Above the roof in such a manner that the roof or the house does not block reception to the , north west , north east , east , install a Winegard HD7000R antenna aimed at about 311 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Here is a antenna mount that does not make holes in the roof ,
http://www.ronard.com/34424560.html if using a eve antenna mount then use the #4560 ,
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 antennas and etc. ,
http://www.solidsignal.com ,
http://www.amazon.com ,
http://www.winegarddirect.com.
Universal J type antenna mount , type , DS-3000 or DS-3000-SSCBLS050 , in the solidsignal search box.
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No preamplifier is required.
For 1 Tv connected use no splitter.
For 2 Tv's connected use a common simple 2 way splitter.
The Tv transmissions are strong signal strength , 70 or more feet of coax is OK.
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As always , trees and tree leaves do a real fine job of reducing or blocking Tv reception and so do buildings and other obstructions including the roof and house.
It is best to install the HD7000R antenna at a location that has the least amount to no amount of obstructions in the directions of reception of any type or kind including the roof and house.
The Tv/s Must channel scan for the Digital 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 channel scan for cable tv channels.