GB587553A - Improvements in circuit arrangements for use with widely-separated frequency bands - Google Patents

Abstract

587,553. Valve circuits for radio reception. STANDARD TELEPHONES & CABLES, Ltd., and HOLLAND, J. D. Sept. 1, 1944, No. 16722. [Class 40 (v)] A multi.electrode valve in an amplifying, detecting or generating circuit is-connectcd as two separate triode sections to generate two different carrier frequencies or operate independently on two wave trains modulated with different signals. In Fig. 1, wave trains E1, E2 at different frequencies are amplified in valve sections 2, 3, 4, 2, 5, 7 respectively to produce oscillations at both frequencies at anodes 4, 7. Impedances 10, 11 represent tuned circuits or filters adapted to. select oscillations E1 at terminal 14 and oscillations E2 at terminal 15. The circuit may, be used as a double frequency changer by inserting a local oscillator between terminals 22, 23 instead of the strap connection, and replacing impedances 10, 11 by band-pass filters to select the corresponding side-bands at the output terminals 14, 15. When voltages E1, E2 are accepted selectively, different local oscillators may be switched to terminals 22, 23 in each case. Fig. 6 illustrates, a double oscillator circuit in which the cathode, first and second grids are coupled with tuned circuit 87, 88, 89 to produce oscillations at one frequency in output coil 101, while the cathode, fourth grid and anode are coupled with tuned circuit 93, 94, 95 to produce oscillations at a second frequency in output coil 102. Switches 86, 92 allow simul-. taneous or alternate selection of frequency. In Fig. 3 (not shown) circuits of the type illustrated in Figs. 1 and 6 are combined with automatic gain control circuits in a schematic diagram of a twin-channel radio receiver with separate I.F. band amplifiers associated with different local oscillators.