Radio Digest (Apr 1925-Jan 1926)

18 RADIO DIGES T— Illustrated June 6, 1925 TUNED R.F. ADVANCES (Continued from page IT) mately the same gauge and of equal insulation. The major portion of such transformers keep this ratio as high as possible, the average being close to 1 to 10 while the general practice is to insert the primary inside of the form holding the secondary and to maintain a spacing of about one-quarter inch between turns of the primary. In the construction of the radio frequency transformers for some of the circuits which I will show, two very radical departures from this usual method Trill be shown and the logical reason given for each method used; not with the intention of joining the army of "low lossers" as a buck private, but rather with hopes of attempting to advance the science instead of wrecking it with purely mechanical tricks in place of electrical goodness. Am I in favor of low loss? Never! Merely as a name, but what I am in favor of is maximum power factor, almost a new word in Radio, and I want this power factor high in the completed receiver, rather than concentrating on one spot and loosing it in the next. Possibly I should not call spades spades, but rather use the more generic term shovels; however, low losses result in the very result our leading engineers are working night and day upon and, having faith in their ability to solve the problem, let us then look to them for our greater success rather than to the clever mechanic. Primary to Secondary Ratio Turn ratio, or the step up ratio factor, in radio frequency transformers, in so far as believing that "the greater the ratio the greater the energy transference" has been proven as erroneous. By way of illustration, if we have six turns in the primary winding and fifty-four in the secondary winding of a solenoid type of radio frequency transformer, our turns ratio would be high, one to nine, yet our transfer or inductance value would be comparatively low. To the contrary, should we increase the number of turns to say eighteen or a step up ratio of 1 to 3, equal to a third of our former value, the amplitude of inductance transfer from primary to secondary would be at approximate maximum. Hence, ratios, of themselves, are but relative terms and apparently have been considered too carelessly by many "low lossers." Not all, by any means, as in some circuit designs and, in partciular, antenna input design, turns ratio efficiency with regard to its inductance transference, is obviously and essentially high. The "Goode" Two-o-One A Le Ton d'argent BY MAIL ONLY 1 .89 Postpaid QUARTER AMPERE AMPLIFIER — DETECTOR RADIO TUBE GUARANTEED SATISFACTORY All "GOODE" Tubes Sold Direct to the Consumer — No Dealer Profits $1.89 5.00 ONE — "Goode" Detect orAmplifier THREE — "Goode" Detect orAmplifier b (All postftge preptld) The "Goode" Two-o-One A Tube imputes or de lactt. II I a fjuarter ampere, t?e rolti, standard baie atlvered tube. Send express or postal money order — New York draft — rjr personal check to — The Goode Tube Corporation Incorporated Owensboro (Dept. A) Kentucky While this factor is equally true in interstage coupling upon some types of circuits, however, in general as we increase the turns ratio between primary and secondary we decrease the tendency toward creating sustained oscillations and, in direct proportion, increase the inductance transfer factor. Therefore, unless one is prepared to determine the compromise his limitations command it is best that he look upon all few turn primary, or high ratio radio frequency transformers, as devices which will tax his ingenuity toward control unless his circuit design definitely prompts their use. Mechanical Construction Another feature of radio frequency design common to many makes on the market for which there appears no logical reason, and which but meant additional cost to the manufacturers, and infinitely hard construction to the home builder, is the practice of placing the primary windings within or upon the inside of the tube or secondary winding. As I write this, I have before me a radio frequency transformer so arranged as to mechanical arrangement of the entire coil that it shows clearly the maximum of mechanical ingenuity in its design and particularly, extreme cleverness and elaborate preparation for the placing of the primary inside the solenoid. "With its secondary winding, it would be easily possible to present it as the finest mechanical effort in coil construction that I have seen, yet I cannot recommend it because the primary is too close to the center of the coil's magnetic field, which is another way of impressing upon you another danger point. Obviously, the ideal position would be outside of the secondary and as much out of its magnetic field as possible without destroying its inductive relation value. Therefore, in the radio frequency transformer which I shall describe later, an attempt will be made to picturize and describe a nearly standard radio frequency transformer as representing the present advanced state of the science. (How primary cells — commonly known as all batteries other than storage — generate electricity — is Professor Moreton's next subject. The chemical actions are simply explained. — Editor's Note.) 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