Greetings! I have been experiencing radio interference for over a year and I am now reaching out for help online.
I have the factory installed Honda Accord 2003 6 cd changer radio. When I start the car the AM signal is fine. After driving for 5-10 minutes I start getting interference. If I turn the radio on and off it sometimes corrects the problem. However, the interference eventually becomes to much and I loose the station. FM seems fine. I tested a portable AM/FM radio and I also experience the same interference.
The interesting part is that when I turn off the engine, the interference clears up immediately for both the car and portable radio.
I also have an XM Radio installed. I did unplug it with no noticeable change in interference.
Sorry for the long post but I wanted to provide as much information as I could.
Any suggestions would be greatly appreciated!

 

Easiest thing to do is unplug the factory antenna and plug an aftermarket antenna in and see if there is a difference in performance. If so the factory antenna is the problem if nothing changes the decks tuner is the problem (I've personally seen people have a number of different issues with these decks). If you don't have install experience I wouldn't attempt to remove this radio, it is a finiky procedure, I can tell you this through experience with this car. An experienced shop should only charge an hours labour to do this test.