Audio Systems: No am on my am/fm/cassette/cd stereo, car antenna, tunners

Question
We have an audiovox gc-600 installed in our RV it plays cd's and cassetts ok and we receive FM Ok, but we cannot get any am stations no matter what location we are in.  If we turn the volumne all the way up, we can hear a faint sound and a lot of static.
We are about to trash this radio, but we don't want to buy a new one and fid out it is the antenna after all.  How can w test it to find out what is wrong? thanks for any help you can give.

Answer
HELLO
go the the auto parts or wallmart and buy a 10.00 car antenna
pull the radio out unplug the old antenna and plug the new antenna  

but audiovox have bad tunners and i seen this problem before when the tunner dies and it only plays cd or tapes