On the electrical noise:  When using the handheld transciever, was  any
portion of the radio connected to the airplane - intercom or antenna?
If not, the noise is radiated.  That suggests to me that the  noise  might
be ignition related - a high energy source.

Is the noise a buzzing sound or a whine?


Matt-

Good call Matt.

Paul Lamar

Matt,
It is more like buzzing loud static. I don't have it on the ground or
below 4000 rpm. Looks like it is rpm related.
I hear clear incoming transmissions, but my replays contain the same
background static. One clue is that when
the prop pitch adjustment switch is engaged, the noise stops.

Bulent.

Ah so try a high voltage capacitor wired across the brushes.
Static (pardon the pun) electricity is generated by the
brushes rubbing on the contacts.

Here are some early ideas of mine and Butch's to reduce
the wear on the brushes. The ACAD stuff is mine.
-- 
Paul Lamar ...No rotor no motor.

Paul, that's a smart idea. I should run to the Patent Office first
thing in the morning :)
Seriously, I like it. Will have to put it on my list of things to do.
Buly

Too late.  We published it in 2001.
Try the capacitor right way. Will not hurt. Don't use an electrolytic.
Use a ceramic non polarized.