Remember you may not need some fancy "HDTV antenna." Technically there is no such thing. It's just two pieces of metal grabbing electrical impulses out of the air. Some do have boosters. A cheapo $10-15 one will tell you if you can get any kind signal then if you can you may need to get one with a booster. Make sure the store has a return policy if it won't work, most bigger ones do.

The HD signal is somewhat directional, you may find moving it just a few feet will make a difference. It is kind of "line of sight" but not like satellite TV.