Your signals are strong at your location and are possibly overloading the amplifier in that omni antenna you bought. Omnis seldom work well, anyway, except for receiving channels equally poorly in all directions.
IF your channels of interest are those in green and to the South of you (mostly at the top of your TVFool "digital" option), this simple passive antenna aimed to the South, is all you need.http://www.walmart.com/ip/RCA-Suburb...-Mast/10828410
If you want more than the main network channels to the south, you may need something larger and probably a rotor, too. One of the larger antennas in the Winegard 769 series would be good. http://search.solidsignal.com/?x=0&y=0&q=769
For what you'd gain, it's probably not worth the effort or expense, though.
The Winegard 8200u is ridiculously large, due to the fact it has old-school elements tuned for lowband VHF. Your only lowband VHF chs are:
If those channels are of no interest to you, I would not even consider that antenna.