Could it be originating at your Head unit? Did you install it?? If no or whatever sheck to see that it is gorounded through the harness or directly to the chassis of the car. Sometimes installers will use the antenna as a ground to "Speed thing up". This works but eventually gets bad. IMO and experience. Take a looky there.

Later,

Chris

99 Se,MTX,TS.
Formerly Dieter88, TbnPlr
NEW ding guards !!