[Uhehner]

I have had VHF interference issues on various boats caused by refrigeration units, depth sounders and florescent lights. It may be as simple a fix as a capacitor across the 12 volt supply to the radio. Try connecting the VHF to another temporary 12 volt battery to see if it's a power source problem or a radiation problem. Does your hand held VHF have the same issue? A good marine electronics tech can usually isolate and fix the problem.
Capt. George