I finally got to hear HD Radio (a.k.a. IBOC) on several Boston FM's
Saturday night (but not any AM's since it was night). My observations:

1. HD Radio does not sound appreciably better than FM.

2. On some of the stations there was a "gritty" quality to the sound
reminiscent of an MP3 Internet stream. To be fair, this could have
been the result of cascading HD Radio with an STL or digital audio
storage system employing something like MPEG or apt-X compression,
and not something inherent in HD Radio itself.

3. HD Radio does not appear to extend a station's coverage. On the
fringe of one station's coverage, where it could be heard in analog
FM imperfectly, the HD Radio was generally not audible at all. We
estimated that the effective range of the HD Radio signal is 90 to
95 percent of that of the analog FM.

4. The Kenwood receiver seems to mute in digital mode if there is
another signal on an adjacent channel.

5. It also mutes in the presence of nearby FM transmitter sites.

6. In analog mode, the digital sidebands of a station running HD
Radio can be heard as white noise. It is not yet possible to
guess how much interference they may cause because only a few
stations are running HD Radio yet.

7. The scrolling text display some stations were running may be a
considerable distraction to drivers.

After hearing some glowing reviews, I was prepared to hear something
approaching the sound of a CD and to want to push to put it on
our stations. Instead, my friends and I were asking ourselves why
anyone would want to pay $75,000 for it.

However, I am still reserving judgment. One night of listening on
one radio isn't enough; I want to hear it on several different
radios on a wider variety of stations, under different reception
scenarios. I'm particularly interested in the effect of adjacent-channel
interference.


umar