GB389026A - Superheterodyne receiver for wireless signalling - Google Patents

Abstract

389,026. Valve circuits for wireless reception. HAZELTINE CORPORATION, 15, Exchange Place, Jersey City, New Jersey, U.S.A.-(Assignees of Macdonald, W. A.; Little Neck, New York, U.S.A.) Nov. 21, 1931, No. 26291/32. Convention date, Feb. 13, 1931. Divided on 391,521. Drawings to Specification. [Class 40 (v).] One or more of the coupling transformers in the intermediate frequency stages of a superheterodyne receiver have one coil, preferably the primary, tuned by 'a condenser to the intermediate frequency and the other coil so wound as to be resonant, with or without added capacity, at a frequency higher than the'intermediate frequency but lower than the lowest signal frequency to which the receiver can be tuned. The coils are somewhat tightly coupled by placing their bobbins close together on an axial former, so that the transformer as a whole resonates at the intermediate frequency. The secondary coil reacts as a capacity at all frequencies within the tuning range, and thus attenuates any signals which penetrate the first detector without change, of frequency. The secondary coil may be shunted by a tapped resistance for giving control of amplification. Where the transformer is followed by a diode detector, it is arranged to step,down the voltage to suit the resistance of the detector. When the secondary coil of the transformer is tuned to the intermediate frequency, only a portion of the secondary should be connected across the detector. Transformers as described above may be preceded at another stage of the intermediate frequency amplifier by coupled tuned circuits arranged to give double resonance. The Specification describes a complete superheterodyne circuit as disclosed in Fig. 1 of Specification 391,521.