Get one that works on the legacy cabling. If it is SWM only you will have to change the RV's cabling to SWM. I have a
D12-100 in my RV. It does not require SWM, although it is compatible with it.
To change the cabling to SWM, you would need a
SWM8 and a
Power Inserter (PI). The receiver's coax goes into the PI. The PI's coax goes into the SWM8. The SWM8's coax goes to the antenna. The PI requires a 110v outlet.
ON EDIT: you will also need to run 2 coax cables to the antenna from the SWM8 or you will only get half of the channels. Either the even or the odd transponders, but not both.