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The Signal Strengths are Very Strong Signal Strengths at Your Reception Location , the Transmitters are Close , and are LOS=Line Of Sight.
Even So , Attics and the Inside of Buildings Are Not a Reception Friendly Environment and Never Will Be a Reception Friendly Environment.
Yes Start with Antenna in the Attic , If Reception Situations Happen in the Attic that Are Not Resolved with Antenna Aim Adjustments and Antenna Location Adjustments , Then Move the Antenna to Above the Peak of the Roof.
The Smallest antenna I can recommend is a ,
http://www.antennacraft.net.
HBU11K antenna aimed at about 74 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Use a Real and Actual magnetic compass to aim antenna , do not trust a cell phone , tablet and etc. 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 2 way splitter.
For 3 Tv's connected use a 3 way splitter.
For 4 Tv's connected use a 4 way splitter.
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As a Test to Prove Reception.
Connect a New Continues Length of Coax to the Matching Transformer (Balun) that is Connected to the Antenna.
And Run the New Continues Length of Coax Direct to 1 Tv , No couplers , No splitters , No etc. .
Direct to the Tv.
