My channel scan will find 12 channels (under "antenna") but won't find channel 3. Under "cable" (with my Super Nintendo's coax cable plugged into my tv) it can't find any channels. I don't have the AV cables. Is it possible to use the coax cable without AV cables to use my SNES?
You can try running a channel scan under antenna with the SNES on and connected to the antenna input.
On some TVs they let you run a scan to just add channels to the already detected ones. This is for rotating directional antennas.
You will get a better picture with the AV cables.