Since FM HD in its current form will likely survive it's very, very
unlikely AM HD will fail. Since both systems were hatched by iBiquity
they will both be force fed to the consumer untill such a time, in the
future, when the FCC sets a date for the end of analog radio. There
will be no FM HD without AM HD ....period.

And this will happen. There will be no turning back.

So all of us who have loved traditional radio are out of luck. It's
that simple. The days of listening to a distant station coming via
the ionosphere are over - at least on the standard broadcast band.
There will be no more 50KW blowtorches and AM radio will essentially
become all local.

It's sad to see another pleasant thing pass due to out-of-control
technology.