Aim the antenna at about 85 degree magnetic compass.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing.html.
Here are some above the roof antenna mounts ,
http://www.ronard.com/909911.htrml ,
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 some places to buy reception equipment and etc. ,
http://www.solidsignal.com ,
http://www.amazon.com.
Remove the Plasma Tv and connect a different Tv and see if the same problems happen.
The Tv/s 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.