I have both a Jack and a Winegard Sensar with the Wingman attachment. Overall, the Winegard surpassed the Jack.
Most TV stations today broadcast using the UHF channels (14 through 51), but there are a few that broadcast on Hi-VHF (7 - 13) and a very few broadcast on Lo-VHF (2 - 6). These channels are the RF channels, not to be confused with the channel number displayed on your TV set which is the virtual channel number. If you go a web site like
http://www.antennapoint.com/ and search for TV transmitters, it will list both the RF channels and Virtual channels.
The Jack and Winegard with Wingman perform about the same for UHF channels, but the Winegard does much better for VHF.