Kensandyeggo wrote:
... I replaced it with an ICOM A-200 and a brand new Comant
antenna, or rather a radio guy did. He can't figure out why there is a
constant hash noise.

A couple of questions for Ken:

1. Can you verify that you didn't have the "hash" with the old radio?
2. How do the spark plug wires attach to the plugs? If it's just a simple
clip, then you indeed have an unshielded ignition system. But if you have to
turn a nut on the plug wire to remove it from the plug, you've got at least a
shielded harness and plug.
3. Does the noise vary with engine RPM, and does it literally sound like
popping? "Hash," to me, implies a hissing type noise. Does the noise stop if
the engine isn't running?
4. Does anything else in the aircraft affect it? Several years back, I was
having a bad interference problem on my comm radio. Turned out it was crap from
the transponder, leaking into the radio via a gap in its case. A handful of
aluminum foil fixed the problem.

If the noise seems dependent on engine RPM, you probably have an ignition
shielding problem...especially if you can verify the lack of a shielded plugs
and mags. The good news is that this is fixable...a new set of plugs, mags, and
harnesses will do the trick. The bad news is, it'll cost a bundle.

Here's a link that may help:

http://www.bowersflybaby.com/tech/fe...tm#radio_noise

Ron Wanttaja