Radio Digest (Oct 1923-July 1924)

RADIO DIGEST — Illustrated April 5, 192U FIXING WHATS WRONG ntinued from page 11) be traced to the lack of tuning experience on the part of the The improper .ipulatior. "ill result in e from any receiver of lerative type. rs of regenerative receivt-C&lled 'heterodyne : note method of recep tions of unknown wave a using this mode of proacuum tubes are thrown into •.. and by adjusting the grid and ontrols at the same time, the circuits are kept in oscillation while the , length is varied over Quite a wide range. With the tubes in an oscillating ■ the receiver circuits will behave as ..tor of Radio energy, some of b will be radiated from the receiving em. The presence of this reinterference is manifested in nearby receivers by whistling noises of varying pitch. It is evident that when ral neighboring regenerative receivers usted simultaneously to the --.ant station, it is practically an ■ ility for any one of them to ree the program from the distant station l satisfactory mam. To acquire the knack of proper tuning :io more effort on the part of the than the highly undesirable method just mentioned. If the antenna am is kept approximately in resonance with the tube circuits, and the incoming i is adequate to give audible s, the broadcasting station may be tuned in by a simultaneous adjustment of i the grid and the plate controls. During this operation, the relative settings of the two control dials should be maintained to such a degree that the circuits are just below the oscillating point. Modulated Signals During the reception of a broadcast program or any other form of modulated signal, it is positively unnecessary to have the vacuum tube in an oscillating condition. Clear, modulated signals cannot be received when the set is in a state of oscillation. The uncalled-for method of throwing the detector tube into oscillation in order to intercept the carrier wave of a distant station, sets up a continuous barrage of reradiation interference. If operators would strive to forego this method of endeavoring to locate stations much of the present interference would be at an end. -While it is, undoubtedly, true that the single circuit receiver, using tickler coil feedback, produces the strongest interference from reradiation, the substitution of a variometer in the plate circuit, instead of the tickler coil, .will aid materially in cutting down this interference. "When using the inductively-coupled types of regenerative receivers, in order to obtain DX signals with sufficient intensity, the coupling must necessarily be close. If under these conditions the set is accidentally thrown into an oscillating state, it will reradiate generously for that amount of energy. In a single circuit set, the initial signal energy applied to the grid of the detector tube is about 25 per cent greater than for a two circuit receiver, with the result that the regeneration does not have to be so far advanced. The fundamental rule to be followed for obtaining best results in tuning is to thoroughly comprehend just what the function of each control is and to manipulate them in a systematic and not in a haphazard manner. A complete understanding of the general operating-principles of the set and its control is essential to getting good results consistently. Operating Single Circuit Receiver Inasmuch as the single circuit regenerative receiver is undoubtedly the most popular type with the Radiophans, it will not be amiss to detail the proper method of tuning such a set. Three controls are generally provided, the wave length control, the regeneration control and the filament rheostat. The filament should be operated at the lowest current which will give satisfactory results. This may be determined by slowly increasing the filament temperature until a hissing sound is heard in the phones and then cutting down the filament current just sufficient to cause this noise to cease. Having the regeneration control set at zero, the wave length or tuning control should be gradually turned until signals are heard. The regeneration control is then slowly adjusted until maximum strength of signal consistent with good quality is obtained. Advancing the feedback control too far will cause the set to oscillate and reradiate interference from the receiving antenna. If the regeneration cannot be controlled the addition of a potentiometer across the filament battery will materially reduce the howling. First, however, it will be advisable to carefully regulate the filament temperature, reduce the plate potential and adjust the feedback control to as near zero as possible. Tuning Inductively-Coupled Receiver In tuning an inductively-coupled regenerative receiver, the filament current should be regulated to a point just below the normal filament brilliancy. The prisnd secondary circuits are then in or adjusted to a condition of nee with the incoming wave. If a tickler coil is employed, the proper amount of regeneration is secured by regulating the coupling between the tickler and secondary coils. If a tuned plate is used, adnent of the plate variometer will furnish the required amount of feedback enorgy. Careful regulation of the filament temperature will bring in the signals loudly and clearly without any howling or distortion. Under stable conditions, the local oscillations are of the same frequency as those radiated from the broadcasting station. If the tuning is varied either way from this state of synchronism, called "zero beat" reception, a high-pitched whistling note will result, the pitch gradually becoming lower until it is replaced by music or speech. Further variation will pro duce a low whistling note, gradually increasing to a shrill sound. Inasmuch as the tuning adjustments for any regenerative outfit are so extremely critical, it will well repay the operator to consider the use of vernier condensers and vernier filament rheostats. This permits of very minute variations in the tuning adjustment of the circuit and in the regulation of filament current. In this manner the point of maximum amplification may be easily found and the resulting reception will be free from any distorting effects. The successful operation of any set depends upon the operator, who should be familiar with the apparatus and always employ critical tuning. The regeneration is easily controlled and with proper manip ulation may be used as an aid in tuning. Radiophans with regenerative receivers can greatly increase interest in the Radio game by endeavoring at all times to do their level best to keep control of their circuits. (TO BE CONTINUED.) Amplification A vacuum tube regenerative set, using only one tube, will bring in signals from nearly the same distance as a set having an audio frequency amplifier. The amplifier only serves to increase the strength of signals brought in by the detector tube, for the purpose of operating a loud speaker or making the signals louder in the phones. ^■.■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■IIIilllillllllliBlillillilliiiiilllllililllllllllllililliSIlilllliilllllllillllilllilillliiiilllllllHIIIiaBIIIilllllllllllllllllll^ I JACK SHACK laV DE LUXE NEUTRODYNE ! EVERY ONE KNOWS THAT THE NEUTRODYNE IS THE BEST SET IN THE WORLD TODAY. No other set compares with it in distance, clearness, volume or sweetness of tone without squeals and howls, PROVIDING YOU USE GENUINE LICENSED PARTS, LICENSED UNDER THE HAZELTINE PATENTS. It has remained for THE RADIO SHACK to bring to you the Neutrodyne DE LUXE, made up of the best obtainable parts and using only GENUINE LICENSED NEUTRODONS AND NEUTROFORMERS. 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THE DE LUXE JUNIOR 3 Genuine Hazeltine Neutroformers, mounted on Condensers 2 Genuine Hazeltine Neutrodons 3 Brass Bushing 4" Dials 1 Full Size Blueprint of Instruction THE DELUXE LIST $24.50 OUR PRICE 16 50 Using COMSCO Condensers SEND NO MONEY WE SHIP C. O. D. ^lAMO' 55 Vesey Street New York City Goods shipped C.O.D. Just pay the postman wwvakW&somon written aij//ey-bmk guaimx& NOTE NEW ADDRESS In order to facilitate deliveries and service, address all mail to our Executive Offices 55 VESEY STREET NEW YORK niiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 1 1 1 1 1 1 1 j ■ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 f=