RF modulator

Sold for about $40, very high quality modulation to whatever analog channel.

Well, at least every TV sold now can support both NTSC and digital signal.

I can't seems to locate one model, but the cheap ones only modulate on Chan 3 and 4.

http://www.apogeekits.com/tv_transmitter.htm this is random google.

http://www.amazon.com/modulator-amplifier-video-sender-transmitter/dp/B003YPDWJE