Sorry to jump onto this thread but I also have a radio problem. Since fitting a Garmin 225A / 8.33 com I have a noise from my alternator. It is a whirring that gets louder with engine revs. If I turn off the field it stops so it is definitely the alternator. I have had the alternator checked and checked all the earth's. I have fitted 1 then 2 then 3 suppressors on the alternator but still have the noise. Does anyone have any ideas that would help ? Thanks.