GB405331A - Improvements in modulating and demodulating arrangements for ultra-short wave signalling - Google Patents

Abstract

405,331. Valve generating, modulating, and detecting circuits. INTERNATIONAL COMMUNICATIONS LABORATORIES, Inc., 200, Mount Pleasant Avenue, Newark, New Jersey, U.S.A., and CLAVIER, A. G., 46, Avenue de Breteuil, Paris. Aug. 4, 1932, No. 21888. [Class 40 (v).] An ultra-short-wave valve oscillator 1 of the vibrating electron type is utilized for modulation and demodulation by applying the modulating voltage (or the incoming modulated wave) to a potentiometer 12, connected across the cathode 2 and the high-voltage grid 3, whilst a tap 14 on the potentiometer is connected to the low-voltage plate 4. Direct voltages are applied to the electrodes 4, 3 from sources 7, 8 through chokes 9, 10 and the modulating or demodulating voltages are applied through condensers 13, 14. By using a selected ratio for the tapped potentiometer, the frequency of the oscillator remains constant. The specification includes curves showing the relation between grid and plate voltages for obtaining constant frequency ; and other curves showing the wave amplitude as a function of the grid voltage under constant frequency conditions. For modulation a straight portion of the latter curve is used, whilst for demodulation, operation is effected at a point where the amplitude is zero, i.e. where the valve is on the verge of oscillation.