It sounds like you plan to have the service installed at home and then use it in the RV as well. That's the best case scenario if that's your plan as you don't have to work about turning service on and off. You just move the receiver(S) from home to RV when necessary.
The issue comes up with the type of receivers you decide to use at home and the type of antenna that would be required in the RV. If you can afford a $1500-$1800 antenna for the RV you can buy a Winegard Trav'ler for Dish or DirecTV and you will have the exact same antenna on your RV that you have on your roof at home.
If not that then the choice of portable automatic domes or a home style antenna mounted on a tripod become your choices. How often and for how long you plan to use the RV makes a big difference. Look around the forum and see what you think. My battery is going dead so I gotta go!!