The hardest thing to grasp about digital TV is the "Virtual channel" concept. As stated previously, the channel that is displayed on the TV set most likely has no relationship to the "real" or "RF" channel being broadcast by the TV station. Most TV stations are now broadcasting on the UHF band (channels 14-51) and a few on the high VHF band (channels 7-13). The low VHF band (channels 2-6) has for the most part been abandoned. Channels 52-69 have been sold off for other uses.
Most of the major TV markets will have at least one or more TV stations broadcasting on a VHF channel. The Jack antenna does an adequate job for UHF but works poorly for VHF. This is one reason why the Jack antenna is a poor choice. The Winegard works much better for VHF and with the Wingman attachment is on par or better than the Jack for UHF.
The easiest way to check what the actual or RF channels being broadcast in your area are is to go to a web site such as:
TV FoolAntennaPointAntennaWeb