As Always , attic and inside of building Are Not reception friendly environment and Never Will Be reception friendly environment.
Yes start with a , ANT751 antenna in the attc aimed at about 62 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Use a Old School magnetic compass.
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A antenna system amplifier is Not required.
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For 1 Tv connected use No splitter.
For 2 Tv's connected use a simple common 2 way splitter.
For 3 Tv's connected use a simple common 3 way splitter.
For 4 Tv's connected use a simple common 4 way splitter.
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If reception situation/problems happen that are not resolvable by adjusting aim direction and location in the attic , then move the ANT751 antenna to above the peak of the roof in such a manner that reception is not impeded and blocked by the roof and house in the directions of , North East , East , South , South West.
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As always , trees and tree leaves , plants and plant leaves , have a negative effect on broadcast Tv reception and so do buildings and other obstructions including your own roof and house.
The best practice is to install the ANT751 antenna at a location that has the least amount to no amount of obstructions of any type or kind in the directions of reception including your own roof and house.
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The Tv/s Must Channel Scan for the , OTA=Over The Air , Digital Broadcast Tv stations/channels , often 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.
Some digital tv's will Automatic channel scan for cable tv channels.
DO NOT channel scan for cable tv channels.
Go into the Tv Setup Menu and select , 'Air Channels' ~ 'Antenna Channels'.
Scan for channels.
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Cable delivered services , cable tv , cable internet , cable phone , Can Not be connected to coaxes that are being used as the antenna system.
Do Not connect any type or kind of cable delivered service to the coaxes that are used for the antenna system.
Yes the coaxes that are in/on the house can be used for the antenna system.
However any type or kind of cable delivered service must be on separate coax.
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Here are places to buy antennas and etc. .
http://www.solidsignal.com.
http://www.amazon.com.
Home Depot or Lowes will sometimes have the ANT751 antenna in stock , no matter what the Home Depot and Lowes web sites say.