Radio Digest (July 1924-Apr 1925)

July 19, 1924 RADIO DIGES T— Illustrated 17 Improving the Single-Circuit Tuner Hook-up Suitable for Portable Receiving Set Probably half of the homemade regenerative sets in use all over the country, as well as, thousands of factory built sets, follow a diagram similar to figure 1. This will of course be recognized in WORKSHOP KINKS EARN A DOLLAR— 1 -A HERE are many little kinks worked out at home that would ■ aid your fellow Radio worker if only he knew about them. There are new hook-ups, new ways of making parts and various unique ways of operating sets that are discovered every day. Radio Digest is very much inter ested in obtaining such material. Send them in with full details, including stamped envelope, so rejected copy may be returned. The work must be entirely original, not copied. RADIO KINKS DEPARTMENT, Radio Digest, 510 North Dearborn St., Chicago stantly as the famous single-circuit, which has fallen into disrepute because of its faculty for radiating powerful oscillations and consequent disturbing reception over a radius of several miles. In these days of staggered wave lengths and possibility of picking up many programs at will if one uses a sufficiently selective receiver, the broad tuning of this circuit is almost as much a detriment as its radiating properties; therefore, if wonderful improvement in selectivity can be accomplished at little or no cost and with very little trouble, the information given in this article should interest every fan — regardless of how selfish or careless one may be as to causing interference for his listening neighbor. But the change shown in this article will do more than improve the tuning qualities of a set and remove practically all radiation — it will tremendously increase the "sensitiveness of any set and r CARTER Jack Switch For "A" Battery Circuit The only switch that shows "On or Off." No unreliable sliding contacts. Simple to mount. All connections soldered. Wide spaced solder terminals. Furnished complete with "On and Off" name plate Knob and Pointer. Any dealer can supply. Write for Catalog of other Carter Products. OLD AND IMPROVED CIRCUIT FIG.1 give one a far greater receiving radius than the single-circuit tuner. Referring to Figure 1, CI is the customary tuning condenser; it may be 5, 7, 13, 17, 23, or even 43 plates — whatever the set now has will work O. K., although probably 17 or 23 plates is most desirable. C2 is the usual, grid condenser; and C3 the by-pass condenser, of .001 mfd. capacity, usually. These same values are used on the circuit shown in Figure 2. In fact, the only addition necessary is the coil L.3, which consists of 5, 8, or 10 turns of any size wire from 18 to 28, wound over the old primary coil. . These turns may be spaced % inch or y2 inch apart, and no special care need be taken in choosing the wire size; although either double silk covered or double cotton covered is preferable because of its superior insulation. The variable condenser in the antenna circuit in Figure 1 is connected across the old primary winding, as shown, and provides the tuning element in conjunction with the switch-taps. • "THE ACCENT IS ON SERVICE" 14-16 Vesey St. NEW YORK VARIOCOTJPliERS $3.50 Workrite 180° Silk Wound $2.95 3.50 Fisher. Large. 90° 2.75 2.75 Fisher, 180° 2.25 4.25 Special Bank Wound Coupler for Haynes Circuit (with diagram) 3.25 7.00 Ambassador Coil (with diagram) 5.50 VARIOMETERS $3.50 Workrite $2.95 5.00 Pathe Moulded 2.25 3.50 Fisher, Large 2.85 CONDENSERS $2.00 E. C. 11 plate $1.05 2.25 K. C. 23 plate 1.35 2.75 R. C. 43 plate 1.65 VERNIER CONDENSERS $4.00 K. C. 23 plate $2.25 5.00 K. C. 43 plate 2.95 PHONES $18.00 DR. SEIBT IMPORTED "SUPER tffi Qfl HEADSET" 3>0.»U $12.00 N. & K.. Imported $6.90 The above items are just a few of our numerous attractive priced articles, which are contained in our BULLETIN OF RADIO PARTS. Gladly sent to you upon request. We are headquarters for "Radion" and "Bakelite Dilecto" Panels. The best panel material available. Mail orders promptly attended to. Will ship C. 0. D. unless remittance accompanies order. •Dealers Need This 200% Profit The new FAHNESTOCK Display Case Will stimulate your sales of Fahnestock Radio Products. 14 of the most popular styles and sizes are included. Shows the purchaser instantly the correct piece for his set. A constant invitation to buy Fahnestock Products. Dealers are offered 200% profit on each case, an unusual offer on standard merchandise. Price to Dealer $17.50 West of Mississippi 18.50 Transportation prepaid when money order or check accompanies order. Subsequent orders at regular price of $20.00. Contents Retail for $51.50 Refills will be supplied at the regular 100 lot prices, shown in catalogue, which comes with case, less discount shown on enclosed sheet. Send cheek or money older, today. FAHNESTOCK ELEC. CO. DONG ISLAND CITY NEW YORK FIG..S. By being careful to connect the movable plates of the variable condenser to the ground lead, as shown, practically no hand capacity will be noticeable — even without panel shielding. Another feature of this re-vamped single-circuit tuner is that all stations will tune in on the same secondary dial setting, regardless of the length of the antenna, because the antenna circuit is untuned. If the reader owns a single-circuit tuner, he should not delaj'' a moment in making this simple change; your neighbors will not only thank you, but you will certainly be agreeably surprised. This circuit is especially adaptable to portable sets. — G. S. Corpe, El Monte, Cal. Above all don't buy a pair of cheap ear-phones. The difference between a good and bad pair of phones is usually the equal of one to two stages of amplification. MAGNATRON MAGNATRON DClT1 199 knows no superior among dry cell tubes. Whether as detector or as amplifier, it will give better results in your set. It and the MAGNATRON DC201A are unqualifiedly indorsed by . experts.' Your dealer has these tubes. They list at $5. CONNEU/EY ELECTRiC LABORATOWES 3Q9 Fifth Avenue new YORK CITY PERFECT FILAMENT CONTROL $1.85 At all Dealers for Summer Radio When you want to tune in distant stations, this summer, use the Bradleystat. When you want perfect filament control, use the Bradleystat When summer static is worst, try the Bradleystat. In fact, when you want maximum efficiency from your detector, use Bradleystat perfect filament control and enjoy a new radio treat Try one, this week! Jilectrlc Controlling Apparatus 290 Greenfield Ave., Milwaukee, Wis. Affrs. of the Bradleyleak Dielectric Panel Made From Glass and Paper A neat and an inexpensive panel can be made of two pieces of window glass and a piece of black paper the same size. First shellac one side of the paper and stick it to one of the pieces of glass and then shellac the other side of the paper and lay the other piece on it and clamp them together with clamps until dry and / GLASS PANEL IV / — SHELLACED GLASS ©LACK PAPER PANEL SMALL CLAMPS <AROUN0 PANEL. then it can be drilled with an iron drill using a little oil or turpentine. You now have a panel that is a good dielectric and is neat appearing. The panel can be fastened to the cabinet by the use of brackets. — Lee'H. Bolen, Hamilton, Mont. Make a Good Lead-in Even though the lead-in wire Is insulated, never let it get up against any metal. This means the cornice around the edge of the roof, the metal window screens or weather strip, or any other metal. Even if it is insulated there will be leakage here, and trouble will surely result. It usually manifests itself by constant whistling and inability to clear up a station altogether. Every Question ANSWERED for only $1 At last you have under one cover a Complete Radio Handbook l.c.s. RADIO JUST OUT 514 PAGES Compiled by HARRY F. DART, E.E. Formerly with the Western Electric Co., and U. S. Army Instructor of Radio. Technically edited by F. II. Doane. 50,000 ALREADY SOLD NO more need you turn from book to ►book, hoping to find what you want. It is all here, in 514 pages crammed full of every possible radio detail. Written in plain language, by engineers for laymen. Clears up the mysteries, tells you what you want to know. A complete index puts everything within your reach in a few seconds. IT EXPLAINS: Electrical terms and circuits, antennas, batteries, generators and motors, electron (vacuum) tubes, every receiving hook-up, radio and audio frequency amplification, broadcast and commercial transmitters and receivers, super-regeneration, codes, license rules. Many other features. Under one cover. Yes, it is all in one volume of 514 pages of clear type with hundreds of diagrams and illustrations. Takes the place of eleven or more specialized texts, each costing from two to ten times the dollar you pay for this single book. Belongs in every radioequipped home, on every amateur's table. Send $1 to-day and get this S 14-page l.C.S. Radio Handbook— the biggest value in radio to-day. Money back if not satisfied. r TEAR OUT HERE n I INTERNATIONAL COERESrONDENCE SCHOOLS I f Box S278K, Scranton. Penna. KI enclose One Dollar. Please send me — postpaid— the 514-page I. C. S. Radio Handbook. [ It is understood that if I am not entirely K satisfied I may return this book within fire II days and you will refund my money. ' I iName _ ! ! I Addresi • • !