GB380144A - Improvements in and relating to thermionic valves and circuits for the generation, modulation and controlling of electric oscillations - Google Patents

Abstract

380,144. Valve generating and modulating circuits. HODGSON, A. D'A., 24, Spenser Road, Bedford. June 30, 1931, No. 31372/30. [Class 40 (v).] A valve generator with two or more grids has a frequency -determining circuit connected between two of the grids, and its output circuit connected between anode and cathode, so that changes in the output circuit do not affect the frequency. As shown in Fig. 2, the frequency-determining circuit 5, 6 is connected between the inner grid 1 and the second grid 2, a third grid 3 acting as a screen and preventing negative-resistance effects. An intermediate point of the coil 5 is connected to the cathode F, and suitable positive voltage is applied to the grid 2 and the anode AN. The output circuit 9, 10 is connected across anode and cathode and is coupled to an aerial or other load circuit. The anode may be connected to a tapping on the coil 9. A neutralizing condenser may be connected between the anode and either of the grids 1, 2 ; or neutralization may be effected by adjustment of the cathode tapping X on the coil 5. The anode current may be given various wave-forms by adjusting the swing of voltage on the grid 2, and multiple frequencies may be obtained in the anode circuit. Modulation may be effected by applying signal voltage to the grid 3, or to the high-tension supply lead for the grid 2. A modulating tone-frequency may be generated by the transmitter valve by back-coupling the anode circuit at 18, Fig. 8, to the circuit of the grid 3, which may include a key 5 and a source of low positive voltage. The tone-frequency may alternatively be generated by back-coupling the tuned-anode circuit 16, 17 to a coil 18<1> in the circuit of the grid 2 as shown in Fig. 9 ; or the coil 18<1> may be tuned.