High frequency oscillator stabilization by pulse counting techniques

A crystal oscillator source at 5 Mc/s provides reference frequencies at 1 Mc/s and 1 kc/s, the latter providing a pulse chain output. Two LC oscillators are controlled by a ganged two decade switch. One oscillator is pulse locked to the 1 Mc/s reference, producing frequencies at 1 Mc/s intervals from 3¿31 Mc/s. The second oscillator, on the same switch position, can be continuously tuned over 1 Mc/s range, the frequency at the high end of the range being equal to that of the pulse-locked oscillator. These two frequencies are mixed, the output appearing in a band-pass filter of range 1 kc/s¿1 Mc/s. This output frequency is fed to a Trochotron divider which can be set to divide by an integer between 1 and 1000 by operating a set of three decade switches. The output will be 1 kc/s if the oscillator is on frequency. The 1 kc/s output pulse train from the divider is compared with that from the standard in a sine wave phase comparator circuit and the error voltage used to lock the variable oscillator via a reactance valve.