XM and FM volume levels are equal. When AM is selected the volume is about 1/2 and not clear
Radio volume on 2008 Hyundai Santa Fe
This may be an antenna issue, but no matter, I would take this to the dealer and see if they have run into this issue. It still may be under warranty as well. Make sure the dealer checks all technical service bulletins and other technical info from Hyundai regarding radio issues. Sometimes these things are fixed by adding new software to the vehicle, and this is best done by the dealer on a vehicle this new.