Sounds like Mark has it covered, I am no expert on HAM radios... but if your problem has to do with the signal wire for the transducer run next to or being in contact with the antenna wire you need to shield them from each other. There is a sound deadening product called Deamplifier Pro, looks similar to DynaMat, but it is supposed to have superior shielding properties. Thin strips taped around the antenna cable anywhere it passes near or makes contact with other signal wires or power wires will shield it from interference. There is more than one product of "Deamplifier Pro", one has the super sticky side and foil on the other, the one I am talking about specifically is just the foam with no foil or adhesive side, they just call it the 'loaded vinyl foam'. For the life of me I can't find a good example on a web page, but I remember high-power car audio installers swearing by it to keep their amplifier signal cables isolated from the high power supply cables.