A New Frequency-Stabilized Oscillator System

A new vacuum-tube self-oscillating system having extraordinary frequency stability is described which depends on the reëntrant circulation of oscillations through tuned filter or coupling units. The reëntrant circulation through the filter sections attenuates all but a single frequency in a manner analogous to the attenuation produced by a filter system having an infinite number of sections. The unattenuated component having a single frequency is amplified at each passage through the system and constitutes the single-frequency oscillation. The methods and necessary precautions for attaining frequency stability are given. Frequency shifts due to ordinary variations of plate potentials, filament current, or keying are found to be of the order of one thousandth of one per cent. The extreme flexibility of the circuits permit the construction of satisfactory radio transmitters operating from the lowest frequencies up to 20,000 kc without the use of frequency-doubling stages. The oscillator system has found wide application in commercial and naval aircraft radio communication problems.