What was the antenna connected to back there? My HU also has no antenna connection (2009 ML) and for the life of me I can't find anything in the back of the vehicle that is the FM antenna! I have tried disconnecting every visible coax connection in turn while the radio is on, and none of them affects the FM sound. I have seen mention of an antenna amp (or booster), but I can't find one. Does your car have one? If so, what does it look like?First, the radio antenna connection is in the trunk. There was no antenna connection on the back of my old HU. I have to run a cable from the new HU to the trunk and swap the antenna from the AGW to it.
BTW, what is the "audio gateway", AGW?