GB343678A - Improvements in or relating to modulating arrangements, suitable for use in wireless and other high frequency signalling systems - Google Patents

Abstract

343,678. Valve modulating circuits. TELEFUNKEN GES. FUR DRAHTLOSE TELEGRAPHIE, 13, Hallesches Ufer, Berlin. Jan. 7, 1930, No. 635. Convention date, Jan. 7, 1929. [Class 40 (v).] In modulating arrangements of the kind in which the signals vary the grid voltage of a valve 2 connected in the grid directcurrent circuit of the high-frequency valve 1 ; and in which an auxiliary valve 3 having its grid circuit directly affected by the signals is connected between the grid and plate of the valve 2 ; a battery 4 and resistance 5 are connected in the grid circuit of the valve 2, and a battery 6 in the grid circuit of the auxiliary valve 3, both batteries tending to make the grids negative relatively to their associated filaments. When the signal applied through the transformer reduces the negative bias on the grid of valve 3, current passes from the condenser 8 through the valve 3 and resistance 5. The grid of valve 2 is thus made less negative or even positive. By thus operating the valve 2 with a positive grid, the heavy grid current of the main valve 1 may be passed without using an excessive number of valves 2 in parallel. As the grid of valve 3 is maintained negative, no grid current passes through the input transformer 7 ; whilst the grid current of the valve 2 can pass through the filament-plate path of the valve 3. For telegraphy, a keying relay may be arranged to short the grid and filament of the valve 3, and a high resistance may replace the secondary of transformer 7.