If you have a directional antenna and want to pull in weak stations from opposite directions, you can use a rotor to turn the antenna towards the broadcast tower of choice. Cost $55 ~ $150.

Rotor Options:  
• CM-9521
   - from Channel Master
   - available from Crutchfield
• SDW1850/17
   - from Philips
   - available from Walmart
• VH126N
   - from RCA
   - available from Walmart
• TDP-2
   - from Antennacraft
   - available from Solid Signal

Multi-directional antennas like the DB8e and HDB8X have sections that can be aimed in different directions, thereby negating the need for a rotor.

TIP: It might be less expensive and simpler to install 2 separate antennas pointed in different directions than a single antenna with a rotor. This arrangement permits 2 TVs to receive broadcasts from New Haven and Springfield, for example, at the same time. The second antenna can sometimes share the same mast as the primary antenna or could even be mounted indoors or in the attic. You can use a coaxial switch to toggle between 2 antennas.