Stability in High-Frequency Oscillators

This paper discusses frequency stability with change in plate voltage of high-frequency oscillators of around 100 megacycles and shows both theoretically and experimentally that the highest stability found by many is only the result of fortuitous circuit adjustment that may readily lead to the desired result in this frequency range. It is shown that the factor next in importance in producing frequency stability is a low ratio of inductance to capacitance in the frequency-determining circuit. It is also shown that a high Q contributes little directly to stability. A high Q is necessary with low L/C ratios to get oscillations but an improvement in Q alone may give poorer stability. To get the fullest measure of stability with low L/C and high Q calls for slight adjustments in the circuit and possibly the provision of loose coupling to the frequency-determining circuit.