GB753509A - Improvements in or relating to radio receivers for use in television - Google Patents

Abstract

753,509. Radio receiving sets. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Oct. 7, 1953 [Oct. 10, 1952], No. 27543/53. Class 40 (5). In a superheterodyne radio receiver comprising means for switching the receiver to any one of a plurality of television channels and of wave ranges (e.g. for V.H.F. frequency-modulated sound broadcasting), the switching means so controls the connection of a variable condenser in the local-oscillator circuit that, when reception is taking place on one of the television channels operation of the condenser provides a fine tuning control, while when reception is taking place on one of the wave ranges operation of the condenser serves to tune the receiver to any one of a number of channels within the range. In the preferred embodiment the receiver, preferably employing turret tuning, is designed to receive on any one of a plurality of television channels within the frequency bands 44-67 Mc/s. and 174-216 Mc/s. and also to receive over two ranges within the V.H.F. band from 86.5 to 100 Mc/s. The receiver comprises the switched coils 1, 2 and 4, 5 in the aerial and R.F. amplifier circuits respectively and also a switched coil 11 in the circuit of the local oscillator valve 9. The coil 11 is tuned by a variable condenser 12 and a further fixed condenser 13. In television reception the condenser 13 in series with the condenser 12 restricts the effective tuning range of the latter which is then used as a fine-tuning control; for V.H.F. sound reception additional switch contacts on the switching means effect the closing of the switch 14, thereby short-circuiting the condenser 13 so that the condenser 12 provides an increased tuning range. In the circuit shown, valve 6 is the mixer and the coils 7, 8 comprise the first I.F. transformer.