GB384544A - Radio receiving apparatus - Google Patents

Abstract

384,544. Valve circuits for wireless reception. HAZELTINE CORPORATION, 15, Exchange Place, Jersey City, New Jersey, U.S.A.-(Assignees of Johnson, J. K. ; Central Avenue, Hartsdale, New York, U.S.A.) May 5, 1932, No. 12930. Convention date, July 7, 1931. [Classes 40 (iii) and 40 (v).] In order to eliminate interference which bears a definite frequency-relationship to the desired signal, such as the so-called " image " frequency in supersonic reception, the secondary S of the input circuit is tapped at the point 14 so as to form two paths. One comprising the winding S1 and condenser C1 forms a seriestuned shunt circuit to earth for the undesired or " image " frequency, whilst the other comprises a heavy-impedance primary P2 which transfers to the first valve voltages of the desired frequency flowing in the tuned circuit S1, C1. The equivalent circuit is shown simplified in Fig. 3. The reduction of voltage due to the tapping may be compensated by adding a second open-circuited winding P12' Fig. 7, to the primary P. The link circuit 11 may be tuned below the wave-band range by means of a condenser C3, Fig. 4, in order to maintain constant coupling at the lower end of the tuning scale ; the coil P2 may be closely coupled to the high-potential end of the coil S2 for the same purpose. Fig. 5 shows a modified form of coupling in which the link circuit 11 is designed to give a better response at high frequencies ; whilst Fig. 7 is another arrangement having the same property.