GB172376A - Improvements in and relating to radio receiving systems - Google Patents

Abstract

172,376. Taggart, J. Scott-, and Radio Communication Co., Ltd. Aug. 31, 1920. Thermionic amplifiers; atmospherics, limiting. -In a method of limiting the effect of loud signals, currents due to the signals are passed through a thermionic valve so as to set up back electromotive forces to lessen the effects in the receiver, or the receiving circuit is shunted by a rectifier conductive to currents of above a predetermined amplitude. The method is applicable to limiting both audio- and radio-frequency currents. In one example a three electrode valve with a telephone in its plate circuit has the received signals applied to its grid. Shunted across grid and filament is a two-electrode valve in series with a battery adapted to give its anode a negative potential. When signal currents are strong enough to make the anode positive, some of the current is by-passed through the valve. In another example, Fig. 3, a resistance R is connected as shown in the grid circuit of the receiving valve V<2>. When a strong positive half-cycle from the receiving circuit L<2>, C<1> is making the grid of the valve V<2> positive, current through the valve V' sets up an electromotive force across the resistance R tending to make the grid negative. In either arrangement two oppositely-connected two-electrode valves may be used to obtain bypassing for both half-cycles. According to the Provisional Specification three-electrode valves may be used in place of two-electrode valves, and continuous waves may be received with an ordinary detector if the damping is made periodic.