The problem with the passive version of these [Ground Loop Isolators] is that there is a massive drop in signal level... good if you have mixer with gain to boost back up to the right level, but if you are simply using it in line then it's problematic - it was deal breaker for the installs I tried it on. I made sure all power leads to PAW and intercom had ferrite beads on them.
Yes, Steve, I agree, it’s always best to look for the
actual reason for interference and deal with it appropriately - often as you say by fitting ferrites to power and other signal cables, or simply re-making a dodgy connection or replacing a potentially high-resistance earth.
I have, however, come across a couple of cases where the interference to audio
was clearly coming from the Raspberry Pi in the PilotAware - and was being output to the intercom via the audio jack. In both cases, ferrites on the audio lead were of no help whatsoever, but fitting Ground Loop Isolators
was effective, and probably the only solution (short of replacing the Raspberry Pi).
As you say, not always the best solution, but can certainly worth trying.
Best Regards
Peter