I use a Winegard Pathway II caryout auto dome.
It only works for DISH and it does HD.
It "sees" eastern or western arc which can be great when there are lots of trees.
DISH uses three sats and while the Pathway only sees one sat at a time, if you select a channel that is on a different sat, it will change and change so fast you wont notice.
The limitation is that the second sat box can only watch channels on the sat that the first box is on.
This has never been an issue for us.
Buy one or two Wallys and leave them in your rv.
I am very happy with ours.