Radio Digest (July 1924-Apr 1925)

July 26, 1924 RADIO DIGES T— Illustrated 30 Minute A-B-G Lessons for Radio Beginners Chapter XVIII, Part II — 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-five chapters, of which the five next will he: Chapter XIX — What is Doing1 in Complicated Circuits. Chapter XX — How Far Can X Hear? Chapter XXI — Choosing1 a Radio outfit. Chapter XXII — Making Your Own Radio. Chapter XXIII — Fixing* Up the Radio Set. IN FIGURE 177 the Radio output is rectified by a detector and put into the grid circuit as an audio current. Another reflex circuit is shown by Figure 178. Such circuits can be made to give nearly the equivalent of one stage Radio plus one stage audio amplification added to a detector. Xiink Circuits Link circuits are not much used in Grid Leaic Resistance. J?ADioTRA,NSFORrie.ie Reflex (Phantom Input) Figure 177 \v broadcast reception but the principle is shown in Figure 179. This will lessen tendency of oscillating receivers to reradiate energy and also affords desirable selection. Super One-Tube Circuits Another class of circuits aims to in crease the amount of regeneration which can be used on one tube. Familiar examples are indicated by Figures 180 and Tlt»>M5 |?EFLEX WITH 'PEQENtRffTiON^AToy: RtDtSM^) Figure 178 181. In such circuits, a self oscillating circuit is set up in the tube to modify the grid potential to permit using regeneration beyond the point which otherwise would not be feasible. Such circuits are effective when carefully adjusted. The principle of operation is diagrammed by Figure 182. An initial grid potential variation is maintained so that <vin< Orcuit (j?eqENEieA7)VE.) Figure 179 the amount of regeneration may be. increased. Possible One Tube Circuits One tube can do any of the following and so combinations are possible. A dia . Perfect! THE LOW LOSS GENERAL INSTRUMENT CORPORATION GROUNDED ROTOR CONDENSER LABORATORIES Because actual tests have proved that dielectric USE IT losses have been practically eliminated. This makes it possible for your receiving set to surprise you with a new power. RECOMMENDED A Professor of Radio Engineering in instruct BY A RADIO ing his pupils said that to attain results such PROFESSOR as no other variable condenser will produce you must use the Low Loss General Instrument Grounded Rotor Condenser. REPLACE YOUR If you are really anxious to "hear the difference" OLD CONDENSER to get greater selectivity, more distance and a remarkable increase in volume, replace your old condenser, with the NEW LOW LOSS GENERAL INSTRUMENT CORPORATION GROUNDED ROTOR CONDENSER. You'll hear the difference. Minimum Maximum Type 46X 11 Plate 5 MMFD. .00025 MFD $4.50 Type 46A 13 Plate 6 MMFD. .0003 MFD. 4.50 Type 46D 21 Plate 9 MMFD. .0005 MFD 5.00 Type 46F 43 Plate 15 MMFD. .001 MFD 5.50 AT YOUR DEALER Otherwise send purchase price direct to us and you will be supplied. General Instrument Corp. 423 Broome Street NEW YORK CITY ((( gram of possibilities is indicated by Figure 183. 1. Amplification, Radio. 2. Amplification, audio. 3 Self oscillation. 4. Heterodyning1. 5. Detecting1. 6. Refiexing", Radio or regeneration. 7. Refiexing, audio. 8. Refiexing of heterodyned frequency output. 9. Phase adjusting. 10. Super-regeneration. X7 L WoCTUHCE. 0* PhOHM. Inductance r ■= CorL P.UrtSOO ~ HiqH FR.EQ0E.KOr for <*R«> Coiv, Autoplex One. Tube Sope*. Figure 180 Flevjellin^ One Tube Super., Figure 181 To utilize more than one principle, the proper initial operating conditions, grid potential, and plate voltage must be employed. In general, to get loud volume from one tube, the initial plate voltage must be raised so that five to ten milliamperes plate current can flow. This will permit loud speaker output but limits Alternating initial Potential Contbcu PUT HERE Plate, Circuit Feedback. Super eeqeneeation Figure 182 Self ^ OSCILLMKaO JgAPio Output]; & IPETECTORh Phase ADJUSTER Auwo Output CGqEriEKWUOH. Possibilities of One Tvbc Figure 183 what else can be done at the same time. Complex circuits become difficult to handle. (What is Doing in Complicated Circuits, will follow in this series. — Editor's note.) Plain type: 3-plate $1.25 5-plate 13-plate 17-plate 23-plate 43-plate $1.50 $2.00 $2.50 $2.75 $3.00 at dealers Vernier type: 13-plate $4.00 23-plate $4.50 43-plate $5.50 at dealers A SCOTCHMAN HAS NOTHING ON THESE CONDENSERS If a Walnart Condenser ever let go of more than .00000? it'd probably buckle up with shame. In which event we'd replace it free. Like the Scotch, these condensers are record-holders for "low losses." And, in addition, they stay tight for life. WALNART VARIABLE CONDENSERS are the last place to look for trouble. Plates accurately pressed, aligned and locked to stay in strong slotted studs. Bakelite end plates. Ask your dealer first, please. "Makers of good /=\ goods only" MC MFG. C&. WALNART E Dept. 445 Chicago London Hawaii -JPorto Rica A Canadian amateur (T. A. Crowe, Calgary), operating on three Myers Tubes, heard the concert broadcasted by 2 L.O., London, England, and picked up Hawaii and Porto Rico the same evening. (Calgary Herald, April 1st). Are you getting resulta liko this? You can with Myers TUbes Practically Unbreakable They banish the noise that spoils reception and give wonderful volume and clarity to long-distance messages. Myers Tubes function perfectly as Detectors, Amplifiers and Oscillators. You can't break 'em unless you deliberately try. Two types: Dry Battery and Universal for storage batteries. (4 volts.) Demand Myers Tubes at your dealers or send price and be Sup plied postpaid. See words 'Made in Canada' on each tube. Others UOt guaranteed. Complete with clips ready to mount. No extra equipment re« quired. E.B. Myers Co. Ltd. mdwWacuum v. lubes 240 CRAIG STREET, W. MONTREAL, CANADA «*s