2006 sonata, avic d1, am reception

Try unplugging the antenna from your radio. See if you still have any noise on AM from these items. I realize that you won't get any reception, but you need to determine if the noise is creeping into the system or through the ground or other wiring. Use a digital ohm meter and measure the resistances in the antenna cable. The outer shield of the antenna should have less than 0.5 ohms resistance to ground. You should have less than 0.5 ohms resistance from the center lead of the antenna at the radio to the antenna mast. There should be no continuitity between the center conductor and the shield. It is also possible that these cars may use an amplified antenna of sorts. It may have to be powered in some fashion. Make sure that your radio has a good ground to the chassis too. Don't use the factory ground wire in the radio harness. sparky