I have checked the antenna connection, it seems tight.
I just had an audio installer add an amp, extra speakers and a subwoofer. When he saw the radio he said that it was an Audiovox in a fancy wrapper and not to expect too much from it. I wanted to get another opinion before doing something rash. At least I have good sound in the front now when listening to my own music.
Since the coach has no good place to mount a GPS I am toying with the idea of replacing the Jenson with a unit that has a GPS built in. That might solve the reception problem at the same time.