallet. Since arrange- ments can be made to insert batteries in flashlight manner, reserve battery flEUJ SUBfflIflRTURE capacity is usually unnecessary. Jobs for subminiature sets For many uses, such as when taking inventory in department stores and speaking in public, two -way conversa- PRIflTED CIRCUITS tion is unnecessary. In such cases the portable unit consists only of a trans- PRINTING of electronic circuits is audience at the National Convention of mitter madé up of a tiny battery pack, one of the important new tech- the institute of Radio Engineers in New a subminiature tube with circuit paint- niques to evolve from research and York City, March 5, 1947. The transmit- ed on its envelope, and a tiny crystal development daring the war. The ter is plugged into a comparatively microphone. The microphone conceivably practicability of the printing technique heavy -duty power pack, while the could be clipped to a man's tie with a was first demonstrated in a program car- standard size carbon microphone with pair of light wires leading to the re- ried on by the National Bureau of matching transformer is plugged into mainder of the unit, which may be Standards leading to the development the other end. The 2 x 3 -inch receiver housed in a package slightly larger than of a tiny generator -powered radio prox- mounted on the 10 -inch console speaker a penny matchbox and carried in the imity fuse. .A paper written by Dr. had sufficient power to operate the user's shirt pocket. The transmitted . Cledo Brunetti and W. J. Cronin, of the speaker so that it could be heard clear- voice may be picked up on a standard Bureau, describes construction methods ly throughout the crowded auditorium. receiver in an adjoining room and fed and shows circuits of a number of-very Logical auxiliary components for a to a recording unit, to loudspeakers of small transmitters and receivers made portable unit would be a set of small an auditorium, or to any desired repro= by the printing method. This article is hearing -aid batteries and a miniature ducing system. . largely an abstract of that paper. Since crystal speaker or hearing -aid type of In other cases, where distance of the war the art has advanced to the earphone. If the .combination is to be transmission is small or where conver- point where complete circuits may now used as'a personal telephone, the trans- sation between a variable point and a be printed not only on flat surfaces but mitter and receiver may be combined to fixed high -power transceiver is desired, on cylinders surrounding a radio tube or operate with the on the tube envelope itself. same set of minia- Several types of miniature micro- ture batteries. In phones, speakers, and batteries are this way a very available as suitable components to com- compact "portable plete the operating units. The units also unit is possible, operate satisfactorily with standard size which, including microphones or speakers. The transmit- batteries, micro -" ter and receiver of Photo A were set phone, and speaker, up for demonstration before a large may be easily /$ Photo A, below-Ten -inch console speaker operated by tiny 3 -tube receiver. with signals from lipstick transmitter, shown plugged into its power pack. Photo B. right, top-A series of lipstick transmitters: below-Development of a printed -circuit iteatite -plate transmitter.

24 RADIO -CRAFT for JUNE, 1947 the complete portable unit could be ex- high dielectric ceramic capacitor, 3¢ inch tremely compact. An example is the case in diameter by 0.030 -inch thick. It is in which a field crew maintains contact attached directly to the tube in Type I. with a base station or with mobile units, M is a carbon microphone and -T is a such as trucks or aircraft carrying mod- miniature microphone transformer. R is erate- powered transceivers. In another 60,000 ohms in each transmitter. Plate application, such portable units would current in both sets is 3 ma and filament dispense with the usual flagging meth- current is 0.2 ampere. ods of lining up commercial aircraft Type I uses a Sylvania 6K4 triode, after landing or in assisting planes tak- with 6 volts on the filament. Micro- ing off or landing on aircraft carriers. phone battery V is omitted, since the Personal radiotelephones could be valu- 6 -volt filament battery is sufficient. Lg able in many applications -for example, is 4 turns and Lp 5 turns, of silver paint in factory and store, on farms, and by on the tube, as can be seen in Photo B. surveyors, hunters, and explorers. In The 50,000 -ohm resistor is also painted addition there are numerous applications on the tube, with graphite paint. in crime detection and traffic regula- A battery -type Raytheon subminia- tion, in limited ship -to -shore communi- ture triode is used in the transmitter of cation, and in emergencies such as Type II, which has its circuits painted forced landings or isolating floods. on a steatite cylinder slipped over the A simple 2 -tube unit consisting of an tube. Battery voltage A is 1.5, and an oscillator and amplifier stage may suf- additional battery V of 4.5 volts is added fice for these applications. One such unit for the microphone. Lg is 3 turns and constructed at the Bureau employs a Lp 6 turns painted on the cylinder,. a1: microphone operating into an amplifier approximately 16 turns per inch. The which modulates an oscillator coupled cylinder is 1 inch long, % -inch outside to an antenna. Pressing a button con- diameter, and 1/32 -inch thick. verts the unit to superregenerative re- The Type III transmitter (Fig. 2) is ception. For receiving, a magnetic ear- large by comparison, being printed on a phone may be operated from the ampli- flat steatite plate 1% inches high by the fier stage. same width at the bottom. It is shown in the lower section of Photo B. The Lipstick transmitters battery -type triode with 1.5 volts on the Figs. 1 and 2 are the circuits of the filament is used in this set, and the first four transmitters of Photo B. They coils are spiral -wound (painted) on the operate in one of the Government bands plate. (Old -timers who saw the helix -132 to 144 me -and were used in pub- go out forever in the '20s will reflect lic demonstrations at Columbus,. Ohio, that there is indeed nothing new under and New York. On at least two instances, the sun!) Lg and Lp are 4% turns each, these subminiature transmitters "went "wound" to 7 -16 /inch outside diameter, on the air" over national networks with and La is 5% turns, % -inch outside excellent results. diameter. Frequency of the transmit- The sets of Fig. 1 are made in two ter is 140 me and that of tubular trans- types. The circuit is painted on the tube mitters is 136 mc. envelope in Type I, and on a steatite cyl- The lower part of Photo B shows the inder surrounding 'the tube in Type IL development of the flat -plate transmit- Sylvania or Raytheon miniature triodes ter (both sides). The upper side carries are used for both types. In both trans- the three spiral coils and a 50 -µµf cou- mitters, B is 120 volts, and C is a 7.5 µµf pling capacitor. The lower side bears the remainder of the circuit wiring, including three resistors (the dark rectangles) and four capacitors. One of the resistors, though not shown in the circuit diagram, is connected to the grid coil. It serves as a blocking resistor for measuring the oscillator grid voltage. The receivers in Photo C are wired with the circuit in Fig. 3. Two of the units shown in the photo are on steatite plates 2 x 3 inches (bottom) and 2 x 5

inches (center), respectively, while the . third is on a 2 x 6 -inch lucite plate. They employ a square -law detector stage followed by two stages of pentode amplification and a triode output stage feeding Photo C -Front and rear of three flat receiv- the loudspeaker. The input tuning is ers, printed on steatite and lucite bases. Fig. I- Circuit of the lipstick transmitter. broad to allow reception over the complete band of 132 to 144 mc. If sharper ver paint consists of powdered silver in 2.2H L Sept ANT.`f' tuning and additional sensitivity is de- lacquer solution, the consistency, being 0201/11uµf .,.SOnyf sired, the input stage may be converted adjusted with an acetate. solvent. About 000 to one employing superregenerative de- 65 per cent of silver powder is used. Sil- 47K Lg Tuul tection. ver plating is found to increase the con- ductivity of the painted coils. Painting the circuits A resistor paint which dries at room M 250uuf HI-, Several types of paints were used, 'temperature may be made of 27.5 per- 3r most of them obtainable commercially. cent graphite powder, 34.5 percent A satisfactory silver preparation is a methyl -methacrylate lacquer, 29 percent m ilv sodium -silicate paint known as Sauerei- toluene and 9 percent lampblack. More

Fig. 2-Schematic of flat -plate transmitter. sen Conductulnte. Another suitable sil- (Continued on page 65) - RADIO -CRAFT for JUNE, 1947 * * * * * * * * * * * * * * * * of October 9. Actually, the rate of the shooting stars climbed from about 8 per hour between 7:30 pm and 8:30 pm to a "5400ter, Ste. maximum of more than 1 per minute ?Jaded Rada

By S. R. WINTERS * * * *

NOT being content with having S. R. Winters, who claims to be "the oldest transmitted signals to the moon, Professional Writer on radio subjects" in the radar researchers are now con- United States, was born on farm In Gran- tacting shooting stars as they ville County, N. C. Bright traces on screen are meteor tracks. . plummet to earth! Or, more accurately Starting We as bookkeeper and freight handler, he learned the Morse Code and be. stated, the National Bureau of Stand- came station master in a small station. Later between 10:30 and 11 pm. The recorded ards is employing radar as a means of he worked his way through the University of facts coincided with the anticipated studying ionization produced by show- period of 10 o'clock for the greatest in- ers of meteors as they shoot through tensity of the Draconid comet shower. space. Following this peak, the rate of occur- On scopes or screens of radar equip- rence dropped to about 20 meteors an ment at the Bureau of Standards' sta- hour after 11:15 pm. The distance tion at Sterling, Virginia, echoes from range was from 60 to 209 miles. The the meteor shower identified with the transient radar reflections lasted gen- Giacobini- Zinner comet were plainly erally about 1 second or less, although visible during a 5 -night period between an appreciable number had a duration October 7 and 12, 1946. The signals were of several seconds. The - Bureau . of intercepted by a standard Signal Corps Standards reports .that only a few of 'SCR -270 -D radar outfit, functioning at the signals seemed to change distance 107 megacycles and sending 25- micro- during the period that they could be second pulses at a rate of 400 per sec- North Carolina as printer, aleo by writing seen on the screen, and this slight shift ond. The maximum power employed was sketches on scientific and biographical sub- was only 5 miles or less. 100,000 watts. The radar antenna, com- jects connected with the University, thus bw Simultaneous but independent ob- posed of 32 dipoles arranged in a rec- ginning his career as scientific writer. Began writing on radio telegraphy before servations were made by the Signal tangular fashion, was adjusted at an broadcasting started, publishing articles in Corps in New Jersey, employing radar azimuth of 315 degrees and at a height Wireless Age and later in Radio News. Since sets at a frequency range of 600 to 1,000 of 45 degrees. The width of the main then has contributed to practically all the megacycles. Results were apparently beam of the antenna was about 40 to radio and scientific publications In the United States, his articles having been published in negative. But according to an appraisal 20 degrees between half -power power more than a hundred magazines and papers. of the Bureau df Standards, in final points. The major axis was vertical. analysis these negative findings were Radar signals were viewed on both the significant in that they suggested "that A and PPI oscilloscopes. A photographic operated by an experienced technician, the ionization density reached in these impression was kept of the PPI mani- who maintained a record of the time, meteors is such that the upper limiting festations. The A scope or screen was range and duration of the pulses. The frequency which they could reflect is be- shower of meteors, tween 100 and 600 megacycles." according to a Detecting meteors by radar is not forecast by astron- merely a spectacular "show ". This radar omer s, was ex- investigation of meteors is being made pected to attain its because of the probability that meteors peak on the night (Continued on page 72)

Receiver console and antenne of the SCR -270 -D rader used by the Bureau of Standards to track meteors. The hooded equipment is the cernera. 26 RADIO -CRAFT for JUNE, 1947 ANTENNA PRINCIPLES PART VII - -- Parabolic reflectors as antennas By JORDAN McQUAY

eral structural difficulties. At "shorter To concentrate all radiated light into wavelengths (or at higher frequencies), the parabolic reflector, a very small entirely new systems of microwave hemispheric reflector is used (Fig. 1) transmission are necessary. to prevent outward radiation from the Progressing downward, in terms of point source of light and thus limit the wavelengths, there are three principal beam to the desired parallel waves. types of such systems. The analogy with microwaves is Parabolic re debtors are the most identical. They can be reflected and widely used means of transmitting and focused exactly as in Fig. 1, using a receiving microwaves in the region be- rotational parabola as a reflector between about 30 centimeters and about 3 hind a source of u.h.f. radiation. When centimeters. the source is situated at the focal point Electromagnetic horns function in the of the parabola, a narrow beam of region between about 20 centimeters microwave energy can be directed to- and 1 centimeter. Theoretical rather ward a similar receiving parabolic de- than practical, use of such horns is vice. U. S. Army Signal Corps Photo largely confined to the experimental The reflector should be at least 10 Photo A -An antenna for 10- centimeter waves. laboratory. However, some are used to wavelengths from edge to edge. feed parabolic reflectors. The antenna in Photo A operates at DIRECTIONAL antennas operat- Metal lens systems newcomers to a wavelength of about 10 centimeters, region - ing in the true microwave the microwave field -are practical for and is . used for the transmission and -at frequencies higher than operation in. the region between 10 cen- reception of radar pulses. The complete 1,000 megacycles -take on phys- timeters and less than 1 centimeter, pro- equipment is used by the U. S. Army ical and electrical aspects entirely dif- viding extremely narrow beams of for tracking down aircraft, and a con- ferent from those operating at lower microwave energy. siderable part of its accuracy depends frequencies. upon proper functioning of the antenna Radio waves only a few centimeters Parabolic reflectors in length have many of the character- A highly directional beam -for radi- istics of infra -red light waves. They are ating and receiving quasi -optical micro- T.- reflected by almost any surface or ob- waves- follows the laws of optical re- 4- --,-- ject with little or no loss of power. The flection. waves may be refracted by differences Light waves are so reflected from a -ififroF PARALLEL REGION OF smooth mirror surface that the angle FOCAL POI T + S REFLECTED WAVES in air layers between transmission f1?- - --- points, or by reflected impedances along made between the reflected wave and LTL _ a transmission path. Many.of the prin- the surface is equal to the angle made ciples of optics -particularly laws gov- between the incident wave and the sur- -'- erning the operation of lenses -are ap- face. plicable to microwaves. After being A concentrated beam of parallel light ARABOLIC REFLECTOR focused into a narrow beam of energy, waves is formed when a point source of Fig. I -How waves are reflected by parabola. microwaves can be propagated from light Is surrounded by a mirror -surface point to point like a narrow beam of of such shape that -due to the above system. A dipole radiator is contained light. Microwave antenna systems make law of light reflection -parallel waves in a small weatherproof enclosure at the use of all these quasi -optical properties are produced in a very intense and di- focal point of the parabola. And the of centimeter waves. Microwave propa- rectional beam. entire antenna iystem can be rotated gation -from po'.nt to point -is always A reflecting surface satisfying this and moved in elevation to provide high along direct or semioptical paths. There requirement is a rotational parabola power gain in any direction. is no ground wave. And the sky wave (Photo A), a type of mirror having (Continued on following page) is of no practical use in propagation. an axis and a fo- The usual laws of antenna reciprocity cal point. The fo- apply to u.h.f. technique: a good radia- cal point is located tor or transmitting antenna is a good along the center receiving antenna. Both function more axis of the para- than 30 or 40 wavelengths above ground. bola. Thus, microwave antenna systems can . When a source of be considered as operating in free space, light is situated at without ground effects. the focal point, all Polarization is important only in that light waves inci- both transmitting and receiving-systems dent on any part of must be identically polarized. In prac- the parabola will tice, horizontally polarized microwaves be reflected in such are more generally used. a way that they Directional antenna arrays* are in- travel outward, adequate for operation at wavelengths parallel to the axis less than about 30 centimeters (fre- of the parabola quencies greater than about 1,000 meg- (Fig. 1.) T h e acycles)-because of the close proxim- source of light ity of elements of the array and gen- waves must be small to obtain a British Official Photo *Discussed in the April and May issues of RAD[O- CaArr. well- focused beam. Photo B -Twin reflectors used in 9- centimeter anti -aircraft radar. RADIO -CRAFT for JUNE, 1947 27 structural supports and rotational gear against reflecting portions of the para- for moving the antenna in azimuth. bolic surface. The resulting directional The inner or reflecting surface of any (output) pattern, however, is deter- parabolic reflector must be metallic - mined largely by the physical shape and preferably copper or other highly con- dimensions of the reflector itself. ductive metal. Small parabolic reflectors A very narrow sectional parabola is may be constructed of any solid used on the flying bridge of the British weather -resisting substance, provided liner Queen Elizabeth (Photo E), pro- the inner reflecting surface is smooth viding a short -range but high- definition and coated with copper or other con- searching beam for the ship's radar ductive metal. However, the presence of equipment. The parabolic reflector func- holes or perforations in the reflector tions on about 7 centimeters, and is fed does not alter its effectiveness, if such by a conventional wave -guide system. apertures are no greater than Mt wave- The radiation pattern is narrow in the length in diameter. Thus extremely horizontal plane, much wider in the ver- large parabolic reflectors (as in Photo tical plané, making the antenna system C) can use any sort of wire mesh or useful for precision sea-search radar. screen meeting these aperture require- A long -wave long -range radar for de- ments. tecting and locating aircraft uses a British Official Pho o Perforations, holes, or openings- parabolic antenna, and completes the Photo C-A 35 -foot parabola for 50 -cm waves when no greater than wavelength - radar installation on thé Queen Eliza- do not detract from the operation of the beth. parabolic reflector. They serve princi- An "open" sectional parabolic reflec- pally to minimize wind resistance for tor (photo F) is used with Western certain outdoor installations, or when Electric radar designed for American sheet metal may not be available or desirable. Other parabola types A reflector consisting of a rotational parabola (A in Fig. 2) is circular in shape when viewed along its axis, and concentrates energy almost equally in all planes. Thus the horizontal and vertical radiation patterns are practically similar in shape -providing almost U. S. Army Signal Corps Photo equal directivity in both horizontal and Photo D -A modified- parabola radar antenna. vertical fields. To concentrate a high percentage of the u.h.f. energy in either the horizontal or vertical field, a cylindrical parabola (B in Fig. 2) is used -having a focal line instead of a focal point. A cross section of this type of reflector appears as a parabola in only one dimension- Photo by Western. Electric,

and that dimension is the plane of great- Photo F-Radar antenna for merchant marine. - est directivity of the u.h.f. beam. Often ships, now in service on inland water- the open ends of the cylindrical para- ways. This is just another of the endless bola are closed to provide slightly great- variety of shapes and sizes of parabolic er power gain. reflectors. Other variations (C and D in Fig. 2) consist of narrow sections of rotational TYPE OF REFLECTOR PLANE OF FIELD PATTERN parabolas, having closed ends or closed HORIZONTAL' sides. These are known as sectional parabolas (sometimes called cheese - AD VERTICAL British Information Service boxes!) and are found in an extreme ROTATIONAL PARABOLA Photo E -Radar antenna on Queen Elizabeth. variety of sizes. They provide extreme directivity in A pair of 'dipole -fed parabolic reflec- particular planes of the radiation pat- tors (Photo B) are used in British anti- tern. In general, the beam width is in- aircraft microwave radar equipment, versely proportional to the width of the operating at a wavelength of less than sectional parabola. And the resulting HORIZONTAL 8 centimeters. One transmits u.h.f. radiation beam is sometimes known as pulses, the other is used for receiving. a "fan" beam. LINDRICAL PARABOLA parasitic Parabolic reflectors are restricted Often elements are added VERTICAL normally to wavelengths of less than to one of these parabolas to further im- about 10 centimeters. However, a num- prove or in some way influence the pat. ber of systems were developed during tern of radiation according to some par- the war which operate as high as 40 or ticular microwave requirement. Such an 50 centimeters, with corresponding in- antenna (Photo D) provides a beam of HORIZONTAL J crease in the physical size of the struc- extreme directivity for radar searching -KI` ture and components. One such arrange- purposes, but the beam in the vertical ment (Photo C) is the antenna system plane is affected by the parasitic (lower VERTICAL SECTIONAL PARAR. / used with fighter -director radar and cylindrical) element so that none of the ground -control equipment by the Royal energy is dissipated downward. HORIZONTAL Air Force. The antenna is a dipole -fed Sectional parabolic reflectors are gen- parabolic reflector 35 feet in diameter. erally fed by an open -ended wave guide An almost-invisible screen is used as or by an electromagnetic horn terminat- DI VERTICAL the reflecting surface of the parabola. ing a wave -guide system. Either method SECTIONAL PARABOLA Remainder of the antenna consists of provides a "spray" of u.h.f. energy Fig. 2- Special parabolas and their patterns. 28 RADIO -CRAFT for JUNE, 1947 NOISE lìLlr[1 \'A'l'IOv By JACK KING noise pickup will be strong, and when the application of a heavy-duty filter to the loop plane is at right angles to the the sign to cut down the noise. source, minimum noise will be heard. The basic circuit of a simple filter is When the approximate' direction of the shown in Fig. 1. In some cases the high - NOISE in many receivers, particu- noise source is known, the field is nar- voltage transformer may develop leak- larly in large cities, presents one rowed down considerably and time is age and the leakage current may result of the serviceman's hardest jobs, saved. in getting the noise out of the In some cases, a little adroit' ques- radio, or in reducing it to so much lower tioning may lead directly to the cause. mV.At TO NEON SIGN level that the customer can notice a de- If the customer states that it is heard cided improvement. only at definite times of the day or night, -GND TO COLD WATER P PE If the noise is in the receiver the job the time is a clue. If the noise is heard Fig. I- Simple filter. Try 600 -volt' condensers may not be very difficult, but if it is due only when a telephone is dialed or a from .01 to 2 µf, smaller sizes first. to external causes getting rid of it is refrigerator swings into action, the likely to be a difficult matter. sources are perfectly obvious. If trouble in excitation of the distributed L and C One of the best ways of attacking the appears only when the drugstore down- to produce damped oscillations. Replace- problem is to listen to the noise. Make stairs is open and its neon sign is lighted, ment of the transformer will get rid of an effort to identify the noise generator it requires no great stretch of the imag- the noise without a filter in such cases. by its characteristic sound. Vacuum ination to decide th4 the neon sign is If the filter is used, the radioman will cleaners produce a sort of whining or causing the trouble. This can be checked often find it more practical to get an whirring noise, electric razors produce with the druggist's cooperation. electrician to install it with BR cable a series of loud sputterings much like It is good practice to take the portable and a box rather than attempt to handle an old -time spark transmitter, and neon receiver with you to check the sign. If the heavy wiring himself. Of course, if signs and various other types of devices the noise dies out on it when the sign you have an electrician's license you can produce sounds which, with experience, is shut off, it is probably defective and do it Yourself. can be identified. For example, the noise should be gone over by a sign man. Sometimes a human problem is in- of a d.c. motor is easily recognized once Usually the owner of the sign will volved. The whole neighborhood may be it has been identified and associated. listen to reason and will be glad to do bothered by the noise, but no one wants A small portable receiver, battery- anything practical if not too expensive to pay to get rid of it. If a number of powered and equipped with a loop an- to get rid of the interference. In 'some people chip in and present the owner tenna, may be used to run down the cases this may involve merely having of the sign with the filter, he will usual- noise. When the loop is in the same plane the sign company put the sign in proper ly cooperate by letting it be installed- as a line drawn toward the noise source, working order. In others it may call for (Continued on page 62)

a. } s ;} CARS MOTOR TELEVISION SET e STREET",. CARS

\iiEE,FRIGERATOR ,,. < J.x TELEVISION SET S D `-/_111!! Ei?IL EL

HEATING PAD

POLE TRANSFORMER

Just a few of the many types of interference with which the serviceman must contend. Even television sets often interfere with each other. RADIO -CRAFT for JUNE, 1947 29 stage must be completely shielded and its tank must be high C in order to obtain a high -Q circuit. At 80 meters about 500 µµf of capacitance should be available. With such a high -C tank, changes in resistance or capacitance in the following stages have little effect on frequency. Likewise, mechanical disturbances such as table vibration are negligible, because the large tank capacitor masks the effect of minor changes in capacitance. In precrystal days, the large capacitance was made up by an enormous variable condenser, often of 1,000 -µµf maximum capacitance. The modern method is to use a fixed capacitance as well as a variable condenser. This is possible only when low-temperature-coefficient w condensers (ceramic type) are used. Even in a well -designed transmitter, there will be a slight reaction on the oscillator from succeeding stages. There- V.F.O. EXCITER fore all stages should be of rugged construction with short, direct wiring. OK TRANS3fITTER Isolation precautions The oscillator must be carefully iso- lated from other stages and from an- Part I- Variable- Frequency Oscillators tenna radiation pickup. A strong field will block the oscillator and cause a chirpy note on continuous wave. Com- 1I' By I. QUEEN, W2-OUX pletely shielding the oscillator will eliminate this difficulty and will prevent direct pickup from succeeding BEFORE the introduction of quartz tals and switch in the one that gives the stages. crystals, all transmitters were con- best opportunity for QSO at the time. The oscillator frequency may be as trolled by variable- frequency os- There is no question about the su- stable as that of a crystal when no load- cillators. The advantages of the periority of the crystal transmitter ing is present. When buffers and ampli- crystal oscillator over the old Hartley where stability is concerned. It.is simple fiers are added, their loading effect may or tuned -plate, tuned -grid circuit were to design, especially since harmonic type vary (as during tuning). Even slight so great that the crystal reigned su- crystals have become available. A single changes in antenna loading caused by preme for a number of years. tube can give an output at 15 or 20 swinging may be fed back through am- With the increase of QRM which has meters, to be further divided as desired. plifier stages to cause a corresponding come with the great upsurge in the A v.f.o. requires 2 or 3 stages to obtain frequency change. It is good practice number of operators on our narrow the same output as that of a crystal therefore to follow the v.f.o. stage with bands, even a transmitter with several stage. Turning a dial to reach a desired at least one class -A buffer, in which the crystals cannot guarantee a clear chan- frequency is not as easy as throwing a grid never goes positive and therefore nel for a reasonable part of the time. switch. The variable-frequency oscilla- does not take any power from the oscil- Many hams have turned again to the tor usually is designed to operate at 80 lator. variable- frequency oscillator (v.f.o.) as or 160 meters and this requires a whole Reaction on the oscillator may take a solution to the problem. Of course the row of doublers or quadruplers to reach place through grid -plate capacitance modern rig is incomparably more stable the higher frequencies. Any. slight in- coupling in the buffer tube. Best buffer than the old self -excited transmitter stability (such as chirp or drift) is then action is obtained by using tubes which circuit. multiplied by the order of the harmonic. have a low grid -plate capacitance. Type We have built and operated several Some hams have been quick to adopt 802 is one of the best for this purpose, v.f.o. transmitters here at W2OUX dur- and keep v.f.o. technique, while others but it is expensive and is not available ing the past few months. This means of maintain that crystal control is far su- as a surplus item. Fortunately, the 6F0 frequency control has a number of defi- perior all around. This difference in is also excellent, its capacitance being nite advantages. The disadvantages are opinion is reflected in modern amateur only about half that of the beam tubes equally definite, and at first glance seem transmitters, both commercial and home - 6V6 and 6L6. Beam tube 807 is rather far more numerous than the advantages. built. Some are designed for exclusive - large for a buffer but it makes a good Fortunately these problems can all be crystal control, others feature v.f.o. con- final or exciter for a higher -power final solved very satisfactorily, and the few trol; with crystal control as optional in because it has a low capacitance. advantages far outweigh all the disad- other cases. A 3- stage, highly stable vantages combined. v.f.o. rig is now being operated at Tone quality

Variable- frequency control is at . its W2OUX with very satisfactory results. Under ordinary conditions the output best in a simple, low -power rig. These Reports are "T9 crystal" and the tuning of a high -C oscillator with an amply suffer first and worst when QRM begins is as easy as with any crystal rig we filtered power supply will be T9X, but to cover the band, but a highly "mobile" ever built. This transmitter will be de- conditions are not always `ordinary" frequency permits change in frequency scribed in a following issue. During early experiments we ran into as required. Since a channel that is clear an unusual difficulty in this respect. one minute may be hopeless a few min- Oscillator design Monitoring showed that the output of utes later, quick tuning is necessary. The basic difference between the two the v.f.o. rig was "crystal" until an an- There is no advantage in frequent retun- types of control is in frequency stability. tenna was connected. The quality then ing if "umpty" amplifiers, doublers, or Mechanical and electrical disturbances dropped to a rough, modulated T7, al- quadruplers must be resonated each have little effect on a quartz element, though a crystal rig set up alongside time. In a multistage transmitter it may but special precautions must be taken and using the same -power supply sound- be better to incorporate 10 or more crys- with self- excited oscillators. The v.f.o. (Continued on page 51)

30 RAOIO -CRAft for JUNE 1947 Vat& S(xet 14e4

By WILLIAM HEDRICH '

THREE tubes are used to give full \ 4 -tube results in this small portable superhet. Operating on but one The little set, built small 45 -volt B- battery, and two on a base 8 x 3 in- flashlight cells, this set makes an ideal ches, is well laid out. vacation companion, regardless of how While number of tubes you lines. far are from the power is low, this circuit The little set was designed around often gives excellent the three following modern battery- results. A little re- type tubes, requiring a plate and screen generation may add to potential of only 45 volts: 1R5 as mixer- oscillator; 1T4 as i.f. amplifier; sensitivity greatly. 1D8 -GT serves as 2nd detector and 1st and 2nd audio stages. The battery drain is very low, A drain being 200 milli- scriber. Never use an ordinary pencil "must" in a set of this small size. Usa amperes, and B drain being about 7 for this work, as the sharp point will a good grade of stranded hook -up wir: mils. The set makes an ideal personal wear away, causing inaccuracies. Be and keep all grid and plate leads as portable for the beach, the summer cot- sure and center -punch all holes before short and direct as possible. Be espe- tage or picnic. It also makes an ideal bi- drilling. Bend sheet back 11 inches cially careful in soldering to the small cycle radio, using a fishpole automobile - each side, to give a finished base 8 miniature tube sockets used to sup- type aerial. In this case use the bike inches long x 3 inches wide x 11 inches port the 1R5 and 1T4 tubes. Use onl frame as a ground. high. enough solder to make a good sour I A piece of sheet steel or aluminuni, Mount all the parts before doing any connection, and do not let solder t 6 x 8 inches, serves as a chassis. The wiring. This will save your temper if rosin run over to adjacent terminal:. author used 20 -gauge aircraft alumi- later on you find that the volume con- Grounds are made to soldering lug num, which was very satisfactory. It trol has to be removed and the oscilla- placed under screws. Stick to the la} - is well to lay out and drill all holes tor coil put in first. out as closely as possible, as this wi.l before bending the sheet. Lay out the Standard parts are used throughout. permit short leads. There are no coil ; various lines on the chassis with a Any 'good set of antenna, oscillator, to wind, and either a buikt6n loo, sharp -pointed instrument such as a and i.f. coils will work. Those on the aerial or a midget antenna coil ma/ set were Meissner 14 -1022 antenna, be used. 14 -4034 oscillator, 16 -6658 input and Wire the set in the conventional mar- 16 -6660 output i.f. transformers. A ner- filament circuits first, then griì 2 -gang 365 -µµf variable condenser with and plates. Although there is no tria: trimmers is used, and the padder con- in wiring or building this little set, it i ; denser has a maximum capacity of well to take your time, unless you al , 350 µµf. familiar with wiring multitube circuits. Good soldered connections are a (Continued on page 71) 1R5 IT4 1D8-GT ., DET;OSC. - I.F. AMP. 2ND DET. IST d .025 2ND AUDIO

I.F. TRANS I.F. TRANS. %T

2MEG IMEG

500 II.F.456NC1 5011 .005

GANG_ 12 !MEG 10MEG# 365Npf .I /200V 125-350upf PAVER 25 T 50V. 3MG D.P.STSW.ON

11.5 V. (t Bti45V. 8-

Under -chassis view of three -tube superhet. Schematic of the receiver. Fixed bias used with the I DB output tube improves quality. RADIO -CRAFT for JUNE, 1947 31 A Small Recording Studio

ers, and by moving the needle in and PART IV- Operating the recording equipment. out of the chuck on others. Cutting the record Speed, needle and record cut considerations. When the angle is properly adjusted, the depth of cut should be regulated so that a 60 -40 relation exists between By J. C. HOADLEY groove and land. The rule of thumb is: make the cut as light as possible, con- sistent with the playback pickup's abil- TO insure consistently.good record- The cutting needle ity to track the resulting recording. The ings, preventive attention should be The next important consideration is chip should throw from the needle at an given to the possible problems be- the insertion of the cutting needle in the angle and lie flat on the disc at least fore they occur. First check careful- head. Sapphire and stellite needles are 1,4,-inch from the stylus (see Photo D). ly alignment of the lead screw assem- the types to use; sapphires will yield The stylus is designed to throw the chip bly and its working parts. Be sure there slightly quieter recordings and will last is no bjnding of any of the gears, how- several times longer. They come in two ever slight, as it will cause wow. It is' lengths and it is necessary to choose the feasible to use a little grinding com- proper needle as specified by the manu- pound to lap the gears into a perfect fit. facturer of your cutter. Of course, this should be done cautious - The needle should be inserted into the ly, or excessive play will be produced. chuck as far as it will go, with the flat Be sure the cutter carriage moves on the needle shank pointing forward smoothly and contains no excessive oil. where it will be engaged by the set - Be certain there is no play in the cutter screw. The flat side of the cutting point mount bearings, as even a small amount should face the back of the cutter head. may cause bouncing of the cutting head The angle of this flat with the surface -see Photo A for example of the re- of the disc should be approximately ver- sults. It should move freely in a vertical tical. The angle varies between 88 and direction, so as to follow -without varia- 90 degrees. There is a particular angle tion in cutting depth -the contour of a which will produce the quietest cut with slightly warped blank. any individual needle. This angle can be After you are sure the mechanism is found by making test cuts with no operating properly, adjust the motor groove modulation and observing the drive (if it is adjustable) until it deliv- noise by playing back the blank groove. ers sufficient power without excessive The easiest way to observe when the vibration. Adjusting the motor too tight- needle is vertical is to lower the cutter 1Y against the idler wheels on a rim - on a blank disc and observe the reflection drive recording motor causes transmist in the surface of the disc. Compare the Photo C- Alignment of needle and reflection. sion of excessive vibration and also a reflection with the needle (see Photo C). slight reduction in the speed of the turn- A slight deviation from vertical can be away from its point. If it does not, it table. Be sure that the rubber idler readily noted. Warning: Be sure that should be replaced or twisted in the wheels are clean and free from oil -see the needle does not point even a frac- chuck slightly. Photo B. They should not be over-oiled. tion of a degree toward the turning rec- The chip should approximate a hu- If they need cleaning, use carbon tetra- ord as it will immediately dig into the man hair in thickness and should be chloride or gasoline. Be sure also that record, which will inevitably tear off the about 0.002 -inch in width and depth. The the turntable rim is smooth and' clean. point of a sapphire stylus. The angle of average playback stylus has a tip with Even a small insect mashed against it the stylus is changed by raising or low- a 0.002 to 0.0025 -inch radius. It is de- can cause considerable noise and wow. ering the cutting head on some record- (Continued on page 64)

._...... ,

Photo A -The grooves near the edge indicate pickup bounce. Photo B-A bottom view of the equipment, showing rim -drive idler:.

32 RADIO -CRAFT for JUNE. 1947 Transatlantic News

From our European Correspondent, Major Ralph Hallows

"full frequency range recording!" Read "for the first time in any publication," the full story of Decca's new system. It combines sound engineering ideas II and new to raise recording to higher levels. _ HEY spell it

I I I with small letters: ffrr. 3. Transients, such as the sounds of usually towards the upper limit of their It stands for tympani, pizzicato on strings, or compass. For that reason they repro- full frequency the clean -cut notes of the cornet duce surface noise as a high -pitched range recording. are not realistically reproduced. . hissing sound. Besides its unpleasant- More important still, it stands for 4. Transients, in fact, áre often re- ness this hiss is sufficiently strong to full range frequency reproduction; produced as very unpleasant dfiown the upper audio frequencies when is for it . one thing to cut on a wax sounds, jarring on the ear. . the recording level of sound is low. disc spiral grooves which record the 5. Sound -. Hence it has been necessary when mak- whole contrasts are unduly .com range of audible frequencies and pressed: the phonograph is very ing recordings to monitor severely, quite another, . as we shall see, to find far from bringing out the real con- keeping the sound level of the music al- a way of making a phonograph repro- between ways above that of the noise; in other duce trasts fff and ppp that everything that is put on to actually occur in the course of an words contrast compression must take the wax. I admit freely that when I orchestral performance. place in the recordings. first heard of ffrr I was not greatly 6. The reproduction distorts, excited. I am much too old a bird some- of the radio and phonograph times very unpleasantly, the w.n.m worlds qyMlll%llllldllq/ll/Ulrrr to flutter blindly into decoys baited sounds of music. j with sales talk about "The Very Soul Believe it or not, most of the six de- of Music," "Reproduction That Is fects enumerated have one and the same Real," "Every Sound in the Studio origin: surface noise. It. has long been Brought to Your Home" and that kind realized that surface noise was one of of thing. On investigation the perfect the greatest enemies of the phonograph; but not until these recent researches were made was the extent of its evil influence fully grasped. Surface noise consists of impulses giving rise to purely random wave- forms, which cannot be analyzed into Fig. 3- Bottom view. A-coil; B- magnets: any combination of sine waves. It is, C- armature; D-- sapphire; E- milled screw. in fact, the sound -wave counterpart of static and its effects on a pickup are Until comparatively recently no reo- similar to those of static on an antenna. ord contained any worthwhile amount Fig. 1- Pickup is 13/4 x 3/4 x % inches. Static, as you know, shock- excites an of frequencies above 5,000 cycles and reproduction promised is too often antenna, causing it to oscillate at its few radio' phonographs were able to found to depend upon a.f. amplifiers natural frequency. Surface noise shock - bring out audio frequencies even as high with a complete cut -off at-or below 5,000 excites a pickup making it produce a as that. The reason is simply that a bet- cycles, a false bass produced by cabi- strong response at any frequency at ter response at the upper end of the net and other resonances, and harmonic which it has a resonance. scale would- have meant giving greater distortion -second and (far more dis- prominence to surface noise hiss. tressing) third- ranging from 10 to 15 In theory the proper reproduction of percent or more. transients can be obtained only if all I am the first technical writer to have the harmonics right up to infinity are the opportunity of investigating the present. In practice perfectly acceptable British Decca ffrr system. I approached reproduction is had if the harmonics the investigation in a distinctly sceptical within the audible range -say up to frame of mind, but before it was ended 15,000 cycles -are. brought out. But I was convinced' that they have tackled transients sound unreal and lose their the problems of the phonograph in an characteristic crispness if there is a cut- entirely new way and that they have much achieved improvements off below 15,000 cycles. With its so outstanding 5,000 -cycle cut-off the radio -phonograph that they may almost be classed as revolutionary. cannot do them justice. And matters The main defects of the phonograph are often made far worse by the listen- as we now know it may be summarized er's use of the tone control. In self- as follows: defence against the hiss which he dis- 1. Surface noise, or needle scratch Fig 2- Pickup exploded. A -feeds from coil; likes the listener often turns the knob B -hinge pin; C- rubber mount for armature; as far as it will go, producing in some spoils the .beauty of music by its 0-the armature; E- magnet; G -cover plate. annoying background. cases a cut -off as low as 3,500 cycles. 2. Even the best of ordinary records The response curves of most pickups You will see now how strongly surface deal very poorly with the upper show marked resonance peaks well noise militates against good reproduc- audio frequencies. within the audio frequency range and (Continued on page 66)

RADIO -CRAFT for JUNE. 1947 33 INTERMITTENI' ALARM

Now you can play your intermittent radios silently. The amine the set while it is in its fading condition. "Signalometer" will tell you when they fade or cut out. The Signalometer is a simple instrument. A modulated signal from any signal generator is fed into the input of By J. JACOBSON the radio. in question. The frequency setting of the signal generator is un- important unless you have reason to IF all the time that radio servicemen avail. The only way the set can be made believe that fading is due to oscillator have wasted waiting for radio sets to quit is to throw the switch. instability at some particular frequen- to fade were converted into cash You know that eventually the radio cy. To put the Signalometer into the and added up, it would go a long will fade or stop playing, because no picture, simply connect its two test way toward paying the national debt. customer will spend money just to clips across the primary of the output Types of fading are as various as make a false claim. So you let it transformer. they are annoying. The customer com- play, meanwhile attending to another Examination of the circuit (Figure plains, "I was listening to a quiz pro- repair, and keeping one ear on each 1) shows the output transformer of gram, but the set kept fading on all the set. This can be very annoying, as con - the set under test then will be very answers." An uneducated radio, no centration is required in many repair heavily loaded. This is to reduce the doubt, but typical of the complaints the jobs, for instance those in which you audio signal across the voice coil to be- average radio shop gets day after day. juave to contend with hum or other low- low the point of audibility. A small re- Or perhaps the radio just quit cold after level complaints, which outside noise sidual voltage is amplified in the 6J5 being on an hour. In any event, the can mask out easily. circuit. The output of the 6J5 is fed into half a 6SL7 which operates as a 6:J5 6SL7. 32L7 diode rectifier. A varying positive .ea voltage from the diode rectifier output 1 BUTTON MIIO: is fed into the negatively biased grid TRANS. circuit of the other half of the 6SL7. The plate load of this half is a 250,000 - ohm potentiometer, the movable arm of which goes to a 1/25 -watt neon bulb. The neon tube, which works as a relaxation oscillator, feeds into the grid circuit of the 32L7, which is a combined SW. II1 .AC amplifier and rectifier power supply tube. 40 The frequency of the warning tone de-

Fig. I -The tignalometer permits silent bench testing of the troublesome intermittent radio. pends mainly upon the capacity of the 321.7 grid -coupling condenser, the grid true intermittent radio has to be work- A".arm for intermittents resistor, and the neon voltage. ing for a certain length of time before Here is a device that is both a time it fades or quits altogether. saver and nerve soother. Just connect Operating instructions Examined on the repair bench, all a radio to it and the radio will play at To operate the Signalometer, follow indications are normal. You look at the either low or top volume silently. No this step -by -step procedure: resistors and they look back at you interfering with you or the technician with an innocent as if to working the next bench. The radio 1. Turn radio dial to a frequency expression, on where say: "Sure, one of us is bad, but you'll will continue to play silently until it no broadcasting station can be have to wait till it gets good and ready fades, then it will let you know. It will heard. to quit." You test and tap tubes, check inform you with a warning tone signal 2. Connect modulated rß. signal gen- voltages and condensers, bounce the from the Signalometer. You can then erator to radio input. set up and down on the bench, to no switch off the warning tone and ex- (Continued on page 73)

Front and bottom views. Neon tube is seen in under -chassis photo

34 RAD IO -CRAFT for JUNE, _1947 PuDi-

Top and bottom views of frequency -modulated transmitter. Coils are efficiently placed to keep oscillator and multiplier leads short. Demoøt4tío« 7emtteix

HAT is FM? This is the ques- By HAROLD McDUFF and GEORGE PYLE* tion most frequently asked by the general public whenever a reactance modulator working with a uses 4 turns, of No. 20 d.c.c. spaced to the subject of broadcasting is 6C5 oscillator on 6 me which is tripled % inch. A 1 -turn coil couples this to discussed. To answer this question the twice to 46 mc, the output frequency the antenna. The oscillator coil is tapped FM demonstration unit shown in Fig. 1 employed. The old -band FM receivers at 9 turns from the grid end. was constructed. Although there are a can pick up the fundamental output For reception, one of the automatic number of FM applicants in the Peoria frequency, and a harmonic of this is tuning buttons of the demonstration re- area, there was no immediate prospect of any FM signals for receiver demon- 6C5 6AC7 " 6AC7 stration. OSC. IOPial TRIP IDyuf TRIP If- Two miniature units, one the FM and s iElz's the other the AM, were designed and constructed, using the same tube complement so far as possible on identical chassis 17 x 4 x 3 inches, using similar short whip antennas, and powered by a common power supply to present practically an identical "appearance. The power output of the two transmitters was adjustable so that equivalent signals at the receiver terminals could be obtained. Program material consisting of wide -range electrical transcriptions originating in one of the radio station's B30DV. control rooms was transmitted continu- Fig. Î1ñe FM transmitter. This 4 -tube job might serve as a model for amateur exciters. ously over an equalized telephone line to the demonstration point and fed 6J5 6J5 6C5 6SJ7 simultaneously to each transmitter. Al- MOD. MOD. I_ 4 OSC. ?ouuf though these units were built as simply r 1 as possible, using standard parts, cer- IDx tain problems had to be solved. The schematic diagram of the AM IN 5004. unit is shown in Fig. 2. It consists of a II tunable oscillator coupled to an amplifier stage and modulated by a pair of 6J5 tubes in parallel. Since there are no modulation transformers available for this tube complement, modified Heis- ing modulation was employed. The coils were made from Barker - 300 V. Williamson Miniductors Type 316. The Fig. 2-Schematic of the AM unit, used to supply a signal to a receiver a few feet away. oscillator had 55 turns, tapped 20 turns from the grid end. The tank coil con - used if the receiver has only the new ceiver was adjusted to the frequency of silted of 70 turns, on which the antenna 100 -mc band. the AM unit, while the manual tuning was tapped by experiment. Fixed mica The FM unit coils were all wound control was tuned to the FM signal. condensers resonated the coils at a clear on 1 -inch diameter tubing. The oscilla- Thus changing the FM -AM selector spot in the broadcast band. tor coil was close -wound with 27 turns switch on the receiver picked up which- The FM unit shown in Fig. 1 employs of No. 28 enamelled wire, the first ever transmitter was desired, leaving tripler with 9 turns of No. 22 d.c.c. no other adjustments to be made, at *Peoria Broadcasting Co. (WMBD) spaced to s inch and the second tripler (Continued on page 53)

The AM unit resembles its FM opposite number closely, excepting for component sixes. The output is ample for short -range demonstrations.

RADIO -CRAFT for JUNE, 1947 IS TELEVISION FOR TODAY PART XIII- Problems of the cathode-ray tube

By MILTON S. KIVER

THE cathode -ray tube in the television receivers, and radar equipment point. Some of these sources of inter- vision receiver is comparable to is shown in Table 1. For television, a ference, listed in order pf importance, the loudspeaker in the sound re- combination of zinc sulphide and zinc are: ceiver. It is much more intricately beryllium silicate is used, this combina- 1. Halation tied in with the operation of the tele- tion giving higher conversion efficiency 2. Reflections due to screen curvature. vision set than the loudspeaker is with than most other known compounds. It is 3. Reflections at the surface of the its receiver. Such factors as operating interesting to note that the electron screen face. controls, sources of high voltage, and beam remains at any one point for only 4. Reflections from inside the tube. methods of focusing and deflection re- approximately 0.1 microsecond, yet the quire careful adjustment if a good light emission continues for two to three Effects of halation image is desired. hundredths of a second, indicating that If we examine minutely the light pat- The basic operation of the cathode - the zinc sulphide and zinc beryllium sili- tern produced by a stationary electron ray tube has been described many times cate are responsible through their phos- beam in a cathode -ray tube, we find that in literature. To repeat a principle brief- phorescence for essentially all of the the visible spot is surrounded by rings ly, the electrons emitted by the cathode emitted light seen by the observer. Fig. of light. These rings of light are due are formed into a high -velocity beam 2 is a zinc sulphide persistence curve. to halation. See Fig. 3. The light rays by electrostatic or electromagnetic The principal object in designing a which leave the fluorescent crystals at means, or both, and then projected at cathode -ray tube is to produce an image the inner surface of the tube face travel the fluorescent screen. The beam is de- having good brightness and high con - into the glass and are refracted. Those flected electrostatically with deflection 10 SCREEN -s trast. When the rays which make an angle greater than plates or electromagnetically with de- electron beam . do not leave the glass when they FIRST DEFLECTION DEFLECTION strikes the back of reach the outer surface, but instead are ELECTRON LENS PLATEP E I ELECTRON LENS the fluorescent totally reflected back into it. At each or ED DE screen, the light point where these reflected rays strike which is emitted the fluorescent crystals, they scatter. \ ELEÇTFION PA?H1 ./ distributes itself in It is this scattering of the rays that j Gle.smsrso4"'" the following ap- produces visible rings on the screen. CATHODE proximate manner: These rings cause a hazy glow in the CAD 1. 50 percent of region surrounding the beam spot and reduce the maximum possible detail con- GRID IST 2ND DEFLECTION DEFLECTION the light travels VOLTAGE ANODE PLATE PLATE +/IDEO+ back into the tube. +D -C BIAS 2. 20 percent of the light is lost in Fig. 2-A persistence curve for zinc sulph- -- I5T ANODE VOLTAGE the glass of the ide. commonly used in SCANNING tube by internal re- P4 television screens. 2 ND ANODE VOLTAGE + VOLTAGE + flection. SCMaa1r V0.TACE -HEATER 3. Thirty percent reaches the observ- Fig. I -Se m i- perspective view of components of e cathode -ray tube. er. flection coils. Fig. 1 shows the inside Thus, of all the light that is produced structure of a typical electrostatic de- by the electron beam (and this itself is flection tube. For electromagnetic de- a highly inefficient process), only 30 flection, the plates are omitted. percent reaches the observer. 03 QS sac TINE The most acceptable screen for tele- Image contrast also is impaired be- vision is one which emits white light cause of interference caused by light trast. Contrast, it will be remembered, when excited by an electron beam. This which is returned to the screen after it is the ratio of the brightness of two does not exclude screens emitting light has been reflected from some other areas, one of which is being bombarded of other colors, for some of these have by the electron been and Are being used. However, TABLE I beam, the other black- and -white images are considered RMA Designa- Activator Fluorescent Phosphorescence not. This r a ti o less fatiguing for the eyes, especially for +ion -Substance Color (seconds) should be as high long-sustained viewing periods. The alas possible to have PI -Zinc silicate Manganese Green Med. 4.03 -0.05 ready familiar- motion picture also "rich - looking" or played in an important part the choice P2 -Zinc sulphide Copper Blue -green Long - of this set of color values. high quality P3 -Zinc beryllium silicate Manganese Yellow -Gr. Mad. -0.OS' images. Due to the An electron gun, once constructed, can Silver White Short 0.005 scattering of the be subjected to considerable misuse with- P4-P3 and zinc sulphide light, however, out being permanently affected. On the PS- Calcium Tungstate Blue Very short 5µsec. med. areas which should other hand, failure to grasp the signifi- 0.005 cance of certain precautions required be in total dark- PbZilphide nc Silver White ness receive some to protect the fluorescent screen can cadmium Silver readily result in a shortened period of Zinc sulphide light. The result is P7 -Zinc sulphide Silver Blue Med. =0.006 a reduction in the usefulness as well as unsatisfactory op- Copper Yellow Long eration throughout the life of the tube. Zinc cadmium sulphide contrast ratio. A Very PI I -Zinc sulphide Silver with a Blue short distinction is usual- A tabulation of the most common nickel quencher IOu sec. phosphors in use in oscilloscopes, tele ly made between

36 RADIO -CRAFT for JUNE, 1947 the detail contrast ratio, which is de- fined on opposite page, and the over -all field contrast, which compares two sections of the screen which are widely removed from each other. Halation affects only detail contrast. AIR Screen curvature reflections SIDE Loss in contrast due to reflections arising from the curvature of the GLASS screen is shown in Fig. 4. The rem- FACE- edy for this is to use a flat screen. Many adaptations, in this direction have been 'made, since the screen curvature greatly VACUUM SIDE FLUORESCENT SCREEN restricts the useful image area. One ex- Fig. 3- Illustrating how reflections between the two sides of the glass can cause halation. ample is the large 20 -inch tube television sets currently being offered to the generated by the screen crystals from To the observer this appears as a dark public by one prominent manufacturer. traveling back to the tube. This is shown patch. A good portion of the image is, in this in Fig. '6. The light which previously Several methods for preventing the writer's opinion, useless because of the went back into the tube is now reflected ions from reaching the screen are in optical distortion introduced by the toward the observer. current use. First there is the bent elec. screen flat 10 curvature. A -face -inch The metal film is extremely thin, in tron gun, as shown in Fig. 8. Ions and seems 20 -inch tube preferable to the the order of 3,500 x 10.8 centimeters electrons emitted by the cathode are ac- curved screen. thick. Since even a layer this thin does celerated to the first and second anodes. Reflections from screen surfaces interpose a barrier in the path of the However, the cathode is inclined at an electron, high accelerating voltages angle to the rest of the gun structure, Light rays, when they travel from must be used. In one medium to lose a another, certain Fig. 7, the efficien- amount of energy at the intersection of cy curves of the two media. At the cathode -ray tube screens having the screen, soma light is reflected when it metallic layer and* reaches the dividing surface between those which do not the air and the glass of the tube. The re- are compared. At flected light travels back to the inner low accelerating surface and then back to the outer sur- voltages, the ener- face and then back to the inner surface gy lost by the elec- again. At each dividing surface, some trons in penetrat- of the light continues onward and some ing the layer de- is reflected back into the glass. Absorp- creases their effi- tion and dispersion quickly reduce the ciency below that strength of these rebounding rays. of similar electrons In Fig 5 -a we see how reflections in tubes without from the insidé surfaces of the tube can The act decrease field contrast of the this layer. Fig. 6-Aluminizing the screen concentràtes all the light forward. to the poorer efficiency image. The loss in contrast from this continues until we reach the point and both particles, if permitted to travel source of interference can be made low where the curves intersect. in a straight line, would impinge on the never usvvL DIAMETER Beyond this region, the screen with side of the electron gun and reach the metallic layer is much superior to the screen. If a strong magnetic field is in placed in the path of the particles, it is EsennG AREA the ordinary tube. The rapid rise efficiency is due to a decrease in energy possible to alter the paths of the elec- Fig. 4- Diffusion effects in non -flat screen. lost at the metallic barrier plus an in- trons sufficiently to have them to travel crease in the over -all brightness due to toward the screen. The heavier ions, by special shaping of the bulb walls, as the light -resisting characteristics of the however, are not sufficiently deflected. shown in Fig. 6 -b, and by the use of layer itself. As a result, they hit the side of the black aquading coating. The latter coat- electron gun. The magnetic `field which ing is also useful purposes, A matter of considerable importance for electrical ion in (Continued on page 57). acting as a shield and a path for the re- is the elimination of the spot turn of the secondary electrons emitted tubes using electromagnetic deflection. f:: from the fluorescent screen. No matter how carefully a tube is de- gassed or how well the cathode coating is applied, ions will be present in the SPOT electron beam. These ions are either gas as elec- molecules which have acquired an ao tron, or, else molecules of the outside coating material of the cathode. The ions have the same charge as the electrons and are sensitive to the same accelerating voltages. In tubes employing electrostatic deflection, the ions and the electrons are similarly deflected and for Fig. 5-How internal reflections are reduced. all practical purposes may be considered as one. However, when electromagnetic A recent step toward improving deflection is employed, it will be found Is- screen.brig{Ttness and contrast has been that these heavier ions are barely de- the addition of an extremely thin film flected. Consequently, they tend to strike of aluminum on the back of the fluores- the center of the screen in a steady OS. cent screen. The film is sufficiently thin stream and produce a thin film of de- to permit the electrons in the scanning activated material on the area exposed. (We I 2 3+ s 6 r é 0 n u a o w o e ñ beam to reach the fluorescent crystals. When the electrons in the scanning beam AP0.ED VOLTAGE -N RAW! It will, however, prevent any of the light pass over this area no light is produced. Fig 7- Effect of aluminizing on efficiency

.RADIO-CRAFT for JUNE. I 9 4 7 37 RAI)IO DATA ShEEn 347 MOTOROLA AUTO RADIO 1946 MODEL CR6 TUNING RANGE OVERALL SENSITIVITY 535 to 1600 Kc. Frequency 1400 Kc., 1000 Kc., 600 Kc. Sensitivity 1.5 lux 1.5 ).sv. 1.0 µv. Standard output is to be I watt and is measured the 3 resistive ELECTRICAL CHARACTERISTICS across -ohm load. (1 watt - 1.74 volts). Test is Power input: 10 amperes at 6.3 volts made with 30 percent 400 -cycle mod- (including speaker field) ulation. Tone control is set to VOICE position and volume control at maxi- Power output: 9 watts TUBE COMPLEMENT mum.

I 6SK7 -GT R.f. amplifier I 6SA7-GT Oscillator -Modulator ALIGNMENT TABLE I 6SK7 -GT I.f. amplifier TUNER POSITION SIGNAL GENERA - STEP DUMMY TOR LEAD 1 6SQ7 -GT a.v.c. SET TO ANTENNA Detector- -a.f. CONNECTED TO SSETGAT ON3 OUTPUT METER amplifier H i g h frequency 0.1 .f I 6SQ7 -GT Audio inverter I at Oscillator -Modula- 455 kc Primary and secondary end (cores out) Sig. Gen. for grid of T -I 2 6V6 -GT Push -pull power amplifier (#5 pin) Primary and secondary I OZ4 or Rectifier of T -2 6X5 -GT 2. H i g h frequency 60 µssf at Antenna 1600 kc Oscillator trimmer kí06,..), re Kies end, tuning shaft Sig. Gen. receptacle against stop. Cores (across er ..¿vou+ in series in R.I. trimmer should be set fo 21 -inch co- r (across L -2) we. project 111/4 s inch axial lead. Antenna trimmer from cans. :;'rev (across L -1) 3. EXACTLY one full 1425 kc Oscillator core of L -3 turn in from high R.f. core of L -2 ." µ °« á..rit frequency end. Use Antenna core of L -I knob set screw as :'F` an indicator. Start measuring turn the moment tuner carriage starts moving inward.

4. EXACTLY four more e Power Oscillator pad core of full turns in (as turned L-4 for maximum noise. indicated by knob OFF 7 setscrew)

,. i'S:,^,.R.`d. 5. Assemble and install receiver in car and connect car antenna. Turn the dial to approximately 1400 kc (not to a local station) and adjust antenna trimmer for maximum noise. This adjust- r ment is referred to as Antenna Padder in receiver installation de ail figure. NOTE:If oscillator padder core adjustment is too far off, repeat alignment procedure, Installation diagram. A- speaker field, yellow; steps 2. 3, and 4. It may be necesssary to repeat alignment more than once if padder ad- B -voice coil, white; C- ground, black; D- justment has been Indiscriminately tampered with. battery. 6SK7 -GT 6SA7 -GT 6SK7 -GT 6SQ7-GT (2) 6V6 -GT C2) R.F. AMP. Smut OSC. MOD. 1.L IST IS. T2 POWER AMP.(TWO) .0001? .0111 .0001 A001 - 11--- - d T3 y1á .li. I 47K 1B0uuf

IOOK BOuld LI 4TK o L2.0 I

006 I II1

I .00a`2 `--is- E. T.-1.- -00012 I tel L3i1 T11 y.00009 - OSC PAD AUDIO U.L INVERT. 1-- 40uuf _ 'SEE T47OK; NOTE T .1 B T.os 10K Ì AS S 330 .5 .=.'SE1 NOTES

RED-BW Ol

TONE s-a P. I.F.455 KC

IK .1°, RED FILSL5 1 IMEG 150 "" .. of 66 .05 Si 2 *-10 TT `, 1 1T Z i VIBRATOR 62 gRN SP.I G-I T4 OZ4/6X5-GT 0 l J 4 4ic.GRN l 6 0 BAT. ONO V.C. S. FIELD S`''w0o R S2 6-¡o BLU TO BAT.RECEPTOR +--- o o TO AMMETER ó I -a NOTE e: RETURN SPNING AND CARRIAGE PLATE MUTE SW TCI, ACTUATED BY CARRIAGE "A-LEAD ASSEMBLY

38 RADIO -CRAFT for JUNE. 1947 SENSIITIO u LUE THE KIT COMES COMPLETE- LY ASSEMBLED. Can be wired in 15 minutes. ponents and circuit guaranteed to meet the following BUILD YOUR OWN specifications: 4 A.C. VOLTAGE RANGES: 0- 15/75/300/1500 volts. 4 D.C. VOLTAGE RANGES: VOLT -OHM- MILLIAMMETER 0- 15/75/300/1 500 volts. 2 D.C. CURRENT RANGES: 0 -15 /150 MA. 2 RESISTANCE RANGES: axce 'owe 0- 10,000 ohms; 0 -1 Meg.

The Model -KT 20 kit provides ALL components, including meter, panel, cabinet, resistors, condensers, tip jacks, control, selector switch, copper.oxide rectifier, pre -cut wires -in fact every component and part needed to complete the unit.

Complete kit including ALL PARTS assembled and ready for wir ing, circuit diagram, easy -to- follow instructions and detailed operating data for the completed instrument.

THE NEW MODEL B -45 THE NEW MODEL 670 SIGNAL GENERATOR SUPER METER $2840 A Combination VOLT -OHM -MILLTAMMETER e, Complete, ready to operate '2775 plus CAPACITY REACTANCE, INDUCTANCE and DECIBEL MEASUREMENTS Self -modulated - provides a highly stable signal. =° i t " CC' D.C. VOLTS: 0 to 7.5/15/75/150/750/1500/7500. RF frequencies from 150 Kc. to 12.5 Mc. on Funda- Ceti A.C. VOLTS:O to 15/30 /150 /300 /1500 /3000 Volts. mentals and horn 11 Mc. to 50 Mc. on Harmonics. OUTPUT VOLTS: O to 15/30/150/300 /1500/3000. Modulation is accomplished by grid -blocking action equally effective for D.C. CURRENT: 0 to 1.5/15/150 Ma.; 0 to 1.5 Amps. - RESISTANCE: alignment of amplitude and frequency modulation as well as for television E 0 to 500 /100,000 ohms 0 to 10 Megohms. receivers. Self -contained batteries. All calibrations are etched on the front CAPACITY: .001 to .2 Mfd., .1 to 4 Mfd. (Quality test for ciccsrolytics). REACTANCE: panel, permitting DIRECT READING. 700 to 27,000 Ohms; 13.000 Ohms to 3 Mcgohms. INDUCTANCE: 1.75 to 70 Henries; 35 to 8,000 Henries. Model B -45 uses a beautifully processed dualtone front panel. Comes housed E DECIBELS: -10 to +18, +10 to + 38. +30 to +58. in a heavy -gauge crystalline steel cabinet complete with shielded test lead, E The Model 670 comes housed in a rugged. crackle- finished steel cabinet com- self- contained batteries and instructions. plete with test leads and operating instructions. Size 51/2" x 71/2" x 3 ".

IIIIIIBIII11111111111111111IIIIIIIIIIIIIIIIIIIIf IIIIIIII IIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIII11; 111IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIWIIIIII1114 IIIIIHIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIHIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIII11111 I

THE NEW MODEL CA -11 = THE NEW MODEL 450 SIGNALTRACER$1875. i TUBE TESTER $3950 \ Simple to operate because signal intensity ß o Speedy operation - assured by newly designed readings are indicated directly on the meter! rotary selector _ a switch which replaces the usual ead soap, toggle. or lever action swttcbes. \ : * SIMPLE TO OPERATE - only 1 connecting () t cable - NO TUNING CONTROLS. o * HIGHLY SENSITIVE uses an improved E )" SPECIFICATIONS 1 VacvuRt Tube Voltmeter circuit. f Tests all tubes 117 up to volts. Tests shorts Tube and resistor -capacity network are built * into = and leakages up to 3 Mcgohms in all tubes. Tests the Detector Probe. E both plates in rectifiers. New type line voltage adjuster. Tests individual E sections such as diodes, triodes, pentodes, etc., in multi -purpose tubes. COMPLETELY PORTABLE- weighs 5 lbs. and measures S" x 6t' x 7 ". * _ Noise Test -detects microphonic tubes or noise due to faulty elements and loose *Comparative Signal Intensity readings are indicated directly on the meter as = internal connections. Uses a 41/2" square rugged meter. Works on 90 to the Detector Probe is moved to follow the Signal from Antenna to Speaker. - 125 volts 60 cycles A.C. - * Provision is made for insertion of phones. E EXTRA SERVICE -May be used as an extremely sensitive condenser Leakage The Model CA -11 comes housed in a beautiful hand -rubbed wooden cabinet. E Checker. A relaxation type oscillator incorporated in this model will detect Complete with Probe, test leads and instructions. - leakages even when the frequency is one per minute.

OUR POLICY We do not advertise any unit which is not available for immediate not solicit orders for any unit that does not meet our requirements shipment from stock. Less flowery adjectives, more detailed for accuracy and honest value. Any item purchased from us is sold specifications. All units are sold subject to one year guarantee with the understanding that it may be returned for full refund except when components are damaged through misuse. Ire do after a 10 day trial. 20% DEPOSIT REQUIRED ON ALL C.O.D. ORDERS

GENERAL ELECTRONIC DISTRIBUTING CO. DEPT. RC -6, 98 PARK PLACE, NEW YORK 7, N. Y. RADIO -CRAFT for JUNE, 1947 39 (Present -day B & W receivers of the fiers. One tuning control may be used direct -viewing type and using a 10- COLOR TELEVISION to tune in the video signals. The 3 -color inch cathode -ray tube employ 30 tubes, (Continued from page 21) signals are next fed into their respec- thus the sequential color receiver com- tive cathode -ray tubes (each about 3 pares favorably in the number of tubes. inches in diameter) on the ends of which A disadvantage of the sequential re- reduced to 12.5 mc.) Sound is trans- appear the 3 images: one in red, one in ceiver is that it is not possible to pick mitted on a relatively narrow band (a blue, and the third in green. Each tube up color images broadcast by the simul- subcarrier of 524.1 me), along with is made with a different phosphor on taneous system (without special design the video signals, as the figure makes the screen which will respond to one of the receiver). clear. color, one tube for the red, one for the The receiving aerials used to pick up At the transmitter, the film (or live blues etc. the sequential color images were of subject) is scanned by a beam from a Magnifying lenses are placed in front - pic- simple design; in many tests a double kinescope tube. After scanning the (Continued on page 56) horn type proved . efficient, dipole an- ture or subject, the beam is focused placed at the foci's of the a lens onto a system of semi- tennas being through PHOTO -TUBE LIGHT FROM parabolic horns. The horns were. made transparent mirrors and 3 photocells LENS GREEN IMAGE of latticed wire in some instances. (Photo D). Each photocell picks up its respective color component and modu- RCA simultaneous color system lates the corresponding carrier. LENS In the simultaneous electronic system For picking up live subjects a flying PHOTO - demonstrated by RCA the three basic spot from a kinescope tube scans the MIR TUBE REFLECTS are trans- scene, the reflected beam falls on a sys- LIGHT colors (red, blue, and green) REDI mitted all at the same time and con- tem of dichroic (color -selective) mir- FROM tinuously. No moving parts such as rors, which reflect the respective color PHOTO'' BLUE revolving color filters are used, the components .onto 3 photocells. These IMAGE operation being fully electronic. Fig. cells in turn modulate the 3 carriers LENS:; MIRROR 1 -b and Fig. 2 -b show how 3 separate used to -transmit the signals. See dia- 76-61.1/E carriers carry the three colors. The gram Fig. 1 -b. total band width of the 3 carriers is Each of the transmitted red, blue, only 14.5 mc. (In a special test this was and green images has the same number (525) of scanning lines and also the same horizontal scanning rate and picture repetition frequency of 30 per second, as in present B & W broadcasting. At the receiver each carrier, modulated respe ctively by the red, blue, and green signals, is tuned in through separate band -pass Fig. 4-A block diagram of the CBS color television receiver. circuits and ampli- Photo D- Simultaneous system color analyzer.

receiver. Photo B-CBS television receiver, rear view. Photo C-The CBS projection color, JUNE, I 9 4 7 40 RADIO -CRAFT for Nccdcti 1947 RADIO DIAGhAMS and S,..rri:ing Infnnrrolion

GET ALL 7 VOLUMES NOW i?ma31n9 ilatfa n O'ááet ¿n P ayram itanuah ALL NEW 1947 CIRCUITS SERVICE DATA YOU NEED TO GET AHEAD Be prepared to repair quickly all new 1947 Speed up and simplify all radio repairs with the inexpensive sets. In this big single volume you have clearly SUPREME Manuals. Service radios faster, better, easier, save printed, large schematics, needed alignment data, replacement parts lists, voltage values, money and time, use these most- often- and information on stage gain, location of Most Popular needed diagram manuals to get ahead and trimmers, and dial stringing, for almost all Models Made by: earn more per hour. At unbelievable low sets released between June 1, 1946, and March R.C.A., Zenith, cost (only $2 for most volumes) you are 1947. A worthy Philco, Sears, Fada, companion to the six previous assured of having in your shop and on the volumes used by over 100,000 shrewd radio Emerson, Belmont, Detrola Radio, job, needed diagrams and other essential servicemen. There is no need to spend large United Motors, repair data on 4 of 5 sums for bulky, space -wasting manuals or to GE., Westinghouse, out sets you will ever buy additional drawings every few weeks - Arvin, Majestic, service. Every popular radio of every make, get this low- priced new SUPREME PUBLI- Stewart -Warner, from old- timers to new 1947 sets, is in- CATIONS Admiral, Delco, manual and you have all service cluded. Clearly printed circuits, parts information on popular Stromberg- Carlson, lists, 1947 sets. Covers 327 Western models of 52 Auto, alignment data, and helpful service hints different manufacturers. Sparton, Motorola, Large size: 81/2 x 11 in., 192 pages $200 Wards, Gamble, are the facts you need to improve your + index. Manual style binding and many others. servicing ability. Save hours each day, e every day, let these seven volumes furnish Post-War Automatic Pre -War Record Players, diagrams for 80% of all sets. See pictures 1945 -1947 Record Changers Changers, & Recorders of these attractive manuals above. Each vol- Service expertly all n e w Just what you need to repair (1945 -1947) record changers. quickly thousands of pre -war ume has between 192 and 240 pages, large Follow simplified factory in- automatic record changers, size 81/2 x 11 inches. Manual style binding. structions to make needed ad- manual units, pick -ups, wire- T.. r: justments and repairs. Hun- less oscillators, recorders, and Compiled by Send coupon today. Complete satisfaction dreds of photographs and combinations. Hundreds of M. N. neltman, epáiieeerihá; guaranteed. exploded views; thousands of mechanical and electrical dia- & serviceman. test hints; service instruc- grams. Instructions for ad- tions for all popular makes. justments and repairs. Most Large size: 81 x 11 ", 144 popular units of all makes. NO RISK TRIAL ORDER COUPON fact -filled pages. At 128 large pages. SUPREME PUBLICATIONS, 9 S. Kedzie Ave., Chicago 12, ILL. your jobber 8512 or post- $150 x 11 inches. $ Ship the following paid, only Price, only 150 manuals: (Money back guaranteed) J 1947 1946 1942 1941 1940 19391 r 1926 -1938 See Your L Price each volume only $2.00, postpaid ` $2.50 J Radio Jobber or Send D Post -War Automatic Record Changers, $1.50. Pre -War Record Players, Changers, & Recorders, $1.50. I am enclosing $ send postpaid. Supreme Send C.O.D. I Publications am enclosing 8 ... deposit. PUBLISHERS OF RADIO BOOKS, MANUALS, AND DIAGRAMS Name:

9 B. KEDZIE AVE. CHICAGO 12, ILL. - Addreu: RADIO -CRAFT For JUNE, 1947 4, r/ff¢tzopolitan RADIOEL[(TRDDI( CIRCUITS OFFERS 4 TWO -TUBE PORTABLE IA7 -GT with the detector coils connect- This regenerative receiver covers the ed between the No. 1 and No. 2 grids. broadcast band, without an external an- This permits the plate to operate at full GREAT VALUES tenna and with enough power to drive a voltage without the coupling resistor small speaker on strong locals. A stan- normally used for interstage coupling The Model 689 -IF dard broadcast loop antenna, mounted to an a.f. amplifier. The plate is coupled WESTON OHMMETER on the case with wooden supports, pro- to the detector by the electron stream. vides enough pickup for most purposes. Regeneration is controlled with a 0.02 -pf A convenient, pocket aim -ohm potentiom- ohmmeter for checking dr- The entire set, including batteries, is condenser and 500,000 culte by the resistance and eter in series between the No. 2 grid continuity method. The ener- built in a box 3 by 4 by 5 inches. gy for the resistance read- It uses a 1S5 detector with a 1S4 a.f. and ground. ings in supplied by a self - it be contained 1.5 volt No. 2 amplifier. Regeneration is provided by If a long antenna is used, should standard large flashlight connected to the control grid, No. 4, cell. Built to meet U.B. winding a 10- to 15 -turn loop, using Army Requirements for Ac- which is returned to ground through a curacy and Durability! 2.5- millihenry r.f. choke. A short an- This Ohmmeter also has a double range D -10 and 01000 tenna works best when connected directly to the oscillator grid. Coils are wound as follows ohms for the accurate measurement of low resistance values. Wavelength Turns Model 689 -16. comen complete with operating Instruction. test (Meters) Ll L2 leads and LEATHER CARRY- ING CARE. a 14- 25 4 6 Lint price $25.50 $14.85 Our Price 23- 41 7 9 40- 85 14 12 The New Model 111 83-125 23 23 AC -DC QUALITY 120 -200 36 36 MULTITESsTER No. 36 d.c.c. or enamel wire is used A new pocket -size volt -ohm- m ilia am meter w th features on 11/4 -inch forms. The windings are never before available in an instrument of this size and spaced 3é inch apart. price. D.C. Voltmeter: 0- 5.50 -250- HAROLD R. NEWELL, 500.2500 volts. A.C. Volt- meter: 0.10. 100- 500.1000 Bradford, N. H. volts. Output Voltmeter: 0.10. 100 -500.1000 volts. The 2 regenerator. Antenna it supported 1DÓ0 millia nperesr' D C. 1 Am- -tube PHONO OSCILLATOR 0.1 -10 amperes. peres:Ohmmeter: 0. 500.100.000 in slots in the two plugs on top of cabinet. ohms: 0.1 megohm. Decibel This phono oscillator described re- Meter: -8 to .55 db. The scale is eaiibrated for line produces the bass notes without notice- of 500 ohms impedance. For other impedances correc- No. 28 wire over the grid winding. tion charts are supplied. able hum modulation. A standard an- Model Il1P, mot Illustrated) Volume and regeneration are controlled leads and romol

42 RAD10 -CRAFT for JUNE 1947 Never so much radio $095 Including Tubes for so little money Postpaid in U. S. A.

SUPER -HETERODYNE FOUR TUBES and SELENIUM RECTIFIER 110 Volt AC -DC KITS direct from factory to you-

Never before has BELLTONE packed so much qualify and value in a $10.95 complete package. This four tube and selenium rectifier super -het kit of parts (chassis 101/2 "x51/2"s7 ") has proven its selectivity, sensitivity and high quality radio reproduction in tens and tens of thousands of receivers sold during the past months. Today you can have this same chassis with all post -war improvements at virtually cost of component parts, drawings, instructións, packing and mailing costs -complete except for cabinet, wire and solder. three big assembly and hook -up prints and ill circuit improvements and parts include - ABC detailed instructions SELENIUM RECTIFIER - eliminates troublesome supplied rectifier tube-it's unbreakable- -lasts the lifetime of your set- starts instantly -- increases sensitivity. including schematic circuit, picture wiring 2. PROTECTIVE FILAMENT RESISTOR- prevents cur- diagram, top chassis layout, dial cord in- rent surge through filaments- eliminates tube burn- structions and cabinet layout suggestion - makes assembly, wiring and final adjust- outs and increases tube life. merits easy, instructive and foolproof. 3. ALNICO PM SPEAKER -1.47 ounce S inch speaker for high quality voice and music reception. direct from factory to you 4. GRIP- STRAIN RELIEF -securely anchors power line cord to chassis-preventing short circuits. only no sales to jobbers, - 125A7 - 12SK7 - 12S97 S. TUBES SUPPLIED-one each dealers or surplus outlets and 50L6 or 14A7 - 14Q7 - 1466 and 50A5.

BELLTONE RADIO and TELEVISION CORP. ORDER YOUR BELLTONE 583 Ave. of the Americas. New York 11, N. Y.

Yes, I want BELLTONE chassis kits Enclosed find

SUPER -HET CHASSIS KIT--TODAY money order check for S

SHIP TO

SHIPPED BY RETURN MAIL STREET CITY STATE

RADIO -CRAFT for JUNE, 1947 43 used with a 5 -inch speaker, this set gives more than enough volume for the aver- RA DIOMEN Here's the Nota .9vailacia ot age room, as well as good frequency response. When using the tone control Way to Bigger Pay IMMEDIATE DELIVERY 6SQ7 25L6 250Kÿ I,01 A A Complete Practical Set of Complete OnIY for TELEVISION RADIOStudy and la:05 Books SH COIL KIT Refera^ e ICE With these Colis, Construction of Your Television Set is Simplified Yours FREE Instruction Manual for 20 -Tube, 7 -inch To Picture Tube Set, included with each a Try7 Days NOW -a new 1947 set 2 6 251 ¡fB SOT Kit. 117V.AC 250 of practical, down to Designed by Television Engineers these earth" books for the man who wan¡,s to get Coils are able to meet most exacting re- ®SW. ahead 4250V. in RADIO and quirements. This Kit makes it possible realizes he must know in grid circuit of 25L6, the total modern radio and tele- the the NEW vision grid resistance should be to handle a big- FOR THE HOME CONSTRUCTOR not greater 1947 Edition ger job. "Applied Prac- than 250,000 ohms. OFF tical Radio" gives the lo build a set of excellent quality able to JUST radio worker the informa- LESTER M. Goon, tion he needs to advance in his six of Television Trans- PRESS receive channels Grove City, Penna. job or radio business. Yet, thiv mission with FM Sound great set is written simple enough (It should be noted that the plate and for the beginner. This is the only set of its kind screen of the 25L6 are operated volt- in America today. AT LOW COST at ages that exceed the maximum ratings APPLIED PRACTICAL RADIO Look at these specified by the manufacturer. Opera- Tells All in 3 Handy Volumes tion in manner may the SPECIFICATIONS this shorten Here is practical. working knowledge of RADIO tube life. Normal operation may be had as it is used TODAY -from by reducing the voltage to 110 basic -princjples to latest IF COILS volts and advances in Television. The Bandwidth of 4.25 MC that can operate changing the cathode resistor to 150 facts are boiled down, in- FREE! ANY site Picture Tube with Mßximum ohms. -Editor) cluding the "know how" to resolution construct, install and serv- 1 year of Con- Permeability Tuned, All Coupling ice all types of Radio and sultation Service all Traps T e l e v is i o n apparatus. Coils and CONVERTER CONTROL Unique picture instruction Mounted & Tech Bulletins Shielded; CAN Here is a simple method of controlling. method takes equipment Adjacent Channel and Sound Traps apart to show what makes included Built -in Coupling and Filter networks the strength of the oscillator voltage it work and how to keep it applied to the grid of the converter of a going. t'RF TUNER ASSEMBLY superhet. It permits the operator to Everything New in Rodio 6 Channels, No. I to No. 6 inclusive maintain a desirable ratio between os- Made Easy Permeability Tuned, All Channels cillator injection voltage and signal The hundreds of interesting up -to -the- minute sub- Maintains Gain and Bandwidth over voltage in the converter tube, and rejects covered include Fre- all Tuning Ranges quency Modulation, Tele- is 10 to 1 GUARANTEE High Sensitivity duces objectionable hiss that common vision, Auto Radio, Public Tuning Coils, Os- at low signal levels. Address Systems. Multi - Set must earn 10 Antenna Coil, RF Band Receivers. High Fre- cillator Tank Coil, all mounted on limes its cost or o00í1 quency and Short Wave - Switch Assembly Plate 6SL7 everything in radio today Coyne sends money MIX.GRID 001 30K from A to Z. Almost 1000 back o its return with 600 Pages Illustra- at end n of I year OUR $2350 OFFER 20K 50K 8+ tions and new diagrams. .00015 50K e02 150.250V, INCLUDES THE FOLLOWING Send No Money -See Books Free I Tank Coil, I Antenna Coil, Oscillator FILTER But don't take our word for what these great books can 6 RF Tuning Coils, all mounted on Switch 20 'O' to for you-see them yourself. dust all in coupon be- Assembly Plate; 5 Video IF Coils, Shield- low and mall it today. Coyne sends you "APPLIED ed, Permeability Tuned; I Shielded Dis- PRAC- TICAL RADIO" to look over Backed criminator Coil; 3 Video Peaking Coils, by 7 day's FREE. If you feel set and Instruction Manual containing Cir- Isn't everything we say AND Coyne School's cuit Diagram for 20 Tube Seven Inch In this circuit, the oscillator of the MORE, just return it at our 20 years Picture Tube Set, together with detailed expense and you owe nothing. of Assembly Instructions, and Parts List. set is replaced by one triode section of a If you keep the set you need Radio shop Pay only Sa after 7 days and The design of these Coils makes it possible to 6SL7, the output of which is resistance - 73 per month (see coupon). You experience obtain satisfactory operation within the ENTIRE capacity- coupled to the remaining sec- can't lose on this offer, se don't range of ANY Television Station. delay -send that coupon NOW. service tion through a variable control. The in- If Our Instructions are Followed jection voltage for the converter is tak- COYNE ELECTRICAL SATISFACTION IS GUARANTEED SCHOOL en from the plate of the amplifier Radio Division, Dept. A7 -Ti, All Special Coils are in this Kit. Remaining parts CHICAGO 12. ILL. are easily obtainable. through a 10 -µµf condenser. TERMS It is imperative that the 50,000 -ohm Shipped Express Prepaid on receipt of check or control be mounted very close to the Money Order. Or Express Collect on receipt of socket of the 6SL7. An extension shaft 25 per cent deposit with order, balance C.O.D. EDUCATIONAL ROOK YELISNINO DIVISION, may be used to a control out to the COYNE ELECTRICAL a RADIO SCHOOL. Dept. A7 -T1 *Patent Applied for. bring 500 5. Pauline St., Chicago 12, III. panel. Keep all other leads as short as Send me Coyne's new 3- Volume Set. "APPLIED PRACTICAL RADIO" for FREE examination. After 7 possible in accordance with standard days rit either return It and owe othing, or pay e3 and e3 month to total 510.75. Or I'll pay practice of oscillator construction. ah price anteervice. Technical Bulletins and 10 to Guar. RAY - LECTRON CO The c.w. operator may use this circuit tee. "Television Kit Headquarters" on his beat -frequency oscillator with NAME AGE 706 Tenth Avenue the same advantages. ADDRESS I TOWN ZONE.... STATE BELMAR, N. J. C. E. HENDERSON, 0 Send C.O.D. VII Balboa Beach, Calif. Lffee. Same money back guarantee e after 7- day C trial. 44 RADIO -CRAFT for JUNE, 1947 WANTED! Chief Engineers, Studio Engineers, Transmitter Engineers for 700 FM Broadcast Stations

the F. C. C. predicts will be in operation by the end of 1947

YES, Plenty of Good -Paying Jobs ... But Only for Those Qualified

FM is actually coming into its own this year . 700 new stations, says the F.C.C. Standard broadcast stations have already passed the 1200 mark. By next year there will be 3 times as many broadcasting stations (AM, FM and TV), as there were before the war. Television receivers are rolling off production lines. If you have had professional or amateur radio experience and Radio is not only expanding in job opportunities but it is also want to make more money, let us prove to you we can give you the growing in technical complexity. Rapid developments in the field of training you need to qualify for a radio job. To help us intelligently radio -electronics are leaving many old -time radiomen far behind the answer your inquiry - PLEASE parade. These are the men who fail to realize that their technical STATE BRIEFLY YOUR BACK- GROUND OF EXPERIENCE, EDU- knowledge must grow with the expansion of radio itself. CATION AND PRESENT POSITION. What does this mean to you? It means you must study not only to hold the job which you now occupy ... but study to qualify for the better job you want. CREI modern technical training can (within a comparatively short time) qualify you for the better jobs and enable you to step ahead of those who have failed to MAIL COUPON TODAY FOR improve their ability through technical training. THIS 24 PAGE FREE BOOKLET! Beginning right now CREI can provide the on -the -job program that equips you with the ability to go after -and GET -these important high salaried jobs. Get all the facts today about the unprecedented CAPITOL RADIO ENGINEERING INSTITUTE opportunities that await you. Learn 16th & Park Rd., N. W., Dept.RC -6, Washington 10, D.C. how CREI spare time technical training can help you as it Gentlemen: Please send me your free booklet, "CREI has helped thousands of other professional radiomen Training for Your Better Job in RADIO -ELECTRONICS", together with full details of your home study training. advance to better jobs during the past twenty years. I am attaching a brief resume of my experience, education and present position. CHECK PRACTICAL RADIO ENGINEERING VETERANS! CREI TRAINING AVAILABLE UNDER THE "G. I. BILL!" COURSE PRACTICAL TELEVISION ENGINEERING NAME STREET CAPITOL RADIO ENGINEERING INSTITUTE An Accredited Technical Institute

CITY ZONE STATE DEPT RC -g, 16TH AND PARK ROAD, N. W. WASHINGTON 10, D. C. I am entitled to training under the G.I. BILI. Branch Otfces: New York (7), 170 Broadway San Francisco (2), 760 Market St.

RADIO -CRAFT for JUNE. 1947 45 \O \ \:\ \ , AAAAAVAAAOAAOAA.. '.

LOOK AT THESE VALUES! £ \ , ALMO VALUE No. 1 COIL WINDING KINK corners of a square about the size of Recently I had my hand drill clamped the popular changer bases. Of course, 5 TUBE SET horizontally in a vise, trying to rewind the lengths of chain are adjusted to a transformer secondary with No. 42 support the changer level at a con- AC -DC, 110 VOLT wire. I tried using the table as a sup- venient height above the workbench. port for my hand while guiding the wire When in use, the hooks are slipped into AVC Built-in s by letting it slide between my thumb the mounting holes of the changer base. tuned Ioop. The may be Vernier tuning _---- nP' 4 and index finger. I found that by plac- chains rolled up or pulled ing the thumb, to one side when not in use. (size 8x5x6). ,,:, holding the wire, on the .. edge of the and ROBERT M. BOSCH, Walnut or table the index finger ; E Y ` Philadelphia, white plastic. ....,,... under the table, I could move very slow- Pa. ly along the table and wind a closely - POWER SUPPLY SAVER Your Cost 15.75 wound coil in very little time. It is best to leave at least four inches between the Whenever I construct a power supply 3 Lot Price $15.45 table edge and the winding. for receiver or amplifier, I insert a No. I used a thin sheet of paper between 47 pilot lamp between the negative side each layer and held it in place with a of each filter condenser and ground. ALMO VALUE No. 2 small piece of Scotch tape. When cold, the resistance of the bulb RAY KIEFER, is negligible. If one of the condensers AUTOMATIC Indianapolis, Ind. shorts, the resistance of the bulb will raise high enough so that the rectifier VOLTAGE INDICATORS tube will not be ruined. The shorted con- RADIO PHONOGRAPH In the radio shack or service shop, it denser can be located merely by locating is often desirable to know the line volt- the condenser connected to the lamp COMBINATION age within limits. For this purpose, I that is lighted. EHRICK H. WRIGHT, use a pair of neon lamps connected as Summit, N. J. Smart modern walnut shown. Quarter-watt neon lamps are design cabinet. Plays available to fit standard pilot light as- SPOTTING MOUNTING HOLES 10-10" or 8 -12" records. Balanced tone semblies and they present a neat ap- It is often difficult to locate accurate- arm. 6 tube superhet- pearance on the panel. ly mounting holes on a chassis radio erodyne with self con- for tained antenna. components, particularly large trans- IIOV -A.C.. D.C. op- formers, variable eration. chokes and condensers. This can be done quickly and simply by Your Cost $50'95 placing chalk dust in the screw holes, or on the mounting lugs, and placing the 3 Lot Price $49.50 component gently in place. A sharp tap on the upper surface will leave clear im- pressions on the chassis and it is then ALMO VALUE No. 3 a simple matter to drill the holes accu- Two 100,000 -ohm wire -wound poten- rately. G. F. STONEMAN, Portable PHONO -RADIO tiometers are connected in parallel Chilliwack, B.C. In Beautiful Leatherette Case across the a.c. line. The lamps are connected between the arm and one end of BUZZERATOR the potentiometer. If it is desirable to Here is the circuit of a little device establish limits between 100 and 120 that I use instead of a signal generator volts (for example), the potentiometer for simple servicing and signal tracing. A is adjusted so that its neon lamp It consists of a small buzzer, 3 -volt bat- starts to glow when 100 volts is applied tery, volume control, and blocking con- across X and Y. Potentiometer B is ad- denser mounted in a coil shield. I find justed so that its lamp glows with 120 the unit useful for point -to -point trac- volts on X and Y. An autotransformer is ing. The blocking condenser makes it useful in making these adjustments. possible to apply the test prod to any When the LOW indicator glows it indi- part of a circuit without danger of A combination radio-record player for all shorting. occasions. Radio is 6 tube superheterodyne cates a voltage of 100 volts or more. with built -in loop. Controlled reproduction When the HIGH indicator glows it indi- LEON G. BROWN, of both radio and phonograph. Permeability Benton Harbor, Mich. tuned detector, oscillator and IF, for 110V- cates that the upper limit has been ex- A.C., D.C. operation. ceeded. STANLEY E. WEBER, r----= $33.50 Arcanum, Ohio Your Cost i I ,'.01 L_- TEST PROD 3 Lot Price $31.95 CHANGER SUPPORTS 600\[x___ GND CLIP. Record changers are difficult to repair unless supported so that the under- J 1 'SMALL BUZZER side can be reached with ease. To solve 2 SMALL FLASHLIGHT CELLS this problem, I obtained some lengths of sash chain and four hooks, normally 4/T. V.C.& SW used to attach the sash, and a screen Covers the Globe door spring. The spring is cut into four R.F. COIL SHIELD 3 -inch lengths and loops formed in each SHIELDED LEAD TEST PROD end. 509 ARCH STREET PHILADELPHIA, PA. Each spring is fitted with a hook on Export Orders Filled Promptly one end and a chain on the other. The Cable ALRAD free ends of the chains are fastened to GND CLIP the ceiling, over the workbench, on the 46 RADIO -CRAFT for JUNE, 1947 ., COMMERCIRIC AIR `LINE`S''`AfR"CH'ARTER PLANES YACHTS tHOME RADIOS FISHING VESSELS AIR FREIGHT HAM OPERATORS Brand New Automatic Direction Finder SCR- RADIO - COMPASS 269 -F 00 COMPLETE \ WITH j COMPONENT PARTS

The radio compass SCR -269 -F was designed to be the primary radio Plotting fixes is accomplished by selecting two or more stations and navigation compass for the United Stoles Army and Navy Air Forces. plotting these on the navigation mop. The point of intersection of these Constant reception it possible dey or night so that fixes can always lines indicates the location of the craft. be made to establish the plane's or ship's location. This equipment comes complete with 17 tubes superheterodyne The azimuth Indicator is divided into 360 degrees and is connected receiver which is tunable from 200 -1750 KC in three bands. A com- to the loop antenna, therefore making it possible to navigate the ship plete instruction book for operation and maintenance accompanies in any direction as preset on the dial. this equipment. COMPONENT PARTS C. Stock No. Quantity S. C. Stock No. Quantity S. C. S lock No. Quantity S. 1 IN -79 3G579 Radio Compass Receiver BC- 433- F 2C3016 F.I I Plug P1 -112 2Z7212 Insulator 1 Insulator IN -81 30581 Radio Control Box BC -434-F 2C3324 F.I 1 Plug PL -118 2Z7218 I Shaft Casing and Spline Orive....22A124 /16/4 Mounting FT -213 -A 226721 -213A 1 Plug PL -122 2Z7222 F 2ZA124 /1 Mounting FT224 -F 226721 -224F I Dehydrator Hose, Fitting IL Clamps 1 Shafting /MC- 124(3001 F 2ZA124/2 Loop LP -21F (Includes Dehydrator(.221921 F.1 10 foot lengths 228727 5 Nut /MC -124 5 F /MC -124 2ZA124/4 Cord CD -365 -A 3E1363 1 Operating & Maintenance Handbook Spline 5 Sleeve F /MC -124 2ZA124/S Indicator I -814 2Z5381F 1 Coupling MC -136 323266 1 Tronslormer C289AS -R16 -T Relay SW -172 2Z7672F 1 Tuning Shaft MC -124 (300') 2ZA124 -300 MODULATION 1 K TRANSFORMER 1495 RCA modulation transformer is conservatively rated at 550 Watt audio to modulate that new KW rig. Really rugged construction with protective i flashover gaps, which are adjustable. Terminals and gaps ore mounted on a "Mycolex" terminal board. The laminations that make up this transformer are of high audio quality and are extremely thin, making it impossible for BUTTERFLY the core to "chatter or talk ". - CONDENSERS Audio Watts -550 Sec. 91 -450 Mils Sec. f2.80 Mils Turns I V' Ratio -Fri: Sec. f1 -1:1 Pri: Sec. f2-5:1 Prit Sec. P2 Top-25:1. Typet 8 -fre (1 C TRANSMITTER Impedance Ration-Pri: 11-1:1 Sec. Pri: Sec. E2 -25:1 Pre Sec. f2 Top 625:1. "yam range r eta DC Resistance -Pri: 135 ohms Sec, f1, 112 ohms; Sec. f2, 99 ohms. 300 to i & RECEIVER Transformers insulation tested. Pri. 8000V.; Sec. F2- 2000V. to the rest of megacycles to modulate the coils and core. Primary center lapped for Class "B" modulators. Secondary f2 will carry 80 Mils Cot. No. BC -2 plate to $1425 of beam power or screen grid tubes. Primary will match any Class "8" tubes up to 10,000 ohms Power Transformer 805'1, 2037's. plate, such as 810's, 75T's, s 8005's, 28120's, 203's, HY51 Z's, 211's, 813's, 828's, Weight approx. 40 lbs. Pri. I15V 60Cy. The famous boat anchor,wideiy Size 91/2' wide, 7'/ deep, 71/4' high. Heavy channel iron mounting brackets. 255/255 SOMA used on 144 MC bond. Ship Sec. I- ping weight 100 lbs. Your BC 191 TRANSMITTER S 60 BC 654 TRANS. & REC. Sec. 2.3V 3.8A $ 29 price, less tubes and power SCR 625 MINE DETECTOR Less tubes and tun. $1495 49 2 Used with tubes x1495 Sec. 3-.5V 4A l- Vonsformer $14.95 ing units. - FILAMENT TRANSFORMERS MICA CAPACITATOR Thordarson 6.3 V 4 amps., 6.3 V4.5 .002 MFD 3000 VDC. Cal. No. 49c amps., 9.7 V.5 amp., pri. 110 V AC 25 51 -101 or 60 cy. -Cat. No. FT -11 1.95 IF TRANSFORMER Thordarson pri. 110 V 60 cy. -sec. 6.3 FT -12 1.49 Mevnt.d In aluminum shield V 6 A, CT -Cat. No. 8 HY 150M Cat. No b co,. 1500 KC, with air trimmer, Thordarson choke, mped.n . coveted typ.. Cot. FC 201 .95 No. T -19 95c Thordarson 12 HY 25M choke, Cot. No FC -203 .39 30MC IF TRANSFORMER In square aluminum can, .Itr.r CONDENSERS slag tuned. Cat. No. 1 -20 29c NEW BC 223 AX TRANSMITTER Cat. Cap. Working Your No. MFD. Volts Cost 801 Oscillator and 801 Power Amplifiers, 2 -46 Modulators and 1 -46 Speech C110 1 5000 Oil 53.95 4 Frequencies Master on selector switch. 10 to Amplifier Xtal and Oscillator C111 3 4000 Oil 4.95 meter Comes 30 watts output. Tone Voice or C.W. Mod. Ideal for 80 band. CI 12 1 1000 Oil .44 with 3 coils TU I 7A 2000 -3000 Kr. TU 18 3000 -4500 Kc. TU 25 3500 -5250 C114 8 6000.1 .95 Kc. Black wrinkle ca e. Includes 2 separate roses to store extra coils. Fre- C115 2 600 011 .49 1 volts WVDC quencies chart and tubes included, pocked in original Westinghouse MFD 6000 $7.95 Westinghouse 2 MFD 6000 volts WVDC 10.95 cases, less crystals at this low price. Cot. Westinghouse 1 MFD 10,000 volts WVDC No. MT100 $2995 12.95 TUNING UNIT TUBES with Turning Une BC 375. Approx. 63 BC37SE Gen. Elect. Mope Trans. complete 813 $ 5.45 829 S 2.45 7 tuning units, Dynomotor and Antenna M.M.F.D. cond., roll., RF chokes tubes, 814 4.95 872A 1.95 Tuning Unit Brand Now in original crates 211 1.45 dial., assed mica cond.ns.n $4995 RK60 1.25 VT127 2.95 VR150 .69 2500 WVDC, over $50.00 In Jj J pert+. Co,. No. TU -101 3 75 HRC 20% Deposit Re- quired on All Write C.O.D. Orders, for F.O.D. Detroit. 52.00 Minimum. FREE RADIO COMPANY Michigan sales Bulletin 5249 GRAND RIVER DETROIT 8, MICH. add 3% Soles Tax

RADIO -CRAFT for JUNE, 1947 47 TECHNOTES PHILCO 37 -600 EXPERTS The resistance of the primary of the oscillator coil, normally 2.4 ohms, rises to a very high value -in the order of CHOOSE 50,000 ohms in one case. This coil is difficult to replace or rewind. I was able to obtain an old coil wound "VOMAX" the overwhelming with the choi of experts because its the same size wire on a form that would finest, perfect -d v.t.v.m be- permit it to slip over the damaged pri- cause greatest demand makes mary winding. Wire was removed from greatest production and lowest cost to you. the replacement until its resistance was "VOMAX" gives you o total of 51 2.4 ohms. The old leads were clipped and ranges to directly d.c., new ones soldered in place. The set a.f., i.f. and nr.fs volts up was through huncreds of megócycles, aligned and worked like new. six resistance ranges covering Louis HOLST, 2 10ths ohms through 2.000 meg-' San Antonio, Texas ohms, three output meter -decibel ronges from -10 through -50 db., six direct current ranges measuring . HUM REDUCTION from 50 microamperes through 12 Experience has taught me never to amperes. Most important is the ab- mount a flat type power solute stability, complete freedom transformer di- from usual gr d current errors .... rectly on a chassis made of magnetic and its astronomical input resist- material if any type of high -gain ampli- Let's look at this matter cf what meter you buy seriously .... ance .... or honest 6.6 megohms fier is mounted on the same chassis. for your choice of this, the service tecnnicions basic instru- upon arc., o.f , i.f. and r.f.; 51 and

ment, con spell either peace and profit . or annoyance 126 megohms upon d.c. Voltage Eddy currents will be set up in the and loss to you. You must have the best meter to meet ranges measure from .1 through chassis and disturb the grid returns. "smart' competition. Anc "smart" competition overwhelmingly 3000 volts dc., .1 through 1200 The transformer should be insulated uses "VOMAX." The reason is simple. Other manufacturers volts a. c. have hod to copy "VOMAX" inventions to try to satisfy your If you wont to guard your meter from the chassis with nonmagnetic demand for o modern, post -wor, obsolescence -proof universal dollar investment .... to make it spacers or washers. Brass spacers will meter. Yet, "VOMAX," the perfected v.t.v.m., stands head only once for many years to come work well. and shoulders above all other meters. This is proved by its . then "VOMAX' at its present heavy purchase and use by the Bureau of Standards in Wash. low $59.85 net price is your logical ALFRED J. ELBOZ, ington, by Western Electric, G. E.. Westinghouse, university choice . . . . os thousands more Sydney, Australia after university, by top -ranking industrial laboratories. F.C.C., wise technicicns like yourself hove

C.A.A., Veterans Administrations, schools, col eges ... . proved to their profit. . RADIOS WITH LOCTAL TUBES When working with sets with loctal tubes, you may find that tapping or mov- NEW IMPROVED ing the tubes in their sockets will cause intermittents or noise. In many cases the trouble can be traced to tube pins which have become oxidized or bent. Buff each pin until bright and then bend each one slightly outward. Ex- Thousands of technicians today rely on "SPARX" dynamic treme care should be used in bending signal tracer to pins save time .... increase efficiency . . the to prevent breaking the glass. cut their costs. It lets you hear and After you have done this, reinstall the see signals . . . . traces signal right tube and allow it to warm up. Tap it. on thru every receiver circuit from an- If the noise is gone the trouble is cured. tenna thru voice -coil .... s shop test JOHN MEDNANSKY, speaker, too. Continuous ' laboratory research has now improved "SPARX" Belle Fourche, S. D. immensely .... creoted the Improved Model .. .. tremendously increased HALLICRAFTERS SX -28A sensitivity .... greatly expanded gen- Complaint: Slight heating of the eral usefulness. And the SILVER policy of protecting your dollar investment pays cut handsomely ... . power transformer, "S" meter hits the a free bulletin tells every user how to convert his "SPARX" into the new, Improved Model in a jiffy ... . pin. goes to prove that for the really serious, profit -conscious technician there's no subst tute for SILVER, that Adjusting the meter potentiometer "SPARX" costing you on y $39.90 is outstandingly the world's best signal tracer. "SPARX" will earn you, has little effect. too, more profits in less lime thon any other instrument you can buy. The meter adjustment control is mounted directly on the metal chassis with its center terminal insulated from Thanks for your patience. Model 906 Signal Generotor is now flawing to your favorite the metal jobber. And what on instrument .... 90 kc. through 170 mc. on fundamentals ... . case. This meter is in the 8 oir- trimmed bonds . .. variable S 400 ti amplitude modulation .... builtin plate circuit and the insulation of the voriable electronic FM sweep . . laboratory triply adjustable attenuator . . . control breaks down, putting an extra metered microvolts . . output 17 microvolt to over 1 volt .. multiply shielded . strays lower than 5500.00 laboratory generators! Yet all this costs you only 589.90 load- on the power supply and drawing net. Better order your 906 now for demand far exceeds production capacity on this full current through the meter. As a precision instrument for months to come. cure, I enlarged the potentiometer mounting hole and reinstalled the control after insulating its shaft with a Send Post Card for Catalog of new measuring equipment, communica- bakelite insulating washer. JAMES C. MCGUIRE, tion receivers, transmitters, kits, See them at your fcvorite Jobber. parts. Los Angeleá, Calif.

. SILVERTONE 6336 OVER 36 YEARS OF RADIO ENGINEERING ACHIEVEMENT Intermittents in this set are often caused by a defective oscillator grid condenser. This unit changes its value in- termittently. Replacing it with a high - I'/ WO4404. C5 1Pe VYei 9"C. quality 50 -µµf condenser will clear up ST.,- HARTFORD 3, CONNECTICUT the trouble. 1249 MAIN MCCLESKY RADIO Co., Baton Rouge, La. 48 RADIO -CRAFT for JUNE. 1947 RADIOMEN'S HEADQUARTERS -ID WORLD WIDE MAIL ORDER SERVICE! ! ! GENERAL ELECTRIC SERVICEMEN Check This Column for Lowest Prices on Quality Puts Tuba: A warehouse full, including the now miniatures. Order all 150 WATT the types you neod and we will try to supply you completely. The following prices are for fifty or mere tubos, assorted, 5% less TRANSMITTER on lots of 100 or more. 27. 5Y3, 80, 38e: 28, 3575. 56, 75, 44e; 78, 78. 675. 5Ce: 6SK7, 6907, 128Á7. 12SQ7, 5U4. 6C6, ODO, 6SA7, 54e; 6877, 12837. 5Y4. 57.3. 6K8, 610, 6V6, Cost the Government $1800.00 6807, 60e; 6J7, 6K8, 65E7, ne; 51,4, 6F7, 12B56. 12AT6, 88e; 815, 99e: 321.7, $1.08; 5085, $1.2& These special prices Now only $44.50! on tubes are for one month only. POWER TRANSFORMERS -Hag -shell type. 110V. 60 cy, Centertapped RV w.nding. Specify either 2.5 or 0.3V Ola- This is the famous transmitter used in U.S. ent *hen ordering. Army bombers and ground stations, during For 4-5 tubo seta -650V. 40MA. 5V & 2.6 or 8.3V $1.49 the war. Its design and construction have For 5 -6 tube sets -650V. 45MA. 5V & 2.5 or 6.3V 1.75 been proved in service. For 6-7 tube sets -675V. SOMA, 6V & 2.5 or 6.3V 1.90 under all kinds of 2.35 conditions. all over the world. The by means of For 7 -8 tube sets -700V. 70111A. 5V & 6.3 or two 2.5..: entire frequency range is covered 5V & 6.3 or two 2.5V 2.8.5 plug -in tuning units which are included. Each own oscillator and For 9 -11 tube sets 700V. 100a1Á, tuning unit has its 9 -15 tube sou -600V, 150-A, 6V & 6.3V 2.95 power amplifier coils For and condensers. and antenna tuning circuits-all designed to operate TRANSFORMERS -All types In stock. AUTO- TRANSFORM- at top efficiency within its particular frequency range. Transmitter and accessorise are ERS; Steps up 110v to 220v. or stops town 2200 to 110v- S1.95. finished 'in black - crackle, and the milliammeter, voltmeter, and RF ammeter are mounted FIL. TRANS.: 6.3v. 8 Amps.-51.98; 5r. 10 Amps. -31.98: on the front panel. Here are the specifications: FREQUENCY RANGE: 200 to 600 KC Universal Output Trans. 8 Watt-89e; 18 Watt 11.29: 30 Watt and 1500 to 12,500 KC. (Will operate on 10 and 20 meter band with slight modification). $1.69. AUDIO TRANSFORMERS: 9. Plate to S. grid. 3:1- OSCILLATOR: Self- excited. thcrmo cómpensated, and hand calibrated. POWER AMPLI- 79c; 8. 'Plate to P.P. Orlds -79e; Reed Duty Class All or 13. P.P. inputs -41.49: Midget Output for AC -DC sets -690; FIER: Neutralized class "C' stage, using 211 tube, and equipped with antenna coupling similar which matches MIKE TRANSFORMER for T -17 Shure microphone, circuit practically any length antenna. MODULATOR: Class "B" -uses to UTC auncer type -$2.00. two-211.tubes. POWER SUPPLY: Supplied complete with' dynamotor which furnishes CONDENSERS -PAPER TUBULAR 600' WV -.001; 002. 005 1000V at 360 MA. Complete instructions are furnished to operate set from 110V AC. -8e; .01, .05 -9e: .1 -loe: .25-23e; .5 -36e; ELECTRO- SIZE: 211/2x23x914 inches. Total shipping weight 200 lbs., complete with all tubes, dyna- LYTICS: Smfd 200v -20e: lOmfd 31v -20t: 20mfd 150v -230; motor power supply. the essential plugs. 20 /20mfd 150v -35e; 30/20 150v -46e; 60mfd 150v-43e: Smfd tuning units, antenna tuning unit and 600v These transmitters are priced to move fast: Order today and be the proud owner of one 475v -34e; 16mfd 350v -85c; OIL CONDENSERS: 4mfd of the finest rigs obtainable. - 49e: BATH. TUB TYPE CONDENSERS: SX.lmfd-200; RE- SISTORS: All types In stock at the lowest prices; Resistor BENDIX SCR 522-Very High Frequency Voice Transmitter- Receiver-100 to 156 MC. This Kite: 11.0 2 watt resistors -$1.95. duty -59e; job was good enough fin: the Joint Command to make it standard equipment in everything FILTER CHOKES: 200, B00, 400. 500 ohm light 200 es 300 ohm heavy duty -99e: 250 ma 35 ohm. made for that flew, even though each set cost the Gov't: $2600.00. Crystal Controlled and Amplitude or 25 for gave U.B. Navy, fully shielded- $1.95; 75 ohm 125 ma -25e Modulated -HIGH TRANSMITTER OUTPUT and 3 Microvolt Receiver Sensitivity $4.25: "Meissner type" tapped filter chokes-25e; 8 amp. iron good communication up to 180 miles at high altitudes. Receiver has ten tubes and trans- core A filler -25e: Choke -condenser combination. Ideal to re- mitter has seven tubes, including two 832's. Furnished complete with 17 tubes, remote place any size speaker field when installing PM speakers -79e. control unit control unit, dynamotor and Ant. $37.95. 110 V. CIRCUIT BREAKERS of Magnetic cape: Following Current Ratings in Stock; 1.25, 3. 4. 8 Ampe. Please specify. We include tree parts for the worm-Mon to continuously variable frequency coverage in the receiver, as $1.95. well es circuit diagrams for operations of the unit on 110V A.C. SEVEN ASSORTED I.F. TRANSFORMERS-$I.98; Five Colls -69e. -274 including 3 separato 0 tube superhet receivers. 2 separate transmitters, each AWL. Oscillator SCR N COMMAND SETS, batteries for O.E. with 44 .watts output, modulate and DC power supply. Bargain price for all 6 pieces ccenplete with WILLARD rechargeable 2 volt storage tubes $29.95 portable radios $2.95. SPEAKERS-PM dynamic type -4'$1.55: 5" $1.55: 6 "$1.95: AIR CRAFT MARKER BEACON-Complete with 9 tubes and sensitive relay to control exit-rani circuits 12"$7.50. to control open edoon from 8"$3.95; 10"- $5.95; from received signals. Just the receiver you have been welling for models 6 Watt $4.95 PHONO AMPLIFIERS -A real AC, 110V. 00 Cycle, distance, etc. Priced at only - Amplifier suitable for PA systems and phonographs: with a AIRPLANE AMPLIFIER C1 contains 3 -7N7, 3 -7F7, and 1 -7Y4, In aluminum case 9raz7" $9.95 husky power transformer. Complete with tubes- $12.95. Watts output, 6 RECEIVER-Completo with 17 tubes and 200 Kc. calibrating crystal $39.95 PUBLIC ADDRESS AMPLIFIERS -26 peak BC-654 TRANSMITTER tubes. separate controls for Microphone and Phono Inputs. $63.00 value for 'posy $32.00. Crystal pick-up, phono motor and turntoblo-$5.25. LINE FILTERS-110V --each unit contains two 2 mfd. oil Oiled condensers and a 15 amp. Iron core choke. This filter 5" Receiver Indicator Oscilloscope with 31 Tubes has innumerable uses such as oil burner line filter. etc. A ten This unit, sold by Western Electric for $2600.00, includes a 13 tube dollar value for ¡Sc. headsets with receiver with 7 IF stages; 2 tube. multivibrator sweep generator; HEADPHONES -Highest quality Signal Corps sponge rubber oar cushions. cord and plug $1.00. 5' rubber 2 tube sweep video amplifier: pedestal impulse and lY amplifier; covered patchcords with phone plug and socket-25e. sweep and 115 V. 60 cycle supply with 2X2 for high generator; RELAYS - Guardian SPBT 12 -24r. has heavy duty 15 Amp. voltage. Makes a wonderful laboratory instrument, or can be more Contacts- $1.25; Guardian 12 to 24r D.C. triple make, single easily converted to a complete home television receiver than any break relay, 5 for $3.75; Sigma supersensitive 2000 ohm D.C. other war surplus item. Only $69.95 SPDT Belay. (slay be adjusted to operate oa lees than 1 Milliampere) -92.50. 6 POLE. DOUBLE THROW. Telephone Type 2000 ohm Bo- 13 Tube BC412 Radar Oscilloscope-Easily converted .to a superb laye. Super Sensitive, $2.50 each, or two for $4.50. 1 ". 1.2 laboratory oscilloscope by a little work. Already 110V. 60 SELENIUM RECTIFIERS-Dry disc typo 154" by just Amp. maximum, suitable for converting DC relays to AC, for cycle $59.95 supplying filament source In portable radios. converting DC meters to AC applications; and also may be used in low current chargers-90e. METER RECTIFIERS -Full wave. may be used for replace- BC -947A ONE KILOWATT HIGH FREQUENCY TRANSMITTER -This relay -controlled transmitter in: ment. or in construction of all types of test equipment-41.25. eludes a 115 V.. 60 cycle power supply. protected by 3 magnetic circuit breakers, that alone is worth lialf Wave-90e. more than the price we are asking for the whole rig. even on today's surplus market. On.the.front panel WIRE -No. 18 POS3 2 conductor parallel eipcord. brown, 250 ft. aro six 355- GB or Weston meters, including 250 SIA, 50 TIA, 1000 MA. 150 V. A.C.. and 1500 V. D. C. spools, $4.25: 500 ft. spools. $7.95: Na 1S PO brown rayon at 1000 ohms per volt for screens and plate. The Back -type 2l "x16 "x36" unit contains a amplifier-and rec- covered parallel lampcord. 500 ft. spools. $7.95; No. 18 ST tifier tubes aggregating over $60.00 at WAA current wholesale prices. Western. Electric =a price to the bound rubber covered double were for warp machines. vacuum government was $1500.00. Shipping weight 500 lbs. Your cost, as le, - only ' $69.95 cleaners, etc., 250 ft. spools, $ 6.95: Rubber covered mike cable, 6e per foot; RGSU 50 ohm coax cut to any length. 8e per foot; single stranded conductor shielded lead with brown rubber over ih eld, super apolal, $1.20 per 100 ft., $10.00 per 1000 ft. All k'nd, of hook -up wire. le per foot. BC 221 FREQUENCY METERS with calibrating Crystal and calibration'eharta. A precision frequency standard that is useful for MICROPHONES -All nationally laboratory technician, service man. known brands. Buaot crystal-$5.45; innumerable applications for Bullet Dynamic- $7.45; bilk° Jr.- amateur, and experimenter. at the give away price of only $39.95 60e; Handy alike -90.4 7.apel Mike- 93e; SHURE T -l7 DIKES. with push 5BP4 CATHODE RAY TUBE, 5" tube at the lowest price ev.r to talk switch -99c. -offered 20 .Á897'D COIL FORMS. including 11 ceramic. S polystyrene, and 6 fiber, all us-ful sixes-Me. V A R I A B h E CONDENSERS: 350 MIMED. 5 gang -$1.95: 4 gang -$1.49: GENERAL ELECTRIC RT -1248 15 -TUBE 3 gang -88e; 2 gang -79e; 7.5 to 20. MMFD, 1759v sportingg extra long -RECEIVER shaft Hammarlund$9e: miniature TRANSMITTER variables. 25 711IFD --39e; 50 AIMED -49e; 75 afMFD -59e; 100 MSITD- TERRIFIC POWER -(20 watts) on any two instantly selected. easily p e- adjusted fre- -69e; 140 MMMFD -79o. quencies from 436 to 600 Mc. Transmitter uses 5 tubes including a Western Electric 316 A TRANSMITTING RF CHOKES. 4 PIE. 850 Ma. -25c or as final. Receiver uses 10 tubes including 956'9, as first detector and eaci lator, and 3- 4 for 51.00. super,regenera- 71I7's IF's, with 4 slug 40 Me. IF transformera. plus a 7H7, 7E6' and 7F7's. In INTERRUPTION FREQUENCY COILS. for as -tuned tire receivers or the tromendously popular FM adapters for addition unit contains 8 relays designed to operate any sort of external equipment when standard broadcast sets. iron core ith a resonant fro - 12 volt actuated by a received signal from a similar set elsewhere. Originally designed for nuency of 50 K(` -39e: Air Core. 100 KO-29e. operation, power supply is not included, as it is a cinch for any amateur to connect this 30 MC IF TRANSFORMERS double slug tuned -25e. unit- for (10V AC, using any supply capable of 400V DC nt 136 MA. The ideal unit for use VIDEO AMPLIFIER PLATE COILS -Slug tuned -25e. in mobile or stationary service in the Citizen's Radio Telephone Band where no license is REMOTE CONTROL UNIT: Aluminum case 4x3x2" con- RT -1248 transmitter on taining 2 potentiometers. triple pole switch. 4 knobs, gear necessary. Instructions and diagrams supplied for running the mechanism. and phone use as a mobile counter 1soks$9c. either -obde Or voice, in AM or FM transmission or reception, for public MODULATION TRANSFORMERS -30 watt. metal case address system, as an 80 to 110 Mc. FM broadcast receiver, as a Facsimile transmitter . or 98c; 30 watt; open -type, $1.95: 40 watt east aluminum receiver, as an amateur television transmitter or receiver, for remote control relay hook - case, $2.95; Class "B" input transformers, cast aluminum ups, for Geiger-Mueller counter applications. and it sells for only $29.95. 10% less if case, 81.95: Transceiver audio traneformerrs. 65e: Transceiver 2 more.- desired for marine or mobile use, the dynamotor which modulation transformers, 65e. 'ordered in- lots of. or If 150 Volt AC meters. 2%"' diameter-$2.49. ,will work on either 12 or 29V DC and supply all power for the set, is only $15.00 additional. BUFFALO RADIO SUPPLY, 219 -221 Genesee St., Dept. ISC, BUFFALO 3, N. Y. Cabla Address: BUFRAD RADIO -CRAFT for JUNE, 1947 49 ,mnummnnnmmnmmmmommmmnnnnnnunmmmmnnmmmlmmmnlmnmmnmmmlmnmmmlmmmmmmnmo

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. i .,mnnnnmmMmmmmmMmmmnnnnnmmmmmmmm11nunmmmmnnunnmmmmmmmmnmmunnunmmmmnmmMmmmnlmmnlmnb

greatest frequency deviation from the combination that may be constructed maximum applied audio input. very compactly. These tubes may be ob- The r.f. chokes consist of 20 to 25 turns of No. 24 s.c.c. wire wound BASS- REFLEX ENCLOSURE tained in the GT /G series. When they to an with midget i.f. transformers, inside diameter of z inch. Slight vari- I would like to have plans for con- are used very little space is consumed. ations in each choke are recommended structing a. bass -reflex enclosure for a to prevent parasitic oscillations. 15 -inch speaker. -C.O.R.; Kansas City, Kansas. 41 FM RECORD PLAYER A. A bass -reflex enclosure design is Please print a. diagram of a. fre- COIL DATA quency- player to be shown in the figure. modulated record 1 am building a. superhet. receiver The hair felt or rock wool pads are used in demonstrating. FM receivers on to cover from 550 kc to 25 me when us- placed tó absorb the high frequency the 88 to 108 me band. -G.V., Spokane, ing 365 -1.4f condensers and an inter- notes coming from the rear of the Wash. mediate frequency of 465 kc. Please sup- A. Here is the circuit of a four -tube ply me with winding data for antenna, 9 ' I + l SB I FM record player for use on the new oscillator, and r.f. coils. What size pad-. 51/4" Á i 1 r p-I I/2 bands. It uses a 7A4 speech amplifier ding condenser should I use ? -C.W.W., ; L_ ; ;;, SPEAKER Ì followed by a 7Q7 modulator. Another Paul, Minn. __ ._I I St. III 1131/Y" 'i

1 4ii i ¡ jll' ' .05 500K 7A4 .05 FREQ.7Q7 4002 7A4 -- -- I 323/4 111 ' DEV. LI - -- ,.t-é/t1 IOµµl1 50K 3.30uut i CONI 1.2 __ _..-,J, 1 21t/Ó PHONO 0'0005 ii PICKUP 5 3/4" I B-11 I 1 Ì 1 V R r 500Kg 1 I - - J Lt f3 y L3/410 20 + IOOK RFC2 RFC 3 F- V-2 51 2 r i J- 1 5K 1W. .01 IOK /5W -i. 25V. 2.5K I.-251/2 -133/4!--J 16/450V. 8 /450V. speaker. The exact size and placement 6/450v. 450V.+ 1W. a of the pads depends upon a number of 50K 20K 3W. variables including speaker and wood characteristics. Experimenting with the W. size and placement of the pads will result in optimum performance. 7A4 is used as the reactance -modulated .012 6.3V.TO FILS oscillator. ,' II7V.AC 7Z4 PHONO -RADIO 50v ION/301.4A The oscillator 4 I would like to have a diagram of coil Ll consists of turns of No. 18 bare wire on a % -inch an a.c: d.c. phonograph and radio com- 40/450X bination. form. The winding is spaced to cover % It should be capable of being inch. The position built very compactly as I want to mount of the tap may be located best by experiment. L2 has 2 it in a small portable case.-P.S., Chi - cago, Ill. turns of No. 18 enamelled wire closely A. Here are the coil specifications. All coupled to Ll. coils are close -wound with enamel wire A. Here is a circuit for a phono -radio Cl may be varied to obtain the on 1 -inch forms.

12SA7 LE 12SK7 R.F. Ose Grid Ose Plats 35L6 Coll Wire Coil Win Coll Win .0021 a Band (Me) Turns Size Turns Size Turns Size 0.55- 1.5 146 32 92 82 20 82 .01 IItTO 1.60- 4.0 36.2 30 80.9 80 12 80 SPEAKER 4.0 -10.0 10.1 30 9.7 80 12 36 10.0 -25.0 4.4 20 4.8 20 6 86 The oscillator coils for the 0.55 -1.5- ' and 1.5- 4.0 -mc bands are wound with the plate coil over the primary, the B- plus end being toward the primary's 68V.,150 MA, PILOT. grid end. For other bands, the coils are wound side by side with 1/32 inch be- j.02 53 660 = tween them. The grid and plate connec- 2 tions are then made to the ends of the T40 30 + 450V 250V T coils with the B -plus and cathode con- T nections at 300 35Z55 the center. Padding con- A A A densers are 400 µµf, 1,070 µµf, 2,900 µµf, u PHONO MOTORTi 21/5W 35L6 12SK7 12SA7 12501 ®SW. -i- and 7,300 µµf, respectively, beginning at the broadcast band. 50 RADIO -CRAFT for JUNE. 1947 V.F.O. EXCITER OR TRANSMITTER (Continued from page 30) ed excellent. Not until à 0.5 -µf fixed condenser was added across one side of the power line and ground were we able to clear up the signal of the v.f.o. Evident- ly radiation had been picked up by house wiring and had modulated the oscillator supply. The frequency of every oscillator depends to some extent upon plate and screen potentials. Turning on a light or electric iron will cause a variation in voltage which in turn will change the oscillator frequency. Even the transmitter itself constitutes a variable load as it is keyed. These voltage changes are made negligible by using the common voltage- regulator tubes. These are widely available as surplus items and are easy to connect into regulating circuits. It is advisable to regulate riot only the oscillator potentials but the following buffer as well. Drift is due to heating of tube elements, components, and wiring. Mica and paper condensers cannot be used in critical circuits. The more expensive ceramic type of condenser has a low Radio Parts temperature coefficient so its capacitance remains constant. In any case thé transmitter should be left on for several minutes before calling since there is al- Radio Sets ways an initial drift. Chirp is the result of a change in fre- Radio Hams Servicemen Engineers quency while a rig is being keyed. This Sound Men Maintenance Men Liam Gear Schools Institutions Manufacturers be due load, may to a changing oscillator THIS CATALOG IS FOX YOU! blocking, or an unstable oscillator. It is often claimed that the oscillator should iVW/4 COUPON TODAY! be left running at all times for best re- Amplifiers sults. On the other hand, keying the oscillator permits break -in as soon as the key is up. In addition, intermittent Industrial Electronic and Test Equipment oscillation prevents too great a change in temperature between intervals of It's here -ready for you now -the new, comprehensive, 1947 transmission and reception. With a well - Concord Catalog displaying a vast, complete selection of every- designed high -C oscillator there should in Radio and Electronics. Send for your copy now. Select be no chirp during keying. On the other thing hand, it is quite possible that keying the your needs from value -packed pages showing thousands of items final or a buffer may introduce serious available for IMMEDIATE SHIPMENT - hundreds of them now chirp. Unless isolation is complete, key- available for the first time -featuring new, latest 1947 prices. See ing any stage will vary oscillator loading the new LOWER prices on finest -quality RADIO SETS, PHONO- and frequency. To check for this condition tune the stage through resonance. RADIOS, RECORD CHANGERS, RECORD PLAYERS, PORT- If there is no noticable change in fre- ABLES, AMPLIFIERS, COMPLETE SOUND SYSTEMS, TEST- quency, that stage may be keyed. ERS. See complete latest listings of all the well -known, standard, In checking for chirp, drift or un- dependable lines of radio parts and equipment- tubes, condensers, steady signals, it is most effective to lis- transformers, relays, resistors, switches, speakers -all available for ten in at some high harmonic of the signal. As mentioned before, any change IMMEDIATE SHIPMENT from huge stocks in CHICAGO and in frequency is multiplied by the order ATLANTA. Whatever your needs in Radio and Electronic Parts, of harmonic. Supplies and Equipment- before you buy -SEE THIS GREAT NEW In addition to technical problems CONCORD CATALOG. Mail coupon for your FREE copy now. which accompany a v.f.o., there also seems to be a psychological handicap. Some hams feel that all such rigs are Concord Radio Corporation, Dept. RC-67 inherently unstable. While an easy -to- 901 W. Jackson Blvd., Chicago 7, III. read and stable signal always gets a Yes, rush FREE COPY of the comprehensive T9X report and little additional com- new Concord Radio Catalog. ment, it is sometimes true that far more R A D I O C O R P O R A T I O N critical listening follows if the signal is Name known to come from a v.f.o. Actually, CHICAGO 7 * ATLANTA 3 Address of course, even a crystal oscillator is 901 W. JACKSON BLVD. 265 PEACHTREE ST. subject to many of the ills of the variable LAFAVETTE RADIO City State oscillator unless it is correctly designed. I J

RADIO -CRAFT for JUNE, 1947 51 5000P, RADIOaELICTRODIC DPYICES` BC -654 Transmitter ,-- -, -r- Receiver a NET $12.95 INTERCOMMUNICATOR quartz crystal in an aperiodic oscillator Lc i Portable voice and CW Rauland Corporation of Chicago circuit. Provision is made for slight fre- - transmitter and receiver is for portable, mobile. and Chicago, III. quency correction to enable the operator s pif fixed station operation. 7- The Amplicall master station unit is to adjust the crystal frequency to ex- -$ - tz tube superheterodyne re- _- . t- ,. celver with 3.5 microvolt available with or without handset (for actly 100 kc by zero- beating a harmonic Y, ... seilsitivilY oil voice and 0.5 microvolt sensitivity completely private conversation). Dis- with the standard frequency transmis- on CtV, and 100 mllliwatts undistorted power output. 955 KC IF. Uses 3- IN5GT, 1- 1A7GT, 2 tinctive features include visual busy sion of the U. S. Bureau of Standards -3Q5GT, 1 -1H5GT tubes. 6 -tube transmitter with individual locking -type push ntonna tuning network. Colpitts thermal compen- signal, transmitter WW V. ated oscillator. class C final with 2- 307A tubes buttons for station selection, illuminated It is completely self- contained except n parallel. and crystal oscillator for checking (re- ency every 200 KC 25 watts output on CW and for power supply. Leads are brought 1.2 walla output on voice. Frequency range. transmitter and receiver. 3800 to .5800 KC. Ideal for out for easy connection to the receiver's lama) Comes complete with cover; set of tubes In- power supply. The power , is talled, 5 spare tubes and 9 spare pilot lights. Less required drier supplice. These units are aced but in good negligible: 6.3 volts at 0.3 ampere for condition. Shipping weight 50 lbs. Net price with II tubes and spares 512.95 the tube cathode heater, and approxi- The 654 unit. only. shipped from our Chicago warehouse. Send your order to Kansas City. mately 2 milliamperes at 200 volts for BC -645 I.F.F. $14.95 the plate and screen -grid supply. The plate and screen potential is not critical ' ~'_ ARMY BC645 and may be anywhere from 100 to 300 O^" ' I.F.F. UNIT. Net ,, $14.95. Early in the i ..I o when radar -,,.,, ,v ,by picked up a plane, ,3 there as no way t ¡./ '1T . of knowing whether .e't 0'4 ...q.:+v tt was friendly or ON -OF? volume control, plug -in cable t _ . f.1: ,., not. That as before BC645 was connections, and a balanced line wiring "" ' "- -w '- invented. BC -645 sont out a signal system which prevents cross -talk. Sys- hat identified the plane as American. It probably aced more lives than any oche piece of electronic tems are available with facilities for the equipment made. With soma modifications the set can use of to 24 be used for 2 -way communication. voice or code. on up master stations, permit- ho following bande: ham band 20 -950 mc., citizens ting as matey as 12 conversations to be a llo 4G0 -470 me.. fixed and mobile 950 -960 me.. elevision experimental 470 -500 me. Equipment capable carried on simultaneously. RADIO- of doing - the Jobs of the mollfi d set sells for hun- reds and hundreds of dollars. The 15 tubes alone are CRAFT worth more than the sale price. -7F7, 4 -7H7. 2-7E6. -OF6. 2 -955 and 1- We310A. It ow covers 460 to 490 mc. Each BC -645 is shipped col h a Belmont factory Printed conversion diagram, allowing how to make AC PHOTOELECTRIC Power supply modulator and how to make Transmitter ACTUATOR ani Receiver changes. Most Hams and experimenters Potter Instrument Company already have the few parts necessary. New 11C -645 with tubes less power Supply $14.95 Flushing, N. Y. ' Two for 29.00 The Model 600 photoelectric actuator 12 volt D.C. Dynamotor 4.95 Extra 316A Door Knob tubes 1.29 is a high- resolution instrument for Brand New Aircraft - counting pills, buttons, watch screws, Receivers BC '?% bottle caps, hardware, and other such -454 items. The unit has a beam approxi- 3 to 6 M.C. vo ts; recommended voltage is 200 to mately 1/16 inch wide and will respond 250. scoop to changes in light level as small as J' The frequency standard is mounted - :1j 20 percent. Since complete interruption PRICE 295 ® k in a drawn aluminum case 2 by 2 inches These Army surplus aircraft receivers may be op- square, and 1% inches high, and is erated from a 24 volt AC filament supply and any low power 250 volt B supply; or the tube changed equipped with 2 convenient mounting to the 6 volt type. There is plenty of room for a The power transformer and rectifier tube; In place of brackets. tube and crystal are the dynamotor. This receiver is very selective and plugged into the top of the unit. With sensitive: has RF stage and BFO. Made by Western Electric and you never saw finer wiring. Offered com- the tube and crystal in place, the total plete 12SR7 and 12A8, but lwith 2tuvest 12ES. 3- 125K7. height is approximately 3% inches. RC- 454 -B-3 to 0 MC superhet receiver with -CRAFT all tubes. Net 35.95 -RAD2o Less tubes. Not 2.95 of the light beam is not required for 28 volt dynamotor (snaps on receiver chassis) Net 1.95 normal operation, objects as small as (Shipping weight of above ree. 8 lbs.) POCKET -SIZE 10 /1000ths of an inch have been counted OHMMETER Aircraft Transmitter with Sylvania Eleotric Products, Inc. absolute accuracy. This feature New York, N. Y. SCOOP PRICE $9.95 mati also permits the counting of objects Up to 55 watts output from --- A miniature ohmmeter has been de- these trans. according to what y which do not have a distinct separation. supply use. signed particularly for use by service- Power You Ideal to . I ®II make over for a master ose. The actuator provides the negative c fn] men as a pocket indicator for prelimi- priced complete with tries I® pulses for operation of electronic count- 12J5 and two 1025. Has built in - nary isolation of electric faults. In radio crystal for dial callhratier. rt; ers, and is designed to detect objects at Used but In good condition. C`- set servicing the ohmmeter will indicate BC 457 9 to 5.9 MC with e ea rates up to 30)000 per minute. The unit tubes. net $9.95 f transient or other faults in difficult re- BC 958 5.3 to 7 MC with contains a capacitor discharge output placements including i.f. transformers, tubes. nit 9.95 circuit for the high -speed operation of Parts Salvage ás ri,p1- control solenoids such are required = SCOOP $2.49 for deflector gates and packaging equip- : t - BC 456 WESTERN ment. ELECTRIC MODULA- TOR. Buy this unit and take it apart for the pieces. Electronic counters of various capac- Chock full of condensers, resistors. relays and tubes ities, predetermining features, and out- VR 150 1235 1685.. Also has a handy modulation transformer which is worth more than our salo put circuits also are available for opera- price. We have several thousand of than to sell at this scoop price. tion with the Model 600. -RADMo -CRAFT BC 456 Modulator with tubes, not 52.49. two for 54.49 DYNAMOTOR SCOOP. 28 volts DC input 540 volts at 250 mills output. Scoop price. not 52.95 NO FULL C.O.D.'S FREQUENCY STANDARD 20a/a DEPOSIT, SAL. C.O.D. WRITE FOR FLYER. Hammarlund Mfg. Co. New York, N. Y. McGEE RADIO CO. The type FS -135 -C frequency- stand- 1223 -C McGee St.; KANSAS CITY; MO. ard unit consists of a precision 100 -kc 52 RADIO -CRAFT for JUNE, 1947 tuning units, and audio sections; approximate values of individual resistors; and open or shorted conditions in other RADIO circuit components. It also provides a GOVERNMENT direct- reading means for spot- checking SURPLUS automotive electrical equipment, industrial electronic apparatus, home appliances, and experimental or development RECORDERS electrical circuits. Direct readings between 0 and 10,000 New and Complete with Tubes ohms are given on a 1.5- milliampere, Designed for ink recording of code signals -scale full sensitivity Weston meter in at speeds up to 400 words per minute on 3/6 series with a 1,000 -ohm molded carbon inch paper tape. Input may be connected to resistor and a penlight dry cell. telephone line transmitting radio signals or The ohmmeter is enclosed in an at- directly to output circuit of receiver. Self - tractive tubular plastic case 7rß inch in Eontained, only requires connection to power diameter and 5% inches over all. The supply and signal source. prod tip base and top cap, constructed Net Description Height Width Depth Weight of green molded bakelite, are mounted Recorder BC -1016 10%" x 191/4" x 14% 80 lbs. in a transparent cellulose acetate tube Tube Complement, Vacuum: Power supply:- Operates on 110 Volts: 50 -60 cycle alter. housing the meter.-RADIO -CRAFT noting current. I Tube VT -116 -A RMA 6517 -GT Input signal: -0.75 and 50 volts required for operation. be obtained several ways, for I Tube VT -90 -A RMA 6H6 -GT May PIONEER ATOM SPLITTER example: I Tube VT -231 (Continued from page 23) RMA 6SN7 -GT a. From receiver connected direct to $ 500 3 Tubes VT -I 15 -A RMA 616 -G recorder b. From telephone line carrying signal 2 Tubes VT -244 the passage of a. single electron through RMA 5U4 -G to ecorder from a remote location. F.O.B DETROIT its gas chamber. Where the number of counts per second is too great for the mechanical relay in the plate circuit of the final amplifier to handle, other circuits have been constructed which supply one impulse to the relay for every two (or higher multiple) counts. These scaling circuits may have a factor of 4, 8 or higher numbers, or may be based on the decimal system, giving an indication for every 5 or 10 counts. Vacuum -tube quenching circuits further speed up Geiger tube action, by causing the tube to de- ionize more rapidly after each pulse, so that it can count faster and register heavier showers of JUNCTION BOXES 50c particles. Complete with switches, fuse holders, jewels, volume The voltage -regulated power 'supply controls and relays. EACH is by no means to be neglected as a factor in atomic research. Maintenance of voltage within very narrow limits is very important when counters or other instruments are operating over critical portions of their characteristics, as is necessary in some very important types of study. VARIABLE CONDENSERS Regulated voltage supplies, vacuum- Four sections 35 Mmfd plus tube amplifiers and electronic switching one section 50 and one sec- FM circuits have so extended the capabili- tion 250 Mmfd. Complete EACH ties of older research devices as to make ANTENNA them practically new instruments, of Will receive up Write Us About Your Needs which the electronic circuits are funda- ,to 150 Mc. mental parts. Thus it is not surprising No order under $5.00- please. Send check or money order. Orders that an important piece of equipment BEACON shipped C.O.D. subject to 20% ad- "Ince $150 for atomic study and research should deposit. All prices quoted EACH resemble a radio transmitter rack. RECEIVERS F.O.B. Detroit, Michigan. BC- 1206 -C DEMONSTRATION SPECIALS TRANSMITTERS A lightweight, 5 -tube superheterodyne receiver built by (Continued from page 35) Sefchell Carlson. Covers 200 -400 Kc radio beacon frequencies. SPAGHETTI- Bundle 35C Complete with the following the same time taking advantage of the tubes: 2 -14H7, I -14J7, I -14R7. and EAR PHONES -Used, in good working con- same audio amplifier and loud speaker l -28D7. Output impedance 300 dition- complete 5OC ohm with provision for 4,000 ohm for both units and thereby eliminating by slight circuit change. Oper- METER FACES -20 assorted -sizes 2 and 3 $ 00 any change in fidelity from that source. ates from any 24-28 V, DC source. inch 1 Current consumption .75 amp. For the interference source an old May be used in light planes by model "T" Ford spark coil was wired connecting to dry batteries for necessary voltage. No high volt- through a push button to four dry cells age power supply used which and a short length of wire connected to gives the set maximum efficiency. RADIO CENTER the high tension terminal. This created Dimensions: 2530 E. Davison Avenue no small amount of racket in the AM 71/i " = 4'./i 4,495 Weight, 4 lbs. Detroit 12, Michigan receiver yet was thoroughly eliminated Complete when switching to FM. RADIO -CRAFT for JUNE, 1947 53 OPPORTUNITY FOR New Radio - Electronic Patents N;-'\RADIO MEN!, By I, QUEEN Here's the book that can help you make a real profit In ELECTRIC MOTOR REPAIR. lt'a a logical addition to any service business. It's a really worthwhile profes- TELEVISION SWEEP CIRCUIT principle of hysteresis -often known as magnetic sion to know. The geld Isn't crowded. Every home. every inertia because it imposes a lag business, every industry uses mo- Patent No. 2,393,601 between an tors. Train now to be the man who exciting current and the electromagnetism which can repair them! Millard W. Baldwin, Jr., Glen Ridge, N. J. results. This invention is an improvement over exist- Two windings are placed over a suitable iron ing circuits which govern the deflection of an core. An a.c. source excites the primary, one half electron beam by electromagnetism. The mag- of which is wound in opposition and in series netic type of cathode -ray tube is advantageous it with the other half. The entire secondary is I'll Make where the necessary deflection power is available, wound in one direction. If the core is in field -free as in television reception, since the tube can be smaller and simpler. Since the special features EASY for you are associated with the vertical sweep circuit, it need only be mentioned that the horizontal sweep is controlled by a suitable oscillator and deflec- to LEARN tion coils according to present-day procedure. The vertical sweep circuit uses three tubes, the lest two in push -pull for second -harmonic reduction. The input triode is triggered by peri- PROFITABLE odic pulses which cause the tube to conduct and therefore discharge the condensers C. These charge again from the battery through any well -known constant current device and the cycle ELECTRIC MOTOR repeats. The output of the push -pull stage flows through the coils Ll -and L2 and it. consista in general of a residual d.c. component and the signal a.c. REPAIR component. For convenience consider the first portion alone, that is, in the absence of a signal. space, it may be considered as composed of two During these intervals there-should be no vertical equal and opposing electromagnets, end to end. deflection of the beam. The deflection coils Since hysteresis lag depends upon peak magnet- fie at only $5 for the ordinarily carry the current of only one of-the ism, it is equal for each half of the core in this complete, 553 -page push -pull plate currents, and as a result the two case and there can be no induced secondary volt- Course! equal and opposite currents balance out only age. near the center of the scope tube. This means If the core is surrounded by a magnetic field ELECTRIC MOTOR REPAIR, that when an electron is near the end of its (for example that of the earth) the two halves a big, brand -new book by the of the core no longer publishers of famous Ghirardi have the same Radio-Electronic books is a gold O SC peak mine for radio men who want to magnetism since one is expand along logical, profitable strengthened and the lines In an uncrowded field. L2 other weakened during Based on this big book alone, any given half -cycle of you can prompt, tSißJ 9-R. train for - exciting entrent. As a profitable service on practically result, the lag ANY TYPE OF MOTOR IN - hysteresis COMMON USE -from small, is increased in one of fractional horsepower motors in the core "magnets" and home appliances, to the larger is decreased in the industrial motor. It tells exactly other, so there is a dis- how to do everything from tartion of the previous - making simple adjustments and I I 1 ly symmetrical field repairs to complete motor re- 450UACE OF TRIGGERING IMPULSES winding. Covers variation. AC and DC mo- The tors, synchronous motors and C effective electro- . generators and BOTH mechani- magnetic field now has cal and electrical control systems. a component which varies IT PAYS TO SPECIALIZE IN at a frequency "SOMETHING DIFFERENT" twice as great as that of the exciting current. Every step of the work it explained 'Imply as A -R -C. both In Condenser C tunes the text and by moro than 000 specially secondary winding to prepared diagrama and Illustration'. No guoaswork I Earls phone of motor this frequency and the repair Is . clearly sbmen so (hero eon induced voltage is am- be no tniatnkina an to what should be dono and why. Quick reference cubits: show step -by- plified and detected by step' how to handle specific jobs. tt'hen a motor comes in a meter. The deflection for repairs. Just turn to ELECTRIC MOTOR REPAIR anti see what to do. it's an Ideal book, cipher for beginners may be either to the or for day to day bench liso In busy sitoln. right or left depending Unique Duo -Spiral Rinding divides book into two melons with test on one side, pictures on the other. L upon the direction of Lies fiat on the bench. Both text and rotated illuatra- magnetic field being tinns aro visible at the the same Unte. travel (along a horizontal line), one or the measured. The field intensity is shown by the Rood coupon now. PRACTICE from ELEC- other of the magnetio fields will predominate output current magnitude. Note that the plate TRIC MOTOR REPAIR for 5 full days - from the AT OUR RISK. Then, It not more than sat - and cause the beam to be deflected even though potential for the tubes may be obtained felled, return book t^ us d EYF.IIT CENT no signal is coming through. Therefore the tele- same a.c. source that supplies the electromag- ' OF YOUR (IONE1- \í1U, BE GREER- SULLY REFUNDED. No Questions askedi vision picture will be distorted along the two netic primary. sides. In this circuit. each deflection coil is This device may be used as a magnetic com- "BORROW" IT FOR centertapped and each half carries the current pass. The mete, will indicate a peak reading from -one tube. As -a result, the two opposite when the core ie pointed toward magnetic north and equal fields cancel out in each coil. Under and south. 5 FULL DAYS! this condition there is practically no magnetic field due to the d.c. component of the push -pull tubes and therefore no vertical deflection without UNDERWATER DETECTION signal input Patent No. 2,410,065 DEPT. RC -6r, MURRAY RILL BOOKS. INC. 232 Madison Ave., New York 16, N. V. Bertram M. Harrison O Enclosed And $5 ($5.50 outside USA) for my copy of the biénd"neW 1h MOTOR 'M PAIIC (assigned to Submarine Signal Co., Boston) C.O.D.CLECrRI MAGNETIC MEASUREMENT Ise foreign G.O. unsatisfactory Power at. superaudible frequencies is generally for y it understoodder 1 fr [turn Patent No. 2,410,039 used in devices for underwater detection of book ins days for complete refund of my money. Lennox F. Beach objects. A sharp pulse is transmitted (peri- I odically) and is subsequently received as an Name (assigned fo The Purves Corporation, echo. The time interval between the two instants Springfield, Mass.) measures the distance of a target Because of Address Measurements of magnetism are inherently in- the very short time between transmission and I direct and often difficult to make. This electronic reception of a pulse, it is difficult to prevent LCity and Diet. No. State method simplifies the process and is capable of blocking of the receiver. An effective method . (aere rtssl IIA high sensitivity and accuracy. It operates on the has been 'devised in this invention. 54 RADIO -CRAFT for JUNE,. 1947 The figure shows the new method as applied 01.1111.6.. to one type of detector. A shaft rotates at con - stant speed and carries with it a disc and a cam arrangement. The disc is equipped with a thin JUNE Minimum Order $2.00-20% Deposit Re- vertical slot behind which is fixed a neon tube gaged on all orders. Please Add Suf- N. One terminal of the discharge tube is fed ficient Postage. WRITE DEPT. RC -6. through a brush and commutator B and the SPECIALS other is grounded. LEö ad The cam is first adjusted so that it closes the SF7.ENIUM RECTIFIERS -11a1í ave Max. input 50 V. AC (S 1 amp; 25% volt. drop when contacts and actuates the transmitter at the used full - rest. bridge. half orfulln " 3 0.D. Each 09el 4 rfor..$2.45 SERVICEMEN'S KITS Weston #301, 0 -50 voltmeter (modulation) AC reo' # 1 -R.F., Antenna a ose. cogs. 10 asstd $ .98 tiSer, 1000 ohms per volt 3^ bakellte 3.95 $ 2- Speaker Cones: 12 mind.m 4^ tO 12" -edge Wafer Loctal Sockets, 1 3/4" mtg. Each Om 20 for 1.00 molded & free (magnetic incl.) Less voice colis 2.00 Varinble Condensers, 2 gang. 303 mmfd. All with trimmers, 49" shaft. 13/16" long. Cad asimmiMeesine mire plated .75 Precision Resistors, 10f Ire- wound. ohmage : 2.35, 11, 24.5, 100, 3330, 5290. 7800. 30K, 50K. or 400K .35 zs® SAO Fusee. Ray duty cartridge. 1 or 3 amps (8 250V (lilegos"). Either .09: 12 for 1.00 AC -DC NEON TF.ST.LITE. Use as probe or fixed indicator from 90V. up. Each. .15: 8 for 1.00

43- BAKELITE MICA CONDrNSERS: 50 eased. .00001 to 2 mm. 200 -000 WV ALNICO MAGNETS Cearly marked 2.95 ad-TUBULAR BY -PASS CONDENSERS: 50 ell 15810. .001 to .15 m[0. 100600W V. Standard brands 2.49 CO -Dial Scales; 25 amid. irntne & slide /I1 rulo (acetate 4 glass a included) 2.98 07 -sl plate.: airplane AIM fulvlé uyn tpes 2.95 ,1= t8- Knobs: 25 enatd. wood A bakelile, In- eluding puahon A set screw typed 1.00 It 1 -Bar. 81/2"x5/16"3411" . $ .83 It 2 -Face 11/4"x l 4 "xV high .98 09 -Wafer Socket.; 12 asstd. 4 to 7 prongs .25 t3 -Heavy W bar. 2Vte/gl %i6 /18 .98 g10-Voltage Dividers: 10 asstd. standard . It 4 -Face Wert high .39 tapped. High wattages included 1.98 s 5- Polished. °1i9, 10^x5, high .3S *6-Polished bar. 9 /1e-xy "xyg, ....20 for 1.00 &I1- Shield Cans: 15 asstd. for coils. R7 -Pace Va"RW9t4tt! high .10 tube., transformers, etc. 1.00 e S-Ail fI.0 O V, b. shoe. polea 40.1 49" 212-Mica Pn ltpeimA e 1 that the corresponds to zero on the high .75 u ccmiing c bare Instant slot 119-ALNICO hV b' shoe. poles 9/18" a9$ types .59 Scale. Received pulse echoes are applied across ,9B a 10-ALNICO V. Wino* Pales 10146.: # 36' wi Tone controls: the neon tube which is caused to glow during 5.93 wound carbon. Less 10 itches 1.49 e l l shoe, ea. pole 11 /16, O.D.. 2 -Wire -wound Resistors: 15 asstd. ohm- - é V4 015 Such instants. Since transmission.. of a pulse sr 1.29 age.. 5 to 20 watts .98 takes place while the slot is at zero, the echo If 12- (Similar to 5) 4/"x./../.7 /18 .35 Coils: O asstd. including shield # la- (magnetisedvyV bar, # 10-IF will arrive after the slot has moved to some lengthwise. wide or narrow ed A slug tuned. Peaks unmarked 1.95 position. marked aides) 1.29 017 -Dial Windows: 12 asstd. sizes. Incl other If the scale calibration is # 15-Polished Block. 3.3(2./...11,6": MAE flat A moulded acetate and convex off in suitable units of distance, the range of notic[iceded wide Cr narrow sdes (wt. 3 Iba) 2.47 glass 1.29 1.95 an is by 018 -Bakelite Coll Forna: 18 os.W. popu- object indicated directly noting the point. e16-Fla . :Vsle1d5 /16m15/10 thick ;.. lar siz es up to dlamoser .98 groove .49 3 at which the neon tube flashes. 19 25 a t17- Cinvlar, 1 1/16" 0.D..0.D.. 49 hole; semi. # -Ri Resistance Units: std. I Receiver blocking is accomplished by the net- circular polea on flat sides .49 watt. canmrt & wire, ierrulend.e-ch 25 1 t18-ound bar, Vi" O.D., 5/16" long to-5 megohma .49 work La, Lb and C. The reactance of La is 020-SPEAKER KIT. real' money designed to be equal and opposite to that of C. It 19--Round h'shoe. %V O.D., 7 /10 high .12 time saver. 21-Round bar. polished, 0.D.. inch .07 paperpIeeggREPAIR The reactance of Lb and that of the projector *21-Round0 bar, polished. 0.D.._ Ñ lon .35 coli forms.. 3 yds felt strpe t2á0 22 d bar, polished. 0.0.. 1W' Chamois leather segments. are such that only a fraction of the total circuit 1ón8 .39 shims & tube of p eake cement. Allll voltage appears across the inductance. During It 23-Round bar. polished. % O.D., 21/4 for 2.49 .59 #21 -Metal Cased By -Pass Condensers; 10 transmission of a pulse, therefore, only a frac- e 24-Round bar, polished. % O.D., pa per. wound, multi section. tion of the total voltage is the long 41/4°- 1.20 201d.0.400W V .49 present across #25- Rougnd par, pollas.. % O.D.. 5 11/10 receiving amplifier. The amplifier input and Lb 1.49 022 -Resistor Assortment: 10 carbon and 1,20-Round $ Y" long .39 wire- wound, asstd. ohttages, l,3 to 3 are designed to be parallel -resonant at the super - 2 le block, h watts .49 audible frequency being used. Therefore the 023 -RADIO CEMENT -& SOLVENT' KIT voltage is m nt iA 3lvoeanto(thinner)! With appli- entire received effective across the Telegraph Key and OV Sasser (Weston, Electric) brush .69 amplifier. Gap & tension adjust; bakelito base $1.28 cator Telegraph Key only. Adjustable platinum con tact.. Bakelite Base A8 Bendix Am Ilaer (Line of Sight) rotary indicator. MULTI -CHANNEL U.H.F. Os McGuire Pick-up 3 cast metal, brown finish. LOS I ISV, 400 cycle. Contains: power Inns, L.70 type audios, 8 oll condensers plus ther components RECEPTION cartridge .59 worth many times the price. Black enrich( case Patent No. 2,394,917 7 ^x54/"x45 1.95 I I SPECIAL. I ( -GIANT "GRAB -BAG" RADIO Heinz E. Kellmann PARTS KIT. A real buy for the Serviceman. Amateur or Experimenter. 15 FUL1. "OUNC311 INPUT TRANSFORMERS . High -frequency broadcasting (including FM, POUNDS of useful: re iston, densen. 3/16.) 56-Carbon Ike to television, facsimile) has created special prob- us. Dire, ape:er repair Pana 9r,a; 58.0 oprnie mike or low Im- haamazrdwaretransform etc., etc. podenp pick -up to timer.... .49 lems which differ greztly in several ways from va ai, $1.95 grid. I 12 foe 5.00 those of AM broadcasting. For example, the line-of-sight limit makes it desirable to use di- PF.LSYN Control Transformers (í2J10^). Original. Iv 1101/.400 cycle, will operate on 50V. 00 Frequency Manual rectional antenna systems, AL-o an accurate cycles 1.95 Operation; 39 illuusI. digrams; 58 pp. n. ..S .19 impedance match should be made throughout, 30I,cycl SUiyynn VII) RADIO HARDWARE TREASURE. An indispensable wave 0 cycle. dro Inrspairs na trans. ß Sfollower. assortment of approx. 1000 screws. nuts. since reflections often seriously distort a 31,.k. S1Á". ea. 3.75 .49 received Victor rower Transformer for models R-32. 45. picture. The wide modulation bands re- 2^ Meter Frame Complete with s2 or 75. Unehlelaod 5.95 quire special design in the antenna and receiv- glass A a screw.4Housind(round). deep 39 ALUMINUM PANELS (.051.1: 7"X10" .39 Weston #301 meter glass & trame: adjust 7" x12 -.451 7.714,-.49: 7ryr18 .59 ing units, and limit the number of available screw .89 BAKELITE PANELS: Vs glossy brown. 7"z30 .59 channels. r7xPERTMLNTAL TUBES .20 asstd. receiving 7"x14 "-.59; 79[18 --79: 0x14- .as 1Áí" Linen Bakelite Strips, 11x11 / ". 3 face .25 This patent proposes to ose separate antenna types for tasting. research. etc. Filament tested.. 1.00 Acre- Snap Momentary Switch SPDT, needle plunger (2 os. pressure) 1OA /125V. Bakelite systems for each station within range, thus ease .39 making TUBES: Perfect condition. but not in scaled it possible to tune, orient. and match a. Gran.eed.. for 90 days. each SSO. 27 50 -.29e; 542. 45. 75, 77, 7A. for optimum picture or sound reception. 1 I PHONO MOTORS I 1Twlneoll 110V. The various ,outputs 80, 89, 6Y3. OHO or GK7 .39 A.C. quiet rim -drive. fan cooled. With feed a single transmission #0A8. 005. OIS, 0J7. 65K7 or 35/51 .43 9 turntable 2.95 line designed for low loes at ultra -high fre- #1A7, BAs, 005 /OU5 or 50 .59 quencies. Fixed -tuned receivers then may be Bend new R.C.A. UX -200 tubes in sealed ear. DYNAMOTORS (Navy DY.9) DC Inputt 26V: DC connected across the line where desired. In some tons. Ideal triode detector-8 for 1.00 öá k énlenlah Mtntts baseulç 61/2831/.... 3.95 eases. it may be desirable to convert the original i ckçVIih high frequency to a lower carrier frequency SPEAKER GRILLES. S1/2- olé. Flocked musical PROMPT or even to demodulate before feeding de line. design on gilt perforated tal .19 S SERVICE ON ALL thus simplifying Speaker Grillele Decorative gold or sliver SPEAKER AND PHONO PICK- the apparatus necessary to weave. Per sq. .20 . UP REPAIRS reproduce the signal from the line. Cone Centering Shims. Kit of 10 (4 thicknesses) This invention should be especially applicable ln durable leather case .35 to large apartment buildings and hotels. HEADPHONES (Army HS 33) 2000 ohms. Leather c e cd adjustable. With PL -54 ROTA-BASE Sponge bber phone cushions. Per pair .20 NEW HANDY LAB. DIAL actually give. a g 515.18 2000 ohm Phones picture of radio tube connections. Simply tin, th (2 -R14 receivers) with 13 RADIO CO. dial to the tube n ber desired on the ROTA -BASE. double cord & PL -54 and mplete correct connections are instantlyl 1ndi. MAKERS OF CONES ANO FIELD COILS nerd ce the "prong" diagrann. No re valuable HEADBANDS (HB -1) with time lost thumbing pages on lengthy dings. DEY STREET. NEW YORK 7. Filament, grid, 65 -67 N.Y: piate. cathode. etc.. to MORE THAN PLSA plug b 13- tipped 300 tubo types given. PRICE NOW ONLY $1.00 double phonC r1 19 WORTH 2. 0284.5 postpaid or sent C.O.D. plus postage. Order NOW. J R -26 ext. jack for M.sa. refunded If you aro not delightfully pleased. Bakelite shell .23 12,000 SO. FT. OF RADIO PARTS- REED M FG. Co.t; ¡p

RADIO -CRAFT for JUNE, I 9 4 7 55 COLOR TELEVISION (Continued from page 40) CODE CARD SYSTEM ENLARGED COLOR IMAGE ON SCREEN Removable Self -Starter Strip exposes ends of Labels for you to peel!

DON'T PICK. USE SELF -STARTER STRIP TO PEEL LABELS.

DON'T PICK. USE SELF- STARTER STRIP TO PEEL LABELS. APPLY IDENTIFY

12 REVOLVING COLOR FILTERS, 720 RPM LIKEWISE OHF[ATSUAFAC{S

à1m p ® pw gpir ,r,.giffiZZ,J747, b l ris 'patunts rnding QUIK- LABELS code WI h, Leads, Circuits, Relays, Parts, etc., faster and cheaper. Pre -cut to exact size, QUIK- LABELS come on handy cards. Ready to use, they etik -ouik without moistening, replace slow and costly string tags, roll tapes. decals, stencils, metal tabs, etc. Resist dirt, grease, oil, abrasion. Self Starter Strip automatically exposes ends of Labels for you to grasp instantly-no more finger -picking.. W. H. BRADY COMPANY Established 19U Manufacturers of Self -Sticking Tape Products 802 N. 3rd STREET. MILWAUKEE 3, WISCONSIN I'm Interested. Send me all the facts on QUIK- LADELS. Name Title Fig. 5- Sequential ,color receiver, showing how color is restored. PLEASE ATTACH TO YOUR COMPANY LETTERHEAD of each tube, as Fig. 1 -b and Photo E - e show. The 3 color beams are flashed onto ARMY -NAVY a mirror, which reflects and blends them HEAD PHONES RADIO KITS«. ARE TOPS on a translucent screen. The observer FOR FUN AND ACCOMPLISHMENT I sees a single composite color image or Build this porta- picture on the screen, the size of the $249 radio. Model ble 15 20 210 ... a three - image being x inches. The receiver way portable re- is of the projection type and is not ceiver, operating on either AC or adapted to direct viewing, at least in its DC or self -con- present design. About 45 tubes are used tained batteries - re" buoi power switch con- in the receiver; this includes sound. 34. mode S. S'9nes. U bo veniently located In the tests conducted at Princeton, Gena, ne 8000 on front of sat so Cores bea"Lvé. bk. or N. J., for the FCC, color images were sensa ntsca that "Battery" bightÿ LmPed OQ "AC-DC" may be transmitted by radio for a distance of oblor Ptuschgs.20' selected without mo9ir 5 permanent about ifs mile, using a frequency of 0° Po kg opening case. Five -Inch Alnico Sq. d9 ° and P 5\3 magnet dynamic speaker, and case covered 520 mc. e ' with weather-tested aircraft material. Accom- R00'13'eto iLn Ñói7A97 panied by simple, detailed instruction sheet. For comparison it is interesting to Oder Price 516.95 note that the RCA console receiver for GET THIS Available at your local distributor. B & 10 If not, write to us. W reception, with a -inch tube catalog, lofes devel for direct viewing, 30 The opments in rodio and Many other models available. has tubes. electronic ports and de- Write for Catalog M B & W projection receiver for an image vices, newest ham gear, 15 x 20 inches has 45 tubes. gadgets and bargains. ... m - a RADIO KITS COMPANY One of the advantages of the simul- N. Y. 1 BURSTEINAPPLEBEE CO., 120 Ceder Street, New York 6, taneous color system is that a standard 1012 McGee Sc,, Kansos City 6, Mo. black and white receiver can be fitted ._.--- Send me your new FREE catalog. with a nominally priced frequency con- Send me pairs of phones at verter so that B & W images may be -2 52.49 plus 20c pair postage. I enclose SPECIAL BUYS! WESTINGHOUSE & G.E. picked up from a color broadcast. The S-._ _ -in payment. RC DYNAMOTORS B & D -input 27 V Ccd 1.4 converter permits the receiver to pick I NAME amps, output 265 V ® .06 amps or same up the green carrier, and as this con- input with 260 V output at .07 $1.35 I ADDRESS amps- Special. ea tains all the essential picture character- ScIsyn differential motor 115 V 60 er. mn be used istics and the synchronizing signals, a I TOWN STATE as high speed motors spprox 1/70 hp with slight Ir__ -GM r_NM esnvoreim (conversion data sheet sup- $1.75 satisfactory B & W picture can be re- - plied). ea. produced on the receiver. This prevents 100 Assorted Resistors, including eight $1,75 2 W resistors obsolescence of B & W television receiv- POWDERED IRON CORES 50 Assorted Mica Condensers $1.95 ers purchased in the past few years. The Make your own high "Q" I.F.-R.F. or B & W receiver cannot pick up its images Antenna coils! Range 100 kc to 50 me. .1 -.1 rot 7000 V.D.C. GE pyranol. ea. $1.95 KIT No. 1 -18 Pieces, 8 Types.....i2.00 pp Five air trimmer ceramic lesl, Assorted in color, of course. To do -that a color Values receiver must be used. A 'sequential re- Also, perm, tuning cores -1700 kc to 635 kc Minimum order $3.00 FOB Philadelphia KIT No. 2 -12 Pieces, 8 Types 53.25 pp ceiver must be of the dual type, fitted MAGNA -METAL PRODUCTS CO. Reliance Merchandizing Company with changeover switches, to pick up 70 E. 45th St. New York 17. N. Y. Areh at Crasher Street Philadelphia 3, Pa. (Continued on page 59)

56 RADIO -CRAFT for JUNE, I947 TELEVISION FOR TODAY (Continued from page 37) r-MONEY TALKS! DOUGLAS OFFERS causes this separation of ions and elec trons is obtained from a small coil The Lowest of Low Prices on the Map! AMPLIFIER KIT! Complete with tubes and punched without nose. Models 102 -103 Complete. placed on the outside of the neck of the chassis for use on phonograph or mike. List $11.00. Yours for $5.53 tube, above the cathode. The 10AP4 tube Special $10.43 F.M. AND TELEVISION ANTENNAS from $4.75 up PHONOGRAPH KIT! Complets with all parts Motor. Deluxe Meter Cases for 2 -3/16 or 2-13/16 Mir. is a commercial tube which employs this turntable, pickup and cabinet for use with above Special $1.15 amplifier. Special $10.95 Chassis 5 x 0% x l'í -20 gauge steel block finish 53e type of ion trap. SPEAKER KIT! Complote with 5" "alnico' speaker Other sizes available at discount prices Yet another method and cabinet. . Special $4.58 'NE -O -LITE ew electric trouble shooters-can be of practically MICROPHONE KIT! Complete with stand and cable used on 60 volts AC to 500 Volts AC or DC. eliminating the ions is the type of elec- for use with amplifier. Special $5.58 List Soc. Yours for 255 PLASTIC PLIERS-5000 Volt Breakdown-Deal for tron gun shown in Fig. 9. The electrons METERS AT SPECIAL PRICES rt POWER TRANSFORMER 700 Volts C.T. 70 ma and ions, when emitted from the cath- Marlon 3" 0 -1 ma. 0-500 us, 0 -30 ma. 5 ma, 50 ma- chola of any- Your special price $2.50 5 Noll, and 2 2.5 Taps. Lists for $6.60. Yours for $3.30 ode, tend to spread out. If a strong Marion 4" 0 -200 ua I mill, 500 ua, 1 nia . 0 -200 0-500 ma, 0- 30.9LOic0 of any, your special price $3.75 AC DC CHOKE 9.5 henries 50 ma 200 ohms. Lists magnetic field is applied at this point, for $1.95. Yours for 74e BEST BUT IN RECORD CHANGERS FILTER CHOKE 9.8 .henries, 100 ma 275 ohms. the electrons can be made to converge List $3.05. 1 ours for $1.50 Doten!a Modol 550-changes 12-10' or 10 -12" records NEW G.E. RELUCTANCE PICKUP CARTRIDGE. and pass through an extremely small tomatlauy. Spatial $13.95 $4.56 aperture and into the main focusing and I.R.C. RESISTOR ASSORTMENT -100 Popular - ALLIANCE PHONO MOTOR AND ASTATC Sian- $1.95 PICKUP" KIT. Special $4.95 deflection fields. Again, the heavier ions SPECIAL 34 Meg Volume Control and Switch Special 49e 5" Alnla F.M. Speaker $1.75 CATHODE RAY TUBES 5 DPI Sylvania $4.95 Variable Condensers for Suporhet Special $1.10 VERTROD NOISE REDUCING ANTENNA for corn- Variable Condensers for T.R.F. - Special $1.25 muniations. broadcast and short wave receivers Special C.D. 2 mfd 600. V an type 39e HARI) TO 'GET SEND US ORDER I TUBES WEM WILL SURPRISESE YOU H. PROMPT DELIVERN DISCOUNT SD if it's hard to get -we have it!! 25% Dep. on C.O.D. Send for Free Catalog BA 7 -3956 Add postage under $5.00 DOUGLAS RADIO SUPPLY CO. DEPT. A. 128 GREENWICH STREET NEW YORK, N. Y.

selling DISTRIBUTORS enjoy them because they make friends and build business. The VERI- the IFIED GUARANTEE back of 10B Pe him to im- Fig. 9 -A method of eliminating the on spot. distributor enables defective do not react to the magnetic concen- mediately replace any trating field but continue to diverge un- new one ... til they reach a positively charged elec- speaker with a trode and are conducted back to the time and money for the cathode. Those ions which leave the saving cathode in a straight line do pass RADIO SERVICE MAN. through the small aperture and into the electron beam. However, the percentage of them is extremely small and no visible damage is caused. A. tube with this type of gun is used in the latest RCA television receivers. The proper position of the bending GRAPHITE coils for the ion trap is at the end of the DEM. COILS COATING tube neck close to the tube base. In H V adjusting the set, the coils are moved uatil the scanning raster or image is brightest. The coil clamps are then tightened securely. GRID FOCUS COIL A third method of preventing ions 41111k .....,,v from reaching the screen is accom- NEATER plished by -the aluminum layer men- tiened previously. The ion, with its Le Igr. ,,ff...... ,,1114, ,fre: BENDING COI . greater mass, does not penetrate as deeply into the aluminum screen as does the electron. By properly determining the thickness of-the metal screen, ions are excluded, while the electrons in the beam are able to pass through. This article closes the series. Comment from Fig. 8- Cathode -ray tube using e bent electron gun readers. Or suggestions as to other subjects for and magnetic field to eliminate on spotting of tube face. 44500 V similar treatment, is invited. TO ANODE

RADIO -CRAFT for JUNE, 19.47 57 CAN YOU ANSWER THESE? Employees of Collins Radio Co., Cedar Rapids, Iowa, are expected to pass a technical examination to show their knowledge of the work they are to per- form. A passing grade entitles the ap- plicant to a trial period on the job which, if successfully completed, leads to a permanent assignment. The following are sample questions taken from an examination for a "Test Technician B" position. 1. In a radio frequency amplifier stage having a plate voltage of 1,250 volts, a plate current of 150 milliamperes, a grid current of 15 milliamperes, and a grid leak resistance of 4,000 ohms, what is the exact operating grid bias value? 2. Sketch a block diagram of a crystal- controlled transmitter, using a buffer stage and high -level modulation. 3. Why is the distributed capacity of a coil always increased by the wax or other coating used for protection against moisture?

4. How is . the vacuum -tube plate current of an r.f. amplifier affected as the plate- circuit resonant frequency is varied?

Two more titles in this popular new series are now available. The two latest -described below -like the others, 5. The above is a circuit of an r.f. give you the most recent, reliable technical information and are as modern amplifier. What is the fundamental dif- in appearance as 1947 radios and cars. ference between the action of the meter The type is fresh, clear -cut, easy to read. The books are bound in flexible covers, if the tube is operating Class C from smartly designed. In short,`everything what it would be if the tube was oper- each connected with these volumes is up-to- 5O the-minute and practical to the nth de- ating Class A? gree. You'll find them constructive helps volt- Titles in building up your knowledge of radio. 6. What are the principal output Nine Recent age ripple frequencies in a full -wave KINKS RADIO QUESTIONS CUTS NO. 31. rectifier? AND DSHORT AND ANSWERS 29 7. What is the relation between the PATENTED Here are the answers to questions most UNUSUAL 1944 -1946 Box" -current power input of the plate 3O CIRCUITS frequently asked of the "Question direct z editor of RADIO -CRAFT. The matefial circuit of the stage being modulated, RADIO QUESTIONS selected is well diversified and chosen for AND ANSWERS practical application to workaday prob- and the output audio power of the 31 SERVICE lems. Circuit diagrams are supplied with modulator for 100 percent sinusoidal ^ ADVANCED the answers. }+ TECHNIQUE modulation? AMATEUR RADIO AMPLIFIER GUIDE NO. 35. 8. Sketch a block diagram of a super- 33-+ BUILDER 'S BUILDER'S GUIDE heterodyne receiver showing an audio AMATEUR A 'book for the amateur operator who frequency stage, radio frequency stage, BUILDER'SRGUIDE builds his own. Practical and down-to- r how to build trans- stage, speaker, 35 TEST earth, it tells you audio power amplifier RADIO mitters. receivers, and other ham gear. mixer, second detector, and intermediate .,. V INSTRUMENTS Construction data on a 430 -mc transmitter, an 53K -24G c.w. transmitter, a frequency stage. SERVICING miniature communications receiver. an 3? RADIO acorn-tube preamplifier, and many others. 9. What is the sum of 25 cycles, 25 HOW TO BUILD Whether you're an amateur now, or just kilocycles, and 25 megacycles? RECEIVERS studying for your ticket, you'll want t 38 RADIO this book. 10. What is a "parasitic oscillation "? SEE YOUR DEALER Collins Signal, Jan., 1947 IF HE CAN'T SUPPLY YOU, USE COUPON -The (Answers for these questions next month, if in RADCRAFT PUBLICATIONS, Dept- 67 you need 'em! Write and ask.) 25 West Broadway, New York 7, N. Y. ( ) ALL NINE Send me the volumes We each, postpaid) checked. My dealer is unable BOOKS to supply. this New RADIO RULE! 29 O 35 Get I enclose S Nreded by all OA) 30 .,a,41, 04aq, drfsmnate° n d Your Name 36 . teehniciaann s. Clearly) ag This (Print Q 31 I .7 ya symbol you Address 37 t868tg4 syuwet,4v time and loon. O 92 1=4 11ó191g1\ ev Sent Imme- Dealer's Name 33 38 COLETTE PRODUCTS CO éá vloi á:oó: Theatre Bldg., Dept. A, Detroit 1 TODAY Address .113 Fox

' for JUNE, 1947 58 RADIO -CRAFT COLOR TELEVISION (Continued from page 56) A. A. Ghirardi black and white images as well as color pictures. Sintultanoous-type color receivers can POSITIVELY _pick up and reproduce images broadcast y B & W stations, with the aid of an adapter. The adapter is needed only because the color band is at a higher GUARANTEES frequency than is covered by B & W receivers, and would be needed to receive B & W transmissions on those fre- to help you repair any radio ever made EASIER BETTER & 1A3-1U or refund every centof our money!

TO HELP YOU LEARN TO HELP YOU REPAIR 9 s Professional RADIO - OUT OF 10 RADIO TROU % Np ELECTRONIC REPAIR, BLES Twice as Fast, without J` l!1t at home, without costly test equipment jt h"' an instructor t i

THE ONLY COMPLETE, 1 VOL. ELIMINATES NEEDLESS TESTING! COURSE OF ITS KIND! There's no magic about it! Just common sense! Once in a lifetime, a technical book is Over 400 pages of Ghirardi's 744 -page RADIO written that is so important, so complete TROUBLESHOOTER'S HANDBOOK contain and easy to understand that it is used al- tabulated and indexed listings of common trouble most universally by members of an en- symptoms, their causes and remedies for almost Photo E -A simultaneous television receiver. tire profession -and Gnirardi'a MODERN every radio in use. RADIO SERVICING is exactly thin kind of Actually it gives specific a book. It gives a course in radio-electronic trouble listings for over 4800 home receivers, repair work by approved scientific methods. auto radio and record changer models of 202 quencies. At the present development Included is a thorough explanation of Test manufacturers! Just look up a defective radio's stage, a mechanical or sequential color Instruments, how they should be used and make and model. The HANDBOOK tells exactly why -even how ; receiver cannot pick up a simultaneous to build your own Receiver what the trouble is likely to be-exactly how to Troubleshooting Procedure and Circuit Anal- fix it. 9 out of 10 jobs can be handled by this image, either in color or as a black and ysis; Testing and Repair of All Compo- method t,¢ nents; Installations; Adjustments, etc.. etc. -in the usual time BECAUSE white monochrome. TEDIOUS TESTING IS ELIMINATED. Over 300 more -also How to Start and Operate a Success- pages ful Radio -Electronic-Service Business. 1300 contain service hints, alignm_nt data, tube in. Among some of the advantages formation, graphs, diagrams and charts to help you pages. 706 helpful illustrations. Self-Test fix ANY RADIO claimed for the simultaneous color sys- Review Questions make study easy. Only $6 EVER MADE in far less time and at foreign). greater profit) Only $5 commle e ($5.50 foreign). 5- tem are: narrower band width than that ($5.50 DAY MONEY -BACK GUARANTEE. . . NO PREVIOUS EXPERIENCE required for sequential transmission; FOR BEGINNERS! NEEDED I greater freedom from flicker; no color Sales records prove that more Radio-Elec- fringing and no color breakup; greater tronic beginners have gotten their start fidelity in picture detail and superior from Ghirardi's 972 -page RADIO PHYSICS COURSE than from any other book or picture brightness for comparable size course ever published. It's a complete rad:o GUARANTEED v ° of images; superior flexibility for net- course in book form -so head and shoulder, TO HELP YOU LEARN R P.¡515í above anything else that it is used as the work broadcasts. basic text by thousands of students and by COMPLETE BASIC Prdßd schools in 82 different countries of the G' The second part of Mr. Secor's article -to ap- world I Everything is explained as simply RADIO -ELECTRONICS,;''. : pear in an early issue -will describe three other as A -B-C. Over 300 pages are devoted to proposed methods of color television. Basic Electricity alone. 508 illustrations . , . for beginners! help you learn fast. $6 ($6.50 foreign).

COMMERCIAL PARADISE

Commercial announcements on the DEPT. RC -67, MURRAY HILL BOOKS. INC. Brazilian ether are so frequent and 232 Madison Ave., New York 16. N. Y. lengthy as toacause one American broad- C rndoeod find 8 for books checked: or send cap. (no foreign C.O.D.'s) for this amount plus postage. It is under- casting magazine editor to evolve a stood I 'nay return books for refund within 5 days if not fully theory that the Brazilians must like satislled. RADIO TROUBLESHOOT- I MODERN RADIO SERVIC- 'em. As many as 20 spot commercials ER'S HANDBOOK $5 ($5.50 ING 55 ($5.50 foreign) may be broadcast successively, with no foreign) MONEY- SAVING COMBINATION OFFER; Both of the above I program material. - Let Ghirardi's TROUBLE- big books, only $9.50 for the two (510.50 foreign). SHOOTER'S HANDBOOK save RADIO PHYSICS COURSE $5 ($5.50 foreign). Proof that the people like this type you time on common radio serv- of fare is entirely lacking, and the fact ice jobs! Let his MODERN Name that there is only one radio for RADIO SERVICING train you every for complete, professional elec- Address 60 inhabitants of the cpuntry might be tronic work. Get BOTH BIG I adduced as evidence to the contrary. BOOKS at special price of only City 4 Zone Btate $9.50 for the two. Bee coupon. ------a RADIO -CRAFT for JUNE, 1947 59 HIGHBRIDGE'S BEST BUY LIST NEW D YNA MIC WORLD -WIDE STATION

TELEVISION KIT Edited by ELMER R. FULLER

. CONDITIONS here have not been and schedules. These will be available to very good. The same seems to be you in the next issue. Our new 24 -hour a true all over, as very few stations clock system seems to have been well of note were reported by our ob- received by our readers according to servers this past month. This year the letters received recently. We are marks the beginning of the twenty-first glad that you like it and hope to see year of broadcasting of the "Happy it used throughout the shortwave spec- Station" known to many listeners as trum in the near future. It certainly PCJ. It is located in Hilversum, Nether- saves a lot of confusion. R.,- '. lands, with the programs under the di- Some new equipment has been put rection of Edward Startz who is well into service here and we have a report known to many of you. Transmissions ready for you in an early issue. A are directed toward the United States Panadaptor (manufactured by Pano- and Canada on Sundays and Wednes- ramic Radio Corp.) is being used for COMPLETE $ 50 days from 2130 to 2300 hours EST. Fre- visual reception, and our report on it quencies used are 11.730 mes, 9.59 incs, With Tubes-Parts -Cabinet 159 will give you full dope on its operation and 6.02 mcs. Other transmissions are and usefulness to the shortwave listener. Exclusive Mail Distributors heard on Sundays at 1030 to 1200 hours Your shortwave editor would like to Cheek These Outstanding Features: on 17.77 mcs, 15.22 mcs, and 6.02 mcs; correspond with anyone using a Pan - Three amges of video I.F. amplifeat1o, -3.5 MC 1600 to 1730 hours on 11.73 bandwidth. and from adaptor in conjunction with their re- Receiver may be aligned easily without use of mcs, 9.59 mes, and 6.02 mcs. Transmis- signal generator. ceiver. To those of you who have written ' Complete resistance and voltage analysis chart for sions on Tuesdays are from 0300 to we easy trouble shooting supplied with each kit. about the shortwave dope card, will transformers are slug tuned for high gain and 0430 hours on 17.77 mcs, 15.22 mcs, and If have more on this matter in a , few maximum efficiency. 6.02 and on Wednesdays from 1030 Safety interlock switch supplied with each unit. mcs; weeks, possibly by the time that you Simplicity of operation -only 6 controls on front to 1200 hours -on 17.77 mcs, 15.22 mcs, panel. read this. Information will be sent to Schematic diagrams are broken down into simple and 6:02 mcs; from 1600 to 1730 hours circuits for case in wiring. you soon. Picture is very stable -does not Jump or tear out on 11.73 mes, 9.59 mcs, and 6.02 mcs. even under unusual receiving conditions. Many changes have been made re -' (AU schedules are on Eastern Stand- 4 Channels -provisions for wiz. Seventeen tubes Including largo picture tubo. cently in the U. S. stations' frequencies ard Time) Picture tubo is seven inches in diameter and gives picture 26 square Indies in size. All parts are unconditionally guaranteed to be electrically and mechanically perfect. Location Station Free. Schedule Locbtlon Station Freq. Schedule Bet comes complete with all necessary Information Meets. parts. drilled and punched chassis. beautifully finished front panel and modernistic cabinet. FINLAND Delhi VUD7 6.100 0830 to 0915 Hardware and other necessary items are also in- Lahitl 01X2 9.500 1100 to 1600 Delhi VUD8 7.270 0600 to 0700; 1115 to cluded NOTHING ELSE TO BUY. Lahitl 01X5 17.800 0130 to 0200; 0500 to 1315; 1830 to 1915: 0545; 0800 to 1700 2100 to 2200 SONAR SOUND DETECTION UNIT FRANCE 11.840 0000 to 0045; 0100 to. Delhi VUD3 7.200 2040 to 2245 Paris 0145; 0545 to 0615: Deihl VUD4 9.590 0030 to 0100; 0200 to In Original Overseas Packing 1045 to 1130: 1315 to 0400; 0430 to 0515: sounds within an 1730: 1830 to 2345 0000 to 1r0 Ideal for detecting underwater 0000 to 0130: 0200 to a Rochelle salt stai as the Paris 15.350 0700 to 0000 Delhi VUD4 9.670 area of 15 miles. Using 0400; 0430 0515 Is up a 60 ft. Paris 17.760 0700 to 0900; 1100 to to active unit the sound transmitted 0780 to 0795; 0800 t0 enclosed in a solid rubber sheath. 1230 cable. Completely 0845 to 1230 Originally used In harbor defense. Coupled with FRENCH EQUA 0830: many valuable TORIAL AFRICA Delhi VUD3 15.290 0130 to 0145; 0200 to 'audio amplifier It has $9.95 0400; 0445 to 0815; uses. Brazzaville FZI 6.020 1600 to 1845: 0000 to 0130 2245 to 0030 SELECTRON SELENIUM RECTIFIERS Brazzaville FZI 9.440 0000 to 0130; 1100 to Delhi VU DIO 17.830 0900 to 0430; 0945 to 2020 0700 Brazzaville FZI 11.970 0995 to 0300; 0930 to IRAN 50 to 99 .85 I 1030: 1100 to 2020: Teheran EQB 6.150 1000 to 1415; 2230 to 0000 to 0230 2900 6 to 49 .90 .? e Brazzaville FZI 1.5.500 0441 to 0800; 0930 to Teheran EQC 0.680 1200 to 1430 1030 JAMAICA to 0130; 0495 to I to 5 .99 Brazzaville FZI 17.530. 0000 Kingston ZQI 4.700 1680 to 1830 0745; 1100 to 1700 JAPAN Quotations on larger quantities FRENCH WEST Tokyo 8.075 0400 to 0900 furnished upon raque t AFRICA Tokyo JVT 6.750 USEFUL FOR: * AC.DC Portal: es * Intercom Dakar FGY 7.210 Tokyo 1VW 7.260 Hone Semite, 8 pm to Power Supplies * Console Rados * Replaces 29 GERMANY 8:30 am Types of Rect. Tubes Berlin 6.070 0000 to 0345 Tokyo MG 7.280 Home Benito, 02D0 to Munich DTYC 5.300 0900 to 0930 KS- 0529 -Transformer Psi. 115 V-60 cycles. Sec. Munich AFN 8.560 0400 to 1209 Tokyo JLG2 9.510 0300 to 0830 ;1-450 V @ 30 NIA C.T.. Sec. V2-6.4 V. @ GOLD COAST Tokyo 11.112 9.520 0600 to 1200 1230MA. Rectangular metal case. stud mtg. solder Accra Z0Y 7.290 1045 to 1800 Tokyo 111( 15.160 1730 to 1815 v eyes- approx size 3 1/16 x 2 5/16 z 8% with standoff GREECE Tokyo 1TL3 15.220 1800 to 0230 4%. Athens 7.290 14f:0 to 1530 KENYA No. T2G-97. Special $1.95 Athens SVM 9.030 1300 to 1800 Nairobi V Q7L0 4.030 1100 to 1400 GUADALOUPE Nairobi VQ7L0 10.730 0500 Co 0600: 0830 to 1.B. v7313 Filament Trans. 115 V -50 -60 cycle. Point-a. 0915; 0945 to 1100 Sec, 31 -27.ÁV @ 4.3 amps No. CT. :-Sec. V2- Pitre FG8AH 5.990 1700 to 1900 0900 to 1200 5.1 V. @ 3 atop CT. :-See. ít8 -64 V. @ 3 amp 7.640 9.890 2300 to 0100: 0530 to No. C.T.: -Sec. #4 5.1 V. o 8 amp C.T.: -Scc. A5 GUAM KU5Q -2.6 V. 0 3.5 snips No. CT. Itectangular metal 0700; 1100 to 1330; : 1900 to 1545 case, solder post terminals: )ltd on porcelain stand - Ms: stud mtg. size 5% x 9% x 5% with standoffs 6'A. GUATEMALA Guatemala 6.530 0800 to 1200; 1830 to T2E -88. Special $4.95 Cay TGWB 0100 Guatemala NEW No. 631P1 /SNA Glass Strobotron tubes. City TG2 6.620 1800 to 2300 Each 83.25 Guatemala 100 lty -Pass Condensers. 10 Varieties. Special -54.95 City TGWA 15.170 1200 to 2000 HAITI Ifigh voltage transformer with Glass Standoff Pri. Port-eu- 6.950 0600 to 0815; 1100 to 115 V. A.C.-400 cycle -Sec. 13.500 V. Rectangular: Prince HH2S 1300; 1730 to 2130 norox. size 6'6 x 41i x 3% with standoff 7W-13 Porteu- 6.160 0500 to 0830; 1100 to Mills U.r. Prince HHCM 1400: 1700 to 2143 T3F -7. Special $3.95 HAWAII Honolulu KRHO 9.650 0400 to 1100 TUBE Honolulu KRHO 17.800 Philippine beam, 0400 12A6 .83 1%N7 .79 to 1130 6SQ7 .83 6517 .83 HONDURAS 6A15 1.25 6C4 .79 La Ceiba HRD2 6.230 1200 to 1400: 1900 to 1625 .70 645PI 5 95 2300 San Pedro 6.860 1100 to 1415; 1800 to 2255 All Prices FOB New York City, N. Y. Sula Tegucigalpa HRNI 6.870 0800 to 1000; 1800 to WV/ - HIGHBRIDGE RADIO - TELEVISION 1500: 1800 to 2300 Suggested by ICELAND Frank Braver. & APPLIANCE CO. Reykjavik TF1 12.260 Sundays. 0900 to 0030 343 CANAL NEW YORK 13. NEW YORK INDIA - Don't Touch That Dial!" Delhi VUD3 3.340 1200 to 1245 "Ah, Ah, JUNE 19 4.7 60 RADIO -CRAFT' for Location Station Freq. Schedule LEBANON Beirut FXE 8.030 0015 to 0115; 0525 lo 0630; 1000 to 1600 LUXEMBOURG 6.090 1430 to 1700 MALAYA 2s Singapore 4.780 1730 to 2230; 2330 to Mwsiccd 01241 WITH Singapore 6.770 0345 to 0935 Singapore 7.220 2930 to 0130 Singapore 9.550 0315 to 0515; 0580 to A8SOLUTE FIDELITY 1100 MARTINIQUE Ft de Franca 9.700 0900 fo 1245; 1600 to AMPLIFICATION 1610; 1790 to 2030 DESIGNED By A. G. SNANEY MEXICO Guadalajara XE111 4.820 2200 to 2400 Mexico City XEUW 6.020 0700 to 0100 Mexico City XEUZ 6.130 1500 to 0030 A new amplifier development now Mexico City XEWW 9.500 0800 to 0200 Mexico City XETT 9.550 0700 to 0100 dearly identify all the instruments in a íùI Mexico City XEYU 9.600 Shed unknown Mexico City XEQQ 9.680 0700 to 0045 Mexico City XETW 6.040 0795 to 0045 After 20 years of audio research and development, MOROCCO Rabat CNRS 9.080 0100 to 0330: 1300 to can now place in your hands a new means to make the 1700 MOZAMBIQUE most fascinating, uplifting, and enjoyable journey into Lourenco 4.920 Daily. 1330 to 1600- sound reproduction through the - Marques CR780 Sundays, 1000 to 1400 the realm of perfect - NETHERLANDS musical amplifier the Hilversum PCl 6.020 0300 to 0430; 1030 to medium of the most satisfying 1200; 1600 to 1730; . - . 2130 to 2300 world has ever known. . H Ilverwm 9.69 2180 to 2300; 1600 to 1780: If you are one of those discriminating persons for M Ilversum 11.73 1800 to 1730; 2130 to 2300; whom anything less than the best is a dissappoint- H Ilvernum 15.22 0300 to 0430: 1030 to 1200 ment, you are one for whom the ACA -100DC Amplifier H I I vereum 17.77 0300 to 0430; 1080 to 1200; 2130 to 2300 was designed. Send for literature. NETHERLAND INDIES Bandana 4.790 0730 to 0800 Bandana PMA 6.780 eked unknown Batavia PMC 18.135 2330 to 0930 AMPLIFIER CORP. of AMERICA NEW CALEDONIA Noumea FK8AA 6.200 0200 to 0400: 1900 to 398 BROADWAY, NEW YORK 13, N. Y. 2000 Send 3c stamp for A. C. Shaney's new booklet "20 STEPS TO PERFECT AMPLIFICATION" NEWFOUNDLAND St. lohne VONH 5.970 0900 to 1400; 1000 to A. C. SHANEY'S FM -AM AMPLIFIER MANUAL IS STILL AVAILABLE AT 25c 2200 NEW ZEALAND Wellington ZLT7 6.710 0415 to 0450 NICARAGUA 3 OF THE Managua YNDS 6.760 0800 to 1000; 1700 to and 2330 WALSCO STAPLE Managua YNOW 6.850 0800 to 2400 Managua YNOW 6.910 sehedulo unknown NIUMBBERS2 DRIVER NOVA SCOTIA hE Parade) Halifax CH N X 6.130 0700 to 2300 L.LEWLo Pays for itself on Sydney CJCX 6.010 0530 to 2200 PALESTINE the first job Jerusalem JCKW 7.220 2330 to 0130 THE NEW, COLORFUL A sensational fool PANAMA for installing wires Colon HP5K 6.000 0700 to 1300; 1900 to EASY TO APPLY and cables, thof 2300 and Panama City HP513 6.030 1800 to 2300 saves time Panama City HP5H 6.120 0100 to 2300 FELT money. Panama City HP5A 11.700 0700 to 2300 Used by Radio, Panama City HP5G 11.780 0745 to 1000; 1200 to Public address and 2230 FLOCK Intercom Techni- PERU L ima OAX4Z 5.890 1630 to 2330 cians. Lime OAX4V 5.910 1800 to 2400 FINISH Staples into corners L ima OAXIB 5.530 - 1800 to 2330 and other inacess- POLAND ible places. Warsaw 6.100 1330 to 2100 COMPLETE FELT FLOCK SPRAY OUTFIT Staples on hard PORTUGAL such as Lisbon CS2WD 6.150 1430 to 1000 surfaces Lisbon CSX 6.370 1330 to 1900 Now you can do your own finishing of: Radio cabinets plaster, hardwood, Lisbon CSW7 9.730 1900 to 2000 phonograph turntables and record etc. Lisbon CSWO 11.040 0900 to 1130; 1230 to and speaker grilles, Con be loaded in 1500: 1600 to 1800 hobbies and numerous other 10 seconds. L isbon CSX 11.990 0800 to 1000 cases, novelties, crafts, PORTUGUESE Items The Walsco Staple Driver is a GUINEA real time and trouble saving tool 7.100 1600 to 1730 The kit (as pictured ) con- 10 brilliant colors available. for the radioman. Also extremely SALVAROR Gun, together San Salvador YSN 7.310 1300 to 1500; 1900 to tains patented WALSCO Felt Flock Spray useful for general stapling. 2300 with necessary materials, such as undercoats, ivory and This device automatically positions SOUTH AFRICA the staple after which it is driven Capetown ZRK 5.880 2345 to 0130; 1000 to brown felt flocks, brush, instructions, etc., with one 1600 fo a pre- adjusted depth the of the Capetown ZRL 9.610 0300 to 0700; 0900 to CATALOG NO. K 50 -List Price $10.75 or two strokes of palm 1030 hand. A small trigger controls the Johannesburg ZRH 6.010 2345 to 0190: 0900 to Write for full information on these items. Dept.''7 feeding mechanism. Wires and 1100 cables up to 1/4" in diameter can Johannesburg ZRG 9.520 0300 to 0700 installed with the Johannesburg .Z71 9.900 0315 to 0715 be quickly SOUTHERN Walsco Staple driver. RHODESIA Price $4.95 Dealers Net (In- Lusaka ZQP 8.910 2230 to 1800 cluding box of staples) SPAIN Alicante 7.950 0730 to 0930: 1530 to 1800 Madrid EAQ 9.370 1500 to 1700; 1830 to 2100 SPANISP MOROCCO Tetuan 6.060 0230 to 0300: 1830 to 1830 SURINAME RADIO MEN Paramaribo PZH5 5.840 1800 to 2045 SWEDEN Write for Bargain Stockholm SBU 9.530 0130 to 0145; 1930 to 1700; 2000 to 2100 Catalog of Radio Parts Stockholm SOBZ 10.780 1100 to 1720 THE LATEST IN RADIO Stockholm SOP 11.700 2000 to 2100 Stockholm SST 15.150 0130 to 0215; 0600 to PARTS -EQUIPMENT- ELECTRICAL 0700; 1000 to 1315 BUYERS' SYNDICATE to you in our SWITZERLAND 786 Carew St. Springfield, Mass. DEVICES - brought Berne HER3 6.160 0020 to 0120; 0245 to 0700; 1200 to 1700 monthly bulletins. ABSOLUTELY Berrie HEI2 6.940 1 Berne HEK3 7.380 1000 to 1045; 1510 to FREE! No obligation. 1530 Berne HEF4 9.180 Berne H E15 11.710 Tuesdays and Fridays. WRITE TO 1000 to 1130; Satur- $3.00 FOR CARTOON IDEAS days. 1550 to 1625 . RADIO -CRAFT prints several radio cartoons every MANUFACTURING DIVISION Berne HEK4 11.980 1645 to 1715 except e month. Readers ore invited to contribute humorous Saturdays I radio ideas which can be used in cartoon form. HERBACH & RADEMAN, INC. Berne HERS 15,310 Saturdays. 1000 to 1200 It is not necessary that you draw a sketchy unless Geneve HBL 9.390 1300 to 1500 yOU wish. IDEAS NOT WANTED: ELECTRONICS SPECIALISTS No electrical or radio definitions wanted. Some of t. MARKET ST., PHILA. e, PA. DEPT. E TAHITI FO8AA 6.980 Tuesdays and Fridays, those were published in the past. but tho subject 1s 522 2200 to 2400 ' about exhausted. TURKEY ' Payment is made on publication. Ankere TAP 9.460 1000 to 1615 Radio production for the first quarter of Ankara TAO 15.190 0000 to 0200: 0415 to Address RADIO CARTOONS. RADIO- CRAFT, 25 0730 West Broadway, New York 7. N. Y. 1947 totalled 4,231, 415 receivers. RAD!O.CRAFT for JUNE, 1947 61 NOISE ELIMINATION "GLOBE' SMASHING (Continued from. page 29) SPECIALS provided he is tactfully assured that his sign will work as it did before. "GLOBE" RADIO TUBES Household equipment interference OUR_OWN BRAND If a refrigerator is causing the noise, 100% Perfect,New and Fully Guaranteed, putting the radio on a different outlet in Cartons may help, but more often the refrig- 0Z4 .88 7B7 .72 35Z5 .48 erator is in need of repair. The brushes IA7 .72 7C5 .72 36 .55 in the motor may spark excessively and lA5 .72 7B8 .72 42 .49 lU6 .88 7B7 1.08 43 .59 require replacement; the commutator IBS .59 7Y4 .72 45 .44 may need cleaning or turning down. The 1LA6 1.53 12A8 .55 47 .59 1LB4 1.53 12J7 .59 50A5 1.08 belt may need replacing. I1; in doubt, ILC6 1.53 12Q7 .49 501.6 9 try to have a refrigerator expert look ILE3 1.53 I2SA7 .55 SOBS 1.28 11.114 1.28 12SA7 GT .72 SOY6 .59 ANNIVERSARY it over and make any necessary repairs. ILN5 1.28 12SK7 .72 57 .49 If it still interferes, the noise can be INS .72 12SQ7 .59 7017 1.56 3Q5 1.04 14A7 1.08 75 .48 further cut down by putting a filter sim- 5Y3 .55 14B6 .88 78 .49 ilar to that in Fig. 1 on the refrigerator. 6A7 .55 14Q7 .88 80 .39 yErrEY However, in many cases an ordinary line 6A8 .55 24A .49 84 .59 6C6 .56 25L6 .59 85 .49 6D6 .55 noise filter can be used without difficulty .55 25Z5 117M7 1.53 6K5 .59 2526 .72 117L7 1.53 and with completely satisfactory results. 6K7 .59 27 99 117P7 1.53 tA0. 6SQ7 .59 35 .55 NEU/ If the noise is being produced by an I I7N7 1.63 6X5 .55 35A5 .83 electric razor, putting a filter at the 7A4 .72 35L6 .72 11723 .88 7A8 .72 35W4 .59 117Z8 1.04 razor outlet, as shown in Fig. 2, may 7B6 .72 35Z3 .72 XXL .88 BlitrA prove helpful. The setscrew which holds Minimum Order: 10 Tubes the wall plate of the regular outlet to Orders of 100 Tubes or more -10 %d discount the box may be loosened slightly. Then on above prices the wire from the ground post of the We carry a complete Lne of Tubes

RADIO & ELECTRONIC SCREW TRANSMITTING and SPECIAL PUR- EQUIPMENT POSE TUBES. "Jan" Inspected, Fully Guaranteed SEND NOW for your free copy of this giant - 807 .98 284G 1.25 9004 .98 size, 144 -page catalog which offers you 2050 .98 3BP1 2.75 VR 105/30 .89 2051 .98 RK34 1.75 9002 .98 ' America's latest, largest line of top - 9005 .98 866A - .89 quality ham gear, parts, communication 9006 .98 717A .89 884 .89 82910 2.75 9001 .98 885 .89 equipment, tubes, tools, test equipment, 872A 1.98 9003 .98 1645 .98 amateur kits and accessories. Page after Acorn Tubes: Noe. 954 to 957 -49e page of post war radio developments - Hearin Aid Tubes: Nos. 501AX to plus a special bargain section that lists 509AX -49c Subminiature Proximity Radio Tubes, used surplus and standard -make radio and tele- in Radar Timing' Devices: (DIODE. 6.3 vision parts at famous Lafayette economy. Filament) -69c Fig. 2-Put line filters near the receptacle. POPULAR BRAND CONDENSERS ... First Quality-Fresh Stock SUPREME PANEL filter is twisted under the head of the ELECTROLYTICS BY PASS screw, in a clockwise direction, so that t et MEYER BARGAINS 20/20 0 150 39e Mfd. 400 at 600 t 3' SQUARE CASE tightening'the screw will make the wire 20 40 150 25e Supreme No. .001 - 90 O IO MA DC. PS 300 to 31. 15 10 4t 450 270 .003 DC. fit tight. The razor itself is plugged into - PS 3C8 0 lo 50 MA 9e DC, 3115 16 40 450 45e .005 PS 323 0 to 300 MA 3135 the filter box which may contain a cou- .01 9e 90 20 450 PS 315 0 to 10 0 52e .02 9e 90 4.53 EACH ple of by -pass condensers and, in some 25 No. 3107 lo 18e .03 9e 9c to I MAD 8. Supreme PS 305 0 cases, series chokes, depending on the 25 ® 25 19e .05 10e loe .1 12e 12e 4' SQUARE CASE 50/30 00 150 49e .25 lee 14e No. 41 14 filter purchased. 0 to 23 MA DC. Supreme PS 328 Minimum Condenser Order: to Condensen PS 329 0 to '"$5 A listening test should be made. If 15 EACH, , the filter does not cut out the noise, try using it at the radio instead of at the VOLUME CONTROLS Be wherever possible 500.000 OHMS. S.P.S.T. Switch. 2' Shan - 47o razor outlet. sure 500.000 OHMS. D.P.8.T. Switch. 2" Shaft - 58e to use different outlets for the razor and 2-Tube Phono Oselllefor-Uses 35W4 and SOBS- LAFAYETTE RADIO Peeks terrine wallop 4 25 radio. 5" Alnico -5 P.M. Speaker 11 oz. Mainel)...1.45 RADIO WIRE TELEVISION, INC. Output Transformer for 5016 69e RUSH Razor interference is often terrific: In 6 ft. Approved AC Line Card 25e NEW YORK 13, 100 Sixth Ave. some cases there will be nothing to do buy BOS1ON 10, 110 Federal St. COUPON but a frequency -modulation radio or turn the regular radio off while the THIS MONTH'S SPECIALS NEWARK 2, 24 Central Ave. TODAY razor is being used. Keeping the antenna of the set away 6AKS TUBES New & Guaranteed, New from power wiring and using a doublet $29e, 113, in sealed Canons GY LAS AYE Ave. York N. New ayetteY. lead -in will ,help in minimizing inter- Sixth nos IOO copy of ference.. n[}Sr[ my tree [teats moo. Catalog. order too my Send. 20% deposit required with all orders }Inter}aver order the same . Work at the rodio We ship Y day w e moth. It. Order Moner-baek n all ì \loner Realigning the radio and making Write tore guaranteetree cattalos and order blanks. every effort to get it selective will help l Dame. in down noise. With sharp selec- grate..... cutting GLOBE DISTRIBUTORS Address...... ,. (ypne... tivity, a certain amount of side -band clos..... cutting will be ñoticed, reducing the 72 Harvard St. Boston 24, Moss. ¿.------PASTE COUPON total amount of noise output of the de- ON PENNY POSTCARD tector, since smaller side bands mean 62 RADIO -CRAFT for JUNE, 1947 less audio output. There may be some easily from the noise, and whatever sep- sacrifice of fidelity, especially in heavily aration is gained is due to the selectivity built -up sections of cities, but often the of the receiver and to such other things listener is willing to hear fewer high as inherent low noise in the set itself. notes if only the main portion of the Line noise filters at the radio will audio spectrum is not too noisy. often eliminate noise due to elevators. It Usually, sets with a stage of r.f. be- is usually impractical to filter the ele- fore the first detector will outperform vator itself. sets without the r.f. stage. In some cases A simple filter the radioman can make it may be wise to recommend to the and use is shown in Fig. 3. The 2 coils customer that the set be traded in for a larger one which does have r.f. This METAL CAN OR BOX

oo I has been found excellent "repair" prac- ! tice in many stubborn cases of noise. 1 I FROM LINE I I TO RADIO A good antenna is important but not the whole story by any means. In the 1 Woo 1 shadow of Brooklyn Bridge or any of t_ __1 the other big steel bridges reception -SEE TEXT FOR CONSTANTS 3 more effective type of line filter. may be very poor. On one side of the Fig. -A running north and TELEVISION Manhattan skyline, rolls of bell wire, used just south, reception from certain stations are ordinary re- as purchased. The condensers should be may be good, but on the other side -cased type and may range HIGH QUALITY from the same stations may be of the metal KIT...A ception to 2 µf. It is a good idea for the weak. If the local noise level is high, from 0.5 too construct 3 filters (one weak signal cannot be separated serviceman to TELEVISION RECEIVER the with 0.5 -µf condensers, one with- 0.1 -if condensers, and the third with 1.0 µf ready for Easy, OPPORTUNITY AD-LETS condensers) and to use the one which is Rapid Assembly Advertisements In tits section cost_ 20 cent, word best for the given-job. To provide shield- Mr each ht,artiun. Nacre. address and Initials must ing the coils should be put in a metal the Brilliant be included at the abets rata Cash should accom- Features pany all elassHRad adrertisensuts unless placed by can about the size of a coffee can or Picture Tube! an accredited advertising agency. No advertisement LECTROVISION for leu then ten w01112 accepted. Ten percent dis- slightly smaller. They can be inserted count sis Issues, twenty percent for twelve issues. Objectionable or misleading a lrertle-menls not er- between the line and either the radio ceptod. Advertisement. for July. 1947, issue must device. reachch us not later than May 28. 1947. or the interfering ENGINEERED Radio -Croft 25 W. Sway New York 7, N. Y In some cases, where the radio is sev- BY eral floors above the street level, it may TELEVISION CORRESPOND!NCE COURSES AND SELFINSTRUC- be found that less noise will be picked SPECIALISTS Cou books slightly used. Sold. Rented. Exchanged. All ublccte. Satisfaction guaranteed. Cush paid for used up if the ground wire is left off the set courses. Complete information and 100 -page Illustrated bargain catalog Free! Write -Nelson Co.. Dept. 39. Chi- than if it is attached. The reason for cago 5, Ill. is impedance between the MAGAZINES (BACK DATEDI -FOREIGN, DOMESTIC. this that the ans. Books, booklets, subscriptions. pin -ups, eta Cata- ground terminal and the actual earth log 10e (reyundedl. Ciceron s. 863 First Ave.. New York 17. N. Y. ground may be appreciable for a long FREE WHOLESALE BULLETIN. TUBES. PARTS. stretch of pipe; noise currents flowing Bargain prices. Renshaw Radio Supply, 3313 Delatan City, Kansas City. Kansas. in that impedance set up a noise voltage cir- AMATEUR RADIO LICENSES. CO3IPLETE CODE which acts in series with the input and theory preparation for passing amateur radio ex- cuit radio aminations. Home study and resident courses. American of the Radio Institute. 101 West 83rd Street. New York City. Keeping the antenna of the set away See our ad on pago 80. from overhead power wiring is impor- Easy-to- Assemble: No Knowledge of tele- WE REPAIR ALL TYPES OP ELECTRICAL 1NSTRU- of minitilizing vision required. COMPLETE easy -to- follow ments. tube checkers and analyzers. Reaction Instrument tant from the standpoint INSTRUCTION SHEET gives you all the Co. (Electric Meter Laboratory). 140 liberty Street, Now the the bet- Yolk, N. Y. Telephone- BArciay 7 -4239. noise. The higher antenna, knowledge you need. ter! Distance from surface or elevated EXPORT AND SALES AGENT SEEKS LINES FOR This Kit INCLUDES SOUND, all com- export trade. P. 0. Box. 1320. San Francisco. electric railway lines is also important. ponent parts, and the following: longer - DON'T FAIL YOUR AMATEUR EXAMINATION I I I Very often it will pay to use a Pre-examination test based on actual FCC written exam- lead -in and to keep the flat top Specially designed Television Antenna inations $2. R. E. Hand, 3049 Via Campo. Montebello, doublet Cali,. farther away from the elevated line or . . . A $30.00 Brilliant Lectrovision seven -inch Picture Tube, plus ALL FRANCHISES OPEN FOR EXPERIENCED TEES- overhead power wires, and particularly ninon Service Men. Manufacturers of nationally dis- other tubes . Pre -tuned R -F unit in from other antennas on the same roof. tributed television kit wishes to laie up service centers . Finished front panel . - All venous television areas. Applicants must haro extensive is often television service experience and suitable equipment for In apartment buildings, this solder, wire and 60 ft. of low loss lining up television receivers. Those selected will receive difficult, but all possible efforts should servicing franch.se and will be advertised as a service lead -in cable. critter for servicing this kit. Transvlslon, Inc.. Dept. be made. Keeping the flat top away 385 North Ave.. New Rochelle. N. Y. Operates on 110V.; 50 -60 cycles BC, from the elevator housing on the roof A.C. Price: complete with ALL tubes, TELEVISION- AVAILABLE NEW "SECOND EDITION elevator and -aselen & Construction of a 5 or 7. Television Receiver"' is desirable also, since the $159.50 (fair traded) and "Design & Construction of a Visual Alignment everything connected with it is noisy. Sweep Signal Generator" at 81.75 each booklet. Imme- IMMEDIATE DELIVERY! diate del.very special television paru. IF and RF coil The importance of a good antenna We believe that the comparative- quality of this kits. transformers, cathode ray tubes, punched "vision" Television In some cet Is superior to other available sets. -It has been chassis, shields. Write for price list. Special job cannot be stressed too much. television Receiver Coll Klt 7í500A including complete set 10 acclaimed by mater schools. mashed coils for 5 or 7' receiver shipped prepaid $4.95 respects, this work is pure labor and not each. Vision Research Laboratories, P. O. Box 52, hew but it's a very important CABINET for Gardens 15, New 1o.k. very 'technical, part of servicing and not to be shirked. TRANSVISION UNIVERSAL'S "MIDGET" POCKET TOOLS. DANDY Kit End Wrenches to 7/16'. can be solved Television 12 -Pc. Set: 10 midget Open 3/16' At least half the noise jobs wood. 75 Unigr.p Midget Pliers, and Sindo of selected grain This and Slip 15% & qe With beautiful hand- rubbed Srrewholder. $12.95. Remit Today. New catalog Free t I I simply by installing a good outside TOOL COMPANY HAS IT. 1527 Grand Walnut finish. Labeled 'nobs. UNIVERSAL The change in signal -to -noise Overall alas: 17%. deep; B C, Kansas City 8, Missouri. aerial. offending 19 %" wide; 151i" FREE ILLUSTRATED CATALOG OF RADIO.ELIM- ratio is usually such that the Price: $29.95 tronica books. Servicing, home study. UHF, radio math, interference hardly can be heard at the electricity, operating. television. etc. D. B. Nephews DEALERS! Cash in on this Kit! Ideal for Publishing, Dept. CO, 300 Pacific Street. Brooklyn 2, new and lower volume control setting re- making your own Custom -Built Television N. Y. bring in programs at a satis- Receiver. See your local distributor, or for quired to write to: BUILD RADIO, PHONOGRAPH. COMBINATIONS, level. This is true even in the further information complete kite: catalog. Radian, 6922C, 21st Ave.. Brook- factory lyn 4. N. Y. case of FM radios which are not as sus- TRANSVISION, INC. Dept, RC BAR - WRITE DEPT RC 20 FOR OUR LATEST FREE ceptible to noise as AM sets, but require 385 North Ave. New Rochelle, N. Y. gptn list of Itadlo and Electronic parts. R.C. Radio Paru and piste. Co., 733 Central Ave.. Hansa. City 6. Kansas. outside antennas for best reception. RAD IO =CRAFT for JUNE, 1947 63 in A getSQyeaa A SMALL RECORDING STUDIO (Continued from page 32) it' VARIETY SENSATIONALLY NEW sirable to cut a groove which matches er level, particularly near the center of this radius as nearly as possible. It is the disc. It is not considered good prac- advisable not to cut too deep a groove, tice to record any closer than 4 inches which would result in distortion and a to the center of a record at this speed. loss in high- frequency response. It is Below a 6 -inch radius there will be a wise also to determine the maximum noticeable reduction in the higher fre- level of signal which can be fed to the quencies. This can be offset in part by TELEVISION KIT head with a given depth of cut. Other- boosting the higher frequencies smooth- Ready for wise, over -cutting, which will result in ly as the diameter of the uncut portion easy rapid as- the grooves running into each other, will of the disc increases. On some recorders sembly. No take place. This can be seen with a mag- this is done automatically as car- knowledge of the television re- nifying glass. If the grooves come too riage travels across the disc. quired. C o m- close together when cutting, an echo It is not considered good practice to . plete easy -to- will be noticed when the disc is played record at 78 r.p.m. on the rim of a 16- 'follow instruction sheet back. inch disc, as the speed of the disc past gives you all There will be a difference in depth of the cutting stylus is too high forrea- the knowledge cut, with a particular adjustment of the sanable stylus life. To obtain a maxi- you need. cutting head, when changing from 78 mum of fidelity with good economy when Reception is clear and sharp ... comparable to a moving picture. r.p.m. to 33 1/3 r.p.m. A satisfactory using 16 -inch discs, a musical selection All necessary components are included. compromise adjustment can be made if it can be recorded at 33 1/3 r.p.m. starting Nothing is required except a screw driver, is necessary to change speed frequently. at the outside of the disc. A second se- cutting pliers and a soldering iron. Only the highest quality standard parts are The highest quality recording, however, lection then may be recorded at 7$ used -the list price value of these parts necessitates individual "depth -of -cut ad- r.p.m. This will yield a recording time alone is more than 0 justment for each speed. of approximately 6 minutes without se- $300. 11 0 volts, 60 cy- P cles A.C. It is wise to check the depth of cut rious reduction in the high -frequency frequently, as even the best needle response of the resultant recordings. ASTATIC PHONO PICKUPS wears. As the point becomes dull it re- It is poor economy to use inferior Complete with L70 crystal & Hard- ware $1.98 quires more pressure to cut properly. discs. One ruined sapphire will more The frequency response of a recorder is than offset the saving effected by many I.F. INPUT & OUTPUT "inexpensive" discs, which TRANSFORMERS a function of needle sharpness. This is are not coat- 12/4x124 "x2lfj ", 466 kc. particularly true when recording the ed as evenly nor as thickly as a first - 10 for 55.40 59 ea. higher frequencies at 33 1/3 r.p.m. For quality disc, and once the sapphire point PHONO KIT best results, the over -all response of `hits the base material it is ruined. The (Contains turntable, pickup $5.95 the system should be checked frequent- material on the disc also may contain plete) ly by cutting a variable-frequency test grit or havehard spots, which result in PLASTIC KNOBS record (introducing sufficient compensa- a high 'noise level. Old dry blanks have (White. Red, Red M$hoaany and Ran.) (In high lots of too, $4.26.) Slip -on type tion electrically to offset the effects of a inherent noise level, and cause 11,4, in. with s/s in. shaft 05 recording -blank hardness, needle sharp- the cutting stylus to wear rapidly. The ANTENNA LOOPS ness, depth of cut, etc.) and observing blanks should not be stored in a too -dry 8x5 Primary and Secondary (10 the light pattern. All the items above place. for 53.60 .39 ea. can eause a high- frequency loss. The recordist will encounter a multi- GUARANTEED VOLUME tude of special problems. These will be CONTROLS Speed considerations presented in itemized form, with Less Switch. 48e 10 for $4.45 their With Switch 59e 10 for 5.45 When recording at 33 1/3 r.p.m., it is causes and remedies, in the next and 600,000, 100,000, 25,000 ohms; 24 meg, 1 meg. 2 mere. conventional to record at a slightly low- concluding article of this series. FEDERAL SELENIUM RECTIFIER 6 or more . . .99 ea. Less than 6 $1.09 ea. RESISTOR CABINETS All wood construction, 6. drawers 24 compartments $3.09 Complete with 100 assorted % w $7.95 and 1 w resistors Bargain! Guaranteed! 100 Assorted Bypass Condensera 600V Value $11.00 Special $6.95 SUPERIOR Model 411f=ft i 670 -Super-Meter A Combination Volt-Ohm Milliammeter plus Capac- ity Reactance Inductance and Decibel Measure- ments. Complete with test leads and netrvF $ fions 2 8.40 RVo° Write Deat. C -6. 20e,1. Deposit with order renuired. Please add sufficient postage. Excess will be refunded.

'tizietei ELECTRIC CO., Inc. 601 Broad St., Newark 2, N. J.

Photo D -How the chip is thrown when recorder is working properly. . 64 RADIO -CRAFT for JUNE 1947 e

NEW SUBMINIATURE PRINTED CIRCUITS (Continued from page 25) effective resistive and conductive paints applied to the etched surface and al- are used on the steatite plates, inasmuch lowed to dry in air. 16 4- as they can be fired on at temperatures ALLIEp' S p A G E ranging from 160 to 800 degrees Centi- Range and operation grade. Subminiature tubes will deliver 50 Absolute cleanliness is necessary if milliwatts of power or more to an anten- CATA14G the paints are to adhere. The third unit na. Although receivers are available RADIO of Photo B was made by first wrapping that provide satisfactory reception on a stencil of the coil pattern around the field strengths of 1 microvolt per meter, tube, using masking tape. The glass it is more practical to assume that 2E36 2E36 2E36 6K4 ANT. r e ,

2 MEG d MEG 2MEG

!MEG IMEG

.0U 2 MEG .002 IMEG .002 SOOK

L5 tr

120MA I- "=_s_ ,+.5V +45v +135V j200MA Fig. 3- Hookup of The 4 -tube printed rec elver does not differ frofn 910 standard circuits. R M1EtE envelope was then etched in fumes of miniature receivers will require field hydrofluoric acid (sandblasting could strengths of the order of 100 microvolts have been employed) which roughens per meter for satisfactory reception. For N ' the surface and allows excellent adhe- a transmitter power of 50 milliwatts and ßY sion of the paint to the Miv envelope. After a 100- microvolt receiver theoretical cal- etching, the .hydrofluoric acid was neu- culations yield a distance of transmis- LARGEST STOCKS tralized with strong caustic soda solu- sion of 9.8 miles. SPEEDY, EXPERT SERVICE! tion, and the envelope washed thorough- The ideal assumptions made in deriv- ly with soap and water and rinsed in dis- ing formulas for distance are hardly Send for your FREE copy of the most tilled water. The conducting was complete Buying Guide for Everything in paint realized in practice, particularly if one Radio. Features thousands of radio and uses an antenna of convenient size and - electronic parts, latest homeradios,sound shape. For a personal radiotelephone systems, amateur gear, builders' kits. Spray Kit (or transceiver) servicemen's equipment, tools, books - a single short telescop- world's largest stocks of quality equip- . Lite -Koat ing antenna is preferred if any is used 'ment -ail at owest prices! Expert help;

Carbon -X at all. Coupling to and radiation from fastest service!. . the antenna unavoidably will be far from Ne -O Tester More than 10,000 item!-Coin. -Lite optimum: If used in a building or on a píete li nes of all leading makes. Largest stocks of hard -to -get

street, - GC LITEKOAT KIT absorption and reflection from parts. Lowest moneysaving "Glows In the dark." Lu- the walls of the buildings takes place. prices. Get everything yo minous ufte coating- need in from emits light in dark For of- These and other factors make the dis- Radio ALLIED! lice. home, ate- No. 184-0- Deluxe Kit. tance of operation a matter which must Pablic Address -entirely new Dealers Net $1.50 be determined experimentally. line -new styling, new design features. Packaged Ready -to- G -C CARBON -X The personal radiotelephones shown in Use Sound Systems; everything in A good method to touch Mr Photo B have been used amplifiers, speakers, mikes, worn and noisy spots an car- successfully in intercom and recording. bon volume controls. - CAR various .te'sts at the Bureau of . Stand- BON -x is an electrical- conduc- Amateur Gear -immediate de' tor. No. 1205 -2 os. he'll. ards. Excellent communication was ob- livery on latest communica- Dealers Net tained with a standard transceiver locat- tions receivers. Time payment Ose plan; -ins ed in one of the rooms a mòdern - trade accepted. Head. of four quarters for all ham and ex- story laboratory. and a subminiature Eft perimenters needs. GC NE-O-LITE transmitter operated from- all other parts: Roordio F mbs sod Data TESTER of the laboratory as well as from Handy Dictionary of Radio Tema Radio Circuit NeOLÌte Tester the grounds a half a mile away. Clear Radio Handbook every serviceman, ex- reception Radio Builder's Handbook periment was also possible with the ooks Simplified Radie Servicing should BL used on e0oV.A.C. fo transmitter located in a modern metal - Radio Data Handbook 500 'V.A.C. D.C. ALL SIX BOOKS No. 37.799 , . $1.00 No 5100ainglo Cost- roofed automobile (door closed) six er on Parallel Resistance end Serin Ca scitaooa e Net 10e Dealen blocks from the transceiver, even though Calculator. No. 37-960 28e Display ;i 1a or R -F Resonance and Coil Winding 1a labte many buildings prevented a clear line - . Calculator. No. 37.965 iSc - v of- sight transmission. A light antenna

G -C FELT -K OAT consisting of a thin rigid wire 18 inches . 8 FLOCK FINISH long was employed in these tests. ALLIED RADIO SPRAY KITS . While miniaturization is a Easy to supply Bock for refinishing turn- feature ALLIED RADIO CORP. tables, cabinets grilles, etc. Kit con- which has attracted the greatest atten- $73 W. Jackson Blvd., Dept. 24-7 Chicago 7, IR. tains specially. designed .pray gun, 2 col - ors flack, tion in the printing undercoats, thinner, brush, . In- of electronic circuits, Send FREE Radio structions, Catalog etc. No. 180 -2. Deaiert Net $6.45 there is another feature of equal or O Send 6 Books No. 37-799 S Sold By All Jobbers Cl Send Calculator No. 37.960 eodosed Write for complete catalog today greater importance. The process makes Send Calculator No. 37.955 RADIO DIVISION DEPT. D it possible to effect economies in production not possible in present assembly -line Name e Mfg. Co., Rockford, III., U.S.A GENERAL CEMENT methods. A single operator can turn out Manufacturers of over 3,000 products Address

_ thousands of Sol., off-re, in or,nt'Poi rille, printed electronic plates ( CoTtinued. on page 70) City Zone....State RADIO -CRAFT for JUNE, 1947. 65 OUR 24th YEAR TRANSATLANTIC NEWS SUPERIOR SERVICE (Continued from page 33) GOVERNMENT FIRST QUALITY LOW PRICE METERS tion. Many attempts have been made to 0.1 MA G.E. type DO -41. 3" 23.50 reduce it by the use of special needles, 0 -1 MA McClintock 90 ohm, 2" 2.45 SURPLUS 0-1 Amp RF G.E. 2" model 8DW44 2.45 of filter circuits and of different ma- 0 -3 MA Gruen 2" scale 0- 30:300:8000 1.95 terials for the record blanks. Some We have on hand a large selection of 600 =0-500 Microamps WE 4" scale 60 -0 -50 3.75 Radio and Electronic Equipment purchased All above in bakelite case needles are a little better than others, cure. Filters are al- from the United States Government. and but none effects a solicit your inquiry on practically any equip- OIL FILLED CONDENSERS most useless, since surface noise is ran- All Standard Brands ment or component parts used by the dom, occurring not on one frequency or Army or Navy. Listed below are only a few 1 mfd 600 volt DC AS 2 mfd 600 volt DC .49 narrow band of frequencies, but on all of the many items we now have in stock. 10 mfd 600 volt DC .98 frequencies from about 1,500 cycles up- 2 mfd 1000 volt DC .79 Discs of soft plastic material, . METERS 0.6 mfd 1500 volt DC .25 ward. 0 -250 MA DC Weston Model 301: 3" case 22.95 0.26 mfd 2000 volt DC .25 such as the vinyl compounds, may lessen 0 -50 DMA DC G.E. Model DO -41. 3" case 2.95 2 mfd 2000 volt DC 1.75 0 -1.8 KV DC- Weston Model 301. D -1 MA 4 mfd 2000 volt DC 3.25 the noise a little, but they also cut do in FS, 3' case, complete with Weston Multiplier. 5.25 0'20 KV DC Weston Dlodel 301. 0 -1 MA FS, 4 mfd 4000 volt DC 5.95 the high- frequency response of the pick- cue mfd 7600 volt DC 1.50 9.25 0.1 reason? Well, ,it is just that 0 -150 V 'AC Weston Model 478. 3" case 2.95 up. The 0-1 Amp BF Weston Model 301, 3" me 3.25 with these softer matérlals what is known as "cold flow" is apt to take place CONDENSERS .6 mfd. 2000V DC, CD type TJH. 011 impreg- when the needle is traversing the tiny, nated .75 1. mfd, 2000V DC. CD typo TJK. Oil impreg- sharply bent curves of the grooves cor- nated 1.00 audio 4. mfd. 2000V DC, CD type TJH, Oil impreg- responding to the upper frequen- nated 1.75 cies. The material has not sufficient d, 1000V DC, CI) type TJH. 011 impreg- canted f 2.00 rigidity to force the needle point to fol- Transmitting Cond. 0008 mfd-8000 VW DC. low the grooves. Instead, the needle de- Seasamo typo F2ISH - .75 forms- bends -the grooves as it tra- RELAYS Time delay, Cramer type TD2 -1209. SO sec verses them and they spring back into delay timer, 110 V 80 cycle 10 amp AC SPST make contacts 4.75 their original shapes after it has passed. Relay Struthers Dunn type 8BXX110. DPST microscope will show that the up- make. 30 amps AC contacts 110 V 60 cycle coil 2.35 The Relay Struthers Dunn type ADBTS. DPST per audio frequencies are on such a 30 amp AC contacts, 3 amps 60 cycle coil 1.75 Relay. Struthers Dunn typo 813X.X110. DPST record, but when it is played cold flow make, 4 amp DC contacts -.125 V DC coil 1.75 ARMY RADIO PHONES prevents them from being reprodhced. They're Weather -Wafer and Shook Proof CIRCUIT BREAKERS When we say they are made to Army specifi- Decca's first line of attack was to Heinemann Circuit Breaker. 15 Amps. Curve 2. cations, that's enough assurance they must be produce a pickup with no resonance 120 AC .95 of best quality. These Army Radio Phones Heinemann Circuit Breaker. 20 Amps. Curve 2. audio Figs. 1, 2 and 120 V AC .95 are perfect and were O.K.'d by Signal Corps within the range. Heinemann Circuit Breaker. 35 .Amps. Curve 2, Inspectors. These Dynamic Mikes and Re- 3 illustrate its make -up. The body of 120 V AC .95 ceivers. were used on aircraft and tank intercommunication systems. Use them for record- the pickup is 1% inch in length, 1% FUSES ing, for hatteryless phone, for pocket size set inch in diameter and % inch in depth. 2 Amp, 3 AG Littelfuse. 5 for .12 loud speaker or talk throw -h your radio set. 160 for - 1.95 Phones, When balanced on the tone arm its 15 Amp, 3 AO Littelfuse, 5 for .12 We bought a good many of these Radio for a deal 100 1.98 they are brand new, and cost great weight is six-tenths of an ounce. As will K Amp. 8 AG Littelfuse. 5 for .12 more thanan ydy can get them for. 100 for 1.98 A re thane dynamic hand mike, be seen, it is of the moving iron type 2 earphones, headband, cord set $345 and contains many interesting features. MISCELLANEOUS A wonderful buy only Clcellhoke, S.IB ® 105 MA DC. Uncased but trop - for The rubber mount of the armature al- zed .39 movement but enforces Heater Strip. 230 V. 200 Watt Chromate.: type SELENIUM RECTIFIERS lows free lateral PT -702. Screw terminals. 7" strip .60 Intercom power complete rigidity fore and aft. The mag- Cartridge heater 115 V 25 Watt. Immersion For AC-DC Portables. cove,. 10" long x K" round case. With asbestos supplies. Replaces 29 types of Rectifier Tubes nets are so situated that when a record covered 10" leads. type C-304 .50 1- 6 95c 500 ohm Pot. 50 Wattount IBC,IRC, 155" x Y." shaft sin- 6 -49 85c is being played they are little more than gle hole panel mount .95 50 -99 .80c one sixteenth of an inch above its'sur- 18.000 ohm resistors, 50 Natl. % Ferrule mount .25 Each complete with instructions Coax cable, 52 ohms impedance. 50', face. The maximum flux change through with connectors 3.55 Seleyn. 110 V cycle 3.95 5G in 60 SELSYN Synchro Transmitter, used the armature is thus obtained. The pivot Linesman's polo climbers 4.50 pairs as transmitter and follower 5 Safety belt with strap. State belt dew nted 5.75 110v AC per pair WW 00 of the armature, being near the top of 4 section sertirvl telescoping antenna. 6%' to a base. with insu- Indicator type 11 -1 in armored case, pickup, is well away from the area 23' extended, %' OD at base 9.00 the lator and standoff side support 10.50 per pair -of flux change. The playing tip of the Neon Bulbs. 0.F. 54W, 115 V. BAYONET baso Heinemann ercuit breakers- 6 -20 -85 T.Ts 4% Bulb, tars NoF .15 66 amp; 115v magnetic type 95 armature is of sapphire; after 1,000 Dlug auDDressms- 0 for .25 or AC; 100 for 5.50 Twin Icad 800 ohms: records the pickup is opened by undoing Test Clip. Frenkol w /point for making electrical per 100 feet 2.95 its connection without removing- insulation .04 the milled screw, the armature and Dressaee Bolder. excellent for station logs. reg- RG8U 52 ohms coaxial cable: mount are removed and thrown away ular letter else BSS' x 11" with extra clip for per 100 feet 4.25 Polling spare sheets. also protective cover. and replaced with a new armature com- Reg. Signal Corps typo 1.00 Jeweled lamp assembly. l' diameter.' Panel mount BC 645 A Transmitter- Receiver plete with mount. Candelabra screw base socket. Red jewel .29 420 -460 Mc; 460 -490 Mc: complete with 15 tubes, including W.E. 316A doorknob. Brand This pickup has no resonances below SPECIAL $25.00 OFFER new with conversion diagram. For e¢í4.95 14,000 cycles and surface noise is very On a deposit of $5.00 we will ship you C.O.D. Freight less than the cost of the tubes.... .9 Collect a large quantity of Government Surplus Radio slight when it is in use. Shellac is used Items subject to your inspection and approval. 11. BC 406. 15 tube. 205 Mc. Fixed tuned re- for the record blanks, the particles of after Inspecting you are not more than satisfied. ceiver. Complete with tubes. return to us Freloht Collect and all it will have cost Wt. 80 lbs. $15.95 the filler being ground very fine and you will be freght charges one way. You should be this to dispose of n few of the Items that you may .passed through a sieve with a mesh of not need for the entire root. Thls is the cheapest way SCHWEIN Free and Rate Gyro Operates from we can sell you War Surplus Radio Material. Our 24v DC. Complete in metal case 300 to the inch; they are thus too small warehouses are filled with thousands of choice Gov- ready for use $5.00 of audible fre- ernment Surplus Radio Items. Lots of them we eo to give rise to waves not have In sufficient quantity to advertise nationally If not rated 250 with order, balance C.O.D. quency. and the cost of Inventory ng, Remixing, correspond- All prices F.O.B. our warehouse New York. ing, etc., would only Increase thelr cost; therefore The recording head is of the moving we make this offer. No order under $2.00 low mechanical We ship to any, part of the globe coil type with very Above Prices F.O.B. Baltimore inertia. The range of frequencies actual- Minimum Order $2.00 ly cut on the master record is from 30 The Abell Distributing Compány LEEDS RADIO CO. to 14,000 cycles. No monitoring or contrast compression whatever takes place 5 E Biddle St. Baltimore 2, Md. 75 Vesey St., Dept. 45 The gain control is Send fer Our Flyers 7 -2612 New York City 7 during recording. Ham* Items Interested In COrtlend set before recording begins to prevent

66 RADIO -CRAFT for JUNE, 1947 an overload occurring on the loudest radio- phonographs, almost all of which passages. It is not touched again. When have loudspeakers peaking at or about Electronics Made Easy! a very soft passage occurs the level of this point and then showing a falling i the music is actually allowed to fall, characteristic. It is found in practice if need be, below the noise level. This that a rise of 3 db per octave is the most may sound surprising, but it is amply that can be used profitably: if the rise justified by the results. During the play- is steeper the pick -up needle is liable ing of an orchestral record one is so not to track properly at high frequen- entranced by hearing the music played cies owing to the sharpness of the curves as the conductor's baton (and not the of the grooves. DECIBELS Though these records Magi-Klips KIT can be used with very Build 18 Experiments at Home- Is good results on ordinary No Tools! , itII1ll0 ==óis:i5'i'-^-m===me=s radio -phonographs, only RADIO RECEIVER. HOME BROADCASTER. 5 11111 PHOTOELECTRIC RELAY. CODE PRACTICE a specially designed re- OSCILLATOR, SIGNAL TRACER. REMOTE 0 CONTROL RELAY. Phonograph Transmitter In. i1111111 _IggillW/M producing instrument tercommun[cat ion Amplifier, Code Transmitter, 5 can Radio Frequency Oscillator, Telephone Line Am. fiI.IIIIIi 3db PER OCTAVE bring out their full Miller, Electronic. Switch, Phonograph Amplifier. beauty. Radio and radio - Temperature Control Relay. Contact Detector. Ir 60b PER 0CAV Electronic Metronome. Interval Timer (one-shot). - AMPLITUD phonograph designers Interval Timer (repeating). are usually well satisfied With a Magi -Klips kit sou cover the entire fled . of radio and electronic engineering theory pidckly in 1 if the harmonic distor- your Sparo timo. IL's simple to arrange the compo- .=c,.11111 :):: l5 nents for each circulL No soldering. No tedious wir- " l I0 30 50 00 4 0 1000 3000 I0 000 i4m0 tion of the reproduction ing. Kit operates on 110 r. AC or DC and includes CYCLES PER SECOND does 5 3575 rectifier. 5015 power amplifier. 12SL7, double not exceed per- triode, powerful 4" speaker -mike. plate relay, broad- Fig. 4 -The recording characteristic curve for ffrr recordings. cent. This undoubtedly cast and SW coils. tuning condenser and generous supply of resistors, condensers. chokes. extra wire. fulfills require- Parts worth double the of kit. monitor's most price knob!) directs that the hiss, ments, so long as the a.f. response does Kit's 48 -page manual has complete loetroetlans which is noticeable only on and diagrams easily followed by the beginner. Re- passages not extend much beyond 5,000 cycles. member. you need no tools, except poselbl a screw- that are exceptionally pianissimo, is driver, with a Mao I. I( lips electronic not But when an amplifier is capable of a and radio experimenter's kit 29.75 annoying. response up to 14,000 cycles such a per- complete The recording characteristic is shown SCHOOLS -Magi -Klipe KITS are excel- centage of harmonic distortion would lent equipment for laboratory and dam- in Fig. 4. It will be seen from 400 room. Write that cause unpleasant effects owing to the for special discount. to 30 cycles at constant amplitude there production of parasitic difference DEALERS -Some territories open. Write is a fall of 6 db per octave. After the and for your trade discount. summation notes, whose number in- change -over at 400 cycles the charac-' OSSR & TAYLOR COMPANY teristic (constant velocity) is level creases as the frequency range is 'wid- Dept C. 1340 Milvia at. to ened.' Berkeley e. 04111. 3,000 cycles. From that point upwards Please ship Megl.Klipa electronic kit (s). Many textbooks state that phase dis- I enclose S the rise is 3 db per octave. This rise is 0 Please mall Dluetreted folder on the Maa1dUIN tat. deliberately made to begin at 3,000 'These records, imported from England, are Name being sold to a very limited market in the United cycles because it is realized that the States, the supply being very short. Street records will often be played on ordinary (Continued on page 68) City slate ORDER. .a,t\ / 1, OPENING DEPT.

:OIfON RAD/0 WiOREHOUfE 73E. MILI S7., DEPT. 63, AKRON, ONIa

Yes, I too want Olson's "Same- Day Service." Send me your new big Bargain Book FREE.

NAME

I ADDRESS

LUTY STATE

RADIO -CRAFT for JUNE, 1947 67 ACTUAL TAPE RECEIVED AT 50 WORDS PER MINUTE ACTUAL TAPE RECEIVED AT 50 WORDS' TRANSATLANTIC NEWS N D (Continued front pape 67) -In Code Recorder BC-1016 rD D tortion is of small account in radios and phonographs. This may be true enough o where the cut -off is in the region of 4,500-5,000 cycles; but it does not hold Us good for wide frequency range audio 0 amplifiers. Fig. 5, by illustrating a very ti Ark' TANT WAVE FM

FREQUENCY I

W A

A F. Naz

N > n O c > r- 51.5.TANT WAVE FORM I- D GENERAL-Designed for ink recording of standard code signals at speeds up to 400 °m es words per minute on a %- paper tape. Made by Waters Conley Company. > Rochester, Minnesota. m 0.2 APPLICATION -a) Designed primarily to be connected to the output circuit of a radio m W receiver. Operates on a signal from 0.15 to 60 volts, usually connected ae directly across the speaker voice coil so that signals may be heard as well f.... Frequency response 600 to 6000 cycles per as automatically recorded. > b) Direct Keying recording from an automatic keyer or from a hand keyer ~ etc. to record messages or for code practice, B c) Can be operated from a telephone line which carries the radio signals to the recorder from a remote location. POWER SUPPLY -Operates on 117, 170. 210 or 240 volt 60 -60 cycle alternating current or within 10% of those voltages. w POWER CONSUMPTION- Approximately 140 watts operating approximately 85 watts m in standby. a z COMPONENTS -Fully equipped and assembled. Just connect to voice coil of the E speaker on your receiver (or to a key for code practice) and plug into your power line. ÿ Contains the following: Bodine variable speed drive motor with fan ,n Three pens (use Higgins "Eternal Black" ink) Power Cord Ó Technical manual with instructions and wiring diagrams O. 6 Spools of tape (1000' spoofs). These spools can record up to 20,000' c of messages if necessary (extra tape available from radio supply houses) > Amplification- bridge circuit with the following tubes: 1 6SJ -7 1 ESN -7 2 5U4 -G 1 61i6 2 6LS I- x 14%" deep; Complete . Steel Cabinet 101/4" high x 199/4" wide $ Fig. 5- Waveform changes from phase change. o wt. 80 158. Designed to fit anti standard 19" rack. Height is 8%" 95 65 lbs. when cabinet is removed fer rack mounting. > and wt. NET m F. o.9., N. S U R P L U S NEW GUARANTEED r.< simple example, will serve to show what w orn ac effects phase distortion may have. Sup- m rated concerns, (Dun & We e.O.D's seat unless aeromoanled by 25% deposit. Orders accepted tro Brad- > - s pose that a sound made in the studio w street) Public and Educational NonPrott Institutions, Governmental Agencies, etc., on open account basis. i- consists of two frequencies with the phase relationship seen at A; if the MARITIME SWITCHBOARD ó phase of the higher frequency is shifted H . Street New York 13, New York 90 degrees, as at B, during recording or á 340 Canal reproduction the resultant waveform AT 400 WORDS PER MINUTE ACTUAL. TAPE RECEIVED AT 400 WORDS ACTUAL TAPE RECEIVE` has a totally different shape. The shape is again entirely altered if the phase - is 180 degrees, as seen at C. B and DC POWER ATTENTION Amateurs - shift C represent very simple forms of phase Experimenters- Inventors distortion. Imagine what would happen 4 SUPPLY Cut your cost on radio sup- to the complex sounds made by a full plies and equipment in half. & BATTERY Clip coupon today. orchestra if they were reproduced by Hundreds of "hard to get" war phonograph with a wide frequency CHARGER surplus items along with tho best a In standard brand equipment -all range in which phase distortion took nt great savings to you. Let us Just the thing to know your particular requirements. place on the grand scale! Phase distor- demonstrate Auto IMMEDIATE DELIVERY. tion is then of great importance in an Radios or for the serviceman to SEND THIS COUPON TO amplifier with a range of 30- 14,000 repair them. Eliminates storage bat- cycles and steps have been taken to re- assures accuracy in your NIAGARA RADIO teries and SUPPLY CORP. duce it to negligible proportions. demonstration. Works on I I 5vAC seo Greenwich St.. is New York C. N. Y. The Deccola, as the reproducer 50 -60 cycle delivering 6vDC at 4 called, contains four stages of triode amp only $1 6.75 or 6vDC at I0 amp Name Class-A amplification. Careful design for $25. Ademe has reduced the harmonic content to City 0.5 percent. Three 12 -inch loudspeakers GREENWICH SALES CO. are used, arranged on the convex arc 59 Cortlandt St. New York City 7 Cali. No: of a circle so that the sound is evenly

68 RADIO -CRAFT for JUNE, I947 NOW AVAILABLE FOR IMMEDIATE DELIVERY FROM STOCK! THE NEW MODEL 670 sui' E R METER A Combination VOLT -OHM -MILLIAMMETER plus CAPACITY REACTANCE INDUCTANCE and DEC I B E L MEASUREMENTS.

Added Feature: The Model 670 includes a special GOOD -BAD scale for checking the quality of electrolytic condensers at a test potential of 150 Volts. Specifications

D.C. VOLTS: 0 to 7.5115/75/160/76011,500 /7,600 Volta. A.C. VOLTS: 0 to 16/30/160/300/1,600 /3.000 Volts. OUTPUT VOLTS: 0 to 15/30/160/300/1.500/3,000 Volts, D.C. CURRENT: 0 to 1.6/16/150 Ma.; 0 to 1.6 Amperes. RESISTANCE: 0 to 600 /100,000 ohms; 0 to 10 Megohme. CAPACITY: .Col to .2 Mfd., .1 to 4 Mfd. (Quality' test for electrolytics.) REACTANCE: 700 to 27,000 Ohms; 18,000 Ohms to 3 Megohms. INDUCTANCE: 1.75 to 70 Henries; 36 to 8.000 Henries. DECIBELS: -10 to +18, +10 to +38, +80 to +68. Housed In a rugged, crackle -finish steel cabinet complete with test leads and operating instructions. Size 51h" z 73/a" z 3 ".

PLEASE PLACE YOUR ORDER WITH YOUR REGULAR RADIO PARTS JOBBER. IF YOUR LOCAL JOBBER CANNOT SUPPLY YOU, KINDLY WRITE FOR A LIST OF JOBBERS IN YOUR STATE WHO DO DISTRIBUTE OUR INSTRUMENTS OR SEND YOUR ORDER DIRECTLY TO US.

SUPERIOR INSTRUMENT CO., 227 Fulton St., Dept. RC -5, New York 7, N.Y.

distributed and there is no beaming of DEALERS! SERVICEMEN! the high, audio frequencies. One can walk about the room without finding the These VALUES mean high notes stronger in some places than PROFITS for YOU! in others. All merchandise offered below is BRAND NEW. and FULLY GUARANTEED. Our enormous stocks The Deccola is an electric phonograph and facilities enable us to give you IMMEDIATE only; the present models have no radio DELIVERIES on all merchandise listed. equipment. You might that no TERRIFIC BUY FOR P.A. MEN! think Astelle R -3 Crystal Handmiko, with one now would buy a high- priced 6 ft. R.C. Mike Cable W$4 50 phonograph (the Deccola costs the WILLARD 2 -VOLT equivalent of over 800 dollars') no matter how good its performance might be. STORAGE BATTERY Exact replacement for GE porta. bies - brand new each $2.75 Willard 6-volt (3 -cell) storage battery, brand new $7.95 Radolek's big Free Profit Magnetic Magnetic Cutting Head. Special 61.93 Guide Catalog and Profit Telegraph Corps pro volt SRaAl ib tore for Poelabie & Farm Bulletin supplements keep rO Sels. Replacement for GE LB -530 $1.55 e RADIO PARTS AT THESE PM SPEAKER VALIIESI you abreast of the As LOOK rapidly Alnico 5 5' PM 1.4$ changing radio Alnico S 8' PM 1.95. Alnico 5 8 PM 3.25 situation. Buying from 450 Ohm 4' Dynamic 1.89. P.adolek means greater MAGNAVOXVOX FP" FILTER CONDENSERS s mfd volts values, better service SOUND SYSTEMS 18 mid 500 65c 8-8 mad 500 volts 70e and more profits. Make 40 -20 -20 rnfd 150/150/25 V 40e METER SPECIAL! Radolek your buying FREE 3e DC Mllliammotor 0 -1000 mile $1.95 headquarters. CATALOG VOLUME CONTROLS 25M ohm Year Type 50M ohm Cat, Any 100M ohm With 250M ohm Switch 4VC Large Stocks 500M ohm Less p Three speakers Megohm provide wide -angle coverage. 2 Megohm Switch 28e 22% VOLT "B' BATTERIES with leads 359 Fast Service MIDGET VISE -SPECIAL! SET, MINIMUM ORDER $5.00 Well, it has been on the market only a INCLUDE: deposit with order -Balance short time and most of our English C.O.D.LENCILh All u2y litt

factories were closed down for several .. RADOLEK CO.. Dept. C -127 GENUINE MAJESTIC 601 W. Randolph St.. Chicago 6. III. weeks at the beginning of this year (r1 send your FREE Profit Guide Catalog. through lack of coal; but over 2,000 ]I RADIO PARTS SERVICE Name have been sold so far in this country Address and the demand is steadily increasing. 53 YESEY STREET NEW YORK 7, N.C. Dbonograph is being "Mae than 10.000 satisfied Radio 'The sold in the United Dealen and Servicemen since 1540." SAVE AT RADOLEK States by an American agent for $1400.

RADIO -CRAFT for JUNE, I 9 4 7 69 Mr. Dealer and Service Engineer: Shake hands with "Inini Hyca,p" now i n this LY-

AN"

VETACelalif-- This is an unusual test offer- now you can test for yourself the high efficiency and quality of the well known "Iliini- Hycap" condenser.

HERE'S THE SIMPLE "GET- ACQUAINTED" PLAN: 1. Ad- vise us right away which one of the two illustrated condensers you wish to test (select one). 2. Enclose 15c only in stamps or coin (to cover cost of mailing and handling), along with the name of your local jobber and we will promptly send you the condenser of your choice, together with our latest catalog. You'll want more of these long -life "Illini -Hycap" condensers when you see how they improve your service work and customer satisfaction. Buy them from your jobber. This offer may not be repeated again - ACT NOW! 1= IIIIni- Hycap" 20MFD. Working voltage 150 D.C. Part No. IHT -2015. 2-"IllIni-Hyrop" 8MFD. Work- ILLINOIS CONDENSER CO. ing voltage 450. Pad No. IHTa450. 1616 NORTH THROOP STREET CHICAGO 22, ILL.

NEW SUBMINIATURE PRINTED CIRCUITS RECEIVER (Continued from. page 65) XMITTER per day at the cost of a few cents per plate. It is not necessary to cut w'res to length, bend them into shape, and indi- 151!!. vidually solder or connect them to a "Servkla9 by Signal Substitution chassis. With the printed technique, each Learn about this modern dynamic approach unit is a reproduction of the master pat- to rodio servicing with ONLY BASIC TEST terns, which EQUIPMENT. reduces line rejects to a ... Fully described in a 120 page book minimum. Substantial savings in wiring available from your Precision Distributor or and inspection and reduction of rejects factory at 354. makes the process economically at- ... Schools are invited to inquire regarding tractive. quantity orders from our Educational Division. Work on the miniature transmitter P R E C I S I O N and receiver units was to a great extent APPARATUS COMPANY INC. carried out by the members of the staff ELMHURST 4, N. Y. of the Ordnance Development Divi:ion, Menule,tu.em el fine Tut [a..ivment National Bureau of Standards, volun- 50b0 TELEVISION ELECTRICAL LABORATORY tarily devoting their after hours to the program. Space does not permit naming Your who Price all showed extreme interest and as- sisted in producing the Write units. Specific CRAFT544SN3 BARGA/h/rj_. for Quantity Prices acknowledgment is made by Messrs. A COMPLETE SET OF TRANSMITTING AND Brunetti and Cronin to J. J. Gurtowski, RECEIVER TUBES Robert L. Henry, and Miss C. G. Moon, FRE WORTH $35.00 who Hi -Power BC -654 -A Is combined transmitter and receiver made important contributions to Electric Drill designed for portable or vehicular operation. The fro the methods and carried out the printing Realty EA° euency range of both transmitter and receiver is weight. Three continuous from 3700 to 5800 kilocycles; all stages of the units. The electronic phases were Jaw keyless chuck. 011 bronze hearings. gang tuned by anti -bock lash worm gear o n. flexible bber cord With plug. dial mech- executed by Max Shufer, G. J. Tedore, 000 rpm at full load. cOperates at 110 anisms. V. AC or DC. Each $17.95 P. E. Landis, L. A. Riley, and E. A. NO. 6202 YOUR GUARANTEE A of Radio Parts We Treasure Chest will ship you at once the above receiver and Vogelsang. Additional work on the de- Contains transformers, condensen. dial controls. grottier and include FREE a complete sot of 13' re- Insulator, terminal connectoro. coils. practically ceiver and 2nLtter tubes. velopment and perfection of new meth- nil types of itches. Many moro useful Items RUSH YOUR ORDER ods of printing electronic circuits and NO. 650. 15 lb. Nit for only .... $450 55 Deposit- Balance Express collect - Send Cheek or money order. including studies of their performance is being postage. No C.O.D.'s. Write for new free MANUEL KLEIN IND. Corp. carried on in the Division by a group 74 C. CORTLANDT ST. NEW YORK 7, H. Y. under the supervision of P. J. Franklin G & E EQUIPMENT SUPPLY CO. and Dr. R. W. Curtis. 400 k. SANGAMON ST.. CHICAGO 22.111. 70 RAD 10 -CRAFT for JUNE, 1947 AND IF YOU NEED TUBES -WE'VE GOT 'EM! Send us trial order. This will nvcem you we merit your iron. - DEALERS SERVICEME N$ quick and FULLY GUARe ÑTEED JOBBERS TUBES and Standard brand merchandiséy Lots of Lots of 10 l0 Type Each Each Type Each Each XTRA SPECIAL BUYS! STANDARD BRANDS 1H5GT 65c 55c 7117 50c 40e 1U5 39 35 7C6 50 40 At Outstanding Prices! IV 60 50 7Y4 50 35 LEADING 5U4G 50 40 7X7 50 40 5W4GT 50 45 TAFT 45 40 BRAND 12" P.M. Sneaker 5Y3GT 40 37 XXL 50 40 Alnico 5 Magnet 5Y4GT 45 37 12A8GT 60 49 AC PHONO Packed 4 in a carton $5.95 ea. 6A7 62 50 12J7GT 50 42 Lots of 12 $66.00 6A8GT 62 44 12Q7GT 53 45 MOTOR 6AB7 69 65 12SA7GT 60 39 60 cycles, 115 8" F.M. Speaker $2.75 ea. 6AC7 69 65 12SQ7GT '50 39 volts with Turn- Lots of 12 $30.00 6C6 50 42 12SK7GT 50 40 table with $495 6BA6 75 50 24A - 50 39 Standard Make 5" P.M. Speaker $1.39 6F6GT 45 40 68 50 6" P.M. Speaker 1.89 25L6GT Crystal Pickup. Com mete 6116 48 44 25Z5 63 50 4" P.M. Speaker 1.29 6J5GT 63 50 25Z6GT 62 51 6K6GT 59 39 27 42 38 SIGNAL CORPS P.P. Input transformers $ .95 ea. 6K7 60 50 35L6GT 60 50 DUAL HEADSETS Lots of 12 - .85 ea. 6K7GT 60 44 35Z3 65 60 2000 ohms with 6 ft. cord 6K8 60 54 35Z5GT 55 42 and tips. Also 8000 ohms 40 z 40 Electrolytic Cond. 150 V. $ .49 6L5G 65 40 43 90 60 high impedance, with two 50 x 30 Electrolytic Cond. 150 V. .49 6SA7GT 50 45 45 66 50 rubber ear cush- 30 z 20 at 150 V. and 20 mfd at 25 Volts .45 6SF7 65 56 47 92 65 ions, cord and 415D 6SJ7 50 49 50L6GT 65 50 phone plug, in- 600 M ohm V.C. with Switch, 6SK7 55 48 56 51 45 dividually boxed. 21/4" Shaft. Popular Brand $ .42 en. 6SK7GT 60 38 75 67 44 List Price $12.50 each Lots of 12 54.80 6SL7GT 60 62 77 45 39 6SQ7 45 80 40 38 50 BRAND NEW WILLARD 50 Mil Power Transformer 6SQ7GT 50 45 84/6Z4 68 45 Primary 110 V, Secondary 6.3 20.22 VOLT STORAGE 480 V C.T. 6U7G 60 48 117Z3 85 60 Rectifier 5 V, H.V...... $1.95 6V6GT 83 50 12AT6 75 45 BATTERY 6X5GT 55 45 Used in General Electric 12BA6 75 45 456 K.C. IF Coils 7A4 69 40 model #530 charge A PACK & Output, medium sine $ .49 ea. 75 45 Input 7B6 50 40 12BE6 portables. Suitable @ 50 50B5 54 42 for all Farm Radio # 95 l ASGT 60 S s. Individually WRITE, WIRE OR PHONE FOR OUR SPECIAL 1N5GT 60 50 32L7GT 90 80 e t QUANTITY PRICES (ALL TUBES FULLY GUARANTEED) boxed. List Price $8.96 Special each 1625 TRANSMITTING Beam Power, Amplifier. 25% deposit on all orders, balance C.O.D.. Same as 807 except 12.8 volt F.O.B. New York 7top ent medium 7 pin 19e ea. Convert Any Record Player to Wireless -with this Complete Assembled and Tested 2-Tube 1629 Tuning indirator_Trl. 25e ea. (manic Eye) tune Wireless. Phono Oscillator $3.95 LAMP Less Vibes Special SENCO RADIO, Inc. panels ;Mountsy Inch. The red in O9- leh hole on to 4 Jewel assembly is with shutter that controls the Is Standard make 6 Volt prong, $1.19 ST.. N. Y. 7. N. Y. standard miniature bayonet base Auto Vibrator ea. 96 WARREN lmp lacebe from neyO e°e TEL. CORTLANDT 7 -6065 asO palfH rnt coca. Special. while they last S 25

BATTERY SUPERHET USES THREE TUBES (Continued front page 31)

After the wiring has been corn- RESISTORS pleted and everything seems in order, insert the tubes in their respective IS sockets. Be careful not to damage OUR the tiny prongs of the small tubes. Plug in the A- and B- batteries and BUSINESS turn on the set. Now you are ready to to line up the set. It may be better WATT- 2 WATT have it lined up by a serviceman, who 2 WATT -1 has all the necessary equipment, but if this is not possible, the procedure is ANY QUANTITIES as follows: ANY TOLERANCES First connect the set to a good aerial and ground, and open the gang con- Immediate Delivery denser to about 1,600 kc. You may hear The completed receiver. a station, but it will be weak. With an insulated screwdriver, set all four kc and adjust the padding condenser trimmers on top of the i.f. transformers for resonance. It may be necessary to RESISTORS KIT to the point giving maximuni signal go back and touch up the i.f. trimmers strength. The i.f. is 456 kc. Next fully slightly to secure maximum signal $2.05 each close the gang condenser to about 600 strength. Most i.f. transformers are \Assorted and Not Mixed'100 pcs. aligned at the fac- 60 pes. / watt and 40 pcs. 1 watt tory,' so little adjustment should be necessary. A constructor who lacks ELECTRONIC PARTS a signal generator AND COMPONENTS to accept the factory adjustment as approximately correct, and confine LEGRI S COMPANY, Inc. his alignment to 848-850 Amsterdam Avenue the oscillator and New York 25, N. Y. VOLUME TUNING r.f. trimmers and This layout, with slight modifications, can be used with any parts. the padder.-Editor RADIO -CRAFT for JUNE, 1947 71 JOBBERS AND DEALERS CARRY "SHOOTING STARS" TRACKED BY RADIO The (Continued from page 26) exercise a profound influence over the NewELECTRON- frequencies used for FM broadcasting as well as for long -range radio communication and navigation. One way, points out the Bureau of eemake it Standards, in which meteors may affect radio waves is to cause "bursts" on FM channels. Some scientists, notably Dr. J. A. Pierce of Cruft Laboratory, Har- vard University, contend that a major Yourself share of the ionization of the E layer Kit of the ionosphere may be caused by meteors. Up -to- the -minute information on the behavior of the E layer is of basic importance because it governs radio frequencies employed for radio communication and radio navigation. The heat set up by friction as the meteors travel at a great velocity through the atmosphere t' is sufficient to vaporize the solid matter and create a trail of hot ionized gas in the vicinity of the shooting star. This blaze of hot gases gives off a visible glow. These gases and the near -by atmosphere are seemingly highly ionized. "Ionospheric investigations," we are told by the Bureau of Standards, "have shown that ionized gases will reflect radio waves below a given frequency, allowing higher- frequency Waves to pass through. The frequency that will just be reflected by a region of ionized gases is proportional to the square of the density of ions. Because the amount of frictional energy dissipated by a meteor, the hot gases in its trail should be ionized for a brief instant to a much greater extent than is the ionosphere. It is known that SOUND AMPLIFYING SYSTEM the 100 -megacycle radar waves Construction kif pene- contains everything needed -no "extras" fo buy trate the ionosphere. However, the ion- YOU BUILD IT YOURSELF-EASILY -QUICKLY NOTHING TO WEAR OUT ization in 12 page instruction book, fully illustrated -easy except small flashlight the trails of the meteors to-read. easy -lo- battery Mitch lasts for understand. easy-to-follow. - months. should Shows each simple operation step-by-step. be sufficiently intense to reflect IT REALLY WORKS SAFE EASY TO radio waves at least in the region -operated on 110 rolls AC or DC Rouse -AS OPERATE AS YOUR RADIO of cm-rent You and the whole carbon microphone -electronic amplifier and pow- family and your friends will 100 megacycles, a frequency relatively erful dynamic loudspeaker all connected together, haro many hours of fun and entertainment "Talk operate same as big amplifying eysteme. ing over the mike"-holding "Audition' -pick- low in terms of modern radar, but much YOU LEARN ELECTRONIC PRINCIPLES Ing up sound from the radio -piano or any mu- All parte are explained and steal instrument higher than the frequencies used for illustrated. -even staging a "radio" pro - All diagrams are simplified for the novice. gram of your own, right In your own home) long- distance sky -wave radio. For highest quality radio parts, test equipment and radio "Supporting evidence for these con- equipment at lowest prices, write for catalogue to tentions was the fact that interference Exclusive All orders and encountered on the old frequency - RADIO DEALERS inquiries will be modulation broadcasting frequencies in U.S.A. handled by our the form of 'bursts' (parts of pro- Distributors SUPPLY CO. dealers in your grams from long- distance stations inter- 135 Liberty Street, New York, N. Y. vicinity. fering with local station performance) had been found to coincide with the 4 appearance of meteors. Further, it had been reported that during the war radar E MEN! operators tracking V2 rockets had been RCA Redlotron New Ostale A Tungsol Sylvania Q.,T S 24 confused by reflections -from meteors. PEN -OSCIL -LITE Raytheon Nylon errs 5 Tubes, Parte ea each Other radar observers, such as O. P. extrerwply nvenient test oscillatoro for all o dio Equipment rrielpg; ai ge clr write for our latest bulletin, beet. C2 tom 4"eni cicca audio io Ferrell, workirtg in an unofficial ca- 000 mnr(n. u -h -f. outnutfrom zero to 125vr Distributors of RADIO EQUIPMENT at Used by Signal Corsa Write for pacity, in India, had actually made finte noon, CHIEF ELECTRONICS" observations which coincided with the GENERAL TEST EQUIPMENT visual observations of meteors. 88 Argyle Ave. Buffalo 9, N. Y. 104 MAIN STREET, POUGHKEEPSIE, N. Y The Square Deal House e Supply "Out of the research on the effect of such phenomena will come decisions as to which frequencies are the best for the various types of radio services. These Output Transformer (to match 50L6 tube) f .39 Electrolytic Condensera 20/20-150 V .26 recent tests, together with the observa- Three Tube Phono Amplifier, complete ydith tubes, vol. control 8.70 tions with the moon as subject, indicate Tubular Condensera .01 -600 V (per hundred) 3.96 Radio Tubes: 50L6 49 35Z5 42 Standard that radar, besides being a plane locator Radio Tubes: 50115 49 35W4 42 Brand and navigation device, is a valuable tool 6" PM Speaker Alnico #5 Magnet 1,22 ALSO DYNAMIC SPEAKERS. VOLUME CONTROLS. 72 OHM COAXIAL, ETC. SEND FOR LIST for the study of radio -wave propagation BROOKS RADIO DIST. CORP., 80 Vesey St., Dept. A, New York (7), N. Y. and is finding also a place as an instrument in the field of astronomy." 72 RADIO -CRAFT for JUNE. 1947 INTERMITTENT ALARM (Continued from page 34) New Guaranteed "TAB'' Electronic Part 3. Adjust volume control of radio to That's A Buy normal audio output level. TBY NAVY TYPE 4. cLG 20144 VI- LEADING NATIONALLY Connect the Signalometer clips BRATOR POWER ADVERTISED &STORAGE EAT. across primary of output transformer TERY CLG 10020 Precision Wire Wound of radio under The UNIT NEW test. output should MANUALS l RESISTORS drop to below audibility. If necessary, 9/10. W i d t h 93/4 MFGRD BY Amplifiers reduce the input from the signal gen- ELECTRONIC 110% (REST 1 %) erator. aL AB\VILLARD ORATORIES 'Ye% '5% 4000 4300 STORAGE EAT. 1500 2000 - 7500 7950 5. Turn on the TERY CO RATED 5000 5100 17000 20000 Signalometer line 4V 40AH NON 10000 15000 . 100000 300001 SPIT. INCLUDES 50000 75000 166750 47000 switch and set the potentiometer arm BOTTLE OF ACID VIBRAPACK Out 51000 147000 9500001 95000 for greatest resistance. After heating, put Vo tage, fil- 229000 250000t 130000 tered DC 50V & 201000 the warning tone should be heard. 150V 30mo 3V/ "TAB" SPECIAL 3 tar $1.00 6. 375 ma.m I.SV/ 25400 294000 314000 333500 Gradually rotate the Signalometer 200ma. 7.5V/20 353500 400000 462900 422000 Wgt 28 Ms. _ potentiometer arm, decreasing the re- Z plug to. 0.58000 178000 THREE for $1.50 ReineKsr, battery 500000 600000 700000 3 for $1.95 sistance until the warning tone stops. Vat 1 MEGONM 2% y THREE for $2.30 aten, nchgable 10MeS Ten KV MEGOMAX 1RFAI 1.75 The position of from 8V etg bat. 12M09 12KV MEGOMAX MFA 1 1.95 desired sensitivity will IDEAL PORT. WWV OII /o H'mttt11 Sealed Navy Resistors located ABLE SUPPLY 1924) me9cnm 1.69 be close to or slightly beyond 'TAB" SPECIAL WRITE FOR OTHER SIZES FROM STOCK Additional CK-1005 tube Vibrator fusee. 5195 GE Meter 211 BC O. a mWlempp 93.95 this point. BLOWERIIII -AIR 28V-13C GE Meter 21/20 BE Flve amp SF 330 BLOWER - 1 ryÇ Dual 00, CFM.. 113.95 1. ma. MTR. 1 B'C 2.95 CRYSTAL RECTIFIER 1N21. 22. 23. Three for 1.25 5 Amp RF MTR 2 /^ B'C 300 How the circuit works nF NEON Sig -11ík U4 /Gr RE Indicator, 5 fo 1.00 1 Amp RF MTR 2r B'G 3.50 WE DYNAMIC Boaehmaster Mike 20ft cable 7.93 OIL CONDSRS AMATEUR CRYSTALS MTD FOUR FOR 3.00 IOmfd /600WVDC $3.23 2mfd /2000WV 2.15 Operation of the ANTENNA A 20mfd /000WV .. 2.43 3mfdf2000WV 2.50 Signalometer is -27 DUMMY LOAD. CONTAINS Omfd /1600WV .. 2.23 2mfd /3000WV 3.60 N.I. plague RES & VAR CONDSR 150MMF/ 1000WV 2.53 4mfd /3000WV ., 3.00 simple. The small audio voltage which 3500V -IN METAL CASE I.9S VACUUM CONDSR IOOMMF /7600V 4.93 FUSE KIT 300 ASSTD BUSS @ LITTELFUSES 3 3 VACUUM CONDSR SOMME /7500V. 4.50 appears across the secondary of the HARDWARE KIF GOOD ASSMNT ONE POUND 99 VACUUM CONDSR 5OMME /20.000V 6.50 input transformer is amplified by the CHOKE. Ellyn /IOOma rev mend Cased. 2 for 2.20 2mfd /5000 WVDC CD Dyknnol 2 for 14.50 6J5. The rectifier half of the 6SL7 then CHOKE BByn 200mn CASED. 2 for 2.81 amfd /5000WVDC Ea: 2mfd /12500WVDC ...25.00 CHOKE 18 /80 ma cased. 2 for l Oa 2mfd /5500WVDC 58: lmfd /25000WVDC ..75 00 delivers a positive voltage to the grid CHOKE Dual Bmfd /600VAC /2000WVDC GE PYRANOL.... 2 95 CHOKE OHy a /130 ml/ / oh mC°,se.I 2 for ...f 2.30 3mfd /330VAC /1000WVDC. GE PYRANOL . 1.23 of the other half, which is triode -con- TRANSF 115V /60c.3200VCT /780vCT /200 mn 13.95 4mfd /330VAC /IOOOWVDC, CD Dykanol 2 for 2.98 115V /0Oc, 1350VCT /ISOma, .3.3V /5A. 5V /2A 7.30 TRANSF WE CASED 115V /00c. 1540V/240ma nected. This causes a heavy plate cur- 1R 115V /00ey, 7.SVCT /6.SA, 0.3VC1'/3A... 3.75 O8OVCT /2dOme NEW SPECIAL Two for 5.95 AUDIO INTERSTAGE PP /P to PP /G UTC... 1.59 STRODOFLASH CONDSR 32mfd /000VAC /2000 rent to flow, resulting in a large volt- CW3 RECEIVER RELAY RACK MTG 31/2x19'. WVDC GE FOUR SECTION Bmfd 7.93 FIXED TUNED XTAL SUPERISET USES 0E7 RF & STROBO FLASH TRANSF 1540V PM I ISV / 4.95 IF 6KB MIXER, OSC: 6K? IF. 008 DET & Outpt, age drop across the 250,000 -ohm poten- OtN7BFO. 80 RECT. 115V /G0ry Pwr. Case, Coils. Tubes, VI VFO, lete VOLTAGE tiometer in the plate circuit. When the with MANUAL & TUBES. REGULATOR RAYTHEON SPECIAL 513.95 NEW S.C. CASED ADJV. TAPS. INPT set fades, no voltage is delivered to OSCILLOSOOPE KIT 95 -130V; OUTPT 115V 58AMPS ONE 3' INCLUDES regulation /90%PF, WT 20 lbs. 6- Ye the 6J5 for amplification, and the 3BP1 TRANSF 115V /60íy PRI. 375 tri- VCT /110ms.1320V 5V /3A, 'Hx81 /eLx4.%'W. 'TAB" SPECIAL S14.85 2.5V/3.25A, GROMMETS KIT ASSTD 200 for 1.00 ode half of the 6SL7 is cut off, due to 6.3V/2.75A. NEW TUBES SBPI CRAY 5Y3GT RECT. 2V3G REGT CONDENSER KIT SILVER &MICA CONDSRS. UNITS 50 for 2.50 its large cathode resistor (22,000 CHOKE. LOW & HV SUPPLY $16.95 TEST SET CRYSTAL RECTIFIERS CON i ROL KIT 50- 2MEGOHMS POTS: 10 for ohms). The voltage at point P, the po- TS268 /U CHECKS IN21, 23, 23A, 21A, 2.50 o 23B, 21B & OTHERS RESISTOR KIT &IWatt 50to2mog- WITH WESTON 100 ' tentiometer's center arm, rises, and the ENGLISH READING IMA MTR ohms. for 2.50 COM- VITREOUS RESISTOR KIT W.W. 20:or 1.00 neon tube goes into oscillation. PLETE IN CAST METAL CASE & HANDLE NEW GTD with NAVY LOCKET KIT 25 ASSTD OCTAL, MAN. LOCTAL, etc 2.35 The voltage across the potentiometer UAL & SPARE PARTS (G'Cost $125) 15.95 ANTENNA POWER RHEOSTAT KIT 25&50Watt SCM50 /18ít with Ins base 4.95 Six for will be high when the plate current in ANTENNA 300011//AT5 & P1259 .97 4.95 ROTARY SWITCH KIT, SIX for 1.75 the second half of the 6SL7 is low and ANTENNA AN/30B- SWIVELED 30%' .97 ANT Collapsible Telescope I to 9r 1.49 vice versa. Therefore ANT SCM50 /39%' Lone. 12 for 1.00 YEEDER ROOT COUNTER 3 DIGIT .30 it can readily be MICA .004mfd /3000WKO. VEEDER ROOT COUNTER. 4 DIGIT .75 2 for 1.00 BRUSH KIT MOTOR ASSTD 100 for 1.00 seen that loss of gain or fading in the CIRCUIT BREAKERS HEINEMANN 3AMP .97 ADDITIONAL SET OF SPARE TUBES 4.95 CIRCUIT BREAICRS HEINEMANN 10AMP .. 1.29 radio under test produces a higher volt- COILS F3 &CW3 WILCOX RCM 5.1 /IOMC'S 2.79 CRT BREAKER KLIXON OOAMP .69 HI- IMPEDANCE 10.000 ohm HEADSET e lufoB KIT ASSTD WITH BUSHINGS. 25 for $1.25 age across the potentiometer 'which in AS WE 509 with 8 ft molded cord & plug 2.95 OR VARIAC 200CÚ /800Watt NEW 14.95 n. STRIP OOmc's'85DB gain ollErO by GAL- TRANSTAT 88/132V/18.2AMP/I 10V INPT-29.50 INN for GE&WE. CONTAINS 8 /6AKS& NAVY SF.Y turn causes the neon tube to operate I /GALS tubes. compact 2.111O54.S2 }1)^ SYNCHROSCOPE COMPLETE. 59.50 Het 00101 & CO RELAY TIME DELAY 115 /IOAMP /AC&DC. . 1.49 as an audio relaxation Jack -AXIAL inPt Plug 9.49 FOXBORO MECHANICAL RECORDER WITH oscillator in SAME STRIP LESS TUBES 3.49 IIOV /OOey Oraphic pen -chart mechanism AUTOSYN BENDIX AY1 & AY -5 Paired In conjunction with the 32L7 grid circuit. dicaton 18 to 24V AC 60 to 400cy p & CAMS.CASED NEW GTD 5200 COST 39.50 LN Per pair. GTD 3.93 RM53 BEllOTF. CONTROL FOR " The potentiometer arm can be adjust- Constant Impedance ROTARY BEAM COUA..R 3.95 WESTON ANALYZERL OAK CASE 844. 84.0 4.50 ANTENNA STAKE METAL FOR GUY WIRES ENT CORD Hvy DutyERTELPH SJ Male fern plug 18 f4 1.00 ed for various degrees of fading. The 12 for 1.00 .n'RFT AMPNTT'OL 78ST. 25 for 1.50 arm is advanced to the point of oscilla- GYRO SERVO UNIT RCA SOS JAN -Clic NOW Ct'd 61. tion and then reduced slightly below BENDIX 12_.500'0 7.SV /4amp. HORIZONTAL STABIL- plate 1500V/200 wath IZER Rated 140 watts output each 'UHF" this point. Of course, too critical an (G'COST NAVY price & 51000) SCHOOLS COL- Two for 7$5. jittß, S i@7r adjustment might cause - LEGE LABS, AMA- WW1 the Signal TEURS; rXP'S. AN OP- 56.40 PORTUNITY TO HAVE. 2AP1 JAN GTD $2.21. ometer to go into oscillation because A GYRO UNIT FOR 681'1 5CP1 OTD 3.95 YOUR IVORKSHO., Sava & SOCKET GTD 6.95 of slight line voltage variations or ADAPTABLE FOR MITI A SOCKET OTO 2.99 MODF3. PLANES, ROCK. 2C26 CTD IRIHF 2 for 1.50 normal signal generator drift. The sig- ETS & REMOTE MECH. 1625 (8'807) 2 for 1.30 ANISIIS. WGT. 12 845 & SO' KTTS 2 for .95 nal generator should be fairly stable lbs. 10^30Xl0 'TAB" 81$ OrD $2.23. 2 for 39 SPECIAL 514.49 829B/3E29 GTD 2.90 and capable of producing a constant ANTENNA FNT IN- 807 OTO Two for 1.90 UI.ATOR 2'A D & 6 304T1 GTO Two for 7.81 non -varying voltage ROD. CFR. 2 for 3.98 446A/2C40 'Lighthouse tube output. SYLVANIA 1N34 CRYS fa 62.80 Two for 5.00 51.39 fa Two 882 SOCKETS 2 for 52;& 872A SOCKETS The signal generator voltage should for 52.40 fa ANTENNA PARABOLIC B GTDGT 90e: Five for 2.000 be sufficient to allow the neon to start RADAR ASSEMBLY 24^ 955 GTD, Two for 1.45 Din. DRIVE & SELSYN 950, 957, 958A. 059 & SOCKET each .90 or stop by adjusting the potentiometer MOTORS. Wave guide 3B24 HV RECTIFIER 20000V /B0ma 4.95 couplings ROTARY 2V3G JAN HV RECT 10500V /. 2 for 1.50 arm. Too low a voltage from the signal JOINT. Including collar 0/105 Boxed New JAN f& 81c. Five for 3.75 for mtg 360 Deg Hertz 2X2, card generator will result in a constant tone, Control @ adj Vertical SVE 7,03A 368A tAIloF D000rrkstob ENew 5.95 (51200) . .$29.50 eve /70c; 6SN7- 12SA7/SIe: 8SA7/01c: regardless Of the position of the arm. 50MMF /20000V JEN. 6ß80/$1.15 6H6/65c 6J5M/55c: Y3GT- RaIAN,GS VC50/6(0. I 80,41c; 8A4/75c ßA1.5 /81c: 0Cß /51, "TABj' SPÉCIAL 505.11.g. JAN /New GUI eá08 Inch; Two / 1.60 Applications of the instrument 2 for 912.95 351.8. 60L6. 3515, 12507. 123X7.for Two for 1.80 BASS JAN NEW GTD & 95e. Five for .43 and 2i5^/9 deposit Wort C2 -723ÓSeennde foe analog BB COMBINATION SOCKETS, The device has many uses. Radios 99. Sper,alists in International Export. School, Col- TRANSMER. PS,TDOBTDD 7.00 lege & Industrial trade. Moneyback "TAB" Guar. 872A SOCKETS. TRANSFOIC55ER.12.00 can be given a routine fading intermit- lee. TUBES, ' tent and noise test before being returned to the customer, with the full "TABf1 Dept. 6RC, 6 Church St., New York 6, N. Y., U. S. A. "TABf7 assurance that any fading complaints * * * * CORNER CHURCH AND LIBERTY STS., ROOM 100 * * * * (Continued on page 74)

RAD 10 -CRAFT for JUNE, 1947 73 INTERMITTENT ALARM (Continued from page '73) PHONO 5 -TUBE AMPLIFIER tom _;JI SUPERHET Medal + are due to receiving conditions or lo- mlqPa

74 RAD 10 -CRAFT for JUNE, 1947 sabto Tfjirtp-Jibe Nears ago $n igrnsback ¡Publications > TOP B HUGO GERNSBACK Founder GOVERNMENT SURPLUS ELECTRON TUBES Modern Eleetrlee . 1908 Your Your Your Your Electrical Experimenter 1913 Type fledlo News 1949 Cost Type Cost Type Cost Type Cost Science & Invention 1920 3AP1 ... $2.95 12DP7 ... $6.95 5Y3 .43 J.R5GT ... .89 Radio -Craft F929 ShortWave Craft 1930 3BP1 .... 2.95 829B 3.50 50L6 . .69 1S5GT ... .89 Wireless Assoeintlen of America 1908 5BP1 .... 3.95 6Y6G .59 OZ4 .69 6SF5 59c 6AT6 .49 6V6GT 69c Some of the larger libraries In the country still has 5CP1 .... 3.95 6ÁK5 .... .95 .... topiea of ELECTRICAL EXPERIMENTER an Ole for 12AT6 interested reamers. 5FP7 .... 3.95 5U4 .59 ... .49 12SQ7 59c 1N5GT ... .69 89 49c. From June, 1913 ELECTRICAL ExPERI- 7BP7 78 .49 .... 4.95 6SJ7 .49 77 49c MENTER 9LP7 5.95 12A6 .69 Treatise on Wireless Telegraphy .... 12SH7 . .49 39 -44 49e by 'Hugo Gerneback 304TH ... 7.95 6K7 .49 6SS7 - .49 2B7 49c Curious Electrical Rocker How to Construct a One- Quarter KW RADIO RECEIVERS RADIO TRANSMITTER AND RECEIVER Wireless Used. in A -I Condition Complete With Tubes APS -13 Transformer Light weight sir -borne radar ester. radio trans- Recent Developments by the Federal 110- 454 -A; 3-8 mo $3.95 mitter and receiver APS -13; tube complement: 5 -926: 9.6AGS; 1- VR105; 2 -D21; unit I. brand new. ewe - Telegraph Company BC- 453 -A; 190.550 ka $6.95 plate with tubes, the tubes alone are worth C15.00 by Lee de Forest, Ph.D. moro than this LOW PRICE OF ONLY -Y 5.00 BO- 455 -A; 6 -9.1 ma $3.95 How to Construct an Oscillation Trans- GUDE PATH RECEIVER - former by S. W. Hector RADIO TRANSMITTERS R-89/ARN-5 Glide Path Receiver used in the Instrument Lading System covering 3407 Wireless Licenses Be- 457 -A1 4-54 mo $2.95 the frequency range 332 to 535 me; Control by Wireless complete with the following tubes: 7 -8Aß: 1- 128107; $2.95 2- 12SN7; 1 -281)7 and including three crystals Quench BO-453 -AS 5.5-7 mc 6497KC: 6522KC; 6547K0 -t nite ero In $6.95 Spark Gaps A -1 condition for only Aerial Problem MODULATOR UNIT ARMY SURPLUS, principal components of radio BC-406-A $6.95 set - SCR- 274 -N; Includes 2 transmitters. 3 re- SOCKET SUBSTITUTE ceivers. l modulator, 4 dynamotor.. control boa. etc.-Ortglnai cost over $600.00. $24.95 While constructing a signal tracer REMOTE CONTROL BOX NOW -eotnplete probe around a 9006 u.h.f. diode, I found BC-450-A $1.95 available SCR -522 TRANSMITTER AND RECEIVER that the sockets for the tube ARMY AIRCRAFT RECEIVER The standard very -high frequency airborne receiver- were much too large to fit into probe Model BC -946 -B transmitter. 100 to 156 megacycles. 4 crystal -eon- the trolled Broadcast band from 520 to 1500 Kc. Tube comple- channels selected from remote con - G 19 95 that I had in mind. I learned -the hard trol box. In excellent condition -ONLY `V ment: 8- 129K7, 1- 125107, 1 -12A6, 1 -12K9. Do- way it does not pay to solder di- signed for drnamotor operation. but Is easily con- -that verted to 110 or 32 volt operation. Has two LF. SETCHELL CARLSON RADIO RECEIVER rectly to the tube pins. stages and three gang condenser. Cames packed in BC C sealed carton complete with tubes and -I20í An excellent connection $12.95 Designed to receive A -N beam etgnals. 24 -28 Tde. 21.6 that takes up instruction manual, but leas dynamotor. watts. Tubo complement: 14117 or 14A7. RP ampllOer; very little space can be made by wrap- 14117 or 1477. mixer; 14A7 or 14117. IF amplifier: 1FF RADIO RECEIVERS 14117 detector and 1st audio amplifier; 281)7. output ping about six turns of No. 24 bare Signal Carpe, complete with 13 tubes. 195 to 420 Ka 4- high z 4- wide a 115i- Model BC- $9.95 long-wt. 3 lbs. 14 ow. Used-A -I con- $4.95 wire *around a straight piece of No. 18 966- A-only diUon BRAND NEW In original carton. wire. This will form a small coil with MARKER BEACON RECEIVER -AIRCRAFT Complete with tubes $7,95 an inside diameter slightly smaller Complete with 2 tubes and seneltive relay to control external circuits from received signals. The DYNAMOTOR DM 32A than the diameter of a miniature tube receiver to control model.. open doors from $4.95 'Each $1.95 pin. a distance, eta Special RADAR OSCILLOSCOPE coil COMPLETE 4-TUBE INTERPHONE Complete When the is placed over the pin with 27 tube. Including 5 $24.95 of a tube, it makes a firm connection AMPLIFIER Cathode Rey Tube- used -each Comet In en aluminum cabinet, Oyex4%e5V4 Inches without damaging the tubes. Soldered two 12350T and two 12M tubes; aleo Electric RADAR OSCILLOSCOPE ynamotorDwith 28DC Volt Input and 250 V Complete with 29 tubes including 3- connections are made to one end of the DC output at 80 MA. Yours for only .. $7 95 Cathode Ray tube- used-each $24.95 coil. ALL SHIPMENTS F.O.B. CHICAGO. Zoe/a DEPOSIT REQUIRED ON ALL ORDERS CHARLES J. APPLEGATE, DEPT. I) Cl /2212paig7l, Ill. The `ARROW SALES, INC. 59 WEST HUBBARD STREET CHICAGO 10, ILLINOIS HOUSE OF A Telephone: SUPERIOR 5575 MILLION RADIO PARTS ELECTRONIC VOLT -OHMMETER 500 FORMULAS TO SUCCESS 'SPECIAL DEALS 110 VOLTS AC 20 RANGES MANY million dollar firma started with a single formula, for which $1185 0/ 6 / 10/50/100/500/1000 /5000 price. for RADIO DEALERS and v6115 DC and AC. 0_1.000.000,000 have =óá;o less--tried d° tested Ohms In Ms overlapping ranee.. Sen. formulae recipes end pprrotosses for IHvtty: over MILLION OHMS per making things all at te ridic- SERVICEMEN POSTpa Ica OLT on-5 volt range. ulously low Kit No. 85 -11nvy Duty Rlm Drive Complete kit Includes all component iIs ur opportunity to start a parts, tubes. bnutness a Motor and Turntable... List $ 9.95 punched and drilled chassis and beautifully comm.mi with but few douar .ed panel. Easily assembled and wired. and with undreamed Of profits Crystal 1MdaD Ud 6.50 tcapitalo prospect. You e also use these Waterfall Walnut Case Open Lut 4.95 developed during war formulas ln your ó° home to cut . 1 Meg. Vol. Control with Switch List 1.50 by Seiraiéle&Mebane circuit e to the bone. Or tdy and 1 slx -root AO Cord .40 you can nútxtenseeis use Uit completely eliminating of batteriesandaex. w rkehnp to rut costs much instrument tall. 1ÓO0% Kit Total List 573.30 V rte0 Dial wale overman incñe long!. Quit paying out many wdallars in ne edditlOn to performing the usual volOOlun profits to manufacturers. Yale Cost only $11.85 thisie Instrument easily measures these and dealers, make ltagenl SUPFJUIET OSCILLATOR. AVC. AFC, thing 'yourself nnf It's s c ay when !you follow our Kit No. 87-8 Tube Amplifier Kit complete TRUE GRID BIAS AT THE GRID. BIAS CELLS with. with tubes end instnm tione- almnle to build $5.73 cut effecting the circuit. Measures the ct leak. 5001,10 instructions. 66 PAGES. 3200 Kit No. 88-Above amplifier completely wired 0.70' note resistance of INSULATION. TUBES. CON - WORDS IN TEXT M. nrwsER9. IC can no used with a signal generator Send for "500 FORMULAS AND RECIPES" to- Klt No. 89-6 inch P. Speaker ... 1.95 for SIGNAL TRACING. day- Enclose 25e. that's alit You n't be asked Thousands of radio and wund equipment parts for another cent ow or Soldlater. °e oney- and supplies. Tubes, record STERLING ELECTRONIC COMPANY bnk nuarantee. changers. ampli- 106 N. Sierra Bonita Aye.. Dept. 2. Pasadena 4. Calif. fiers, speakers, ota Write for Catalog Na 30 NATIONAL PLANS COMPANY P. O. BOX 28 R, STATION N. New York 2a, N. Y. EQUIPMENT Co. Sweden, with 1,840,000 radios, has the highest rate of radio ownership in - 911-913 Jeffersonerson Ave.. TOLEDO 2.1)H10 Europe. RADIO -CRAFT for JUNE, 1947 75 TUBES ALL TYPES IN STOCK Communications STANDARD BRANDS -R.C.A. SYLVANIA, G. E. ETC. RADIO -CRAFT EQUIPMENT IN THE ANTIPODES Minimum Order - 10 Tubes 10 to 26 - 40% off List Dear Editor: ment is all haywire. When I see the 26 to 100 - 50% off List a signal cost of things like 'scopes in America 101 to 500 - 60 & 30 off List I have enclosed a photo of 601 and over - 60% off List tracer that I constructed from the arti- and compare them with the price we OUR SPECIALS cle in the August, 1946, issue of RADIO - CORNELL- DUBILIER - CONDENSERS CRAFT. Although I made several struc- 20x20 -150V 45 tural alterations to accommodate the IS5 - 124 - 3S4 - 1115 .69 material I had on hand, the instrument 25Y5 - same u 2.535 59 worked perfectly from the first. 6Á1/6 same u 6AX5 69 - As you will see ;from the photo, I 6AK5 - Brand New Western Electric 89 Acorn Tubes 954- 955.950 -951 49 added pockets at each end to dispose of

Hearing Ald Tubes 501Ax to 509AX - 49 the spare leads that are a necessary ad- All American Kit 50L6-35Z5.12SA7- 12SK7- 12S07 2 65 junct to the tracer. Also, instead of Miniature Kit 50B5 - 35W4 - 1213E6 - 1213136 - having a speaker hole cut, I placed 123T6 265 louvres in the front of the cabinet, this OUR OWN BRAND "COMMERCIAL.. TUBE GUARANTEED UNCONDITION. my mind improving the appearance ALLY -100 to Ail Types In Stock 60eo off List Also, the pockets on the MADE BY STANDARD BRAND of the article. MANUFACTURER ends took the high look off the tracer. Write for Cattle, I have been a subscriber to your publication for years now, enrolling through a local agent for three years at a time, COMMERCIAL RADIO and always look forward to the arrival of the book with impatience: My father 36 BRATTLE ST., BOSTON 8, MASS. and myself are in partnership in a radio a.. -,. service business, and have made all our have to pay, I wonder where the dif- test equipment, - including an all -wave ference comes in. signal generator, grid -dip meter, and In conclusion, I would like you to con- Television Receiver Schematics author of the article re- Oct n good picture of how Television Receivers n 1,000 -volt vacuum -tube voltmeter. The gratulate the strurted- simple, easy.. low cost. Prepare yourself efor a and lucrative field. 3 different schematIcs of lending latter is a very elaborate instrument, ferred to, Mr. W. H. Watkins, and show television units-study their construction eat ho -,e or in lab. during your spare time Special 81.85 corn. using a 100 -microampere meter. The him the photo of my version of his eiéte. Also available schematics on aC a45. SCR-522. DC -325. data on it came from an Australian tracer. 3C-375. for 52.25. clls cSCR-274.ek money) order with orderll technical monthly. K. WosxETT, ORDER TODAY! o WRITE NOW! Palmerston, New Zealand TELEVISION ASSOCIATES Way down here the cost of test equip- 30 Church St. Room 533A New York 6. N. Y. -BUILD 15 RADIOS TWO REACTIONS TO THE CRYSTRON CIRCUIT Absolutely No Knowledge of Dear Editor: Dear Editor: Radio Necessary I enjoyed the mendacious adventures Every year about April first, you edi- You Need No Additional Parts or Tools of. Mohammed Ulysses Fips in your tors go off on a binge and come up with April issue. Maybe he's "got something some silly monstrosity of an article such 36 -Page Book Written by Expert Radio In- as the "New Crystron Lapel Radio" structors . . tenches you to Build Radios in there." a Professional Manner. Hearing aids need a perpetual source which appeared in the last issue. why the editors of R -C indulge You will start with a 1 -Tube Receiver -Be- of "high" voltage for the voltage- ampli- Just fore you are done with this Kit you will have fier tubes; and an output tube operat- in such childish horseplay is just too built 11 Receivers. 1 Public Address System much me, and must be for many and 3 Transmitters. ing on the voltage of the filament- supply for Latte,y! That means a very gassy tube of your other readers. I wish the edi- The PROGRESSIVE RADIO KIT without too much distortion of output tors of RADIO -Ca.rr would grow up! is THE ONLY COMPLETE KIT -Contains current, conditions not easy of attain- Why not devote that time, energy and Everything You Need! Inatroc- PRICE lion Book. Metal Chassis, ment. space to a decent article. -an extra ar- Tubes. Radio Parts, Soldering S1 /75 work on that problem, ticle of real consequence-an article ton Iron, Cutter Pliers and Screw- Put Fips to driver. and a million hard -of- hearers will for- some TRUE unusual subject. be was Special FREE OFFER for limited time ever bless him. Please editors, do your age. It Ume only. FREE Electrical and Radio Maybe he can combine the Electret one of you editors who remarked in a Tester with Each Progressive Radio Kit. and crystal earfone with the output previous issue that all radiomen are rig -.11-d an extremely small, strangely "suspect." I don't argue the Progressive Electronics Co.. Dent. RC -2 tube; requiring 22 Hevemeyer St., Brooklyn I1, N., Y. periodic recharge of the Electret, to sup- point. But do not let us ADVERTISE Sirs: Please Bond me tito Progre estro Radio Kit. ply the energy lost in sound -waves from the fact. And that's exadtly what your O Check or Money Order Inclosed. Postage prepaid. 1 the crystal. "FIPS" articles are doing. O C.O.D. I will pay postage. No charge is madé for this invaluable I like you and your mag. O Send for further information. 1 P.S. -(But I suggestion! anyway.) NAME LEE DE FOREST, E. E. JONES, Richmond, ,Va. ADDRESS Guadalajara, Mexico I CITY ZONE STATE 1 NOTE: C.O.D. Outside U.S.A. A.C. CURRENT ANYWHERE! RADIO TUBES With INN B! BIB- MI= n - Stock Plants Generato r ! 50LG.1A7.35Z5,etc. Most Critical Types in rvm totiohhtt ShRIO kind of Brand New, in Sealed Cartons Current s the hlghllnea. Output of FM receivers in 1947 will Sises 500 luaus to 100 KW. IOWA GUARANTEED Also Manufacturer of Rotary be close to 2,000,000 sets, say manufac- Write For Frequency Repairmen and Dealers. Cns` and 0 Vol turers. By the end of December, however, Available List at Trade Discounts D.C. Motors in 1/. 1/e and 4ri RP. A.C. Motors, Ingle is expected that FM receivers will be lu 11/2 and 2 R.P. it RADIO -EXPERTS phare in production at the rate of 5,000,000 as E. 93rd St.. Dept C. Paterson 4. N. 1. KATOLIGHT annually. 120 Rock St., Mankato, Minn. for JUNE, 1947 76 RADIO -CRAFT WOULD YOU LIKE A QUIZ? Dear Editor: I read with much interest your editorial on generalization before specialization, with its accompanying quiz. As one of the many individuals who find pleasure experimenting in all une Speciali branches of science, I observed at once the educational benefits we could obtain from a monthly, students' radio quiz. I PORTABLE PHONOGRAPHS ask not only for myself, but for all those who wish to acquire a more general AC-DC and battery portable phonographs, knowledge of science, that you include complete with 3 tubes, ,amplifier, spring in each issue of RADIO- CRAFT a quiz wound motor, and battery. Ready to play. parallel to that of the March issue. Ideal for beach, picnics, J. B. GREABLE, JR. etc. Only $21.99 Fredericksburg, Texas (Possibly some of our regular authors PORTABLE PHONOGRAPH would like to try their hands at a quiz CARRYING CASE AUTO ANTENNAS or two?Editor) In brown or tan leatherette, built Sturdy, rust proof, 3 section 66" n AVOIDS FILING SYSTEMS in record holder, site I3"xI53/4"x71/ $2.13 Dear Editor: WHILE THEY LAST $4.95 From time to time I read in RADIO- ASSORTED COILS CRAFT about filing systems, keeping ar- DISTRIBUTOR AND SPARK ticles separate from advertising, Package of IO Assorted Coils back- PLUG SUPPRESSORS ing up all articles by advertising, etc. I.F. Antenna R.E. I solve my filing problem quite simply. 18 cents each I cut out the contents page 10 for $1.50 WHILE THEY LAST of every 100 for $12.00 $1.95 issue and keep them all in a loose -leaf per package book. When I want a particular article, A all I have to do is refer to the book with COMPLETE LINE OF TUBES ARE NOW AVAILABLE the contents pages, which gives me the date and page number of the article. Write for Our Latest Catalogue H. SILK, London, England RADIO PARTS COMPANY 612 W. Randolph Dept. "C" Chicago 6, III, Facsimile took another step ahead at the recent national convention of publishers. Some 14 newspaper- owners placed orders for equipment after seeing CHANCELLOR VALUES! it demonstrated, according to reports Your from Radio Inventions, Inc., which ex- Price hibited at the meeting. $33.95 WITH LEARN Burgess Battery EITHER Reran ait, ß42.7u AC- DC- BATTERY PORTABLE DELUXE! 4 tubes plut selenium rectifier. Beautiful elm In a Few Weeks...in the Mated alligator calo. GREAT SHOPS OF COYNE Not a "al/ante-Studs," G?osriide Your You'll learn fast at COYNE, using actual full - Price size equipment. Real shop work plus necessary theory. 48 years' success. 2 great Opportunity fielas -rush coupon for FREE BOOK on course yd.' prefer. For Veterans and non-veterans. Retail ELECTRICITY RADIO value $39.95 Includes Motors, Arma- Learn to build, shoot ture Winding. Indus- trouble on Radios, Pub- trial and House Wiring, lic Address Systems, ALL PURPOSE PHONO COMBINATION Power Plant Work. Sound Pictures. FM, Walnut veneer cabinet- Superheterodyne radio - Maintenance, both AC Television. Training in Silent motor- cystal pickup. Beautiful tonet or DC. Also new field of Electric Refrigeration For quantity prices-write Industrial Electronics. included. Send coupon. Shipped FOB warehouso -20% deposit. bal. COD. Get. big, illustrated book on either course -no obligation. f- FREE BOOK how Tells Coyne helps you. :ADIONIC EQUIPMENT CO. I70 Nassau St, Dept. le& New York 7, N. Y. B. W. COOKE, Dir., FOU, cnoics O) please send me FREE copy of your 1947 COYNE Catalog. 1 understand It has thousands or Items ELECTRICAL 2 GIat Fiefdf Illustrated, described and priced and will be SCHOOL. Dept. A7 -780 great help to me In my b tor ' hard.to 500 S. Pauline St., Chicago 12, 111. RADTONIC find" radio equipment: CHANCELLOR RADIOS. Send FREE BOOK and full details ou course checked: ID ELECTRICITY Ci RADIO EQUIPMENT COMPANY Name NAME Address ADDRESS TRIBUNE TREATER ENTRANCE DEPT. 106. 170 NASSAU ST., N. Y. 7, N. Y. I WORTH 2 -0421. CABLE "CHANSLOR" CITX STATE r City State RADIO -CRAFT for JUNE, 1947 77 ALL STANDARD ADVERTISERS BRANDS INDEX TO Abell Distributing Company 66 National Schools 11 Sop/OBVMSO Allied Radio Corporation 65 The Mayers Company George Brodsky Advertising Newark Electric Company, Inc. '74 OFF Almo Radio Company 46 The Charles Brunelle Company 68 OPA E. L. Brown Advertising Niagara Radio Supply LIST Burke and Wayburne American Sales Company 78 pRICES Olson Radio Warehouse 67 American Television. Inc 13 Agency Jessop Advertising Turner Advertising Opportunity Adlets 63 61 Amplifier Corporation of America Pa -Kette Radio Company 74 Sternfield -God ley Arrow Advertising Arrow Sales, Inc. - 75 OUTPUT TRANSFORMERS for 50 L 6 $ .49 Precision Apparatus Company, 70 Sander Rodkin Advertising Agency Shappe- Wilkes, Inc. ALLIANCE MOTORS with 9" Audel Publishers 79 Progressive Electronics Company 76 turntable 2.95 Grant & Wadsworth, Inc. Thomson, Sava and Valenti, Inc Bell Telephone Labs. Inside Back Cover CRESCENT SPEAKERS, V 5" PM . , .95 N. W. Ayer & Son RADIO SCHOOL DIRECTORY SHURE Belltone Radio & Television Corp. 43 Your Choiee, B.ady, W. H. 56 (See Page 80) PICK -UPS ASTATIe Brady -Parkinson Company American Radio Institute WEBSTER Brooks Radio D'st- ibufing Company 72 Sternfield-Godley, Inc. PORTABLE LEATHERETTE CASE Equity Advertising Baltimore Technical Institute to Burstein -Applebee Company 56 Candler System Company accommodate record changer- F-ank E. Whalen Advertising Company Rand -Ries Advertising A REAL BUY 5.95 Buffalo 'Radio Supply 49 Commercial Radio lest.tute International Advertising Agency Don Martin School of Radio Arts VOLUME CONTROLS with SWITCH Buyers' Syndicate 61 Electronics Institute, Inc. -all ohmage: in stock .50 C. F. Cannon 78 Hollywood Sound Institute M. J. Werner Advertising Nelson Advertising Service ESICO SOLDERING IRONS - Capitol Radio Engineering Institute 45 Lincoln Engineering School 65 Watt 1.95 Henry J. Kaufman & Associates Melville Radio Institute 100 Watt 2.31 Chief Electronics 72 Milwaukee School of Engineering The Graphic Company of Advertising RCA Institutes 25% with order Balanee C.O.D Cleveland Institute of Radio Electronics 15 Send postage with all orders less than $5.00 Kenneth Kolpein Advertising Radcraft Publications 58 Colette Products Company - 58 SALES Rolfe C. Spinning, Inc. Radio Center 53 Claude E. Whipple Advertising Commercial Radio 76 CONSOLIDATEDCOMPANY Radio Corporation of America 6 The Goulston Company, Inc. Thompson Advertising Communications Equipment Co. 8 J. Walter Wholesale Distributors Borough Advertising Agency Radio Dealers Supply Company 72 Burke and Wayburne Dept. RC Ave.. New N. Y. Concord Radio Corporation 51 -I, 768 Amsterdam Vedi 25, Radio Experts 76 E. H. Brown Advertising Agency Radio Kits Company 56 Consolidated Radio Saps Company 78 Corporation 3 Hamburger Agency Cornell- Dubilier Electric Radionic Equipment Company 77 HAM Z Reiss Advertising Republic Advertising Agency SPECIALS Coyne Electrical School 77 Radio Parts Company 77 Parabolic Reflectors. 15 inch spun Alum. Gordon Best Company, Inc. 44 S. Advertising A17ak Fin. Ideal for 1200 MC Coyne School Sydney Lovitt $2.19 ea. Electrical Radio Publications 78 and un Phil Gordon Advertising Agency Original Price $18.00 r $3.95 Dr. Radio Supply and Engineering Company 14 67 ' Deer & Taylor Karl Behr Advertising- Agency Butterfly Tuners -80 to 300 Mc. 800 to Spencer W. Curtiss Advertising G.. 1000 Mc. New in cartons $1.95 9 Radolek Company 69 DeForest's Training Institute Turner Company Alr Trimmers. 10 asstd 91.19 Lauesen & Salomon 44 Douglas Radio Supply Company 57 Ray -Lectron Company Mica Cond- n_ers, 25 asstd.. .98 Malcolm Severance Company Esse Radio Company 12 - Manufacturing Company 55 Phase SLift Condensera-2 sections. split Gary A. Ruben Advertising Reed stator 4 -16 mmfd. silver elated .69 Borg Advertising Agency G & E Equipment Supply Company 70 Reliance Merchandising Company 56 Plate Transformers -Pri. 110V 60 $6.95 Tronnes & Cdlnpany cv. Sec. 1600V CT -250 ma Howard W. Sams and Company, Inc. 5 G & G Genuine Majestic Radio Parts Service 69 -Kynett Klystron Ose. Tube- 2K26/723 AB. oel.75 Bergman-Jarrett Company Aitken Company Company 61 on 8 cm. New in cartons. while they General Cement Mfg. Company 65 Walter L. Schott last. each Sander Rodkin Advertising Agency Ross. Gardner & White 39 Sanco Radio Inc. 71 . Electronic Distributing Company Write for circular General Sternfield -Godley Bass & Weber Company, Inc. Sprague Products Company - 16 General Test Equipment Company n Harry P. Bridge Company AMERICAN SALES CO. Suzanne Hayman Advertising 9. Academy Radio 7 1811 West 47th St. Chlmeo Illinois Globe Distributors 62 Sprayberry of Harry P. B.idge Company. The Goulston Company Company 75 Greenwich Sales Company 68 Sterling Electronic Instruments 69 Weber Associates Superior ,. Bass & Weber Company, Inc. Herbach & Redman. Inc. 61 CANNON -BALL Supreme Publications 41 Philip Klein Advertising Agency H. Teplitz Advertising Circular R -6 cover s Hershel Radio Company 47 Henry Hugh-Allen Sylvania Electric Products, Inc. Inside Front Cover Company NewelfEmmett Company complete line of sensi- 'Highbridga Radio -Television & Appliance Co 60 "TAB" Technical Appa,atus Bldrs 73 -tone, depend- & Wayburne Agency tive, clear Burke Advertising Associates Hudson Specialties 79 Weber able Headsets. Get it. Television Associates 76 70 Illinois Condenser Company 63 Choose the super -qual- Roy D. Zeff and Associates Transyision, Inc. H. J. Gold Company ity Headset you like Instructograph Company 74 College " 4 Turner Advertising Agency Tyler Commercial best. Twenty -five years Wm. F. Finn & Assoc. Company 2 "y International Resistance Variety Electric Company 64 k' sICes headset specialization Falkner and Company, Inc i vY John Arndt Bass & Weber Company b' insures satisfaction. 76 nets 9 Katolight Co. Wright, Incorporated 57 .i.nry. their "'I' Write Klein Ind. Corp. Manuel 70 Advertising. Inc. SternfieldGodley Kay Laboratoriet e 78 C. F. CANNON COMPANY Lafayette Radio 62' X. L. Radio SPRINGWATER. N. Y. Reiss Advertising Agency Leeds Radio Company 66 Weber Associates Get Started in Radio #aadset #aadfuattQts Legri S Company 71 William H. Rankin Advertising IO 1eHOW.TODO -IT" BOOKS Leotone Radio Corporation 55 Get In Altomari Advertising Agency means of those 10catimely boons. clearly ritten, profusely Illus. Lifetime Sound Equipment Company 75 tinted, Contains over 15.000 w rds. need The Miller Agency Company You'll be amazed nt the wealth of Do you McGee Radio Company 52 Information books.boo aExlleepa t for lnree nferece -ide I Westgate Advertising Co. for technical library. Your money back it not satisfied. BINDING POSTS? McMurdo Silver Company 48 PORT with Edward Owen & Company 5 BOOKS for 50c Action La Elfures Contact aarntd connection. P. R. Mallory & Co., Inc. Back Cover gulü Kynett Company 10 BOOKS for $1.00 Manufactured In All Aluminum Type M Aitkin- at 12e ch. ' Magna -Metal Proddcts Company 56 Sent to You Postpaid Bakelite TOP Typo I Equity Advertising Agency J Aluminum No. 1-Now-To Make Four Consols (LeadiRn Term.) at Maritime Switchboard 68 ets To Have Fun Types NP. ALL BRASS- STAtN- (Merle CP Or Electronic & Instrument Co. 42 No. 2 --fow To Make The NOWith Radio LESS STrst.. SPRING PIN. PROVEN Metropolitan 1 NO. To Read Radio Most Al WI 7-How by SPRAY TEST s. NON. Bass & Weber, Co., Inc. t: SA each and 2 PlTube 240SRR. T Murray Hill Books Company 54, 59 No. 3- Alternabne Current No. 8-Radio for Beginnen Manufacturer. an Liberal for Beginners No. 9-Simple Electrical EA. Dealers Harry P. Bridge Advertismg. No. 4-All About Aerials periments National "Plans Institute 75 No. S- aeginners' Radio Di.. No. l0- Television RADIO LABORATORIES Remit by Meek o money order-rellater letter u you X. L. National Radio Institute 1 cash or Clamps. 10. III. r Á 0 420 Weat Chln8S Ave.. Obtain Van Sant, Dugdale & CO.' BABIO PUBLICATIONS, SSA West B'way. New York (7) for JUNE, I 9 4 7 78 RADIO -CRAFT (HARD -TO -GET PARTS\ A MINORITY REPORT? ,POWERFUL ALL -PURPOSE INDUCTION Dear Editor: 1.DAYS FREE MOTOR I am IDEAL FOR EXPERIMENTERS --401 USES and have been for some con- Sturdily constructed to precision siderable time a regular reader of your standards, this self-starting shad Induction motor magazine RADIO- CRAFT. erueñenough u fan If uses.° eess. Somefl of re: Auomaic Tim- My reason for writing to you is my EXAMINATION ing Devices. Current trInterrupters. t Electric Fans. Electric Chime.. Window amazement at the article "Transatlan- Electric Vibrator . Small Grinders. Buffers tic News" by Major Hallows, in the umps. Mechanicals Mod Sirens, and other mell. issue of January of this year. [Is,lomelt.. My job is of Consumes about 15 watts of that managing a radio power and has n eed of 3.000 When neared down, this business in the heart of London, in sturdy unit will constantly or- ate an 18.inch turntable loaded with dead Fleet Street. I have been selling, in- imensions high by 2' 1 " deep: has 4 convenient mounting studs: shaft Is h" lone stalling, and servicing television re- by 3 /16 "v diameter.° and runs In If- aligning. 11. retaining bearings. Designed for 110 .20 voila. 60.80 ceivers since June of last year when the velen. A.C. only. Shp. Wt. 1 lbs. ITEM NO. 147 $LL9 BBC recommenced its transmissions YOUR PRICE 957 after the wartime .break. ULTRA MAGNET Business is of such a magnitude that LIFTS MORE THAN 20 TIMES I am now booking ITS OWN WEIGHT orders for television LITTLE GIANT MAGNET receivers 18 months ahead. The demand Lifts a lbs. easily. Weighs 07.. Made is terrific for receivers of all sizes, from teel. C umr. etc with keeper. World'. ,erimenter'magnet ever the standard 8- x 6 -inch picture to Theft wiii the cold hundreds rat excellent uses for large 12- x 10-inch type. this high llty=rmnnent magnet. Prices range Mcekt'ree Ìn,a" 1ty" Shipp. Wt. NI from £35 plus tax to £150 plus tax, and YOUR PRICE a $ -'S0 the demand is just as great for the smaller -tube type as for the other. GENUINE MICROPHONE TRANSMITTERS Definition is excellent and in my miners taken °from a large opinion is quite good enough for this size telephone mly na fertivoo tta2dry soils' of screen, and no appreciable benefit Can be used on P.A. a vs. tern.. can systems. Inter. would result from the use of 1,000 -line vir. transmissions. milts, hnnne.tn -house RADIO FACTS rnrm.to.fnrm 'phone tines Even with the 8- x 6 -inch type the nito loo through your AND FIGURES ow lal or r viewing dictaphone nick -un. Use- distance (optimum) is found AUDELS RADIOMANS GUIDE-9U Pages, 633Illus- ful replacements on hot. tory- operated rural tele- to be about 5 feet, so that in the small trations, Photos, Wiring Diagrams, 38 Big Chapters, hone lines. covering Radio Theory, Construction, Servicing, includ- THESE ARE GENUINE flats which abound in this town any- TRANSMITTERS. MADE. RV KF.I.I.f1GO. WESTERN ing Important Data on Developments in Television, ELECTRIC AND BpTRO Creme ON. excellent in thing much larger is not required and Electronics and Frequency Modulation, Review. appearance operation. & Testing. offered timeS. °Ship.eWt. 1° lb. neither could it be used in comfort in Questions and Answers, Calculations ITEM No. 180 Highly Endorsed -Indispensable for Ready Reference YOUR PRICE $2.10 most cases. and Home Study. From the transmitting end the art S4 COMPLETE PAY ONLY $1 A MONTH AMAZING BLACK LIGHT!! Step up your own skill with tho facts and figures of Powerful 250 watt U Itra-Yio let Source of the cameraman can be seen to im- your trade. Audcls Mechanics Guides contain Prac- The ita(navlollett tical Inside Trade Information in a handy form. of light prove daily as they get more practice Fully Illustrated and Easy to Understand. Highly a else.crlmental and enter t:,h,,,tent Make, nil eunres- new Endorsed. Check the book you want for 7 days' ent substances brilliantly lump at this and very difficult art. Free Examination. windBrit. No transformers of any In Send Money. needed. Fun n standard conclusion, I would like to point No Nothing to pay postman. lump socket. Dringay out beau- is tiful' opalescent hues In various out that mine not at all an unusual Ì1tó' CUT HERE - -- -Via types f materials. Swell for innate. parties. yy etc.: case and that if Major Hallows would - liehtin. té. Bulb only. Shp. \VL. 2 lbs. like to come and see me, or for that MAIL ORDER ITEM NO. 87 YOUR PRICE $1.95 matter any other television dealer in AUDEL, Publishers, 49W.23St.. iot^f,4"..oYK London, we should be only too pleased Please send me postpaid for FREE EXAMINATION books WESTERN ELECTRIC BREAST MIKE marked U) below. II I decide to keep them 1 agree to light-weight to give him plenty of evidence as to the mall SI In 7 Days on each book ordered and further ft carbmon ml °croph0 ItCweighs mall S1 monthly on each hook untI I have paid pHs.. only 1 Ib. O herwiSe. I win them. Mike th unmeetable demand for television re- punting°ands has 2 -way swivetl- RADIOMANS GUIDE, 914 Pages . . . 64. ingq adjustment that It be ceivers of all descriptions. adjusted to any desired position. ELECTRICIANS EXAMINATIONS, 250 . 1. d I am - her are Z wovenv straps: WIRING DIAGRAMS 210 Pages . . .. . 1. Around Uro otnet ELECTRICAL DICTIONARY 9000 Terms 2. aroundgoes chest. Straps can be Yours sincerely, raped o and off quickly an ELECTRICAL POWER CALCULATIONS,425Pgs. 2. in Tills L. A. LEE, HANDY BOOK OF ELECTRICITY, 1340 Pages 4. a xe llentmentk° an be adapted for home broadcastip or London,_ England ELECTRONIC DEVICES 216 Pages . 2. C mm nication systems. By ELECTRIC LIBRARY, 12 vol., 7000 Pgs., $1.50 vol. diIvatesmounting breastplate, it can be used as desk mike. OIL BURNER GUIDE, 384 Pages . .. 1. rubber 6-foot REFRIGERATION & Air Conditioning, 1280 Pgs. 4. cord and hard nlug. In n u crardlzed UNWANTED INVENTION plate. non- rustabic. Shipping weight. 2 lbs. POWER PLANT ENGINEERS Guide, 1áu0 Pages- 4.. ITEM 152 PUMPS Hydraulics &AirCompressors, 1658 Pgs. 4. YOUR PRICE $1.49 Dear Editor: WELDERS GUIDE 400 Pages 1 BLUE PRINT READING. 416 Pages . . . 2: WATTHOUR METER In the "Why Not" item by Elizabeth SHEET METAL WORKERS Handy Book 388 Pgs. l: Rehm in the RADIO - SHEET METAL PATTERN LAYOUTS, 1100 Pgs. 4. ready óItmmeoÌalelserviee February issue of DesignediRn0Ó AIRCRAFT WORKER, 240 Pages . . 1. f°`le wlÌré Á.C. CRAFT, Miss Rehm says that a telephone MATHEMATICS & CALCULAI IONS, 700 Pgs.. 2.

circuit. Simple2 to tal I? " bfo °° linee which could be used without being held MACHINISTS Handy Book, 1600 Pages . . . 4. 2 wi rmstl lond. MECHANICAL Dictionary, 968 Pages 4 ily hen,-! in the hand "would enable a woman to AUTOMOBILE GUIDE, 1540 Pages 4 wtid á^' éçhlFv°deep. Westing. chat and do some mending at the same DIESEL ENGINE MANUAL, 400 Pages . . 2. nouse. G. E. Ft. Wayne. MARINE ENGINEERS Handy Book, 1280 Pages 4. Snngpmn or other a Ilahlo is precisely time." That probably the , make Sho \Vt. 14 lbs. SHIPFITTERS Handy Book, 272 Pages . 1. MECHANICAL DRAWING COURSE, 160 Pages 1. M N 33 reason the telephone companies have YITEO.OUR PRi,:E $6.95 MECHANICAL DRAWING & DESIGN, 480 Pgs. 2. not dared touch the idea with a ten - MILLWRIGHTS & Mechanics Guide, 1200 Pgs. 4: foot pole. Why, that's dynamite to play CARPENTERS & Builders Guides (4 vols.).. 6. HUDSON SPECIALTIES CO. PLUMBERS & Staamfitters Guides (4 vols.) . 6. 40 West Broadway. Dept. RC -6 -47. New York 7. N. Y. with! Women do enough "visiting" on MASONS & Builders Guides (4 vols.) . . . . 6. t I have circled below of the Items Im MASTER PAINTER 32 2: ordering. 11v full remittance o'fSe` (In- the telephone under present conditions. & DECORATOR, Pgs. clude hipping harge.) IS enclosed (NO C.O.D. GARDENERS & GROWERS GUIDES (4 vols.) 6. ORDERS UNLESS CACCOMPANIED WITH A DEPOSIT.) Imagine the confused state of affairs ENGINEERS and Mechanics Guides OR y deposit off S is enclosed (20,7 Nos. 4, and bred). hip C.O.D. for balance. NO C.O.D. that would exist if they could sit and 1, 2, 3, 5, 6, 7 8 complete , , . 12. ORDERFORORDER THAN SS.00. BE SURE TO IN- Answers on Practical ENGINEERING NGES. mend while gossiping on the phone. We ENGINEERS & FIREMANS EXAMINATIONS . CrcclItmieEel No N wtdwanted: L 147 159 180 87 152 93 men would never get the chance to use it. Bell System, Name Name So please, don't toy with the idea! Address -____ Address LONG- SUFFERING MALE, Plena. Print Clearly (Name withheld at writer's request) Occupation City State Cabin John, Md. [mpor.a by

RADIO -CRAFT for JUNE, 1947 79 BOOK REVIEWS DIRECTIONAL ANTENNAS, by Carl RADIO SCUOOL DIRECTOR E. Smith, E.E. Published by Cleveland Institute of Radio Electronics, .Cleve- land, Ohio. Loose -leaf style, flexible PREPARE NOW FOR SKILLED JOBS IN RADIO AND ELECTRONICS leatherette covers, 81/2 x 11 inches, over 300 pages. Price $15.00 (2 copies $25.00). This book is complete with charts, illustrative patterns, definitions, and equations. INTENSIVE COURSES- Thorough, technical Part I derives the characteristics of reference antennas (spherical, half- education for progressive men and women. wave, quarter -wave, 0.311 vertical, and 1. RADIO TECHNICIAN -The MRI General Licensed by the State of New York others) from those of an "infinitesimal" Course. Includst F.M. & Television. Prepares 1 Etj For FCC Broadcast licenses. radiator. Design equations for field 2. RADIO & TELEVISION SERVICING-Pre- MELVILLE RADIO INSTITUTE shape and strength of the several -types pores For employment as Repairmen on Stand - 45 West 45th St., New York 19, N. Y. are developed" from basic. consideration. ord Broadcast, F.M. IL Television Receivers. E> GENTLEMEN' 3. RADIO COMMUNICATIONS- Prepares for RC -The method is clear and concise, and not FCC Operntors license. Leads to position .cis Send me FREE informatIon too demanding, soit is suitable for tech- Merchant Marine or Flieht Radio Orresr;Cpm- about moeiol Operator. your school. nical student as well as engineer. 4. FUNDAMENTAL RADIO MATHEMATICS - Part II contains over 500 actual field The MRI Preparatory Course. Required pre - Name training for students locking a basic mathe- patterns obtained from twd towers matical background. spaced up to 4 wave lengths and phased MELVILLE RADIO INSTITUTE up to 180 degrees (in steps of 15 de- 45 W. 45th St.. N. Y. 19, BR 9 -5080 grees). Almost 15,000 actual patterns "Tie 4e11 School Maword By R.dro.M.le" L obtained from 3- element arrays are shown in Part III, Each page contains 64 patterns associated with a given 8 rowls F RADIO- TELEVISION TECHNICIAN'S COURSE placement of the radiators, the New Classes starting every 5 weeks. Immediate Enrollment. and 8 columns corresponding to the Women Students invited. phasing (up to 360 degrees in steps of Approved for veterans. 45 of two of the towers rela- Write for Free Bulletin on Cous-ace degrees) tive to the third. A special feature of HOLLYWOOD SOUND INSTITUTE, Inc. these sections is the method used to 1040 N. Kenmore Ave., Los Angeles Dept. B MO 1-2345 designate each 'pattern by a definite number to indicate directly the phase, LEARN orientation, and distance of the towers. LEARN These patterns were originally drawn RADIO by an electro- mechanical calculator TELEVISION IN ONLY 34 WEEKS which was designed, built, and patented Get F. C. C. LICENSEor complete RADIO by the author and his associates. I. Q.

ELECTRONICS RADIO REPAIRING . Modern Completely Equipped TELEVISION -I Year Laboratories Classes Start Every Month MORE COLOR TELEVISION DAY AND EVENING CLASSES Our Organization Engaged in TECHNICAL A new television invention .report- 1 G.I. APPROVED. Veterans TRAINING for 27 Years ed last month from the West Coast may Receive Subsistence BALTIMORE. TECHNICAL INSTITUTE make possible 3 -color television with ENROLL NOW 1425 Eutaw Place, - Bait 17, Md. a single electronic image tube. is George ELECTRONICS INSTITUTE, INC. The system the invention of E. Sleeper, chief engineer of Color 21 Henry Detroit 1, Mich. RCA INSTITUTES, Inc. Television, Inc. Offer thorough training courses in all technical phases of It employs a scanning device which COMMERCIAL RADIO INSTITUTE converts filtered colors into a single A radio training center ¡or Radio and Television DAYS -EVENINGS WEEKLY RATES picture at the transmitter, using a sin- twenty -six years. VETERANS: RCA Institutes Is approved gle electronic picture tube. The images . under G. I. BIII. of Rights

. For Free Catalog Write Dept. in a in RESIDENT COURSES ONLY RC47 are reproduced group black and Broedart, Service. Aeronautical. Television and Marine RCA INSTITUTES, Ines. white on the receiving picture tube and telegraphy clang; Preparatory Course now forming. Liter- A Service of Radio Corporation of America projected through filters and com- ature epee request. Veteran training. Classas now forming 75 VARICK STREET NEW YORK 19. N. Y. then for July LL Entrance examination June" 16. bined optically and projected to a screen Dept C. 38 West Biddle St.. Baltimore 1, Md. as a color picture. A feature of the system, it is pointed SOUND RECORDING SCHOOL out, is that it is receivable on both sets A practical 9 months' course in Sound Fundamental.. equipped for color and those producing Recording, and Sound Transmission measurements; ta n laboratory containing transmission sets. oscillators, only monochrome images. send square wave generator and Intermodulatlon analyzer, and ive"key.' ssages In mode by elegraph other equipment. and radio. Commerce needs thousands of men for jobs. Good pay, adventure, Two complete recording studios ustmllating broadcast. Interesting work. Learn at home quick- morion picture and commercial sound recording, under ly through famous System. the direction of H. M. Tremaine. PRACTICAL rr FRET, Approved for Veterans CANDLER SYSTEM CO. DON MARTIN OF RADIO ARTS TECHNICAL Dept. 3.0. Box 028, Denver 1. Caio., SCHOOL FOR D.S.A. 1655 Cherokee St., Hollywood. CalIf. TRAINING YOU Specialize In Electronics, Radio, Electricity, Refriger- CORRESPONDENCE COURSES IN ation. Heating and Air Conditioning. or Welding. Prepare In one year for position as Technician, or la RADIOdndELECTRICAL. ENGINEERING two additional years_ secure your B. S. Degree ie RADIO ELECTRICAL ENGINEERING with major in Ma- ' ELECTRICAL ENGINEERING ááe eeetrtgrasflelu! TECHNICIAN and RAD ID SERVICE COURSES chinery or Electronics. 1a vor Write for booklet "Career Building" Co'7,"m. Simpli sac, yonc tiersíná m i kl d"' FM and TELEVISION rx""a

Thirty years ago, when all telephone service went Laboratories devised a different kind of filter -a by wire, Bell scientists developed means of sending filter in a waveguide. This filter is a system of dozens of conversations over the same line. electrically resonant cavities formed by walls and partitions. Waves that set This they did by giving to each conversation a up sympathetic vibrations in the cavities pass through; others different carrier frequency; then to separate it from are reflected. the others, they used a device which they had in- In the Bell System, now, single circuits are carry. vented and named-the electric wave filter. ing many conversations at the same time through precision wave -filtering. Today, in microwave telephone systems, the mes- sage- bearing waves pass to and from the antenna in pipes called waveguides. So scientists in Bell BELL TELEPHONE LABORATORIES

EXPLORING AND INVENTING, DEVISING AND PERFECTING, FOR CONTINUED IMPROVEMENTS AND ECONOMIES IN TELEPHONE SERVICE

THE ONLY BOOK OF ITS KIND IN THE WORLD

swers to your questions about vibrator power supply designs... lit Basic Vibrator Structures Examples of Transformer Design Mallory Standard Vibrator Types Design Considerations for Other Applications Vibrator Selection of Correct High Frequency Vibrator Power Power Transformer Supply Chardtteristics Timing Capacitor Typical Vibrator Character' 'c Considerations Data Sheets Design Practices and Methods Power Transformer Design of Interference Elimination Power Supply Circuits General Procedure in Designing Vibrator Transformers Vibrator Inspection Procedures

What do you want to know about vibrators or vibrator power supplies? What kind of problems are you called on to solve? This book gives you the answers to your "why" questions. It will help you to understand the basic principles involved in vibrator power supplies as well as the designing of such equipment. The information brought you in the Mallory Vibrator Data Book is complete, original and easy to understand. Produced by the country's largest makers of vibrators, it shares with you sixteen years of highly specialized power supply experience -and cannot be duplicated anywhere else. It embodies the same kind of "know how" that Mallory has brought you in such outstanding volumes as the Radio Service Encyclopedia, the Mallory Technical Manual and others. Although just published, this great new book -the only one of its kind in the world -is already in large demand. Order now before the first edition runs out. See your Mallory Distributor. Price $1.00.

See Your Mallory Distributor for a free copy of the 1947 Replacement Vibrator Guide

VIBRATORS VIBRAPACKS... P. R. MALLORY 8. CO.. inc. ... CAPACITO. VOLUME CONTROLS ... SWITCHES ... RESISTORS

. FILTERS ... RECTIFIERS ... POWER SUPPLIES. MALLORY !p. U.S. Pot. Off. LAPPROVED PRECISION PRODUCTS P. R. MALLORY & CO. Inc., INDIANAPOLIS. 6, INDIANA'