GB216308A - Improvements in or relating to wireless systems - Google Patents

Abstract

216,308. Kinman, T. H. April 30, 1923. Thermionic heterodyne receivers; undesired signals, eliminating or limiting. - In a heterodyne receiving system, the grid oscillatory circuit 4, 5 of the receiving valve o is tuned to the received waves and has small resistance and large ratio of capacity to inductance. Local oscillations are also applied to a separate coil 3 in the grid circuit, either by a separate source or by retro-action from the tuned plate circuit 6; and the tuned grid circuit 4, 5 offers low impedance to such oscillations so that a minimum of the local energy is impressed on the aerial circuit 1, 2. The tuned grid circuit may be directly connected in the aerial circuit, as shown, or it may be inductively coupled to the aerial coil 2. When a frame aerial is employed, the grid circuit 4, 5 may be connected in series between the aerial coil and the tuning condenser; or the frame aerial and its tuning condenser may themselves form the tuned grid circuit. The beats produced in the circuit 7 are preferably supersonic as in Specification 197,405, and are transferred to further amplifiers. Undesired wave-lengths received by the aerial produce only small potentials across the circuit 4. 5. A screen 10 prevents direct magnetic action of the circuit 6 on the aerial.