I used to run my 720 straight from the cigarette lighter adapter, and never had any problems with audio interference. After an in-flight electrical problem, I decided to buy an external battery for my 720 and run with it in-line between the cig lighter and the 720.
Recently, I've noticed a lot of interference/squeal on the radio/intercom, and I finally figured out that it's related to the wire that runs from the battery to my 720 on the yoke. When I have it routed neatly, it tends to cause more interference. If I just leave it flopping around in the air, it seems to be better, but I have yet to find a routing that completely eliminates all interference. Trial and error just isn't working for me this time.
Of course I'd like to route it more neatly. Is there anything I can do to help alleviate any interference? A certain waiy to coil the wire, or routing it parallel / perpendicular / coiled / some distance away from headphone cables / jacks / other wires?
Could a magnetic choke be part of the solution? What size choke would I need, and where would it (they?) need to go?