GB530024A - Improvements in or relating to radio and like transmitters - Google Patents

Abstract

530,024. Modulating systems. TELEFUNKEN GES. FUR DRAHTLOSE TELEGRAPHIE. June 14, 1939, No. 17417. Convention date, June 14, 1938. [Class 40 (v)] In a high efficiency modulating circuit arrangement, carrier power is fed to a load by a valve which is connected to the source of anode current through a low frequency choke, a second valve supplies supplementary power during positive half-waves of modulation, and a third valve consumes power during negative modulation halfwaves. The class C amplifier H1 is connected to the anode current supply + Ua through the low frequency choke Dn and the high frequency choke D1, and supplies unmodulated carrier frequency power to the load R connected across the tank circuit L, C1, C2, valve H2 operating in class C is connected to the source + Ua through the high frequency choke D2 and is driven by both carrier and modulating voltages in such phase that during the positive modulating half cycles it contributes power to the tank circuit and load. The choke Dn maintains the feed current of valve HI steady and thus causes a rise in anode voltage and increase in power output during the positive modulation half cycle. The valve H3 is connected directly across the tank circuit and its anode is supplied by a low voltage source + U2, its grid is driven with carrier and modulating potentials in phase opposition to valve H2, and since it is blocked on positive modulation half waves and takes current in the positive half periods of anode alternating voltage it thus consumes power to produce the negative half cycles of modulation. The choke Dn prevents the feed current of valve H1 rising due to the decrease in the effective load. Specification 497,343 is referred to, and a circuit embodying that invention is described.