Most of the Digital Broadcast Tv stations transmitters are Very Close to your location.
Most of the Digital Tv stations/channels are Very Strong at your location and there is A Lot of multipath/reflected Digital Tv reception bouncing off buildings at your location.
The Very Strong Digital Broadcast Tv reception is Over Loading the antennas amplifier and the Strong multipath/reflections is making reception even worse.
Install a Non amplified antenna Up High , Above the Roof.
Install a Winegard HD7000R antenna aimed at about 90 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Here are some above the roof antenna mounts.
http://www.ronard.com/909911.html , use the 5 foot tripod antenna mount.
http://www.ronard.com/34424560.html , use the #4560 eave antenna mount.
http://www.ronard.com/ychim.html.
http://www.ronard.com.
Buy the ronard antenna mounts at solidsignal by typing the word ronard in the solidsignal search box or buy from ronard.
Here are places to buy antennas and etc. .
http://www.solidsignal.com.
http://www.amazon.com.
http://www.winegarddirect.com.
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The Digital Broadcast Tv transmissions and reception is So Strong at your location that I recommend use a simple common 4 way splitter for 1 thru 4 Tv's connected.
The 4 way splitter will reduce the strength of the strong signals.
Put 75 Ohm terminators on any unused output ports of the 4 way splitter.