Thanks very much for the information.
And, yes, AM-HD sounds so damn good, it's hard to go back to analog - the reason why I asked if anyone knew why WABC was only broadcasting in HD during specific hours. When my HD signal goes out in the afternoon on WABC, I'm tempted to change the radio dial because of how bad the analog quality sounds in comparison to HD. But it's like any new technology - we've all been listening to analog radio for decades...but when something new and better comes along, it's hard to go back. Like black-and-white to color, then cable, then HDTV. It's the age-old question we ask ourselves: "How did we use to live without this?"
I know there's a great deal of dislike towards HD, because of its interference with analog AM. But let me tell you, I might have plunked down $200.00 for my SONY HD Radio, but it's worth it.
Ask someone a few years ago why they paid so much money for their Plasma or LCD television with an HDTV hook-up and they'll tell you it was worth it. I must say, HD Radio is the same thing - if only there could be some improvements, like 24/7 broadcasting.