Ron Wanttaja wrote:

I'd installed my new Microair transponder a month ago, but have been having
troubles with interference. The transponder was inducing bad clicking
sounds into the comm radio receiver, making the radio difficult to
understand.

I couldn't really blame the Microair, since the Terra transponder I'd had
before did exactly the same thing. But I'd been hoping the new transponder
and installation would eliminate the problem...especially since I'd
reworked all the transponder wiring and moved the antenna to a different
location. But the interference continued.

The main suggestion I got from the avionics guys around here is that the
transponder was interfering via the cables running to the headset jacks. I
installed shielded braid over those cables, though, and the problem
continued.

All the electrical connections to the radio (except the antennas) are made
via an unshielded flat connector. Since the wires had to spread out to fit
the connector, I hadn't been able to run the braid all the way to the
radio...it terminated about two inches away, and I ran a ground wire from
the braid to the radio chassis.

It seemed to me that the most likely culprit was that last two inches of
unshielded wiring and the unshielded connector...especially since they were
the closest part of the wiring harness to the transponder.

So, today I took a roll of aluminum foil out to the airplane and wrapped
foil around the back of the radio, leading it down the wires until it
contacted the braid. Duct tape, of course, to hold it in place.

I'm happy to report that this solved the problem. Radio signals were
perfectly clear.

I figure the foil isn't worthwhile as a permanent solution. A guy at the
airport suggested using aluminum window-screen material. It appeals to the
cheap side of me. Any drawbacks, or suggestions for alternates?

Ron Wanttaja


If it ain't broke (no mo!) don't fix it...


Richard