Chrominance/Luminance Crosstalk in Cable Television Demodulators

Author(s): Charles W. Rhodes
Publisher: Society of Motion Picture and Television Engineers
Publication Date: 1 October 1970
Conference Location: New York, NY, USA
Conference Date: 5 October 1970
Page(s): 56 - 67
ISBN (Paper): 978-1-61482-903-4
DOI: 10.5594/M00697



Cable television systems frequently employ demodulators as part of their head-end equipment which convert the UHF or VHF-TV signal to video. Distortions of this (video) signal cannot generally be corrected. In the case of color TV signals, distortion changes the luminance level; it always is decreased in the case of the negative modulation. Quadrature distortion also is a systematic and fundamental source of differential gain, chrominance gain being reduced as the luminance level increases. When the cable television demodulator and the home receiver both contribute to the distortion, they are additive. The interrelationships of luminance errors and differential gain in terms of both luminance level and chrominance level are outlined for several different IF response characteristics. A new test signal to measure the luminance distortion and its application is discussed. Other methods are reviewed.