GB516901A - Improvements in radio-receiving apparatus - Google Patents

Abstract

516,901. Wireless receiving systems. GENERAL ELECTRIC CO., Ltd., and ESPLEY, D. C. July 27, 1938, No. 22391. [Class 40 (v)] In a receiver having a common frequencychanger for television and accompanying sound and also adapted for ordinary broadcast reception, the broadcast signals, preferably after a preliminary change of frequency, are also applied to the same frequency-changer at a carrier frequency not substantially greater than and possibly much less than the intermediate frequencies of the television and accompanying sound at the output of the common frequencychanger, and selective means capable of distinguishing between adjacent broadcast stations are introduced into the broadcast channel in such a way that they do not restrict the television band. The Figure shows alternative input paths A, B for the television and accompanying sound and for the broadcast, respectively, a common frequency-changer 3, and separate outlet paths, one 6 used in common for both sound signals and the other 9 for the vision signals. The station-selecting means may be permanently connected in the separate broadcast path at 15a, or may be subsequent to the common frequency-changer 3 in which case it may be switched in, e.g., at 15b, when changing-over from television to broadcast reception. Alternatively, circuits in the common path may be modified as regards selectivity when change-over takes place, e.g., by connecting condensers across the coupling circuits, or there may be two parallel paths one passing a narrow band around one I.F. and the other a broad band around a different I.F. Where the broadcast input frequency to the frequencychanger 3 is the same as the I.F. output of the television sound, oscillator 4 is suppressed during broadcast reception and the frequencychanger acts merely as an amplifier, but where it is less, the frequency of oscillator 4 is suitably changed to give the same output frequency from frequency-changer 3 for both sound channels. Specification 453,484 is referred to.