GB199964A - Improvements in and relating to the method of and means for generating and amplifying electrical oscillations by thermionic tubes - Google Patents

Abstract

199,964. Preston, L. G., and Shuttle worth, N. July 17, 1922. Thermionic amplifiers and generators.-A thermionic valve circuit for the amplification of applied impulses or for generating electric oscillations of any frequency, and applicable to the transmission or reception of wireless signals, or as a relay, is characterized by the grid being coupled electromagnetically to a coil in the anode-filament supply circuit, the retroactive coupling being thus made through circuits which are independent of the resultant amplified or oscillating currents. As shown in Fig. 2 (Prov.), applied impulses from a primary P are transferred to a step-up secondary coil K inserted in the supply circuit of the valve A, B. Amplified currents are generated in the tuned oscillatory circuit E.C.F.L. The grid is coupled at Q to the coil K, the direction of the voltages transferred to the grid being in phaseopposition to the plate voltage variations so that the load on the generator is kept constant. In Fig. 4 the coupling between the coils Q, K is sufficient to set the system into persistent oscillation. For telephony, the coil K is impulsed from an auxiliary circuit E, F, L. C, which may be energized in the manner shown in Fig. 2 (Prov.), so as to feed continuous amplified oscillations into the aerial A<1>. Microphonic modulation may be superposed on the circuit EF or on the grid circuit or aerial of the main system. As the carrier frequency is determined by the constants of the circuit EF, it will remain constant in spite of slight variations of the aerial constants due to swaying under wind-pressure &c. The coupling between the grid and the anode-generator-filament circuit may be direct, as shown in Fig. 2 (Comp.) through a portion L' of the main coil K. The portion L<1> may be inductively coupled to, or entirely removed from the coil K, and is connected in parallel with a condenser C<1>. A grid condenser and leak may replace the grid battery S, and high-frequency grid currents may be suppressed by the insertion of a choke coil between coupling-coil Q and grid leak.