static radio?

I have a 2000 Lincoln LS, and recently my FM radio only is static, buy only when the car is running. if i shut the engine off, it becomes loud and clear. AM is good too.
any ideas?
thanks.

Make sure the radio antenna connection to the back window is secure and there are no breaks in the grid for the antenna. The connection will be near the top center of the back window. Out of the headliner will be a small coax cable with a connector on it that snaps onto a connection on the rear window glass.

Sounds like mayber there is an issue either with that connection or with the ground for the antenna coax.

-Rod

i actually figured that it only does it when the rear window defrogger are on/ if i shut it off, radio works fine with engine running too.
does anyone know where the ground for rear window defrogger is?
thanks.