The -->Most Likely<-- cause of losing reception a little at a time is , Weather--> Water damage.
Water get's Into the Connections and Water get's into the Coax.
Water can also get into the coax connection of the CM4228HD antenna.
If so , some spray contact cleaner , inside the connector of the CM4228HD antenna will blast any water out and clean it out.
Unless there is a lot of water damage.
And Yes water can get into the inside of the coax where the connector is installed on the coax , Water damage inside the coax means the coax is Not Any Good.
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As a Test.
To Prove Reception.
Connect a -->New<-- continues length of coax to the CM4228HD antenna and run the New loooong coax through a open door or window , Direct to the Tv.
No coax grounding coupler , No couplers , No splitters , No amplifiers , No electronic devices , No nothing.
It is the , CM4228HD antenna , the New coax , the Tv.
For outside coax and connectors use the coax that has the Compression type connectors , not the Old crimp type connectors on the ends of the coax.
And to make double sure that water does not get in outside connections and coax use Coaxseal. Wrap the connections and along the length of coax with coax seal.
http://www.coaxseal.com.
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Install the CM4228HD -->Above The Peak of the Roof<-- in such a manner that reception is not blocked buy the roof and house in the directions of , north , north east , north west , south east.
Aim the CM4228HD at about 349 degree magnetic compass direction , Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Attics Are Not a reception friendly environment and Never Will Be a reception friendly environment
Signal attenuation , Electric/electronic interference , Multipath/reflections- signals bouncing all around in the attic.
That said , the Tv reception is strong signal strength at your location you can try the CM4228HD antenna in the attic.
---->However.<----
If you install a Metal roof , A Metal Roof means that the metal roof Will Disrupt and Block most of the Digital Tv reception with a Tv antenna in the attic.
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Digital Broadcast 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.