HD Radio Update
The call confirmed my suspicions about the role location plays in my ability to get digital signals. I learned about a few things that could help. I'll try them out and report back.
I also learned that one of the digital clocks in the unit can interfere with signals around 88.1 and 88.5 if the signals are weak in the first place. That seems to be the source of the digital chirps I get when trying to tune to WAMU (88.5FM). That's a good piece of information for public radio people to have.
I realize the engineers probably know all this stuff. Stations would do well to start educating all staff members on the consumer issues around this new technology. You never know who at your station might come in contact with someone who needs help with HD Radio. Perhaps each station could have an in-house FAQ available to staff members.
But the best part of the call with Boston Acoustics was this; they not only called to help me with my radio, they also were trying to learn how to make their product better. If only every customer service experience could be that good.