Above the roof in such a manner that reception is not blocked by the roof or house in the directions of , north west , north , north east , install a ANT751 antenna aimed at about 350 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
As always , the starting antenna aim direction is the --> starting antenna aim direction.
The antenna aim direction can be adjusted to provide the best reception.
Most Digital Tv's have a signal strength meter and some Digital Tv's have a signal quality meter.
The ANT751 comes with a J type antenna mount and is not much money at ,
http://www.solidsignal.com ,
http://www.amazon.com.
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No preamplifier is required.
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For 1 Tv connected use no splitter.
For 2 Tv's connected use a common simple 2 way splitter.
For 3 Tv's connected use a common simple 3 way splitter.
For 4 Tv's connected use a common simple 4 way splitter.
As always , trees and tree leaves do a real fine job of reducing or blocking Digital Tv reception and so do buildings and other obstructions including your own house.
It is best to install the ANT751 antenna at a location and height that has the least amount to no amount of obstructions of any type or kind in the directions of reception including your own house.
The Tv/s Must Channel 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.
Digital Broadcast Tv tuners can develop - Digital Glitches - that are not cleared out with a simple channel scan.
Do a Double channel scan.
http://www.fcc.gov/rescan.html.
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DO NOT channel scan for cable tv channels.