2006 GP GT Radio Issue with AM Band

Here I am with another GP issue. Just bought a used '06 GP GT with Supercharged 3.8L and 80000 miles. Has a Monsoon radio speaker system. FM1 & FM2 reception is great, CP player works well and sounds great as well. Issue is that there are only a couple of AM stations that I get reception on and those are very weak. AM reception locally on my '01 GP SE is fine on numerous local stations. Can a radio loose reception on only 1 of 3 bands? If not, where should I look next? Antenna cable seems to be plugged solidly into the radio. Balance and Fade features on radio seem to work OK. Never had a radio in any car have a problem like this. These GP's seem to have some odd issues. hanks in advance for any advice or suggestions.

If I remember correctly, there is an antenna module with a ground connection on it(screw).......it is located in the rear edge of the headliner near the center....I think ther are two plastic retainers in the headliner near the rear window......remove, lower the headliner a little and you can feel the module.....have an AM station on that you should be able to receive...it will be weak or static...reach up there and move the module or tighten the screw and I think you will hear a difference....

Thanks for the info. I'll check that out and let everyone know if that's the problem. I've never had a radio issue like this but knew there'd be someone out there that has. That's the amazing thing about this web site. That and the fact that people actually are willing to take the time to help complete strangers.