GB493368A - Improvements in or relating to alternating current amplifiers - Google Patents

Abstract

493,368. Valve circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and CLOUGH, N. H. April 6, 1937, No. 9771. [Class 40 (v)] The magnifier stage of a transmitting amplifier becomes conductive when flow in a normally-energized inductive circuit suddenly ceases or is reduced, the frequency of the flow variations being controlled by an oscillation generator. The oscillation generator 1, 2 feeds a pair of valves 14, 15 which pass on the positive and negative peaks of the oscillator as negative flicks of twice the oscillator frequency to the grid of valve 26. This valve is normally conductive and its plate circuit includes inductance 30. The negative flicks cut off valve 26 so that the flow in the inductive anode circuit is interrupted at twice the oscillator frequency. The anode 29 is directly connected to grid 31 of magnifier valve 32 which has its own tuned flywheel circuit 35, tuned to twice the oscillator frequency and the interruption of flow through valve 26 causes steep sided positive pulses to be applied to the grid 31 so that an approximately sinusoidal waveform of twice the oscillator frequency appears across tuned circuit 35. The valves 14, 15 may be replaced by a single phase reversing valve, the output then being at the same frequency as the oscillation generator. Modulation is effected by operating telegraph key or relay 36 or, for telephone transmission, by connecting the grid resistance 24 to the cathode 25 through a source 37 of modulation potential and a negative grid bias source 37. Alternatively the valve 32 may be a pentode, modulation potentials being applied to the suppressor grid or the phase reversing valve may be a pentode, keying being effected by a key or relay between the screening grid and earth.