Check out these sites:
Input your address, and locate / find the television transmitters in your vicinity, their distance from you, and recommended classes of antennae:
At the above site, "AntennaWeb":
Maximize your television reception
The AntennaWeb.org mapping program, provided by the Consumer Electronics Association (CEA) and the National Association of Broadcasters (NAB), locates the proper outdoor* antenna to receive your local television broadcast channels.
Based on geographical maps and signal strengths, AntennaWeb locates the best antenna for you — whether the antenna is for use with a home satellite system, high-definition television (HDTV) or a traditional analog set.
A blogsite, with recommendations for converter technology:
High Def Forum: