Radio Digest (July 1924-Apr 1925)

July 19, 1924 RADIO DIGES T-— Illustrated 30 Minute A-B-C Lessons for Radio Beginners er XVIII, Part I — Hero Circuits of Radio By P. E. Edelman IN THIS series of articles the story of Radio is told in so simple a manner that the uninitiated can follow theory and practice whether or not he knows anything about electricity or its application to broadcasting' and reception. The series consists of twenty-flve chapters, of which the five next will he: Chapter XIX — What is Doing1 in Complicated Circuits. Chapter XX — How Tar Can I Hear? Chapter XXI — Choosing1 a Radio outfit. Chapter XXII — Making Your Own Radio. Chapter XXIII — Fixing Up the Radio Set. A RADIOCAST listener may well wonder where the Greek name circuits come from. Says one, "Old man DeForest started it by calling the vacuum tube 'Audion'." Someone decides Internal Tu&e Capacity between gsk? e> plwe Regenerator Figure 166 VteP GRID Mun Toned Plate Circuit JTut»eo IAeriai. _ 'Circuit ToNtt? Plate. Circuit ^RMSTSJOKGp COPLEY) Figure 167 that "dyne" would sound nice on a new variation, and, so a whole family of "dyne" circuits is begotten. Some of the "dynes," "flexes," etc., would hardly recognize their third cousins of the tribes, so TuNEP QlZ.lt? Circuit a FeepbacX [Jeinartz Regenerator Figure 168 the average listener soon decides that the name is less important than the PRE-AMPLIFIER Registered Makes Summer Radio Practical THE TWIT' HEU. PRE-AMPLIF1EH Is a powerful Radio Frequency Amplifier attachable to any receiving set. !t brir.fs in many distant stations which you cannot hear without It. Brings in with tremendous volume those you now hoar only faintly. i,u, :.t selective1. Prevent <: lotion. Price complete with tube $20.00 Shipped Prepaid S. A. TWITCHELL 1025 Western Ave. MINNEAPOLIS, MINN. "works." Another flock of so-called "hero" circuits are named after the designer who happens to publish a circuit. Some writers make sarcastic remarks about 5m<xLt Cohtrol. Reqenerato^. (gE RADIATES) Figure 168A * IK — CONPENSER FtEP&AOC Condenser. J^eqenera^or. Figure 169 Tuned Plate Circuit ARnS-TRONq-UEAGjAvVT FEEDBACK. Figure 170 such circuits, systems, etc., as are much press agented or trade advertised, but this is hardly polite. They will tell you for example that the popular Reinartz circuit is nothing but a regenerative hookup, but overlook the fact that numbers of users regard it as an improvement. The much discussed Armstrong circuit could in the same manner be called, "just another audion circuit." Regeneration Regeneration as an electrical principle is very old, dating back to the days of Ultra Aupiok Q?e Forest) Figure 171 Joseph Henry. The usual dynamo employs regeneration in building up a magnetic field when the armature sends a weak current through the field to react on the armature, etc. etc., over and over SENT FREE 'Radiol Then Get Our FREE Bulletin No. 92 It shows recent developments and improvements in parts and the kind you must use if you want the best in Radio. Send for this book today. tfLmim Quality Unsurpassed — For every known "Hook-Up" ALL GOOD DEALERS SELL THEM prmfar fyttivlt famynny 3810 Bavenswood Ave CHICAGO again until the field attains full strength. The howling or singing microphone formed by putting a receiver against a telephone transmitter comprises regenera ^ Absorb"*^ Circuit 1*J* AUSTIU ABSORBER Figure 172 CEYSTAL PETECTOR APPCP Figure 173 NEUTEALtZER o> Tube Capacity £\ce Neutralize*. Figure 174 tion. Regeneration itself is a principle of nature. One Tube Circuits So there is a legitimate field for attempts to improve Radio circuits by new combinations of principles and means. Some of the possible combinations as well as principles in use in various popular circuits will now be pointed out. Neutkauzer ^Tube Capacity Hazeltine-Jones Neutralize*. Figure 175 Tube Capacity Neutralize? * Figure 176 What One Tube Can Do Probably many listeners have wondered why a single tube could not perform all the functions of a series of tubes. Why not amplify, detect, amplify, etc., all with one tube? There is no theoretical reason why not, except the capacity of the tube and the difficulty of arranging non-interfering circuits in correct phase relation. Aside from the cost of the tubes and the upkeep, boiling down of the number of tubes is no special advantage, unless simplicity results. Figure 166 indicates a typical regenerative receiver with an equivalent dynamo circuit. Feed back can be inductive or capacitative coupling. Such a receiving circuit can be made to radiate energy. (Continued on page 16) What a whale of a difference just a few cents make!" — all the difference between just an ordinary cigarette and— FATIMA, the most skillful blend in cigarette history.