If you have an HD television, the converter box is built in.
You
may need a pre-amp depending on your location relative to the stations you're trying to get, but if it worked once before it should work now.
This site (
http://www.antennaweb.org/) will help you figure out what stations you can get in your area if you don't already know.
I live way out in Winston County and I pick up CBS, ABC, and NBC out of Birmingham perfectly fine, and I could get FOX if I cared enough to try. All we have is a small antenna the size of a sheet of paper. Granted, sometimes I have to tape it to a pole and hold it way up close to the ceiling, but still. When I lived up on Sand Mountain above Scottsboro, I had an antenna like the OP is talking about and a pre-amp, and I got all the Huntsville and Chattanooga stations just fine. I was running it through an existing cable TV setup (I wasn't paying no dang cable company for free TV) and it worked just fine.