Radio Digest (Oct 1923-July 1924)

February 2, 192Jf RADIO DIGEST — Illustrated How and Why of Super-Heterodyne Receive Chapter III— Oscillator Construction Details AFTER the long wave or super-audible transformers have been constructed i-and the fan understands the reason for their employment In this receiver in preference to the average Radio frequency or even audio frequency transformer, the explanation of the oscillator is considerably simplified. Let us assume that the super-audible transformers give maximum efficiency at a wave length of 10,000 meters, which is the same as saying at a frequency of 30,000 cycles. The broadcasting range 0 ONE REQ.D.%, PANEL STOCK By H. J. Marx % tnim -o <S HOLES 3/lb'' (}) 0 (b (b cb d> M" 9" | 9" | 9" I 9 | 9" I 11" TzT~i~e^i*'K'*r-fe-*r ft"*""" is~*n2' . 3f T -* 1" (D THREE REQ.D. % PANEL ST r>i«0 c ■\ c >l OlTT \ ' 2 HOLES 3/ig" s ^ J , -2 that is to be covered runs from 200 to 600 meters (1,500,000 to 600,000 cycles). Then the range of the oscillator should be from 470,000 cycles (500,000 — 30,000) to 1,530,000 cycles (1,500,000 + 30,000). This means that the oscillator circuit must tune from 196 to 638 meters. The idea is that we must synchronize the two frequencies so that we. impress the one frequency on the other at certain beats. It is these beat values that carry the fluctuations which (D TWO REQ.D.-BRASS >\y^9mf^\ are rectified in the second detector after having been amplified in the super-audible stages. It is obvious that, when tuning, any close wave length which would otherwise interfere with reception, would not synchronize with the beats, and is therefore eliminated. As may be expected, the oscillator tuning is controlled by the variable con gETTER Tuning with BREMER-TULLY VERNIER TUNER Says N.T.BRADFORD Terra Bella, California, Jan. 3rd, 1924. "I assembled your No. 2 with two stage amplifier at an expenditure of two hours' time, including the amplifier. Since that time my Neutrodyne has been laid away and all our Radio receiving has been by way of B. T. No. 2. The tones are the best of any set I ever operated." Says GEO. COLMAN 909 N. Kedvale Ave., Chicago, Jan. 9, 1924. "I saw in the Daily News Saturday an article about Minor's Superdyne being able to pull in Elgin through WJAZ. Just want to let you know that with your No. 2 hook-up I have just now pulled in Elgin, Cincinnati, Cleveland, and Pittsburgh with both KYW and WMAQ going strong and can do it every time, as well as get almost anything else I want." Better Tuning Tells you why — shows you how. Sent on receipt of ten cents — packed free with each tuner. Better Tuning B-T Price 10c BREMER-TULLY MFG. CO. S32 South Canal Street CHICAGO denser which should be of the best quality obtainable. The lower the losses and resistance of this condenser, the more selective are the tuning qualities of the superheterodyne circuit. If the oscillator does not cover the tuning range required, the circuit will not function. Then, again, the oscillator circuit parts must be so designed as to permit free oscillation of the tube. Improper design will be manifested by the fact that the tube will not oscillate. Super-Vernier Rheostat Gets 'em All Gets 'em Clearly "MICROSTAT" is in a class by itself as a precision instrument for the perfect control of the filament current in detector tubes, and everyone knows that you must control this current to the finest degree if you are going to get the ultimate from any set — "MICROSTAT" does all this. Built on an entirely new principle. Two windings in parallel — one 6 ohm — other 40 ohm. Absolutely noiseless— infinite control — handles any tube. Capacity 3 Ampere Bakelite moulded — silver etched dial. Do not install a Rheostat until you know all about the "MICROSTAT." Our Bulletin No. 92 explains it in detail. Send for it. It's FREE. fotmltr fyttlrif fampany 3810 Ravenswood Ave. $3.00 — and worth it Ask your dealer for "MICROSTAT" — and get it CHICAGO Oscillator Coils All the points discussed have been carefully considered in the design. The parts have been carefully detailed so that they can be assembled by any fan with a little mechanical ability. The special inductances are again used because of their high efficiency and low cost. The values and sizes given vary slightly from the standard form but these sizes will undoubtedly be placed on the market soon. Fans can easily wind these forms Radio Apparatus Favored and demanded by "those who know" in Radio New "Regal" No. 162 Double Arm Inductance Switch A IS Point Switch complete in one unit. No more messy soldering. No more drilling of holes. No more chipped panels. Complete with hard rubber Knob and Dial. $1.50 New "Regal" No. 120 Vernier Rheostat For fine filament control of tubes, and superfine tuning, the Regal Vernier stands alone. Nothing just like it on the market. Complete with Knob 6-ohms $1.25 30-ohms 1.25 New "Regal" No. 200 Audio Frequency Amplifying Transformer For clearness of tone, amplification of voice and music from nearby and distant broadcasting stations, is unecjualed by any Transformer on the market. 3'A to 1 Ratio. 5 to 1 Ratio. .$4.25 . 4.50 At your dealer's — otherwise write tor our folder No. 25 showing complete lino of Regal Radio Products AMERICAN SPECIALTY CO. 115-220 Holland Ave., Bridgeport, Conn. themselves. It Is only necessary to cut a wooden rod to the diameter required, and use the size studs indicated for the two sizes of colls required. The wire is wound from one side to the other, always , (?) ONE REQ.D -BRASS 3 HOLE ^-f l/ro'STUO **-e •1 16 16^ "v-M •P" goin^ over two studs on each side. About 15 studs (odd number) are required. Oscillator Farts All the parts have been carefully detailed and numbered. Number 1 Is the top (Continued on page 26) RADIO CABINETS Direct from manufacturers. Excellently finished In genuine Mahogany and Oak. 7 X 7 X 9. 7 X 7 X 10. 7 X 7 X 12. 7 X 7 X 14. 7 X 7 X 18. .$2.85 . 2.95 . 3.05 . 3.25 . 3.40 7 X 7 X 21 $3.50 7 X 7 X 24 3.85 7 X 7 X 26 4.10 7 X 7 X 28 4.39 POSTPAID IN U. S. No Strongly constructed with grooves for panels, fasteners or screws needed. Cash with order. Sizes denote size of panels required to fit in grooves of cabinet. Base Boards up to 18 inch, 25o extra; over 18 Inch and up to 28 Inch, 40o extra. D. SUMNER 237 South Market Street, Dept. 21, Chicago 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. PERFECT CONNECTIONS are always sure with Fahnestock Patent Wire Terminal Grips like a Vise Eliminates Vibrations Easily Attached. No Soldering Best of All for RADIO OUTFITS .No. 46 Made in all Sizes and Shapes At your Dealer's Fahnestock Electric Co., Long Island City, N. Y. Dealers can obtain Fahnestock Products from following distributors: BOSTON Wetmore-Savag'e Co. F. D. Pitts Co. DETROIT Detroit Electric Co. CHICAGO Barawik Co. MILWAUKEE Julius Andrae & Sons Co. PHILADELPHIA H. C. Roberts Flee. Supply Co. PITTSBURGH Luduick, Hummel Co. WESTERN DISTRIBUTORS Marshall & Co.. Los Angeles, Cal.