On Monday, July 11, 2016 at 4:11:33 PM UTC-7, wrote:
Ferrite.
That was the word I was searching for.
They solved the problem but it took a significant amount of trials to solve the noise. The problem has stayed fixed for many months.

You can put a 50 ohm terminator on your antenna input to the radio and see if the noise stops. If it does you are probably receiving it from an external source. If it doesn't it MAY be generated internally, or it may be conducted from an external source thru the power leads. You can isolate that by powering the radio from a separate power source than the rest of the glider..

Tom