AM Radio reception fades in in and out

Do you have a telescopic antenna? They used to make an antenna about 60" long. I would definitely suggest one if you don`t have one yet. The long antennas look weird but they do a good job of picking up and holding AM broadcasts.

If you adjusted the trim on the radio I guess there`s not much more you can do there. Check that the antenna base is grounded well. Is your radio not solid state?