GB469628A - Short-wave television transmitter - Google Patents

Abstract

469,628. Valve amplifying and modulating circuits. RADIOAKT.-GES. D. S. LOEWE. April 27, 1936, No. 11910. Convention date, April 30, 1935. [Class 40 (v)] In a short-wave television transmitter, dynamic earthing of the valve grids or cathode is effected through resonant circuits including an inductance and a capacity in series, the modulating impulses bias, or heating current being applied through a resistance or choke to eliminate high-frequency reaction. In the arrangement shown in Fig. 1, in which the invention is applied to a modulating valve 1, e.g. of the frequency-doubling type described in Specification 435,561, associated with a quartz oscillator or similar exciter 6, the picture and synchronizing signals derived from generators 10, 11 respectively are applied through chokes 18, 19 to the grids 8, 9, which are earthed through two resonant circuits 14, 16 and 15, 17. The condensers 14, 15 are variable so as to permit readjustment when the carrier wave frequency is altered, a grid bias battery 22 preferably maintains the grid 9 at a higher potential than the grid 8, but, in order to permit the employment of a signal of less amplitude from the generator 11, the latter may be connected to an additional grid inserted between the anode and grid 9 and maintained at cathode potential. In a modification, Fig. 2, showing the last valve 23 of a transmitter, the directly heated cathode 25 is earthed through resonant circuits 26, 27, the inductances 26 being divided and the capacities 27 being connected at the point of division, while the cathode 25 and battery 29 are connected to the opposite ends of the inductances.