High Accuracy Heterodyne Oscillators

Abstract

The accuracy of a heterodyne oscillator after the low frequency check is made is of the same order of magnitude as that of an ordinary type of oscillator in which circuit elements of the same stability are used. It depends on the constants of the variable frequency oscillator only. This accuracy can be improved by a ratio of 10 to 1 by adding another and higher check frequency. The temperature coefficient of the circuit elements can be kept down to less than 6 parts per million. Scale errors can be reduced to a value comparable with the oscillator accuracy by spreading the scale. A precision oscillator having a frequency range up to 150 kc. and an accuracy of ±25 cycles including a scale mechanism whereby a large scale spread is obtained on a direct reading scale is described.