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If the roof is a metal roof the signal will be reduced and blocked.
Up High in the vaulted ceiling install a ,
http://www.antennacraft.com ,
HBU11k antenna aimed at about 100 degree magnetic compass direction.
Here is how to aim antenna ,
http://www.kyes.com/antenna/pointing/pointing.html.
Use a Real and Actual magnetic compass to aim antenna.
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Digital 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