Even if can not get above the tree , Higher Is Still Better.
Install a bigger antenna , install a Winegard HD7698P antenna.
Aim the HD7698P antenna at about , 261 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 , ronard(911) 5 foot antenna mount.
http://www.ronard.com/Tripods%200703/4712.html.
http://www.ronard.com/ychim.html.
Measure the Chimney and use a , ronard(2212) , ronard(2218) , ronard(2224).
Buy the ronard antenna mounts at solidsignal by typing , ronard(x) , in the solidsignal search box or by from ronard.
Here are some places to buy antennas and etc. .
http://www.solidsignal.com.
http://www.amazon.com.
http://www.winegarddirect.com.
http://www.ronard.com.
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Test reception without and with the preamplifier.
When Test reception without the amplifier , Disconect and Remove All Parts of the amplifier , the preamplifier unit , the power injector , the power supply.
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Look for a way to install the HD7698P antenna at a location that is not blocked by the tree/s the direction of reception.
Or has the Least amount of tree/s obstructing reception.
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Digital Tv Tuners can develop - Digital Glitches - that are not cleared out with simple channel scans.
Do Double Rescan ,
http://www.dtv.gov/rescan.html.