In the past there have been a few issues with the coax connectors being grounded out and the connector had to be replaced. Checking them requires an ohm meter. At each connection, touch one test lead to the center (brass wire) and the other lead to the outer part. If you get a reading or continuity either one end of the coax or both ends may be bad. Look for any pieces of aluminum foil touching the center wire. Another potential problem is improper wiring within the coach. Either of these issues may be something to have your dealer check. When you picked up your rig, did the dealer go over the operation of the antenna and TV's???