The DB8e covers UHF stations, real channels 14-51. The Y10713 covers VHF high, real channels 7-13. The preamp combines the signals from the two antennas. With just one or the other, you could connect the antenna directly to the TV. With both antennas: instead of the preamp, you could use a passive combiner called a UVSJ (UHF-VHF splitter-joiner). They are cheap -
http://www.solidsignal.com/pview.asp?p=uvsj
If you want just one antenna that covers both UHF and VHF-high, you could possibly use the Antennacraft HBU55 or HBU44. The combination above should be superior though.
If you want to go higher from the ground, telescoping masts are available that will go much higher than the fence. Take a look here -
http://www.antennapartsoutlet.com/ You can also use the house to help support the mast without going up on the roof. Look at eave mounts and wall mounts.
Aiming through trees is a problem - look at "Trees and UHF" here -
http://www.hdtvprimer.com/antennas/siting.html