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Does reception improve with , Antenna aiming changes , mounting heights changes , antenna location changes.
Aim the antenna at about 65 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointong/pointing.html.
Use a Real and Actual magnetic compass to aim antenna.
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Also.
Digital Tv Tuners can develop - Digital Glitches - that are not cleared out with simple channel scans.
To clear tuner do Double Rescan.
http://www.wchstv.com/DoubleReScanAlert.pdf.
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As always , trees and tree leaves , plants and plant leaves , have a Negative Effect on Broadcast Tv Reception including your own roof and building.
Some and not all Negative Effects are
Absorbing , Blocking , Reception
Multi-Path Reflecting signal bouncing all around.
Install 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 building.