Kirk, please tell us what RV you have. (It's best to put that information into your profile and/or signature.)
Usually the "outside cable connection" is wired to the back of the Winegard rooftop antenna booster control (see picture).
You have to disconnect the Cable Input from the back of that and connect it directly to the Tailgater. In some RVs they have inserted splitters into that line as well. Tailgater can't be used with any splitters.