As a Test to prove reception one way or the other.
Aim the antenna at about 99 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Connect a New continuous length of RG-6 coax to the antenna and run the New continuous length of RG-6 coax through a open door or window direct to 1 Tv.
No coax ground blocks , No couplers , No splitters , No passive or active devices.
It is the , antenna , the matching transformer (balun) , the coax , the Tv.
Digital Tv tuners can develop - Digital Glitches - that are not cleared out with simple channel scans.
Do a double rescan ,
http://www.dtv.gov/rescan.html.
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As always , trees and tree leaves , plants and plant leaves , produce a negative reception situation , multi-path/reflecting , absorbing , blocking , Tv reception , and so do buildings and other obstructions including your own roof and building.
The best practice is to instal the 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/building.