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The Situation/Problem Most likely is , Multi-Path Reflections Tv Signals Bouncing All Around off of trees and buildings including your own roof and building and etc. .
Get the ANT751 antenna , Up In The Air.
The less obstructions to no obstructions in the directions of reception and the surrounding area the better for reception.
Including your own roof and building as a obstruction to reception in all directions of reception.
Get the antenna Up In The Air clear of obstructions in all directions.
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Digital Broadcast 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.