1080i broadcast, KSL TV (local news) note: jaggies on collar (click to enlarge)

The picture to the right shows a close-up of the anchor in a local newscast from KSL-TV (channel 5 in Utah). The broadcast is advertised as 1080i (e.g. my TV claims it's a 1080i signal based on the info in the signal). If you look closely, you'll see that the collar (a nice, high-contrast diagonal line) has jaggies--stair-steps in the collar instead of a smooth line. You can see them very clearly.

1080i broadcast, KSL TV (national news) note: collar is smooth (click to enlarge)

The second picture shows another broadcast on KSL-TV a few minutes later. This broadcast, of the news anchor on the Today Show (NBC's national morning show) is also allegedly 1080i as reported by my TV. If you look closely at the collar on the anchor in that broadcast, you'll notice that there are no jaggies. In fact, the national broadcast is clear as a bell.

In both cases, I was viewing the program from an over-the-air HD signal directly into the back of the TV. Also, this isn't an artifact of the camera. These pictures accurately represent what can be seen with the naked eye.

This behavior is consistent. I can view any KSL local news cast and see the jaggies. I can view any NBC national news program on the same channel and they aren't present. The TV reports 1080i programming in both instances.

Here's my question: why? Is the local broadcast not really a 1080i signal or is the signal 1080i, but something in how it was captured or processed not as high definition as the broadcast itself? I'm leaning toward the latter explanation, but I don't know anything about it. For example, maybe they're shooting with lower resolution cameras? I'm just guessing. Anyone from KSL want to comment?

I guess the third possibility is that my TV is messed up, but I don't think so. Steve Fulling has a 52 inch version of the same TV and reports the exact same phenomenon.