Radio Digest (Oct 1923-July 1924)

February 9, 192k RADIO DIGEST — Illustrated Reflexing Four-Tube Neutrodyne Receiver Inserting a Crystal in the Popular Circuit By H. J. Marx THERE have been a number of efforts to discredit the possibility of using the reflex type of circuit in conjunction with the neutrodyne principle. No real reason exists, however, why the neutrodyne circuit should not be reflexad, and this without loss of efficiency but retaining the gain accruing from the elimination of one tube. More Volume A number of fans have stated that they would like a little more volume from their five-tube neutrodynes. This article is primarily intended to detail the changes necessary for reflexing one stage of the audio freq\iency and then using the fifth tube for. an additional stage of audio frequency amplification. FAHNESTOCK'S LATEST RADIO HELP No. 31 The Antenna Connector Price 10c Snap larger connector over Antenna Wire; insert Lead-in Wire into smaller clip and a perfect connection is the result. IMPROVED GROUND CLAMP Equipped with Fahnestock Patent Wire Connectors Easily Attached No Soldering — For Radio Use Only FAHNESTOCK ELEC. CO. Long Island City, N. Y. Dealers can obtain Fahnestock Products from following distributors: Special New York distributors SPARTAN ELEC. CORP. BOSTON Wetmore-Savage Co. F. D. Pitts Co. DETROIT Detroit Electric Co. CHICAGO Barawik Co. MILWAUKEE Julius Andrae & Sons Co. PHILADELPHIA H. C. Roberts Elec. Supply Co. PITTSBURGH Ludn i< k, Hommel Co. WESTERN DISTRIBUTORS Marshall & Co., Los Angeles, Cal. The additional parts required are one audio frequency transformer and a few by-pass condensers. Jacks can be added if desired. Naturally, if only one stage is reflected, the fan will have no trouble in construct'on and operation. It is only when two stages are reflexed that we meet the more serious problems of tube efficiency, proper by-pass condenser values, interference in leads, oscillation control of the tubes, and the ratios of the transformers. Few fans have had trouble with single-tube reflex circuits; it's the multi-tube reflexes that cause the gray hairs. Making' Change on rive-Tube Set In making the change on a five-tube set, the lead between the plate of the second B+OET. B+AMP. tube and the third neutroformer is opened and the primary of the extra audio transformer is connected in series, with a .002 condenser across it. The secondary of this transformer is connected to the grid and filament of the fourth tube. The secondary of the audio transformer, after the detector tube, is coniiected in series with the grid return of the secondary of the second neutroformer. A by-pass condenser is then added from the neutroformer filament terminal to the negative battery lead. This then completes the alterations for reflexing one stage. Four Tube Set For those fans who want a four-tube set the last tube can be eliminated. This gives a very efficient receiver that meas $ 3/4 Actual Size PREMIER AUDIO-FREQUENCY TRANSFORMER 3CAThe wonder of the £^Radio world. A more ""efficient transformer than you could ever buy before. And the smallest, most compact instrument of its kind. About the size of an English walnut and yet "HEGEHOG" is a wizard for reproduction value, tone quality and consistent performance. Less distortion. No foreign noises. The secret is in its patented construction. It is shielded 100%. Fully guaranteed. Ratios 1 to 3, 1 to 4, 1 to 5, $3.50; 1 to 10, $4.50. You'll want "HEGEHOG" in your next "hook-up," so get all the facts NOW. Our Free Bulletin No. 92 gives them fully. Send for it. Ask for and insist on "HEGEHOG" at your dealer's. \>rrmWr fyrtirlt fompuny 3«10 Ravenswood Ave. CHICAGO well with any five-tub'; Heavy Wire Used In ' turn of i RADECO Safety Fuses Are protecting countless Radio Tubes DEALERS Add this profitable sales maker to your line and make satisfied customers. If you are not handling this fast selling specialty write us at once. Radio Equipment Go. New England's Oldest Exclusive Kadio House 20 Stuart St. BOSTON, MASS. Try This New One If You Want Efficiency PFANSTIEHL COMBINED GRID LEAK & CONDENSED. 2 MEG FOR UV 200 -i3 MEG F0RUV201A 3 MEG FOR UV 199 / PFANSTIEHL TUNING UNIT "•HNSIDE Try this newest efficiency hook-up, using the Pfanstiehl Tuning Unit PFANSTIEHL RADIO SERVICE CO. Highland Park, 111. Bring your set up-to-date Switch points have passed out of date. They are uncertain and unsatisfactory. Walnart Inductance Switch 1-10 points, permits of better soldering and insures positive contact. Only one hole to drill. Simply and quickly installed. ASK YOUR DEALER Catalog of complete line of Walnart parts on request WALNART El|te)?fC MFC C&. 1249 W. Van Buren St., Dept. 421 CHICAGO In Canada: WRIGHT RADIO CO., Overbrook, Ottawa, Canada, Canadian Distributor $1.25 WITH DIAL The base of this instrument is Con densite CeloroS, the perfect dielectric insulation (licensed under B i k e I i t e patents). j