Radio today (Sept 1935-Dec 1936)

TUBE TESTER RELIABILITY AT LOW COST A new emission type Tube Tester that tests all metal and glass-metal tubes. Features: Double Grid Cap for Metal and glassmetal tubes. Shadow-type A.C. meter for adjusting line voltage. Leakage and short test. Tubes tested under load. But four simple operations required. Handsome portable quartered oak case with all-metal panel having silvered letters on black background. Especially constructed against obsolescence. Model 430 complete with Triplett instrument having direct reading GOODBAD scale, protected against C <| Q AA damag \et Denier Price. $14.40 Model 431 — same as Model 430, except has Readrite direct reading GOODBAD meter. Dealer's Net Price Readrite also manufacture all types of testers used for servicing radio sets, including: Set Testers, Tube Testers, Resistance, Continuity and Capacity Testers, Point-to-Point Testers and inexpensive Indicating Meters. SEE YOUR JOBBER MAIL COUPON NOW 1 READRITE METER WORKS, Dent. RT 11, [Hull ton. Ohio. I Please send me more information — | Model 430 Model 431 | Catalogue Name Address City State SERVICING — RIDER Of course, such change is necessary in order to realize upon the high fidelity transmission, providing that proper sideband transfer is secured in the system ahead of the i-f. amplifier. Stagger i-f. stages Speaking about the i-f. amplifier, the simplest method of adapting the system to increased sideband transfer, is by staggering the stages. A compromise adjustment can be reached which will provide sufficient band pass so as to enable realization of the increased sidebands in high fidelity transmission, yet not interfere with adjacent channel selectivity over the normal band. This is not guaranteed, but can be accomplished under favorable conditions. The insertion of additional switches to control series resistors in the secondary circuits to increase band width at a sacrifice in amplification greater than that caused by staggering, complicates matters too much. Excessive staggering should not be used, as it is a fixed adjustment and cannot be changed at will or with great ease, to suit changing conditions. At best, staggering reduces the gain in the i-f. amplifier. Hence the degree of staggering used, must be a compromise hetween maximum gain consistent with the required band width. At no time should the staggering be increased beyond the capabilities of the audio system. As a rule, this means about 5,000 to 7,000 cycles, each side of the peak frequency. To get true fidelity reception the audio system will have to be modified or replaced. Replacement of the audio channel with one of greater response requires that the speaker, too, be changed. Such changes cost money. . . . Too much money! As a matter of fact — now that the method of revision has been described — we do not think that many such jobs will pay. . . . Not unless the owner of his receiver is in love with the woodwork on his present cabinet. SERVICE NOTES Visual alignment *■ As each day passes there is more justification for reference to visual alignment with the carthode-ray oscillograph. . . . More and more of these oscillograph units are being sold, as is evidenced by communications received requesting certain kinds of special data. One of the important items to remember when the cathode-ray oscillo graph is used to align the i-f. system, stage by stage, is the possibility of an assymetrical response curve, due to regeneration introduced when the signal generator is connected to some part of the i-f. system, other than the input circuit of the mixer tube. The leads between the generator and the i-f. transformers may feed some of the energy from the input to the output circuits and thus vary the amount of regeneration in the circuit. . . . 26 Radio Today