Ken,
I would carefully trace the "goodness" of the antenna lead from the tray to
the ship. A short or on open would get your symptoms.
I think a simple Ohm-meter would work. With the radio-to-tray connection
disconnected, you should see almost an open-ckt (meg-ohms) from the ship's
antenna to cable shield/ground. And you should see a closed circuit from the
antenna to the coax center-conductor.
Good luck.

Heinz