GB363480A - Improvements in and relating to devices for the modulation of wireless transmitting apparatus - Google Patents

Abstract

363,480. Wireless transmitting systems. BARON, H., 231, Strand, London.-(Lorenz Akt..Ges., C. ; 1, Lorenzweg, Tempelhof, Berlin.) Nov. 14, 1930, No. 34356. [Class 40 (v).] In a radio transmitter, the modulating system is arranged to vary the mean value of the aerial current in accordance with the prevailing signal strength in such a way that the lower limit of aerial current is maintained substantially constant. As shown in Fig. 2, modulation is effected by the signal currents amplified at V and applied to a winding W1 on the iron-cored choke D in the aerial circuit. The signal currents are also applied via a transformer T1 to a rectifier R3, and the rectified voltage is applied to a valve R1 causing the direct current through a resistance n in its plate circuit to vary in accordance with signal volume. These variations are amplified in the valve R2 and applied to a second winding W2 on the choke D. In a modification, Fig. 4 (not shown), only a single control coil W2 in the plate circuit of the valve R2 is used, but the grid circuit of this valve receives the signal voltages from the amplifier V as well as the volume voltages from the resistance n. A full-wave rectifier may replace the rectifier R3 and valve R1, Fig. 6 (not shown). When thermionic modulation is employed, Fig. 8, the grid circuit of the modulating valve R4 receives its high-frequency input through a coupling L1, its signal input through a transformer T2 from the amplifier V, and its signal volume input through a resistance n traversed by the rectified signal voltage.