GB1000608A - Improvements in and relating to television apparatus - Google Patents

Abstract

1,000,608. Radio receivers. BLAUPUNKTWERKE G.m.b.H. Oct. 25, 1962 [Nov. 9, 1961], No. 40417/62. Heading H3Q. In a television tuner switchable to receive either within the VHF or UHF bands, and wherein the same general circuit configuration is used for reception over both bands, the switching being effected by switching of fixed induction and associated trimming capacitors, but the same capacitors being used for tuning and the same valves or transistors being used for amplification and frequency changing over both bands, the inductance elements for VHF tuning each comprise a half-wavelength conductor, the central portion of which is displaceable and is mounted together with the corresponding VHF inductor on the rotor of a switch so that either the central portion of the conductor or the VHF inductor may be selectively brought into circuit. Fig. 1 (not shown) illustrates a tuner comprising a radiofrequency amplifier valve preceded by a switchable tuned input circuit and followed by two switchable tuned band-pass circuit providing the input to a mixer-oscillator valve whose anode circuit includes a further switchable tuned circuit tuned to the local-oscillator frequency. The four tuned circuits are mounted within separate compartments in a screened container, coupling between compartments being effected by suitable slots in the compartment walls. Fig. 2 shows a section through one compartment. Conductor 53 mounted on a switch rota forms together with fixed conductors 50, 51, a half-wavelength section serving as the VHF tuning inductor. Section 53 may be replaced by inductors 57 or 58 for tuning over separate parts of the VHF band. The radio-frequency valve amplifier stage may be preceded by or replaced by a tunnel-diode amplifier stage.