GB421013A - Improvements in or relating to modulated high frequency transmitters - Google Patents

Abstract

421,013. Valve generating circuits. TELEFUNKEN GES. FUR DRAHTLOSE TELEGRAPHIE, 12, Hallesches Ufer, Berlin. Nov. 1, 1933, No. 30406. Convention date, Nov. 1, 1932. [Class 40 (v)] Distortion in a modulated carrier-wave transmitter is compensated by rectifying voltages derived from the modulated output and applying these voltages, which comprise a distorted form of the original modulating voltages, to oppose the modulating voltages. The invention is described with reference to amplitude modulation. In one arrangement, Fig. 1, which provides only partial compensation, the output of a modulating valve 1, having its grid-filament circuit connected to a high frequency source HF and a modulating source 3, is rectified by a diode 2 and the resultant fluctuating voltages across resistance R form part of the bias applied to valve 1. This arrangement may also be applied between the output and input of the oscillator and modulator valves respectively in an anode choke-modulated transmitter, Fig. 2 (not shown). In the modification shown in Fig. 3, the distorted modulated output from valve 1 is amplified by a non-linear amplifier HFA before rectification at 2. In the further modification shown in Fig. 5, the rectified output of 2 is connected across a diagonal of bridge 9 and the modulating voltages from 3, besides being applied as usual to the valve 1 are applied across the other diagonal. Distortion components alone are picked up from one arm of the bridge and applied by transformer 7<1> to the grid circuit of valve 1. A further modification, Fig. 6 (not shown), combines the methods of Figs. 1 and 5, an amplifier shunted by a protective discharge tube being interposed between bridge 9 and transformer 71. Specifications 383,412 and 410,668 are referred to.