When reception degrades as time goes by.
It is almost always because of - water - , water in the coax connections , water in the coax , water in the hard ware such as splitter , ground blocks , water in matching transformer (balun) and etc.
Even if the coax does not look like there is water damage to the coax , the coax can still be water damaged. Discard the coax , connections can go bad from water damage.
Discard coax and etc. , replace with new.
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-->Yes I know you are receiving the USA Digital Tv stations.<--
For improved reception , install a Winegard HD7698P antenna aimed at about 170 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
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Use
http://www.coaxseal.com to prevent further water damage , after the damaged coax and connections and hardware has been replaced with new.