Here the Federal Antenna Law that says Yes you can install antennas above the roof in such a manner so as to have Reliable Tv Reception.
http://www.fcc.gov/mb/facts/otard.html.
Install a Winegard HD7000R antenna above the roof in such a manner that the roof and house and garage do not block Broadcast Tv Reception to the , south west , south , south east.
Here are some above the roof antenna mounts ,
http://www.ronard.com/909911.html ,
http://www.ronard.com/ychim.html ,
http://www.ronard.com/34424560.html if using the eave mount use the #4560. ,
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 some places to buy antennas and etc. ,
http://www.solidsignal.com ,
http://www.amazon.com ,
http://www.winegarddirect.com.
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Use no preamplifier.
For 1 Tv connected use no splitter.
For 2 Tv's connected use a simple common 2 way splitter.
For 3 Tv's connected use a simple common 3 way splitter.
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As always , trees and tree leaves do a good job of , reflecting , reducing , blocking Digital Tv reception and so do buildings and other obstructions including your own roof and house and garage.
It is best to locate the antenna at a location that has the least amount to no amount of obstructions of any type or kind in the directions of reception including your own roof and house and garage.
The Tv's Must Channel Scan for the Broadcast Tv Channels , often named the 'Air Channels' or 'Antenna Channels' in the Tv setup menu because the Tv transmissions travel through the air from the transmitting antenna to the receiving antenna.
Some Digital Tv's will automatic channel scan for cable Tv channels.
Go into the Tv setup menu and select , 'Air Channels' or 'Antenna Channels'.
DO NOT Channel Scan for Cable Tv Channels!!.