[BigBill]

You need to put your street address, city and zipcode only into the box, then answer the two questions at the bottom about trees and such and the house type single story or multi story. Then click submit.
When the next screen shows, the put the radio button in the correct type of stations your are looking for, digital, analog or both. For free HDTV you need to look at digital and you must have an ATSC tuner to pick that up.
The important parts on that screen are the "compass orientation" and "miles from" fields.
The information you get there also tells you what size antenna you might need.
This next site will help you determine the strength of the signal and how high you need to put an antenna to get Line of Site (LOS) for different stations from you house. Hope this helps. http://www.tvfool.com