GB637292A - Improvements in vacuum tube oscillation generators - Google Patents

Abstract

637,292. Valve generating circuits. SOC. ANON DE TELECOMMUNICATIONS. Nov. 6, 1945, No. 29588. Convention date, Dec. 16, 1942. [Class 40 (vi)] A thermionic valve oscillator comprises amplitude limiting means connected in parallel with the tuned circuit which is associated with the valve, and a circuit including an element whose impedance increases with frequency is connected between a point on the inductance of the tuned circuit and an input electrode of the valve to provide negative feed-back. Fig. 2 shows a circuit in which, it is stated, oscillations are produced and negative feed-back is provided by means of inductance 7 and resistance 8 which are connected between the inductance of the oscillating circuit 3, 3<1>, 4 and the valve cathode via the earth contact. The metal rectifying elements 6, 6<1> limit the amplitude of the oscillations in the oscillating circuit and the tendency for harmonics to be produced by these elements is countered by the effect of the negative feed-back circuit due to the increase of impedance of this circuit with frequency. A saturated core inductance may be used in the negative feed-back circuit to produce the same effect. A similar circuit is described in which an additional valve is employed, the connections between the grid and cathode of the first valve and the tuned circuit being reversed to compensate for the phase reversal introduced by the second valve. The Specification as open to inspection under Sect. 91 also describes the use of a tungsten filament lamp for amplitude limiting purposes, and several alternative positions of the amplitude limiting element are shown. This subject-matter does not appear in the Specification as accepted.