GB155642A - Improvements in wireless telegraph receivers - Google Patents

Abstract

155,642. Gill, E. W. B. Sept. 22, 1919. Wireless telegraphy.-In a receiving-arrangement comprising two thermionic valves, the plate A of the first valve is connected direct to the grid g of the second valve, and is otherwise entirely insulated. The potential of the grid G of the first valve is adjusted by a potentiometer P in conjunction with a small battery C, and is varied by oscillations received from the antenna E. The plate a of the second valve is in circuit with a telephone T and battery V. The combination gives a characteristic of the form shown in Fig. 2, the current in the circuit of the plate a remaining at first approximately constant as the voltage on the grid G is increased, then falling sharply, and then becoming again approximately constant. Thus from L to M the combination has a negative resistance. Curves are given showing the effects of varying the filament heating-currents and the voltage of the anode battery V. The combination can be used as a rectifier at either L or M, or as a current-limiting device, so that all signals over a certain strength give sounds of equal strength, or as a means of discriminating between different types of signals or between signals and atmospherics. Between the rectifying-points L and M, signals go to a minimum, and it is,found that the minimum adjustment differs for different types of transmitter. Thus of two signals of equal strengths it is possible to hear only the first on one adjustment and only the second on another adjustment.