CX-7 AM radio issues

I know most people these days don't give a rat's a$$ about AM radio, but I like to sometimes listen to it. Problem: In my CX-7 unless a station's transmitter is less than 10 miles away, I always get reception interference from the engine. It's a steady "chik-chik-chik" that runs at about the same audible tempo as an old fashioned analog stopwatch. It's done this ever since I've owned the car -- about 5 yrs ago.

Only does this when engine's running. Is there anything I can do to stop this?