Thanks for the heads-up on ferrites. I was afraid that I'd find that 60Hz is too low for them to filter out. Sounds like that's the consensus here, too.
The brand-new radio sounds almost as bad as the circa 2002 radio it replaced in the same location. The radio on the flybridge, on a different circuit and farther from the inverter, but powered from the same breaker panel, sounds fine. The wire to the problem radio takes a rather circuitous route
; the PO just tapped an existing lighting
circuit where it passed through the compartment with the inverter. It's a good hefty wire, about 14 Gauge, with good connections, and there's no voltage drop when transmitting. Just the noise.
So, it sounds like I'm going to be running a dedicated power cable sooner, rather than later. Something I've wanted to do anyway. I'll route
it from the other direction, away from the inverter.
Any value in buying
shielded cable? Should it be a twisted pair or is flat OK?