DOCSLIB.ORG

1991-07: the Story of Reflexes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
1991-07: the Story of Reflexes VII liliLdi gp e IRa~dln~o by PETER LANKSHEAR The story of `Reflexes' This month's column is not about rubber hammers and kneecaps, but a technology that persisted throughout the history of valve radio, and one that was exploited to its greatest extent in Australia. With semiconductors available today tal detector and then reflexed the audio valves coincided with a boom in at only a few cents apiece, it is difficult back to the grid of the valve to again `midget' radios, and an increasing de- to appreciate just how expensive ampli- amplify the signal. Any problems like mand for car radios. Economies in space fication was in the early days of radio. erratic operation and distortion were of and battery consumption became import- Not only valves, but every milliampere- little consequence. ant, providing an incentive to resurrect hour of precious battery power cost a lot reflexing. of money. Any way to economise was Early superhet use From late 1933 the Americans, espe- well received. An early 'high tech' application of re- cially RCA, made some use of the 6B7 in During World War 1, much research flexing was in Edwin Armstrong's first car radios as a reflexed IF and trans- went into triode valve applications. One generation of RCA superheterodynes, in former-coupled audio amplifier, with the US Navy worker, W.H. Priess, patented 1924. To keep the number of valves to a one valve providing IF and AF amplifi- the concept of passing a signal twice minimum, the first valve was used as an cation, diode detection and AGC. This through the one valve — once at RF and RF amplifier, and then again as the first was an effective system, but a problem then, after detection, at audio frequen- IF stage operating at about 50kHz. was that it was practically impossible to cies. Provided that there was no over- After 1925, as valves became cheaper, make an inexpensive wide range audio loading, with `reflexing' (as it was and users became more critical of its coupling transformer with sufficient in- called) one valve could, theoretically, do complications and limitations, reflexing ductance for pentodes such as the 6B7. the work of two. was generally abandoned. But during The result was a restricted audio re- There seems to have been little im- 1932, the 6B7 and 2B7 double-diode- sponse — acceptable enough in a car, but mediate interest, but with the advent of pentodes, and the 6F7 triode-pentode ap- inadequate for a domestic receiver. broadcasting, reflexing became an at- peared. Each had a general purpose With its pentode section used as an RF tractive proposition to manufacturers pentode suitable for both RF and AF am- or IF amplifier and the triode as an audio and experimenters. Notable 1922 models plification. The triode of the 6F7 was amplifier or detector, the 6F7 soon be- were Marconi's two valve V2, and De suitable as a detector or audio amplifier, came a popular alternative to reflexing Forest's D7 with three valves. Similarly and the diodes in the other valves were for economical and compact receivers — many enthusiasts used their one precious for detection and AGC. typical Australian examples being the valve as an RF amplifier feeding a crys- The arrival of these multifunction 1933 Healing 44F and Stromberg Carl- Regenerator Unit CIRCUIT DIAGRAM OF THE MARCONIPHONE V.2 RECEIVER Figl: One of the earliest British receivers made commercially was the 1922 Marconi W22', a reflex with the first valve combining the functions of RF and AFamplifler. Marconi used plug-in 'pancake' coils, tuned by adjustable copper 'spades 86 ELECTRONICS Australia, July 1991 O-?1f high, a less complex system became pop- ular for economical receivers. Many Eu- A-337 r !~ ropean output pentodes, such as the PENA4, AL3, and EL3 had very high 6F7 12A7 mutual conductances — typically g A-243 9mA/V, compared with the 2.5mA/V of E i A-340 the standard 2A5, 42 and 6F6 pentodes available in the US. With an efficient IF amplifier it was possible to eliminate the audio voltage amplifier, by driving these high gain valves directly from a diode detector. A-34/JI The EL3 even had diodes incorpo- (orA-339) R-263 rated, to become the EBL1 for this ser- R-138-4b1. vice. Unfortunately the EBL1 was a very R-255 tall valve, limiting its use in compact U-fOorU-fff f2A7 6F7 receivers. Circuit of the final run on the Kadette Jr., Modal F. Some early Australian sets such as the 1933 Astor OX, and a few New Zealand Fig.2: Using two double valves and a classic example of reflexing from 1933, the `Ultimate' sets, did use this arrangement International Kadette Jr was a 'midget' which could be fitted into an overcoat but their use of the insensitive American pocket. The pentode section of the 6F7 was both RF and AF amp, with volume pentodes was a serious limitation. Later, controlled by varying its screen voltage. The triode section of the same valve was the Radio & Hobbies `Little General', used as a grid-leak detector. Note the absence of a power transformer. using the higher gain beam tetrode 6V6G, was quite successful in good re- son 564. Some writers confused this with If AGC was used, there was 'play ception areas. reflexing, but the concept was quite dif- through', or significant audio output ferent — multiple valves within the one even with the volume control at zero. As By 1937 reflexing had been pretty well envelope, rather than multiple use of a the control was advanced, there was a abandoned in America, but not so in this single valve. `minimum volume' effect accompanied part of the World. New Zealand's Ulti- However the American firm Interna- by distortion. As a compromise, some mate produced a small four-valve reflex tional did reflex the 6F7 in their unique receivers did not use AGC, but had the during the period 1937-39, but Australia 1933 `Kadette' TRF series. Claimed as manual volume control ahead of the IF became the real stronghold of reflexing. 'The World's Smallest Radio' (for amplifier. `World' read `America'), a Kadette could Other problems included distortion at The great Aussie reflex be fitted into an overcoat pocket. They high modulation levels, and total re- The second generation of reflexing had only two valves, combining the ceiver gain was significantly less than was to be taken up enthusiastically in functions of RF amplifier, grid leak de- with the use an extra valve in a conven- Australia — particularly by AWA, who tector, two AF stages and mains rectifier! tional receiver. in 1934 introduced the fust of their re- Emerson and RCA made some small In Europe, where signal strengths were flexed Radiolettes, the model 27. reflexed domestic superheterodynes in the mid 1930's, but they resorted to a resistive audio load for the 6B7. This compromise improved the audio perfor- mance, but created a serious limitation for IF/AF reflexing that was never fully overcome. Limitations There is insufficient space here to cover all aspects of reflex design. Read- ers interested in a full discussion are re- ferred to the classic Radiotron Designer's Handbook, where an entire chapter was devoted to reflexing. Briefly, to obtain a reasonable audio gain, the anode load resistor of the re- flexed amplifier needed be of the order of 50k to 100k ohms. At the same time, RADIO ANC/ N0R011 for an acceptable IF performance, at least REFLEX RECEIVER 100 volts were needed at the anode. With 24OV HT supplies normally around 250V, the DRAWNM W maximum current through the anode re- Fig.3: This 1952 'Radio & Hobbles' design represents the final development of the sistor was therefore restricted to less than Australian reflex, with the screen grid of the 6AR7-GT IF valve acting as the audio 2mA — inadequate for good IF amplifier stage anode. Breakthrough and low level distortion could be avoided only by performance. using a manual gain control. ELECTRONICS Australia, July 1991 87 VINTAGE RADIO Anienns Despite the shortcomings of reflexing, 000>M. f the little five valve Radiolettes proved to y lktiziargavyerf C—, be very popular with the public, although -1f------ AblbrCä7 .0 less so with servicemen! a,T vx 49,50 With more gain than a straight five- valve receiver, their extra sensitivity A could be useful. Shortwave models were 41111, O added to the range in 1936. Other firms OAS • too found a demand for reflexes. The Flg.4: The wheel goes 1938 Australian Official Radio Service 401. full circle! At right is the 411, Manual lists eight different brands of re- National one valve reflex flex receiver, including battery powered for hobbyists, dating GM versions. from 1925, while below is 001 Au: arc* For about 15 years Australia persisted its solid state equivalent, anans' - with the reflex. AWV even developed described 37 years later agar '•• 1 valves more suited to reflexing than the by Jim Rowe in the then whiv Nand Hobbies 1 -TUBE semi variable-mu 6B7 and its octal `Radlo, Rhea 10s" REFLEX equivalent, the 6B8G. There was an ex- tended-cutoff and better shielded ver- X4r' sion, the 6B7S, and later in octal form, 0 0 0 the 6G8G. Then in 1949 came the unique -A +A tB lead shielded 6AR7GT, with more than -B If r. double the transconductance of the 6B7. An interesting but late improvement came in November 1947, from a Radio REACTION & Hobbies reader, S.L. Marsh of 10K .0047 HIGH Belmore in NSW. By using the screen IMPEDANCE grid of the reflexed valve as a triode PHONES anode at audio frequencies, the pentode anode could be run at full current and voltage.
Load more

Recommended publications
  • Valves Were Expensive in the Early Days of Radio and So Designers
    By RODNEY CHAMPNESS, VK3UG would become gassy. Occasionally, even today, a valve with a purple glow inside it will be seen and this is often an indication that the glass to metal pin seal is not perfect and air has leaked VICTORIA into the valve. Incandescent light globes were the first items to have metal pins or wires protruding through a glass envelope. However, this created no real problem, since the vacuum created was satisfac- tory for their operation and the glass- to-metal seals were not as critical. In some cases, the globe was filled with an inert gas such as nitrogen to prevent Above: the Kriesler 11-41 was a popular evaporation of the filament. 4-valve reflex receiver from the 1950s. One problem with valves was that the metals used inside them (ie, for the elements and filaments) had to Valves were expensive in the early be carefully selected, otherwise they days of radio and so designers came up could emit gases when they became hot. These gases could then "poison" with clever techniques to minimise the a valve and adversely affect its per- valve count. One technique was known formance. So early attempts at making valves as "reflexing" and involved using the into viable amplifying devices encoun- same valve to work as both an RF or IF tered many difficulties. However, their potential to revolutionise radio was amplifier and as an audio amplifier. obvious and so a great deal of effort was put into solving these problems. It is for these and other reasons that valves were by far the most expensive nOMPONENTS such as tuning ca- had a small amount of gas left inside, and fragile components in early valve pacitors, inductors (both fixed and due to manufacturing limitations.
    [Show full text]
  • RF Communications : Systems & Circuits
    ELEN 665 RF Communications : Systems & Circuits Edgar Sánchez-Sinencio [email protected] Analog and Mixed-Signal Center,Texas A&M University 1 Fall 2009 WHAT ARE THE MAIN TOPICS INVOLVED TO FULLY UNDERSTAND RF DESIGN ? IC DES S IGN ON TI AND CA DEV NI ICES U MM CO N ICROWAVE G M SI E D TECHNIQUES F R SIGNAL PROCESSING APPLICATIONS 2 Analog and Mixed Signal Center, TAMU ELEN 665 (ESS) INTRODUCTION AND MOTIVATION • HOW DO LIVING BEINGS COMMUNICATE ? • HOW CAN WE MIMIC HUMAN COMMUNICATIONS ? • WHAT ARE THE FUNDAMENTAL ARCHITECTURES OF WIRELESS RECEIVERS AND TRANSMITTERS ? • WHAT ARE THE FUNDAMENTAL PROBLEMS IN A RECEIVER? How does non-linearity play a role? 3 Analog and Mixed Signal Center, TAMU HowHow dodo livingliving beingsbeings communicate?communicate? • Communicating is something that all animals, including humans, do. It could be a dog barking a warning, a cat arching its back, or crickets chirping, animals are always sending messages to each other. • Animals and plants react to stimuli which might come from other living things or from the environment. A stimulus usually causes the organism which receives it to respond to it. Animals use all their senses to communicate. • For example, some male birds develop colorful plumage so that the females will be attracted by a visual stimulus as well as by sound. • Bees (dogs) communicate by means smelling (sniffing). • Dolphins communicate through sounds. 4 • The signals which an organism uses can be visual (sight), sensual (touch), auditory (sound) or chemical Marine mammals establish contact with specific individuals using short-range vocalizations. The most singular example of marine mammals using sound to make or maintain contact is between mother and offspring.
    [Show full text]
  • Build an Old Time One-Valve Radio T
    •~ a.. e e Ifito .ega'3a, . tr Ssc~ . a~:r"..,`'r"'~g~~ t.~.= ~ y~~..i•'`'E~;sr,:~ .?-~`.r ;~'~I:i'Y ~~":'-:2i:5'-~'r:" *: ap~ i d -.t e -•i' e'•,y`. z'a--'~ ~a.r •~`,`'t ,'-yerk',t"3-c .rLt ~`u"r. ,~,`.~f'F' 06***104r"' G: _•ad2r. r,`r,*•r--,.x-00-fti;,s -,yr-4.o o-+J-0,0_4 03-c?'rv7-F * Special `nostalgia' project: BUILD AN OLD TIME ONE-VALVE RADIO T There's a lot of interest nowadays in building simple valve-based radio sets, of the type that were popular from the 1920s right up until the 1960s. Here's the first of two articles which give all the information you'll need to construct an authentic one-valver starting with a basic `grid-leak' set and progressing to a regenerative circuit with surprisingly good performance. Enough information is given to allow you to use almost any old valve or other components to hand. by PETER LAUGHTON Cleaning out my radio `shack' (read had, and how much I'd learned. This, cussion is the following project. mess) the other day, I came across a along with several recent Letters to The circuits described can be built number of radio receivers that I con- the Editor asking for more vintage using almost any combination of com- structed years ago based on valves, radio projects, resulted in me talking ponents, even from junked valve TV and remembered how much fun I'd to Jim Rowe, and the result of that dis- sets.
    [Show full text]
  • Acme.Pdf (8.05Mb)
    Amplification without Distortion A Discussionon Radio with Particular Refer- ence to the Construction and Operation of Radio Audio and "REFLEX" Amplifiers and Sets. Have you ever stopp€d to cousider what makee it poseible for you to hear the distant broadcasting station, to fill the room with music, to communicate with the amateur hundreds of miles away? It is amplification-the key to Radio, Amplification is used on both the transmitter and receiver, and with it thc ringer's voice in New York is transported to the farm in Ohio, or the President of the United States talks to the whole country just as though he werc in milliona of homes at the same time. But Radio without amplification would be a ship without a sail ! Amplification eliminates distance and permits a room or hall full of peoplc to be entertained simultaneously, but the limits of radio and amplification should be clearly understood, especially in regard to distance. The transmission rangc of radio varies greatly between day and night, city and country, summer and winter, and from oight to night, and in such a manner that no €ract rante can be specified for aoy particular aet. August, 1924 At-ti'n .. s the most eimple radio e€t will pick up broadcasting ltations at con- sidersble distancesaway, but usually this reception is a freak, anJcannut be dupli. cated at will. As the set becomes more elaborate (that is. as amplification'sreater is added) the reliable distance over which it will operate becomeg and treater up to a safeestimate of 300 to 500 miles in the winter eveningswhen using a loud speaking telephone and loop antenna.
    [Show full text]
  • Electronic Home Music Reproducing Equipment
    Electronic Home Music Reproducing Equipment Daniel R von Recklinghausen Copyright © 1977 by the Audio Engineering Society. Reprinted from the Journal of the Audio Engineering Society, 1977 October/November, pages 759...771. This material is posted here with permission of the AES. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the AES by contacting the Managing Editor, William McQuaid., [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it. John G. (Jay) McKnight, Chair AES Historical Committee 2005 Nov 07 Electronic Home Music Reproducing Equipment DANIEL R. VON RECKLINGHAUSEN Arlington, MA The search for amplification and control of recorded and transmitted music over the last 100 years has progressed from mechanical amplifiers to tube amplifiers to solid-state equipment. The AM radio, the record player, the FM receiver, and the tape recorder have supplemented the acoustical phonograph and the telephone. An incomplete summary of important developments in the past is presented along with challenges for the future. Home music reproduction began when Bell invented the tromechanical repeater caused it to be used for 20 years telephone in 1876 and Edison invented the phonograph in more as a hearing-aid amplifier [5, pp. 64-69]. 1877. Instruments were manufactured soon thereafter and C.A. Parsons of London, England, inventor of the leased or sold to the public. Yet the listener had very little Auxetophone, marketed in 1907 a phonograph where the control over the reproduction and the volume of sound, the playback stylus vibration caused a valve to modulate a tone quality being predetermined by the manufacturer of stream of compressed air which was fed to a reproducing the phonograph and record or by the telephone company horn [6].
    [Show full text]
  • Amplification Without Distortion
    Amplification without Distortion cAcme Apparatus Company • ElGHTH BDmON Amplification without Distortion A Discussion on Radio with Particular Refer� ence to the Construction and Operation of Radio Audio and" REFLEX" Amplifiers and Sets. Have you ever stopped to consider what makes it possible for you to hear the distant broadcasting station, to fill the room with music, to communicate with the amateur hundreds of miles away? It is amplification-the key to Radio. Amplification is used on both the transmitter and receiver, and with it the singer's voice in New York is transported to the farm in Ohio, or the President of the United States talks to the whole country just as though he were in million.. of homes at the same time. But Radio without amplification would be a .hip without a sail! Amplification eliminates distance and permits a room or hall full of people to he entertained simultaneously, but the limits of radio and amplification should be clearly understood, especially in regard to distance. The transmission range of radio varies greatly between day and night, city and country, summer and winter, and from night to night, and in such a manner that no exact range can be specified for any particular oet. B.&.N A-920 February, 1925 At times the most simple radio set will pick up broadcasting stations at con­ siderable distances away, but usually this reception is a freak, and cannot be dupli­ cated at will. As the set becomes more elaborate (that is, as amplification is added) the reliable distance over which it will operate becomes greater and greater up to a safe estimate of 300 to 500 miles in the winter evenings when using a loud speaking telephone and loop antenna.
    [Show full text]
  • The KH-27 RECEIVER by Kenneth Harkness
    TELEVISION ON LIGHT RAY! 15 Cents Tubeless Amplifier Announced D10 Grid Biasing Through Resistors Reg. U. S. Pat Off. A Simple 4 -Valve Circuit America's First and Only National Radio Weekly Hookup for Overseas 'Phone Set ol. 10 No. 19 Illustrated The KH-27 RECEIVER By Kenneth Harkness FIG. 1-The wiring diagram of Kenneth Harkness' latest receiver, the KH-27. See article on page 3. J.; FIG. 2-Top view of the receiver after the wiring has been completed. 110W TO RID RECEIVERS OF PARASITIC NOISES 1,ANGMUIR'S GREAT LABORATORY ADVENTURE RADIO WORLD WITH so much interference these days, why not improve your detector tube action and gain selectivity? Simply install a Bretwood Variable Grid Leak.Price $1.50. .,.moo al The Bretwood Variable Grid Leak NORTH AMERICAN BRETWOOD CO., 143 West 45th Street, N. Y. City. Enclosed find $1.50, for which send me one Bretwood THE Bretwood Variable Grid Leakmay Variable Grid Leak (or $2.00 for leak with grid condenser attached) on five-day money -back guarantee. be installed in any receiver ina few minutes.Single hole panel mount makes NAME this possible. Use a Bretwod andmarvel at STREET ADDRESS the difference! CITY and STATE (Inquiries Invited from the Trade) By ARTHUR H. LYNCH How to Build A Series of Five Important Articles on THE DIAMOND 5 -Tube Model HOW TO USE THE DE LUXE SYSTEM Herman Bernard, designer of this wondercir- mai, has written at, illustrated bookleton "How This seriestells how tobuildthe 2 -tube to Build RADIO WOILD'S Improved Diamond the Air." of De Luxe Receiver (without audio) and how to Send 50c and getthis booklet,in- cluding afull -sited wiring blueprint and free adopt this or any other set so as to obtain the name piece.
    [Show full text]
  • Circulation Larger Than That of Any Other Radio Publication
    CIRCULATION LARGER THAN THAT OF ANY OTHER RADIO PUBLICATION SEPTEMBER 25 Cents Over 200 Illustrations Edited by HUGO GERNSBACK r ulf ist tN . ri aumum SCIENCE and INVENTION RADIO REVIEW AMAZING STORIES RADIO INTERNACIONAL www.americanradiohistory.com Radio News for September, 1926 193 majestically sweet LKE the grand cathedral organ- Due co the exclusive direct -drive unit mighty monarch of all musical in- with its eight points of contact from unit struments -the new Tower Cone runs the to cone, the new Tower Cone gives not entire gamut of tone, bringing to you each only a complete range of tone, but a note, majestically sweet and clear -with beauty of "voicing ", and a' responsiveness the variety of color and shading de- to changes of tempo, long sought but manded by the real musical critic. never until now achieved. Your Dealer Will Be Glad to Demonstrate www.americanradiohistory.com Radio News for September, 1926 'NIEWS Published by EXPERIMENTER PUBLISHING COMPANY, Inc., Publishers of "Radio News," "Science and Invention," "Radio Internacional," "Radio Review" and "Amazing Stories." Editgrial and General Offices: 53 Park Pl., New York City H. GERNSBACK, President. S. GERNSBACK, Treasurer. R. W. DEMOTT, Secretary Member: Audit Bureau of Circulations Radio Magazine Publishers Association SEPTEMBER, 1926 NUMBER 3 Contents of This Issue: [®3 Is Radio at a Stalidstill? The Eusonic Receiver, By Hugo Gernsback 203 By Joseph Bernsley 228 How to Make Radio Pay Your Way, How to Build Wireless Receivers, By C. William Rados 204 By Edmund T. Flewelling 231 Television an Accomplished Fact, A Family Receiver, By Watson Brown 232 By A.
    [Show full text]
  • Rado May03 1924 .Pdf
    2 Radio Doings Business Has Been So Good This Week That We Have'nt Found Time To Write An Ad KENNEDY ghc1Royally g' (Radio Ask Any Kennedy Dealer WHOLESALE ONLY KIERULFF & RAVENSCROFT 1630-1632 South Los Angeles Street, Los Angeles, Calif. Phones: ATlantic 3125-ATlantic 3303 1Rabio doings Phone TRinity 6062 H. C. CHARLES, Editor 1.T.PERDUN,Manager HALL BERRINGER, Technical Editor Branch Manager: R. L. CONNER, 703 Cunard Bldg., San Francisco, PhoneGarfield 4557 Advertising Representativest J. C. PENLEY J.B. SHILLINGFORD LEE FELTSKOG 308 Van Nuys Building Los Angeles, Calif (Entered assecond-classmatter,November 25, 1922, Los Angeles, California Post Office, Cinder Act of March 3, 1897) Copyright,1924,by Harwood PublishingCo. FiveCents a Copy Two Dollars a You. Vol. IV. Los Angeles, May 3, 1924 No. 18 National Music Week THE week of May 6th to 12th has bee designatedMusic Week.It is particu- larly fitting that the radio public should help tocelebrate this week.Radio and broadcasting without music would be like arailroad train without the engine or an automobile with no gasoline. Weshould all get tired in a very short time of listening in to just talk. Music, since the early days of history, has alwaysentered into the culture of all nations.Most countries have music that is distinctive.It is easy to distinguish an Italian, Spanish, Irish, Scotchair as soon as you hear it, and it seems to fit the natures of those inhabiting these countries.So we have music for all moods and fancies.Music can inspire us when we hear out nationalanthems, and can make us sad when we hear funeraldirges.
    [Show full text]
  • Reflex Radio Receivers 1924 Ocr.Pdf
    The "Experimenter's Library" 25c. Books Covering Every Branch of Radio Each book is written by a well-known author and con• tains 48 pages of valuable (••HM.TICAI. KflOlO information, fully illustrated. ftWf(U(Ni". r,fr.v Cover is in two colors, size 5/4 x7K inches. No. 1. Tips for the Radio Amateur Constructor. Hi No. 2. How to make Practical Radio No. 3. Receiving Set*. Radio Questions Answered. No. 4. Radio Frequency Amplification No. 5. Loud Talkers and How to Build Them. No. 6. IftAOlC QUESTION ALL ABOUT • How to Tune Your Radio Set. RADIO PARTS No. 7. 100 Radio Hook-ups. No. 8. All About Radio Parts. No. 9. History and Operation of the No. 10. Vacuum Tube. The Neutrodyne—All About It. No. 12. How to Locate Troubles in Your Radio Set. I © T«t(..^ Each 25c. Postpaid HOW TO TU«F. you ft f- flO.O SET THE CONSRAD COMPANY, inc. Selling Agents 233 FULTON STREET NEW YORK CITY THE EXPERIMENTER'S LIBRARY, No. 13 Reflex Radio eivers By P. E. EDELMAN TRADE Published by THE E. I. COMPANY 233 Fulton Street New York City Printed in the United State* of America Copyright by THE E. I. COMPANY 1924 All rights reserved, including: that of translation into foreign languages, including the Scandinavian INTRODUCTION. The growing popularity of reflex types of broadcast receivers is due to the efficient use of fewer vacuum tubes than equivalent outfits of different character re• quire. The reflex principle was proposed by Schloemilch and Von Bronk in their U.
    [Show full text]
  • Transistor Circuits Mai{Uai
    7 No. f 68 216 TRANSISTOR ,'\ ) CIRCUITS MAI{UAI, { No. 4 by CLIVB SINCLAIR C,lTTCLI'IS I!,\I] iiis] R,UCTXOiVS F]S}I BLIilLDING "frvo L tran.sistor supr:rilet. ). Ii!-Fi tape acri picii-up pre-arnp. l. lli-lji 3+irtt unrpli!iir- l. triiii;rture ma:.;\ D.:\,.cr packs. 5. 5 ficis to 2 mc/s sign:il injecfor. 6. Scnsitive subrtiniaiure lcudsgre:rker.racllo, 7" Single t;rrasistor reg;r_.ner*tivereceiver. .i5-rrntf $, puirlic arirlrer;sanip!ifiei. -[ransirlor 9, voltmrrer. Ii.i" Sirnple earpiece r.eflex receir.er. ; i. Simp)i..transnritter. BERNARDS RADIO MANUALS r TRANSISTOR CIRCUITS MANUAL No. 4 by CLIVE SINCLAIR LONDON BERNARDS (publishers)LT.D BERNARDSRADrO MANUALS No. 168 GeNrn.,rr-Eorron : CLIVE SINCLAIR First publishedDecember 1960 Repr.in,tedNovember, 1964 ReprintedJanuary, 1966 ReprintedMay, 1967 On Page II TAPE AND PICK-UP PRE..{N,PLIFIER In third paragraph of text, third line should read : 8 volts, not 2 volts. On Page 12, Fig. 3 The 330K rcsistor betweenthe beseof Tr. I arrd the emitter of Tr_I should bc of pre_settype. o 1e60. Printed by V. Cooper parrners - & Ltd. Flitcroft Street, W.C.2. I'or Bernards(publishers) Ltd., The Grampians,western Gate, w.6. l* '- l CONTENTS Page Introduction 5 Noteson useof OCl69 transistor :'. 6 l. Two TransistorSuperhet.., 8 . ) I'Ii-Fi Tape and Pick-Up Pre-amplifier... 11 3. Hi-Fi 3-wattAmplifier 15 4, Miniature Mains PowerPacks ... l8 5. 5 Kc/s to 2 mc/s SignalInjector... 2L 6, SensitiveSubminiature Loudspeaker Radio 23 " 7. The " Mighty Atom SingleTransistor Receiver t{ 8.
    [Show full text]
  • No.17 Single-Transistor Reflex Radio Arrange the Blocks and Attach the Earphone and a Lead Wire (Used As an Antenna) As Shown in the Figure
    in this project Blocks used Radio Circuits No.17 Single-transistor Reflex Radio Arrange the blocks and attach the earphone and a lead wire (used as an antenna) as shown in the figure. Then, turn on the main switch. Put the earphone in one of your ears. Turn the tuning knob back and forth bit by bit until you find a radio broadcast station that you can pick up. The transistor first amplifies high-frequency signals and then amplifies the low-frequency signals detected by the diode that have been returned to the transistor. A radio that works to amplify both high-frequency signals and low-frequency signals using the same single transistor, as described, is known as a “reflex radio.” * In blocks with lighter lines, current only flows along Block Layout Diagram the dark, solid lines. Circuit Schematic High frequency Voltage doubler detector Low frequency Circuit Mechanism As a basic outline, the transistor-based amplifier circuit formed using the 1-kΩ resistor and 1-MΩ resistor connected to the base and the 1-kΩ resistor and 4.7-kΩ resistor connected to the collector operates twice, once for high-frequency signals and once for low-frequency signals. First, the high-frequency signal current is received from the secondary coil of the tuning coil. The current is amplified by the transistor as it flows along the path indicated by the dotted line in the figure at right. The 100-pF capacitor passes only high-frequency signals. As shown, the high-frequency signals flow along the path indicated by the dotted line to enter the voltage doubler detector circuit (described below).
    [Show full text]