That could be troublesome since the new DirecTV hardware requires SWM hardware. The SWM hardware is not built into any of the dome style portable antennas or a roof top manually pointed antenna (but can be added). You could use an open faced antenna that you manually setup and point which has the SWM hardware or an automatic roof top antenna like the Winegard Trav'ler without issue.
Do you know what kind of antenna you are planning to use in the RV? Do you want to be able to watch DirecTV HD programming while in the RV?