GB494577A - Improvements in automatic tuning apparatus for wireless receivers - Google Patents

Abstract

494,577. Valve circuits for wireless reception. ROBINSON, J. March 24, 1937, Nos. 8738, 13417, and 23565. [Class 40 (v)] Oscillations at the true intermediate-frequency produced by an additional oscillator are combined with the incoming signals to produce the true local-oscillator frequency which is fed back to control the normal local oscillator. In one arrangement, Fig. 1, the amplified signal frequencies in addition to being supplied to the normal frequency changer 13 are amplified and combined in a second frequency changer 22 with intermediate-frequency oscillations produced in a crystal-controlled circuit 23. The output is fed over lead 26 to the tuned circuit 14, 15 of the normal local oscillator. The incoming carrier-frequency also appears in lead 26 and is fed back through valve 13 to augment the incoming carrier to increase selectivity. In another arrangement, Fig. 2, the intermediate - frequency produced in frequency changer 41 is amplified at 44 and applied to a grid 45b of a second frequency changer 45, oscillations of the true intermediate-frequency being produced at the same grid by a tuned circuit 46. The local-oscillator tuned circuit 42 is connected to another grid 45a of valve 45 and the output of the valve includes both the intermediate frequency and the original frequency. By reason of electron coupling, the incoming frequency appears on grid 41b of valve 41 and is fed over lead 48 to valve 45 in which it combines with the intermediate frequency to produce a local-oscillation frequency which is fed back over lead 48 to control the local oscillator 42. There is also produced in valve 45, by combination of local oscillations and intermediate-frequency oscillations, the original signal frequency which is fed back over lead 48 and valve 41 to augment the incoming signals to increase selectivity. The system may operate with the circuits in a condition of sustained oscillation and this condition may be controlled by A.V.C. means so that the circuit is retroactive but non-oscillating except when in tune. Normal A.V.C. control or meeting of the output circuit may be employed. Specification 466,415 is referred to. Specification 489,571 also is referred to in the first Provisional Specification.