2YA To Go On Test

Radio Record, Volume II, Issue 24, 28 December 1928, Page 7

2YA To Go On Test

Crystal Control v. Master Oscillator OR some considerable time station . 2YA, Wellington, has been erystal controlled, as are many of the foreign stations, but results have not been what they might have, and the tests. should reveal whether it is the erystal that is at fault or not. : A erystal-controlled transmitter consists of a valve oscillator controlled by a piezo-electric crystal, a radio frequency amplifier, and in some cases a frequency multipliér. Owing to the fact that the oscillations generated in a crystal-controlled circuit, while re-

>. Pasa emeonanmenio et snc t TST aeenieatrintlaat oF markably selective and’ constant, are nevertheless very feeble, it is necessary that, the energy should be amplified many times before it can be useil for practical purposes in the transmitting plant. "A Crystals for this purpose must in the first place be clear and flawless, and then cut to a definite size. The size determines the wave-length, and unless the crystal is replaced the wavelength cannot be altered. Thus, "broad tuning," "off the wave-length,’ and similar complaints are impossible. The crystal is mounted in the circuit by being placed between two conductors and so placed in the circuit. Diagram I shows the erystal mounted as it is at 2yA-the bone of contention. With the master oscillator control, however, wave-length ean vary by very minor alterations. There is little difference in the circuit except for the provision of another valve instead of the crystal, and a .lesser, amount of amplification. This latter type is still that used in most of the big stations of the world, and certainly with careful adjustment and handling can give results well nigh perfect. Diagram 2 is the master oscillator aoe