BSO on the radio - not for me anymore
Tue Oct 12 10:41:55 EDT 2010
> As for HD, I have a Pioneer stereo with the add-on HD receiver. It sounds great
> especially on AM. The big problem is range. I lose about 20% compared to analog.
> HD-2 is about 50% and HD-3 is close to 30%.
To clarify that: you are not losing range. The HD signal reaches
about as far as the protected service contour, sometimes a little
further. Sometimes a lot further if the station has increased digital
injection from -20dBc to -14 or -10. A better way to think of this
is that analog signal gives you a bonus well beyond what you, as a
listener, are supposed to get.
As for the differing ranges on HD-n vs. HD-1 (the analog simulcast)
that's an oddity but a known one. First is perception; when the
digital signal drops below useable levels, for HD-1 it blends back to
analog. For HD-2 (or -3 or -4 or -n) it just mutes. The problem,
IMHO, is that the system tries too hard to always put audio out there,
even in a fringe area. So you get blips of audio and short periods of
muting...the most frustrating kind of reception. But with HD-1, it's
somewhat less noticeable because a well-engineering plant can make the
digital/analog blend nearly unnoticeable.
Second, and equally real, is how the HD-2 and HD-3 are encoded. If
the station in exchange uses the Extended Hybrid mode to gain an extra
24kbps, the rub is that 24kbps can't be combined with the regular
96kbps of the main hybrid. And Extended Hybrid adds digital carriers
closer to the analog center freq, so it can be impacted differently
than the rest of the digital signal. So an HD-n channel in the
Ext.Hybrid datastream can exhibit different perceived quality of
reception than HD-n in the Main Hybrid datastream.
There have also been reported cases where if the HD-2 and HD-3
channels, even if both are in the Main Hybrid datastream, can show
differing perceived quality of reception. I'm not 100% convinced this
is true; it's so easy for perceived quality of reception to be
influence by a host of constantly-changing variables that are
difficult to control for. But theoretically, I could see reasons why
it really would be different. But it'll be different for every
station as every station uses different transmitters, different
antennas, different processing and pre-processing, and different HD
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