The best RV antenna (something designed for an RV) is the Winegard Sensar IV with a Sensar Pro inside (Not required but an awesome add-on). Your coach might not have room on the roof for this antenna but it is indisputably the best (except for the few uninformed that will dispute this)!
I am not sure why, but TV reception is one of those things that RVers are extremely, over the top, passionate about. You are going to get many answers so it's going to take a bit of work on your part to separate the wheat from the chafe but if you get confused, refer back to this post.
:p