GB560780A - Improvements in or relating to thermionic oscillation generators - Google Patents

Abstract

560,780. Valve generating circuits. TELEPHONE MANUFACTURING CO., Ltd., and PADDLE, L. H. Aug. 13,1942, No. 11338. [Class 40 (v)] The frequencydetermining circuit of a valve oscillator is shunted wholly or in part by one or more asymmetric or non-linear resistances, with the object of obtaining stability of frequency and wave-form. As shown, the tuned circuit 3, 4 is associated with the cathode 5 and the first two grids 6, 2 of a pentode valve 1, the grid 2 acting as anode and providing feed-back to the control grid 6. The asymmetric resistances 7 are connected across the respective sections or the whole of the dust-cored coil 3. The third grid 23 is connected to the cathode, and the anode circuit includes a resonant circuit 9 tuned to the operating frequency and transformer-coupled to the load. Bias for the control grid 6 is provided by a condensershunted resistance 27 in the cathode lead. The asymmetric resistances 7 may be single dryplate rectifiers, or pairs of such rectifiers connected in opposition, or any conductor having a non-linear relation between current and applied voltage. In a modification, a condenser is interposed between the sections of the coil 3, its upper plate being connected to high-tension positive, and its lower plate earthed through a condenser-shunted resistance, Fig. 3 (not shown). A rectifier may be interposed between the upper end of the coil 3 and the grid-anode 2 in place of the condenser 29 as in Specification 519,672. In a modification referred to in the Provisional Specification, two valves may be used, the grid of the main output valve being energized from the anode circuit of an auxiliary valve, and the frequencydetermining circuit 3, 4, 7 being situated in the grid circuit of the auxiliary valve and energized by current derived from the main valve output circuit.