There is no such thing as a HDTV antenna. What you are talking about is the Satellite dish, its likely a triple LNB. I do not think that one is compatible with Dish Network's receivers. But if you switch to Dish Network, they will likely swap it out during the free installation. They might even be able to re-use the pole.
Finally, this is a regular dbs question, not an HDTV programming question. Wrong forum.
Finally, this is a regular dbs question, not an HDTV programming question. Wrong forum.