The easiest way to explain this is there are seperate lines that run to the roof mount. One line for the bedroom and one for the living room. In order to find the correct lines, consult the placard on the door. This will explain which one goes to the roof(for living area) and goes to the living area, and so on.
If you are putting your dish outside, you will only need to use the line going into the coach (marked on the placard).
Hope this helps.