Tom,
WBBM is northwest of Chicago; I would guess that you go south of the 
city perhaps coming in on 80/94 and maybe continuing on 80.  So you'd 
never have quite gotten close to the station.  At work in my former 
office the station would go in and out of H D and drove me nuts, 
although that is a short trip!  Now I am in a different office and 
the signal is stable.  The point of digital for voice eludes me, though.
pat, K9JAUAt 06:02 PM 8/26/2013, you wrote:
>Steve:
>
>I checked wbbm A M again today on either side of the Chicago area.
>
>I need to do a bit more careful checking with milage, but I would say as a
>rough estimate that I really had to be within about 40 or so miles of
>Chicago before the digital a m signal stabilized, and this was in the
>day-time.  I can only imagine that, at night-time, the situation would
>worsen.
>
>The thing is that I can't believe others don't notice that too, which does
>the whole digital A M possibility a further dis-service.
>
>Anyway, these are just my views, of course, and I'll try to do some more
>checking with some other stations in other markets as my trip proceeds.
>
>Tom Behler: KB8TYJ
>
>
>-----Original Message-----
>From: For blind ham radio operators [mailto:[log in to unmask]]
>On Behalf Of Steve Dresser
>Sent: Monday, August 26, 2013 10:37 AM
>To: [log in to unmask]
>Subject: Re: Speaking of Digital:
>
>Tom,
>
>That's exactly the problem with HD radio on AM, and even on FM to a lesser
>extent.  You may very well discover that your radio doesn't have a means of
>keeping the HD turned off, which in my opinion is an absolutely essential
>feature for listening on the AM band.
>
>I'm afraid that HD on AM will end up like AM stereo.  It will eventually
>disappear due to lack of interest.
>
>Steve
>
>----- Original Message -----
>From: "Tom Behler" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Sunday, August 25, 2013 14:51
>Subject: Speaking of Digital:
>
>
> > Hi, everyone.
> >
> > The ongoing discussion regarding D Star, and audio quality reminded me of
> > something I recently experienced, and meant to bring up to the list.
> >
> > As many of you may recall, the XYL and I recently purchased a new vehicle
> > that has an HD radio in it.
> >
> > Well, thanks to the help of some on the list regarding how best to
> > understand and use the new HD capabilities while traveling, I believe I
> > have
> > mastered the main functions of the radio pretty thoroughly now.
> >
> > However, I have to say that digital A M leaves a tremendous amount to be
> > desired, in my opinion.
> >
> > For example, while traveling through the Chicago metro area from Michigan
> > on
> > our way to and from the St. Louis area several weeks ago, I tried
> > listening
> > to WBBM  AM 780 with the new digital radio, and the experience was
> > actually
> > quite anoying.  I'd say that as we got 30 miles or so on either side of
> > Chicago, the digital AM signal kept switching on and off, to be replaced
> > by
> > a much degraded analog signal.  Perhaps there is a way to turn the digital
> > AM reception mode off in this particular radio, but I have not found it
> > yet.
> >
> > We are going to be traveling through quite a few metropolitan areas on our
> > upcoming family visitation trip, so I'll have time to play with it a bit
> > more, but I really am wondering now about the usefulness of digital AM
> > radio.
> >
> > Tom Behler: KB8TYJ
> >