A Simplified Circuit for Frequency Substandards Employing a New Type of Low-Frequency Zero-Temperature-Coefficient Quartz Crystal

This paper presents a new type of stabilized quartz-controlled oscillator and a new type of low-temperature-coefficient piezoelectric quartz circuit element which, in their combination, are particularly suitable for portable substandards of frequency. The oscillator circuit is simple and may be easily stabilized by two reactance adjustments so that the frequency is unaffected by change of tubes or by small changes in the circuit reactances, the plate voltage, and the ambient temperature. Measured stabilities are given for this circuit when constructed as a substandard of frequency, employing the new CT crystal, and generating one hundred kilocycles and its harmonics. A previously unused type of vibration in quartz plates cut at an angle to the crystalline axes provides low-frequency circuit elements with a wide range of temperature coefficients. Two specified orientations, designated as CT and DT cuts, exhibit zero temperature coefficient at specific temperatures and are closely related to the recent, but now popular, AT and BT high-frequency plates. The new plates are especially useful in precision applications for by slight final adjustment their frequency may be either raised or lowered and their temperature coefficient made either more positive or more negative.