What kind of HF antenna? Vertical? Remember that 1/2 of the radiation is not from the antenna, but rather from radials from the base of the antenna. Sounds like this is a vertical that is mounted on the rear ladder without any thought to the lower portion of the antenna; ie the radial, or ground, connection. Sounds like a good way to have RF all over the coach --- can see how slideouts go crazy --- and can cause interference to TV's (will not make his neighbors happy when they can't see their Soaps)..
Make sure the base of the antenna has a good RF Ground.. don't rely on just the ladder for a good ground. Just a thought.
Wire antenna and antenna tuner might be another choice.