GB1295653A - - Google Patents

Abstract

1295653 Television receivers PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 5 Dec 1969 [10 Dec 1968] 59525/69 Headings H3Q and H4F A television receiver includes a mixer 1, an oscillator 9 with an external tuning arrangement 79, a reactance stage 71 connected to the output of a phase detector 45 for automatic frequency control of 9, the inputs of the phase detector being connected to the input and output terminals of an I.F. sound carrier suppression filter 21 present at the output of the mixer 1, the output of the phase detector 45 being further connected to a picture information filter 49 for adjusting the picture quality by altering its frequency response characteristic. Both luminance and intercarrier sound signals are present at the output of detector 55 while a chrominance sub-carrier and an intercarrier sound signal are present at the output of a detector 33. In operation, an adjustment of the external tuning control 79 produces a change in the I.F. frequency. The intercarrier sound signals present at the outputs of detectors 55, 33 are phase compared at 45 to produce an error voltage for electronically tuning oscillator 9 to maintain the I.F. frequency. The error voltage produced is also applied to a controllable filter 49 present in the R.F., I.F. or video sections of the receiver, so that the frequency response of the filter, especially the Nyguist slope may be suitably controlled to improve picture quality. Separate tuning adjustments 79 may be provided in each channel of a push-button receiver.