CaminDFW

Long time lurker first time poster. Which goes "first" in line? I know that the antenna goes directly into the HD unit. Does it goe ip bus out from the hd to ip bus in to the xm bus out to the head unit or... xm ip bus out to hd bus in to hd bus out to the head unit? I currently have the HD unit second in line and I get hd radio but do not get "normal FM".