GB172350A - Improvements in modulation systems for wireless signalling and the like - Google Patents

Abstract

172,350. Taggart, J. Scott-, and Radio Communication Co., Ltd. July 6, 1920. Thermionic amplifiers and modulators; directive signalling.-In wireless receiving systems, a plurality of electric discharge devices such as thermionic valves, each of which is provided with means for controlling the current through it, are connected in series so that a main current flows through the devices, the magnitude of which is dependent on the combined effects of the different controlling-means. In the arrangement shown, two three-electrode valves V<1>, V<2>, are connected in series with a main source of current H, a receiving circuit L<1>, C' being connected to one grid, and a local source of oscillations G to the other grid. The source G may be of radiofrequency, preferably arranged to give beats for heterodyne reception. Two wireless receiving systems, receiving the same or different signals, may have their effects combined by applying them to the grids of the two valves, one or both valves acting as a detector, and the antenna systems may be differently arranged to produce directional effects. Alternatively audio-frequencies may be applied to one or both of the grids. According to the Provisional Specification, two valves connected in series may be used in transmitting systems. One valve may be selfoscillating, the oscillations being modulated by low-frequency oscillations imposed upon the grid of the second valve; which grid may be given a normal negative potential so that the main current is very small or zero when the modulating potentials are not applied. The modulations may be produced by a microphone or by a key in the grid circuit. The key might be arranged to short-circuit completely the second valve.