Seven-League Oscillator

A bridge-type RC oscillator is described which is continuously adjustable over a frequency range of 20 cps to 3 mc in one sweep of a two-gang linear potentiometer control. Tracking requirements of the two-gang control are not severe. The output is available in four phases, and the frequency is an approximately logarithmic function of the linear potentiometer setting. Practical limits of the frequency range are tentatively 0.01 cps and 10 mc. Accuracy of setting of the order of one per cent is attainable with ordinary components. Frequency stability is of the order of 2 per cent per db of tube gain variation.