1993 Honda Accord Radio Static

I have a problem receiving AM radio. When I turn the car off, they come in loud and clear, but when the car is running and especially with the AC, the static overpowers the signal.
I've put a new alternator in and that seemed to help very little. I've also replaced the spark plugs with resistor plugs to help.
Any ideas as to what else to try?
Oh yeah, the radio is not stock. That one gave out several years ago.