Well, audio manufacturers save some money on making radios these days by putting no money in the AM tuner because the know 85% of the drivers will never use AM. The drawback is the people that do listen to AM are old and like to complain. All and all there isn't much of anything you can do for him. I have heard of an old half assed fix of wrapping the radio with aluminum foil to reduce the ground loop noise, but I have never tried it.