Smart Antennas are directional antennas that are "smart" because they automatically rotate to the proper direction depending on the location of the channel you’re watching. The smart antenna works best if used with only one TV and converter box at a time, because the “smart” technology is designed to capture the best signal for the TV that is plugged into the smart antenna port (EIA/CEA-909 interface).
Technically you CAN attach more than one TV to the smart antenna. But, if you use a splitter to attach a second TV and Converter box, your smart antenna will only adjust itself to accommodate the first TV. So you may experience sub-par reception on your second TV when viewing stations from a different direction than the first TV.