A few weeks ago I posted my troubles with radio whine when engine was
on. I was led (by myself) down a garden path of the external amp power
system being the problem. I posted what I did. Talking to David B. on
his trip out here gave me a better understanding of a ground loop
problem and today I think I have fixed my problem.

I brought in a new ground and power to the *headunit* straight from
the aux battery and ground beside aux battery. This has fixed things.

I concluded that the power and or ground to the headunit was
compromised somewhere downstream of where the headunit harness plugs
in, and it was easier and more reliable to just run new supply wires
to it.

alistair