FM Carrier Stabilization High-Fidelity Amplifier

HUGO GERNSBACK,Edifor

1 R ihid i'eeae - FM Carrier Stabilization 4. High-Fidelity Amplifier Clamping Circuits

THE ANTENNALYZER

SEE PAGE 536

MAY 1946

25c

CANADA 30c "' INSULATED COMPOSITION RESISTORS

1/2 Watt 1 Watt 2 Watt ±10% Tolerance

NOW ... OHMITE makes available to you three Little Devils of exceptional ruggedness and stability! Resistance value and wattage Millions of these tiny molded fixed composition re. are marked on every unit for sistors have been used in critical war equipment and in quick identification. the nation's foremost laboratories. They meet Joint Army - Navy Specification JAN -R -11, including salt water immer- sion cycling and high humidity tests. They can be used at their full wattage ratings at 70 °C (158 °F) ambient temperature. They dissipate heat rapidly -have low noise view level and low voltage coefficient. Enlarged Ratings for maximum continuous RMS voltage drop

are high: 500 volts for the I watt unit -1000 volts for the I watt unit -3500 volts for the 2 watt unit. Units Meet Joint Army -Navy Specification JAN-R -11 have high insulation breakdown voltage. AVAILABLE FROM STOCK IN STANDARD Little Devils are completely sealed and insulated by their wire, RMA 10% TOLERANCE VALUES molded plastic construction. Leads are soft copper hardened immediately adjacent to resistor body -strongly TYPE SIZE RESISTANCE MAXIMUM LIST anchored -and hot solder coated. LENGTH DIAM. RANGE VOLTS PRICE Light, compact, easy to install. All units color coded. 10 Ohms Resistance value and wattage are marked on every unit 1/2 Watt 3/8" 9/4" to 500 13c for quick identification. Available from stock in Standard 22 Meg. RMA values from 10 ohms to 22 megohms. 10 Ohms Devils are ready for any job anywhere. And /6n9 Little ... I Watt Y332" to 1000 17c they're low in cost. Order them now! 22 Meg. 10 Ohms AVAILABLE ONLY THROUGH OHMITE DISTRIBUTORS 2 Watt 116" 56" to 3500 25c 22 Meg. OHMITE MANUFACTURING COMPANY 4896 FLOURNOY STREET, CHICAGO 44, U.S.A.

Send Now for BULLETIN No. 127 Gives complete data and list ae Reefice wed of RMA values. Includes di- mensional drawings and handy color code. Write for it today! HMUTIE RHEOSTATS RESISTORS TAP SWITCHES CHOKES ATTENUATORS BILL, YOU'RE ALWAYS FOOLING 1 I'LL TRY, MARV,e ('IL A PREP LESSON WITH RADIO-- OUR SET WON'T SEE WHAT I CAN 00 SNOWED BILL NOW NE COMP WORK- -WILL YOU FIX IT? WITH IT TONIGHT IILC3E GOCD PLQ7 a M

tvE SEEN STUDYING AT HOME WITH THE SAY, I'VE SEEN THEIR I HELLO, - - GOT YES, NATIONAL RADIO INSTITUTE JUST ADS BUT I NEVER THOUGHT I CAN'T FIND OUT BILL JOE --I'M WHAT'S WRONG A TOUGH ONE STUMPED-- BUT LANDED A SWELL RADIO JOB,TOO LISTEN I COULD LEARN RADIO -- FOR AS TO FIX 7 WHEN ARE ihE CLICKS I SHORT THE GRID AT HOME GUESS I'LL MAKE A SINCE LET ME YOU A RADIO EXPERT? CONNECTIONS... HERE'S YOUR TROUBLE I'LL MAIL FOOL OF MYSELF IN THE FIRST I F STAGE I LEARNED HELP YOU -- A COUPON GC I\' WITH MARY THIS TEST BEFORE I EVEN STARTED FORA FREE THE COURSE, FROM A LESSON RIGHT FREE LESSON THE AWAY N. R. I. SENT ME G

THANKS' I WAS ON, $O GLAD YES, PM CONWNCED NOW SOON I CAN HAVE MY YOU CERTAINLY KNOW JUST BILL-IM OUR WORRIES A TINKERER. A FEW I ASKED YOU TO FIX THAT THE N.R.I. COURSE OW'N FULL-TIME RADIO RADIO. SOUNDS AS ARE OVER I HAVE MONTHS AGO, BEFORE OUR RADIO' IT GOT IS PRACTICAL ANO REPAIR BUSINESS, OR BE GOOD AS THE DAY A GOOD JOB AND I STARTED THE N. R.I. YOU STARTED THINKING THOROUGH. I'LL READY FOR A GOOD JOB I BOUGHT IT! THERE'S A BRIGHT --841T ABOUT RADIO AS A ENROLL NOW. THEN IN A BROA06AST(N6 STATION COURSE N.R.1.'S -SO CAREER, AND NOW FUTURE FOR US 1OAN MAKE EXTRA AVIATION RADIO, POUCE 10 "J METHOD-GP/ES A ' YOU Re GOING AHEAD iN RADIO MONEY FIXING RADIO OR SOME p FELLOW THE PRACTICAL $O FAST! IN SPARE OTHER BL SY RAOIOS KNOWLEDGE AND EUObENCE TIME WHILE RADIO FIELD TO BE A SUCCESSFUL t.a rNrif _"11.4sif LEARNING. RADIO TECHNICIAN

You Build Those and Other Radio Circuito I will send you a Lesson with 6 BIG KITS OF PARTS I SEND TOUS 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 jobl TO SHOW HOW PRACTICAL IT IS TO TRAIN AT HOME FOR SUPERHETERODYNE CIRCUIT (right) Preselec- tor, oscillator-mixer -first de- GOOD JOBS IN RADIO tector, i.f. stage, diode deteo- tor- a.v.c. otage, audio stage. Bring in local and distant I want to give every man who's interested in Radio, stations on this circuit you either professionally or as a hobby, a copy of my build yourself! Leeson, "Radio Receiver Troubles -Their Cause and Remedy'- absolutely FREE! It's a valuable lesson. Study it-keep it-use it- without obligation! And MEASURING INSTRUMENT (above) with it Ill send my 64 -page, illustrated book, "Win you build early in Course. Use it in practi- Rich Rewards in Radio," FREE. It describes many cal Radio work to make EXTRA money. jobs in Radio, tells how N.R.I. Vacuum tube multimeter, measures A.C., fascinating trains you D.C., and R.F. volte, D.C. currents, re- at home in spare time how you get practical experi- sistance, receiver output. enoe with SIX BIG KITS OF RADIO PARTS I send. This "Sample "Lesson will show you why the easy -to- gaasp lessons of the N.R.I. Course have paved the way A. M. SIGNAL -GEN- to good pay for hundreds of other men. I will send it ERATOR (left) build you without obligation , , , MAIL THE COUPON! It yourself! Provide. to amplitude - modulated Future for Trained Men is Bright ìi make EXTRA money axing Radios In signals for test and spare time while learning. 1141 LEARN Radio experimental purposes. Mks, Television, Eleotronhx prlaelples from my easy -to -gram Lessons- Gives valuable practical Tk Radio Repair trueness M booming PRACTICE whet you beam by Nullding real ROW. Thera L good money axing Radler Radio Otreuits with the vEs kits of Radio hi your spars time or own full time ban- parts I send -USE your knowledge to make ned. And trained Radio Techn(clons also EXTRA money while getting ready fer a good find good Fey opporWnitiee in Polies, Avia- run time Radio lob. tion and Marine Radio, In Broadeasttrsg, Radio Manufacturing. Public Address work, Find Out What N.R.I. Can De for YOU etc. Think of the boom coming now that new Rados can be model And think of even MAIL COUPON for Sampio Lesson and MR. I. E. SMITH, President, Dept SEX railer opportunities when Television and 64 -page book. FREE It's packed with tads NATIONAL RADIO INSTITUTE. Washington 9. D. C. runt® are &satiable to the public] Out about opportunities for you. Read the details Into Radio NOW. abort my (tune. Read letters from men I Mall me FREE, without obligation, Sample Leseon and 64 -page book trained. telling what they are doing, earning. about how to win metes. In Radio and Teievlsion- Electrons®. (No Many Beginners Soon Make Si, salesman will roll. Please write í1S Just MAIL COUPON In an envelope or paste plainly.) s Week EXTRA in Spare Time H on a penny postal. -i. E. SMITH. President Dept. SEX. National Radio Institute, Pioneer Age The day reo enroll I start eond1n EX- Home Study Radio School. Washington 9. D. C. TRA MONEY JOB SHEETS to help y w I Name Our 32nd Year of Training Men for Success In Radio Address

City Zme State 14E1 o If you are a war veteran. check here L

RADIO -CRAFT for MAY. 1946 517 The IRC is a commonsense selection service TYPE BT INSULATED METALLIZED and of the controls you need for complete TYPE BW INSULATED WIRE WOUNDS ...the perfect combination. The controls in the IRC Century Line trois for the widest variety of replace- were carefully selected after exhaustive ment needs. study of IRC sales records and of the Best of all, it's not necessary for you requirements of receivers and equip- to actually stock all the 100 Century ment now in use. Line types ! We recommend you main. These studies showed that the num- tain a minimum stock of at least the ber of types previously listed could be 18 Type D Controls listed on page 6 reduced considerably, yet give ade- of IRC Catalog #50- they'll handle quate coverage. But it also proved that 8776 of your replacements -and you reducing the number of available types can depend upon your IRC distributor POWER WIRE WOUNDS... rugged, . moisture proof, completely dependable. to anything less than the 100 now for other types, as required. comprising the Century Line, would And don't forget, only IRC controls make the service engineer's replace- give you such quiet, smooth, depend- ment problem extremely difficult. able performance ! ... because they're On that basis, we established the the only controls with the famous Century Line -not too many, not too IRC Metallized Element, the Five few -but just right to give you Finger Contactor, and the Silent properly designed, easily installed con- Spiral Connector !

YOUR IRC DISTRIBUTOR is the man to know when you need any type of resistor... there is an IRC resist- POWER RHEOSTATS (above), Pre. ance unit for almost every servicing requirement. Ask cisions, Wire Wound Controls, Bleeders, him for your copy of IRC Service Catalog #50. Non -inductive Wire Wounds, etc. (below) -for many service needs. FOR BETTER -THAN -STANDARD DUALITY... Sa 444o

INTERNATIONAL RESISTANCE CO. wan' Dept. 25 -E 401 N. BROAD ST., PHILA. 8, PA. Canadian Licensee: International Resistance Co., Ltd., Toronto

MAKERS OF MORE TYPES OF RESISTANCE UNITS, IN MORE SHAPES, FOR MORE APPLICATIONS, THAN ANY OTHER MANUFACTURER IN THE WORLD.

518 RADIO -CRAFT for MAY, 1946 74e T'fee« 1/todel SIGNAL TRAC E R Simple to operate ... because it has only 0 N E connecting cable - N 0 tuning controls!

Introduced in 1939 -1940 Signal Tracing, the "short -cut" method of Radio Servicing quickly became established as the accepted method of localizing the cause of trouble in defective radio receivers. Most of the pre- war testers (including ours) were bulky requiring a number of connections before the unit was "set for operation" and included a tuned amplifier which had to be "retuned" to compensate for signal shift. The new model CA -11 affords all the advantages offered by the pre -war models and only weighs 5 lbs. and measures 5" x 6" x 7 ". Al- ways ready for immediate use without the necessity of connecting cables, this amazingly versatile unit has NO TUNING CONTROLS. Essentially "Signal Tracing" means following the signal in a radio receiver and using the signal itself as a basis of measurement and as a means of locating the cause of trou-. ble. In the CA -11 the Detector Probe is used to follow the signal from the antenna to the speaker -with relative signal intensity readings available on the scale of the meter which is calibrated to permit constant comparison of signal intensity as the probe is moved to follow the signal through the various stages.

SIMPLE TO 1 * OPERATE-only connecting cable- * COMPLETELY PORTABLE -weighs 5 lbs. and NO TUNING CONTROLS. measures 5 "x6 "x7 ". * HIGHLY SENSITIVE-uses an improved Vacuum * Comparative Signal Intensity readings are indicat- Tube Voltmeter circuit. Tube and resistor- capacity ed directly on the meter as the Detector Probe is network are built into the Detector Probe. moved to follow the Signal from Antenna to Speaker. * Provision is made for insertion of phones.

Please place your order with your regular radio parts jobber. If your local jobber cannot supply you kindly write ¡or a list of jobbers in your state who do distribute our instruments, or send your order directly to us.

The Model CA -11 comes housed in a beautiful hand - rubbed wooden cabinet. Complete with Probe, test leads and instructions. NET PRICE SUPERIOR INSTRUMENTS CO. DEPT. R 227 FULTON STREET NEW YORK 7, N. Y. RADIO -CRAFT for MAY, 1946 519 BUSINESS GETTERS

NOW tsT fIRST ICE ßA O SONO 90 01 OORRAN

With direct mail, you can multiply the prospects who come to your door -bring in new customers to keep your business and your profits steadily growing. Ray- theon Bonded Electronic Technicians have a big story to tell -and have effective self - mailers to tell that story to the public. These direct mail pieces are only a part of the broad program of selling helps made available only to Raytheon Bonded Electronic Technicians. Bonded service means better customer relations. For full details to qualify, see your Raytheon distributor today.

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RADIO RECEIVING TUBE DIVISION NEWTON, MASS. NEW YORK CHICAGO

520 RADIO -CRAFT for MAY, 1946 LET ME TRAIN YOU for RADIO ELECTRONICS& TELEVISION

Supply p FULL RADIO SET for SIMPLIFIED INSTRUCTION - PRACTICE & TESTING

Beginners Learn FAST(

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MAKE GOOD MONEY IN a Business of Your Own ...or a Good Radio Job. FREE BOOKS Mind training through halal practice shouting. 'l'hus. under Sprayberry meth- "How To Read Radio Diagrams and Symbols" with a FULL RADIO SET ... that's od.. you du not have one cent of outlay the interesting way I'll teach you Radio. for manufactured Test Equipment. And its the latest, most practicer Here's a valuable and wonderfully complete new method of all to fix in your head per- Succeed As a Radio -Electron INan book which explains in simple, non -technical English manently the money essential -making My training will give you the broad. how to read and understand any Radio Set Diagram. Radio knowledge. The offer I make you Provides the quick key to analyzing any Radio circuit. here is fundamental principles so necessary as the opportunity of a lifetime. a background. no matter which branch Includes translations of all Radio symbols. This in- I'll prepare you easily and quickly for Radio a wonderful future in the swiftly ex- of you wish to specialize in. I structive volume is yours for the asking- without Pending field of Radio -Electronics IN- make it easy for you to learn Radio Set obligation. Send for it AT ONCE, and along with it CLUDING Radio, Television, Frequency Repair and Installation Work. I teach I will send you another big Modulation and you how to install and repair Electronic Industrial Electronics. Equipment. In fact. you'll be a fully free book, describing in com- Be wise! NOW'S the time to start. RADIO- ELECTRONICTAN, plete, interesting detail my Opportunities ahead are tremendous! No qualified previous experience necessary. equipped with the skill and knowledge Radio -Electronic training. is The to perform efficiently and to make a Sprayberry Course starts right at the wonderful success of yourself. beginning of Radio. You can't get lost. It gets the various subjects across in Read What Graduate Says such a clear, simple way that you un- RUSH derstand and remember. And, you can °One Job Nets About 526.00" master my entire course in your spare time "Since last week I fixed 7 radios, all ... right at home. good- paying jobs. and right now I am COUPON You Do Practical Experiments working on an amplifier system. This There's only one right way to learn job alone will net me about $26.011. for Radio Electronics. You must get it As long as my work keeps coming BOTH through simplified lesson study combined in this way, I have only one word to say and that is. 'Thanks' to my with actual "shop" Practice under the Sprayberry personal guidance of a qualified Radio training. and I am not MMMM Teacher. It's exactly this way that afraid to boast about it. "- ADRIEN Sprayberry trains you supplying BENJAMIN, North Grosvenordale, SPRAYBERRY ACADEMY OF RADIO real Radio parts for learn -by -doing ex- Conn. F. L. Sprayherry, President perience right at home. Thus, you learn Room 2056, Pueblo, Colorado faster, your understanding is clear -cut. DON'T PUT IT OFF! Please rush my FREE copies of "Row to MAKE MONEY In RADIO I'll Show You a New, Fast Way to Test Get the facts about my training - ELECTRONICS and TELEVISION." and "Row to READ RADIO Radio Sets Without Mfg. Equipment now! Take the first important step DIAGRAMS and SYMBOLS." toward the money The very same Radin Parts I supply -making future of with your Course for gaining pre -ex- your dreams. All features are fully Name perience in Radio Repair work may be explained in my big, illustrated adapted through an exclusive Sprayberry FREE Catalog which comes to you Address wiring procedure to serve for complete. along with another valuable FREE fast. accurate Radio Receiver trouble- book you'll be glad to own City (Mall In envelope or pasts 1111 penny post Ord) I >> TL COUPON AT ONCE! :.. aM aMMMMaaaaaalalaaaaaaa.aia P.ADIO -CRAFT for MAY, I946 521 RADIO Contents May, 1946 Volume XVIII No. 8

Editorial: Radio Industry Unfair? by Hugo Gernsback 529 CRAFT Radio- Electronics Monthly Review 530, 531 ANO POPULAR ELECTRONICS Radio Thirty -Five Years Ago 557 Iacornorating SNORT WAVE CRAFT TELEVISION NEWS RADIO i TELEVISION ELECTRONICS

Demonstration Devices by W. K. Allan 532 The RCA Antennalyzer (Cover Feature) 536 FM Carrier Stabilization by I. Queen 537 HUGO GERNSBACK, Editor -in -Chief FRED SHUNAMAN, Managing Editor Clamping Circuits by Jordan McQuay 541 MAJ. M. H. GERNSBACK, Cons'h'g Ed. R. F. SCOTT, Technical Editor I. QUEEN, Editorial Associate ELMER FULLER, Shortwave Editor SERVICING A. PASCALE, Production Manager by Eugene J. Thompson 540 G. ALIQUO, Circulation Manager Visual Radio Alignment JOHN J. LAMSON,Advertising Director Logic -A Repair Tool by Edward J. Bukstein 543 ALFRED STERN, Promotion Manager Radio Data Sheet No. 335: RCA Victor Models 54B1, 5481 -N, 54B2, 54B3 547

IN THE NEXT ISSUE CONSTRUCTION

Modern Television Course A U.H.F. Ham Transceiver by 1. Queen 545 High -Fidelity BC Tuner by Maurice A. Kay 580 Plug -Ugly Eliminator - A 5 -Tube Superheterodyne Hum Level Reduction TEST INSTRUMENTS Published by Raderait Publications, Inc. by Bob White 534 Publication Office: 29 Worthington Street, Multipurpose Tester Springfield 3, Mass. VTVM - by Edward W. Harding 535 Editorial and Advertising Offices: 26 West A Versatile Broadway, Tel. RE 2 -9690. New York 7. N. Y. Chicago Advertising Office: Radio -Craft, 308 W. Washington Street, Suite 1413, Chicago 6, IL. Tel. Randolph 7363. Cleveland Advertising Office: 406 Erie Bldg., SOUND Cleveland, Ohio. Burdette Phillips, Manager. Tel. Main 9645. Superamp With Tuner by Cyril G. Brennan 539 Los Angeles Advertising Office: 606 South Hill Street, Los Angeles 14. Calif. Ralph W. Harker, Manager. Tel. Tucker 1793. San Francisco Advertising Office: 582 Market St., San Francisco 4, Calif. Ralph W. Harker. DEPARTMENTS Manager. Tel. Garfield 2481. RADIO -CRAFT is published monthly on the Edited by Elmer R. Fuller 544 26th of the month preceding that of date. World -Wide Station List Subscription rates: United States and pos- Circuits 546 sessions, Mexico. Central and South American Radio- Electronic countries, 52.60 a year. $4.00 for two years, New Radio -Electronic Devices 548 $6.00 for three years. Canada, $3.00 a year, 56.00 for two years, $7.50 for three years. Try This One 552 All other foreign countries. $3.25 a year, $5.50 for two years, 58.26 for three years. Technotes 554 Special rates for members of the Armed Forces in U. S.. or those addressed by A.P.O. Why Not/ 557 or F.P.O. mail, $2.00. Entered at the poet office at Springfield as second -class matter The Question Box 558 under the Act of March 3. 1879. All communications about subscriptions should be New Radio Patents by I. Queen 562 addressed to: Circulation Manager, Radio- Craft, 29 Worthington St., Springfield 3, Available Radio -Electronic Literature 582 Mass. Communications 583 Notice of CHANGE of ADDRESS should Book Reviews 587 reach us at least one month in advance. When ordering a change, please furnish an address Biographical Portrait Drawings by Constance Joan New stencil impression from a recent wrapper if you can. Address changes cannot be made without the old address as well as the new. $ IIIIIIII1011111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111101111i1III111 Foreign Agents London -Atlas Publishing and Distributing Co., Ltd., 18 Bride Lane, Fleet St.. London, ON THE COVER E.C. 4. Melbourne-McGill's Agency, 179 Elizabeth this month illustrates one of radio's uses St., Australia. Our cover s of electronic apparatus in its own industry. The Text and illustrations of this magazine are RCA Antennalyzer speeds up design of multi -unit copyright and must not be reproduced without permission of the copyright owners. antenna arrays, performing intricate calculations Copyright, 1946, Radcraft Publications. Inc. and throwing the result in graphic form on the RADCRAFT PUBLICATIONS, INC.: screen of the cathode -ray oscilloscope at left. Hugo Gernsback, President Chromatone by Alex Schomburg from RCA photo Mai. M. Harvey Gernsback, Vice Pres. G. Aliquo, Secretary 522 Your copy of the complete, new Concord Catalog is ready! It offers you the latest, greatest selection of guaranteed quality RADIO SETS, PHONO- RADIOS, RADIO PARTS, TEST INSTRUMENTS, BOOKS, TOOLS, AMPLIFIERS AND ACCESSO- RIES, AMATEUR KITS AND SUPPLIES, ELECT- RONIC EQUIPMENT...page after page of post-war - engineered equipment and parts you have long been waiting for. All standard, top -quality lines. Thousands of items. Money- saving prices. And fast service, direct from our two centrally located warehouses in CHI- WE HAVE WHAT YOU WANT! CAGO and ATLANTA. The new Concord Catalog displays the most See the first peacetime line of Concord Radio Sets in comprehensive stock in years! All well- known, new, modern cabinets with a host of post -war fea- standard lines are fully represented. Equipment - tures. See the thrilling MULTIAMP Add-A -Unit accessories -parts for all radio and electronic use ...for building, repair, maintenance...for engineer, Amplifiers, brand new in the field, with sensational amateur, serviceman, soundman, retailer ... com- new flexibility, fidelity, and power -EXCLUSIVE with plete lines of tubes, instruments, tools, speakers, CONCORD. condensers, resistors, relays, etc... PLUS a radio set department offering latest postwar models... PLUS See the vast stock of everything you need in equip- the exciting line of MULTIAMP Add -A -Unit ment and parts...see them in the new, comprehensive Amplifiers offering many innovations in public Concord Catalog, just off the press. address units obtainable only from Concord. Your copy is ready...and it's FREE. Rush coupon today.

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RADIO -CRAFT for MAY, 1946 523 OL' PROF. SQUEEGEE DID THE JOB

y.w... SQUEEGEE

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524 RADIO -CRAFT for MAY, 1946 RADIO 9 Boom INDUS in FM WEI-NE, Broa SOdN POISED t áS1in 1%\ Au r Nr Seen COAS6 MVO BEM NETWORK su O 0. ze44. RADIO ELECTRONICS DeFOREST'S MODERN"A-B-C"wAY a.t qacise

Plan your future the way business men do: Watch the headlines! Pick a field that's "in the nerve'-one with many opportunities for interesting, PROFITABLE EMPLOYMENT or a good chance for establishing a BUSINESS OF YOUR OWN with little capital. Pick a field that offers a variety of interesting opportunities-a field with one of America's most promising futures ... and see how you may MAKE YOUR START TOWARD A PLACE IN THIS FIELD BEFORE JOB COMPETITION BECOMES ACUTE. Write for DeForest's Big, Free, Illustrated Book- "VICTORY FOR YOU." Learn how DeForest's prepares you at home, in your leisure time -without interfering with the work you are now doing -then helps you make your start in the vast BILLION DOLLAR Radio- Electronics field.

You Get EMPLOYMENT SERVICE DeForest's Employment Service offers you the advantage of long and favorable contacts with some of America's foremost Radio- Electronics concerns. "VICTORY FOR YOU" tells you how this Service has helped many to their start in Radio- Electronics. Y ti see how DeForest students and graduates are prepared to win and to hold good paying jobs -how DeForest students start businesses of their own with little, if any, capital. You "LEARN -BY- DOING" DeFOREST'S at Home with Practical Equipment TRAINING IN- iri) WELL -ILLUSTRATED Enjoy CLUDES IN- a "Home Laboratory." DeForest's provides 8 BIG KITS STRUCTION IN LOOSE -LEAF LESSONS OF RADIO ASSEMBLIES AND PARTS to give you valuable MOTION PIC- practical experience DeForest's provides 90 loose -leaf lessons pre- at home. Build modern Radio Receivers and TITRE SOUND pared under Circuits that operate. Build Electric EQUIPMENT. FM the supervision of the man often Eye Devices, an Aviation referred to as the "Father of Radio " Band Receiver, a Public Address System, a Wireless Microphone RADIO AND -Dr. Lee and numerous other fascinating TELEVISION... DeForest, inventor of the Audion Tube, and experiments -in fact, 153 in all, holder of in your spare time at home. NEW colorful over 800 important patents.... ACT Kit Supplement tells PROMPTLY! See how you can learn Radio you about DeForest's "Home Laboratory," and how you the valuable use modern A -B -C DeForest's way -by Radio parta and sub -assemblies to get real practical Reading experience as you learn. ... by Doing ... by Seeing at Home. Mail coupon Now! r,fartll s Home MOVIES Help You Learn FASTER...EASIER DeFOREST'S With DeForest's, you use a genuine DeVRY 16 mm. Mo- tion Picture Projector and exciting training films to help TRAINING INC., Chicago, III. you learn some of Radio's fundamentals FASTER .. . EASIER. SEE what happens inside of many DeFORESTS TRAINING, INC., circuits you are working on. SEE bow electrons 2533 -41 N. Ashland Ave., Dept. RC -C 5 function. SEE how RADIO waves Chicago 14, Illinois, U. S. A. are changed into sound. Get De- Send me both your big book "VICTORY Forest's big, free book! Use it as FOR YOU" and Kit Supplement, showing a key to show you the way to how I may make my start in Radio -Elec- Radio-Electronics job opportuni- tronics with your modern A -B -C home training plan. No obligation. ties of today and tomorrow -the opportunities the headlines tell about. Name Age_ - Address Ipt. SEND FOR FREE BOOK & City Zone State SUPPLEMENT TODAY! If under 16. check bere for apedal If a discharged veteran of World information. War II. check bere. RADIO -CRAFT for MAY, 1946 525 , i I Í i I

; II { L ,: .:.ri,1iii.1L

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i:vu...rs,., .... .:......

A "SEARCHLIGHT" TO they pass between the metal plates the war to produce precise radio beams. their direction of motion is bent in- FOCUS RADIO WAVES This "searchlight" is a milestone in ward so that the energy travels out as many months of inquiry through the In the new microwave radio relay a nearly parallel beam. At the next realms of physics, mathematics and system between New York and Boston, relay point a similar combination of electronics. But how to focus waves is which Bell Laboratories are develop- lens and waveguide, working in re- only one of many problems that Bell ing for the Bell System, giant lenses verse, funnels the energy back into a Telephone Laboratories are working on will shape and aim the wave energy as repeater for amplification and re- to speed microwave transmission. The a searchlight aims a light beam. transmission. goal of this and all Bell Laboratories This unique lens -an array of metal A product of fundamental research research is the same - to keep on mak- plates - receives divergent waves on waveguides, metallic lenses were first ing American telephone service better through a waveguide in the rear. As developed by the Laboratories during and better.

Research and Development in Telephone Telegraphy Television Wire Transmission Radio Aided by Physics Chemistry Acoustics Mathematics Electronics Metallurgy Magnetics Microchemistry Electron Dynamics Spectroscopy Vibration Mechanics Statistics Crystallography Fundamental Studies in Speech and Hearing Lubrication Contact Alloys Electrical Measurements Corrosion and Decay Quality Control Design of Antennas Cable Capacitors Coils Cords Dials Microphones Networks Outside Plant Apparatus Resistors Vacuum Tubes Circuit and System Design for Crossbar Panel Step -by -Step Manual Amplifiers Modulators Oscillators Repeaters Gain Control MAY, 1946 526 RADIO -CRAFT for Grasp the NEW OPPORTUNITIES in RADIO

Modern Radio -F M broadcast and reception - Television - Radar - Industrial Electronics; power, control, communications -new equipment and methods demand new technical ability and experience. Keep up to date with the latest.

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OF TECHNICAL SCHOOLS Mimi Member: NATIONAL HOME STUDY COUNCIL NATIONAL COUNCIL RADIO -CRAFT for MAY, 1946 528 Facts in the ease of Ex- Serviceman vs. Radio Manufacturer

or a number of months now, Rnnio-Caarr has been re- get an agency. We ascertained that this man did not have a ceiving an increasing number of communications from regular store, but was a radio serviceman. He owned a tiny ex- servicemen who write bitter letters indicting the establishment and was strictly in the repair business be- radio industry -from manufacturer to distributor on fore the war. He had never handled radio sets before. His down -accusing it of unfair practices in shutting out serv- location was also against him because he was in a residen- icemen from sharing in the radio business, to which they tial section where there are no stores. For this reason the believe themselves rightfully entitled. radio manufacturer could not grant a dealership to him. Many servicemen state that they sold their own radio This man's credit standing, however, was favorably known, business, then went into the service, only to return and find and the set manufacturer suggested to him that if he could that they are now shut off from their former and other sup- open a new store somewhere near or in a business section, ply sources. Some state that upon returning home, they where there would be a chance of selling quantities of sets, opened a new store, or a new establishment, and since then they would be interested in granting a dealership. From have fought a losing battle to secure representation for this it will be seen how' difficult it is to judge such cases. No some radio set or some radio supplies. two are alike. They wrathfully contend that they meet with no success Then once more, we must come back to what we said edi- and that the usual answer is: "We are extremely sorry, but torially in our November issue -the approach of the ex- we have no open territory at the present time, and cannot serviceman to the manufacturer. open new accounts now." In that issue we stated that no manufacturer will pay Naturally, the men cannot be blamed for voicing their any attention to handwritten letters on blank sheets of extreme annoyance at all this. Many state that they are paper. It is a serious reflection on the ex- serviceman who the holder of a Silver Star, Air Medal, Purple Heart, and has not sufficient pride to get up a good letterhead and at similar decorations, and they feel that the radio industry least keep up appearances. We find that many of the letters has let them down badly. They usually end up by stating: which arrive here -and among these are the most bitter - "What really did we fight the war for ?" are badly composed and are rarely on a decent letterhead. Frequently the letters become extremely caustic, as has No one, therefore, could be surprised that radio manufac- been attested by a number which have been printed in turers or their distributors pay scant attention to such un- RADIo-CR.FZ's "Communications" section. businesslike communications. It is not a simple matter to dispose of these letters with Some of the writers seem to have an idea that RADIO- a blanket answer, because most cases differ and no single CRAFT will always defend the radio manufacturer no matter answer could possibly cover all of the different ones. what he does. That, of course, is not based upon facts. Unfortunately, many of the ex- servicemen who write Unfortunately, it IS true that a number of radio manu- these wrathful letters are not quite fair themselves. In the facturers today have so much business that they can be first place, many of the writers never had a radio set agen- choosy. They usually are understaffed, and if some minor cy before they went to war, and they, therefore, do not clerk gets a letter which he does not consider of sufficient understand the requirements of most radio manufacturers. importance, it may go unanswered. There is first the matter of credit. Radio set manufactur- On the other hand, it must also be admitted that deserv- ers give agencies or dealerships only to those who are finan- ing ex- servicemen, who have a satisfactory rating, have also cially responsible, because the radio manufacturers do not been turned down. Here the fault does not lie with the ex- do a cash business. That means that the customer is usu- serviceman, but with the manufacturer. Unfortunately, too, ally billed on, say 30 or 60 days' credit, as the case may be. there are a number of unpatriotic radio manufacturers in If the store proprietor has no financial rating, the manufac- business, and they deserve severe censure. However, it must turers naturally will not be inclined to extend credit. That be said that if the case of the ex- serviceman is intelligently is true in every line. put before a higher official of a radio manufacturer the ex- The ex- serviceman appreciates the fact that just because serviceman usually will get what he was after. he served his country, and served it well, it does not follow Just writing one letter does not turn the scales of success. that this entitles him to a financial credit if he has no estab- A personal call may be necessary. There is also the tele- lished credit. phone. If the ex- serviceman uses his ingenuity and his re- We believe this to be elementary, but it is often lost sight sourcefulness and can get the attention of a manager or of. We know as a fact that many ex- servicemen, who had assistant manager, we feel certain that his cause will, in been in the business before, and who had a credit standing most cases, get the attention that it deserves. previously, find little difficulty in re- establishing themselves The ex- serviceman must understand that thousands are with their old suppliers. It is when a new man, who had fighting for the same thing that he is, and it is often quite no previous credit standing, comes along that the difficulty impossible for an official to know who is an ex- serviceman begins. and who is not. It is up to him to use sufficient pressure and Not so long ago we investigated a deserving ex- service- resourcefulness to make himself heard. man who had Written in to us in a similar vein as that point- All of this, however, is only half of the story. What good ed out above. He, too, bemoaned the fact that he could not (Continued on page 559)

RADIO -CRAFT for MAY, 1946 529 BROADCASTING VIATHE MOON from one part of the earth to another, described in last month's issue of Radio - lO-ELECTRONI S Craft (page 503) as a Gernsbackian prediction from the year 1927, may become a reality if a plan announced last month by Federal Telephone and Radio Corporation is put into effect. items Interestiisg Scientists of that company consider the communication between FM DX RECORDS were hung up dur- THE MEDAL FOR MERIT was pre- establishment of to Brigadier General distant points on the earth by using ing a contact last month between an sented last month feas- electric power company station in Win- David Sarnoff, RCA's president, by the moon as a reflector "entirely Sig- ible in the not -too- distant future." nipeg, Canada, and an ensign on the Major General H. C. Ingles, Chief the time 200 miles nal Officer of the Army, who represented It is obvious that a transmission USS LC1 1000, at south of Jamaica. President Truman at a presentation emanating from any point, beamed at ceremony held at Radio City, New York. the moon and reflected back to the A long conversation was carried on earth, would strike all points on the side without difficulty over this distance, General Sarnoff was previously of the earth turned towards the moon which is more than 2500 miles. More awarded the Legion of Merit on October with substantially equal intensity. Since remarkable was the fact that the set 11, 1944, for "exceptional meritorious the radio waves strike the receiver from used on shipboard was a low -power conduct in the performance of outstand- above, natural obstacles between the Navy portable with a normal range of ing service" when he was on military transmitter and receiver would have no approximately 15 miles. The Winnipeg service overseas. The present decoration effect. Therefore, the blocking action station was a larger unit used to com- of the curvature of the earth, moun- municate with outlying power stations tains, cities and other obstacles to high as well as with service and repair frequency line -of -sight transmission cars. will be eliminated. "NUCLEAR NONSENSE" was the The range of a powerful television description applied last month to the broadcasting station would be hemi- popular idea "that atomic energy will spheric. Reception of American tele- presently displace all other known vision broadcasts would be equally good sources of power," by H. C. Meyer, throughout South America, Canada president of the Foote Mineral Co. The and Alaska, as well as Europe and a energy is there, he stated, but in the large part of the Pacific. The only re- light of our present knowledge, like the quirement would be that the receiver gold in seawater, it costs more to get be within sight of the moon at the same it out than it is worth. time as the transmitter. More remote A second fallacy attacked by Mr. stations would therefore, have less Meyer was the supposition that secrecy available time for reception, and the concerning atomic power can be main- maximum operating time for any sta- tained by legislative action. "It is utter tion would be 12 hours per day and nonsense for any group or nation to regularly changing. This is a factor with attempt to control the knowledge of which radio and television have not atomic energy developed during the heretofore had to contend. war," he said. "Explosive atoms and The advantages of moon -reflected explosive ideas cannot be imprisoned or transmission would be manifold, espe- outlawed by government edict." Maj. -Gen. H. C. Ingles and.Brig:Gen. Sarnoff. cially those due to the use of very high frequency transmission allowing for a AMATEUR CONTACTS on the mi- was a tribute to his civilian activities as considerable number of channels. At crowave bands were reported last month. head of a great radio corporation. The present the band width of the receiver Amateurs W6BMS and W2LGF, using citation, signed by President Truman, is narrow, thereby limiting the trans- the 5250 to 5650 megacycle band, were said (in part) : Mr. Sarnoff placed the mission to code messages, but probably able to establish contacts over a distance full resources of his company at the dis- future developments will overcome this of 31 miles. This is the first reported posal of the Army whenever needed, re- disadvantage, when higher power trans- use of these bands by anyone other than gardless of the additional burden im- mitters become physically and econom- military and commercial services. posed upon his organization. He en- ically feasible. Fantastic developments Parabolic reflector antennas and Klys- couraged key personnel to enter the may then enter the realm of reality. tron tubes were used in the apparatus. service, and at his direction RCA engineers and technicians rendered special assistance on numerous complex communications problems. He fostered electronic advances which were adapted to military needs with highly beneficial results. The wholehearted spirit of cooperation which Mr. Sarnoff inculcated in his subordinates was of inestima- Signals transmitted ble value to the war effort. from a single point on HAM STATIONS are again being the earth would be re- licensed, it was announced last month flected back from the by the American Radio Relay League. moon in a broad wave The FCC has resumed licensing of am- which would almost ateur radio stations after suspending this service at the outbreak of the war. a hemisphere. cover Prior to Pearl Harbor, there were 60,000 amateur radio station licenses in the United States. It is estimated that this number will increase to 250,000 in the next five years due to the upsurge of interest in amateur radio communication created by the war.

530 RADIO -CRAFT for MAY, 1946 MESONS Produced artificially for the

11111111111 I I I I I 1 11111 I I C I I I 1 1111111111 I I I I I I I I I 1 1111111111111111111 e= first time in a laboratory were announced last month by General Electric engineers. Using X-rays from the company's new 100,000,000 -volt betatron, physicists have succeeded in producing this short -lived particle heretofore to the Technician 1111111111111111NIIIIIIIIIIIIII111111111111111111111111111111111111111111111111111111111111111111111111111111111IIIIIIIic found only far above the earth's surface. The betatron has opened to science PLANE -BORNE TELEVISORS were ten channels an equal number of planes a new energy range, between 40 and 100 valuable as reconnaissance agents in the can transmit ten similar views of a million volts. Pacific struggle, it was revealed last battlefront to screens at a General The meson, hitherto known only month at a Navy demonstration at Headquarters, giving staff officers a through cosmic ray studies, is a particle Anacostia, D. C. Two types of televisors, complete view of the scene. (The pic- considerably more massive than the ture is reminiscent of one pictured in electron, though lighter than the proton. The Experimenter for November, 1924, Mesons are produced in the atmosphere in which Hugo Gernsback envisioned a high above the earth's surface by the six-panel screen, on which Army officers primary cosmic radiation from outer would view television images from each space and last, on the average, but a of the six cardinal directions, mean- few millionths of a second. while directing the plane by radio con- ICEBERG DETECTION trol. Both the with war -de- television and the radio veloped radar and loran will be a fea- control features were actually used dur- ture of the reestablished International ing the later stages of'the recent war, Ice Patrol, it was announced press representatives last month were informed.) by the Coast Guard. The Ice Patrol, Brigadier General Sarnoff, president which maintained a continuous watch of RCA, which developed the system in of the danger areas of the North Atlan- cooperation with the Navy, predicted tic during the iceberg season, was dis- wide peacetime use for the equipment. continued in 1941, though a careful esti- Among other applications, he pointed mate of ice conditions was maintained to: revolutionary television news cover- throughout the war for the benefit of The compact "Block" camera unit out of age over short and long distances from naval vessels and convoys. ifs base. cars, boats, planes and helicopters; safe- The radar will assist in locating ice- guarding the lives of test pilots by re- bergs during periods of low visibility. placing them in experimental planes Loran will give the exact location of a where there is a risk element; trans- berg as soon as discovered. This is im- mission of terrain images to incoming portant. In the past, patrol vessels have planes (or ships) whose pilots might be been fogbound for days. Their position unfamiliar with the region; industrial had to be determined by dead -reckoning applications as watchers where peril and radio - direction - finder bearings. from heat, chemical or radioactive proc- With the use of loran, the patrol ves- esses or other causes would render hu- sel's position can be determined within man observation impossible; and ex- approximately one mile and warning ploration, either over hazardous terrain given of the position of an iceberg or deep beneath the ocean surface. sighted. Loran will also afford a more This latter application is adapted to efficient means of tracking bergs in their recovery of sunken treasure at depths daily movements. too great for divers, or for monitoring A constant patrol of the region will machines working under water. be maintained by aircraft and specially Official Navy Photo equipped cutters. Airplanes of the B -24 Scene on the Potomac televised from a plane. type will be used by the aerial watch. the "Block" and "Ring" systems, were demonstrated. The Block transmitter is a camera weighing only 75 pounds, and is designed for short -distance work. The Ring transmitter is a larger unit, designed for long- distance work, uses two cameras, weighs upward of 500 pounds, and is capable of high -quality television production. In tests over Washington last year, Ring transmitted excellent images over a 200-mile radius from an altitude of 22,500 feet. Even at dusk, it was possible to observe movements of traffic and recognize landmarks without difficulty. Wartime use of the two systems included as "eyes" in remote -controlled planes, flying bombs and "crash" boats; SCENES PICKED UP BY AIRBORNE observation of gunfire, mapmaking and TELEVISION SYSTEM ARE general reconnaissance work; transmis- TRANSMITTED INSTANTANEOUSLY sion of messages, maps and charts, be- IN ANY DIRECTION TO REMOTE tween ships or aircraft. RECEPTION CENTERS Planes transmitted from 6,000 feet views of Baltimore and other scenes (one of which is reproduced here) to Navy and Press representatives at the Naval Air Station in Anacostia. With

RADIO -CRAFT for MAY, 1946 531 By W. K. ALLAN

DEONSTRAT1ON DEVab

A. C. Phase and l'ectors Made lisible

FREQU ENCY modulation or FM is upon the phase of alternating current. famed for staticless, high fidelity Facility in using the concise and con- reception; and has been rapidlyin- venient representation of alternating creasing in importance, promising current by vectors is also a great asset even greater growth in the future. The to student and engineer. discriminator and limiter constitute the Photo A shows a device described by William K. Allan is a Western main differences between amplitude mod- C. V. Drysdale in his book "The Foun- Canadian, making his home in ulation receivers and FM receivers. dations of Alternating Current Theory" Calgary, Alberta. After graduating for draw- from McMaster University, Ham- Discriminator circuits are also part of (Edward Arnold-London), ilton. Ontario, he joined the staff automatic frequency control or a.f.c. ing alternating current or voltage of the Electrical Department of systems, as well as being employed in curves identical to the sine curves ob- Western Canada High School, tak- This import- served experimentally on an oscillo- ing graduate courses in vocational some FM transmitters. education at Colorado State Col- ance of discriminators merits some time scope. The pencil which traces the sine lege. and effort toward understanding their curve is actuated by a Scotch yoke (not During the war years he served action. a Swedish dialect pun) but a slotted as civilian instructor for army, T mechanical linkage driven from a pin navy and air force trainees; at The Foster- Seeley discriminator pro- present is conducting an electronics duces voltage reversals from radio fre- inserted at the tip of an arrow which course for the local International quencies changing at an audible rate, is a radius of a disc rotated by hand. Brotherhood of Electrical Workers. phase relationships. The disc's shaft, after passing through He specializes on odd jobs in elec- by using certain tronics and physics, for example To make these phase relations more a supporting bearing, carries two worms designing and servicing electronic readily understandable the radio fre- from an old dial drive. Dial cable se- musical instruments, constructing quencies are slowed down from millions cured to, and winding around these a portable radiation detector, etc. sec- worms as a capstan, passes around pul- Is on the roster of the Bureau of of cycles to about forty cycles per Technical Personnel; an amateur ond and the modulation or changing leys mounted on the back of uprights with the call VE6KQ; and an of this frequency is slowed down from at each end of the frame, to terminate Associate of the I.R.E. He is audio rates of second to on the sliding board which carries the known to Radio -Craft readers thousands per through a number of articles on a manually controlled change spread paper. Thus as the disc turns the dial electronic organs, the last of which over many seconds. This slowing down cable pulls the sliding board and paper appeared shortly before the war. enables the carrier phase changes to be along to provide the time axis of the studied by stroboscopic illumination. sine curve. Note that the sliding board The voltage changes, resulting from the has most of its sides cut away so that modulation of the carrier frequency, can it bears on the guide grooves only at arrow. Insert the Scotch yoke driving be observed by the unaided eye. its four corners. This is done to reduce pin 'at its tip, and trace a second sine friction. curve, which with the first curve drawn AC VECTOR REPRESENTATION With this device draw a sine curve represents two phases of a three -phase The first requisite in understanding by rotating the wheel. Then draw a alternating current. When two three - discriminator operation is a knowledge second arrow 120 degrees or one third phase sources are connected in additive of the effects of capacity and inductance the way around the disc from the first series, what is the total voltage? Well,

Photo A-The Scotch Yoke for demonstrating alternating current. Below, Fig. I -The three Strobotrons with their power supplies.

uw c

SYNCH- RONOUS MOTOR

RADIO -CRAFT for MAY, 1946 532 draw a zero axis on the paper, and at a number of points along this axis, add the heights of the two sine curves, treating distances below this zero axis as negative. Joining all points so located by a dotted line, results in a new sine curve of the same height half way between the two already drawn. Thus 1 volt when added to 1 volt differing in phase by 120 degrees produces 1 volt. An example of this in practice is found in a 3 -phase delta connection where series addition of 220 and 220 volts results in 220 volts. This answer so laboriously obtained can be found immediately if either arrow is moved only along its own length or diagonally sideways, without changing its direction or length, until its tail is on the point of the other arrow. With a pin at the point of either moved arrow (if moved sideways to the positions shown by the white lines) a sine curve is traced which is the sum of the two curves represented by the arrows, as shown in the photo A. Now a quantity which requires direction as well as magnitude to describe it is called a vector. For example, voltage, velocity and force are vectors whereas mass, density and volume are non -vectors. Thus we have a mechanical proof that alternating voltage may be Photo 6 -The Vectorscope. Left -The revolving arrow. Right-Stroboscope illuminating unit, represented by a vector (arrow) imag- ined to be rotating counterclockwise, denser with with a current of hundreds of stationary at the point of its revolution perpendiculars from its point to amperes lasting a few millionths the starting line, giving instantaneous of a when the a.c. is most positive. If neces- second but producing a very intense sary, stop the motor and adjust the disc values of voltage. BY PRESERVING flash BOTH DIRECTION of light of such extremely brief so this resistor voltage vector will ap- AND MAGNI- duration as to apparently arrest the pear horizontal TUDE, VECTORS MAY BE ADDED with its tip to the right motion of any object illuminated by it. to conform with conventional position. IN PLACE OF THE SINE CURVES The THEY REPRESENT. grid and cathode of a strobotron are connected across: a coil, a resistor, INDUCTANCE AND CAPACITY and a condenser, which are in series THE VECTORSCOPE Next turn on the power supply of the across the 115 -volt 60 -cycle line. See strobotron connected across the induct- Having vector notation clearly in Fig. 1. They are visible behind the (Continued on page 568) mind, let us now put it to use to de- headlamp housing scribe the effect of condensers and coils of the strobotrons on alternating current and voltage. in Photo C. Photo B shows a vectorscope described The synchronous by Lawrence G. Betz in the February motor rotating the 1944 issue of Electronics. It consists of arrow is started an arrow which is a radius of a disc and the screen n % n nDISCRtMIIATOR rotating clockwise 60 revolutions per control of the stro- i ln second. (A set of 2 -1 silent, fiber, auto- botron connected uJ v4uuVU mobile timing gears on an 1800 r.p.m. across the resistor synchronous motor from an obsolete is adjusted until a l mechanical X -ray rectifier is used.) the peak of the al- Three SN4 or 631P1 strobotrons, or ternating current cold- cathode neon -filled tubes, are each sine wave creates connected across a condenser kept just enough voltage charged to just below the strobotron's drop across the re- ionizing voltage, by three independent sistor to fire the d.c. power supplies. A positive charge on strobotron, as is any strobotron's grid causes its neon evidenced by the gas to ionize, so discharging its con- arrow appearing

DISC WITH ARROW 1

.5 135V-, =

Photo C- Demonstration board with stroboscope unit in foreground. Fig. 2 Above, -The discriminator action is similar to that of a frequency- modulation detector, but at very much lower frequencies. RADIO -CRAFT for MAY, 1946 533 By BOB WHITE

MULTIPURPOSE TESTE is Volt, Ohm, Mil und Capacity Meter and Signal Tracer

THE experimenter will find this The socket of the 6B8 tube is fas- vernier dial. The latter unit is used for seven -tube test unit very useful. It tened to a three -foot six -wire shielded measurements. The calibrated knob was incorporates a four -watt audio am- cable. The tube must be shielded if the mounted on top of the cabinet, because plifier with a built -in dynamic 6B8 -G glass type is employed. Resistor in this way the dial reading is not apt speaker; an r.f. test probe; a twin indi- R12 and condenser C15 are mounted on to influence the setting of the "eye." cator electron -ray tube with its separate the probe assembly, but all other parts The 6H6 tube rectifies alternating are located within voltages that are impressed on the elec- the cabinet. Switch tron -ray indicator circuit, so that the Sw2 turns on the image will be clear and sharp. Selector probe. switch Sw4 connects the various testing The 6AF6 -G circuits. When the indicator circuit is twin indicator tube used in conjunction with the signal trac- has both ray -con- ing amplifier, potentiometer R18 regu- trol electrodes tied lates the intensity of the signal affect- together so that ing the indicator. two similar shad- The power supply employs a 5Z4 tube ows are produced. in a conventional full -wave rectifier cir- The tube was cuit. By using jacks J8 and J9 the `B" mounted on a brack- supply can be used to operate or test et with pins 3 and external circuits, if the current require- 7 in a vertical ment is not too large. The neon lamp plane. Switch Sw3 serves as a safety "B" indicator. If the turns on the tar- lamp should go out or glow dimly, the get voltage. The power supply should be turned off be- 6K7 tube - con- cause this would probably indicate a nected as a triode amplifier short circuit or a dangerously heavy -has two is variable bias con- load. If the "B" supply being used power to a circuit to be tested, trols. The 1 -meg- to supply ohm unit (R15), the r.f. probe and audio test prod can which has no dial be used; but it is impractical to use any or calibration, of the other tests simultaneously. All measurements are made with the calibrated dial and 6AF6 tube serves to set the OPERATION OF THE TRACER shadow angle be-. amplifier; and a power supply. The test- fore making measurements. R16, the Signal tracing is a very convenient er will trace a signal from aerial to 750,000-ohm control, is connected to a system for locating a defective stage in speaker of a receiver, and give a com- four -inch 325° calibrated CA precision (Continued on page 564) parative check of signal intensity. It measure voltage, resist- will current, JI ance, and capacity; and also test con- o densers for open and short circuits. red bleck PHONES The test unit was built in a ventilated J3 CIO metal cabinet measuring 12 x 7% x 7 le-rÓ inches. The chassis was made from a WI NC R18 C 11 SJIO 1/s -inch sheet of alloy aluminum measuring 11 x 61 inches. Since the heavy aluminum cannot be bent easily, it was 2 eSW4 supported and fastened by means of R19 i angle irons. 3 It is essential that extreme care be 2 ckred taken in wiring and constructing the red tester. The leads should be well insulat- J2 R212 ed. The jacks that are not grounded to Nck$ 6B8G 6 the chassis can be thoroughly insulated yellow I by fastening them with live- rubber w-j_R22 blue 1 grommets mounted in the panel. black green- 1 brown- 450n Toggle switch Swl permits the audio FIELD amplifier to operate either the speaker rea ^ig_0 000 + or a pair of phones connected to jacks CABLE RII' TCI C2 J10 and Jll. R3 serves as a volume con- N Cl5 RI2 trol and also operates the power sup- R.F. TEST PROBE ply switch. lead from the FUS The grid cap II7V AC 6J7 tube should be shielded to prevent THE SPEAKER SHOWN IS A S" DYNAMIC pick -up of stray noise and hum. The instrument has more tubes than is usual for such a device. The 6B8 -G is in the probe. MAY 1946 534 RADIO -CRAFT for By EDWARD W. 14010k

A VERSATILE IINFA

This Small instrument Measures Volts and Milliamperes

HE average serviceman or experi- meters are needed. Accordingly it was was straight for two or three volts at menter can build an electronic decided to make this electronic voltmeter moderate bias, was not to be found. The voltmeter which will be entirely double as a multi -range milliammeter, best portion of the curve seemed to lie satisfactory at a cost of less than and to forget about incorporating any near a bias point of 2.5 volts, and here ten dollars, plus a few hours of labor. resistance ranges in it. only about a portion half a volt long The conventional approach to elec- The specifications tentatively set up was really linear. In other words, the tronic voltmeters has been to employ called for the cheapest possible unit current passed by the tube would in- two tubes in a push -pull circuit to actu- compatible with reasonable accuracy crease in direct proportion to the volt -. ally drive the meter. The reason given and with a high input resistance. The age impressed on the grid only if the for this is that a push -pull circuit is unit had to be sensitive, a.c. operated, voltage impressed was limited to not needed to provide linear deflection of and use the one -milliampere meter which much more than half a volt. the meter. This is not true-or at least, happened to be available. does not have to be true. A little thought brought the conclusion that a high gm tube with a rectifier unit in the same envelope would K do the job. The 117L7 was selected - 5MEG 4117L7 IK mainly because it was available. The 10MEG 117N7 would a probably be little better, I.5v +2.2 v /n +2.2v though there is not much difference be- RI tween the two. The 117L7 has a gm of 0-I MA 5300 and a plate resistance of about 17,000 ohms when operated with recommended voltages. The rectifier section Fig. I -First experimental voltmeter circuit. will supply 75 milliamperes, which is ample for this purpose. The problem, then, reduced to finding a circuit which would permit applying INPUT IMPEDANCE PROBLEMS as much as a volt across the input, yet To get a high input resistance, it is would still result in linear operation. A necessary to do more than just insert cathode follower circuit is one in which 20 or 30 megohms in the grid circuit of the cathode voltage rises and falls in the tube -especially of a so- called power phase with grid voltage variations. With tube. Under normal operating conditions a cathode resistor of infinite size, it is the beam power amplifier section of the theoretically possible to have the cathode 117L7 should not have a resistance in go just as positive or negative as the its grid circuit greater than a half grid does, In practice, an actual loss in megohm- according to the tube manual. voltage across the cathode resistor-as The reason for this is that some elec- compared to the voltage from grid to trons en route to the plate do strike the ground -is to be expected. This circuit grid and must be permitted to leak off did offer the possibility of staying without biasing the tube negatively an (Continued on page 578) appreciable amount. If the number of electrons flowing from cathode to plate is reduced considerably, naturally there The line- operated portable volt- milliammeter. win be a corresponding reduction in the number that end up on the grid. For this Another current foible is that it is reason it was decided to reduce the plate necessary to precede this push -pull stage voltage applied to the tube from the with still another stage in order to get normal 100 volts or so to about 30 volts. input resistances of reasonably high In addition to that, the heater voltage values. When a rectifier is added to this was reduced somewhat, to about 100 array of tubes, the total adds up to four volts. It is inadvisable to reduce the -and some designers go a step further heater voltage much more than that, and put in a voltage regulator tube or since the rectifier half of the tube needs even two of them! a reasonably normal heater voltage to One final pet peeve is the unvarying supply the nominal 40 milliamperes combination of electronic voltmeter with drawn from it. Under these operating an ohmmeter. Most servicemen and ex- conditions it was found possible to in- perimenters have some sort of a uni- sert a total of ten megohms in the grid versal meter with a satisfactory ohms circuit with no ill effects. With these scale. And two ohmmeters are as useful circuit parameters the tube draws a and necessary as three legs. But almost little less than seven ma, with no signal everyone has need from time to time of voltage applied to the grid. an extra current-reading meter. For in- A little experiment showed that the stance, in reading the plate and grid tube -even with these reduced voltages current in an oscillator, or in balancing -still had a fairly high gm. However, a push -pull stage by getting the current it was disappointingly non-linear. A por- drawn by both tubes equal, two current tion of the characteristic curve which This rear view shows how parts are mounted.

RADIO -CRAFT for MAY, 1946 535 tiatt\EATuiìÈ

THE RCA ANTENNALYZER

Electronic means of designing directional antennas

CONSTRUCTION of directional and even electrically. As early as 1943 after which the resulting pattern is ob- radio antenna systems is a com- an electrical system for calculating the served on the C -R tube, or, when a given plex operation. To concentrate polar diagrams of systems with as many pattern is the goal, the dials may be the power of a station in any as five aerials was described (Electri- twiddled until the proper pattern is ob- given direction, from two to a half- cal Communications, Vol. 21, No. 2, ab- tained. Then the dial settings are re- dozen aerials may be required, each stracted in Radio -Craft August, 1943). corded. These dial settings tell where to transmitting in such phase relation This was non-electronic in action, using locate the powers, as well as the current with each of the others that the sig- a number of Selsyns fixed on a shaft, ratios and phase angles to use. With a nal may be reinforced in the desired their phase position simulating that of little practice, this operation may be direction and cancelled in all others. In the separate aerials in the antenna sys- performed in a few minutes. Metering certain special cases, odd -shaped pat- tem studied. Rotating the whole group devices are included in the Antennaly- terns may be required, as when a sta- with the shaft is equivalent to taking zer so that the ratio of maximum field tion near an irregular seacoast may measurements in a circle of azimuth intensity to r.m.s. field intensity is ob- wish to cover three quadrants, but not around an actual antenna system, the tained. waste power broadcasting over the "radiation pattern" being read on an a.c. One interesting point in connection fourth, occupied only by sea. In at least voltmeter and plotted every few degrees with the use of the Antennalyzer was one other case, it was found desirable around the circle. observed recently. After engineers fa- to avoid blanketing the local stations of miliar with the operation of the instru- a single city with the signals from a ELECTRONIC MEANS SOUGHT was not surprising that engineers ment had established the proper location powerful broadcaster, while maintain- It for an antenna array, the final trace ing signal strength all round (and even began to cast about for electronic means handling complicated calcula- was marked with crayon on the C -R beyond) it. of these tube face. Then the controls were mis- The higher frequencies tions, only incomplete solutions of and Antennalyzer march toward which could be approximated with ear- adjusted the turned has the need and in- who had used accentuated for cruder apparatus. The RCA over to an engineer never creased the of using direc- lier and In six minutes he had ma- possibility was developed to per- the device. tional As frequency is in- Antennalyzer nipulated dials until his on antennas. the major of this work en- the trace creased, it becomes more and more dif- form part oscilloscope coincided with the by electrical means with no mov- the cray- large of pow- tirely on his ficult to generate amounts series of potentiom- markings. Checking dial settings The inherent in the con- ing parts except the with first recorded, was found er. difficulties which change the various para- those it struction of antenna systems, however, eters that he had arrived at an antenna ar- An meters. Through its use, the time re- decrease as dimensions are reduced. an antenna problem has rangement which differed from the orig- system which, broadcast fre- quired to solve can happen antenna at been reduced from several days to a few inal. This under certain cir- quencies, would cover several acres of cumstances. It has been found that when copper, may hours. Fifty-two tubes are used to per- ground and require tons of form the various functions. a rather complicated pattern is desired, be mounted on a single light mast if the where the use of three or more antennas frequency is high enough. Developed specifically for the design are necessary, it is possible to find two Equations for the radiation patterns of directional antennas for broadcast or three configurations which yield the use, the Antennalyzer, in the form il- same pattern. lustrated on the cover, will yield the lI+MB cos (a B+ 411-Los [0-aB]` radiation pattern of directional anten- MEASURING ANTENNA GAIN nas which have as many as five towers One of the uses of the Antennalyzer is or sources of radiation. in measuring the gain of a directional -cos[I-aEI Eaeh source is characterized by four antenna system. When the designer has +MD cos Z 1, the distance from a arrived at the proper pattern he usu- (aD+ [I oDJI parameters: reference point; 2, the azimuth angle ally desires a knowledge of the scale to place on the plot. An exact +ME cos (a E t 2 eos}2[/-eEl) with respect to a base line; 3, the factor amount of current in the antenna, and determination involves a knowledge of 2 =Void) sin B+ B 4, the phase angle of this antenna cur- the mutual resistance existing between +[MB (a a rent. Thus the Antennalyzer has four the antennas. However, rn approximate cos answer may be obtained quickly by + Mc sin (a c + 2s {1-11d) ' potentiometers associated with each antenna, with one exception. One antenna plotting the pattern in polar coordinates the area with a plani- +MD sin D + Zcas [/-erd) is located at the reference point and and measuring (a carries unit current at zero phase. meter. A circle whose area is the same 11)12 is taken as the circle from a single +ME sin la E t cos [i Hence no controls are required with this then antenna. antenna operated with the same power. The Anfennelner obviates problems like this. is displayed di- The radius of this circle is the r.m.s. The radiation pattern polar diagram. on the face of the cathode -ray value of the horizontal of directional antenna systems are well rectly may be ob- tube, either in polar or rectangular co- This approximate relation known, but the arithmetical work nec- tained by measuring the peak value of essary to secure the plot of a radiation ordinates. out of Antenna- The Antenna may be used in two the signal coming the pattern is tedious and time -consuming. lyzer and then measuring the r.m.s. efforts have ways. The dials may be set to corre- It is not surprising that on page 549) been made to do this work mechanically spond to a given antenna configuration (Continued -CRAFT for MAY, 1946 536 RADIO By 1. QUEEN

FM CARRIER STABILIZATION

Part I-The General Electric and Federal Systems

NE of the major problems in can operate up to 500 kc. It is generally Construction of the deflecting grid FM broadcasting has been that used at approximately 230 kc, a fre- system and its connection to the circuit of maintaining the average quency at which it permits a deviation are shown in Figs. 4 and 5. As a con- O carrier frequency while mod- of approximately 175 cycles per second. sequence of the 3 -phase voltages, the ulating it so that it deviates up to Multiplying these values by 432 puts the potentials on grids A, B, and C vary. At 75 kc on either side of its assigned carrier in the new FM band with a some instant, for example, A and B are value. The FCC regulations call for a maximum drift of only 2000 cycles from 6S L7 6S N7 the mean, a very small percentage of the new FM carriers (which operate on approximately 100 mc). Amplitude modulation broadcasting takes advantage of the precise unchang- ing carrier possible with crystal con- X TAL trol. This property is a disadvantage in NETWORK FM. The crystal resists the change of Im which is TO frequency the very basis of the 230 KC 3m system. 230 KC The major electronic and radio manu- t17SCPS facturers have devised ingenious meth- I- ods whereby the high standard of crystal còntrol is combined with frequency OUTPUT modulation techniques so that the mean 99.36 MCI transmitted carrier is maintained with- Ií75 KC I MULTIPLIER X 432. in the rigid requirements while it devi- L_ ates in accordance with the modulation Fig. 2 -Block diagram of the G -E FM circuit which uses the Phasitron frequency modulato to provide the very high fidelity of maximum deviation of 75 kc as re- positive and C negative (Fig. 3 -a). The which the FM is capable. quired. latter grids repel electrons towards the The associated by neutral plane, while B GE PHASITRON METHOD circuits required A and attract the phasitron are not complicated. They them. The periphery of the disk then The type GL -2H21 phasitron tube consist essentially of a crystal oscillator assumes a sine wave pattern (Fig. 6) (Fig 1) is designed to provide wide operating at 230 kc and a circuit to con- which rotates at a velocity determined phase excursions at audio frequency vert the output to 3 -phase 230 kc by the crystal frequency and the num- rates in a crystal -controlled carrier. It (Fig. 2). ber of deflector grids. The tube contains a deflecting grid Anode 1 has 24 holes punched in it, structure of 36 wires, the active portions of which t are horizontal. t y- ¡ r Every third wire is connected together IN B AB B - - , and to a common STANTI b I N base pin. Each STANT2 phase of the 3- phase voltage is connected to one of these base pins. An POTENTIAL OF NEUTRAL PLANE additional deflector A B C A B C A B C AB is connected to another base pin and constitutes the neu- 1 I1 ®1 A11 A1 1 tral plane (Fig. 3), and is grounded through a condens- ,nNVi INSTANT2 er. INSTANT) TIME-, Electrons emit- 3 PHASE VOLTAGE APPLIED TO DEFLECTOR GRID ted from the cath- Fig. 3- Action of three -phase voltage in the deflector grid system. ode are attracted to anodes 1 and 2 (Fig. 4), which are 12 above the disk plane and 12 below it. at positive potential, thus forming a These are shown in Fig. 7. At the in- tapered thin -edge disk. This electron stant when the sine wave pattern is in disk extends from cathode to anode 1 the position shown by the heavy lines, and lies between the neutral plane and all electrons are transmitted through Fig. I -The G -E Phasitron, structural view. the system of wire deflectors. (Continued on following page)

RADIO -CRAFT for MAY, 1946 537 (Continued from previous page) 2H21 the holes to anode 2. One half -cycle 3 PHASE PHASITRON Fig. 5 -How the Pha- later (dotted lines) no current can pass sitron is connected through the holes and anode 2 current 230 KC 230 KC to frequency -modulate FROM ±175 CPS is zero. As the disk rotates the anode KTAL OSC current varies sinusoidally between the crystal's output. these extremes. To modulate this current a coil L is placed over the phasitron (Fig. 8). It AUDIO is supplied with the audio frequency cur- T T rent. The magnetic force on each elec- ? rBt tron moving from the cathode causes the entire disk to rotate in a direction determined by the polarity of the a.f. Fig. 6, left- Pattern of the rotating disk voltage. This effect acts to speed up or of electrons due fo the three -phase voltage. slow down the electrons in the already - rotating disk. Therefore an angular dis- Fig. 7, left, below -Structure of Anode I, placement (at an audio rate) is super- showing maximum and minimum current curves. imposed upon the normal disk rotation Fig. 8, below -How audio -frequency modula- due to the 230 kc, 3 -phase voltage, and results in phase modulation of the car- tion is impressed upon the Phasitron tube. MODULATION rier. A maximum a.fy power of 50 milli - COIL watts is required.

FEDERAL'S FREQUENCY STABILIZATION N9 I ANODE N2I This CFS system is based upon the HOLES PUNCHED IN ANODE de"- Miller effect principle, generally known I Ito radio technicians as a difficulty to be overcome. In this case it is a useful property. As a result of Miller effect, IA s . ' VA the input capacitance of an amplifying MINIMUM CURRENT MAXIMUM CURRENT tube depends upon its amplification and ANODE N22 ANODE N92 upon the difference of phase between a.c. grid and plate voltages. BUFFER 4MC MASTER OSC MILLER EFFECT The modulating unit (Fig. 9) is an 909 8 important part of the circuit. It contains a Hartley coupled oscillator operating C903 C905 R904 at approximately 4 mc. This frequency 4 is divided by 256 in suitable multivibrator circuits so that it lies within the limits of 14.3 -17.6 kc, depending upon u assigned carrier. The frequency of a R901 R902 precise temperature -controlled crystal C9!3 oscillator is similarly divided so that the 904 1 frequency is the same as that just men- TC902 tioned (Fig. 10). The two frequencies so obtained differ in phase. They are passed through TO CENTER FREQ.STABILIZATION UNIT FROM DISCRIMINATOR (Continued on page 549) R F OUTPUT 5+ Fig. 9 -The Federal system employs the well -known Miller effect to stabilize frequency.]

MODULATOR UNIT --I AUDIO PRE- r MILLER MASTER OSC BUFFER ; AUDIO TRANS EMPHASIS ' EFFECT

INPUT 1 RF. 6AB7 tI 12J5 --I 6AB7 OUTPUT 150.600 1 L_

FREQ. FREQ. FREQ. FREQ. OIV.f /2 BUFFER DIV. f/2 BUFFER DIV.f/2 BUFFER DIV.f/2

12SJ7 125N7 125.17 2SN7GT 6AB7 12SN7GT 12SN7GT 3.66 -4.5MC

457.6 -563.2 KC 0.915- 1.126 MC 1.83-2.25 MC

226.15-281.6 KC FREQ. FREQ. LOW PASS BUFFER DIV.f/4 BUFFER DIV.f/4 FILTER

PHASE LOW PASS 57.2 70.4KC 14.3 -17.6 KC BUFFER DISCRIM. FILTER

T I H6 XTAL FREQ. __ FREQ. LOW PASS OSC. DIV.f/2 BUFFER DIV.f/2 FILTER

Fig. 4- Phasitron, cutaway view. I -Cath- ode. 2 -Focus electrode No. I. 3 -Focus 114.4 -140.8 KC 57.2 70.4 KC 14.3 -176KC electrode No. 2. 4- Neutral plane. 5 -Anode the frequency- dividing system. No. 2. 6 -Anode No. I. 7- Deflector grid. Fig. 10 -Block diagram of the stabilizing unit, showing MAY, 1946 538 RADIO -CRAFT for By CyGil. G BRENNAN

SUPERAMP WITH TUNER This High- Fidelity amplifier includes a radio receiver

THIS amplifier, an experimenter's mixers (plus tuner input channel) and the signal amplitude increases, so does consolidation of circuits, has satis- a high gain push -pull amplifier. the potential in the 7M. The plate end factory tone, volume, and a number A double triode -7F7 is used for a two - of the expand- compress control will of useful auxiliary features. The channel mike input, the grid leaks of gain negative potential, while the cath- original model is constructed in a 10x8x each section forming volume controls ode side will be positive, with respect 10 -inch sloping front, metal cabinet, and for the microphones, thus serving as to ground. By moving the control arm on a 9x2x7 -inch chassis; an external efficient mixers. The plates of the 7F7 to the right or left of center, variable speaker is used. Since wiring and com- are coupled together through a one - degrees of positive or negative rectified ponents are close, all coupling condens- megohm resistor, reducing amplifica- voltage will be applied as bias to the ers, A.F. leads, and other sensitive com- tion but preventing any motorboating. 7A7; this rectified voltage increases ponents were shielded thoroughly wher- From here, the a.f. signal travels with signal amplitude, giving desired ever possible. Output is about 20 watts. through a switch on the back of one of compressed or expanded signal from the mike controls, through a coupling the 7A7 plate. Expansion of volume is condenser to the center-tap of the phono used to increase the dynamic volume volume control, the lower side of which range of phonograph records which were is shunted with 50,000 ohms to ground. compressed during the process of recording. Conversely, compression of COMPRESSOR- EXPANDER volume is sometimes desired when using The higher potential side of the phono the amplifier for recording purposes. control, from whence the signal comes, Leaving the 7A7, the signal is ampli- is fed through a coupling condenser to fied by a pentode -amplifier 7C7, then by the grid of a 7A7, used in a volume ex- a triode 7A4. Here an audio transformer pander- compressor circuit, with little is used as coupling to a pair of beam - amplification value. Also, the signal power 6V6's or 6L6's, in push -pull. In- from the phono control is fed to the verse feedback is applied by a 5- megohm grid of a 7C7, which acts as an ampli- resistor in series with a blocking con- fier in the volume "expand- compress" denser between the grid and plate of circuit. each 6L6. Since B -plus leads were long, From the plate of the 7C7, the signal an 8- microfarad condenser was placed passes to one cathode (coupled to the directly at the 6L6 screen grids. A tuner, amplifier and turntable in one unit. opposite plate) of a double-diode recti- An octode or pentode converter is fier 7A6. A center- tapped potentiometer used in the first stage of a superhetero- The circuit consists of: a superhetero- is coupled between the other cathode dyne tuner. The superhet was used be- dyne tuner, a volume compressor -ex- and the opposite plate to it, with the cause of space limitation, in this case. pander, a three -channel input with center -tap grounded (See figure). As (Continued on page 563)

IMEG É N INPUT 6600. 7A7 .02 7C7 ' 7A4 7F7 - so,o r It I. 500.n MEG I MEG Sn I MEG .5MEG COMMON .5MEG GROUND 0-1 î ,M2.01 N Ér 6L6 .01 6H6 ISO MA 5Y3 e

.25 MEG 500 4 6.3v.ToALL FILAMENTS

PHONO MOTOR IÌ1. AC PILOT

OFF o o Ill AC

`TRIPLEPOLE TRIPLE THROW 5 MEG POWER SWITCH

NOTE : I -F = 456 KC; L I,ANT; LZ.OSC.

The Superamp comprises a high- fidelify amplifier and a supe heterodyne tuner. There is a radio, phonograph and two microphone inputs.

RADIO -CRAFT for MAY, 1946 539 VISUAL RADIO ALIGNMENT With a "Wobbulator" and Oscilloscope

SOON the new post -war receivers 180 kc and back again from 180 to 170 will make their appearance in kc, as shown in Fig. 1. dealers' salesrooms throughout There are two general types of FM the country. Many of these models signal generators, or "wobbulators" as will incorporate FM, television, high they are sometimes called. One type em- fidelity audio and other refinements ploys a motor -driven rotating condenser that the public expects in the post -war and the other develops the signal elec- era. Shortly after these receivers find tronically. The rotating- condenser va- their way to the consumer, visual align- riety has become almost obsolete, so Born an electrician's son, Eugene a technique of great J. Thompson early became inter- ment must become little need be said about it. There are ested in electrical subjects. Built interest to servicemen who will have a number of ways in which an FM sig- his first radio while in high school, to service these new sets. nal can be electronically produced. The at the same time attending radio Visual has been used little classes at night. Entered the Col- alignment most popular method is to apply a low lege of the City of New York in in the past. Many servicemen believe it frequency control signal (usually 60 1989, majoring in science. Mean- to be radically different from the out- grid of a reactance tube, while repaired radios for spending cycles) to the money in his spare time. causing the tube to act as a varying Leaving college shortly after inductance across the oscillator tube. Pearl Harbor, Mr. Thompson en- listed as an Aviation Cadet, serv- A schematic diagram of a typical in- ing as navigator and instructor -instrument of this type which is capable charge of Radio Navigation and of operating frequencies from reaching the rank of first lieu- 1.- -170 KC- +-175 KC- *160$01' -175 KC-- *- -170 KC-4 at mean tenant. After leaving service held 415 to 540 kc and band widths of 0 -40 Fig. I -The signal "wobbles" across the i.f. several engineering positions in kc is shown in Fig. 2. In this circuit war plants manufacturing elec.: is is reactance the tronic devices, also writing tech- put meter method. This not the case. the 6J7 the tube and nical manuals for the Army and Equipment necessary for visual align- 6K8 is both a mixer and FM oscillator, Navy. ment consists of the usual alignment the triode section performing the latter Ambition: to become a Psy- - The band width may be reg- chiatrist- starting medical school tools (wands, wrenches, etc.), a cathode function. this fall. Hobby (other than radio) ray oscilloscope, and a frequency -modulated by raising or lowering the am- photography. Member Delta Kappa ulated signal generator. The first two plitude of the 60 -cycle input to the 6J7 Epsilon and the Caduceus Society, items need little or no explanation. The grid by means of Rl. Once this ad- City College. last one, though by no means a recent justment is made, the mean frequency innovation, has not been widely used in is swept back and forth through this the servicing field and will bear some range at a definite linear rate of 60 quency modulated and whose mean fre- explanation. cycles per second by the 6K7 sweep gen- quency is equal to the difference be- A frequency -modulated signal generator. The band width is kept constant tween the two original frequencies. A erator is one whose output varies con- by using a second external variable few examples will make this clear. tinuously in frequency above and below frequency oscillator whose output is not If we had a receiver with an i.f. of a given center frequency at a predeter- modulated, and combining the two sig- 175 kc and a pass band of -.-10 kc, as- mined rate. For example, if the center nals in the pentode section of the 6K8 suming the mean frequency and fre- frequency were 175 kc and the fre- tube as in a standard superheterodyne. quency deviation of OSC. No. 1, which quency deviation were ±5 kc, the fre- The result of combining a frequency is the FM oscillator, were set at 460 kc quency of the output signal generator modulated signal with an unmodulated and i-10 kc respectively, by adjusting would vary continuously from 170 to r.f. signal is a third signal which is f re- (Continued on page 571) 7K16 6J7FREQ.CONTROL C13 VARYING VOLT 25-250V r JPl e 235V AC RI 25K 6K7 .005 PT2 RIZ Hs, C3 SWEEP GENERATOR . i 7 a2 LT _J IOOK E UNUSED CI7, EACH 35- 120ppt RI3 R2,75K UPPER A ND FREQ. , 0- 401(C LOWER 2K F-,o SLOPE LIMIT EQUALIZER SWEEP V2 - - EQUALI NOBBLED (°^' :X WIDTH R3 30K 25l PTI y CONTROL OUTPUT 2A Y 235V

W 235v WAVE -CREST ADJUSTABLE FROM 6K8 C12 FIXED OSC. 6X5 EQUALIZER 415 -540KC r' 01101 = R5 10K R6 74K. R7 ,450 R6 150 r P Ll p \ --i .00005 .000005 i SW 150V 75V 6V 11.SV ¡ ICIS RIS RI4 C16 C6 CI C2 CIO °oa 1 INPUT VI 87 CI 6 C24e8 50K I MEG .4- i--VC X X .5 I I6 L _4_ __J YY 1/4CII .1 SYNCH R4 V4 50K, 17V AC - Fig. 2- Schematic diagram of a fully -electronic frequency-modulated signal generator or "wobbulafor" as used for i.f. alignment. 640 RADIO -CRAFT for MAY, 1946 14Ai etAit

e A.. . e o C q 11

The "1). C. Restorer" Is Applied in 31any Radio Circuits

NY wave form-regardless of is misleading, because the actual d.c. with respect to the frequency of the in- shape or frequency-hasfrequency -has a component present in the output wave put signal. Effect of a long time con- reference level of voltage about of a clamping circuit has nothing what- stant on the input is negligible -under which recurrent alternations or ever to do with any d.c. component which usual operating conditions. But the changes take place. This axis is known may or may not be present in the origi- clamping circuit contains a diode, whose also as the d.c. component of the wave. nal input (signal) wave. action must also be considered. Its value can be established, changed, Clamping circuits may be classified Conduction takes place in a diode only or reduced to zero by electronic action. according to their electronic simplicity when the plate is positive with respect However, when a wave form must be in three general categories: to the cathode, or the cathode is negative entirely above or entirely below a refer- Diode Clamping, with respect to the plate. In the circuit ence level, a process known as clamping Grid or Triode Clamping, of Fig. 2, the diode can conduct only is used. Synchronized Clamping. when its plate is positive with respect A clamping circuit maintains either Simplest clamping circuit (Fig. 2) to ground. the positive extreme or the negative ex- consists of a series condenser C and a When no input signal is present, there is no conduction, but when the Fig. l- Circuit for positive or nega- parallel resistor R, tive clamping of waves to same (zero) followed by a diode signal is applied, the following transient reference level. connected across effect immediately takes place: r J the line. When a On all positive portions of the input non -sinusoidal but wave, the diode conducts and effectively o I recurrent wave is shunts out the resistor R. This action NEGATIVE NEGATIVE in CLAMPING CLAMPING applied to such a results an effective short time con- l AT ZERO CAT POSITIVE circuit, the axis of stant. And the condenser C charges at JIuh REFERENCE) REFERENCEI the original signal a fairly fast rate. is shifted below On all negative NO CLAMPING POSITIVE POSITIVE ground so that pos- portions of the in- PRESENT CLAMPING CLAMPING -going wave, AT ZERO REFI CATNEG.REF.I itive extrem- the diode ties of the wave dputdoes not conduct. treme of a wave form within the limits never appear above the zero reference , The circuit proof a desired reference level of voltage. level (ground). This is known as posi- vides a long time Clamping is not to be confused with tive clamping with a diode. Fig. 2- Positive di- constant for the limiting. A limiter introduces deliberate Regardless of the shape or complexity ode clamping to se- much slower dis - dis' Irtion whenever a wave form exceeds of the input signal, when the recurrent ro reference level. charge of condens- a certain voltage level. A clamping cir- w ;ve form is applied to the condenser er C. The signal during negative por- cuit shifts the axis of a wave form so C the signal loses immediately any d.c. tions is unaffected by action of the cir- that one of its amplitude extremities is component which may have been pres- cuit. This uneven action - considerable not permitted to exceed a certain level ent. The wave then assumes a new ref- charge, but much slower discharge of of voltage. erence level with respect to ground -so condenser C- continues for several cy- There are two kinds of wave clamping that for any one recurrent cycle the area cles, until a charge has been built up on (Fig. 1) according to the appearance of the wave above ground and below condenser C sufficient to shift the signal of the desired result or output wave. ground is equal. In other words, the sig- wave form below the zero axis. This un- Positive clamping means that the posi- nal shifts in such a manner that the even action is shown in Fig. 3A. tive extremities of a wave are held to a zero reference (ground) appears Such a transient effect takes place certain reference level with respect to throukh the average center of the wave. when a signal is first applied to the zero or ground. Negative clamping The input signal has suffered no clamping circuit. Thereafter, the con- means that the negative extremities are change of phase or shape by this initial denser remains charged and the output held to a certain reference level. action. The wave mere- REFERENCE LEVEL In electronics work the most common ly has been shifted with +E reference axis is ground, or zero. Clamp- respect to a new refer- ing is usually accomplished with respect ence level: ground, or o to that reference. zero. -E In some radar, television, and indus- The wave is then ap- INPUT INPUT trial electronic circuits the reference plied directly to the ac- level normally may be as much as sev- tual clamping circuit. +E CHARGING EFFECT OF CONDENSER C eral thousand volts, and either plus or Condenser C is REFERENCE LEVEL minus in polarity. When such signal charged and discharged voltages pass through a coupling con- by the input signal at denser at any point in the circuit, the a rate dependent upon d.c. component is lost. This is often un- (1) the recurrent fre- -2E IJLJ...Li.. desirable. quency of the input OUTPUT OUTPUT However, the old reference level can wave, (2) the value of A:TRANSIENT EFFECT B:STEADY-STATE EFFECT Action circuit shown in Fig. 2, Le a Fig. 3- of positive clamping reestablished -or new axis estab- the condenser, and (3) with transient and steady-state effects. lished-by the use of suitable clamping the value of the resist- circuits. ance in the circuit. wave form is maintained so that posi- Since a d.c. component is effectively Values of the condenser C and "re - tive extremities do not exceed the zero restored by such circuits, they are some- sistor R are selected so that their prod- reference level. This steady -state effect times called d.c. restorers. But this name uct (RC) provides a long time constant, (Continued on following page)

RADIO -CRAFT for MAY. 1946 541 (Fig. 3B) continues until the input is is approximately equal to the fixed tubes. This method of clamping is known changed or interrupted. voltage E (Fig. 4). as grid clamping. When a triode is used, Care must be taken in the selection of Occasionally a wave form is required this method is also known as triode values of R and C, to obtain a sufficiently to be clamped above the zero reference clamping. long time constant. Actual values will, level. When the negative extremities of If any element of a vacuum tube is of course, depend upon the recurrent a wave's amplitude are held at or above made positive with respect to the cath- frequency of the input wave form. the zero axis, the process is known as ode, electrons are attracted and there is In practice, the load resistance of the negative clamping, accomplished merely a flow of current. Conversely, any ele- stage immediately following the diode by reversing the diode connections. ment made negative with respect to the In the circuit of cathode repels electrons and there is no o-11 Fig. 5, values of the current flow. C c condenser C and re- Thus the grid and cathode electrodes sistor R are again of a triode, tetrode, or pentode could be OUT- OUT- selected so that substituted for the conventional diode in INPUT PUT INPUT 111111 PUT their product (RC) the clamping circuits discussed previ- provides a long ously. But it is more usual to employ a time constant, with triode for this purpose. o 0 o o respect to the fre- A typical grid clamping circuit is quency of the input shown in Fig. 7, which supplies positive o signal. clamping. The triode is biased almost to The diode con- the point of grid- current flow, and there INPUT INPUT ducts only on nega- is a resultant large plate current in the tive portions of the load resistance. Values of the condenser o input wave, thus C and resistor R are selected so that E shunting out the their product (RC) provides a long time o constant with respect to the frequency OUTPUT resistor R. The condenser C of the input wave form. OUTPUT charges fairly During positive portions of the input Fig. 4, of -Po itive diode clamping circuit, nega- quickly the of is driven for through signal, the grid the triode tive reference level. Fig. 5, right -A circuit effective positive flows. The cir- the zero reference level. resultant and grid current negative diode clamping at short time con- cuit thus has an effective short time constant. stant. And the condenser C quickly 0-il o 20 K 1(!0 (SMALL) 50K During positive charges to the applied potential. R portions of the in- During negative portions of the input S ou T- o1F-J1Á 11 PUT INPUT OUT- C put wave the diode signal, the circuit presents a long time PUT 5 does not conduct, constant, and the input wave passes un- R IT° and the condenser affected through the triode. _I RFC C discharges only But the charge on condenser C is o o B+ a small amount. sufficient to shift the axis of the input The circuit pre- wave form so that the positive ex- o sents a long time tremities are below the reference level constant to the infor positive clamping. INPUT INPUT put, and the signal Reversal of the grid and cathode con- is relatively unaf- nections of the triode permits negative fected. clamping in much the same manner. o Since the rate of o charge of the con- CLAMPING CIRCUIT APPLICATIONS - denser C is greater OUTPUT than the rate of Diode clamping and grid clamping are Fig. 6, left- Negative clamping, pos.tive reference. discharge, the axis widely employed in radar and television, a tube. Fig. 7, right -Positive clamping with triode of the output wave and to some extent in industrial elec- is tronics equipment. These types of clamp- shifted upward use in (in a positive di- ing circuits find particular connection with cathode -ray tubes. clamping circuit often causes some rection) so that the negative extremi- slight discharge of the condenser during ties of the wave are above the zero When a signal of any type is to be non -conducting portions of the input reference level. This process is known displayed an an oscilloscope, it is usually cycle. This results in a slight extension as negative clamping. necessary to display the wave form with of the positive -going output wave above As previously, the output reference respect to some reference level -at, the zero reference level -instead of just level can be established at some positive above, or below the scope's normal base touching it. This condition may be recti- value above the zero axis. Circuit for line or zero reference. Normally such a fied-as described below-by applying a this type of negative clamping is shown signal would be coupled from the final small bias voltage to the diode vacuum in Fig. 6. output stage to the deflecting plates of tube. A fixed voltage E is inserted in the the scope through a condenser, to pre - plate lead of the parallel diode, re- (Continued on page 560) CIRCUIT VARIATIONS sulting in negative Clamping of the positive extremities clamping of the in- of a wave is not restricted to the zero put signal at a reference level. Positive clamping usu- positive reference ally takes place with respect to some level. Value of the fixed voltage below ground. referenceaxis is ap- For this purpose a slightly different proximately equal clamping circuit is used (Fig. 4.) to the fixed voltage A fixed voltage E is inserted in the E (Fig.6). cathode lead of the parallel diode. Cir- Clamping can cuit operation is similar to the previous, also be accom- unbiased diode clamping circuit. But the plished with a tri- voltage E is additive to the voltage o d e, tetrode o r reference level. This results in positive pentode -using the +300V.B +700VB SMEG 1 clamping of the input signal at a nega- grid and cathode -5000V.B +B tive reference level, the value of which electrodes of such Fig. 8-Typical radar indicator circuit with two clamping diodes. 542 RADIO -CRAFT for MAY, 1946 UKSiEiN

PAIR TO

Common Sense Is an Important Piece of Test Equipment

THE approach to the problems of at the output of the power unit, he will the plate -load resistor is not shorted. radio servicing has been the focal consider this portion of the receiver in Such a condition would indicate the point of much argument, and has good order. If he does not find the volt- complete absence of plate current, and given rise to the development of age output of the power unit normal in the most logical conclusion is that the several conflicting schools of thought. every respect, he will make further cathode circuit is open. A less likely The best approach, the logical ap- measurements to determine which indi- reason is that the tube is biased beyond proach, one both rapid in employment vidual component within the power unit cut -off because of a disorder in the bias and thorough in its revelations -this is is at fault. He will take voltage read- voltage. the goal the several schools of thought ings along several points on the bleeder An other- than -normal voltage reading pursue, each in its own way a different resistor or voltage divider, to measure at point C may indicate open leads or means to the same end. the voltage between the various filter bad connections from the voltage source; What will be the approach? What the sections in search of shorted or leaky shorted, open, or changed value of procedure: direct voltage and resistance screen resistor; or shorted or leaky measurements, channel substitution and A screen or cathode by -pass condenser. section testing, or signal tracing? Every This disregards the possibilities of serviceman must face this question. He shorts or opens within the tube best may choose one, two in. combination, verified with a tube checker. Too high even all three. All three approaches have or too low a voltage at point D in Fig. -r Fig. 2 -Where to look been proved be efficient and successful. 2, is again due to either excessive or to for trouble in e stage. The analytical mind may choose signal insufficient plate current. tracing, the mind excelling in deductive filter condensers or open chokes and Consider the case of an open cathode and inductive reasoning may choose rectifier cathode resistor. Place the voltmeter probe on channel substitution, the mind more im- check the voltage at the to determine if this tube is functiofiing point D and a voltage is indicated. This pressed by visual demonstration than that it is, he will usually be higher than normally by abstract thinking will prefer the di- properly. Once satisfied will check the a.c. voltages on both expected. The reason for any voltage in- rect measurements approach. Let us ex- dication at all at point D is that the amine each method individually. sides of the power transformer. The checkpoints in a simple and typi- voltmeter resistance has shunted the open cathode resistor and thus com- DIRECT cal power supply are shown in Fig. 1. MEASUREMENT pleted the circuit. As implied by its name, this is the The "direct measurements" serviceman will then proceed to measure all What of point E in Fig. 2? Unless most direct approach to servicing. It there is some circuit arrangement to does not necessarily follow, however, the individual plate, screen grid, control grid, and cathode voltages in the re- provide grid bias at this point, no d.c. that it is the fastest method, or even the voltage should be indicated. A sensitive most efficient. It involves the discovery ceiver. These checkpoints, designated by A, B, C, D, and E are shown a.c. voltmeter may be used to indicate of disorders through abnormal or sub- the letters of in Fig. 2. The presence of heater volt- the presence excitation voltage at age can be determined by the "finger that point. "C` test" for metal tubes, or by visual ob- ADDITIONAL MEASUREMENTS servation in the case of glass tubes. oá The direct measurements serviceman, He will determine whether plate finding the tube socket voltages normal, voltage is normal, too high, too low, will then measure the a.v.c. voltage to or not present at all. Should a check at determine if this circuit is operating. CHECK POINTS =X point A in Fig. 2 fail to indicate the He will check for voltage on the local CHECK ALL TRANS. LEADS presence of any voltage, this service- oscillator grid as an indication of oscil- B. A voltage read- Fig. I -Check points in receiver power peck. man will check point lation. ing at this point would be a definite in- If all voltages in the set are normal nora zal voltages, currents, and resist- dication that the plate -load resistor is and the trouble has not been located, he ances; lack of these indications where open. If there is no voltage at point B, will then turn the power off and proceed they should be found; or their presence the lead between this point and the pow- with resistance measurements, checking where they should not be. er supply is making bad contact. for continuity through all the coils and The protagonist of this method values A subnormal voltage indication at his volt- ohm -milliammeter more than point A marks excessive plate current ANT. SPEAKER any other single item of test equipment. such troubles as: R.F. 2ND AUDIO and would suggest MIXER AMP, DET. AMP. The direct measurements approach is Plate -load resistor increased in value, or AMP. the one which requires the least amount or removed en- bias -voltage decreased osc. of test apparatus. A good multitester tirely because of shorted or partially (one with a high ohms -per -volt rating, shorted cathode resistor or cathode by- Fig. 3- Another way of viewing the receiver. or preferably a vacuum -tube voltmeter) pass condenser. is the prime instrument required. If the voltage reading at point A is transformers of the set, all ground re- To the exponent of the direct meas- too high, the plate is drawing too little turns to the chassis, the voice coil of the urements approach, the power supply or no current at all. This would again speaker, and the contact arms on the and its leads are the heart and nervous point to possible trouble in the bias rotors of the tuning condensers. He will system of the radio. He will therefore system. Suppose the voltage at point A check the values of vital resistances begin by making inquiries into the power is roughly the same as the voltage at throughout the set. Resistance measure - supply. If voltage is present and normal point B, and it has been determined that (Continued on page 574) 'RADIO -CRAFT for MAY. 1946 543 Edited by ELMER R. FULLER

WORLD -WIDE STATION LIST

S this goes to press we are wait- will be much better. Reports on recep- on 6.090 megacycles. This transmittèr ing for the few more days be- tion on this band will be most welcome. is also heard at 5 to 10 pm on the same fore the 80-meter ham band is Short wave reception has been rather frequency. again opened to U. S. ama- erratic for some time, and only occasion- CKNC is now broadcasting on 17.82 teurs. We are looking forward to some ally have any good dx catches been megacycles from 7 am to 1:30 pm daily. very good QSO's with several of our made. ZAA in Albania has been heard CKCX is heard from 7 am to 2:45 pm friends of the old days. For some time at 2 to 3:30 pm on 7.850 megacycles. on 15.19 megacycles. CHOL is heard now we have been playing around with This station is quite weak, but comes in from 1:45 to 7 pm on 11.72 megacycles; the ten -meter band, but results on this occasionally with fair volume. VLR2 is and CKLO from 2:45 to 7 pm on 9.63 band have not been what they were ex- heard well at 8 am on 6.150 megacycles, megacycles. These are all heard with pected to be. Several good days have with the news in English. Sign -off very good results in all parts of the been experienced but they were few and time is 8:25 am. ZNS2 in the Ba- country. far between. It is hoped that 80 meters hamas is heard with the news at 8 am All schedules are Eastern Standard Time.

Free. Station Location and Schedule Freq. Station Location and Schedule Free. Station Location and Schedule

MOSCOW, U.S.S.R.: 6 to 8 ant: II 7.320 GRl LONDON,toENGLAgND; G to 10:30 pm; 9.130 H12G CIUDAD TRUJILLO, DOMINICAN 9.480 to 11:30 to 1 ana. 11 pm REPUBLIC; heard" at 9 plat. midnight 11 beam. 7.360 HET3 BERNE, SWITZERLAND; 6:30 to 8 9.140 KUSQ GUAM; heard at m. 9.490 WCBX NEW YORK CITY; Brazilian pot. 9.165 CR6RB BENGUELA. ANGOLA: 3:30 to 4:30 4 to 10:30 mn. U.S. Navy at Guam pm; 8:30 to 9 pm. 9.490 KNBI SAN FRANCISCO. CALIF.: Oriental 7.380 NCN 3:45 am: Hawaiian 7.380 HEK3 BERNE. SWITZERLAND: 10 am to 9.185 HEF4 BERNE, SWITZERLAND; North beam, midnight to 12:30 pin; 3:15 to 3:30 Dm; 8:30 to American beam, 7:15 to 7:45 beans. 4 to 9:45 a 10 pm. 4:20 to 5:20 pm; 6:30 to 8 pm; 8:30 9.490 KNBX SAN FRANCISCO. CALIF.: Oriental beam. 11:15 am to 3:30 7.565 KNBA SANaaFRANCISCO. CALIF.; Oriental to 10 pm. pm. 9.235 COBQ HAVANA. CUBA; 8 am to noon; 8 9.490 GWF LONDON, ENGLAND. KONG; 4:30 to 7.565 WNRE NEW YORK CITY: European beam, to 10 pm. 9.495 ZBW VICTORIA, HONG midnight to 3:15 nt; 4:30 to 6 pm. 9.270 COCX HAVANA. CUBA; heard at 12 am. 8:30 111 8 mu to 7.570 EA143 SANTA CRUZ, CANARY ISLANDS: 9.300 MACEIO. BRAZIL; 0 to 7 pm. 9.500 XEWW MEXICO CITY. MEXICO; 11 am to 5 to 6:15 pm. 9.330 KU5Q GUAM; 8 n 2 11 7:15 to 7:45 7.575 KCBA SAN FRANCISCO, CALIF.; East In- 9.330 ANDORRA;noon to 7 pm. 9.502 01X2 LAHTI, FINLAND; pm; dics beans, 4 to 9:45 9.305 PY MANILA. PHILIPPINES: 5 to 7 am; 11 to 11:30 pm. 7.805 KNBX SAN FRANCISCO. CALIF.; Oriental Il to 11:30 pm. 9.510 TAP ANKARA, TURKEY; 1 to 2 pm. beam, 5 to 11:00 am. 9.340 PJY9 WILLEMSTED. CURACAO. 9.510 GSB LONDON, ENGLAND; Near East 12:30 7.805 WOOC NEW YORK CITY; European beam, 9.345 HBL GENEVA, SWITZERLAND; 1 to 3 beam. 11 pm to 1:15 am; to midnight to 3:15 am; 3:30 to 5:45 pm. 4 pm: South American beam. 4 to pm. 9.350 VIENNA, AUSTRIA; heard at 9:30 9:45 pm; Italian beam, 12 to C am; 7.850 ZAA TIRANA, ALBANIA: English at 3 to lam. 12:30 to 4 pm. 3.20 pm. 9.350 SOFIA, BULGARIA; to 11 9.520 PARIS, FRANCE; North American ; 12:45 1 1:15 7.860 SUX CAIRO. EGYPT; 5 to 5:30 pm. 9.360 CBFX MONTREAL, CANADA; 6:30 am to beam, 12:30 to am; to 7.950 ALICANTE. SPAIN: off at 6 pm. 10:30 Em. 8.000 DAMASCUS, SYRIA: 11 pm to mid- 9.360 CET1 N1 E, YUGOSLAVIA; 1:30 to 3 9.520 VLW7 PERTH. AUSTRALIA; 5:30 to 10:30 night. 8.030 FXE BEIRUT. LEBANON; 11 pm to 5:30 9.370 EAQ MADRID, SPAIN; 2 to 3 a m; 7 to 9.520 ZRG JOHANNESBURG. SOUTH AFRICA; am. 9 am; 10 am to 5 pm; 6:30 to 9 pm. 3 to am. 8.565 AFN MUNICH. GERMANY; 4 am to 12:15 9.380 COBC HAVANA. CUBA: heard at 5:30 pm. 9.525 GWJ LONDON, ENGLAND; Near and Mid- pin. 9.385 OTC LEOPOLDVILLE. BELGIAN CONGO; dle East beams, 11:45 pm to 12 m; 8.665 COJK C MAGUEY. CUBA; 8 pm to 12:30 5:30 to 7:30 3:30 to 4 pm; African beam. 3:30 9.410 GRI LONDON. ENGLAND: African beam, to 4 pm; European beam. 11:30 pm 8.696 COCO HAVANA, CUBA; 7 am to 11:30 pm. 12:30 to 2:30 am; 5:30 to 7:95 am; to 1:45 am; 5 to 8 am: 10:15 am to 8.830 COCO HAVANA, CUBA: 4:30 am to 12:30 10:30 am to 1 pm; 2:30 to 5:30 pm_ 11:30 am; 12 to 4 pm. am. European beam. 12:30 to 2:45 pm; 5 9.530 WGEO SCHENECTADY. NEW YORK; South 8.840 DAKAR, FRENCH WEST AFRICA; to 7:45 am: 10:15 am to 9 pm: American beam, 5 to 11 pm. afternoons till 4:30 pm. 4:30 to- 5:30 pm. 9.535 121 TOKYO, JAPAN; 7 to 8:15 am, 8.950 COKG SANTIAGO, CUBA: 6:30 am to 10 9.420 BELGRADE. YUGOSLAVIA; mid- 9.535 SBU STOCKHOLM, SWEDEN: 1:30 to r night to 2 am; 10 to 10:95 am. pm; 8 to 9 pm; Sundays only 5 to 8.985 COKW HAVANA CUBA; evenings. 9.440 F21 BRAZZAVILLE, FRENCH E8 9 9.030 COBZ HAVANA, CUBA; 7 am to 11 pm. TORIAL AFRICA; am to North am. 9.535 BERNE. SWITZERLAND; 9.082 CNRS RABAT, MOROCCO; 2 to 5 pm. mid- midnight to 2.30 America at 8:30 to 10 pm. night to 3 9.465 TAP ANKARA, TURKEY: 11 am to 4:45 Asiatic pm. 9.540 VLG2 MELBOURNE, AUSTRALIA; 9.120 BALIKPAPAN. BORNEO; heard 5 to beam. 7 to 9 am. 6 pm. 9.470 CR6RA LOUANDA. ANGOLA; heard signing North BUDAPEST, HUNGARY. off at 4:30 pm. 9.540 VLC5 SHEPPARTON, AUSTRALIA; 9.125 HAT4 American beam. 7 to 7:45 am: 8:45 to 9:45 pan. 9.540 PARIS, FRANCE; midnight to 12:15 am; 12:30 to 12:45 am: 1 to 1:15 am. 9.540 XERQ MEXICO CITY. MEXICO: evenings. 9.540 LKl OSLO, NORWAY; 2 to 2:30 am; 4:45 to 7 am. 9.540 CJCA EDMONTON, CANADA: 9:30 am to 11 pm. 9.548 SINGAPORE. MALAYA; 8 to 9:30 am. 9.550 GWB LONDON, ENGLAND. 9.550 OLR3A PRAGUE. CZECHOSLOVAKIA: 3 to 6 pm. 9.550 KGEI SAN FRANCISCO. CALIF.: Natal In- dies beam. 4 to 10:45 am: Alaska beam, 11 am to 12:45 Dm. 9.555 XETT MEXICO CITY. MEXICO. 9.565 KOMSOMOLSK, U.S.S.R.; 9 pm to midnight; 2 to 9 am; 11 am to 2 Dm; 4 to 6 pm. 9.570 KWID SAN FRANCISCO. CALIF.; Oriental beam, 11:15 stn to I pm; South American beam. 7:45 to 11:15 pm; Alaska beam, 11:30 pm to 1:45 am. 9.570 WRUA BOSTON, MASS.; European beam, 4:30 to 6 pm. 9.570 KWIX SAN FRANCISCO. CALIF.: Oriental beam, 2 to 11 am. 9.580 GSC LONDON. ENGLAND; Central and South American beam, 4:15 to 9:15 pm: Indian beam. 8 to 8:15 pm. 9.580 VLG MELBOURNE. AUSTRALIA: Indian beam. 9:35 to 9:45 am. 9.590 WLWO CINCINNATI. OHIO; European beam. 3 to 4:45 pm: South American beam, 6 pm to 12:15 am. 9.590 VUD4 DELHI. INDIA: 8 to 10:50 pm: 1 to 4 am; 5:30 to 7 am: 7:30 am to 3:45 pm. 9.590 PC1 EINDHOVEN, NETHERLANDS; 3 to 4 pm: 9 to 10 pm. 9.595 ATHLONE, IRELAND: 4:10 to 4:30 9.600 XEYU MEXICO CITY, MEXICO: heard late afternoons and a e:P:gs. (Continued on page 550) "But I tell you -I hid $150 in my radio!" 544 RADIO -CRAFT for MAY, 1946 By 1. QUEEN

A U. H. F. HAM TRANSCEIVER. A Practical Unit for the 420- and -up Amateur Band

WITH activity starting to long and separated by about % inch. boom on frequencies higher The miniature 50 µµf condenser is con- than 400 mc, we decided a nected across the far ends of the lines. short time ago to construct The tube ends connect directly to the and experiment with a compact, low- tube contacts. power transceiver which would operate Polystyrene blocks are used to insu- at these frequencies. A portion of the late and support the r.f. components. The amateur band in this range (420-430) presence of this material has no appre- has recently been made available. The ciable effect on the r.f. fields, and though remainder, comprising 430 -450 mc, will expensive, it is well worth -while. Leads probably be opened very shortly, giving between the r.f. and audio circuits go the amateur 30 whole megacycles with through holes drilled through the poly- which to experiment in a desirable part styrene. The material machines very of the spectrum. The new citizens' band, well, taking saw, drill or tap very nicely fr -m 460 -470 mc, should also be opened The plate, grid and cathode circuits The transceiver with power pack (in rear) soon. This, for the first time, will make must be well isolated from other cir- radio reception and transmission legal cuits by suitable r.f. chokes. We wired 1% inches from the front panel. This without any license of any kind. This up a number of these experimentally, effectively eliminates capacitance ef- transceiver covers a range of 415 -500 taking off turns until we arrived at an fects, which we feared at first. The met - mc, including all the above. optimum in each case. Quite a bit of altshaft of the variable tuning condenser Not much thought to power can be lost through inefficient or is extended by means of an insulated had be given and a short of polysty- to choice of tubes, as the field is pretty insufficient chokes. coupling length well limited to the well -known and popu- The tuned circuit is set back about rene rod. The front panel will accom- 2 -inch we lar 955 acorn type. The small size modate a dial but were un- fits to locate one in Radio Row and had well with the compactness of other com- able ponents at ultra high frequencies and to be content to make a home-made job. the low power requirements make This was done by pasting a circular it with inked divisions on` possible to run it efficiently from the piece of paper a.c. line or from medium -sized batteries. the panel and using a small bakelite ar- The complete set, except for speak- row knob. er or mike and power supply, can be POWER OUTPUT VS. FREQUENCY built in a space less than 4 x 4 x 4 inches. This is the size of our unit but As might be expected, the output is the photograph shows appreciably greater at the lower fre- unused space Even the acorn begins within this volume. It is possible, for quencies. tube example, to incorporate a small 2 -inch (Continued on page 585) PM speaker or small "B" batteries for the plates. We were more interested in getting a solid, clear signal out of the antenna and this has been accomplished. Vibra- tion and movement of the transceiver during transmission has no adverse effect on the signal and the frequency once set remains constant. There is no evidence of hand capacity during tuning. This instrument is definitely not a toy and the design has not been limited for the sake of compactness. Experiments carried on over short distances within the same block show Top-The oscillator that the waves pass readily through partitions and brick walls. Communica- circuit. Heavy tubas tion over short distances did not require are "long lines' and the receiver to be equipped with anten- bent wire is antenna na. Our experiments show that with no coupling. Below -Au- benefit of location a mile or so can be dio section. Batteries covered. Given the advantage of height strapped to the trans- the signals should go the line-of -sight former are fo excite limit with a reasonably good signal. the carbon microphone. R.F. SECTION The circuit is a parallel -line affair but with condenser tuning for convenience and ease of calibration. The lines are u -inch copper tubing, each 2 inches RADIO -CRAFT for MAY, 1946 545 SIGNAL GENERATOR circuit makes this oscillator easily sistors and condenser values give this A few parts from the junk box may adaptable for multi -band use. unit excellent frequency response. be assembled into an efficient signal A practical adaptation of the circuit In keeping with our desire to make generator in a short time. This will is shown in Fig. 2. Here it is used as an furnish either modulated or unmodu- audio -frequency signal generator. The lated r.f. signals at the will of the opera- coil Li, and capacitors Cl, C2, C3 tor. and C4 are chosen by experiment or cal- The circuit uses a 1G6 -GT twin tri- culation. Selector switch S1 is used to ode as radio and audio frequency oscillators. The grid coil of the r.f. oscil- Radio -Craft wants original kinks from its readers, and will award a seven - month subscription for each one pub- IG6G 40K A5 lished. To be accepted, ideas must be new and useful. Send your pet short -cut RÁÑS or new idea in today!

select any of the desired frequencies 81+ FI 0400.., which are determined by the values SW.151 AUDIO of TONE the capacitors. Continuous change of 117uAC ¡.001 8+45V 6-0A- A+L5Vo 80. FIL. 600V TRANS + 8+ r 1I lator is wound with No. 32 enameled 216v1`? wire, close wound, to cover 11/4 inches on -+ T a 1 -inch form and is tuned by one sec- RESISTORS.25W,EXCEPTAS NOTED. tion of a standard broadcast condenser. This winding is then covered with a the unit as compact as possible; an thin sheet of celluloid. The plate wind- a.c: d.c. circuit was used. As the cur- ing is wound over the lower end of the rent ratings of a 6H6 will not be ex- grid coil and covers 3/16 -inch. The out- ceeded by the current demands of the put coil is wound immediately above 6SJ7, a 6H6 working into a R -C filter the plate coil and covers.% -inch wind- was used as a full -wave voltage doubler. ing space. frequency can be attained by using a The filament requirements for the The modulator uses a straightfor- large variable capacitor instead of the tubes are met by using a small 6.3 -volt ward audio oscillator circuit. The trans- switch and fixed capacitors, but at au- transformer. former is one designed for inter -stage dio frequencies, the size of the variable Note -The unit may be made more coupling. A transformer with a 3 -1 condenser becomes very large. compact by using a 350-ohm line cord turns ratio is applicable to this circuit. A cathode follower stage has been resistor. The panel controls are: TUNING, PAUL FISK, OFF -TONE -R.F., and ATTENUATOR. Montreal, Canada The dial used on the tuning condenser 6J5 6J5 6J5 should be free from back -lash and 6+ "MYSTERY" IMPROVEMENT capable of close calibration. The OFF - I l LsWiC C2TC3TC4,l,-1 On page 718 of Radio -Craft for TONE-R.F. control is a double pole, August 1945, you published my "mys- It I three position switch. Variable r.f. out- CS tery" circuit and requested to hear fur- put is possible through the use of a ther reports about the set. 1,000 -ohm potentiometer across the out- It became evident that the 6B6 output winding of the r.f. circuit. put tube was operating under difficul- The plate voltage is supplied by a ties. I therefore took the 6B5 out and small "B" battery of the hearing aid substituted a 6A3. type and the filament voltage is sup- Fig.2 The results were astonishing. Tone plied by a flashlight cell. added to couple the oscillator to the quality and general fidelity was im- If either of the oscillators fail to os- output terminals and to provide a low proved fully 100 %, and the volume and cillate, it may be necessary to reverse impedance output. selectivity also registered substantial the connections of either of the wind- Potentiometer R4 serves as the out- gains. The whole circuit loosened up and ings. put level control and the cathode load took on new life. Several bugs and This signal generator produces a resistor. Changes in the output load and gremlins disappeared entirely. signal from 400 to 1500 kilocycles and adjustment of the output level should The most "mysterious" and gratify- is useful in servicing broadcast re- have very slight -if any -effect upon ing result obtained was the automatic ceivers. oscillator frequency. change from dual to single control. With A. SKITSKI, Lno G. SANDS, the regeneration control placed at the Waakatenau, Alberta Towson, Maryland extreme position, that position became permanent and the circuit could be per- UNIQUE OSCILLATOR MICROPHONE PREAMPLIFIER fectly handled over the entire broadcast A unique oscillator circuit using two This compactly built preamplifier has band by using only the volume control. separate triodes or a dual triode tube is enough voltage gain to couple a crystal The only other change made is the illustrated in Fig. 1. A 6SN7 -GT or a microphone into the audio frequency end rewinding of the coils with No. 28 pair of 6J5 tubes are suitable. This os- of practically any home radio receiver. enamel wire instead of No. 32 as here- cillator will perform at radio or audio It is designed around the 6SJ7, connect- tofore used. frequencies, depending upon the circuit ed as pentode with an approximate volt- RALPH W. MARTIN, constants. The simplicity of the tuned age gain of 100. Carefully selected re- Loa Angeles 82, Calif. 546 RADIO -CRAFT for MAY, 1946 RCA VICTOR MODELS 54B1, 54B1-N, 54B2, 54B3

SPECIFICATIONS ductance. Ground test oscillator through Frequency Range 550-1,600 kc. .1 mf. capacitor to receiver chassis. Intermediate Frequency 455 kc. CRITICAL LEAD DRESS ALIGNMENT PROCEDURE I. Dress blue, green and black leads of second i.f. transformer as direct as Test Oscillator.-Connect test oscil- possible. If excess lead exists, dress lator as indicated in chart, keeping the down side of socket and flat as pos- as low as possible to avoid a.v.c. output sible against chassis to transformer room behind the battery holder to action. opening. allow the holder to move when a bat- Output Meter.- Connect meter from 2. Cross the green and the black leads tery is installed or removed. top lug of TBI (plate of 354) to ground. inside the first i.f. transformer can, 5. Dress the "B" battery leads behind Turn volume control to maximum position. keeping the green lead to the outside. the gang frame and over the top of 'Steps 3, 4 and 5, shown in alignment Keep the blue and the green leads the output transformer. table, require a coupling loop from the separated as far as possible through- 6. Observe the outside foil connections signal generator to feed a signal into the out their length. on all paper capacitors, also the receiver loop located in the lid. This loop 3. Dress audio coupling capacitor (C14; polarity of the electrolytic capacitor should be approximately one turn of .002 µf.) and the lead to the volume (C17). 6 x 311/2 inches coupled to the signal gen- control up and underneath the shelf 7. Keep blue and red leads of output erator through a 200 µµf capacitor, and supporting the output transformer. transformer above the mounting shelf. loosely coupled to the receiver loop an- 4. Dress the three capacitors pyramided tenna at about 1% inches distance, so behind the speaker, parallel to the Note: Do not install "A" battery with- as not to disturb the receiver loop incomplete assembly and with enough out cardboard cover. A rubber band should be placed around each one of the tubes for TABULATION FOR ALIGNMENT cushioning. Connect the Adjust the high side of Tune test -osc. Turn radio following for eBAT Steps test osc. to- dial to- max. peak CUP to- output - +{ Connection Quiet point C11 C12 tja 67.5V 1 lug of C2, 455 kc. near 1,600 kc. 2nd i.. trans. r

1 AVC located on 1 354 rear of gang ' 2 in series Quiet point C8, C9 SWIi 155 I IST I.F. with .01 µf. 455 kc. near 1,600 kc. 1st i.f. trans. .TRANS `20LF TRANS C8, C9 KC 455 KC 3 "Antenna 1,600 kc. 1,600 kc. C5 (osc.) (((455 coupling 174 T loop thru 200 4 µµf. capacitor 1,500 kc. 1,500 kc. C2 (ant.) (See - Align- ( Ut5 OSC. - ment Proce- 800KC dure- for 600 kc. 600 kc. L2 (osc.) C5 OSC. C2 ANT explanation.) 1600 KC 1300 KC 6 Repeat steps 4 and 5 for final adjustments. Positions of trimming, padding and i.f. trimmer condensers.

IR5 I T4 IS5 3S4 IST DET..OSC. I.F. 2ND DE L. A.F. A.V.0 OUTPUT F+ F- 1 LOOP 36 a OG G G

LI SUP SUP +34V green green C20.005 PT, +34V IST I.F. 20 I.F. +56V CI a4C2 blue 60V 10- 1 15,,,f r------IE? 2- blue be .002 /530, 274 = `TI V.C. C6, '4C9 CÑ.tr, - C12 2n

1 4, - Mad -6V.1600KCG RI +34V L5 L6 L7 L6 R6 RB +60V -7V.,1500KCI 100K 139,0 C14 2 blue T ,2O black MEG 4.7 B.$ PM SPEAKER _C4 p V.C. MEG áll R4}.002 1C10 10 MEGS re en ( 2'.02 R21 02 C6 C5 CC 15K' 75- 1l T2-IS.d red 1225 11.K,te L2 L4 C17 RIO 4, In R3 10 3.3 MEG -o- + 1.5V A BATT.

7 3.3MEG C16 ellow ello R9 Note: CS and C6 are variable; the I.05 = 33 / arrow was inadvertently omitted. 67.5V. B BATT 620 1 SW.I ON LID

BAIT VOLTAGES SHOULD HOLD WITHIN 2O %. MEASURED t WITH CHANALYST OR VOLTOHMrST, VOLTAGES MEASURED WITH RESPECT TO CHASSIS GROUND.

RADIO -CRAFT for MAY, 1946 547 SWEEP CALIBRATOR PRECISE VOLTAGE SUPPLY flat response for high fidelity sound United Cinephone Corp. Clippard Instrument Laboratory pick-up or wide range with rising char- Torrington, Conn. Cincinnati, Ohio acteristic for extra crispness of speech or high frequency emphasis. This instrument provides calibration This custom -built instrument fur- marks for use in calibrating the sweep nishes a.c. potentials of laboratory ac- It is designed for high quality pick- voice speed of a synchroscope or triggered curacy in 1 /10th -volt steps from 0 to 111 up and reproduction of and music sweep oscilloscope. The markers consist for laboratory or production line use in -in public address, recording and re- of short video pulses, of less than s/z testing and calibration of a.c. meters, mote broadcast communications. -Radio microsecond duration, spaced apart by vacuum tube voltmeters or other circuits Craft an exactly known number of micro- where a known source of a.c. voltage is seconds. required. Ranges: Switch permits choice of It incorporates a precision trans- four different time intervals between former of the true isolating type with calibration markers: 2.5, 10, 50 and 100 a primary tapped to adjust within one microseconds. tenth of one volt of line voltages from 100 to 132. Secondary is precision tapped to provide output voltages of 0 to 111 in 1 /10th -volt steps. A Weston meter, model 476, is placed in the secondary circuit for highest accuracy and is calibrated with a single red line to indicate proper primary voltage adjustment. When the primary is adjusted to 100 volts the instrument may also be used as a variable ratio transformer provided input voltages do not exceed calibration settings. One- thousand-to-one to one -to-one values in Markers have an amplitude of 40 steps of one one -thousandth are fur- volts, with choice of polarity. nished in ranges up to 10,000 cycles. Trigger Pulse (internally generated) : Choice of polarity. The positive trigger has an amplitude of 120 volts; negative 65 volts. The repetition rate is continuously variable by means of a COLD -CATHODE RECORDER calibrated control from 2000 to 3000 Sylvania Electric Products Co. c.p.s. Boston, Mass. Operation from an external trigger The R -1130 is a modulator glow tube pulse, either positive or negative, of 66 of the crater type that is rugged and volts. dependable for facsimile and sound -on- Gate: Continuously variable duration film recording; oscillograph timing of 20 to 3000 microseconds. (gate length markers; stroboscopic devices; seismic is length of time during which markers recorders; and photo- electric counters. are generated following each trigger The tube, usually operated by the pulse. All markers that would appear single -ended output stage of a push - subsequent to this interval are sup- pull amplifier, provides a modulated, pressed.)-Radio-Craft high -intensity point -of -light source by means of a hollow cathode producing INSTRUMENT RESISTORS high ionization density which may be. Instrument Resistors Co. viewed in depth. Current through the Little Falls, N. J. tube varies linearly with the signal Four new types-ALA, ACA, BLA Output is conservatively rated at voltage regardless of changes in tube and BCA offer the advantages of close 30 -volt- amperes as follows: 0.1 to 1 volt, impedance. 5 amperes permissible current; .01 to tolerance, high quality and low unit cost. Used receiver 11 volts, 2 amperes; 0.1 to 31 volts, 1 in a typical facsimile Type ALA is a 3 -watt resistor, with a the light output of the tube is focused maximum resistance of 2500 ohms in ampere; 0.1 to 111 volts, 0.3 amperes. Accuracy of 1% is guaranteed for the through a baffle with a sharp rectangu- voltage output of one -quarter of 1% for lar opening to produce a spot of light. the ratios.- Radio -Craft .0072 -inch high and .0104 -inch wide on a drum rotating at 90 r.p.m. Scanning movement is .0104 -inch per revolution. CARDIOID MICROPHONE Type R -1130 recording tube is sup- Electro- Voice, Inc. plied in a T -9 bulb with intermediate South Bend, Indiana shell octal base and may be operated nichrome and 5000 ohms in manganin. A new cardioid unidirectional crystal in any position. Providing a useful light Type BLA, rated at 5 watts, runs to microphone, with high output, dual fre- range between 3500 and 6500 angstroms 50,000 ohms (nichrome) and 10,000 quency response selection, and other it will respond to frequencies between ohms (manganin). Types ACA and features is announced. 15 and 15,000 c.p.s. Rated at 135 volts BCA are the same as ALA and BLA The new CARDAX has a dual fre- d.c. with currents ranging from 6 to 35 except for a coating of high-tempera- quency response selector on back of ma, it requires a starting voltage of ture cement. -Radio -Craft microphone which enables wide range 170 d.c. maximum.-Radio-Craft 548 RADIO-CRAFT for MAY, 1946 FM CARRIER STABILIZATION (Continued from page 538) _ALLIEDSX946 a buffer stage and individual low pass filters and then applied to a phase discriminator of the conventional type known to FM technicians and repair- CATALOG men (Fig. 11). The magnitude of the discriminator a.c. output voltage depends upon the difference of phase between Rut& dad the two applied frequencies A and B. The polarity depends upon whether the stmt s Hartley oscillator frequency A drifts upward or down. The low-pass filter which follows the discriminator grounds out the rapid a.f.

IIZIlJ IAAJ I2H6 '11r FREE 1:2 II CI OUTPUT Send for it Now! C2 II

Fig. I I -The 12H6 output corrects frequency. modulation and permits only the vary- LARGEST AND MOST COMPLETE STOCKS ing voltage caused by gradual frequency Today's handiest, most complete Buying Guide! drifts to affect the grid bias of the Mill- Brings you latest, finest values in parts, tubes, er tube (V -903). Change of grid bias kits, tools, books, test instruments, communi- of this tube varies the input capacitance cations receivers, Ham gear, public address of the and therefore the frequency and other equipment. Places at your finger Hartley tank coil across which it is con- tips over 10,000 items of nationally known nected. The original frequency drift of NEW guaranteed quality. Makes available to you RADIO SETS the Hartley oscillator is compensated Parade of new world's 1 94 6 for in this way. the largest and most complete stocks models, including under one roof ready for rush delivery. radios, phono- The output frequency of the CFS ... and latest commu- Enables you to get everything you need in nications receivers and modulator unit is multiplied in suc- Ing Cover- radio and electronics from one dependable, broadcast, short-wave ceeding stages to bring it into the FM and amateur bands. Beau- band. The center frequency of this trans- central source. Send for this new 1946 Cata- tiful styles) Wonderful per- mitter is maintained to within .001 per log now. Save time, work and money! formance) Outstanding cent of its assigned values. values!

THE RCA ANTENNALYZER (Continued from page 536)

value of the same signal. The instrument panel used for this purpose may be seen near the top of the Antennaly- HANDY RADIO BOOKS zer. The signal from the Antennalyzer AND CALCULATORS ITEMS Radio Formulas 10,000 NEW P.A. EQUIPMENT is fed first to the peak- reading volt- Denary & deb, Dle- OVER of Radio Terms, of quality Sound meter which consists essentially of a dio Circuit Handback.81/n Ra- Biggest section systems for Builders' Handbook, Radio for every - equipment public address fled Radio Servlein9, eli ports and require- diode rectifier. The input signal is ad- Data Radio erv- ment. Handbook Six Complete No. 37 -799, - Books engineers, anla- listing justed until the meter in the output 7Se. SOY dmens, amplifiers, of Parallel Resistance icemen, speakers, reads full scale. Then the signal is Capacitance and Sertes AU leading crophones, mi. Calculator, tears, builders. accessories. No. X37 -gyp lowest prces. Newest switched to the input of the r.m.s. volt- R -F Resonance makes, at developments lee and Coll Wind. now. many with meter. The output meter is switched to Calculator. for Free Catalog exclusive N. 37 -955 features, this voltmeter at the same time. Since ...... 2sc the meter scale is calibrated with full r- - scale equal to unity, the new reading is ALLIED RADIO CORP. now the ratio of the r.m.s. signal to 333 W. Jackson Blvd., Dept. 2 -EE -6 the peak signal. ! Chicago 7, Illinois Date ALLIED Send FREE New 1946 Catalog. A supersonic reflectoscope using I Send Six Books- Calculator No. f enclosed sound waves to locate flaws in solid ' Calculator No. objects has been developed at the Uni- RADIO versity of Michigan, reports Dr. Floyd I Name A. Firestone of the departments of physics and engineering research of the A ddrene Soezrfai ík Radio University. Is uses a quartz crystal cov- Cita Zane State and G`'leeLtaw:ea ered with a film of oil to contact the object being tested. RADIO -CRAFT for NI/ Y, 1946 549 WORLD -WIDE STATION LIST (Continued from page 544)

6.606 GRY LONDON. ENGLAND: African beam, 10.000 XGOL FOOCHOW. CHINA: 5 to 9 am: 12:15 to 4 pm; Near East beam, 11:30 pm to 1 am. 2:30 to 4 pm; Middle East beam, 11 10.220 PSH RIO DE JANEIRO. BRAZIL; eve- pm to 1:95 am; Australian beam. nings. 11 pm to 3 am. 10.400 YPSA SAN SALVADOR, EL SALVADOR: 6.608 ZRL CAPETOWN. SOUTH AFRICA; 3 to heard evenings. 7 an 9 am to 4 pm. 10.420 VLN SYDNEY. AUSTRALIA; around 12:15 9.610 ZYCB RIO DE JANEIRO. BRAZIL; eve- am. nings till midnight. 10.450 MOSCOW, U.S.S.R.; midnight to 2 9.610 MCH LUXEMBOURG; heard irregularly at 9:30 to 10 am. 4:30 pm calling New York. 10.510 KUIG GUAM; heard calling NBC around 9.615 TIPG SAN JOSE, COSTA RICA; 9 pm to 5 :30 pelt. 12:30 am. 10.730 VQ7L0 NAIROBI. KENYA; 9 am. 9.623 CXA6 MONTEVIDEO. URUGUAY: 3:30 to 10.780 SDB2 STOCKHOLM. SWEDEN; 3:15 to 5 8 pm. pm. 11.040 6.625 XGCA Somewhere In China: G to 7:45 am. CSW6 LISBON, PORTUGAL; Brazilian 9.625 GWO LONDON. ENGLAND: African beam, beam, 12:30 to 3 pm: 4 to 6 pm. 12 to 1:15 am; Middle East beam. 11.090 PONTO DEL GADA, AZORES; 3 to 12.15 to 12.30 an; 1:30 to 2 pm; 4 pm. 4:15 to 9:30 pm; European beam. 12 11.115 MCH LUXEMBOURG; heard with Army to 12:30 am; 1 to 2:93 am; 5 to hour for New York. 7:30 am; 10 am to 11 am: 12 to 11.145 WCBN NEW YORK CITY; European beam. 1 1:30 pm; 2 to 5:45 pm. to 5:45 pm. 9.630 CKLO MONTREAL. CANADA; European 11.595 VRR4 JAMAICA. BRITISH WEST INDIES: beam. 3:15 to 7 pm. heard at 10 am. 6.640 GVZ LONDON. ENGLAND: North Amer- 11.616 COK HAVANA, CUBA; 11 am to 11 pm. his ican beam, 4:15 pm to 11:45 pm; 11.640 PY2 MANILA. PHILIPPINES; 6:30 to New Zealand beam. 12 to 4 am. 7:15 am: evenings. 9.646 XGOY CHUNGKING. CHINA: East Asia and 11.645 BRUSSELS. BELGIUM; evenings South Seas beam. 6:35 to 8:40 am; about 7:30 pm. BOOK 11.650 Big Ghirardi North American beam, 8:45 to 10:40 XTPA CANTON, CHINA; 7 to 9:15 am. ant; European beam, 10:45 am to 11.680 CMCY HAVANA. CUBA; afternoons and eve- 11:30 am; East Asia and South Seas nings. beam. 11:30 am to 12:45 pm. 11.680 GRC LONDON, ENGLAND; Far East MAKES IT EASY for 9.660 G W P LONDON. ENGLAND: African beam. beam. 9 to 10:15 am: Middle East 11 pm to 1:15 am; For East beam. beam. 12 to 2:15 pm. 11 pm to 3 :45 am; North African 11.690 XGRS SHANGHAI. CHINA; 10:15 am to beam. 1 to '45 am. 11:30 you to. LEARN BASIC 9.660 HVJ VATICAN CITY; noon to 1:30 pm: 11.696 HP5A PANAMA CITY, PANAMA; 7 am to 1:45 to 2:30 pm. 11 nm. 9.660 HHBM PORT AU PRINCE. HAITI; 5 to 11.700 G V W LONDON, ENGLAND: African beam. 8:30 am; 11 am to 2 pm: 5 to 9 pm. 10:30 am to 4 pm. RADIO- ELECTRONICS 9.650 MOSCOW. U.S.S.R.; 4:30 to 9:15 pm. 11.705 SBP STOCKHOLM, SWEDEN: 8 to 9 pm; 9.670 WRCA NEW YORK CITY; Brazilian beam, 1:45 to 2:15 am:6 to 7 am. 7 to 10:30 pm. 11.705 CXAI9 MONTEVIDEO. URUGUAY: 8 to 9 9.670 VUDIO DELHI, INDIA: 7:20 to 11:30 am. pm. 9.675 JVW2 TOKYO. JAPAN: 2 to 5 am: 5:30 to 11.705 CBFY VERCHERES, CANADA: 30 am to 11 7:15 am: 7:30 to 9:40 am; 9:55 to ant. COURSES ONE 11:40 am; 12 to 1:40 pm; 4:30 to 11.710 WLWS2 CINCINNATI. OHIO: South American 36 IN 6'45 pm. beam, 5 to 7:15 7:30 to 9:30 19.675 GWT LONDON. ENGLAND: beam, pm; African Pm. 1:45 to 2:15 pm; Canary Islands 11.710 WLWK beam, beam. 1:30 to 1:95 am; 2:15 to CINCINNATI, OHIO; European 7:30 am to 4:30 2:30 am: 3 to 3:30 European pm. pm; 11.710 VLG3 MELBOURNE, AUSTRALIA: North COMPLETE beam, 1 only to 2 am; 5 to 7:30 am; $5 beam. 10 10:45 am, 8:45 10:15 am to 12 pm; 12:30 to 1:30 American to to 9:95 pm, Tahiti beam. 1 to 1:40 pm: 2:15 to 4 pm. 2:23 am. 9.680 XEQQ MEXICO CITY, MEXICO: evenings. am. British beam. 1:55 to Send the coupon today! Examine Ghirardl'a famous Northern Asiatic beam, 2:30 to 2:55 9.680 V LC2 SHEPPARTON. AUSTRALIA; North- RADIO PHYSICS COURSE. See for yourself how this ern Asiatic beam: 2:30 to am. 3:30 am; 11.715 British beam. 11:15 am to 11:45 am. HEI5 BERNE. SWITZERLAND: Tuesday giant 972 page. 314 lb. book at ONLY 65 gives 9.680 EQC TEHERAN. IRAN: I to 3:30 pm. and Saturday. 10 am to noon. complete basic training that can pave your way to a 11.718 CR7BH MARQUIS, MOZAMBIQUE. 9.683 LRAI BUENOS AIRES, ARGENTINA; 6 to good paying Job or business of your own in Radio, 8:30 pm. 11.720 PRL8 RIO DE JANEIRO, BRAZIL; 9:30 to Television, Fat, Facsimile, Broadcasting, Communi- 9.685 TGWA GUATEMALA CITY. GUATEMALA; 9:55 pm: off Saturdays and Sundays. Sundays at G:55 pm. 11.720 CKRX WINNIPEG, CANADA. cations, etc. See how its 972 profusely illustrated 9.680 GRX LONDON, ENGLAND, Australian 11.720 OTC LEOPOLDVILLE. BELGIAN CON- pages give Just the training you need -ALL YOU beam, 12 to 4 am. GO: 5:30 to 7:30 am. NEED osier, better. faster-AND AT FAR LESS 9.700 WRUS BOSTON. MASS.: Central American 11.725 JVW3 TOKYO. JAPAN; heard at 1 pm. Every step beam. 6:30 pm to 1 am. 11.730 KGEI SAN FRANCISCO. CALIF.: South- COST. No previous training is necessary. 9.700 KCBF SAN FRANCISCO, CALIF.: Oriental west Pacific beam. 1 to 9:45 pm. is made crystal clear. Many beginners have completed beam, I to 9:45 pm. 11.730 WRUW BOSTON, MASS. European beam, 1 it in a few weeks. Thousands of Ghirardi-trained 9.700 KCBR LOS ANGELES. CALIF.; Oriental to 5 pm; Caribbean beam, 5:15 to men now hold important Radio- Electronic positions. beam, 2 to 4:45 am: 5 to 11 am. 5:45 pm. 6.705 FORT DE FRANCE. MARTINIQUE; 11.730 KGEX SAN FRANCISCO. CALIF. South- heard at 5:30 pm. west Pacific bean. 2 to 4:45 am. No training AT ANY PRICE is more 9.710 CR7BE LOURENCO MARQUES. MOZAM- 11.730 WRUL BOSTON. MASS.: North African widely endorsed by experts themselves. BIQUE, 2 to 3:30 pm. beam. 6 to 8:95 am; Mexican beam. 9.715 MOSCOW, U.S.S.R.; 6:30 to 7:30 am. 6:30 pm to 1 am. 9.720 PRL7 RIO DE JANEIRO. BRAZIL; 3 to 11.730 GVV LONDON. ENGLAND: Far East 9:30 pm. beam. 12 to 4:45 am. LEARN 9.730 XGOA CHUNGKING, CHINA; 122:30 to 1:45 11.720 CHOL MONTREAL, CANADA; European am: 5:30 to 10:15 am. beam. 2:15 to 7 pm. FAST... 8.735 CSW7 LISBON, PORTUGAL; 7 to 8 pm. 11.740 COCY HAVANA, CUBA; afternoons. 9.735 CXAI5 MONTEVIDEO, URUGUAY, 11.740 CE1174 SANTIAGO, CHILE: 7 am to 11:30 9.745 OTC LEOPOLDVILLE. BELGIAN CONGO: pm. relays ßßC at 8:30 to 11:45 pm. 11.740 HVJ VATICAN CITY; noon to 1 pm. LEARN 9.750 WLWRI CINCINNATI. OHIO; North African 11.750 GSD LONDON, ENGLAND: African beam. beam. 3:15 to 6 pm. 12 to 3 am; 10:30 am to 4 pm: 9.750 KCBF LOS ANGELES. CALIF.; South Amer- South American beam. 4 to 9:15 pm; RIGHT ican beam, 11 pm to 1 am; East Mediterranean beam. 2 to 3 am; 4 Indies beam, 4 to 9:95 am. am to 4 pm; North African beam. 9.750 WNRA NEW YORK CITY; European beam. 2 to 3 am; 4 am to 3:30 pm. at a Price You Can Afford! 1:45 to 6 pm. 11.760 V LG I O MELBOURNE, AUSTRALIA; 3:55 to Ghirardl'a RADIO PHYSICS COURSE makes 6.760 TGWA GUATEMALA CITY, GUATEMALA; 5:15 am. Radio -Electronics -Television amazingly easy to loam. evenings. 11.765 ALGIERS: 6 am to noon. in a 9.763 OTC LEOPOLDVILLE. BELGIAN CONGO; 11.770 KCBA SAN FRANCISCO. CALIF: South Everything is explained carefully and thoroughly relays BRC at 9:30 pm to 12:45 am. American beam, 11 pm to 1 am: 5 clear, easy style you cannot fail to understand No 9.785 OAXSC INCA. PERU; evenings. to 10:45 pm; Oriental beam, 1 to involved mathematics. No lessons to wait, for- No 9.800 H N F BAGHDAD, IRAQ: 9 am to 4 pm. 4:45 pm. North time lost. You get your training easily and quickly - 9.823 VIENNA, AUSTRIA; midnight to 2 11.770 VLA4 MELBOURNE, AUSTRALIA; American 12:10 am. ani: 6 to 8 am: 10 am to 4:30 pm. beam. to 12:40 while the big money -making opportunities still 9.825 GRH LONDON. ENGLAND; North Amer. 11.780 GVU LONDON. ENGLAND; Indian beam, beckon on every side. You'll be amazed to find how lean beam. 4:15 pm to 11:45 pm. 11 pm to 1:15 am; Australian beam. 11 to 1:15 am; European beam, soon RADIO PHYSICS COURSE has you familiar 9.833 COBL HAVANA. CUBA; 7:15 am to 12:45 pm am. 5 to 7:45 am; 10:15 am t04:15 pm; with every phase of this fascinating subject -how it African beam, 5:30 to 6:45 am; subjects that other books and 9.855 KWID SAN FRANCISCO. CALIF.; South 7:15 to 7:45 am; 10:30 am to 11 enables you to grasp Pacific beam. 2:30 am. to 6:30 am; 11:30 am to 1 pm. courses make seem highly complicated Best of all. MOSCOW, U.S.S.R.: 8 to 9:30 9.960 pm: 11.780 HP5G PANAMA CITY. PANAMA; daytimes you buy it on an UNRESERVED 5 -DAY MONEY - 10 pm to 2 am; 8:30 to 9:30 am: and evenings. 10 am to noon. BACK GUARANTEE. 11.780 MOSCOW. U.S.S.R.; 9 to 10 am. 9.997 WBOS BOSTON. MASS.; European beam. 01X3 LAHTI, FINLAND: 2:30 to 3 am; midnight to 3:15 am; 1 to 5:45 pm. 11.780 6 to 7 am: 8:15 to 8:45 am; 1 to Every cent of your money will be JOHANNESBURG. SOUTH 6900 ZTJ AFRICA; 5 pm: 5:45 to 6:13 pm; 8:15 to refunded if you are not more 7:15 to 7:45 8:30 pm. 9.915 GRU LONDON, ENGLAND; African beam, BRUSSELS, BELGIUM; 5:30 to 6 than satisfied. Send coupon today! 12:30 11.785 to 3:30 pm: 3:45 to 4:45 pm: pm; 8 to 8:15 pm. Indian beam, 11:15 am to 12:15 pm; European Mediterranean beam, 3:45 to 4:45 11.790 WRUS BOSTON, MASS.; beam, 6 am to 4:15 4:30 to 6 pm: North African beam, 12:30 to pm: pm. 3:30 11.790 KNBA SAN FRANCISCO, CALIF.: Philip- pm. pine beam, midnight to 3:45 am; 9.980 SVM ATHENS. GREECE; heard 1 to 6 pm. South American beam. 5 to 11:45 pm. USE COUPON 6.958 HCJ B QUITO, ECUADOR; afternoons and 11.800 GWH LONDON, ENGLAND: African beam, evenings. 1:45 to 2 am; 7 to 7:15 am; Canary at bottom of adjoining page 11.000 W W V WASHINGTON, D.C.: U.B. Bureau Islands beam. 1:30 to 1:45 am: of Standards; frequency, time and European bream, 1 to 2 am; 5 to musical pitch; broadcasts continu- 7:45 am; 10:15 am to 12 pm; 12:30 ously day and night. to 1:30 am.

550 RADIO -CRAFT for MAY, 1946 REPAIR RADIOS EASIER AND TWICE ASTAST?' This Big 4 -lb. Manual -size Radio Troubleshooter's Handbook Shows Exactly How to Diagnose and Repair Common Troubles in Practically Every Radio in Use

A repair data Handbook that goes to work for you NOT A STUDY BOOK! the minute it arrives! Speed up radio repair work! Eliminate radio to be repaired. Four times out of much needless, tedious testing! Handle five, the HANDBOOK will show you step common radio troubles fast and profitably. by step just what to do-in a fraction of the Make spare time money repairing sets- usual time. Ideal for either busy repair shops without costly equipment or experience. or beginners. Paya for itself in time saved on the very first job. MAKE MORE MONEY- FASTER! Over 300 additional manual -size pages in- Ghirardi's famous 744 -page, manual - clude service hints; i -f alignment peaks for size RADIO TROUBLESHOOTER'S over 20,000 superhets; transformer trouble HANDBOOK shows you what to do-ex- data; the most complete tube information LET GHIRARDI TEACH YOU THE actly how to do it. Over 400 pages give you've ever seen; color codes; and hun- "SECRETS" common trouble symptoms, their causes dreds of graphs, diagrams, charts, etc. OF MAKING REAL and remedies for over 4,800 receivers, all carefully Indexed so you can find what- auto radios and record changers of 202 you need in a hurry. Price only $5-on MONEY IN RADIO SERVICING. different manufacturers. Just look up the 5 -DAY MONEY -BACK GUARANTEE Eliminate much needless testing! Repair two Make, Model and Trouble Symptom of the BASIS. See Money- Saving Combination. sets in the time normally required for one! BE A PROFESSIONAL RADIO - ELECTRONIC SERVICING EXPERT

Let Ghirardi Scientific Training Prepare You for the Big Money Class! MODERN RADIO SERVICING is Alfred A. Ghirardi's famous 1300-page 1- volume course in PROFESSIONAL radio - electronic service work. It gives the kind of training that will MONEY -SAVING be your "Open sesame!" to the better money- making opportunities that only scientifically trained servicemen will be in OFFER! a position to grasp- including profitable industrial electronic work. It explains all types of test instruments. Shows how Let RADIO TROUBLESHOOT- to analyze circuits professionally; how to use all types of ER'S HANDBOOK save time test equipment for troubleshooting; how to test, repair and on common service jobs. Let replace components; how to make substitutions-how to handle MODERN RADIO SERVICING every phase of radio repair work from A to Z by approved train you for professional radio - MODERN methods. Absolutely "tops," either as a basic course in the field electronic service work. Get entire of radio -electronic servicing, or as a "refresh- BOTH big books at special er" on any type of work that puzzles you. Worth its weight in gold in giving you real Know -How and paving your way to a Money-Saving Combination price A V profitable radio- electronic- television servicing future. 1300 pages; of only $9.50 for the two. Act at 706 illustrations; 720 self -test review questions. Only $5. 5 -DAY once! Send coupon now! MONEY -BACK GUARANTEE.

LEARN ALL ABOUT ELECTROLYTIC

CAPACITORS MURRAY HILL BOOKS, INC. Dept.RC -56, 232 Madison Ave., New York 16, N. Y. Don't buy, specify, use or replace :1 Enclosed find i for books checked; or send C.O.D. (no foreign capacitors blindfolded! They are among C.O.D.'s) for this amount plus postage. If not fully satisfied. I may return the most important components in radio - brooks within 5 days for full refund. electronic equipment. Read Alexander D RADIO PHYSICS COURSE RADIO TROUBLESHOOTER'S M. Georgiev's book, THE ELECTROLY- (See adjoining oage) HANDBOOK TIC CAPACITOR and $5 ($5.50 foreign) 55 (55.50 foreign) learn the facts! THE ELECTROLYTIC CAPACITOR El MODERN RADIO SERVICING Tells all about the various electrolytic $3 ($3.25 foreign) $5 (55.50 foreign) types . their construction, character- MONEY -SAVING COMBINATION OFFER: Both Troubleshooter's istics, advantages, applications, measure- Handbook AND Modern Radio Servicing. only $9.50 for the two ($10.50 foreign). The only mod- ment, testing, defects, making emergency repairs, etc. Shows when and where ern book of its to Name kind. Profuse- use the various types; describes wets 8 ly illustrated. versus drys; applications at low and high Address voltages and frequencies; a -c or pulsating d -c uses; ambient conditions, etc. Over C iq- and District No. Stale 200 pages. $3 ($3.25 foreign). Use coupon.

YOU'LL NEVER GO WRONG ON A Ghirardi BOOK.

RADIO -CRAFT for MAY, 1946 551 CODE OSCILLATOR EMERGENCY B.F.O. RADIO-CRAFT welcomes new and orig. In the middle of a code practice ses- It is possible to obtain the tone of an inal radio or electronic circuits. Hook- actual c.w. station by connecting your ups which show no advance on or sion my beat- frequency oscillator failed code practice oscillator to the input of advantages over previously published to work. Having a small home receiver a phono oscillator. The signal is then circuits are not interesting to us. Send on a nearby table, I tuned it to the high picked up by a receiver in the same in your latest hook-ups- RADIOCaAFT frequency end of the broadcast band. It manner as an ordinary recording would will extend a one -year subscription is possible to pick harmonics from the be. for each one accepted. Pencil diagrams oscillator of the broadcast set. These -with short descriptions of the cir- harmonics can be made to beat with the cuit -will be acceptable, but must be of on -sized sheet. incoming signal the communication 1 1\7F7 clearly drawn a good receiver thus making the unmodulated TI -.... signal audible. V POWERLESS INTERCOM For example, it is desired to beat a IAC I) -+Nb A good intercommunicator, for short signal with an incoming signal of 9.5 distances, may be made without using megacycles. The broadcast receiver is BELL TRANS batteries or switches. tuned to approximately 1130 kilocycles. T tx. Two 3 -inch PM dynamic speakers It will then be possible to make the sixth are connected to output transformers harmonic of the oscillator beat with the TO PHONO OSCILLATOR (500 -ohm to voice -coil) and the pri- 'FROM PHONE CONNECTION) incoming signal. mary windings of the transformers When using the b.f.o. to search for a by line. With many types of phono oscillators, connected together a station, it is necessary to know the exact By speaking into one of the speak- frequency of the station being sought. it may be necessary to connect a re- a voltage is of 50 to 100 thousand ohms across ers, from a short distance, S. A. WHITT, sistor set the voice stepped output of the code unit to bring up within coil and Princeton, W. Va. the up on the secondary. It is then passed the B voltage to the plate. A by -pass NOVEL POWER SUPPLY .005 should be ORDINARY 500n LINE TO VOICE COIL TRANS. condenser of about µf A center-tapped output transformer used across it to pass the r.f. current may be adapted for service as a power or in many cases the tube will not os- transformer by using it in the manner cillate. it ill 3 "PM SPEAKER 34P M SPEAKER described in the circuit. A series condenser of about .05 tf is The primary of the transformer is usually necessary to prevent d.c. from through the primary of the other trans- used as a center -tapped auto- trans- being applied to the grid of the first former and the voice coil is excited. and the high voltage output is in former tube the phono oscillator, depending This works remarkably well with the fed to the plates of a OZ4. This tube on the circuit. new high -efficiency speakers which use was selected because it does not require JOHN WINKLER, Alnico magnets. cathode heating voltages. The filter sec- Big Rapids, Mich. E. A. CHAPMAN, tion is the conventional "brute- force" Alberta, Canada type and with the values specified, it is WINDING INDICATOR possible to get 220 volts d.c. from the An old "Readrite" or similar moving - SIMPLE WIRE GAUGE output. vane type of meter, or one that has a A handy wire gauge may be made by burnt-out winding can be utilized as an mounting wire of various known sizes excellent test meter to differentiate be- on a piece of 12 by 8 inch white card- OUTPUT tween the various windings of a power board. The wires may be held on the TRANS PRI. transformer. Some transformers are not board by small strips of cellulose tape. C.T. coded in accordance with RMA specifi- The size of the wire is noted just below 5+220V the test strips. When it is necessary to 117V AC cations. 16 16 To test, the meter is simply laid on top determine the size of a wire, it is held of the core of the transformer. Then side by side with the test strips until T35ov T s_ each winding is excited by connecting the two sizes are matched. the leads to a 1.5 -volt dry cell. There JOHN TREBYCH, JR. The turns ratio of some transformers will be only a slight deflection when the Fruitland, Ont. is such that the voice coil will yield a high -voltage leads are connected, but (This method is actually as accurate usable voltage which may be applied the 5 -volt and 6.3 -volt windings will in- as a standard wire gauge for measuring to heat filaments. Using a heavy trans- dicate approximately half -scale deflec- the smaller wire sizes. Editor) former designed to work into several tion. The 5 -volt winding will read slight- output impedances, it may be possible ly higher than the 6.3 -volt winding while TWO SHORTWAVE KINKS to find some combination where stand- a 2.5 -volt filament winding will read A music stand base makes a FB an- ard filament voltages are available. highest of all. With a little practice and tenna for either 2% or 11/a meter bands, IRWIN STELZER, some sort of calibrated chart, the set- giving directional characteristics in Yonkers, N. Y. tings for each winding can be discov- three directions. If legs are adjustable, ered. It will then be possible to deter- experiment to find resonant length. Ap- FLUORESCENT UNIT mine whether any windings are shorted proximately 14 inches is a half-wave at_.. - -- A portable or mobile fluorescent lamp partially 6r completely. 21/z and a quarter-wave at 1% meters. can be made by connecting the fluores- It would not be advisable to use a A five -cent pyrex bowl makes a good cent bulb across the high -voltage sec- meter that is still in regular daily use, feed- through insulator. Drill through, ondary winding of a 6 -volt vibrator as the intense magnetic field developed using low pressure drill and light oil for pack. The battery I used was a car may cause a change in the meter magnet lubrication. Total cost is twenty cents battery. The vibrator pack was from which would cause inaccuracy in future compared to about $3.00 when pur- an old auto radio. The 20,000-ohm re- voltage readings. chased complete. sistor is an adjustment for maximum PETER R. HEATH, GERALD SAMKOFSKY, results. SANTOS TIJERINA, Stettler, Alberta Brooklyn, N. Y. Billing, Texas

552 RADIO -CRAFT for MAY, 1946 N:U SAVASHAFT

UME CONTROLS

s, ve work...time...material

Two simple operations give you eight big advantages With only 10 types you handle 1. Cut shaft off old control 95% of all control replacements 2. Insert shaft in bushing of new Say -a -Shaft control Try Say -a -Shaft and see f91 yourself how much No stock problem easier they are to install. Learn about their No replacement headaches velvety smooth operation, quietness, Eliminates shaft and size and knob fitting long life. problems Note the convenience and profit in handling Any standard shaft adaptable to these controls ractically all replacements with only 10 types. Each control complete with Switch (switch Oráér an assortment today from your N. U. operates only when lug is released) Distributor. Prompt delivery assured. Easily installed in those hard -to- get -at chassis All midget size for simplicity NATIONAL UNION RADIO CORPORATION Gives you tapped controls where Newark 2, New Jersey needed

Trsnrini.p Gtbo/r Rey, R.rfiri.r, Special Prrp.r. Triter Co.Ànu.g CwFñL Pima Electric G/4 P.nrl Lyi P1.,66g6t Bra,

RADIO -CRA FT for MAY 1946 553 TECHNOTES

ZENITH 8S458 This set was tuning very broadly with low volume. A check of the plate and screen voltages showed these values to be low.

* for Style .05

REPLACED WITH 600K COND. The socket of the 1232 r.f. stage is not * for Dependability immediately available for testing as it is mounted on a sub -panel. Upon dis- mantling this circuit, it was found that the screen by -pass condenser was leaky. * for Performance This was replaced with a .05, 600 -volt unit. As a precautionary measure, it is wise to replace the a.v.e. by-pass condenser that will be found on the same assembly. J. &IMRIN, Bronx, N. Y. Model 22 Microphone Gives You All Three . . SHORTED I.F.'S in- the When shorted i.f. transformers are There's sore than beauty of styling behind dicated in sets using shielded units, set Turner 22 Microphone. This famous member of the the set upright and jar slightly to dis- Turner Line is a precision unit - engineered to faith- lodge any small washers or bits of solder fully reproduce every desired sound without har- that may have found their way into the monics or distortions - ruggedly built to perform trimmer condenser assembly. with unfailing dependability under difficult operating If shaking does not remove the trou- conditions. Good reason why so many leading ble, remove the shield before discon- manufacturen of electronic recording and communi- necting the windings from the circuit. cations equipment specify the In many cases, the short is within the and not the trans- Turner 22 as standard for maxi- trimmer condenser former itself. A surprising number of mum performance ... why you "shorted" i.f. transformers can be want the TURNER 22 for cleared up In this way. your equipment. Available in CARL V. FISHBACK, both rugged crystal and dy- Hillsboro, Oregon namic models. Ask your dis- These Features You Gete 22 tributor or write for complete PUSH BUTTON RCA AND GE the Turner A frequent complaint on all RCA and in Proofed performance characteristics. of Moisture GE receivers using separate solenoids * Choice Dynamic Crystal or Rugged for each pre -tuned station, is that the cannot be tuned Cartridge. Semi- or high frequency solenoids for Licensed 1500 kc. * 90° Tilting Head pera flan. Turner Microphones above Non-Directio Under U. S. Patents of the American Removing one turn of wire from each C abi Telephone and Telegraph Company, in the * Removable of the solenoids question will cure Compensator. and Western Electric Company, Inc. trouble. * Barometric Proofing. HUGH A. MCCCRMICK, * Mechanical -Shock from Close Montreal, Canada * No blasting Free Turner Catalog Speaking. . PHONO OR TONE SWITCH * Low Feedback. Occasionally a radio serviceman is Performance. Write for your copy *Certified called to install a tone control or phono ji_'ll on a radio set that was not equipped with one originally. The problem of mounting the control or phono -radio switch without disturbing the symmetry of the other controls is not always a simple one, and practically all customers want their control on the front panel. The TURNER Co. If the set is equipped with push but- 902 17th Street N.E., Cedar Rapids, Iowa tons of the "electric" type, (switch with Pi in the communications field separate tuned circuit for each pushbutton), it is a simple matter te dis- connect the leads from one pushbutton switch and use this switch for a two position tone control or for a phono -radio switch. HUBERT WATKINS, Under Patents of the Brush Development Co. Crystals licensed Gulfport, Miss.

554 RADIO -CRAFT for MAY. 1946 FM radio receivers are more static -free and less costly - thanks to research at RCA Laboratories.

NEW FM - noiseless os the inside of o vacuum tube!

Now, FM, or Frequency Modulation is no longer expensive! "Better things reception, provides still greater free- at lower cost" is one of the purposes dom from static and interference of RCA Laboratories - where similar caused by storms, ignition systems, oil research is constantly going into all burners, and domestic appliances. RCA products. It's radio at its finest - making your And when you buy anything bear- living room a part of the concert hall RCA Victor name from a ing the - Manager of idea of how marvel- Stuart William Seeley, itself. You've no television receiver to a radio tube re- the Industry Service Laboratory, ous music can sound over the radio placement -you know you are getting RCA Laboratories Division, perfect- until you hear the golden perfection one of the finest instruments of its kind ed this new FM circuit. It not only of FM reception developed by RCA. that science has yet achieved. operates egdally effectively with but lowers Moreover, through this new RCA strong or weak stations, Radio Corporation of America, RCA Build- the cost of receivers by eliminating development, FM receivers can be ing, Radio City, New York 20. Listen to The additional tubes and parts that were made at a cost comparable to that of RCA Victor Show, Sundays, 4:30 P.M., East- formerly considered necessary in standard -band broadcast receivers. FM ern Standard Time, over the NBC Network. Frequency Modulation receivers.

RADIO CORPORATION of AMERICA

RADIO -CRAFT for MAY, 1946 555 I ell TELEVISION AND ELECTRONICS

0Z) ON) hg e ctOeA ;ÑIPL&PNOtS a t91 cut GNpRtS

38 BIG CHAPTERS Easy to Road -Easy to Grasp -Easy to Apply A home -study course-especially well organized. The style is so interesting you will read along without effort, hardly realizing that you are actually studying and taking in vital information. Audels Radiomans Guide gives you just the right amount of mathe- It gives you usable formin matics required to cope with radio pointers on radio, problems successfully. You can solve, including fre- of extraordinary book, quency modula- with the aid this tion, television, practically etc. Also valuable QAND every radio prob- inside information A for Aviators, Ma- lem that comes rines, Commercial up. At your fin- Operators and UNIQUE Technicians, Serv- ger tips is a icemen and Stu- QUESTION complete index dents. and for instant use. ANSWER . METHOD t tA . Highly Endorsed ts s os b 0 11 tott stie y c . CO' Guti °p a, w tir 1001 RADIO FASTS AND 'FIGURES ` °ti 4 AUpasti° ct.$,p8:t A Complete Library In One Book tc AUDELS RADIOMANS GUIDE gives authentic Princi- , tgF e9t 23 ples and Practices in Construction, Operation, Service oS `tiò and Repairs. Covers clearly and concisely radio fundamentals -Ohm's Law- Physics of sound as related to ` ti P Gtib radio science -Measuring instruments -Power supply - `ttGyQJ Resist ors - Induc tors - Condensers - Transformers and SA` examples-Broadcasting stations -Radio Telephony -Re- ceivers - Diagrams - Construction - Control Systems - Loudspeakers - Antennas - AutoRadio - Phonograph Pick- ups -Public Address Systems-Aircraft and Marine PJJt6 Radio - Radio Compass - Beacons - Automatic Radio COMPIETE pJ° 100 Alarms -Short Wave-Coil Calculations-Testing -Cath- ode Ray Oscillographs - Static Eliminations - Trouble ovóo Pointers - Underwriter's standards - Units and tables. REVIEW QUESTIONS -READY Reference Index. 00` toa 556 RADIO -CRAFT for MAY, 1946 CORRECTION NOTICE

Due to a typographical error the advertisement, LEEDS RADIO CO. Page 580 should be corrected as follows:

BC -603 Tank Receiver ... Price $25.00

NOT $5 AS PRINTED

RADIO -CRAFT MAGAZINE

3ltabío Mbírtp-jfíbe rums Sgo In ßtrnsback fiublitations MICR GERNSBACK Founder

Modern Eleetrics 1903 Electrical Experimenter 1913 Radio News 1919 Science & Invention 1920 Radio -Craft 1929 Short-Wave Craft 1930 Wireless Association of America 1909

Some of the larger libraries In the country still hay copies of Modern Electric' on fife for Interested readers. From the May, 1911, issue of MODERN ELECTRICS: Eiffel Tower and Time Signals. 4,70.. Wireless Efficiency Test. Rotary Spark Gap. ,...ä. A Silicon Ticker, by Stanley Hyde. Three Slide Tuner, by William S. Wilder. Foot -Operated Aerial Switch, by Clift R. Richards, Jr. Aerial Mast, by John W. Gundy. Tuning Coil for Fine Adjustment, by Harold Hermann. PROOF CONVERTS A DOUBTER Plate Glass Condenser, by Ethan We admit Clarke. that our advertising of "VOMAX" describes the "one and only" . . . A Simple Loose Coupler Frame, by a v.t. multi -meter so new, so modern that it tops the list. Yet we know our each F. W. Doty. and every statement to be hard fact. Writes a converted "doubter ": - Universal Detector, by Edward . I would not Hutchinson. part with VOMAX for any money . , I read with considerable A Break Key, by Dick Cuthbert. interest your articles in July and August 'QST,"'Taming the Vacuum Tube Voltmeter.' Your claims as to this instrument's ability as Mounting Crystals, by Chester W. a Dynamic Signal Tracer were taken with a grain of salt, however, because I had considerable experience using the vacuum-tube Scherf. voltmeter as a signal tracer and in most cases results were far from used the 'VOMAX' satisfactory. I have A Detector Switch, by Walter Trost. as a signal tracer on several jobs and am more than pleased with the results ... I was also pleased to find the instrument so stable and free A Ground Block for Wireless, by R. This stability was of zero shift. another of your advertising claims which I took with a grain of salt. S. Crawford. (Signed) A Satisfied Serviceman, Clarence F. Hartzell, Altoona, Penna." An Experimental Wireless Telephone, by H. W. H. If that isn't proof to the hardest boiled technician, may Adjustable and reorder we mention "VOMAX" order Condenser -for Sending by the U. S. Bureau of Standards? And as a clincher, you know that when Only, by Jay Jakowsky. your jobber is enthusiastic, it's because he has something Say of real value to you. A Silicon Detector, by all eight New England stores of Hatry & Young; Radio- Wire -Television; Clarence Bal- & Appliance Radio Corp. of Nashville: "We and you, our customers, have waited a mighty lard. long time for 'VOMAX' -it's more than we expected." Watch Say Radio -Case Wireless Outfit, by Wil- Equipment Distributors, Los Angeles; Burstein -Applebee, Kansas City; liam Dettfner. Walker -Jimieson, Chicago; Mac's Radio Supply, Southgate, Calif.; New York; Arrow Electronics, Multiple Detector Stand. Rhode Island Distributing Co., Pawtucket; Lew Bonn Co., Minneapolis and St. Paul; Wholesale Radio Laboratories, Council Bluffs; Wireless Across the U. S., E. A. Terminal Radio, New York; by Newark Electric of Chicago and New York; Lukko Sales, Chicago; "In our critical Mayne. opinion these features establish 'VOMAX' as standard of comparison." To tie the knot of acceptance and superiority even tighter, Bendix is now recommend- 9 ing "VOMAX" to all BENDIX RADIO distributors and dealers 9 WHY NOT ? 9 service. to insure top -flight Your favorite jobber can probably squeeze your "VOMAX" Have you ever asked yourself, "Why out of his monthly allot - ment-if you act fast . . . while it's still only $59.85 net. can't I have this or that gadget on a radio? Why aren't programs made to fill such and such a need ?" If so, you Send postcard for complete specifications of OVER 34 YEARS OF RADIO ENGINEERING ACHIEVEMENT are a charter member of the Radio - "VOMAX." new 904 Capacitance - Resistance Bridge, Craft "Why Not" club. Send us your 905 "SPARX" and other new, post -war. SILVER 74'9,4*44s:4e4, "Why Not's" on all subjects- serious or measurement and communication products. See them cpArbo7, May 13 IS. MO MOO araen. screwball, practical or idealistic. We at the Chicago Trade Show. through ...WORD a. CoaaECtKYr will pay $1.00 for every one we believe will interest making tuning impossible. There is room phono when one or the other is in use, the readers of Radio -Craft. for them in most cabinets -cost would be You can get the idea from the "Why so that extraneous noises would not be small, and they could be used as a support picked up. Not's" printed below. Send in as many for loops, etc., if an excuse for them is as you like. One dollar will be paid for necessary.-Charles McClcskey, Jr., Baton JOHN WILLEY, each one printed. Rouge, Le. Montpelier, Vermont (Some Signal Corps equipment was Why not put covers on all trimmer con- manufactured with this feature during the Why not design a universal radio re- densers with a special keyed device for war. Editor) ceiver with plug -in power supplies opening so that only the serviceman could which can be purchased with this "sin- open it. This would prevent the customer Why not have a pickup and mike in gle model" receiver? from "tightening those loose screws" when Five different types the radio stops playing. -J. H. Meyer, one? When used as a mike, it could be of power supply could be purchased; a Metairie, La. held in the hand and when used as a dry -battery supply; a vibrator supply pickup, could fit to be (Seriously, the "sealed- unit" idea may be it into brackets. The used with a 6- or 12 -volt storage developed by some receiver manufacturers, top part of the pickup could have a battery or 32 -volt farm unit; an a.c: d.c. especially for the new ultra- midgets.- screen on it the same as an ordinary supply for 117- volts; a supply for 110- Editor) mike, while the bottom could be made 220 volts at 60 cycles; and a supply for Why not build all radios with built -in just as the regular phono pickups are 110 -220 volts at 25 cycles. chassis brackets so they could be inverted made. A switching arrangement could PVT. JOHN R. SIMPSON, on the bench without endangering parts or be provided to shut off the mike or Ft. Meade, Md. RADIO -CRAFT for MAY, I 9 4 6 557 11.1 51IIIIIIIIIIIIIIIl11111111I11111IIIIIIIII1111111111IIIIIIIIIIIIIII111111IIIin11III1i11: III11111111111IIIIIIIIIIIIIII1111111IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII111111IIIIIIIIIIIIIIIIIIIIIIII1

The Question Box is again undertaking to answer a limited number of questions. Queries will be answered by mail and those of general interest will be printed in the maga- sine. A fee of 50c will be charged for simple questions requiring no schematics. Write for estimate on such ques- fions as may require diagrams or considerable research.

°, Illl munnmmmmnunlllmnunsiximnmunno unman wnoixis a ixim nnnm imam ununnuirmumunomi iim i mna

have to be replaced by a 750 -ohm, 20- heavy -duty power transformer should watt, wire -wound resistor. be used. The circuit is shown below. TUBE and output trans- REPLACING THE 183 The same sockets ELECTRONIC METRONOME former may be used. receiver using I have a Sparton to see diagram of an in the power ampli- HI -FI TUNER -AMPLIFIER ? I would like a push pull 183 tubes metronome that would be fier stage. I would like to replace these i] electronic type. I would like a diagram of a two suitable for timing purposes and that tubes with some more common easily in the number of advise what tubes to use and stage r.f. tuner working into a hi -fi could be varied Please out- beats per second or minute.-F.B., De- what changes are to be made in the set. amplifier with 6A5 -G tubes in the -J.J.M., Buffalo, N. Y. put. The amplifier is to have micro- troit, Mich. phone and phono input circuits.-J.A.J. A. The diagram shown should meet -Goldsboro, N. C. your requirements. It is essentially a YELLOW A. The tuner uses a 6D6 as a t.r.f. multivibrator or relaxation oscillator / stage feeding a 6C5 detector. It is de- and the beats may be made to vary from signed for local reception and is not twenty per minute to above 100 kc de- o enough for distant reception. pending upon the circuit constants. 27 VOICE sensitive 45-i COIL A 6C5 is used as first a.f. stage and It is obvious that if the beat -rate is works directly from a phono pickup or more than a few beats per second, they a will appear as one continuous tone and 80 s YELLOW the tuner. A 6J7 is used as preampli- A' fier for the micro- SPKR phone. Dual tone I°OK IoOK +IK+ 265.. FIELD 6J5 .20- LINE controls are incor- s \ .5 CORD CHOKE 2500n o- porated in the grid / \ circuit of the 6N7 ÑÑ i5 T5 phase inverter. z e O A signal of 2 á 3 is re- .0+1/0 4Qi aka, 0 Q, 750 volts (peak) 20W SW grid o--i 25Z5 quired on the 3MEG 3 MEG 25Z6 fimP u7V.AC of the 6N7 for full output. It may be Widely varying frequen cies can be produced by the multivib ator. How Sparton I83's can be replaced with 45's. necessary to change be used as a code be replaced by a the tone control somewhat if the voltage then the device may A. The 183's may oscillator by keying the cathode pair of 45's. Since the 45's operate with is low on the grid. Instead of changing practice be in- of one of the tubes. 2.5 volts on the filament of each tube, it the tone control, another 6C5 may circuit the filaments in serted just ahead of the first a.f. stage. High impedance headphones are con- is necessary to connect in the circuit and the them work from the 5 The plate -to- cathode voltage of the nected as shown series to make of the device may be fed into an volt filament winding that was used by 6A5 is 325 volts and for full output, the output output of the power supply should be amplifier by placing the amplifier input the 183's. into metronome phone jack. The present cathode bias resistor will 375 volts. Low -resistance chokes and plug the

6C5 .25 008 (2)6A5GTS RADIO SW o-' 250K PHONO .0005 i -o,MIKE 5 ME 500K 250K VOL. - i CONT. 004 -5011 50K - 5Kn 150V PL.TOPL.

TO le 6N7 PM SPKR 250V e .1 FOR PHONO PICKUP 500K e 6SJ7 - 3750 300V SK (SHIELDING .005 + 8 r- t_ ----- _

FOR 2MEG 10 MEG MIKE i - B + e L 350TO 375V -CRAFT for MAY, 1946 558 RADIO RADIO INDUSTRY UNFAIR? (Continued from page 529) In this NEW WORLD

is it to the ex- serviceman to obtain a dealership or an agency on paper if he OF ELECTRONICS- cannot get the sets? As this is written at the end of March there is only a single, solitary radio set manufacturer in the U. S. who produces 100,000 units, i.e. (radio sets), per month. It should be remembered that before the war a normal month's production in radio sets ran at least into 1,141,600 units *. From 1 /wi, this it will be seen that a mere 100,000 t 4 - \ sets, the top production by any one maker at the present time, is a drop in the ocean. Right now radio sets simply NEW DEVELOPMENTS are not being produced in pre -war numbers, let alone to fill post -war expecta- SPELL tions. /rowO,D' afili As go to a by we press statement CIRE HOME STUDY COURSES COVER the president of the largest radio set THE FIELD OF RADIO- ELECTRONICS manufacturer in the country, Philco, -TELEVISION, ULTRA -HIGH FRE- reaches us, from which we quote the A FEW YEARS AGO broadcasting was QUENCY TECHNIQUES, AM AND FM born of first BROADCASTING, COMMUNICATIONS following passages: -many the radiomen to ENGINEERING -from simple treatment "But it is necessary to report that enter that field have long since arrived of fundamentals, through preparation for due to conditions beyond the control at the top of their profession. FCC commercial radio operators' license examinations. up to and including com- of the management of this or any TODAY, the techniques of this New plete high level quantitative treatment of other single company, our produc- World of Electronics, war -developed and advanced radio -electronics and communi- tion remains at an unsatisfactory only now released, offer greater oppor- cations engineering. Choose the course level and is much lower than our best suited to your needs, and start with tunities than ever existed in the early the section you are qualified to enter. You schedules called for. One of the days of broadcasting! pay for only the section or sections you chief bottlenecks at the present time need. Use the "Pay -as- you -go plan" pat- is the fact that price ceilings on MICRO -WAVE RELAY SYSTEMS, TEL- terned after ethical, educational practice. These features are unique with Cleveland many radio parts and components EVISION, FM broadcasting, mobile com- Institute, and represent the best in the are such that our suppliers are un- munication systems for trains, automo- modern. post -war concept of home study able to provide us with more than biles, busses and trucks, many industrial training. a fraction of our requirements. A applications -these are only a few of the Many CIRE students of advanced engi- second major drawback has been a neering courses today are broadcast chief new developments and new techniques engineers. Graduates of CIRE courses are series of strikes in suppliers' plants which offer marvelous, exciting oppor- eligible for the top jobs in radio -elec- which have also interrupted the tunities to you who are alert -and are tronics. flow of parts and hampered Philco qualified! production. "The solution of these problems YOU HAVE THE OPPORTUNITY to depends on the formulation of sound "get in on the ground floor" -where policies at the national level, and it promotion will be rapid -where you can is hoped that progress in this direc- go to the top, IF -you have the foundation will soon be forthcoming." tion of technical knowledge which is so The statement, signed by John BaIlan- vital to an understanding of the new tyne, President, is dated March 12, 1946. techniques. Your first step toward suc- Other radio set manufacturers in are cess in this new world of electronics is a like position. They have few, if any, your resolution the to acquire a formal, sets at present time. The late steel fundamental technical and other strikes did not make the al- knowledge. CIRE ready bad conditions better. Indeed, they courses of home study training are planned to do that job. Mail the Write today for free, descriptive booklet. "THIS caused further unexpected delays. coupon NEW WORLD OF ELECTRONICS HOLDS OP- today! PORTUNITY FOR YOU." No obligation -no sales. Our personal guess is that there will men. not be an abundance of radio sets in 1946. CLEVELAND INSTITUTE of RADIO ELECTRONICS We are certain that by the end of Contractors to the Canadian this year when Broadcasting Corporation. the set manufacturers Successors to are getting into their full stride, and NILSON RADIO SCHOOL, Founded 1939 particularly when the new crop of set SMITH PRACTICAL RADIO INSTITUTE, Founded 1934 manufacturers begin to look for outlets in earnest, that the ex- serviceman, if RC- 5 TERMINAL TOWER - - - - CLEVELAND 13, OHIO he is at all deserving, will get his right- MAIL THIS COUPON. ful share of the radio business. The important point that we wish to CLEVELAND INSTITUTE of RADIO ELECTRONICS I desire training in make here is that the ex- serviceman RC -5 Terminal Tower, Cleveland 13, Ohio Gentlemen: Please send Information about > our home I have had experience in broadcast- should make himself thoroughly ac- study courses In Radio -Electronics. quainted with ALL of the conditions ing O servicing operating O prevailing in his industry. He cannot NAME mfg. O CAA O Army -Navy D act intelligently until he has gathered amateur O other ADDRESS all the facts. Believe us, there are many i am a High School Grad O angles to be considered during the pres- CITY College Grad O ent hectic days. I hold a degree in ZONF STATF- *Nearly 14 million sets per year. In 1941 there were produced 13,700,000 units.

RADIO -CRAFT for MAY, 1946 559 FOR EVERYTHING IN RADIO CLAMPING CIRCUITS (Continued from page 542)

w9C vent high (plate) voltage being applied of their relative amplitudes and wave ¿3O, to the sensitive plates of the cathode - shapes. ray tube. But when the signal passes Clamping is also used in the sweep For fd through such an isolating condenser, the or time base circuits of cathode -ray st volt- signal loses its d.c. component and the oscilloscopes. If co- phased sweep reference axis immediately becomes zero. ages don't always start from the same DeliVerye Unless a new reference level is pro- reference point (in time), the resultant iiet Leo's own. personal. sodden the same place lenire on you radio and eiert mole vided-by a suitable circuit-the signal trace will not begin at seeds. Quirk dubiety, lotvct will Shift of its own accord so that the on the scope screen each time a cycle is e s, literal trade-in allowances. zero reference (or time base) appears repeated. Result would be a jittery and through the average center of the wave. quite erratic trace. Use of a clamping and 1EEDS That is to say, with the d.c. component circuit- between the final amplifier SH;61JIlE 11E41111 gone, the area of the wave above and the deflection plates of the tube -per- below the base line becomes equal. This mits easy regulation of the start of the WRL MULTITESTER is an inherent characteristic of most sweep trigger voltages. Steel ease with cathode -ray oscilloscopes. Often clamping is used for both the 30 -60 qe 19' 7 5 1 cathode cat. No. 10.401$185 To supply a new reference level, a signal and the sweep voltages of Leads .. Less clamping circuit is inserted between the ray oscilloscopes. This is of particular deflection importance in many radar circuits to Handles :%C lac Voltmeter. DO Millismmeter, high and loo coupling condenser and the nnge Ohmmeter. 3" meter with sturdy D'Aronnal movement. plates of the cathode -ray tube. ensure complete independence of signal Size 5%s8s3%. and time base shift. A complete stork of tools, replacement pans. test equipment, In a typical radar indicator cir- intercom and publie address systems .. , everything for the is used to Clamping permits the elimination of progressite sen ice dealer. cuit (Fig. 8), a diode Dl clamp the positive extremities of the signal to a given reference level. All PHONO AMPLIFIER KITS target or other in- Complete with tubes, speaker, stomped dications on the chassis. and all resistor and condens- en tube will appear as 3, ea. Cat. No. 7-271 ...... 59.50 ea. Lots of downward deflec- Crystal nets. Antenna Kits. Code Oscillator Kits. Transmitter tions with respect -3000B +B radio Kits, and many other items for the experimenter and enthusiast to t h e reference Fig. 9-This television output system uses a peak clamping diode. axis. During the time negative portions of low- frequency portions of extremely the original signal are passing through complex wave shapes -such as are en- FEMME clamping circuit, diode Dl does not countered in video stages of television the not Transmitting tubes, condensers, mikes function. When positive portions of the circuits. These low frequencies are .. everything for the Ham. One of and the final tele- the country's largest storks of Ham signal are applied to the circuit, the particularly desirable, equipment. Write Leo, WOGFO, to- vision picture will not suffer appreciably ay. and be first with the latest. We diode conducts, acting as a short circuit. Imite inquiries for special equipment by their loss. of all kinds. Charge on the condenser Cl maintains a balanced clamping circuit. In this way Clamping circuits are also used in a fixed a d.c. component of the wave is restored television to hold blanking at or reestablished. potential -generally at the control elec- Another diode D2 is used in the radar trode of the picture -tube. One typical indicator circuit of Fig. 8. Second diode For peak performance and more dollar for dollar value, gel a WRL is used to clamp voltage impulses ap- in SIGNAL INPUT c Ti ansmitier Klt . . designed tube. Leo'ss own laboratories . tested plied to the grid of the cathode -ray and proteo. Available in 15, 35, 70, as brilliancy pulses, and 150 wall kils as well as kits ens- These are known Wm built to your own specs. Write and are miniature (power) versions of Leo today for complete deists, prices and terms. the original signal. Applied to the grid of the oscilloscope, these pulses cause the tube to become bright or brilliant only when a signal is actually during periods R2 Here are lust a few of the many well - applied to known receivers offered by Leo: being received and is being 250K Hallienners SX-25 S 94.50 the deflection plates. Such brilliancy Hallicefters 5.209 S 60.00 Hallieraften SX -28A $223.00 might ruin the tube unless re- pulses 'SYNC. Ectmphone EC -IA S 29.50 so the peaks aammariund HP-129X $129.00 stricted in voltage that VOLT. National NC-2 -40C 5225.00 never exceeded a certain, safe, reference INPUT If Write for details of our trade-In plan D2 is to wia easy terms level. Purpose of the diode s ply this needed restriction in combi- Fig. 10- Synchronized bridge clamping circuit. FREE! 52 PAGE FLYER nation with the long time constant (RC) electronic. in 9. Values 52 pages packed with real buys in radio, composed of condenser C2 and resistor arrangement is shown Fig. and general merchandise. R2. Operation is identical to the positive of condenser C and resistor R have a Giant Radio Map (size 31,¢'x4%') 150 clamping circuits described earlier. I d time constant compared with the Handy Tube -Base Calculator 25C Clamping also makes possible the line- scanning interval. But the product Address Dept. RC -5 application of two signals to a single RC will be short when compared to the Council Bluffs, Iowa cathode -ray tube: one signal above the duration of changes in background light. oscilloscope base line, the second signal The biased diode (Fig. 9) with con- below. Thus, two phenomena can be denser C and resistor R develops a viewed and compared at the same time. voltage reference level equal to the peak Without clamping action on each of the of the video signal. Since the peak value two signals, they would merely vary is fixed, camera -signal components of about the oscilloscope base line (zero the video wave act in series with a fixed reference) and prevent an examination bias-forming part of the control -elec- formerly Wholesale Radio Laboratories RADIO -CRAFT for MAY, 1946 560 trode bias on the grid of the cathode-ray without change in reference level. tube. Background brightness of a tele- When the rectangular sync is re- 'c944te 2ulzeítel vised scene thus depends only on the leased, the clamping circuit immediately average value of the camera -signal com- becomes active. ponent. The blanking level remains fixed. Reversal of polarity of the sync wave RADIO & ELECTRONIC Supersync can also be held to a fixed applies a negative voltage to the cathode TESTING EQUIPMENT point of amplification by means of a of diode Dl and a positive voltage to the clamping circuit, thus establishing a plate of diode D2. The two diodes con- IMMEDIATE DELIVERY from STOCK GUARANTEED stable black-level independent of ampli- duct. The bridge is balanced, because of fier saturation. the symmetry of the circuit elements. The New Superior Therefore the Model CA -11 SYNCHRONIZED CLAMPING bias voltage appearing at the lower junction also appears at the Signal Tracer All of the clamping circuits previously upper junction. In this manner the input Net Price $18.75 described used a diode or triode to clamp signal is clamped to the reference volt- either amplitude FEATU RES: extreme-and allow the age E while the Signal wave bridge is active. * intensity readings are form to extend in only one di- When the next rectangular indicated directly on the rection from sync wave meter. the reference level. is applied, the bridge again becomes * Only ono connecting cable - A third and No tuning controls. distinct class of clamping non -conducting and the upper junction * Highly sensitive -uses an Improved vacuum tube is known as synchronized clamping. This voltmeter circuit. is free to follow the signal wave form, * Tube and resistor- capacity network are built Into circuit maintains the output potential the Detector Probe. and the entire process is repeated, ac- * Completely portable - weighs 5 lbs. Measures at a fixed level until an external syn- 5 x 6 x 7 inches. cording to the nature of the sync wave * Provision is made for insertion of chronizing wave is applied, when the applied to the circuit. phones. output The voltage is allowed to follow the Co- phased sync waves are coupled to New input signal. Then, at the conclusion of the bridge through SUPERIOR the blocking condensers. Model synchronizing wave the output volt- Each diode is shunted by its own re- age is returned immediately to the ref- PB -100 sistor -R1 and R2 -which charges the Volt -Ohm- erence level. This system is used in condensers so as to reduce the diode cur- most television circuits. rent flowing Milliammeter during conduction. Net Price Simplest type of synchronized clamp- During the clamping period, if a ing uses $28.41 a pair of diodes in a Wheat- charge develops on the condenser C is stone or it Ranges: balanced bridge circuit (Fig. removed through the diodes. If the DC Volta: 0 to 10). Other two arms of the bridge con- 5/25/50/250/500/2500 charge produces a positive potential at AC Volts: 0 to 1 /.5o/100/500 /1000. sist of equal resistances. Output 3leter Ran s: it to 10/50 /100 /500 /3000 sob the output, diode Dl provides a dis- DC Current: 0 to 10/250 mn. 0 to 2.5 Amp. The input signal to be clamped is Resistance: 0 to 1 0011/100.000 ohms. 0 -1 Mee. charge path. If the charge is of opposite Decibels: -10 to +15; 0 to +4:5; +30 to +55. applied to the upper junction between sign, diode D2 provides a discharge plate and cathode of adjacent diodes. path. Both of these paths are of low The When a reference bias is required, this impedance, necessary for a rapid dis- New "MONITOR" voltage E is applied to the diagonally charge of condenser C. Crystaliner opposite junction of the bridge. Another-form of synchronized clamp- SIGNAL ing utilizes two control triodes in a volt - GENERATOR age divider circuit (Fig. 11). Triodes Net Price 557.50 Vl and V2 act as variable resistors. 1 New Type Signal This arrangement maintains Generator designed for a con- the Serrlceme.n Interest- stant bias on tube V3 at all times ex- ed in money -making Ideas. Finter -Tip Control. Frequency instantly select- cept when a negative -going sync wave ed. No confused dial to read. No band switch I.F.. is applied to the clamping circuit. Broadcast. Shortwave and titra High Frequencies with or without 400 cycle note. Frequency accurate to .1 of SIGNAL ,005 When the sync wave is not applied, 1 %. Output approximately 10 volts. VOLTS C2 the input signal feeds directly to the INPUT grid of tube V3. Except for a small The New Model 802N fixed bias, the voltage at the grid of Combination tube V3 and the cathode -to -plate voltage across tube V2 are identical. Any posi- TUBE & SET tive increase in a signal voltage results TESTER in an increase in the bias of V1 -which Net Price $58.31 makes it a much higher resistance, and íMc brings the RANGES: voltage at the plate of V2 DC Voltmeter: 0/10/50/500/1000 at 1000 ohms per volt (and the grid of V3) Four Range AC Voltmeter: 0/10/50 /500 /THOU back to normal. DC Milliammeter 0 /1 /10 /1000 DC Ammeter 0 /10 In a similar manner, a decrease in the DB Meter: -8/15/15 to 29/29/ to 49/32 to 55 decibels Four Range Output Meter-same as AC Volts Fig. I I- Synchronized clamping, another form. grid voltage of V3 results in a decrease in the bias of V1, which decreases the R.C.P. Model 4.47 AC -DC Multitester $17.59 The synchronizing voltage (generally effective resistance of that tube and R.C.P. Model 448 Pocket Multitaster 24.01 a rectangular R.C.P. Model 461A Sensitive Multitexter 38.71 wave) is first applied to brings the voltage at the grid of V3 R.C.P. Model 488 Ultra-Sensitive Multitexter 70.07 a low-gain triode amplifier, and the out- R.C.P. Model 668 Electronic Voltmeter 73.01 back to normal. Action of VI and V2 R.C.P. Model 805 Tube & Set Tester 87.71 put of this tube is connected to one thus maintain the grid voltage of V3 at Supreme Model 546 Oscilloscope 82.50 junction of the balanced McMurdo Silver Model 900 "times" 59.85 bridge. A direct a constant value. SUPERIOR Model 1553 Volt Ohm Milliammeter 24.75 connection is also made between the sync When a negative rectangular sync SUPERIOR Model PB210 Multi Meter 35.75 wave and SUPERIOR Model 450 Tube Tester 39.50 the remaining junction point. wave is applied to the clamping circuit SUPERIOR Model 720 MultiRan,1eACAmmeter 49.50 In this way, the sync wave is applied (Fig. 11), tubes Vl and V2 are driven SUPERIOR Model 400 Electronic Multimeter 52.50' in opposite phase to opposite junctions beyond cut -off for the duration of the Send for our FREE New Post -War Catalog! of the bridge circuit. sync wave. When these tubes are not When a sync is applied to this circuit conducting, the grid of tube V3 is left (Fig. 10), the co- phased outputs from free to follow any changes in amplitude the triode prevent the two diodes from of the input signal. Condenser .Cl can- nW roftQNf/Naft conducting. A positive voltage is applied not discharge. Thus the grid voltage of ELECTRONIC & INSTRUMENT to the cathode of diode Dl; a negative V3 follows CO. the input signal voltage. Dept. voltage is applied to the plate of diode At the end of the sync wave, tubes V1 C, 6 MURRAY STREET D2. Thus the clamping circuit is in- and V2 are permitted to conduct, re- NEW YORK 7, N. Y., U. S. A. active, and the upper junction of the turning the voltage at the grid of V3 Phone: BArclay 7 -5556 bridge unaffected. Consequently, the in- to the reference level, and the clamping put signal appears across the output process is repeated. Cable Address: METRONICS RADIO -CRAFT For MAY 1946 561 EW RADIO PATENTS

By I. QUEEN

of these coils is further supported by the seal. VOLTAGE DOUBLER When a low voltage is applied to the bulb. the William W. Garstang, Indianapolis, Ind. filament becomes heated. At about 10 volts a glow Patent No. 2,392,472 discharge also takes place between the main lead and the bulb then brightly. The uses sets of contacts which ends, glows THIS vibrator two full current of the bulb is .15 amperes. enable it to double the voltage of the battery Fluorescent material may be coated on the which energizes it. inside of the bulb in order to obtain any desired lower Initially the armature rests on the three color including ultra -violet radiation. If a string contacts and when the battery is switched on bulbs are connected in series and one This of these current flows through the magnet winding. becomes defective by reason of failure to glow. sittracts the armature which therefore touches the other bulbs will continue to function. the upper contacts and interrupts the magnet winding. In this position the battery charges the condenser to its full voltage.

INDICATOR As the magnet is no longer energized the MOTION armature falls back upon the lower contacts Herbert Ziebolz, Chicago, III. again. This puts the condenser in series with Patent No. 2,383,758 the battery with the proper Polarity so that a total voltage of 2E exists across the output ter- MOTION or position is translated into electrical minals. An interrupted voltage of this peak value signals by means of an oscilloscope. The elec- exists as long as the vibration takes place. tron stream of the tube is deflected by both static and magnetic fields. Therefore the position of a magnet will affect the direction of the electron ENERGY REFLECTOR beam and the point at which it strikes the plate. Raymond J. McElhannon, Flushing, N. Y. If only part of the spot hits the plate, the meter Patent No. 2,391,914 will read lower than if the plate catches all the of micro- electrons. radar and similar applications Ll, together with its variable shunt, is FOR wave Coil waves, radio energy is emitted through used to counteract the effect of the magnet. area. This guides and caused to scan a given Curve A is the result when the shunt is approxi- usually requires a mechanical motion. This inven- mately 1/5 the resistance of the coil. Curve B means to tion, however, makes use of electronic is obtained when the two are equal. L2 is used direct radio waves. to position the spot initially so that it strikes the center of the plate. One application of this invention is the indication of the height of a liquid in a pipe by means of a floating magnet on the surface. These Aerovox Type PBS cardboard -case electrolytics squeeze into the tightest L9 876543ai places because they mount three ways - perfectly flat, on the side, or on end. L2

Aerovox Adjustimount feature facilitates the mounting of single or stacked units. Slotted metal mounting bracket instantly adjusted to any situation.

-111 11- 11110 ---- PBS electrolytics are available in wide range of voltages, capacitances, popular An elongated oscilloscope tube is used to pro- combinations. vide a sheet of electrons. This tube is much wider BRITISH HAMS ARE BACK than its height. Starting from the base end, the amateurs are now back on the tube contains a cathode or filament, two focus- British sing electrodes and a set of deflecting plates. An air, and licenses are being issued to Ask Our electron sheet is thus emitted by the filament and operators and stations. Some dissatis- Jobber is deflected between the two extreme positions faction is reported at the slowness with Ask for Aerovox Type PBS cardboard -case electro- noted by the dotted lines. replacement units. lytics as handy general -purpose The energy of a wave guide is directed which licenses are being processed. Ask for new postwar catalog. Or write us direct. output against the electron sheet and since the latter As in the United States, a great in- has the properties of a conductor, reflection takes crease in the number of "hams" is noted. place as shown, between the extreme positions A of Radio Society of and B. A more complicated set-up may be used Membership the if it is required that reflection of the energy Great Britain has jumped from 2,000 takes place in more than one plane. before the war to over 4,000, and it is expected that with radio-minded ex- PILOT LAMP Servicemen membership will reach Chalmers Morehead, E. Orange, N. J. 10,000 before the end of 1946. Patent No. 2,392,333 ELECTRONIC device combines the features of fluorescent RADIO EQUIPMENT SHOW !FOR RADIO- AND7 THIS and glow lamps in one bulb. It can be used Postwar radio parts and electronic either for decorative purposes or for pilot bulb INDUSTRIAL APPLICATIONS use. Its advantages are low power dissipation, equipment will be exhibited to the pub- cooler operation and long life. lic in a national radio show to be held AEROVOX CORP.,NEW BEDFORD,MASS.,U.S.A. The bulb is filled with an inert gas such as in the Stevens Hotel, Chicago, May 13th argon at low pressure. The leads are mounted 18, N.Y. Cable: 'ARLAB' 16th. is expected that many entire- Export:13 E.40th St, NewYork through a glass seal, and at their inner ends to It In Canada: AEROVOX CANADA LTD., Hamilton, Ont. are spot welded two filament coils. The ¡unction ly new items will appear.

562 RADIO -CRAFT for MAY, 1946 MODEL 2406 Volt OhmMilliammeter 28,000 OHMS PER VOLT D.C.

SPECIFICATIONS NEW "SQUARE LINE" metal case, attractive tan "hammered" baked -on enamel, brown trim. PLUG -IN RECTIFIER -replacement in case of overloading is as simple as changing radio tube. 1. READABILITY -the most readable of all Volt- Ohm -Milliameter scales NEW ENGINEERING NEW DESIGN NEW RANGES -5.6 inches long at top arc. 50 RANGES a REDDOT LIFETIME GUARANTEE Voltage: 5 D.C. 0- 10 -50- 250 -500 -1000 at 25000 ohms on 6" instrument protects against per volt. defects in workmanship and material. 5 A.C. 0 -10 -50- 250 -500 -1000 at 1000 ohms per volt. Current: 4 A.C. 0- .5- 1 -5 -10 amp. 6 D.C. 0 -50 microamperes - 0- 1 -10 -50 -250 milliamperes -0 -10 amperes. 4 Resistance 0- 4000 -40,000 ohms -4 -40 megohms. 6 Decibel -10 to +15, +29, +43, +49, +55 Output - Condenser in series with A.C. volt ranges. Model 2400 is similar but has D.C. volts ELECTRICAL INSTRUMENT CO. Ranges at 5000 ohms per volt. Write for complete description BLUFFTON OH IO. moving the power switch arm one posi- SUPERAMP WITH TUNER tion from the off position, power is ap- (Continued from page 539) plied only to the amplifier and tuner; by moving a position further, the arm applies power also to the phono motor. A Noticeable is the .0004 mf mica con- a.v.c. voltage to the first stage. The third section denser in series oscillator of the power switch applies with the coil radio volume control doubles as diode 6.3 volts to a pilot indicator. primary and ground, to assure more load. The a.f. signal from the triode uniform band spread. The i.f. signal plate of the 7C6 is coupled through a is amplified at 456 kc, through a 7A7, condenser and d.p.d.t. switch on back then detected by a double diode triode - of the tuner volume control, to the 7C7 OPPORTUNITY AD -LETS Advertisements In this srction cost :0 cents a word 7C6. One of the diodes is used to supply control grid. One half of the radio vol- for each insertion. Name, address and initials must be Included at the above rate. Cash should accom- ume control switch pany all classified advertisements unless placed by an accredited advertising agency. No advertisement is used to control a for less than ten words accepted. Ten percent dB- count six issues, twenty percent for twelve Issues pilot light used to Objectionable or misleading advertisements not ac- denote whether the cepted. Advertisements for June. 1946. Issue must reach us not later than April 23. 1948. tuner is in or out Radio -Craft 25 W. Bway New York 7. N. Y. of the a.f. circuit. Incorporated is a MAGAZINES (BACK DATED) -FOREIGN, DOMESTIC, arts. Books, booklets, subscriptions, pin -ups, etc. Cata- well filtered full - log 100 (refunded). Cicerone's. 863 First Ave.. New wave power sup- York 17, N. Y. ply, good for 300 AMATEUR RADIO LICENSES. COMPL171'E CODE and theory preparation for passing amateur radio ex- volts at 150 milli- aminations. Home study and resident courses. American Radio Institute. 101 West 63rd Street. New York City. amperes -the actu- Seo our ad on pago 588. al high voltage cur- CORRESPONDENCE COURSES AND SELF- INSTRUC- non books slightly used. Sold. Rented. Exchanged. All rent drain being subjects. Satisfaction guaranteed. Cash paid for used courses. Complete information and 92-page Illustrated bar- about 115 ma. gain catalog Froc. Write -NELSON COMPANY. Dent. A complex power 2 -39. Chicago 4. switch is used in SURPLUS RADIO AND ELECTRONIC PARTS AND equipment. New and used. Write for free list. High - order to control bridge, 312 Canal St., New York City 13. the phono motor, YOUR NEW FREE CATALOG IS BEADYI RADIONIC'S Catalog lists hard -to -get radio parts and books. All avail- mounted on top of able for immediato shipment. Send today lo: ltndionic Equipment Co.. Dept. 1,15. 170 Nassau St.. New York 7, the cabinet. By N. Y. . QSL'S, SWI: S NEW DESIGNS. FIRST CLASS PRINT- Inc. Free samples. Richard Fran,en. W3DEE, Maple Shade. New Jersey. The under -chassis wir- RADIO TUBES. PARTS WHOLESALE. BULLETIN 3c. ing is somewhat com- Penshaw Radio Co.. 3313 Delaran. Kansas City. Kansas. plicated due fhe to PLANS 1 -TUBE DC RECEIVER (BW RECORD 7000 including Radlobuilder" large number of parts. miles). . -25c laboratories. Box

RADIO -CRAFT for MAY, 1946 563 MULTIPURPOSE TESTER (Continued from page 534) i i a receiver or amplifier. For tracing Sw3. Revolve the top calibrated dial audio -frequency signals, connect a (R16) to 0 degrees, and with R15, the shielded test prod and lead to jack J7. uncalibrated control, adjust one section The signal may then be traced from the of the twin indicator tube until the "eye" sound source to the output by touching just barely closes. Plug in the test leads stage circuits. to the red jack J1 and the black jack J2. the prod to successive the probe is used for following For measuring d.c. voltages connect The r.f. test side of the the signal from the aerial to the detec- lead from J1 to the positive be measured and the lead of a receiver. To operate, turn on potential to tor side. Turn the switch Sw2, and connect a jumper wire from J2 to the negative 2. the J6. The signal can then selector switch Sw4 to position If from jack J7 to to cause the observed or heard by touching the voltage is not great enough be switch to po- probe of the tube to the r.f. and i.f. green image to overlap, Always connect a lead from J8 sition 3, 4, or 5. After the proper range stages. cali- of the receiver whenever has been selected, rotate the top TIP to the chassis opens the signal tracer is used. brated dial (R16) until the "eye" for You! The volume control, R3, should be to the "just barely closed" position. halfway for the aver- Read the number of degrees indicated turned up about voltage chart. In fact there are age signal. The electron -ray indicator and refer to the proper four interchange- tube can be used to observe the inten- Two of these voltage charts should able tips adapted sity of the signal. The tube is turned on be made for each of the four ranges. One to the Ungar Sol- by switch Sw3, and connected to the set is for a.c. and the other for d.c. dering pencil... amplifier by turning selector switch voltages. These charts can easily be each designed Sw4 to position 1. Turn up the inten- prepared by applying known voltages to do speedy sity control R18 until the indicator tube and recording the number of degrees precision work responds to a signal impressed on the deviation from zero required for each on hard -to- amplifier. Set the uncalibrated bias con- voltage. An accurate voltmeter used in reach jobs! trol R15 so that all of the resistance is conjunction with a variable a.c. and a cut out. This causes the "eye" to open. variable d.c. source can satisfactorily be No. 537 Pencil The intensity of two or more signals used to calibrate the tester. Tip, mode from may be accurately compared or matched If it is not known whether the voltage Elkaloy A, Tip with the indicator tube. With no signal is a.c. or d.c., it can be determined by Vs" dio. present, turn the calibrated dial which reversing the leads. If the voltage is d.c., operates R16 to 0 degrees (all resist- the 6AF6 -G tube will indicate the ance effective), and adjust the uncali- voltage only with the positive side con- Ruggedly built, the brated potentiometer R15 until the nected to J1. If the voltage is a.c., the Ungar Soldering tool shadow angle is 0 degrees or the "eye" tube will indicate the potential during weighs only 3.6 ots., just barely closed. Turn the intensity both trials. is perfectly balanced control R18 to its maximum setting and Position 5 will measure 1 to 32 volts and handles like a do not change the setting during tests. a.c. or .5 to 41 volts d.c.; position 4, 20 fountain pen. Heats Apply the signal to the unit and note to 400 volts a.c. or 5 to 200 volts d.c.; 3, 100 to 1100 volts a.c. or 50 in 90 seconds. Draws that the green image will overlap. Turn position dial R16 until the to SOO volts d.c., and position 2, 400 to only 17 watts. Unit the top calibrated just as it did with 2500 volts a.c. or 200 to 1500 volts d.c. complete with any indicator tube appears no signal present. one tip sells at less Read the number than $2. Please order IN4 of degrees indi- from your Electronics cated by the dial distributor. and then repeat the /No. 538 Chisel process for other Tip, made from signals. If the Elkaloy A, Tip reading is less for X dia. another signal, the strength is less; if the reading is greater, the signal strength is greater. To connect the No. 539 test unit as a volt- No. 536 Extra Hot, meter, turn on the Standard made from power supply and Tip, made from Tellurium Hard Drown indicator circuit Copper with the switch mounted on R3, Ungar and toggle switch Components in the in- flectricTools, /.u. strument are neatly Formerly Narrt' A. Un1r, Inc. and well laid out, as LOS ANGELES 54, CALIF. may readily be seen in the photograph, right. 564 RADIO -CRAFT for MAY, 1946 Position 2 has a much higher theoreti- indicator circuit, revolve the top cali- 9 and 10. The charts can be prepared cal range, but due to arcing or break - brated dial to 0 degrees, and with the very easily with the aid of variable a.c. iItg down of the insulation in the selector uncalibrated knob set the indicator tube and d.c. sources and accurate alternat- switch or at the jacks, it is not advis- so that the green area of one section ing and direct current meters. Position able to apply higher voltages. just barely touches. Turn selector switch 8 has an a.c. range of 1 to .15 ampere One of the leads is connected directly Sw4 to position 7, and plug in the test or a d.c. range of 1 to .05 ampere. The leads to the chassis; so, take care that the to J1 and J3. Connect the prods current is limited to a maximum of 1 metal cabinet is on an insulated surface in series with the circuit to be analyzed. ampere because of the power rating of well away from the receiver or voltage For d.c. measurements make sure to the resistor and the large voltage drop. connect source and that the operator does not the black lead from J2 so that Position 9 has a range of 20 to .5 mil- touch the cabinet. It might be worth- as the electrons flow from negative to liamperes d.c. only; and position 10 has while to insulate the cabinet from the positive, they will enter that lead. Turn a range of 1200 to 50 microamperes d.c. negative side of the "B" supply and to the selector switch to position 8 for only. connect a small condenser from the neg- large alternating or direct currents, or The current meter may be found use- ative side to the chassis. to position 9 or 10 for smaller direct ful for approximate measurements if no currents. With current flowing through standard meter is on hand. CURRENT MEASUREMENTS one of the shunt resistors, the image of The test unit can be used for approxi- the indicator tube should overlap. Ad- RESISTANCE MEASUREMENTS mate current measurements in cases just the top calibrated dial so that the The methods of connecting the low where the relatively high voltage drop image appears as it did with no current range ohmmeter circuit of the test unit will not upset the operation of the cir- flow. Read the setting and refer to the is as follows: Turn on the power sup- cuits. To set the tester for this func- proper current chart. ply and indicator circuit, revolve the tion, the following steps should be Two current charts are required for top calibrated dial to 0 degrees, and taken. Turn on the power supply and position 8 and one each for positions (Continued on following page)

- most < 1ja

4 OUT OF 5 DIAGRAMS POPULAR, LONIoPRICED DIAGRAM MANUALS 1942 YOU WILL EVER NEED These cssy -to- apply, inexpensive manuals will help you Find radio faults quickly. Make the needed repairs in repair radios faster. This volume covers 1941 models, any radio in minutes instead of hours. Save time on 1941 with alignment data, I.F. peaks, and replacement parts every job. These large, inexpensive diagram manuals lists. Compiled by M. N. Beitman, hide' the circuit for every popular radio receiver. ar. w,.xa. radio serviceman for many years, Most Popular 4 'of 5 out diagrams you will ever need are included. .1931 author and teacher. Be ex- Models Made by: WITH ALIGNMENT DATA, PARTS RADIO pert in radio servicing; LISTS DIAGRAMS. simplify your work. 192 00 Philco, RCA, Clearly printed circuits, alignment data, parts lists, service Ji u K -- Zenith, Sears, hinté are the facts you need' to speed up servicing. Repair pages, 816x11 inches. Only GE, Emerson, radios: quickly and properly- follow the factory a. Let this important man- Belmont Radio instructions given in these manuals. The 1942 ual give you over 80% of Detrola, Fada, manual lists 351 models of 40 manufacturers. 192 all 1940 circuits you will United Motors, fact. packed pages. -Large size, 81/2 1940 x 11 in ever need, acquaint you Westinghouse 200 with new developments, train you to service Arvin, Majestic, The most popular volume of the quickly and efficiently millions of Stewart-Warner, series. Will pay for itself with the seta. Data on F.M.. portables, re- $900 Admiral, Delco, 1926-1938 time saved during the first day of cording. etc. 417 models of 43 man- Stromberg- Carlson, use. Includes all the popular old ufacturers. 208 pages. Net price Western -Auto, timers. Save hours on every job. 427 his grams the Another handy manual of Sparton, Wards, of radios of this most-popular Motorola, Gamble, period, with parts lists and alignment in- diagrams you and many others. formation. 240 pages, 8% x 11 inches. need. Circuit data, hints, :I.f 1939 and information are time- savers and money -makers for you. Let these diagram manuals SAVE HOURS ON EVERY JOB guide you to easier service work. Why try to get along without SUO Be ready to make helpful diagrams? Use this volume with repairs in minutes instead of diagrams 192 pages of popular hours. You will be called upon to fix hundreds of 39 manufacturers. Order today. Price only of models listed in Compiled by these easy -to -use manuals. M. N. Reitman, Tackle each job with the needed help found in NO RISK TRIAL ORDER COUPON radio engineer, these service manuals. Greatest bargain in SUPREME PUBLICATIONS, teacher, author diagram books. Send coupon today. Plan to use 9 S. Kedsle Ave., Chicago 12, ILL. & serviceman. these manuals this week. Ship the following diagram manuals: (Money back guaranteed) 1942 0 1941 ci 1940 1939 1926-1938 Q I am enclosing 5 send postpaid. Supreme Publications Q Send C.O.D. I am enclosing 5 deposit. Name: PUBLISHERS OF RADIO BOOKS, MANUALS, AND DIAGRAMS Address : (Use Coupon or Write Order in a Letter) RADIO -CRAFT for MAY, I 9 4 6 56 MULTIPURPOSE TESTER Slalkag' (Continued from. previous page)

switch Sw4 to position 6. the shadow angle returns to normal, the TESTING INSTRUMENTS turn selector Run a jumper wire from Jl to J4, and condenser is good; but if it does not re- connect the test prods to J8 and .15. turn to normal, the condenser is shorted Short the test prods together and ad- or leaky. If the indicator tube fails to A GREAT AFTER just the shadow angle to 0 degrees. Now "blink," either the condenser is open - WAR RECORD connect a resistor to the test prods and circuited or the capacity is less than adjust the top calibrated dial R16 until about .001 p,f. Note that the shadow will the green pattern appears as it did with not be deflected again until the con- the prods shorted together. Read the denser is discharged or the leads re- K / versed. number of degrees indicated and refer A f N to the low range resistance chart. Electrolytic condensers are tested in A The high range of the ohmmeter cir- a similar manner with a few exceptions. cuit of the tester is operated as fol- It is necessary to connect the positive lows. Rotate the top calibrated dial to terminal of the condenser to J2 and 0 degrees and turn selector switch Sw4 the negative terminal to J5. When the to position 5. Run a jumper wire from prods are connected to the condenser, J1 to J4, and connect the test prods to the shadow angle of the indicator tube J2 and J5. Adjust the uncalibrated dial should be decreased for several min- so that the indicating shadow is 0 de- utes. Ir the condenser is good, the grees with the test prods NOT shorted shadow angle will slowly increase un- together. Connect a resistor to the test til it reaches a constant value. After prods, and adjust the top calibrated dial testing any type of condenser, it should so that the shadow angle returns to 0 be discharged by short- circuiting the degrees. Read the dial setting and re- condenser leads. A spark can be noticed fer to the high range resistance chart. with any condenser with a capacity of The low range of the ohmmeter cir- .01 µf or more. cuit is 400 to 500,000 ohms; the high range is 15,000 ohms to 30 megohms. The CAPACITY METER two resistance charts can be prepared To measure the capacity of con- with the aid of a variable resistance and densers, revolve the top calibrated knob an accurate ohmmeter. to 0 degrees; turn switch Sw4 to posi- SUPREME tion 6, and connect the test leads to Jl MODEL 504 -A CONDENSER TESTS and J9. Adjust the uncalibrated knob TUBE AND SET TESTER To test paper, mica, or variable con- so that the shadow angle of the indi- densers connect the jumper wire from cator tube is 0 degrees with the prods SUPREME regrets that war J1 to J4; turn the selector switch to NOT short-circuited together. Connect necessitated an interruption position 5; plug in the test leads to J2 (R16) to 0 degrees, and with R15, the of service to its customers and J5, and turn the uncalibrated knob the condenser to the prods and adjust and friends. We are genu- so the shadow angle is maximum (about the top knob in order to deflect the inely glad to get back into 100 °). Contact the prods to the leads shadow angle back to 0 degrees. Read peacetime production -proof the condenser. The shadow angle of the number of degrees indicated by the to the capacity meter duction for YOU. the indicator tube should momentarily knob and refer be reduced as the condenser charges. If chart. MANY SUPREME INSTRUMENTS NOW AVAILABLE -But not enough to take care of all orders at one time. Demand for accurate, dependable SUPREME equipment is such that we suggest you make arrangements for your needed new SUPREME models without delay.

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SUPREME INSTRUMENTS CORP. PILOT LIGHT GREENWOOD, MISS. U. S. A. Export Department: Hw ry THE AMERICAN STEEL EXPORT CO., Inç, 374 Madison Ave., New York 17, N. Y1 to the schematic. Front view of the instrument, showing controls. Designations refer Nor -CRAFT for MAY, 1946 566 RADIO If a stock of condensers of known capacity is available, the capacity meter chart can be prepared by recording the HARRISON HAS IT! number of degrees rotation required for ARRISON HAS IT! each capacity. The meter has a range of V .0004 to .25 microfarads. LINES V The resourceful experimenter will be ALL STANDARD able to think of many additional uses V HSS -HARRISON SELECT SURPLUS for this multipurpose tester and signal V tracer. The circuit does not employ any expensive precision parts, and makes a HALLICRAFTERS TRANSMITTERS! very interesting and useful project. SIGNAL CORPS Used In the SCR -299 450 WATT CW mobile station (the fa- 325 WATT PHONE List of Parts mous "Voice of Vic- CONDENSERS tory") these transmit- CONTINUOUS ters are outstanding for DUTY OUTPUT Cl, C2 -16 mfd. 460 V. electrolytic. their dependable, effi- We are having the Hal - cient service. This war - licrafters factory remote C8 -.005 mfd. 600 V. tubular. improved version of the these transmitters from C4, C17 -.06 mfd. 600 V. tubular. IIT -4, ruggedly con- the SCR -299 trucks, and C5-.02 mfd. 600 V. structed for continuous' carefully retest and crate tubular. duty, In modern black them for shipment. A C6-25 mfd. 26 V. electrolytic. console cabinet is suit- few may have been C7, C8, C9, C10, C13, C14, C16, C18 -.05 mfd. 600 able for the finest com- slightly used for dem- V. mercial or amateur sta- onstration but all are tubular. tions. fully guaranteed to be C11, C19, C20-10 mfd. 25 V. electrolytic. Among the in perfect condition. C12, C15 -.0001 mfd. outstanding I eatures We make them available mica. for only a fraction of Band switching of oscil- the original cost! RESISTORS lator and buffer stages Complete BC -610 trans- -- crystal or VFO (Var- mitter, with BC -614 Rl, R5, R7, R14- 500,000 ohm carbon. iable Frequency Oscil- speech amplifier and lator) operation - all connecting c a b l e, all R2-500 ohm 1 W. carbon. stage. metered -remote tubes. operating manual, R3-500,000 ohm volume control with switch. Speech Amplifier for and coil sets for 20, 40. R4, R13, R22- 100,000 ohm control desk - control, and 80 meter bands (or carbon. and protective relays one set of coils for any R6, R24 -2,000 ohm carbon. and Interlock switches other frequency between 118, 1121 -1 meg. carbon. -modulation limiter - and IS Tfe.), for R9- 10,000 ohm carbon. all steel cabinet 33^ x 115 Volt, 50/60 2t.^ a 40^ high - link cycle SJ11B RIO, R12- 50,000 ohm carbon. output to transmission 1111 -250 ohm carbon. cable. 10 -METER 1116, R18 ACCESSORIES OPERATION -1 meg. potentiometers. Crystals: Amateur34.80. R16- 750,000 ohm volume commercial Hailiereften is furnish- control. ... 819.50 ing us conversion kits 1117- 260,000 ohm carbon. Microphone: with desk containing coils, parts 1119 -10 meg. carbon. stand, cable, and plug and complete instruc- R20-5 628.50 tions for simple changes meg. carbon. Additional sots of coils to permit efficient oper- R23 for commercial fre- -10 ohm 10 W. power. quencies ation on 28 -30 Tin 1125 -50.000 ohm carbon. 640.00 525.00 RECEIVERS TUBES LOCAL HAMS I - - Come In and get And here are the SCR -299 receivers at a sensational price! LIMITED 1 -5Z4. the 11C11-299 One of the finest. most modem communications receivers ating Oper- -sturdy, dependable. compact -- excellent for all services. QUANTITY! 1 Two with -6F6. RF stages -high sensitivity exceptionally low Wire Special De- top, with la eps, noise level- crystal niter-two IF Mages--precision dial - or 1-6J7. cable channel. etc. 4500 division vernier bandspread -ten tubes-Pt/2"x Is^ livery your order. 1-6B8 or 6B8 -G. FB alué! panel with 8^ deep metal cabinet -beam t utput- Don't wait or they Also to 18 with 2. 5. & 30 select all mh teracoconverter top On all may bo all sold. Im- I- 6AF6 -G. your for mediate om large Complete receiver with tubes. speaker In metal cabinet. shipment 1 -6K7. stock of all stand-d and to Model BC -342, from N e w T o r k. 1-6H6. ard 115 In It 50ion anual -ready 59% with order. amore ré PISS baargains. F-3o tttoobpil ao etvco- or eS9cy ice -Model balance C.O.D. BC 2, tem 2 t batmneg .0Ór MISCELLANEOUS PARTS A POST CARD wil put your name on our IF YOU WANT to be among the very first to has I -Power transformer; primary 120 V. A.C.; mailing list to receive new catalogs. bul- V any nut or not immediately available equipment get on our "Preferred List." secondary 6.3 V. q. 3 A., 5.0 V. ! 2 A.. and letins, additional HSS bargains, and details V 350 -0-350 V. of how you may obtain, without cost, a The factories owe us plenty -and as it come. in we rush it right out! 1 -5 inch dynamic speaker with 450 ohm field copy of V winding. "Electronic Parts and Equipment." can make sure of getting yours quicker by our new 800 -page Buyers' Guide. VYoutelling us now what you want. (Naturally. orders 1- Output transformer with 7000 ohm primary deposit mole first.) If you change your mind winding. PLEASE SEND IT TODAY! Vwithyou ran r.nwel ',ilium( obligation. 6 -"MIP" octal sockets. 2- Tuning indicator octal sockets for 6B8-G and 6AF6 -G tubes. 1 -Metal tube shield for 6B8-G tube. 6 -Grid caps. ARRISON RADIO CORPORATION 2- S.P.S.T. Bat -Handle toggle switches. 1- S.P.D.T. Bat -Handle toggle switch. '-i' -) 12 WEST BROADWAY NEW YORK CITY 7 1 -11 position selector switch. 5. 1 -Black 114" streamlined bar knobs. BARCLAY 7 -9854 6 -Dial plates. 1 -ICA Precision Vernier Dial (4" diameter, JAMAICA BRANCH - 172 -31 Hillside Are. - REPUBLIC 9 -4102 325') for 1115. 7 -Red insulated tip jacks. 4 -Black insulated tip jacks. 1 -T-2 Tiny Neon Lamp (General Electric). 1 -Pilot light assembly with 6.3 V. lamp. 1 -Fuse and fuse mount. dora Eeeetwc 71 'e 1 -12" x 7" x adiet 71" metal cabinet. #aadivattets For nomerpw control appliceriuns such al burg. 1- Chassis. tar alarms, industrial solely cannel., automatic o n,r and in 1 -3 ft. 6 Wire shielded cable for R.F. tube probe. Folder R -5 illustrates canianctior, with a chime or bell Hook -up wire, a of steeple in spaghetti, rubber grommets, and complete line of Guar- es andd ces. n Fo, AC. other hardware. anteed Campi.,. with oll tubes and SPOT 45 control relay. No CANNON -BALL ADSON RADIO CO. WAR AID TO TELEVISION 221 FULTON ST, NEW HEADSETS YOan 7 N Y. Home television will benefit from the Beautifully designed, wartime development of the television - ANOTHER Light in weight. Effi- NEWARK STORE! guided -bomb. ScientinHily AT 212 Spilt cient. Reproduce with FULTON ST., NEW YORK 7, N.Y. Visual pickups of news events Heavy bar mag- -pa- nets greatly In clarity and good volume. t sl_eeeo rades, sports, fires and other their em occur- alares.. . Write rences -are made possible by a portable C. F. CA NNON COMPANY Newer camera -transmitter unit built originally SPRIN GWATER, N. Y. /,LELTR/!'C ompanj 115-I17 W. 45th St, to help bombardiers steer their missiles. PO 323 W. Mldlsoe St. NEW YORK IA RADIO CHICAGO 6 -CRAFT for MAY, I 9 4 6 567 DEMONSTRATION DEVICES Radio (Continued from page 533) a.c. afee. When it is adjusted so it will just a strobotron fired from a slip ring's the arrow on the rotating output. A burnt -out power transformer, fire on peaks, with Headquarters wheel becomes visible when vertical about 150 -watt size, was rewound up. Since the arrow is two identical windings corresponding to with its point except rotating clockwise 360 degrees every cy- approximately a 220 -volt primary winding was center for 25 cle the alternating voltage across a coil that the secondary reaches maximum 90 degrees or one tapped. On the 120 volts at 60 cycles before it reaches maximum they each drew about one quarter amp. years quarter cycle over one across a resistor in series with that corresponding to something henry inductance. Two 5.25 -µf (15- coil. in Lastly turn on and adjust the strobo- watt fluorescent lamp) condensers is controlled by the con- parallel across the primary and second- tron whose grid cycles denser voltage. It illuminates the rotat- ary coils, tune them to about 40 with tip down- per second. The "radio frequency choke" ing arrow when vertical trans- wards, proving the alternating voltage is the primary of a small power a condenser reaches maximum. 90 former and its coupling -from center across of primary degrees or one quarter cycle after it tap of secondary to high end across a resistor in -is made through a 2 microfarad con- reaches maximum two diodes series with that condenser. denser: A 25Z5 supplies the (reverse line plug or use a transformer Notice that with sine wave variation, results lui hence its if high side of a.c. line affects current through a coil and heater circuit). The 50,000 - is fastest at the through the magnetic field, rising ohm load resistors have 2 -watt neon start of a cycle. Thus the induced volt- indicators. of change lamps in series with them for age which depends on the rate At radio frequencies the bottom end of of field, must be maximum one quarter We ship at once parts, the primary of the discriminator trans- - of a cycle before the greatest current connected to voltage drop across, former is effectively equipment, whatever you need! through, and hence ground through the bypass condenser a resistor. In the case of the condenser is less than an ohm at the it will be greatest (.1 µf This house began its career almost as the voltage across ; end of the charge. frequencies used) and the early as Broadcasting itself! Today, 25 when it contains the greatest radio frequency choke going to the cen- years later, we're the world's largest radio This will be when the total current is con- condenser ter tap of the load resistors also supply house! Standard Lines: National, which has flowed into the nected for practical purposes to ground Hammarlund, R.C.A., Hallicrafters, Bud, reaches maximum, which is just before by con- flow by the bottom resistor's -pass Cardwell, Bliley, and all the others! the current reverses and starts to at 4 current re- denser because a .001 µf condenser out. This point where the megacycles offers about 18 ohms react- SUPERSPEED SERVICE Orders verses is one quarter cycle after the important ob- and hence ance. This leads to the shipped out same day received, maximum current through, servation that THE R.F. CHOKE IS on most goods. voltage drop across, a resistor. EFFECTIVELY CONNECTED ENGINEERING SERVICE If your The entire circuit diagram of the ACROSS THE PRIMARY IN SERIES - problem requires stroboscope apparatus is shown in Fig. WITH ITS COUPLING CONDENSER. special equipment, we'll make it 1. The 3.5 microfarad condensers came Because obtaining less than 1 ohm at 40 from double 40 -watt fluorescent lamp cycles requires thousands of micro - ballasts discarded because of noise or farads, one slip ring was connected FREE! burnt-out coils. The resistor and choke directly to the -bottom end of the pri- were chosen to give somewhere near the mary as well as to the junction of the Latest bargain flyer is across the condenser, test instru- same voltage as two resistors and r.f. choke. These are includes about 800 ohms and 2 henrys. taps ments, record chang- or mounted behind the board and to points on ers, communication CONSTRUCTION brought through equivalent DEMONSTRATOR the hookup painted on the front. This receivers, ham trans- at last to the discriminator tubes and a Turning does not change operation of the circuit mitting C and Fig. 2, the vari- electronic shown in Photo but saves large condensers. host of able frequency alternating current is itemsyou need today. a pair of slip rings con- supplied from USING THE DEMONSTRATOR nected to diammetrically opposite com- Originators and `T mutator segments on the armature of a One strobotron's grid and cathode is Marketers of voile Aa Q motor. connected across the r.f. choke (heavy the Famous two pole, series, direct current from three heavy- black in the diagram). A second strobo- Power is supplied upper half duty 45 -volt B batteries in series with a tron is connected across the rheostat to control the speed of the center tapped discriminator sec- carbon pile strobotron is net o Wire and thereby the frequency. The end of ondary. The remaining shaft carries a fly -wheel with connected across the lower half bf the the motor motor is Telettision inc. an arrow or vector on it which appears secondary. When the started, light of the slip rings supply a frequency equal NEW YORK 13 BOSTON 10 NEWARK 2 stationary when viewed by the

out couoee, Doste on penny post cord, malt today Above Resonance, Xi Cut Below Resonance, Xs. Frequency Resonant. Xr, is more than Xe is less than Xe Balances Xe R. W. T. Dept. t1EI 100 AVENUE OF THE AMERICAS, NEW YORK 13

Gentlemen: Send me FREE copy of your Latest Bargain Flyer C.76, packed with recent electronicequipment and components

!YAW L...- is 0 Current lags,la s, outoutput ut is -- is Current in- Pphase, outputout ut ADDRESS leads, output - leading and lagging currents. Diagram from bottom of board, showing in- phase, CITY 2ONr STATEEI Fig. 3- RADIO -CRAFT for MAY, 1946 568 to its revolutions per second. When this frequency is about 40 cycles the 90- degree leading counter-voltage from the secondary coil just balances the 90 -degree lagging counter-voltage from the condenser across the secondary. Re- member how the condenser and coil voltages were exactly opposite on the vectorscope? Since there is nothing but the resistance of the circuit offering opposition ,at this resonant frequency, a considerable circulating or oscillating current is set up, which creates a high counter -voltage across the inductance and an equally high but opposite voltage across the condenser. If the secondary's inductive reactance Xo is Q times its resistance R, this counter -voltage, which equals IXr. created by the oscillating current through the coil, is Q times the actual voltage induced in the secondary which equals IR. This Q or multiplying val I ñnäeÌrai

ttó M1LLIAMETltann be from two to thousands in a radio, so ER I; m.Y nnt.s33eo the voltage induced in - the secondary can Combination VOngVOLI for oll tests. n:roohiw%vóts.mlcrN be ignored compared RCP switchtch p/ n tnwers to the back voltage TESTER OB.O/ tom0lem &/ SET 5.00a anm created by the oscillating current in the TUBE /a0 "` O 130 ,° AMPLIFIER secondary at resonance. rnnum°saooo1T,ee.; ao 25 viol p.A. !C-.;R DGt000 Ó $¿ç a20.,U/T00 I ct 1 / Oh200.000: 7l AGr000.mmeeÓ05000DCÓÓOr éRÓ?0.rK/S1 " RESONANT FREQUENCY AG vo1P_.,eminru6 .nlubet. The induced voltage from the circu- 9 lating current at resonance across both p { D t ivu eter-wme halves of the secondary fires the strobo- 69S2 A ún2N S trons connected to it, producing a eso two es- Net r images of the arrow 180 degrees apart, ¡, COMPANY and the position of the cardboard car- 1, N Y. rying the arrow on the flywheel ELECTRONICSNEW YORK is ad- ST., lar .nvm;,, mrcña äi:: CORTLANOZ 3-2696 justed until these arrows appear Wrue to us Psntm 82 Whitehall No 105 straight up and down and the image rins,,,,e. Ìtt ep OgPt- of the arrow, made visible by the strobotron connected scion the r.f. choke, is horizontally to the right, half way or half of the coil equals the sum of the this resonant condition, the actual volt- 90 degrees between the other two. To voltages across the choke and the bot- age curves and secure this last condition their vector representa- the capacity tom half of the coil. So when these two tion together with their rectified sum of the 21.1f coupling condenser may have sum voltages are rectified as shown by are shown in the center diagram on the to be changed. When the voltage across the shaded areas, they create equal cur- discriminator the r.f. demonstrator board. See choke is half way between the rents through the top and bottom load Fig. 3, a two secondary reproduction of these curves. voltages, the sum of the resistors as is evidenced by the fact Remembering that electron voltages across the choke and the flow is from top that both neon lamps glow equally. For cathode to plate in a tube, it is easy to RADIO TERM ILLUSTRATED see that the equal voltage drops across the two resistors oppose, and hence the Suggested by Robert Hopkins, total voltage is zero. Nelson, B. C., Canada BELOW RESONANT FREQUENCY Next slow down the motor by means of the rheostat to produce a lower frequency. Since the condenser still charges to the same extent but fewer times per second, the current in and out of the condenser is less, so the capacitative reactance Xo must be greater. Since the magnetic field now interlinks the secondary coil fewer times per second there is less induced voltage so the inductive reactance XL must be less. When capacitative reactance Xo predominates over the inductive reactance XL in a circuit, the maximum voltage opposition occurs late in the cycle and so maximum current flows earlier in the cycle and the current is'said to lead. Because the circulating current in the secondary now leads, the Q -fold counter -voltage it produces across the secondary coil now also leads. The position of the vectors and the sine curves they represent for this condition are shown in the left di- Regeneratior. (Continued on following page) RADIO -CRAFT for MAY, 1946 569 so there is more current into it and its 'éiilíi;l,ihl',iglt;.i.r must be less. The sec- er 'i4 l!Á!:'l:!íilillles'siil'e""` reactance X. >i'iiltt,.r,ia. ondary's field, reversing oftener per second, induces more voltage, so its reactance XT, increases. When inductive reactance XL exceeds capacitative reactance Xc the greatest reactionary voltage occurs early in the cycle (remember how the back voltage across the coil was ahead of that across a resistor or condenser ?) and the maximum current does not flow until later, or in other words the current lags. As the whir of the motor gradually increases in pitch the two vertical secondary vectors slowly turn clockwise from their 90- degree position relative to the black primary vector which remains unchanged and the upper load resistor lamp glows brighter while the bottom aqe" load resistor lamp dims, indicating that RADIO DIAL BELTS the sum of the choke and top coil now ITS ROUGHNESS ASSURES SMOOTH PERFORMANCE exceeds the sum of the choke and bottom one. This makes the top end of the Made of buna S rubber (1t3 thin single) with smooth rubber cover on outside and rough finish on inside. two resistors positive to ground since Standard equipment with set manufacturers - resistant the electrons accumulate at the lower to atmospheric changes - more pliable and rougher - entrance to the top resistor making that insuring positive grip on shafts and pulleys. Its popularity has made it the largest selling Radio Dial Belt in the U.S.A. end negative while their scarcity at the of resistor makes it positive. pay for the belts and top this FREEJustget this metal container Ask your jobber for handy, durable MECHANICAL ANALOGY This B2SA Servicemans Assrt. 2S Belts this Metal BSOA ALL METAL service. The conditions just observed, namely: 100 " man's sliding drawer C ontoi n er BIOOA " at low frequency the condenser offer- FREE Use the Belts the Manufacturers cabinet. the end of the use in their original equipment. ing the chief opposition at cycle (so the current led) and at high frequency the inductance offering the D CO. chief opposition at the beginning of the J F MANUFACTURING lagged) have a 19, N. Y. cycle (so the current 4111 FT. HAMILTON PARKWAY BROOKLYN mechanical counterpart, lucidly described by Drysdale, "If a steel bar with DEMONSTRATION DEVICES a weight on the end of it is clamped in Unusual Buy a vise, and is pulled to one side and let Ray Tubes (Continued from previous page) go, it will vibrate to and fro with a Cathode definite frequency. If we take hold of backwards and of the discrim- the end of it and move it agram at the bottom very we shall feel board and its re- forwards slowly, that inator demonstrator elastic force of the spring, which is production in Fig. 3. end of stroke, prac- slows and the fre- greatest at the the As the motor speed if were no weight. But can watch the two sec- tically as there quency falls one now start to move it more rapidly, and ondary vectors shifting counterclock- swings much because the clock- it will be found that it Television Parts wise, indicating a lead more easily; or if the same force is ex- wise rotating arrow is illuminated be- New Factory Sealed Tubes for visible posi- ercised the swing will be much greater, fore it reaches its former move with the same Television and Oscilloscopes imagines vectors to until when we it tion, (Convention frequency as that with which it vibrat- DUMONT 7EP4, price $29.90 rotate counterclockwise so a counter- move almost without 18.00 ad- ed itself, it will RCA 6BP4, price clockwise shift means they have thé hand at all, and if DUMONT 6ßP1, price 15.00 rel- any force from vanced from their former position continue to the same G.E. Focusing Coil for Electromag- voltage across the we were to exert netic Tubes, price 8 50 ative to the primary force as at first, the swing would be- with 6 An- At same time it is RCA Television switch black ri. choke.) the come so great as perhaps to break the tennae RF transformers, price 5.60 obvious the sum of the "black" and top C.E. CR Power transformer 1700 V , spring (just as a condenser). s 90 voltages is now less than the black and 6.3 V., 2.6 V., price "But if we try to move it much more Cathode Ray tube socket with H. Volt- bottom as is proved by the top neon age wiring, 11 Pole Magna!, price 2.40 lamp going out and the bottom one's quickly still, we shall now find a great- 14 Pole Di- Heptal, price 2.40 plate becoming fully covered by glow. er resistance to the motion owing to Cornell -Dubilier Oil Filter tubular we shall mfd 3600 V., price 1.80 Thus the total voltage across the two the inertia of the mass, and Capacitor .1 force in a .02 mfd 2500 V. Sprague tubular resistors no longer balances out to zero, also find that our greatest Capacitor, price .90 but is negative to ground since the elec- given direction has to be exerted at the All types ceramic, mica and oil capacitors, in direc- trimmers, coaxial cable. etc. trons piling up at the top end of the beginning of the stroke that Send 50e for complete catalog including bottom resistor make that end nega- tion, whereas it had to be exerted at the diagrams for RCA. G.E., DUMONT and end when we were moving slowly and ANDREA Television Receivers, free with tive and their shortage at the ground- order $5.00 and more. ed end of the same resistor leaves it the inertia effect was small in com- RCA Parts and Equipment Distributors positive. parison with the elastic force of the World's First Sperialired House spring. In other words the force has In Television ABOVE RESONANT FREQUENCY changed from lagging to ,leading after ELECTRONICS SERVICE & SUPPLY Lastly increase the input frequency passing the natural vibration frequency, Dept. RC, 268 W. 40th Street, up the motor. The con- just as with the electrical circuit con- N. Y. by speeding New York 18, denser now charges oftener per second taining capacity and inductance." -CRAFT for MAY, 1946 570 RADIO The amount of voltage produced at the discriminator output depends on the extent of the frequency swing or deviation and governs the intensity of the sound in radio or contrast of the picture in television. The frequency of the voltage changes in the discriminator output depends on the number of frequency swings or variations per second and governs the pitch of the sound or fineness of picture detail. PARTS This apparatus is a very definite help For RADIO in teaching alternating current theory.

Since the foregoing was written it became Fishing for your radio equipment is o gamble evident that the transformer primary should -you not be connected to the slip rings until the don't know what you'll get or when you'll get it. motor comes up to speed. On one occasion the motor happened to atop with the two cons - mutator segments, which are connected to Let Sun Radio do your fishing for you. We have the collector rings, directly under the brushes. lines thrown every When the demonstrator was started the next out to leading manufacturer, time there was a severe flash which badly and each hook is baited with our highly- regarded burned these two segments, because the d.c. went directly from the brushes through the reputation which enables us to get prime consider. low resistance transformer primary, and as the armature turned the commutator segments ation. interrupted this heavy flow and the arc from self- inductance badly burned the bars. To pre- The result is our half million feet of well- stocked vent a recurrence of this a switch opens the line from the rings to the transformer pri- shelves. No matter what you want, one call to mary until the generated a.c. frequency approaches the resonant frequency of the tuned Sun will probably get primary. it - the FIRST time. FREE OFFER Call SUN First Condensed chart of VISUAL RADIO ALIGNMENT Graphical Symbols for (Continued from paye 540) Note our ONE and ONLY address Electronic Diagrams as standardized by the the output frequency of RMA (includes those un- OSC. No. 2, the SUN RADIO & ELECTRONICS CO., INC. til recently kept secret). external unmodulated r.f. oscillator, to Just ask for iLAddress 635 kc we NEW YORK 7, N. T. would obtain the desired 122-124 DUANE ST. Dept. GR5 signal as follows: BArclay 7 -1840 OSC. No. 2 635 kc 635 kc 635 kc receiver lies in the range covered by OSC. No. 1 450 kc 460 kc 470 kc the FM signal generator (415 to 540 Output Dif- kc) as is the case with the majority ference of Freq. 185 kc 175 kc 165 kc receivers, it is not necessary use If the i.f. frequency to the were 262 kc OSC. external signal generator because the No. 2 would be set at 622 kc: wobbulator's signal is satisfactory in OSC. No. 2 622 kc 622 kc 622 kc itself. OSC. No. 1 430 kc 460 kc 470 kc To discuss some of the units used Output Dif- to align FM ference Freq. receivers here would be 172 kc 162 kc 152 kc unnecessary, as their only essential Note that in both cases, although the difference from the unit in Fig. 2 is that mean frequency is different for the out- they operate higher put frequency, the at mean frequencies band width remains and band widths in the neighborhood the same. Of course, if i.f. of the of the 300 to 400 kc. 8 HILTS IN ONLY 90 SICOND5 W 5 Amplitude of the frequency-modulat- 6 MAINTAINS PROPER HEAT 4 e6 ed signal must 4 remain constant LESS RIMMING NEEDED The 3 7 throughout the entire frequency swing. COOL, SAFE HANDLE Kwikheot a2 Iron is powerful The necessity TIPS LAST LONGER 2 8 I for this will be seen in e1 -225 watts. A CAN'T OVERHEAT 9 Fig. 3, which illustrates the shape of a built -in thermostat typical resonance curve for a single- or LIGHT WEIGHT maintains ideal double -tuned i.f. transformer which is 6 TIP STYLES temperature for best soldering, pre- peaked at 175 kc and has a band width of vents overheating, 10 kc. This curve tells us that the i.f. prolongs life of tips, transformer for which it was drawn is C=. saves retinning time. designed to pass signal Kwikheol is hot, ready a frequency of to use only 90 seconds 175 kc with minimum attenuation. after plugging in. Light Further, as the frequency is increased (14 ounces); well -balanced, or decreased, the amplitude cool handle. Complete with response ! l tip SI I.OD drops off sharply until it falls below AUDI - the level *portaged 3ILITY of audibility for all frequencies below 170 _EVEL kc and above 180 kc. ANAiiA Therefore, the transformer, or strictly speaking, the resonant DIRECTION circuit, is said OF UNMODULATED SWEyP to reject or suppress all frequencies I I I except those lying within the KC = range , l55 160 THERMOSTATIC 165 170 175 180 185 190 195 from 170 to 180 kc. Note SOLDERING IRON that the cali- A DIVISION OF Fig. 3- Output curve, constant signal input. (Continued on following page) SOUND EQUIPMENT CORP. OF CALIF., GLENDALE 4, CALIF. RADIO -CRAFT for MAY, 1946 571, view the curve instantaneously in the form of a trace on the screen of the instrument. But to do this, the sweep frequency of the oscilloscope must be twice the rate at which the output of the signal generator sweeps across the band width and back again (from 170 to 180 kc and back to 170 kc). The G -E TUBE CHECKER Quick, easy, reason is that the trace representing accurate tube checking which saves you time and trouble and the i.f. response curve will not stand happy- that's the job the TC -3P is keeps your customers still on the screen unless this require- built to do. Line Voltage and tube quality, or shorts, may all be checked on one selector switch. Individually operated ment is fulfilled. switches permit placing the proper voltage on the proper pin The sweep frequency circuit of the of the tube. The G -E Tube Checker is available in either Model (TC -3). Write: oscilloscope is a low- frequency oscillator the Portable (TC -3P) or Counter ampli- Specialty Division, Electronics Department, General Electric usually combined with suitable Company, Syracuse, New York. fiers to produce the bright horizontal line across the scope face. The sweep- GENERAL ' j ELECTRIC

Electronk Measuring Instruments

Fig. 4-The single-curve alignment pattern.

producing circuit is a sawtooth oscillator, producing a special type of curve. The voltage rises slowly, causing the spot of light to move across the oscilloscope screen, tracing out a line. On reaching its peak, the voltage fails suddenly to zero, causing the spot to fall back to the left side of the screen instantaneously. Since the sweep frequency is set to twice that of the "wob- L- bulator," the spot sweeps once across Wanted ALIGNMENT the screen as the signal generator is Service Supervisor VISUAL RADIO being swept from 165 to 185 kc, and a (Continued from previous page) second time as it is being swept from by Electronic Organ 185 to 165 kc. In reality there are two brations extend from 165 to 185 kc to curves instead of one, but the second Manufacturer provide a base for the curve. The same curve is not visible because it is exact- must be done with the frequency mod- ly on top of the first one. The reason a base for the for this will become apparent when it open for the ulated signal to obtain Unusual opportunity now the screen of the oscilloscope. is noted that the response curve has under 40 years of age trace on right man. Must be could the same shape whether you go from personality The response curve in Fig 3 and of sound health; have by connecting a 165 to 185 kc or from 185 to 165 kc. people of have been obtained which will enable him to meet load resistor, re- Therefore, when the frequency of the friends meter across the diode average culture or better, make drop across it for a num- FM signal reaches 185 kc the sawtooth influence their cording the with them quickly, and of frequencies introduced by an voltage drops to zero, returning the experi- ber Thinking; sales or other business ordinary signal generator, and then trace to the left -hand side of the screen, ence definitely valuable but not abso- plotting the curve from the data. It and as the sawtooth voltage rises again, from the signal gener- lutely necessary if other qualifications is apparent that the amplitude of the the frequency trav- sweeps from 185 to 165 kc. As the are tops. Position will entail some input signal must be kept constant or ator response going from 185 to 165 kc varies eling. results will be meaningless. Because the cathode -ray oscilloscope exactly as it does in going from 166 is possible to to 185 kc, the second curve falls di- Must be thoroughly familiar with audio serves as a voltmeter, it circuits and components. Must have proven ability in writing effective service notes and installation instructions. Must be able to set up, train and supervise field force.

a e with old established but pro- a 00 Position gressive firm with highest financial rating. Write immediately giving full par- ticulars and complete history of activities for past ten years, in first letter.

Box My-6, c/o RADIO -CRAFT, 25 West N. Y. h i k Broadway, New York, f g variety of conditions, which are explained in the text. Fig. 5 -These patterns indicate a RADIO -CRAFT for MAY, 1946 572 rectly on top of the first, giving the appearance of a single curve. In addition to double curves, single curves are also used. This is accomplished by keeping the sawtooth voltage at zero during the period when the frequency of the generator passes from 185 to 165 kc. The resultant curve is shown Fig. 4. The rising line at sharply Here's a great OLSON bargain: 70 to the right of the curve is the second By -Pass Condensers, made to rigid Olson curve, but it is collapsed into a line specifications. Will withstand voltages due to the absence of the sawtooth de- higher than ratings. Worth much more flecting voltage. than our low price. Order now! 95 POSTPAID Small size (appro.- 11/2"" long, "" dia. ) makes these units right for compact Pane/ lamp Tool circuits. Long tinned copper leads. You with as each Condenser Kit get SEVENTY 600 -V. Tubulars, ordered. Rubber tool grips Fig. 6- Alignment pattern for e.f.c. circuit. follows: bulb for easy installation or QUANTITY CAPACITY QUANTm CAPACITY removal in hard- so-get.at positions. The method of connecting the signal 20 ...... 01 20.__05 Mighty bandy! generator and the oscilloscope varies Send for our free Bargain Catalogs ml. esw sees with the type of circuit to be aligned. ealr to U. S.A. In a receiver which uses a diode detector, the vertical plates of the oscil- ÓcsÖiV ' loscope RAMO WAI?RAYOW should be connected across the Stock diode load resistor. When the receiver #TCA 73 E. Mill St., Dept. 23, Akron, Ohio employs a triode biased detector, a sat- Send me Kits of 70 Condensers each, at $4.95 per Kit postpaid. I enclose isfactory procedure is to open the bias resistor and by -pass condenser circuit, I will receive a Panel Lamp Tool FREE with each Kit ordered. and then to connect the vertical plates of the oscilloscope from the cathode to ground across a 0.5 megohm resistor NAME which has been by- passed with a 250 µµf condenser. It is also advisable to ADDRESS short out the plate load; although this will invert the trace it does not affect the alignment procedure. The FM signal generator is connect- Learn RADOL K ed to the input of each particular stage, just as any other signal generator would be. The order of procedure for visual RAPID alignment is identical to that which is RADIO followed when an output meter is employed. Alignment starts at the back of the receiver and works toward the SERVICING front, feeding the signal into Large stacks assure the fine. and meet the last completo selection. of oll available i.f. amplifier input, the next -to -last, item. and approved for at lowest prevailing prices. Thousands of so on, until the converter is reached. active buyers depend on u. for their entire The object is to adjust the trimmers of Veteran Training Radio repair and replacement requirements. the stage into which the signal is be- Because wo understand service problems, every order is expedited for delivery In ing fed until a symmetrical curve is Our specialized training develops radio repairmen who have 200 hours actual double quirk time. Everything we do Is obtained. This applies equally as well planned For convenience and taridachon to to both the single and double curve servicing experience when they leave oa. ra mar. You will find it profitable to methods. Fig. 5 shows some scope pat- school. Course trains for AM, FM, make Rodolck your buying boodquartera terns commonly used. Television, Broadcast and Amateur. The curves at a, b and c of Fig. 5 in- This is no ordinary course. For par- FREE BUYING GUIDES dicate various conditions of misalign- ticulars write: Be f existing conditions we keep our ment. The curve at d indicates correct customers right up to the minute on avail. alignment. Adjustment IVAN D. LONG, President able merchandise by releasing supplement, of the trimmers fr tly instead of sending our regular will not always result in a symmetri- Big Profit Goid cal resonance curve. Slight departures Western Radio a year. send from exact symmetry are permissible, the coupon now however, if the departure is great, Institute to get these Free such Buying Guide Sup - as it would be when the degree of 1457 Glenarm, Denver 2, Colo. plements as they coupling is excessive and regeneration are issued. is present, the circuit itself should be suspected and examined. Thus, visual was employed. Figs. 5 -f and 5 -g illus- FAST SERVICE! alignment serves as a check on potential trate misalignment and alignment for RADOLEK CO., Dept. C-1 14 trouble in the customer's home, which a typical triple -tuned i.f. transformer 601 W. Randolph St., Chicago 6, 111. Please tend IRE! ,uyI.g aula svpplcments would ordinarily leave the shop unde- such as might be encountered in a high - NAME tected. fidelity receiver. Fig. 5 -h illustrates cor- Fig. 5 -e is the same curve as that in rect alignment for a transformer of sim- ADDRESS 5 -d except that the single trace method (Continued on following page) ORDER FROM RADOLEK

RADIO -CRAFT for MAY, I 946 573 shown in Fig. 6. Many manufacturers provide detailed directions for visual HEADQUARTERS FOR alignment of their particular receivers Equipment and Information which may differ from the very general NAM directions given in this article because of circuit considerations. It is advisable to consult the available technical data on each particular set which is to be aligned to determine if such is the EXTRA case.

SPECIALS LOGIC -A REPAIR TOOL Leach Relay (Continued from page 543) Low Loss D.P.DT. 6V. D.C. Coil ments being normal, he will turn his at- $1.75 Net tention to the capacitors in the set. This 3C'24 G. Tubes FOR YOUR will often involve freeing one end of the Limited Supply condenser from the circuit and checking $1.90 Net for the slow swing of the ohmmeter 10 M.C. I.F. Trans. NEW RIG needle. Doubled Air Tuned Monitor Crystals The direct measurements technique 90e Net has much to recommend it. Since most Type 43B, 7 Mc. $2.83 Net circuit disorders result in a change of 8 x 8 M.F.D. -600 V. Type 43C, 14 Mc. $3.75 Net Oil Impregnated Type 43D, 28 Mc. $5.50 operating voltages, the troublesome com- 4 prong base ponent can often be located rapidly. Not $2.10 Net Also complete Line of: all troubles however, manifest them- NATIONAL EIMAC selves as voltage abnormalities, and in Mail Orders Promptly Filled JOHNSON JONES these cases the direct measurements ap- Amateurs to Serve You OHMITE AMPREX proach becomes a long and tedious TAYLOR rite ADVANCE process. W 6SCQ W W 8 W LG /6-W 6NAT BARKER-WILLIAMSON WfiSSU HALLICRAFTERS CHANNEL SUBSTITUTION To the advocate of this servicing procedure, a radio receiver is the sum total \ Radio Product Sales Company ' of its individual sections, each serving its own individual purpose and adding 138 WEST 15TH STREET its result to the total performance of the LOS ANGELES 15, CALIFORNIA PRospect 7471 receiver. To him, the receiver is divided almost anatomically. It is a collection of separately functioning sections, op- VISUAL RADIO ALIGNMENT erating interdependently, and blending (Continued from previous page) their services to the ultimate result. It follows that a failure in any one section lar design; the single -curve method was will detract from the total operation of the receiver, and the serviceman deals IN STOCK! used. Note that there are two peaks in the curve at 5 -g, and three in the curve with sections. at 5 -h. The possibility of aligning a This type of serviceman is not inter- MEISSNER high -fidelity set as accurately as this ested primarily in circuits, voltages, or signal transfer; he prefers to work 6 Tube AC -DC Radio Kit with an output meter is extremely remote -the result is .a loss in fidelity. with block diagrams. He is interested in The same principles of alignment are purpose rather than means of accom- applicable to FM receivers. Of course, plishment. He is a student of functional the frequency range and the band width analysis. He does not see the receiver of the signal generator must be high as a conglomeration cf resistors, capaci- enough to cover the FM band, as point- tors, inductances, and tubes; he sees it in sections: r.f. amplifiers, ed previously. i.f. may terms of out The stages oscillators, i.f. amplifiers, detectors, and be aligned by connecting the discrim- a.f. amplifiers. inator as a diode detector, so that the He must of necessity have a working drop across the load will provide the knowledge of basic and conventional cir- Frequency range covers the broadcast band vertical deflection voltage for the os- short wave cuit design, but the mental picture ac- from 550 to 1600 Kc and the cilloscope. Fig. 5 -i shows the pattern hand from 6 to 19 Mc. Three controls provided Tuning, Rand Switch and Volume. which indicates correct alignment. Aft- On -off switch incorporated in volume control. er this the discriminator transformer is Complete with all parts, hardware, wire, aligned so as to obtain a trace such solder, speaker, tubes. as that shown at Fig. 5 -k. This curve pictorial and schematic is obtained the pri- diagrams. by first adjusting 8 mary until of the NET. F.O.B. N.Y. the linear portions Cabinet for above (walnut curves are greatest; a secondary check wood) Net $3.75 is that peaks will have their maximum Sbigaing weight, less cabinet 10 lbs. amplitude when correct alignment is obtained. The secondary is then adjusted until the intersection of the two Fig. 4- Set -up for channel substitution test. curves lies halfway between the peaks. companying his servicing is a block dia- Some higher -priced sets incorporate gram as shown in Fig. 3. a.f.c., which must be checked for cor- His first task is to locate the faulty 85 CORTLANDT ST. N. Y. 7, N. Y. rect alignment. A representative trace section. To this end he may arrive by WOrth 2-4415 which illustrates correct alignment is several means, but the true type of

574 RADIO -CRAFT for MAY, 1946 "section" serviceman will use a channel substitute. The channel substitute is an instrument containing and duplicating the different sections of a receiver. It HOW TO PASS ó,é;é,;;, contains ref., i.f. and a.f. amplifiers as :, ; well as detectors and oscillators. In practice, this serviceman will check each section of the receiver in question, by substituting for it the functional CC LICENSE equivalent in the channel substitute instrument. For instance, if he suspects the audio amplifier of the receiver, he will take leads from the audio amplifier EXAMINATIONS... in the channel substitute and connect them between the second detector and FREE BOOKLET Tells you the Govern- merit Requirements for all classes of commercial licenses. Saves you many hours of random, undi- rected study. Assures a minimum of time in get- A ting your ticket! D

CLEVELAND INSTITUTE OF RADIO ELECTRONICS Successors to Nilson Radio School, founded 1939; Smith Practical Radio Institute, founded 1934 E F G H Fig. 5 -How troubles show up on C -R 'scope. RC -5 TERMINAL TOWER CLEVELAND 13, OHIO the loud- speaker of the receiver. If the MAIL THIS COUPON receiver then resumes normal operation, his suspicions are confirmed and he CLEVELAND INSTITUTE OF RADIO ELECTRONICS knows that the trouble lies in the a.f. RC -5 Terminal Tower, Cleveland 13, Ohio section of the receiver. This channel Gel,tlemen: Please send your FREE Booklet, "How to Pasa FCC License Examinations." substitute test is illustrated in Fig. 4. If the audio amplifier is operating Name normally, he goes on to check other sections of the receiver. Next, he will sub- Address stitute the second detector of the channel substitute for the receiver's second City Zone State detector. In this way he will substitute each section of the channel substitute for its corresponding section in the receiver, until the faulty section is discovered. Intense effort is then concentrated on this faulty section to locate its single misfunctioning component. This will involve the use of such test equipment as tube checkers, volt - ohm-milliammeters, capacitor testers, etc. Thus the chan- r el substitute method of servicing is a pure type only up to a certain point, after which some other method of approach Models range hone 330 to FOR RADIO AND must be employed. 35.000 wons, A. C. typos horn 113 to 660 volts, SO, ELECTRONIC APPLICATIONS Several well known shortcuts have become popular sup- 60. 160 cycles, singles or throe -phase and 400, SOO plements to channel substitute testing. For instance, the and 500 cycles, Nngl. ONAN ELECT I; IC GENERATING audio amplifier phase. D. C. type. horn 6 may be checked by shorting the .- heater and to 4000 volts. Alta evail- PI. NTS suppl reliable, econom- cathode at the base of the first audio tube to see if the 60- obie in deal voltage and i, electrical service for electron special hegasncy typos. cycle note is transmitted through the audio section to the - and television applications as speaker. %sell as for scores of general uses. A quick check for r.f. sections employing grid -cap types Driven by Onanbuilt, 4 -cycle gaso- of tubes is to touch the antenna lead -in wire to each of these line engines. these power units are grid caps in turn, to determine which stage of r.f. is inop- of single -unit. compact design and erative. sturdy construction. Suitable for Intermediate frequency amplifiers can be checked by mobile, stationary or emergency probing around with a lead from a service. crystal detector in series Model shown I. from with a pair wac serin: 2000 to of headphones. (Continued on following page) 3500 watts; powered by onsnhailt. wtwo- ylinder. water.cnoted engine. RESONANT' _ R.F. I^_TUNEDTO-+ I.F. -1 DET. -.s E I SIGNAL AM R INDICATOR AND SONS I FREQ. METER 5428 Royalston Avenue L. ANY R.F. _ --J Minneapolis 5 Minn. OR .F. - - ^_ i TUNED V.T.V.M. STAGE B t Fig. 6 -Block diag am of tuned channel analyzer or signal tracer. Ì------n PROBE j FILTER METER I AUDIO y EYE -TUBE I AMP OR OTHER RECT. INDICATOR AUDIO STAGE L------TUNED V.T.V.M,- - - Bt Fig. 7 -For audio circuits, much simpler apparatus may be used.

RADIO -CRAFT for MAY, 1946 575 LOGIC-A REPAIR TOOL (Continued front previous page) While the "channel substitute" approach is the method least used, it is often useful in locating "bugs" which are almost immune to the other methods of servicing. Intermittent reception, a bug causing no small amount of trouble to servicemen, can often be found by FREE WANT -AD SERVICE channel substitution. SIGNAL TRACING z. By FORMER SOLDIERS, SAILORS, MARINES Signal tracing is, in the opinion of Radio -Craft offers its help -wanted columns free for the use of honorably dis. many (including the author) the ulti- charged men in the armed services. State the type of position you seek, pre- mate in servicing. It is efficient because ferred locality, your experience, education, and other details. Confine ad to 50 it deals with the item of primary im- words, or less. Supply name and address. Army veterans send section number portance, the signal. It requires a deep or photostat of discharge paper. Navy men send photostat of discharge paper. understanding of the theoretical princi- Address RADIOCRAFT, Classified Ad, Dept. 25, West Broadway, New York 7, ples of circuit function, and the ability N. Y. Your ad will contain a box number and replies will be forwarded to you. to interpret correctly the indications AVAILABLE given by the signal tracing instrument. Signal tracing is therefore only as good RADIO TECH.; 29. 1st cl. phone; transmitters; Bernard Mishkin, 351 Hinsdale St.. Brooklyn. D yrs. exp., married. S. F. Brook Box Y -I. % N. Y. DIG -1950. as the serviceman performing it. liadlo -Craft 25 W. Vim., New York 7, N. Y. RADIO. RADAR -4% yrs. experience. Interested is RADIO TECH.; 2/c Itad. Telephone. Telegraph in recording, television or redact Salary secondary. It an approach which involves fol- Licenses. Army and Cie. exp. Will accept short Willing to study evenings. Bernard Resnik. 2006 lowing the signal from input the training program. Ted Schwartz. Box Y -2. % Benson Ave., Brooklyn. N. Y. its at Radio- Craft, 25 W. Broadway New York. 7. N. Y. EX -NAVY RADAR TECHNICIAN. 3 years' experi- antenna to its output at the speaker, RADIO- Radar: 2 yrs. rader exp. in Army. C. ence in operation. maintenance and repair. Seek Rubenstein, 1530 St. Nicholas Are.. Now York position with a future In Radio. Radar or Tele- and determining at which point it is lost 33. N. Y. vision. At present I am attending R.C.A. Inst. RADIO Technician and Operator. 1st class Tele- evenings. Salary is secondary. J. J. Korngold, 154 or distorted. For localizing hum, tran- phone License, 3 yrs. Army experience. C. Quint, Kings 1st Walk, Brooklyn. N. Y. sient voltages, noise, and distortion, 181 Riverdale Ave., Brooklyn 12. N. Y. RADIO. RESEARCH LAB. ASSIST. Experience sig- RADAR -RADIO TECH.; lap. in F.M., Broadcast- radio repair. Tech. school grad. Electrical mech. nal tracing is the last word in servicing. ing. F.C.C. Lic. Seek any Electronic Field. N. L. Polasky. 612 Ocean Ara., Brooklyn 26. N. Y. Miller. 1494 Crotona Park East, Bronx 60, N. Y. RADIO TECH.. coll. grad., exp. Army maint. re- Signal tracing may be accomplished COMM. TECH,' 3'4 years exp. A.M., F.M., pair seers.. trans. M. Jooefsberg, 981 Willoughby Y.B.F. Instructed Mechanics 2'f- years. Desire in- Ave.. Brooklyn 6: EV 7 -3076. with either an oscilloscope or a tuned teresting work. L. Solomon. 3127 Coney Island RADIO 24; arms; salary Avenue. TECH.; exp. 3% Yrs.: VTVM (vacuum -tube voltmeter). This Brooklyn 24. secondary. fob with opportunity. Ben Greenberg. RADIO OPPORTUNITY; Hare G yea. top radio 2725 Barker Ave.. Bronx 67. M., FCC License. and largo finished room avail - choice, like so many others in radio nble. RADIO. 3% yrs. exp. Navy radio tech.. adaptable to Desire ideas. assistance for production basis. any F. Guaru, 163, Himrol St.. B'klyn 21. servicing, is largely a matter of pref- M. Koffer. 743 Hendrix Street. B'klyn 7. position. N. Y. RADIO COMMUNICATIONS: pos. with future, YOUNG MAN mechanically inclined, interested in amateur license. knowledge typing. David H. Bier- erence. Radio. Seeks position with future. 3 years A.A.F. man. 2063 Mapes Ave.. Bronx G0. With oscilloscope, experience. Sidney Davidson. 1169 E. New York RADIO TECHNICIAN: exp. receiver. transmitter; the the signal in Ave., B'klyn 12. N. Y. -l'it 2 -0818. interested in any phase of radio, electronics. Marcus the receiver deflects the electron beam in RADIO TECH.: Oper. Mait. Conni 1. B'deast, Wittenberg. 805 St. Marks Ave., B'klyn 13. G.I. Radio exp.. FCC Mc's. Murray Brown, 149 So. RADIO. electronics, 3 yrs. exp. Army. civilian the cathode -ray tube. A graphical rep- 9th Street. B'klyn. N. Y. EV 7 -5897. schooling tuft,. P. A. M. Shack. 1855 E. 13th St., RADIO -RADAR Tech.; 1/c phone license. 3 yrs. B'kyn 29: ES 5.5967. resentation of the signal voltage is thus army electronics. M. Bayent. 1710 w. 9th St., RADIO REPAIRMAN; 4 yrs. clv. & army exp. Brooklyn 23. ES G- 0903. H. Zolinsky. 501 Powell St.. B'klyn 12. obtained. These waveforms can then be RADIO; 4 yrs. civilian exp.: 3 yrs. army. 3 yrs. RADIO SERVICING. 3 yrs. Army exp.. aviation judged for amplitude gain through a maint. school. A. Bindler, 961 Barbey St., Brook schooling, willing to learn. Lochart. 641 E. 175 St., lyn 7. Bronx 57. circuit or stage; for distortion, unde- RADIO TECH.; G yrs. exp., ex-Naval radar, RADIO TECH.; comm.. Army exp.. AM. FM. tele- V.B.F., will work firm. S. Rosenstein. 1826 Bath - vision, accept apprenticeship program. Apt. 2D. 118 sired attenuation or complete signal gate Ave., Bronx 57. 2d Ave.. N. Y. 3. RADIO -RADAR Tech.; 4 yrs. exp. mainte., re- 3 willing learn. loss, transients, hum, and noise. pair; RADIO MECH.; yrs. AAF exp.: to knowledge camnunicetiot equip. B. Nathan - H. Berman. 756 Saratoga Ave.. B'klyn 12. If the sweep frequency of the oscillo- sors. 2872 Bright. 9th St.. Brooklyn 24. RADIO TECH.: 4 yrs. exp.. AM & FM trans. & ELECTRONICS, exp. tech.. civilian exp.. desires rec., accept apprenticeship. A. Rubin. 156 So. 9th scope is not high enough to spread the work In field. D. Loran, 395 Ocean Ave., St., B'klyn 11. Slonlm, Brooklyn 26. BU 4 -2815. DE FOREST Student: desires position: postwar waveforms, a broad band of light will RADIO TECH.; civilian exp.; 2 yrs. army. 3 yrs. possibilities in radio servicing: 2% yrs. machtnest willing worker. A. Hausmann. 1447 Longfellow exp. A. Branic. 531 W. 151st St.. New York 31. appear on the scope screen when check- Ave.. Bronx 59. DA 9 -0332. ELECTRONIC TECH. two years nary experience ing in RADIO TECH.; expd tester, troubleshooter. inb- maintenance, installation radio, radar; knowledge the signal the r.f., i.f., or oscil- uilt.; 3 yrs. Dig. college. S. Geller, 1879 Prospect trigger. video circuits; collego grad. Box A -3. % lator sections. This makes it impossible Ave.. Bronx 57. Radio- Craft. 25 West Broadway. New York City. RADIO WORK Desired: limited exp.: hold oper- B.S.. Army radio. radar background, license. EX- CAPT.. 27 to determine the exact shape of the sig- ator's school nights. M. l'etroQ 140 extensive experience all phases wartime Loran pro- Baruch PI.. N. Y. 2. gram, pre -war industrial purchasing exp., can qual- nal voltage. An amplitude measurement, RADIO RADAR; 3% yrs. exp.; AAF instr.; drafts- ify for executive or purchasing assistant, sales en- however, is man. H. Rosenblum, 205 Sea Breeze Are.. B'klyn gineering. Box A -4. % Radio- Craft, 25 West clearly indicated, and volt- 24. ES 2 -0909. Broadway. New York City. age gains and signal transfer may thus RADIO 10B -2 yrs. Army radar. exp.; wages RADIO TECHNICIAN -22. three yrs. with AAF. secondary; 23. M. Yochel. 2773 E. 15th St., Rrook,vn interested all phase of electronics. Going to collego be noted. 29. nights. Robert Kreisler, 798 Saratoga Ave., B'klyn RADIO TECH.; 34. yrs. exp. repair, maint.. radio, The signal is followed from the an- radar equip., signal corps. A. D. Aran, 291 Mon- RADIO TECH.. 27. exp. P.A.. movie sound sys- tauk Ave., Brooklyn 8. AP 7 -1527. tems, allied field, N.Y.C. or L.A. L. Kruger, 2060 tenna input, checked at all the grids and RADIO Wireman; 3 yrs. exp., 9 yre. exp. elec- 23. N. Y. condensera. E. 9th St.. B'klyn plates, and finally traced to the speaker trolytic J. Hanish. 1966 62d St., RADIO ENGINEER -1st class radiotelephone, 10 Brooklyn 4. 6 BE -8156. radio 5 Army exp. ELECTRONICS; Navy; exp. years amateur years diversified voice coil. It may be checked at both civilian; audit; LHF Peter Korn. 188 Bay 25th St.. B'klyn. N. Y. technique; radio -radar circuits; 20. D. Schaffer- A.A.F. RADIO -RADAR mechanic. 3 ore. exp . sides of coupling transformers and man. 775 So. Blvd.. Bronx 55. all RADIO bmtchwork, test equip. Including oscilloscope, con- Repairman; 3 yrs. army training; exp'd: struct -align euperhets. A.C. -D.C. power units, etc. coupling condensers to see if the signal 23, married. O. Spiro, 652 So. Blvd., N. Y. 55. J. Goldstein. 969 Bruckner Blvd.. Bronx 59. voltage is passed and if no RADIO TECH.: 2 yrs. army exp.. start as trainee ELECTRICAL -ELECTRONICS; 3% yrs. 1/c Navy distortion lab. aaat. M. Kramer, 1256 Brook Ave.. Bronx 56. electrician; willing to work and learn' desires op- has been introduced. Fig. 5 shows the RADAR TECH.: 3% yrs. exp. excel. electronic portunity: night engineering student. Box A -2. % trng.. latest airborne mullet. I. Gerstein. 612 Radio -Craft. 25 West Broadway. New York City. waveforms indicated at different points Argyle Rd.. Brooklyn 30. RADIO, RADAR. ELECTRONIC TECHNICIAN - in ELECTRONICS; knowledge radio and electrical Nan'. 26. 2% yrs. exp.. 1% yrs. collego. stimulant the receiver. theory and elec. drafting: 22: B.S. grad. R. Serge, personality. Desires position with progressive firm In Fig. 5, A indicates the normal sig- 500 W. 213th St.. N. Y. 99. LO 7-9817. Built Nary transmitting and receiving base. Bernard RADIO Schmeltzcr. 516 E. 11 St., N. Y. 9. N. Y. nal present at any point in the set's TECH.; S yrs. coll. in radio eng'g. Dia. RADIO TRAINEE-3 yrs. Army exp. Seeks work experimental work. D. Jacobs, 107 Hart St.. Brook- in electronic fields. Ago 24. earnest references. Box or B lyn 6; EV 8 r.f. i.f. sections. represents the -4849. A -1. % Radio- Craft, 25 West Broadway. N. Y. C. RADIO TECH.. 3 yre. exp., sock job in lab.; RADAR: know shipatting of navy radar installation same signal after it has been amplified. willing to work. H. Reiner. 47 Bay 26th St., welder. Robbins. 314 Brooklyn completely; electric chauffeur. 14. E. 98th St., Wklyn 3. The ratio of the height of signal B to RADIO. Telegrapher Oper.: 2% yrs. army exp. A. CREATIVE-that's the word for "Thinker Upper." t:Ye height of signal A is the voltage Diamond. 653 Marcy Are., Brooklyn 6. radio program director. news editor, writer, public RADIO TECH.; married; 2'h yrs. exp.: AM, FM relations man with many interesting projects up his amplification between these two points receivers, transmitters; apprenticeship accepted. sleeve and --- colorful record. (From PH D to Psy- A. Lender. 125 Ten Eyck Walk. Brooklyn 6. chological Warfare.) Excellent references. Emil of measurement. RADIO TECH.: 22; 3 yrs. exp. AAF; attend coll. Lehman, 514 Third Ave, Asbury Park. N. J. nights. B. Kreisler, 738 Saratoga Ave., Brooklyn 12. YOUNG VETERAN: 24, married. 3% yrs. service C of Fig. 5 shows the i.f. or r.f. sig- RADIO OPERATOR AND TECH. interested in a as radio mechanic and telephone linesman, willing nal and the presence of super- imposed job in the radio field. Have been a radio operator to learn any electrical trade. Harry .Joseph O'Brien, in the Army for three years. Also have a license. v5 Division Ave. B'klyn 11, N. Y. noise voltages. If these noise voltage peaks are regular and recurring, they

576 RADIO -CRAFT for MAY, 1946 are probably caused by some mechanically rotating or vibrating device. D of Fig. 5 represents the signal ARMY AND NAVY voltage at the plate or grid of the local oscillator. A straight narrow line with no vertical deflection at point D would SURPLUS BATTERIES reveal that the oscillator is inoperative. ALL NEW - IN ORIGINAL CASES Incidentally, this same pattern (D) found in Signac an audio stage would indicate Corps Mfg. Type Description Quantity Case Price undesired oscillation in that stage. Type per Case Only E of Fig, 5 is the signal expected to 22% Volt "B" be found in the audio section. Once BA -2 Burgess 4156 3" x 33" x 2946" 40 $0.07 each again the comparative amplitude of this 0¡ Volt "C" signal at any two points is a measure- BA -27 Burgess 2370 3%" x 4" x 1%" 54 .07 each ment of voltage gain. Burgess #2 - F of Fig. 5 represents the audio sig- BA -30 Eveready 950 1% Volt Flexible Cell 600 .02 each nal being distorted as a result of the Burgess 4FH 13¡ Volt "A" tube operating beyond the linear portion BA -35 Eveready #6 Screw Terminals 32 .07 each of its characteristic curve. Overdriving Burgess 5308 45 Volt "B" the stage or improper bias on the tube BA -36 Eveready 762 -S 574" x 4346" x 29%" 12 .12 each will give rise to this condition. Combination Form G shows the signal in an audio stage Burgess 5A100 6 Pack 734 Volt "A" which has harmonic distortion. Trans- BA -39 Eveready 349 150 Volt "B" 6 .25 each former and impedance coupled ampli- Portable Combination fiers are easily susceptible to this type "A " -"B" Pack 134 of distortion. Volt "A " -90 The presence of power frequency hum BA -48 Burgess 6TA60 Volt "B" 20 .35 each is indicated in H of Fig. 5. In attempting 45 Volt "B" to locate the Screw Terminals with origin of this hum, it is Burgess Z3ON Insulated Junior Knobs often wise to check the power supply BA -53 Ray -O -Vac 452 13/8"x3" x 4%" 32 .12 each and decoupling networks first. Burgess M -30 45 Volt Portable "B" While the cathode-ray oscilloscope is BA -59 Eveready 482 5%" x 396" x 1%" 24 .35 each a versatile and widely applicable instrument of servicing, it is not expressly designed for the job of signal tracing. RADIO ELECTRIC SERVICE CO., INC. The "tuned vacuum -tube voltmeter" is N. W. COR. 7th AND ARCH STS., PHILADELPHIA 6, PA. designed solely for this purpose. The BRANCHES 3145 N. Broad St., Philadelphia, Pa. 219 W. 8th St., Wilmington, Del. tuned VTVM's on the market differ 5133 Market St., Philadelphia, Pa, 1042 Hamilton St., Allentown, Pa. slightly in design, but are identical in 513 -515 Cooper St., Camden, N. J. 9 North Second St., Easton, Pa. principle. They are known commercially as "Chanalysts," "Analysts," or by similar names. The IMMEDIATE DELIVERY! tuned VTVM picks up the sig- APPROVED nal at any point in the circuit, passes it Model A -100 I SIGNAL GENERATOR through a detector circuit (if not al- e R.F. BANDS 100 Kc. -310 Ke. 31r. ready an audio signal), and actuates Xe.-1000 200 Ka.. 32ÓÓ Rc.- some indicating device such as a meter 10.0 Mc. 10.6 Mc.26 r Mc., 21.2 Me.-52 Mc. or magic -eye tube. CONTINUOUSLY VARI- - ABLE RF.AF fine atten- Fig. 6 ,P illustrates this circuit arrange- E TERNALI MODULA- TION FROM 40 to ment. The signal is being picked up at 30.000 cycles. MIMI"®®M® L MOCyycle,LA any point in the r.f. oscillator, or TNONRAT NEGLIGIBLE4 40 HARMON- i.f. sections, is then fed into a resonant IC OUTPUT. co menlete with all tubes, Net Price $47.00 circuit tuned to the signal frequency, cables. instruc. ... iconnectingkons. etc. Battleship gray -Circular on R ft amplified and passed through a detector, crackle finish. size: 12 C.O.D. orders should be ac- and the audio voltage shown by the in- 10 x 0563" ompaniedby25 / deposit. dicating device. SCENIC RADIO & ELECTRONICS CO. If the signal is present, the indicating 53 Park Pl.. New York CIty 7 device will show this and give a measure of the signal amplitude. The fre- approach should be compatible with the quency of the signal being checked is serviceman's type of mind. In recent indicated by the calibrated dial of the years the trend has been towards signal AMPERITE resonant input circuit. tracing. This approach is becoming In checking the signal in the audio more and more widely used. In radio amplifier section, it is only necessary to work any of the three approaches can _ amplify this signal and apply it to an be made successfully. In electronics, ra- indicating device. This indicating device dar, television, and any other circuits may be an a.c. meter responsive containing, non -sinusoidal waveforms, to the signal tracing with an oscilloscope is not 51 audio frequencies. It may be a d.c. in- ADRESS & dicating device; in which case a rectifier only commendable but practically a or filter circuit must be employed to necessity. MICROPHONES change the audio signal to a d.c. voltage. CORRECTION THAT SURPASS This arrangement is shown in Fig. 7. An error appeared in the article, A.C. THE HIGHEST RE- KONTAK MIKES The tuned VTVM is especially use- Voltage Measurements, on page 250 of QUIREMENTS OF ful because it will not only trace the the January issue. The fourth equation BROADCASTING, signal and measure its amplitude, but of a series relating to Figure 4 reads PUBLIC ADDRESS, also indicate the signal frequency. + L. This equation should We have now discussed these three read, I = Im + L. í AND RECORDING approaches to servicing: direct measure- Our thanks to Mr. L. W. Lechtreck, of Write for Catalog ments, channel substitution, and signal St. Louis, Mo., for calling this to our AMPERITE COMPANY tracing. As stated earlier the type of attention. 561 BROADWAY NEW YORK. N. Y. RADIO -CRAFT for MAY, 1946 577 A VERSATILE VTVM HARD-TO-GET PARTS-\ (Continued fron page 535) POWERFUL ALL -PURPOSE INDUCTION MOTOR within the linear portion of the char- voltage on both sides of the meter, ob- IDEAL FOR EXPERIMENTERS -1O1 USES Sturdily constructed to p c ision acteristic while still impressing a great- viously no current will flow through it. standards, this self-startingr Pole induction voltage on the than would other- When a potential of one volt is applied enough number 1f uses. er grid Some aof these are: Automatic . Ind Devices. Current Interrupter.. wise be possible. between grid and ground several things Electric Display. EPhotocell Control happen all at once. First, the grid rises Devices. Electric Vibrators. Small AN EXPERIMENTAL HOOKUP Grinders. Buffers and Polishers, one volt. Then the voltage at the cathode Miniature Pumps. Mechanical Mod- els. Sirens, and other applica- A few calculations plus a breadboard 0.5 to tions. rises about volt with reference Consumes about IS watts of experimental setup soon showed that ground, since the tube passes more cur- power and has a speed 3.00 n cnnle with a value of cathode resistor suffi- rent. This causes a curent of one mil- stry unit will constantly oper-- atesudt a 8 -i h turntable loaded to 2.2 a with 200 lbs. dead weight-THAT'S POWER! cient provide about volts of bias, liampere to flow through Rl-roughly high hasDl4 convenient tang studs: Isai/e °Ìon voltage loss of about 80 percent result- one milliampere. The exact current that diameter, self-aliening retaining -b rbesiá edfor 1110.20 50.80 ed. Fig. 1 illustrates the preliminary flows depends on the setting of Rl. This cycles. A.C. only. Shp. Wt. 2 lbs. ITEM NO. 147 circuit tried. With Rl set near the value extra current must also flow through YOUR PRICE $ 97 5 of the cathode resistor and with one the 125 -ohm biasing resistor. This tends volt actually impressed between grid ULTRA MAGNET to lower the cathode -to- ground voltage LIFTS MORE THAN 20 TIMES and ground, the meter would deflect slightly-by .125 volts to be exact. When ITS OWN WEIGHT about three -quarters of full scale. Re- LITTLE GIANT MAGNET equilibrium is reached-and this all LIftn 5 lbs. ily. Weighs 4 o. ducing the size of Rl made it possible Made of ALNICO high.magnetic happens practically instantly-the cath- steel. Complete with keeper. World' to obtain full scale deflection with a one - most powerful magnet ever made. ode is established firmly 0.4 of a volt The experimenterof and hobbyistuses for volt signal. The unhappy feature was higher than it was previously. This ex- this high quality = rmanent magnet. Measures la/a' 1t/a. Shin. 'St. that the meter reading was not linear. tra voltage has caused enough current lbs. ITEM When half a volt was applied, the meter YOUR PRICE $1.50 to flow through the meter to bring it to did not read 0.5. Further checks showed full scale deflection. The meter does not GENUINE MICROPHONE TRANSMITTERS that in Fig. 1 the cathode -to-grid wind itself around the needle stop be- Regular telephone transmitters taken from a large change was about 0.8 of a volt when cause the current that flows through it telephone supply overst gout one volt was impressed across the grid. also flows through Rl and raises the tlY Ó 9 In other words, the linear portion of voltage at that point almost 0.4 of a to rmf s. call systems,, inter- communications was telephone dr- the tube characteristic being ex- volt. The cathode to grid voltage has cults. house -to-house or farm-to-farm lines. ceeded. The cure for that was to in- changed only 0.6 of a volt. Tests showed to talk through your redlo or crease the size of the cathode resistor. that the response was linear which was dictaphone pIck up. Use- ful placements on bat- This would make the cathode follower to be expected since tery- operated rural tele- the "signal" was phone Ones. more efficient and therefore would THESE ARE GENUINE there within the linear portion of the tube TRANSMITTERS, MADE BY KELLOGG. WESTERN be ELECTRIC AND BpTeRaOMBERG- CARLSON. excellent In a larger cathode swing and conse- characteristic. appearance and operation. remarkableWt. 1e and Oneese loom ea to these times. quently less difference between grid and It can be shown that the output im- ITEM rouR PRlce $1 .50 cathode. pedance of a cathode follower is con- AMAZING BLACK LIGHT!! siderably less than the actual value of Powerful 250 -Watt VltraViolet Source cathode load. This means that a cathode ucer of ulra- vil lightittl f or follower can be comparatively heavily general otnoettexperimental meis .. Makes all °Snores. loaded rent substances brilliantly luml without changing the amplitude nescent. allo transfor mers of any needed. of its output. lamp Brings y ut beau-- tiful opalescent hues in various Because a low value of Rl will re- types of materials. Swellwell for amateur parties. play etc.: to quire more current to a nl,talnn unique lighting effects. produce given B ulb only. Shp. Wt. 2 lis. value of voltage drop across it than a ITEM NO. 87 YOUR PRICE $1.95 high value, R1 can be used as a sensi- WESTERN ELECTRIC BREAST MIKE tivity control. Within reasonable limits a Anti its value will not affect the operation of c ft IcaarÚ icrophone. It weighs Fig. 2- Fundamental circuit of the meter. only I lb. the cathode comes follower. When Rl, for in- mounting svel- A value 1000 gútic adlustment ans1awit so that It can be of ohms was selected. stance, is set at 200 ohms, an extra cur- to any desirestraps:position. There It was found that to keep the bias on rent of one ma through it will cause a goes around eck.. the oti,er around chest. O Straps he the tube near the 2.5 -volt region, some voltage rise across it of 0.2 of a volt. A snapped on and off quickly by an ingenious mike circuit changes would have to be made. 300 -ohm value would hs excellentea be cause a voltage adapted for home broadcasting or Either the grid would have to be placed rise of 0.3 of a volt. It can be readily dismount) gabreastplate, m liie used a it above ground, or the cathode resistor seen that the voltage at the cathode Comes °écomnplete with 6 -foot would r M and harts rubber plug. Finished Ie .. nn:o,llser have to move to the sub -basement. would have to be higher to maintain the plate. n n- table. Shipping weight. 2 Ibs. The circuit shown in Fig. 2 was there- same meter reading ITEM NO. 152 $1.95 if Rl was 300 ohms YOUR PRICE than it would if Rl WATTHOUR METER 1 20MEC 2500 1500 overhauled and 3 117L7 were only200 ohms. Completely service. for Immediate Y IV 750K Dayesigned for regular 110 - I 72f +30V Rl will require volt. 00 cycle 2 -wire A.C. Q bW Irl l Simple to +110V y llneatand l initial setting when 2 ires 9MEG 2500 2 wires the load. Sturd- e ily constructed In heave IoV 10.01 the unit is built case. SW' high. 01/a' metal .9MEG v +2_4V + + and readjustment house. 0. E. pFL Wayne. Sangamo or other a ilable 100v IK 16 whenever make. Shp. W4 14 los. fT the tube 75K 4V 250VI ITEM NO. 93 $4.95 - is changed. It YOUR 400V 00-IMA 12.5K 125 45 0-IOM-AILII should not be nec- uo II7VAC essary to adjust it HUDSON SPECIALTIES CO. 900V LO V O-IOOMMIA 12.5K 9II very often. In 40 West Broadway, Dept. RC -5.46, New York 7, N. Y. the I have ircled below to numbers of the Items I'm SW 0- 50oVVi' four months this ordering. My full remittance of S (In hipping charges)harges) la enclosed (NO C.O.D. unit has been in ORDERS UNLESS ACCOMPANIED WITH A DEPOSIT.) Fig. 3- Schematic of the volt- milliammeter as finally adopted. OR my deposit of S is enclosed (20ofe daily operation, it -\red). hip Mer C.O.D. for balance. NO C.O.D. ORDER FOR LESS THAN 55.00. BE SURE TO IN fore adopted. The voltage distribution is has not been CLUDE SHIPPING CHARGES. found necessary to change Circle Item N159wanted: as indicated. -cathode 47 eO 87 152 33 The grid voltage the setting of Rl. A setting of between difference is maintained at 2.4 volts. 200 and 400 ohms will be found to be cor- Name rect for almost any tube used. Remem- Address HOW IT OPERATES ber, to increase sensitivity, lower the Please Print Clearly value City If the thousand -ohm zero -set control of Rl. State is adjusted to provide exactly the same (Continued on following page) 578 RADIO -CRAFT for MAY, 1946 The final voltmeter circuit is shown in known voltages of the proper magni- Fig. 3. The transformer was wound by tude. If the resistors in the input cir- hand on a core from a small power cuit have been carefully selected, a METERS transformer. About 600 turns of No. 26 rough check to make sure of correct NEW WESTON RADIO SERVICE METERS enameled wire were used for the prim- wiring would be all that is required. IMMEDIATE DELIVERY ary and about 500 turns for the sec- The calibration just described is ondary. It was a tiresome job, but no simple and reasonably accurate and can Model 779 $69.19 small transformer with a slight step - be done quite quickly. It should be ac- The Newest Supersensitive Analyzer down ratio was to be found. It would curate enough for all practical pur- be unwise to build the unit without a poses. Model 772 analyzers $49.50 transformer, though at first thought it THE MILLIAMMETER CIRCUIT Model 777 Tube checkers $49.50 would seem that dropping resistors Current scales can be included or not could be used. The transformer is need- as the builder desires. The simplest way Model 697 analyzers $24.00 ed for isolation, and if it is being hand to obtain the proper value of shunts is Model 785 Industrial circuit tester. .$93.75 wound it might just as well drop the to use another milliammeter as a stand- Model 666 selector 16.83 voltage a little too, thus saving the cost ard in series with this one. With a volt- Model 766 Televerter. 6.000 volt 18.75 of a resistor. Without the transformer, age source of the proper magnitude- Model 766 Televerter. one side of the a.c. line would be con- a dry cell and variable resistor will do 10.000 volt 22.00 nected through the 125 -ohm biasing re- quite nicely-the selection of the shunts NEW SURPLUS METERS sistor to the negative probe of the elec- is quite simple. From a discarded po- tronic meter. If this probe were then tentiometer select resistance wire of WESTON ROUND FLUSH BAKELITE to be clipped to the chassis of an a.c: about the right length. Connect it as a METERS UNLESS SPECIFIED d.c. receiver and the line plug happened shunt across the terminals of the meter OTHERWISE to put the receiver chassis at the op- Model 801, 31/2". 0 -10. 0.15, 0 -60, 0 -100, in this unit. Then apply the voltage to 0-800, 0 -1000 Milliamperes D.C. 4.95 posite polarity to the voltmeter, it both meters in series and adjust the be so would be Model 301, 3W Sangamo 500 -0 -500 would not good. There variable resistor controlling the voltage Microampere Movement. 100 -0-100 110 volts across the biasing resistor, until the standard meter reads the de- Scale 3.95 lead lot of which would quickly to a sired current. Then vary the length of Model 506, 21" 0 -10, 0-50. 0 -200 smoke and a burned-out resistor. resistance wire used as a shunt until Milliamperes, D.C. 3.50 both Model 643, Surface Mounting. 0 -150 CALIBRATING THE UNIT meters read the same. The resistance wire can be wound around any volts D.0 8.00 After the unit is built, it must be convenient form and cemented after the Model 801, 8w' voltmeters 0 -150 volts calibrated. The easiest way to do this proper length has been determined. D.C. 4.60 is with a couple of storage batteries, The 0 -1172 K.V., D.C. complete with 1000 same procedure can be followed on the ohm per volt resistor 6.95 though dry batteries can be used. If 0 -4 K.V., D.C. complete with re- other ranges. It may be advisable to sistor 7.95 storage batteries are available, connect use copper wire on the highest range them in so 10 volts is avail- Model 476, 81/2". 0 -8 volts $4.00. 0 -130 series that since a resistance of only 0.22 ohms is able in -volt steps. Accuracy of cali- volt $4.50. 0 -160 volts 5.95 two approximately what will be needed. is bration will depend on the exactness of It Model 517. Round Flush Ring Mount- easier to work with and easier to solder, ing, 0- 15 -25 -75 volta A.0 2.95 the voltages, so it would be wise to check though it has the slight disadvantage Model 517, 21/2". 0-160 volts A.C 2.95 them with the best meter available. If that its resistance tends to increase they are fully charged, each cell may slightly as its Model 476, 81 ". 0 -4 Ampere White - provide a potential of slightly more temperature rises. scale 4.60 The values listed in Fig. 3 are cor- 0 -30 Ampere A.C. Black Scale 4.00 than two volts, and allowance should rect a meter with A for an internal re- Model 642, 4t/ß' Surface mounting. be made for this in the calibration. sistance of 100 ohms. The 45-ohm 0 -150 volts A.0 9.00 re- 0 -15 Ampere light load across the batteries will bring sistor in series with the meter brings A.0 8.00 them down to an almost exact 2 volts. the resistance of the particular meter Model 801. 0 -25 volts A.C. Rectifier constructed in type 2000 ohm per volt 6.95 If the unit has been used in my unit to 100 ohms. accordance with Fig. 3, be sure that the Model 506, 214 ". Decibel Meter -10 to If the circuit is carefully followed +6 Black Scale 3.95 volts -milliamperes switch is set for and close -tolerance resistors in the in- volts. Plug the unit in the a.c. line, and put network for the voltmeter selected, set selector to 10 -volt WESTINGHOUSE the switch the the builder of this unit will have a volt- scale. Use terminals Y and the common meter that should compare Model NA 33, 2% ". 0 -150 volts A.C 1.98 negative if storage batteries are used favorably with the most expensive commercial Model NX 35. 31" 0 -24 Milliampere for calibration; terminal X and the com- models. movement. with 0 -24 MA and 0 -1200 mon negative if dry batteries are used. volt scale 2.25 After allowing the unit plenty of time Model RX 35, 31/2". 0 -15 kilovolt meter, 1 milliampere D.C. move- to warm up -at least five to ten minutes ment, complete with 15 megohm, 15 -accurately set the meter with the 1000 kilovolt tubular resistor. List price ohm zero-set. Then place the meter OSCILLOSCOPE $165.00. YOUR cost only 16.50 probes across the 10 -volt source and ob- Model DY -2, 41/2", 0 -21/2, 0 -50, 0 -60, Western Electric used Signal Corps 0 -70, Ampere A.C. surface mounting serve the reading. If the meter needle 5" oscilloscope made for SCR 268 White Scale 8.00 reads more than full scale, increase re- Radar set. Contains power supplies Model -DY -2, 41/2". 0 -150 volts A.C sistance Rl. If the meter needle reads 115 volt, 60 cycle; amplifiers and surface mounting Black Scale 9.00 less than full scale, decrease the resist- controls for vertical and horizontal Model DY-2, 41/2". 116 volt, 60 -70 cycle ance provided by Rl. Once the value of positions, sensitivity, spread, focus frequency meter White Scale 35.00 Rl which gives full -scale deflection is intensity, and fixed frequency sweep. CE Type DW94. Radio Frequency am- obtained, the linearity can be checked meter. 2 %" Black Scale 0 -1 and 0 -8 Contains 13 tubes. Comes complete Ampere 2.96 by connecting the meter probes to suc- with diagram showing how to add a cessively lower voltages. Be sure that Model DO -40, G.E. 3" Round Surface sweep circuit. Excellent for radio Mounting Meters. 0 -2.5 and 25 milli- the zero -set is accurately made since servicing and laboratory experiment- amperes, 0 -300 Milliamperes. 0 -900 will volts. All D.C. All ZERO CENTER 2.50 it require resetting when R1 is ing. Model BC 412 A and B. Ship- changed. ping weight 200 Add sufficient postage on P.P. eiders. lbs. Excess will be refunded. If dry batteries are used the same all complete. ONLY 32.50 procedure can be followed with the exception that a total of 30 volts should Maritime Switchboard be available for a complete check on Maritime Switchboard the linearity. Terminals X and the com- 336 Canal Street New York 13, N. Y. 336 Canal St. N. Y. 13, N.Y. mon negative should be used. Worth 4 -8217 Worth 4 -e2I The other ranges can be checked with

RADIO -CRAFT for MAY, 1946 579 PLUG -UGLY ELIMINATOR EE 1 By MAURICE A. KAY Home object of the invention is to pro- bottom of the cylinder regulating the ._7he ofRAD /O_. THEvide a means by which a person lis- flow of air to the space inside the cyl- tening to the radio can be relieved of inder. By screwing this valve in or out, For over 25 years excep- listening to commercial announcements the rate at which the air can enter the tional values and service in which he may have no interest or cylinder may be regulated. to customers all over the which may even be offensive to him. Secured to and moving with the pis- world. It operates by the listener pressing ton rod is a bent arm, one end of which a button whenever the announcer begins is attached to the piston rod. The other Here Again . . . his commercial. This shuts off the cur- projects through a slot in the case. This the and eliminates com- BC -412 "Scope" rent to set the slot has a notch formed therein. This complete with II tubes plus mercial. After a predetermined time in- 5" Cathode, operates on S3500 terval, the current is automatically CURRENT SUPPLY RADIO. 110 V. A.C.... turned on without effort by the listener RECEIVER and the broadcast is resumed. Many persons turn off their radios IELIMINATOR BC -603 Tank Receiver, cost Govt. whenever a commercial announcement $900.00; FM freq. range 20 to 27.9 comes on. Especially those obnoxious Block diagram of the commercial eliminator. mc. Can be converted. $ ones -babies crying, whistles and fog Extra Special. Order at bent arm has the end finger once horns blowing, etc., etc. Often the per- at a button son either forgets to turn the radio on and a pointer which registers on a scale. again or turns it on while the announcer When the listener hears the announc- Selsyn Motors, 110 V., 60 is still proclaiming. er start a commercial, he simply presses c., with indicator. Extra $1800 To perform the operation described the finger button. The bent arm to which Special. Pair + above, I use an apparatus consisting of the finger button is attached pulls down a baseboard which supports a case in the piston rod, causing the switch to BC -423 Modulator the top of which is located a switch. The open and abate the nuisance. As the Self contained power supply can be switch has a stern which when pressed easily converted to a 2 meter trans- SWITCH NORMALLY OPEN mitter. Complete with tubes $10.00 closes an electrical circuit. The switch BC -156 Transmitter & Receiver is so constructed that it is open unless Complete with phones, generator, antenna and ground, spare parta, restrained by pressure on the stem. etc. All in trunk 39" x 22" x 101/2" 25.00 Mounted on the baseboard is a cylin- TS /182 UP Navy Scope An exceptional buy. Complete with der adapted to receive a pump piston tubes and set of spare parts includ- which slides horizontally therein. The ing transformer, choke. 2 extra cathodes and 22 other tubes 60.00 piston has a rod which projects through .05 Mfd. 16000 V Sprague Vitamin "Q" a cover in the cylinder. A spring tends oil condensers 3.00 to force the forward so that .5 mfd. 6000 V. GE Pyranol 5.00 piston the 10 mfd. 1000 V. GE Pyranol 2.75 upper end of the piston rod strikes Aerovox Oil Condensers, 1 mfd., 1000 against the stem of the switch and volts .95 Signal Corps High -grade Telegraph Key .89 closes the circuit. Normally the spring High Grade Transmitting Key .89 holds the switch closed by pressing on $12.60 G.E. Pyranol, 10 mfd., 600 V the stem of the switch through the FRONT VIEW SIDE VIEW Cond. 1.50 pis- G.E. Pyranol, 4 mfd., 600 V. Cond .95 ton and the piston rod. Working diagram of the apparatus which is Shure Crystal Pickup 2.75 A regulating valve is provided at the claimed to be radio's greatest improvement. 1 mfd. 600 V. Aerovox Oil- Filled Bath- tubs .25 $60.00 Aerovox 1 mfd. 10.000 V. Oil Cond. 9.95

LEEDS RADIO CO. 75 Vesey Street COrtlandt 7 -2612 New York City 7

A FREE BOOK Develop your personal, creative power! Awaken the silent, sleeping forces in your own conscious. u Become Master of your own life. Posit aside all obstacles with a new energy you have overlooked. The Rosicrucians know how, and will help you apply the greatest of all powers in

man's control. Create health and abundance for - yourself. Write for Free book, "The Mastery of Lie." It tells how you may receive these teach- ings for study and use. It means the dawn of a new day for you. , . Address: Scribe .11.8.V. The ROSICRUCIANS SAN JOSE (AMORC) CALIFORNIA Leff -The inventor shows how the eliminator operates. Right -Inside view of the device. 580 RADIO -CRAFT for MAY, 1946 piston is forced downward, the air is forced outward through the valve and around the sides of the piston. When SPEED UP REPAIRS WITH THESE G-t AIDS the button is released, the spring forces the piston back. This motion creates a G -C Way! vacuum below the piston which resists Handle Dial Belt Replacements the Easy further movement until sufficient air en- ters the cylinder through the valve and partially balances the pressure on both r. sides of the piston. The piston rod con- BA tinues its travel until the upper end AP closes the switch after an interval of, say, 45 seconds after the button is pressed by the listener. The listener may '.rdon't 4, Order belt by c Better still - DY using G -C 3 If you S. have a cum regulate the length of the interval by ( 2 Lnnw m (romrte ...C.-7, III 1 Guide- fiels b e l l r \D c t ourum1,rrr: lin a esaYa ntmlc use distrd.utor.Phone. x 1,-lia eu v lust cheek "'de' the orr- Belts a Indexed adjusting the valve. He can, without ad- number of the sc r In permanent algal L nnnleic Ìi Ré cor a der r'a io , e to Jctern.Inc Gee.IC o rapt service- box with slide'. justing the valve, regulate the length placement (urine Dc lt, ins11ru'c uns t drawer. n d Measuring rcct G -C su belt. no waiting. of the interval by varying the distance scale. mua page G -C No. 345 Belt Guide he pushes the button down, being guid- TO ALL RADIO SERVICEMEN -68 FREE Scale. Ask for them at your Radio ed by the calibrations on the scale. The and Service Book and Measuring listener can turn off the set permanent- Parts Distributor. ly by placing the finger button within -Strong- Correct Fit" G -C Dial Belts the niche on the slot. Get "Smooth The apparatus is small and portable. from Your Radio Parts Distributor By using wires of sufficient length, the apparatus may be placed by the listener in any convenient location without mov- GENERAL CEMENT MFG' CO. ing the receiver, or the apparatus may be made an integral part of the radio ROCKFORD, ILLINOIS, receiver. The device is connected to the radio by means of a "series" plug fixed to the terminals of the wires leading to the MINIATURE, EXTRA - SENSITIVE HEADPHONES! commercial eliminator. This series plug fits into the electric wall outlet near the IDEAL FOR radio. The plug from the radio is then Amateurs,Servicemen,Com m e rc is l Operators,etc. fitted into the series plug. Thus the cur- Manufactured especially for Infantry and Armored Forces; rent to the radio is controlled through cost the Government approx. $35.00 per headset. Extremely the switch in the eliminator. When the sensitive phones, with good fidelity characteristics, with matching transformer built -in so that phones work into any eliminator is not operated the current is hi- impedance output and at the same time are protected controlled by the switch on the radio it- from any DC component. Practically indestructible. Light self as in normal operation. and Compact! Features: adjustable headband; flexible rubber phone cord to provide many years of wear and to guard against moisture; rubber spring clip for fastening to clothing; soft, flexible rubber ear -tips fastened to each RADIO- ELECTRONIC QUIZ phone for comfort and to remove ex- pRICE, 595 How thoroughly have you mastered traneous noises, etc. Supplied with COMPLETE the contents of this magazine? Try the standard phone plug. following quiz as a test: Send check or money order for postpaid delivery. I. How might the range of one televi- Dealer and distributor inquiries invited on quantity. sion station be extended to cover half TAYBERN EQUIPMENT COMPANY the earth? (See page 530.) 120 Greenwich St. New York 6, 2. What does "Block" and "Ring" N. Y. mean to television? (See page 5314 3. What is a "Vectorscope "? (See page 533.) NEWT ÄDDÌTÖ2: MORE SMASH BUYS 4. What would be necessary fo attain at Slips In your pocket or purse - absolute linearity in a vacuum -tube ÉLADYelTO3PLAY! as shown National Radio Distributors voltmeter? (See page 535.) u-e. Personal Smn000thphonerable black and silver plastic case. Kaa 5. How many sets of computations are patented Fixed Crystal NO IMMEDIATE DELIVERY RIeES. BATTERIES required for a five- antenna array? PLUG REQUIRED. USUALLY RECEIVES LOCAL (See page 536.) BROADCASTS without HERE'S VALUE! wire. 6. How is the frequency of an FM GUARANTEED TO WORK when 3 tube AC -DC Phono Ampli- connected and Used according to fier. completely transmifterstabilized? (See instructions with each assembled and page 537.) used Inin e..e ready to operate. Uses 12Sa7, 7. hotels, cabins. bed. after hours. etc. 50L6 and 3525 tubes. Size: Of what use is a frequency -modu- 5'/a' x 3V' x I%0. Price each SEND ONLY $1.00 Pay postman $ 99. hm ó env- net lated signal generator when servicing err fees on arrival or send 53.99 for postpaid $4.75 less tubes. In lots IDEAL GIFT CHILDREN OR ADULTS ALIKE! of IO each $4.45. an AM receiver? (See page 540.) KETTE RADIO TODAY -NOW. Dealers in most cities. A GREAT BUY- INSULATED RESISTOR KIT 8. Contins 100 type What are the three main ap- PA -KETTE RADIO COMPANY Iced Insulated tesist resistors. Approximatelyy 600 DEPT. RC S KEARNEY. NEBRASKA Popular Gold Band. Each 52.69. In loto proaches fo radio receiver servicing? asi S, Some EXTRA SPECIAL! -RY -PASS CONDENSER KIT (See page 543.) Consists of 100 Tubulars (all 600 Volt) in the following sizes: 001. .002. .006. .01. 02. 03, 9. Can you name a reflector which .05, e .1 Mfd. All Fresh Stock. and fully guar- If anteed. Per Kit. 55.95. contains no solid material, yet can be RADIO KITAAmico "QUALITY ABOVE ALL tubes, S Speaker. and full Instruction% used to swing the beam of a radar Each 510,93 Dy- or radio transmitter? (See page 562.) !x namic Speaker, and full Instrructionns. Each, 517,95. )40'. Please include at least 25,1/4 with C.O.D. orders, 10. Has a device ever been made »..L.:5-11:g.. Write for New Free Gataleo. Just Out, which will cope successfully with the .nit\ ar. , "plug -ugly" radio commercial? (See National Radio Distributors page 580.) CAPACITORS SOLAR CAPACITOR SALES CORP. New N.Y. 285 MADISON AVE. NEW YORK 17, N. Y. 10298 E.163 St., York 59,

RADIO -CRAFT for MAY, 1946 581 CHECK THESE PRICES! Available Radio- Electronic Literature HERE ARE JUST A FEW OF OUR SENSATIONAL VALUES ON OUR LARGE STOCK OF STANDARD Manufacturers' bulletins, catalogs and periodicals. FIRST -QUALITY MERCHANDISE. SEND FOR OUR LATEST PRICE LIST. A NEW SERVICE FOR RADIO -CRAFT READERS: In order to save Almost MI types of tubes in stock. Mall in your your time, postage and incidental work in writing a number of letters to orders for all types needed. not lust the critical num- various bulletins offered, proceed bers. and well try to fill your orders completely! different manufacturers to secure the as follows: TANK TRANSMITTER owners! Trade In your 12 -volt letterhead (do not use postcards) ask us to send you the litera- dynamotor for a 110V AC operated power supply On your For $29.95 and your dynamotor, we will supply a com- ture which you designate. It is only necessary to give us the numbers. We plete kit of parts and instructions to construct a power request directly to the manufacturers, who in turn supply operating from 110 V AC. for your B -19. will then send your Mark Il Radio. Complete SCHEMATIC DIAGRAM will send their bulletins or other literature directly to you. and CIRCUIT DESCRIPTION for B -19's. along with instructions to convert to AC operation-$5.00. TUBULAR CONDENSERS. Guaranteed one year. Prices in lots of ten. either one type or assorted. 210 MANUAL FOR ELECTRONIC ed in the Dongan line are transformers 100 Mf, 25V-35e; 50 Mt. 150V -45c: 20 -30 Mf. - 150V-90c: 20 -20 Mf, 150V -30c; 25 kit. 25V -20e: DEMONSTRATION for oil burners, fluorescent tubes, neon 20 Mf, 150V -20e; 10 Mf. 50V -15e. PAPER CON- to in- DENSERS 1000V teat; 600 WV, .25 Mf-20e:.1 MI An interesting manual of laboratory signs and motor control.- Gratis -10e; .05 off -Oc; .02 51f- 8c:.01 bff-- Oc:.008 51í- terested parties 5c; .005 Mf and smaller -7c. MICA CONDENSERS. experiments, printed by Radiolab Pub- 1000V teat: 600 WV. any standard capacity -15r. A 60 -page MOTOR STARTING CONDENSERS. 110V. 85 -115 lishing and Supply Company. Mrd, 3- second start, universal type for refrigerators, of nine chapters, illustrating 217- DIATHERMY TUBES pumps. etc. -$1.25. booklet i methods of performing 15 experiments Taylor Tubes, Inc., has issued a fold- PLASTIC LONG -NOSE PLIERS -Will stand 300° er cross -indexing the various types of heat and are Insulated to 6000V. Just the tool for or demonstrations of electronic prin- radio servicing-89c. AMPLIFIER FOUNDATION diathermy machines and the tubes that UNIT 7z17z9", chassis is 3" high. Finished in beau- ciples. The demonstration begins with tiful gray ripple finish- 92.T0. We have a complete are used. This is of interest to manufac- stock of ICA chassis and cabinets at comparably low the flow of electrons and conclude with prices. G.E. MICROSWITCHES. S.I'.D.T. -50r. turers and users of diathermy equip- FILTER CHOKES- Stromberg- Carlson. 30 11y.250 receiver testing and alignment. Ma, 35 Ohms DC Res. Fully shielded in black ment.-Gratis crackle case -$1.98. This manual is of particular interest The RADIO CHEMICAL KIT-in leather case--contains to science and physics teachers. 218 VIBRATOR GUIDE one bottle each of cabinet stain. dial -drive "no-slip," may be al- - enact cleaner, lubricating oil, cabinet polish, and demonstrations described The Mallory Replacement Vibrator service cement -'BAs useful as a screwdriver to the fit the needs of the class or serviceman " -$1.34 per kit. SI'AGIiErr1 -in as- tered to Guide is issued by P. R. Mallory & sorted colors -Rrst Quality -x911 fit insulated wire up the equipment on hand. Presented upon to a10 ales -25 ft. for 25e. METER RECTIFIERS- Company. It is a complete listing of full ware, four -wire type-99e ea. purchase of servicing equipment but radio equipment using vibrator type ALL PURPOSE NEON TESTERS. 60 to 550 volt. be separately for $2.00. Indicate all kinds of current. AC. DC or RE. and may purchased power supplies and gives the number comes complete with instruction booklet outlining various tests on radio sets, including the location of of the vibrator used as a replacement. fading, dead stages, shorts, and making screen -grid 211- INSTRUMENT CATALOG and plate circuit tests. 25c ea. Per dos. ou attractive 24 -page catalog Of interest to servicemen and radio display card -$3.50. Electro -Tech issues a supply retailers.- Gratis AUTOMOBILE ANTENNAS - Standard 3 section of servicing and industrial equipment. type, complete with lead- in -66 "-51.50; 96"- $2.95. catalog is well illustrated and lists RESISTOR KITS-50 assorted. all useful 2 Watt The 219 -SOUND ACCESSORIES sise -- $1.95. ROTARY SWITCIIES-SPDT shorting line of equipment. -Gratia type -15e. Ceramic switches for hifrequency use-3 a standard Atlas Sound Corporation has issued pole double throw or 4 pole double throw ishorting type) either one -95c. "INSIDE THE VACUUM a catalog, F -41 that lists many pieces TUBE," by Rider -a valuable addition to your tech- 212-STUPAKOFF CATALOG nical library- 54.50. of sound accessories. This illustrated Stupakoff Ceramic Manufacturing lists CARBON MIKES: "Bone Broadcast" type. com- issues an illustrated bulle- catalog speakers, baffles, enclos- plete with instructions to attach to any radio- hoc. Company ures, microphone stands, similar Gold- Plated single- button midget type signal corps ceramic prod- and mike, with stretched duraluminum diaphragm -.rust tin showing the various apparatus. -Gratis the mike for concealed or secret pickups. lapel mikes. These products in- or for attaching to any radio-95c ea. 81HUIRE. Model ucts manufactured. T -1T, single- button. Features high -quality reproduc- clude antenna spreads, coil forms and tion, built-in switch. 5 -ft. cattle with plug, and 220 -CERAMIC CAPACITORS moistureproof cover. Packed in sealed cartons -$2.75. insulators. They are also manufacturers Bullet CRYSTAL mikes. $5.45; Bullet DYNAMIC The Electrical Reactance Corpora- mikes -$7.95. of metal -glass hermetic seals.- Gratis tion has issued two pamphlets describ- RECORD CHANGERS-110V. 60 er. with crystal pickup. This two -post changer will play twelve 10 ing two new types of ceramic condens- or 12 inch records INTERMIXED! -the only changer 213- PRECISION SWITCHES ers that they have developed. These on the market with this feature, in this price range. Mu Specially priced at $22.50. A switch manual by the Switch condensers have solid silver electrodes. Corporation. This manual is well illus- Type CN has parallel leads and type trated with photographs and working CI has axial leads.- Gratis drawings. The performance of the vari- BUFFALO RADIO SUPPLY ous types of switches is given in the 221- COMMERCIAL TRANSMITTER 219 -221 Genesee St., Dept. 5C form of tables and graphs. -Gratis to A four-page pamphlet has been issued Buffalo 3, N. Y. interested parties by Aireon. It illustrates a 50 -watt complete ground station for airline and oth- 214 -THE AMAZING ELECTRON er commercial applications requiring Do you need A 33 -page booklet published by the low -power transmitters. -Gratis r Electronic Corporation of America. It BINDING POSTS? is illustrated in cartoons and drawings 222 -ALNICO MAGNETS The XL PUSH POST with its Suring - Action assures Constant Contact and some of quick connection. and explains to the layman, An eight -page pamphlet issued by Ar- Manufactured io All Aluminum Type as the miracles of modern electronics. Not nold Engineering t 12cv each. Company. It gives en- Aluminum Body. $aksllBakelite Top Type al a book for engineers but written pri- gineering data on Alnico permanent at ESc each. P, ALL BRASS-STAIN- marily for the public at large.- Gratis magnets in the form of tables and , LESS STEEL SPRING A PIS- PROVEN by R IV SALT SPRAY TEST - NON- graphs. Of interest to manufacturers. CORROOCORROSIVE at 28e sash.each. - Manufacturers and Realaa Liberal 215 -ALTEC SPEAKERS Gratis X. L. RADIO LABORATORIES An illustrated pamphlet on high -fi- 420 West Chimp. Ave., Chicago IO. III. delity speakers, issued by The Altec 223 -CAPACITOR REFERENCE - Lansing Corporation. Complete with GUIDE /te frequency response curves from zero The Magnavox Company issues a 20- ed r to sixteen thousand cycles.- Gratis page reference manual on electrolytic Largest Manufacturer of condensers. Illustrated, with each type Apparatus Wireless Telegraphic 216 -INDUSTRIAL TRANSFORMERS of condenser described with working CO ICE Equ1YEer An illustrated catalog of industrial drawings. This manual is particularly McElroy Manufacturing Corp. transformers is issued by Dongan Elec- interesting to manufacturers and dis- 82 Ireskllae beige Bastes, Massackesetts tric Manufacturing Company. Includ- tributors.- Gratis

582 RADIO -CRAFT for MAY, 1946 ri i i %i PPS'% jG, PIP aG /,i jG/i,i, , "TAB" oi 2 SPECIAL BUY (Limited Quantity) . SERVICEMEN'S CORRESPONDENCE -AN EXAMPLE Crystal Diode Sylvania 1N21 SII. C. three for $1.00 Crystal Diode holder cartridge type three for 1.00 Eimae or H.R. VTI27A & connectors, new Govt. I. 4.95 G.E. Neon '/4 W. NEI6 /991 (LP 42c) four for 1.00 RCA 6AC7 -1852 new govt. insp. (LP.SI.75) .65 Cathode Ray Tube new gvt. Insp. 5API (LPS20) 9.95 The editor of Radio Craft but I think it is high time that some of Cathode Ray Tube new gvt. insp. 5BPI (LPS20)) 9.95

Cathode Ray Tube new get. Insp. 5BP4 (LP527) 9.95 ' I have read the editorial in the No- you and your kind got wise to who Rectifier 872 new get. insp. (LP57.50) 4.50 vember issue as well as the comment in made it possible for you to stay in busi- Circuit Breaker Heineman 3 or 20 amp 110V .97 Circuit Breaker Heineman .OlOamp 2300V. DC .97 the February issue by Mr. Rubane, on ness and preserved your freedom so G.E. Switehette CRI070C103F3 DPNOC five for 1.00 Micro- Switch leaf type IOA. 125V. SPNO 3 for 1.25 the subject of a good typewriter and a you could live your own life. This Relay Sigma Sens. 5AH 200 ohm 3.5ma SPDT 2.25 Relay W.E. sens. 3500 ohm SPDT 5A contacts .97 neat letterhead. I ask you now, what would have been a hell of a place to Relay 105 Ward L. 115V 60cy SPDT 20A cis 1.90 is wrong with the paper that I write this live if Hitler or the Japs had have Micro wave ant. with coaxial enter & mtg. briet. .95 FM Television Rotatable UHF Coupler 3.98 I on, and what is wrong with the whole gained control of our country and YOU, CoAxial 52 &72 ohm RG8 &11 U cable 10010. for 12.00 Lacing Cord Mildew Resistant #6 treated lb. 1.90 .thing? I'll tell you. According to your Mr. Editor, Know it. Now, let's see you Thermostat operates 85 deg F. 15amp three for 1.00 way the does not get busy and help some of the fellows G.E. DW44 R.F. Thermomtr 0-IA. 2'/;" B' ease 3.95 of thinking, paper G.E. DW52 R.F. Thermomtr 0 -5A. 2Ya" B' ease 3.50 have the neat letterhead which you pre- that helped you. AC Voltmeter NA33 Wstghse. 15OV60ey 21/s"B'o 2.95 r DC Voltmtr 2000V. prec.mult. 1000 /V.21/2"B'e 8.95 scribe and I do not happen to have the JACK R. MASSEY. DC Voltmtr 4000V. pree.mult. 1000 /V.3"B's 10.95 DC Voltmtr 10,000V. pree.mult. 1000 /V.3 "B'e 12.95 nice new typewriter recomended per - Resistor precis. N.I. Sprague 10 mee (LPS90) 3.00 (Perhaps it would have been better sonaly by you, and I also know that RES. precis. N.I. W.E. Hermeticly sealed 1qó had we reproduced Mr. Massey's letter 1000, 5000. 10000. 30000 each 25e. 80000 ohm .45 the form is not as good as it should be. 100000. 200000 ohm each 55e. 500000 ohm .65 photographically. Unfortunately, this Resistors 100 asst %s & I W BT 50 to 2 mee 2.50 You see, this is Sunday and my secre- Hammarlund socket 900% would have taken over in Radio - UHS Acorn (LP61.501 .30 tary does not work today so I have to a page Amphenol high V. safety socket 77A4T Two for .75 Craft, and our readers appreciate that Johnson :247 socket for 829 tube steatite Ins. .85 do all this alone. Socket octal amphenol 78- 58T -HF ins. 25 for 1.49 this would not have served any pur- Johnson 50 w. socket hvy duty type H.F. Steatite .85 I am one of the fellows that was Johnson miniature 277 B socket & shield HF Ins .29 pose. Instead, we reproduce the letter, Devon S.C. switch 13 cis. H. F. ins. 25 amp eta. .49 forced to sell out when my draft board complete, Radio Noise Filter Mallory NFI.7 oil cond .49 with its faulty English, and Transformer 6400V.C.T.y A Kenyon 115V6Ocy 18.00 called and since I have returned I have its bad spelling, exactly as it was re- SI Min. orders FOB. N.Y.C. Add Postage all orders and 25% deposit. WHitehall 3 -3557. Send for catalog found the same trouble as the two other ceived. 300. Don't wait. rush orders as quantities are limited. fellows who have writen to you. Mr. Choke G.E. Wheeler 4 hy. V5A. 30 ohm wt. 2.95 Mr. Massey speaks of a "letter- New Vacuum Tube Voltmeter S.C. 1107 F 29.70 Rubane hit the nail on the head when Condenser GE IMFD- 1000V. a) 60e, ten for 5.00 head." The letter was written on an ex- Condenser GE pyranol 3MFD 330V AC I000VDC .95 he said that the veterans are the poor cellent bond Condenser Solar 25MMF 10000 V. RF (LPS21) .35 paper-two blank sheets New Bendix autosyn gvt. Insp. 110V60cy pair 18.00 slobs that went out to win the war while of paper-but not a printed Aircraft ouncer Impd. Jefferson 100 Hy 3100 ohms .69 letterhead. Ohmite 25 w. 250 or 350 ohm (LPS4) 1.45 the Draft DODGERS stayed home and The only good thing about the letter Millen 36001 ceramic plate cap 9/16 & %" 8 for .90 ate up the post -war gravey. I had a is the paper. It is as if Mr. Massey had "TAB," Dept. RCS good business before the war and now 6A Church Street, New York 6, N. Y. put on his best suit -minus the pants Our Central Location what do I come home to. Well, that is -and called on a radio manufacturer. not my wory because I am making a Everything we said editorially in our ELECTRICIANS! living. The thing I don't like about this November issue was violated in this RADIO MEN! thing is that we are not given the chance letter. For instance, the typewriter was Earn More Monev! that we should have. We could not so battered that the letter "a" is out help it if we were away from home of alignment, making it most difficult while all the post -war planning and to read the letter. For $5.00 the type- agencies were being given out. All writer could be put into shape so that we were doing was the fighting so the recipient of a letter would at least those big shots who got the agencies be able to read it without irritation. could use them. Now that we have won We repeated verbatim what we said these rights for the plutocrats, they tell in our November issue, to wit: us to go jump in the lake. I would have "If we an cannot typewrite our- outlet for some good equipment if selves, we would get somebody in the Manufacturers and Distributors our community would to do the work for have saved a spot for the proper us, because if we have a beautiful L. Distribution in place of thinking of the letterhead, yet have our letters Yoa, / /DDoysErij extra dollar he might get by handing Needed by was workers. maintenance typed by an amateur, this is worse men. beginners, old timen) Nothing it to the highest bidder. I say, Mr. Ed- than not having OVER elselike lt. Saves time. helps boost you, itor, a letterhead at all." pay... 4 GREAT BOOKS IN 074E1 it is time for you to change your To put it in another way, you can 1. New Step-byStep Trouble Shooting r mind and 500 Course. 2. SUO Shop Printe 3. Else.- get behind the veteran and "hire" English the same as any other Large Size Radio Dictionary. 4. Spare Time Jobs. push. (I don't mean over the cliff like Electrical yr. Technical Counsel by commodity. A good high -school girl FREE!Imail from COYNE staff, on you have done in the past) would be glad to write and Radio trouble -shooting problems, letters for a Shop Prints SEND NO MONEY! See offer below. A man in your standing should have small sum per letter and would -How to read Satisfaction guaranteed by famous actually COYNE Les rn -by- Doing" Elec. sence enough to know where his bread be gaining experience helpful to her in a and use them trical School. Rush coupon novel and butter comes from. You wouldn't business course. There is no more C. 50.K1 jus- u o ELËCTR CAL SSeN6L. FREE TRIAL? have your nice cozy home and a nice tification ' 1 600 a. Poulina St.. Chicago 12, N. COUPON 1 for poor composition or Eng- klm g polished desk in your we, B tráÌdsadgr.'+rouble Sh oting Manual.Withi IO darys after office if the lish than for poor paper. ll Renia t 1951 either cetera It or seed 6d, Nee ta > anal total 1 É9.961, paid, end tuf sere ovor 10 veterans, had have laid down our arms Mr. Massey does not seem to have 1 Same 10.da> tree trie{ d return DrMlesa.privilege. on the battle field and said, we are going learned I NAME__ that in this world we must con- I ADDRESS-___ home and get some of those post -war form to many things. When he was in I,:aTme W one.- .STATE. ideas before the plutocrats get them. the Army he was taught a rigorous -J We wouldn't have got them ether be- routine, particularly that of order and BUILD YOUR OM/NF-1.1:; - cause the Japs and Germans would have neatness. His buttons had to be shined; FAST FREEZER 'Ile .J got here ahead of us. Why don't you so had his It's easy to build this household nppll- - - shoes. Appearance counted ance and profitable to use. Save uo to and some of the other big boys in your for a lot. Yet, in the civilian 75 %. Operateson 110 or 32 volts. clans world, show 5 sizes and are easy to follow. line help us to get some of the bet- where exactly parallel conditions pre- ENJOY MAKING ONE OF these freezers from new or used Darts. Noes- // 5 slier ter deals that are available at this vail, our correspondent wants to have Ma 40 Cu.tl time? Check for (comecomplete plans and catalog r I don't like to wave the flag (Continued on following page) LE JAY MF... CO., 456 Wry Bldg., Minneapolis 1, Mies.

RADIO -CRAFT for MAY, I 946 583 COMMUNICATIONS (Continued from previous page) SPECIALWI Introductory Offer everything his own way instead of try- Radio manufacturers - particularly 10c per Pack, 12 for $1.00 Postpaid ing to conform with custom and usage. new ones-will be hard put during the RADIO HARDWARE Radio -Craft is happy to note that Mr. next few years to get the right kind of Machine Screws Massey is making a living, but he cer- distribution. They cannot get too many Cat. Quan- Cat. Quan- tainly could double or triple it, if he good outlets. If you talk to radio man- No. Size City No. Size tity we have, you learn that 501 4 -36 x 1/4 6 508 8 -32 x% 12 would conform to present day business ufacturers, as 502 4 -36 x 1/2 6 509 8.32 x 1/2 12 rules, which unfortunately he seems to they have an insufficiency of deserving 503 4-36 x1'/4 3 510 8 -32 x% I I would much rather have 504 6 -32 x 5 511 8.32 x I 7 have no inclination to do. outlets. They f 4 505 6.32 x /2 4 512 10 -32 x 1/2 10 one "God helps them that help them- ten accounts in a community than 506 6 -32 x 7A 2 513 10 -32 x /. 8 or two. 507 6 -32 x 1 8 514 10.32 x 1 6 selves." An old and true saying, which Self Tapp ng Screws is particularly apt today. Unfortunately, the one or two outlets 515 45i /2 8 518 8xy/ 7 in which they have 516 6x1/4 8 519 10 7 are the only ones e We positive Mr. Massey 517 6x /9 8 520 10x% 6 are that - confidence; the others fall by the way- Metal Washers as well as other ex- servicemen -can get side because they "do not play ball" in 521 For No. 6 25 523 For No, 10 25 and 522 For No. 8 25 outlets from radio manufacturers a business sense. Hexagon Nuts distributors IF ONLY HE WILL Radio- Craft, we believe, is the only 524 4-36 x 1/4 16 526 8-32x5/16 14 THEM THAT HE IS DE- 525 6 -32 x 5/16 15 527 10-32 z 3/e 8 SHOW radio magazine that has gone to the Lockwashers SERVING. Rest assured that we speak trourle of showing ex- servicemen what 528 For No. 6 15 530 For No. 10 15 when we say with em- 529 For No. 8 15 531 For %" 8 authoritatively course to pursue to get ahead, so they Assortments phasis that deserving ex- servicemen are may take their righteous place in the 532 Wood Sc ews 10 533 Grommet 4 going places these days. radio industry. Unfortunately, there 534 Cable Clamps 6 BEEN SUCH are still some who cannot see the light. 535...... Dial Springs 2 THERE HAS NEVER 536 Spade Bolts 7 A SHORTAGE OF GOOD OUTLETS To quote the old proverb: You can 537 Set Screws 5 FOR RADIO MANUFACTURERS lead a horse to the water, but you can- 538 Fibre Washers 15 539 Soldering Lugs 15 AS THERE IS AT PRESENT. not make him drink. Editor) 540 Rivets IS 541 Mounting Nuts 4 542 Grid Caps 4 "RADIO- CRAFT" IN OCCUPIED TERRITORY We Can Supply All Types of Radio Hardware WRITE FOR OUR COMPLETE CATALOGS Dear Editor: ing. Telephone receivers were rewound DEALERS I Write for complete I feel I must write and thank you with wire taken from audio transform- JOBBERS f catalogs and discounts for Radio -Craft. ers to increase the resistance. TRUTONE PRODUCTS CO. Early in the German occupation of Reception was very good from the 303 W. 42nd St., New York 18, N. Y. Guernsey I was lucky enough to come A.E.F. transmitter in England about across a few copies of your magazine, 100 miles away; in some instances at which I regret I had never before loud speaker strength; hardly believ- ATTENTION! , f - known. I soon remedied that after the able, but proved many times. Introducing Our .. war. Now I receive my issue every First Post -War EY Your magazine was one of my best month, though usually three months MULTI -TESTER t friends during those five years. I read, late. re -read, and then read them again; the KIT H banned As you are aware, radio was articles always seeming to bring out Ideal for Use By by the Germans and all work had to Students Schools i some point I had not noticed before. I Hospitals Ama- ' O be done under very difficult conditions, leurs regret that some of the articles in re- and Service- various means we still listened men. but by cent issues are rather too technical 5 voltage ranges, 3 to the news. We finished up with crystal current ranges, S for me at present, but I hope to catch 1 all sorts ohm ranges. ^' receivers, making them from up soon. Volt Ranges: 0.5- - of materials; the crystals from a mix- 50 -150- 500.1500 volts. Current Ranges: 0- 50- 150.500 H. CAPPER, Ma. Ohm Ranges: 0 -2 00- 20.000- 200.000 ohms. ture of lead and sulphur or galena Model 120 (Illustrated) crystallized in a pipe cap after heat- Guernsey, Channel Islands. Complete Kit Cal $a959e7 .7 In addition our previous models of meters and Radio K Its are still available. A FEW COMPLIMENTS AND CRITICISMS Cade Kit model S -5. complete with tubes @ $19.95 the old tubes can do. Ca[io Kit model TRF -4A, less cabinet @ 10.95 Dear Editor: lot that Radio Kit model S -6. less cabinet @ 17.95 I have quietly said nothing and re- How about articles on complete me- 250' Deposit on C.O.D. Orders. Write for Free Catalog. We c rry a complete stock of parts. ceived each issue of Radio -Craft in the dium -power transmitters for the ultra- a Export `inquiries Invited. mail without voicing my opinions of high amateurobands? How about a series RADIO KITS COMPANY your magazine. As with all magazines, on test equipment that can be built by M 120 Cedar St. New York Dept. 6. N. Y. there are good points and bad points. the home radioman and used in the radio Human nature demands that your read- shack? Why not advertise for writers? I don't want you to think that I am a HAZELTON INSTRUMENT CO. ers tell you only the bad points about your publication and none of the good. "know -it- all." Why not ask your read- Electric Meter Laboratory Your January issue and the February ers what they want. Print some of my Electrical instruments, Tube Checkers, issue look promising with those articles letter in your "Communications" col- and Analyzers repaired. written by your Editorial Associate umn and ask for comments. If the old 140 Liberty St., New York, N.Y. Mr. I. Queen. Don't lose him! And let's Short Wave Craft readers have fallen Tel. BArclay 7 -4239 have more like him! Your features such back on Radio -Craft for radio reading - as "Radio- Electronic Circuits," "Try you'll hear from them. I remain, a ra- 1 This One," and "The Question Box" are dioman who cries for the good old days. very good. Keep them going! SHERIDAN B. LAPORTE RABIREE' How about a feature called "Experi- Worcester, Mass. menting on the Ultra -High Frequen- (Mr. LaPorte will doubtless be WHOLESALE RADIO__ cies?" Use circuits that the home radio- pleased to see in this issue the first of 2608 Ross Ave. man, experimenter, and amateur radio a series of practical constructional arti- operators can use. Leave out this stuff cles on high- frequency transmitters and DALLAS 1 TEXAS about magnetrons, etc. There is still a receivers by I. Queen. Editor)

584 RADIO -CRAFT for MAY, I 9 4 6 A U.H.F. HAM TRANSCEIVER There's a new kind of (Continued from page 545) AMPLIFIER to feel the effects of the u.h.f. These time of purchase and we can only hope can be shown by the following table: for the best. It happened in this case a- coming! that one was slightly better than the and A.C. Shaney PLATE LOW FREQ HIGH FREQ other as an oscillator on the high fre- - VOLTAGE I Ig Ip Ig quencies. There is no apparent differ is "a- fíxin' to build it" en e in efficiency in the audio stage. I0 0V .25 ma 490 yA 2.Sma IIO uA at Amplifier Co. of America MICROPHONE CIRCUIT 220V LS 850 4.0 250' Technicians want The circuit is a better kind of amplifier conventional among and they are going to get it! For there Effect of frequency change on I and I. transceivers. We used a Stancor A -4413 is an amplifier in the making at Amplifier microphone and audio transformer. This Co. of America today, that promises to revo- These unloaded circuit values show the is the largest component in the unit, higher efficiency obtained the lower lutionize the industry's thinking about the at but its cost is reasonable and it elim- amplifier of the future. It is cleverly designed, end of the range. inated time and effort that would be beautifully constructed and most amazing in For greater output it may be desir- spent in adding windings to a straight its performance. Its fundamental design is able to work on the lower portion of audio transformer, as is sometimes done. one of the truly exciting secrets of o.ir time. the amateur band (even when the re- Since the purchased unit matches a New circuits, new materials, and new proc- mainder opens up) if conditions per- esses combine in this amplifier to achieve a 200-ohm microphone and a 10,000 -ohm triumph mit. Our tuning arrangement is ideal in plate to a single grid input the ampli- of modern engineering. this respect since it permits very good fier gives very good results. The out- It may not be the first amplifier off the line, spreading in but it may well be the first band this region. More put is ample to run a 2- or 3 -inch PM completely new than a fourth of the dial rotation covers speaker and with phones one. And amplifier men know that A. C. the signals are Shaney and his associates at Amplifier Co. the present third of the amateur band. really Ioud! The primary of the speak- The of America have what it takes to build the antenna consists of a % -inch er transformer (or headphones) acts kind of an amplifier that engineers, techni- aluminum tube about 5 inches long with- as the modulation choke. cians and music lovers are waiting for. in which a 3/16 -inch piece of tubing A carbon mike with two pen -light why so slides. This means that the total length cells is found to give sufficient modula- That's many thousands to- can be extended to almost 10 inches. A tion. There is plenty of room to add an- day are "watching the news" from quarter wave -length is about 6% inches other should the output of any particu- at 425 me but the antenna should be lar mike be found to be low, but 3 AMPLIFIER CO experimented with for best results at volts is ample here. The mike jack is o AMERICA any frequency. Coupling is provided by designed to short out the microphone a half-turn of No. 16 wire. If a rela- winding when the unit is used as a re- 398 BROADWAY, NEW YORK 13, N. Y tively great distance is to be covered ceiver with no mike plugged in. Other- is A postal card will put you on our mail- it recommended that another quar- wise there is a terrific hum due to the ing list to be among the first to know. ter wave -length be added on the other open winding. Plugging in puts the bat- side of the loop, making a dipole. Better tery in series with the winding. If the yet, an array of directional radiators mike has a "press-to- talk" switch it (the 18 YEARS IN RADIO should greatly increase the range in any mike) need not be removed even when given direction, but on the other hand, a long period of transmission is sched- GET THIS will take the transceiver a little out of uled. The circuit appears in Fig. 1. the portable and convenient -to- handle We don't find it necessary to include Teat CATALOG category. another switch to open the speaker sec- By This Old Firm A phone tip one end of at the anten- ondary in order to avoid feedback to the Latest developments in na (held by means of a screw through mike. If the two are separated by a few radio and electronic the tubing) fits into a tip jack and feet and if they don't face each other ports and devices, new- makes the radiator removable when the this will not cause trouble. If necessary, est horn gear, gadgets is for experimenters, bar. transceiver not in use or being car- however, the switch may be placed right wins in war surplus ried about. on the speaker and need only be a single - items. pole single -throw type. AUDIO SECTION FREE The choice of modulator (and audio POWER SUPPLY TO amplifier) also fell upon the 955 tube, It was found desirable to design YOU C a Mail the coupon be- but for different reasons. Here we were small power supply which would deliver low and get this concerned with size and power require- sufficient voltage to run the transceiv- new catalog FREE. ments, as well as the fact that two tubes er during the tests. The size of power of the same type make for simple test - transformer we would have liked to use r ing of tubes and permits putting the and those available didn't coincide, so BURSTEIN. APPLEBEE CO., I best one in the oscillator section. These we went over to the voltage- doubler 1012 McGee, Kansas City 6, Mo. tubes are not generally tested at the a.c: operated idea. A 117Z6 -GT tube Send me FREE catalog advertised In (which now seems Radio Craft I AM ANTENNA generally a v a i t- 955 able) is used in the STATE CONNECTION IN INDUSTRY Óóe` SPR TRANS NAME OR PHONES supply. 12T 1/4' 955 Relatively small ADDRESS 00005 o-+ R condensers are used TOWN STATE_ across the tube ele- 12T ° '5MEG° 1/8" ments and a large .00005 --LL (capacitance) val- o I .IST 25 ,002' ue across the d.c. I7T VB ATTENTION Ve" i output. This eliminates some of the Radio Servicemen and Appliance Dealers Send for our latest catalogue sheets. disadvantages o f Many hard -to-get items. 3V high capacitance 8+ (Continued on John A. Cox Radio Supplies 554 Seventh St. Parkersburg, W. Va. Fig. I- Schematic diagram of the 420 -450 megacycle transceiver. following page)

RADIO -CRAFT for MAY, 1946 585 INDEX TO ADVERTISERS Adson Co. 567 Olson Radio Warehouse 573 LAKE'S Aerovox Corp. 562 Onan & Sons, D. W. 575 RADIO Cabinets & Parts Allied Radio Corp. 549 Opportunity Adlets 563 Amperite Co. 577 Pa -kette Radio Co. 581 NOW Amplifier Co. of America 585 Paulson Co. 586 Available Arrow Electronics 569 RADIO SCHOOL DIRECTORY Audel & Co., Theo. 556 Page 588 Postwar Bell Telephone Labs. 526 American Radio Institute 2 Post Buffalo Radio Supply 582 Candler System Burstein-Applebee Co. 585 Cleveland Inst. of Radio Elec- RECORD - Cannon Co., C. F. 567 tronics CHANGER Capitol Radio Eng. Institute 528 Commercial Radio Institute Cleveland Inst. of Radio Lincoln Engineering School In luxurious brown leatherette portable case 559, 575 15" L x 15" W x 10" D. Latest electronic de- Elec. Melville Radio School velopments make this modern record -changer Concord Radio Corporation 523 RCA Institutes, Inc. the finest on.the market today! Cornell -Dubilier Elec. Corp. List Price.....$49.95 Dealer's net $29.97 Tri -State College Back Cover Western Radio Institute Also blank table cabinets of walnut veneer in the following sizes. with speaker opening nee left front Cox Radio 585 side. (Note: 7" has center speaker grill.) YMCA Coyne Electrical School 583 St1 - St/" L X 5I/" N x 4" D 51.95 E2 -10t/" L 63/4"H x 5' D 52.75 Crabtree Wholesale Radio 584 Radio Corp. of America 555 E3 -13t/a" L x 7S/a" N x 81/' D 53.25 Training, Inc. 525 Radio Electric Service 577 E7e -101/" L X 7" N it 5t /" D 52.50 DeForest's *Speaker Opening in center of front side. Electronics Service & Supply Co. 570 Radio Ham Shack 586 Radio Kits Co. 584 All types of radio cabinets and parts Free Want Ad Service 576 are at larger stock listed Singose catalog. General Cement Mfg. Co. 581 Radio Product Sales Co. 574 SERVICEMEN- RETAILERS & Join our ustomer list today. General Electric Co. 572 Radio Television Supply Co. 586 Write for our NEW. 12 page. illus. Radio Television, Inc. 568 trated. elaborate catalog) Order from Harrison Radio Co. 567 Wire Lake! You'll make no mistake) Co. 584 Radolek Co. 573 Deot. C Hazelton Instrument Hudson Specialties Co. 578 Raytheon Mfg. Co. 520 LAKE RADIO SALES CO. International Resistance Co 518 Rosicrucians 580 615 W. Randolph Street, Chicago 6, III. J. F. D. Manufacturing Co. 570 Scenic Radio & Electronics Co. 577 Equip. Corp. 571 Solar Capacitor Sales Corp. 581 H Kwikheát Div., Sound R S SPECIALS Lake Radio Sales Co. 586 Sprague Products Co. 524 WESTON METERS: Leeds Radio Co. 580 Sprayberry Academy of Radio 521 0 -5 MA-Mod 301 54.95 LeJay Mfg. Co. 583 Sun Radio Corp. 571 0 -100 MA -Mod 301 4.95 Liberty Sales Co. Inside Back Cover Superior Instruments Co. 519 0 -1 Amp -Mod 301 4.95 Inst. Co. 566 0 -150 V. A.C. -Mod 476 4.95 McElroy, T. R. 582 Supreme McGraw -Hill Co. 587 Supreme Publications 565 RG 58 /U Coax. .08 McMurdo Silver Corp. 557 "Tab" 583 RG 11 /U Coax. .10 Maedel Publishing House 587 Taybern Equipment Co. 581 RG 58 /U Per foot $.05 Maritime Switchboard 579 Technical Apparatus Builders 583 Metropolitan Elec. Inst. Co. 561 Terminal Radio 574 COIL SET: will tune to 2 through 30 megacycles with 235 mmfd condenser. Consists Murray Hill Books 550, 551 Triplett Elec. Instrument Co 563 ofa4 stages: 2 RF, 1 mixer, 1 oscillator, 4 National Radio Distributors ....581 Trutone Products Co. 584 coils in each stage, 20 coils in all, with 18 air trimmers, permeability slugs in each National Radio Institute 517 Turner Mfg. Co. 554 coil, 4 wafer ceramic bandswitch. Wired and National Schools 527 Ungar Electric Tools, Inc. 564 mounted on four separate shielding Plates Western . ready to put into set and connect. With National Union Radio Corp 553 Radio Institute 573 Diagram: Newark Electric Co., Inc. 567 World Radio Laboratories 560 Set $10.00 Ohmite Mfg. Co. Inside Front Cover X. L. Radio Labs. 582

1/3 with order RADIO A U.H.F. HAM TRANSCEIVER HAM SHACK (Continued from previous page) 63 Dey Sf., New York 7, N. Y. "nput power supplies such as poor reg- receivers and of Lecher wire frequen- Send for ~Catalog., ulation, severe load on tube, etc. A small cy checks has been covered recently (in TOOLS 6 EQUIPMENT for DEVELOPMENT rip- the and issues). The WORK WATCHMAKERS choke was included to help smooth January February TOOLS " - ple. Hum is inaudible on the speaker. CATALOGUE Using headphones there is a slight hum, I17Z6 of Precision Tools. Equipment rl _ for Development Work, for the as might be expected, but when the making of New Worlds. is oscillating or super -re- State your business when order- transceiver 400,, _1 ing catalog. is 20 f e generating it is very low and lost in IIIUAL 50 + 37 South Wabash Ave. 400V 2W the "rush." s0.. /200V HÉNRYPAULSON! £CO. CHICAGO 3.U.S.A. The output of the supply can be varied from zero (useful when making In the Rocky MountainRegionit's tests within the set or changing tubes, + 10 H etc.) to a full 225 volts at maximum Fig. 2-The variable -vo tage power supply. RADIO & TELEVISION SUPPLY CO. drain of 13 ma. A voltage control is al- - same principles apply to these higher 150 Hubson Ave., P.O. Box 892 ways desirable in connection with super regenerating receivers and is a good frequencies. The frequency calibration PUEBLO, COLO. of receiver and transmitter must be "If we don't have It. we'll get It- thing when testing the transmitter at or It can't be had! Phone 572W' different inputs. It will be noted that made to a closer tolerance as far as the voltage must be progressively in- actual dimensions are concerned. In O OUR SUBSCRIBERS creased for satisfactory results as the other words, a fraction of an inch dif- We are sorry that RADIO -CRAFT has not frequency devia- been reaching you on time lately. This has 500 me point is approached, otherwise ference means more been due largely to the difficulty in obtaining the super- regeneration drops out leav- tion above 400 me than it does below paper. Hundreds of other publications are the Lecher similarly affected. Fortunately conditions are ing only ordinary oscillation and a very 150. It will be found that rapidly improving. Effective with the next insensitive (See Fig. 2.) measurement will show a sharper indi- issue we hope to resume our normal mailing condition. schedule The operation of super- regenerative (Continued on page 588) 586 RADIO -CRAFT for MAY, 1946 /Uvw-142 "111111111111111111 EV 111111111111111111111111111111111111111111l1 @_- KR E I important design articles ELECTRONIC EQUIPMENT AND TWO -WAY RADIO by Samuel Freed- on ELECTRONIC equipment ACCESSORIES, by R. C. Walker. Pub- man, Commander USNR. Published by lished by Chemical Publishing Com- the Ziff -Davis Publishing Company. Stiff and parts .. . pany. Stiff covers, 5%2 x 8% inches, 392 cloth covers, 6 x 8 y2 inches. Price $5.00. pages. This handy reference This is possibly the most compre- book brings to design- This book, prepared principally for hensive text ever written about two -way ers, builders and users and students, presents in in- of electronic equipment engineers radio. It covers this entire field from and parts a host of teresting detail the fundamentals of fixed and mobile units to marine and valuable aids -material of which has been con- operation of many types electronic aeronautical applications. densed into graphs, equipment and their accessories. Low -frequency long -wave charts, and concise ar- applica- ticles, to supply you The first five chapters deal with the tions receive the same treatment as FM with a short cut to more and better reference more conventional types of vacuum and u.h.f. installations is data in your field. It contains a multitude of en- and theory. It gineering aids related to the design of circuits, tubes and their applications to metering rather surprising, however, to find in- equipment and .individual parts for radio, elec- in industry. terspersed amongst wave guides tronics, television, facsimile, radar, sound, and and related vacuum -tube apparatus-including topics Chapters six through eleven cover cavity resonators, basic reviews of brought into prominence by acceleration of war- light- sensitive and light -producing de- Ohm's law and elementary a.c. theory. time electronic research. vices, their fundamentals and uses in For example, the author speaks of Just Published commercial practice. Cathode ray tubes, "functional comparisons of v.h.f. versus photo cells and sources of light are in- microwaves," "beamed transmissions" ELECTRONICS for ENGINEERS cluded. Interesting applications of the and trapping as related to atmospheric Edited by JOHN MARKUS and VIN ZELUFF neon glow tube as a voltage regulator densities," then breaks off and presents Associate Editors, Electronics 390 pages, 8%Z x 11, figures, $6.00 is found in chapter eleven. the formulae for capacitive and inductive reactance, followed by a somewhat This rich source of data contains over a hundred Mechanical and electronic control de- different articles, each one a "find" for the elec- vices are covered in chapters twelve and lengthy dissertation on LC ratios tronics man who needs concise, easily available and Q. information to aid him in his work. It represents thirteen. The portion on mechanical design articles, charts. and graphs selected from switching is very complete. Working Some of the chapters, such as those the complete files of Electronics magazine for on two-way railroad radio, personalized their value to you. carefully condensed, edited, and diagrams of thermal delay, vacuum de- and private indexed, and arranged in easily accessible form. lay and mechanical delay switches are applications (citizen's radio), police, fire, and forestry services, 10 DAYS' FREE EXAMINATION COUPON illustrated. and maintenance and repair of trans- The closing chapter discusses, briefly, mitters and receivers, are more than McGrawH ill Book Co. 330 W. 42 St., NYC IS many of the fundamentals and applica- sufficiently interesting to offset Send mo Markus and ZeluR's Electronics for Engineers these for 10 days' examination on approval. In IO days I will tions not covered elsewhere in the book. minor digressions. send $6.00. plus few cents postage. or return book post- This includes a.c. and d.c. motors, paid. (Postage paid on cash orders.) small The nineteenth chapter, on licenses metallic rectifiers and regulators. and regulations, comprises a summary Name A thirteen -page appendix of various of the relevant parts of the Communi- Address mathematical formulae and relation- cations Act and new applications and City and State ships is a useful addition to this book. amendments as they apply to individual, Company PRINCIPLES OF RADIO FOR THE private firm or corporation, and public Position 11C -5.46 utility or semi For Canadian prices, write: Embassy Bo* Co.. OPERATOR, by Ralph Atherton. Pub- -official use of two -way 12 Richmond St. E.. Toronto 1 lished by The Macmillan Company. Stiff radio. The entire volume is interestingly cloth covers, 5 x 8% inches, 344 pages. illustrated and diagrammed throughout Price $3.75. and, except for minor inaccuracies, such as reference to the Civil Air Patrol as A simplified volume on radio theory, "Civilian Air Patrol," appears to be MATHEMATICS this easily -read book is an excellent accurately compiled. text for students. Freedom from mathematical phraseology, other than the TELEVISION SHOW BUSINESS by FOR simplest algebra, will make it easily Judy Dupuy. Published by General Elec- RADIO understood Two volumes, prepared for home study. by the non -technical reader. tric Company. Size 81/2 x 11 inches, soft is well Book I (314 pp.) the It illustrated with over five paper covers, 246 pages. Price $2.50. covers algebra, hundred drawings and photographs. arithmetic, and geometry; Book 11 (329 The first three chapters are devoted to Probably the first actual television pp.) covers the advanced algebra, trigo- the nature of electricity and the vari- production text book to be offered to the nometry, and complex numbers neces- general public is this manual by Miss ous methods of generating it. Ohm's sary to read technical books and articles Law is covered very well in this section. Judy Dupuy. It is strictly, as the title implies, on radio. The next three chapters are on mag- a non - technical manual, though netism and its application motors, the reader will unconsciously pick up a to certain amount of technical lingo along MAEDEL PUBLISHING HOUSE Room 117 generators and meters. 593 East 38 Street. Brooklyn, New York with the material on "How to become The last ten chapters are devoted Send me MATHEMATICS FOR RADIO AND a television director or producer in 36 COMMUNICATION as checked below. I enclose purely to radio theory. Each component easy lessons." payment therefor with the understanding that of the set is I may return the book(s) within 6 days in good explained in a surprisingly Somesof the mores interesting chapters condition and my money will be refunded. thorough manner for a text of this na- on telecasting cover variety shows and ture. As each part is explained, it is . revues, drama, television commercials, Name illustrated both photographically and studio and control room procedure, and diagrammatically, the symbol for the hints and tips for the television actor. Address component being learned at the same The scripting requirements are covered time. rather thoroughly. An up -to -date gloss- Teachers of beginners in radio theory ary of television terms and slanguage Book I at $3.75 plus 6c postage will find advantageous the visual train- (dictionary style) completes lesson 37. Book II at $4.00 plus 6e postage ing aids recommended at the end of Do's and don'ts summarized at the end Books I and II at $7.75 postage prepaid each chapter. (Continued on following page) Foreign and Canadian prises 25e per volume high& RADIO -CRAFT for MAY, 1946 587 sented. The diagram of the klystron is particularly interesting and is seldom RADIO SCH OL DIRECTORY seen in this form. _ _ Radio communication and television PREPARE NOW FOR SKILLED JOBS IN RADIO AND ELECTRONICS are discussed in the order of their MAKE a place for yourself in a new world of radio and electronics -a world in which chronological development. Some of the revolutionary electronic developments will require highly specialized technical little -known men of science who never- knowledge. Take a good course now to fit yourself for a good paying job. The training theless played important parts in the you need can be supplied by one of the schools advertised in this publication. development of modern communication t are mentioned. RADIO Television is described from the ear- Train With professionals. Conl- liest attempts to carry sight impulses Ditto. Intensified courses; ne- GC )Li pair & Maintenance. Cegraph- over a wire or through the air to the 1,7 cations. High -speed telegraphy. Ba 'Ray man. Learn how to send and Slip transcription. FCC trama, e by telegraph present schemes of color television. To a, r! ,radios Commerce needs thousands of men for Jobs. Good Spay. adventure. describe the modern methods inter- Wish School Students ac- interesting work. of as Mer- through fa Candlerm system. cepted for training Write for FREE laced scanning, lines of the page are - chant Marine Radio Officers. BOOK. to CANDLER SYSTEM CO. numbered in the same sequence as the Gov't sponsorship available Dept. 3 -5. Boa 928 , Colo.. U.S.A veterans. scanning within the electron tube. It is "A Radio School managed by radio men." 45 W. 45th St., Dept. RC. New York 19, N.Y. possible to read the page only when the MELVILLE RADIO INSTITUTE RADIO lines are scanned in the proper order. -77P-5enwe n A chapter discusses the effects' of RADIO Technician and Radio Communleations courses.: Register now for new classes starting first MONDAY atomic and solar disturbances on trans- RADIO COURSES of each month. Day and Evening Classes. mission and receptign of radio signals, RADIO OPERATING CODE and the final chapters deal with the re- RADIO SERVICING - ELECTRONICS AMERICAN RADIO INSTITUTE 101 West 83rd St.. New York 23. N. Y. lation between electrons and nuclear REFRIGERATION SERVICING APPROVED UNDER CI BILL OF RIGHTS. Personal Counselling Services for Veterans physics. Write for Latest Trade & Technical Catalog Y.M.C.A. TRADE & TECHNICAL SCHOOLS Correspondence Courses In W. 44th street New York City U.H.F. HAM TRANSCEIVER RADIO .3,0 ELECTRICAL ENGINEERING (Continued from page 586) ELECTRICAL ENGINEERING Goetgoodemsp trivet field. Prepare yourself. at Low Cost fordssecure future. Modem. Imnhl lied. understand daouickll`. cation than at lower frequencies. The RADIO RADIO ENGINEER! Fyou finC tí NGur adánrees. prom eere] r w"nrk. should be adjusted so that the Home Study Courses for Sedie Technicians and vacuum T coupling tTrainsrlñnu Servicesuper-service adlvn. real Ìic Radio Engineers. Prepare ow for a better Bndlo- tion. Tuition $25. c therteauór' Deferred clan. same reading will be obtained after Sob. Free Booklet gee mir large ads. haeÌ GÌOéent on pages 559, 575. te R E E gaines. complete details. SEND NO\Vl several tries, within MI inch or better. LINCOLN ENGINEERING SCHOOL interval represents Cleveland Institute of Radio Electronics Lit :Iñ3 ;t . Even this short 1% frequency. The hand RC -5 Terminal Tower Cleveland 13, Ohio about of the must not be kept too near the wires COMMERCIAL RADIO INSTITUTE during the measurement. (Fig. 3 is the Inc. A radio training center for calibration curve.) RCA INSTITUTES, twenty -four years. I Offer thorough training FREQUENCY ilviiirti courses in all technical phases of Radio and Television RESIDENT COURSES ONLY RATES DAYS- EVENINGS WEEKLY Broadcast, Service, Aeronautical. Television and Marino VETERANS: RCA Institutes is approved telegraphy classes now forming. Literature upon request. under G. I. Sill of Rights veteran training. Classes now forming for July 1st. 520 For Free Catalog Write Dept. RC56 Dept. C, 38 West Biddle St., Baltimore I. Md. RCA INSTITUTES, Inc. A Radio Corporation of America Service 71 VARICK STREET NEW YORK 13. N. Y. 500

I I I I I I I 11111111111 I I 1111111111111111 I I I i 11111 I I I I I L I I I I I I I I I I I I I I I I I 111111111111111111111111111 VETERANS can complete work LEARN RAPID = here in shortest possible time. 480 Courses also in Civil, Electrical, RADIO SERVICING Mechanical, Chemical, Aeronautical Engineering; Send for Free Information, "3 Ways to Learn Veterans. _ Business Administration, Accounting, Secretarial Radio." Approved for Training Science. 63rd year. Enter June, Sept., Jan., Mar. (See our ad on 573) 460 Dale School now filled to capacity. No applications can WESTERN RADIO INSTITUTE be accepted until further notice. 1457 Glenarm. Denver 2. Colo. :_ College Ave. TRI -STATE COLLEGE ANGOLA INDIANA g11111II IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIlI1111IIIIIIIIIIIIIIlll1111111111111l111la 440 BOOK REVIEWS (Continued front previous page) 420 i 4 of each chapter give the text a school- ELECTRONS IN ACTION, by James book flavor. Stockley, General Electric Research 4000 5 10 15 20 The continuity is excellent and very Laboratory. Published by Whittlesey DIAL nearly meets requirements of a per- -Hill Book Company, the House, McGraw Fig. 3- Calibration curve of the transceiver. fect book: To make the reader forget Stiff covers, 51/2 by 8 %z inches, 309 he is reading and feel that he is actually pages. Price $3.00. The new amateur band offers an ex- living through each chapter with the cellent chance to experiment with re- 1 This book provides excellent mate- flectors, polarization, etc. Thus, a sheet author. Were it not for the superabund- or stu- tele- rial for study by the layman of aluminum placed behind an antenna ant presence of General Electric's who desires a knowledge of the vision station call letters (WRGB) dent , will progressively and alternately in- of "everyday electronics." this manual would be 99 percent per- fundamentals crease and decrease the signal as it is fect. As it is, the slight marring of Fifty -four drawings, sketches and dia- moved steadily away from (or toward) enjoyment by this repetitious redund- grams are used for graphic presenta- it. Another rod or piece of tubing will ancy is more than offset by the excellent tion of the subject matter. These are act in the same manner. The latter may photographs and entertaining story on supplemented by forty -four well- chosen be held at its center by the hand as it is the lesser -known phase of television; and well- reproduced photographs. moved toward and away from the ra- the story behind the "ike- lights. " - The operation of the magnetron and diator. The effects of polarization are E.A.W. klystron oscillators is very well pre- clearly shown in this way. MAY, 1946 588 Printed in the U.S.A. RADIO -CRAFT for 4!e1 RADIO4«PHONØGRAPH R'ea,.:

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