GB175635A - Improvements in thermionic wireless transmitters - Google Patents

Abstract

175,635. Ges. f³r Drahtlose Telegraphie. Feb. 16, 1921, [Convention date]. Thermionic modulating systems.-In a wireless transmitter employing a thermionic valve with two grids, the anode feed current and the potential of the space-charge grid are influenced simultaneously by the speech current through separate circuits, and the space-charge grid may be kept at the same potential as the anode. The anode is shown as connected to a positive main, which may be 110 volts above the negative main and the filament F. The grid G is connected as shown to the oscillatory circuit O, for the purpose of generating oscillations. Modulation is effected by the variations of potential applied to the anode A by secondary S of a transformer, the primary P of which carries a current induced by the microphone M through the transformer T1, T2. To prevent the steady component of the current in the circuit P, T2, from magnetizing the covers of the transformers, compensating windings C, T3' are provided and the current therein is adjusted by means of a variable resistance W2. In order that the space-charge grid R may be always at the same potential as the anode A, it is connected to an adjustable point in a resistance W1 which carries the telephone current.