Also possible but less likely, it could be a alignment issue.
For example on my FADA 895 (RCA 630ts clone), I get no snow when there is nothing hooked to the RF input, just a raster, but I can tune in things on all channels if I try, not very well mind you, but it works, when the video is at peak clarity, the audio is a bit fuzzy, and vice versa, I can find a decent happy medium when video source is DVD or laser disc, ( channel 3), but it's BUZZ-O-MATIC with most most input from the cable box, which is typical for cable input,
So, I know that mine can do with an alignment, which I have been avoiding because I don't want to pull the chassis again unless I really have to, and I have the direct video input option anyway in the meantime, but I will try it someday, though I hear it's an arduous task to get it right.
Anyway, this also may or may not be similar to the problem you are having with your set, just a guess.
Weird thing is, with mine, with nothing but an alligator clip lead hooked to the antenna input set to CH 3, and adjusting FT through it's full ranges, at one spot, it locked on to a FM station, not sure which one.
