Tuning of Nonstandard TV Picture Carriers

In numerous households with video services the input signal to the tuner of a TV receiver may not necessarily be provided by an antenna, but may be a CATV signal or originate in a home instrument like a VCR or a video game. The RF carrier frequencies of signals not received directly from commercial TV stations do not necessarily conform with the FCC standards. For example, the picture carrier frequency of a channel may be offset by several megahertz from the FCC specified value. The purpose of this paper is to describe a reliable method of automatically tuning nonstandard TV signals with offsets as large as 3 MHz.