Check the antenna , see if the antenna matching transformer (balun) is making the connection to the antenna wires inside the plastic housing.
A way to test reception is to bypass all coax.
Install a Known to be good looong coax connected directly to the antenna and run the coax through a open window or open door directly to the Tv.
Here are some above roof top antenna mounts ,
http://www.ronard.com/909911.html ,
http://www.ronard.com/34424560.html ,
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.
Here are places to buy antennas and etc. ,
http://www.solidsignal.com ,
http://www.winegard.com ,
http://www.amazon.com.
Also install a Winegard AP8700 preamp.