Quartz - crystal frequency standards

A brief history of the development of high-precision quartz-crystal oscillators is followed by a discussion of crystal characteristics, including Q factor, frequency ageing, and frequency drive characteristics. A graph is given which shows the effect of cooling and reheating on a 5 Mc/s fifth-overtone AT-cut crystal unit. Various types of quartz crystal resonators that have been evolved are then outlined: these are the Marrison Y-cut ring, the GT-cut plate, Y-cut bars, the Essen ring, and AT-cut resonators. Performance figures of these crystal units are tabulated. Methods of temperature control are described, and the development of high-precision frequency standards is briefly reported. An application of a high-stability crystal-oscillator in a communication system is mentioned. Finally, atomic and molecular frequency standards are discussed. References to 24 other papers dealing with crystal resonators and their applications are given.