no picture with over the air: cable works fine

Do you have a button to push, to power the antenna? If so, and you are doing everything right, then I'd suspect a a coax problem, maybe miswired, or shorted.

Has it worked in the past, and just recently no longer working?

Jerry

Is your television set properly for over-the-air DTV reception (as opposed to cable), and have you run a channel scan?

Over the air.....Button for power must be on
Cable it needs to be off

TV needs to be set for 'air/antenna' input
*Cable is set to Cable or Aux input

Head of antenna needs to be POINTED/AIMED in direction of Tower
Many on-line TV directional websites ....put in your location and it will show direct/distance for towers
Auto Scan for available channels
*Each time you move you have to re-aim antenna and rescan for channels

Ok, Thinks I have seen:
Multiple Wall Plate/power inserter/Switches... Got to find the right one (Very rare)
Wall plate off/fuse blown
Wall plate not even connected
Bad connection (Roof pass through)
Bad coax
Missing head (ok you don't have that one)

Now I'm not a professional RV tech but twice it's been the roof pass through One was a pass through (it stuck up through the roof) I traced the problem to that point provided a bypass line and a dealer/shop fixed it (Tear into roof... NOT on your rig will I) The other time (my own) the connection was in the roof ( **THOUGHT** sealed (not very well) and had corroded to dust or darn close to it. A new barrel connector and two new waterproof compression cable ends and SUCCESS.

I've also seen popped fuses though on my rig I never found the @34#@ fuse for that circuit.

A test light is your friend by the way (Google automotive test light or visit most any auto store or departmetn, Looks like an old fashion ice pic)

Thanks to all that replied; by bypassing the interior cable found out that the existing cable is bad, now to find someone who knows how to replace it, without destroying the interior.