Crystal oscillators and their application to radio transmitter control

The paper discusses the mechanism of operation of crystal oscillators, with particular reference to the frequency stability obtainable. The quartz crystal unit is described with special regard to the temperature performance obtainable from the various cuts used to cover a frequency range on fundamental modes of 4¿20 000 kc/s, and some drivecircuit analysis necessary for the establishment of stability criteria is given. Although it is not desirable to lay down hard and fast rules for design, a chart is included which gives an indication of the type of crystal and drive circuit required for given conditions of stability, frequency, and temperature range. Finally, examples of practical designs are quoted giving long-and short-period stabilities ranging from 30 × 10¿6 to 1 × 10¿8.