GB425308A - Improvements in alternating current oscillatory circuits - Google Patents

Abstract

425,308. Valve generating circuits. RYALL, L. E., 52, Crescent Gardens, Eastcote, Ruislip, Middlesex. Sept. 7, 1933, No. 24795. [Class 40 (v)] The degree of oscillation of a thermionic oscillator of the back - coupled type is controlled by rectified output voltage. The Figure shows a back coupled oscillator 1 in which the feed-back to the grid circuit is taken from a potentiometer comprised by resistance 4 and the anode cathode impedance of an auxiliary valve 5 the grid bias of which is varied by rectified signal voltage from transformer 12. The tuned circuit 9, 10, and series resistance 11 are shunted across the oscillator output, the former being tuned to the signal frequency. By virtue of this rejector circuit there is no transfer of energy to the transformer 12 at the fundamental frequency and when harmonics are produced, such as by the action of the gas discharge amplitude limiter 15, corresponding variation of the impedance of valve 5 acts so as to reduce the feed back voltage of the oscillator 1. In a modification, (Fig. 2, not shown), the impedance valve 5 is shunted by a parallel tuned circuit tuned to the oscillation frequency. Modulation of the oscillator may be effected by injecting modulating potentials in series with a polarizing voltage in series with the discharge tube 15 or alternatively in the grid circuit of the valve 5.