GB516643A - Improvements in or relating to radio and like transmitters - Google Patents

Abstract

516,643. Wireless transmitting systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and WASSELL, H. J. H. July 2, 1938, No. 19668. [Class 40 (v)] Multi-valve telegraph transmitters are keyed by controlling the potentials upon the screen grids of some of the valves and arranging that the final keyed valve takes maximum dead loss during " spaces " to prevent excessive load variations upon the power source. A keying valve 2 is connected in series with a resistance 4 across the D.C. supply 1. Keying means 6, 7, 8, is arranged to render valve 2 conductive or non-conductive and taps 9, 10, 11, on resistance 4 supply the screen grids of certain of the valves in the transmitter. The final valve 12 has its screen connected to the positive terminal of source 1 and its control grid 15 by which it is keyed is connected through choke 16 and resistance 17 to a bias source 18 and thence to a tapping 19 on the resistance 4. During "marks" valve 2 is conductive and positive potentials are applied to the screen grids to make the valves conductive, also the potential from tap 19 opposes the bias source 18. During " spaces " valve 2 is non-conductive and the screen grid potentials of the earlier valves falls to zero, rendering them non-conductive. Also the grid bias of the last valve 12 is determined solely by source 18 and is of such a value that the valve takes maximum dead loss. During " marks " a voltage is developed across resistance 17 by grid current which renders the grid of valve 12 more negative during "marks" than during " spaces."