Quote:
Originally Posted by Penthode
If you are using cheap consumer channel 4 RF modulator, it produces a double sideband am video signal. It is conceivable the video carrier is on the opposite slope of the IF response so that the picture looks good but the audio would be absent.
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Some cheapie modulators create the sound carrier at 4.5MHz, mix that with the baseband video, and then modulate all that onto the channel carrier. So you'd find the sound carrier at the usual place, and also 9Hz lower (on the other side of the channel carrier). Maybe you could use an FM radio station around 88.3MHz with the TV set to channel 6, and fine tune the TV a little high (to cause the split sound IF to find the FM radio station. This should verify that the sound IF is at the right frequency, and not 4.5MHz off. But be aware that FM radio stations have much stronger deviation (FM modulation) than TV sound carriers do. So the FM station will likely come out distorted.