GB242948A - Improvements in or relating to the supply of electric power to high frequency signalling systems - Google Patents

Abstract

242,948. Western Electric Co., Ltd., (Assignees of Holden, W. H. T.). Nov. 13, 1924, [Convention date]. Thermionic valves, arrangements and connections of.-The high and low tension supply to valve receiving or transmitting sets is derived from a common source such as the electric light supply mains. The plate voltage, grid-bias, and filament supply is taken from a single rectifying unit, though certain of the valve filaments are energized from a separate transformer unit and the space current flowing through these valves is used to augment the filament supply to the rest. The Figure shows a superheterodyne receiver, local oscillations being supplied from a back-coupled valve O1 to the first detector D1, the output from which passes through one or more intermediate amplifiers A1 to a second detector D2, and thence through a push-pull amplifying stage A2 - - A5 to the loudspeaker 24. The midpoint 6 of the frame aerial 1 and one of the outer terminals are connected across the grid and filament of the first detector D1, the plate of which is connected to the other frame terminal through a stabilizing condenser 5. Energy from the mains L1 feeds two transformers 25, 26 in parallel. The transformer 25 feeds the filaments of valves A2 - - A5 direct through conductors 28, 29 and 30, 31. The transformer 26 feeds the full-wave rectifying unit R1, R2, through a main winding 33 and an auxiliary winding 32 which energizes the filaments of the rectifying valves. A blocking circuit 34 and smoothing circuit 35 prevents the passage of current irregularities into the set. The rectified voltage is fed to the plates cf the amplifiers A4, A5 by a conductor 36 through a potentiometer 48, and to the plates of the amplifiers by a lead 46 through the windings 47. The tubes D2 and A1 are fed from potentiometer 38, 40 through the transformer primaries 39, 42 whilst the supply to the oscillator 01 is'taken off from the point 43. Grid bias is supplied to the amplifiers A4, A5 through a conductor 52 and balanced resistances 53, to A2 and A3 through a resistance 54, conductor 55, the filaments of tubes D2, 01, and A1, and conductor 56 to the balanced resistances 57, and to the tubes A1, D1 and 01 through resistance 54, conductors 55, 58 and 8 and through the respective transformer windings to the grids. The filament supply to the tubes D2, A1, D1 and 01 is derived in part from the space current flowing through the amplifiers A2--A5 through the leads 28 - - 31 to the midpoint of transformers 15, thence through lead 12 to the filaments of D1 and A1, through conductor 10 to the filament of 01, then to D2 and back through resistance 54 to the negative side of the rectifier R1, R2. The rest of the filament supply to these tubes comes direct from the rectifier through conductor 36 to point 37 and then through the resistances 38 and 40 in parallel to the conductor 12 which supplies the tubes D1, A1, 01 and D2 in series.