You need a TV tuner.
You need to "convert" the RF TV signal into an audio signal. This is similar to expecting to plug in an FM antenna into the AUX input on your receiver and having it work. It does work on your receiver, but remember that you feed it through the tuner section first.
Your best bet is to find the audio outputs on the back of your TV set. If there are none, most VCR's have them. In that case, you would need to use your VCR to tune in the TV channels but at least you would be able to get them in stereo.
If all else fails, new TV's with stereo audio outputs are getting cheaper and cheaper every day. I just picked up a 27" Toshiba with oodles of I/O options for $188 @ 6th Avenue.