You may not know what Antenna TV is. I certainly didn't. It turns out that it's not a separate, standalone cable channel, but something that existing channels subscribe to, most likely on the higher-end frequency. (If you're not aware, many channels have these additional digital frequencies that have separate programming from their standard channel.)
For instance, in Los Angeles, it's listed as showing on KTLA. Now, normally, KTLA is channel 5. But on Time-Warner, Antenna TV programming airs on KTLA's 5.2 frequency, which is channel 1258. Bizarre and confusing as this many sound, it's actually pretty basic -- albeit bizarre and confusing. Other cable systems in L.A. show it on their own KTLA Antenna TV channel. Cox, for instance, has KTLA 5.2 showing on channel 815.
To make this much less confusing, just go to this page here to find where Antenna TV is shown in your area. There's an interactive map of the U.S. you can click on, or just scroll down a list. Not every city or even state get Antenna TV, but there's fairly wide coverage, especially east of the Mississippi River.
One note: if you click on the map for your city, a tiny window will pop-up with a channel. (For example, in Los Angeles, it will say "KTLA.") But don't accept that as the answer. Look directly below the map, where a large blue box will display the correct channel number for each cable system available. It will also show the frequency, but that's not really important.
Here's this is what I mean. This is what that part of the page will look like if you had clicked on the dot for Los Angeles --