I just got cable last year. I have tried everything and almost am expert on that subject. Now that I have tooted my own horn...
Go to Radio Shack, don't get a used one, they corrode and lose there efficiency, the model number of there antennas ralate to the number of miles it is rated for. Get the biggest one they have, I think it would be an xxx-120. Get an amplifier also, they are a two piece unit, half of it goes up on the antenna and the other part plugs into a 110 outlet behind the TV. If there are citys all around you you want to 'see', you should also get a rotor.
The height of the antenna is not critical. I had one seven feet off of the ground that worked just fine. Alot has to do with your average elevation. How hthe ground aroud you is. If you live in a deep vally you need height, if you live on a hill you won't.
The area I live in is rural. Rockford, the closest city (30 miles) has 5 t.v. channels. After I put together this setup, I would routinely receive channels from Chicago, Millwaukee, Quad citys, Madison, even Indianapolis on occasion.
Sorry for the long letter, I hope this helps.