Radio broadcast .. (1922-30)

48-2 RADIO BROADCAST ADVERTISER TONE Full, sweet, mellow and natural, without the slightest indication of distortion, is another achievement that is making the APEX SUPER FIVE the most popular of all receiving sets. VOLUME That supplies dance music or entertainment without any loss, is a feature forwhich the APEX SUPER FIVE is world famed. DISTANCE Lends added enjoyment to radio with an indescribable fascination of tuning-in far away stations, which is always possible with the APEX SUPER FIVE. Ask your dealer for a demonstration. Your eyes and your ears will tell you that APEX stands at the high point of perfection in both performance and appearance. $80 without accessories. SUPERS APEX ELECTRIC MFG. CO. 1410 W. 59th Street Dept. 204 CHICAGO THE GRID A Department Devoted to Solving the Problems of our Readers QUERIES ANSWERED 1. WHAT is MEANT BY "TUNING"? F. B. F. — Topeka, Kansas. 2. THE CONTROL OF REGENERATION IN MY RECEIVER IS NOT SATISFACTORY. WHAT CAN I DO TO IMPROVE IT? E. W. P. — Chicago, Illinois. AN EXPLANATION OF TUNING IN A circuit consisting of inductance and capacity (coil and condenser), it is possible to alter the value in meters of this circuit by variations in value of either the inductance or capacity. If a generator of an alternating current is connected with a coil and a variable condenser, Generator Condenser A.C.MeJer 3. Is THE USE OF AN OUTPUT TRANSFORMER, FOR A LOUD SPEAKER, OF ANY BENEFIT IN OBTAINING GOOD QUALITY SIGNALS? A. C. B.— Gloucester, Massachusetts. 4. HOW IS A C BATTERY USED IN A DETECTOR CIRCUIT TO OBTAIN RECTIFICATION? T. C. — Newark, New Jersey. change over to another station transmitting at a different frequency (wavelength) it is only necessary to re-adjust the receiving condenser C.2 until the circuit is in resonance with the new signal. As was previously stated, variation in value of a circuit may also be obtained by varying the inductance value of the coil. This may be done by a switch tap arrangement as in Fig. 3 A, or by the variometer method in B. The switch-taps allow the use of more or less of the coil turns which, at its best is only a rough control. In the variometer arrangement, the total inductance value is governed by the Coil coupling of the fields of the two parts of the coil. They are wound so that when at right angles to each other the fields oppose each other and the inductance value is low. When parallel, FIG. I then by varying this condenser it is possible, by noting the maximum deflection of a meter which is in the circuit, as in Fig. i, to arrive at a setting of the condenser where the coil-condenser part of the circuit will be resonant with the frequency of the current set up by the generator. We now have a new term "resonant" or "resonance," and as defined by Hogan this means "Agreement or harmony in frequency: the condition under which the natural frequency of an oscillating circuit equals the frequency of an applied alternating electromotive force." In the circuit A, Fig. 2, we have a frequency generator whose frequency can be varied by the variable condenser Ci. Now, to bring the circuit B in "resonance," or "tuned" to A, it is necessary to rotate the condenser Ca until maximum deflection is noted on the meter. Any change in the adjustment of the frequency of the generator will necessitate an adjustment for the circuit B. Now suppose, instead of the generator circuit A, a signal from a broadcasting station is substituted. Since broadcasting stations are as Variometei \ Fixed Condenser (Air) the fields aid value is high. B FIG. 3 each other and the inductance Frequency Generator Circuit A HOW TO OBTAIN BETTER REGENERATION W t i FIG. 2 signed to a definite frequency (wavelength), then it is possible to adjust the circuit B, or "tune it," by means of the condenser C2, until it is in resonance with the transmitted wave. To f Tested and approved by RADIO BROADCAST ~4r HEN a receiver of the regenerative type goes into oscillation with a "plop" instead of gradually doing so, as the tickler coupling is increased, it is impossible to tune-in distant stations satisfactorily and steps should be taken to rectify this condition. Often smoother oscillation can be obtained by decreasing the B battery voltage applied to the detector tube plate, but when this does not alter conditions, it is then necessary to employ other means for obtaining the desired results. If the tickler coil produces regeneration, then by reducing the number of turns on this coil, one at a time, a point may be reached where, upon advancing the tickler, there is an even, smooth, production of oscillation.