I'm sure you want more channels for your TV sets than the usual channel 3 or 4 set top boxes or VCRs provide. I managed to convince a frequency synthesized LA7161 TV modulator chip to do channel 13. No point in repeating all the gory details here, see http://videokarma.org/showthread.php?p=3114423#post3114423 which is in a sister forum in this web site.
http://videokarma.org/attachment.php?attachmentid=184208&stc=1&d=1409950170

This was an RCA TV modulator, one that has a feature that turns itself off if the input video signal goes away. Then it passes RF from an RF input F connector.