To return to the thread of this discussion... at least briefly... WSCR 670 and WBBM 780 both appear to have their IBOC turned off at the moment. I thought maybe it was just for a game, but it has persisted overnight and this morning. Both sound so much better without the annoying hiss in the background!! Enjoy it while it lasts....
Both off all day Sunday, and still off when I went in to work tonight.
Listened to wonderful old stuff on WSM all the way to work.

A quick check now still shows no iboc on either.
You are far removed from WSM's protected contours....
http://radio-locator.com/cgi-bin/pat?call=WSM&service=AM&status=L&hours=UHonk, Honk. Honk Honk!
Your idea of radio is a weak, small-minded little concept, and far outside the protected contours of the laws of physics.
You can try all you want, but skywave is real, and doesn't respect any definitions or excuses that it "ought not exist".
You are still free to create as much interference to the public airwaves as you can get away with.
Have fun at it, you wild-n-crazy guy, you.
HD on AM is about as effective as the glue used in the roof panels of the "big dig".
"But they said this glue would work!"
Unless of course the idea is to trash the service, then it's doing a pretty good job.