GB624692A - Improvements in or relating to electrical oscillators - Google Patents

Abstract

624,692. Automatic control systems for oscillators. PHILCO RADIO & TELEVISION CORPORATION. Feb. 6, 1946, No. 3710. Convention date, Aug. 31, 1944. [Class 38 (iv)] An oscillator to be stabilized in frequency is given a small periodic frequency variation, and its output is fed to a tuned circuit whose rectified output is applied to correct the frequency of the oscillator. The oscillations from a velocity modulated oscillator 11, Fig. 1, are applied to a resonant cavity 31 whose output is rectified at 33 and applied over amplifiers 45, 51 to series connected diodes 58, 59. A multi-vibrator 35, 36 applies a pulse at high audio-frequency to the repelling electrode 15 of oscillator 11 to produce periodic variations in frequency. If the cavity has a characteristic 34, Fig. 2, and the oscillator 11 is producing a frequency fl, the pulse 64 applied to the repeller 15 produces a change of frequency causing a variation of amplitude corresponding to a negative pulse 65 to appear at 33 ; if the oscillator is producing frequency f2, the pulse 66 from the multi-vibrator produces a variation of amplitude corresponding to a positive pulse 67 at 33 ; while if the frequency of oscillator 11 is at fo, the pulse from multi-vibrator 35, 36 produces a variation of amplitude corresponding to a negligible pulse at 33. The series diodes 58, 59 pass the pulses to appropriate charge condenser 63 to vary the impedance of valve 24 and thus the potential of tapping 21 determining the potential of repeller 15, and thus maintaining the frequency of oscillator 11 at the resonant frequency of the cavity 31.