A 2 antenna system is , Channel Surfing Friendly , Push the button on the hand held remote control and change antennas and keep on watching Tv.
Here are some roof top antenna mounts ,
http://www.ronard.com/909911.html ,
http://www.ronard.com/34424560.html ,
http://www.ronard.com/ychim.html ,
http://www.ronard.com.
Buy the ronard antenna mounts at solidsignal by typing the word ronard in the solidsignal search box.
Here are places to buy antennas and ect. ,
http://www.solidsignal.com ,
http://www.winegarddirect.com ,
http://www.amazon.com.
The Tv must scan for The Broadcast Tv Channels sometimes named the 'Air Channels' or 'Antenna Channels' in the Tv setup menu because the Tv transmissions travel through the air from the transmitting antenna to the receiving antenna.
Do Not scan for cable tv channels.