[IRCA] IBOC reception

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

I decided to scan through the local AM band to see just how the IBOC
reception is with an ear toward how a listener would perceive it.  Here's a
list of stations I could get.  Radio is a JVC KD-HDR1 and the antenna is a
whip-type on top of an 80' tower.  This sort of approximates a car parked on
a hill and distances it from some of the house noises.

1.  WPRO-630   Decodes OK, audio quality not bad.  Levels close to analog.
Some time sync difference, enough to annoy if it switched back and forth a
lot.  A word syllable is lost or doubled, depending which way it goes.

2.  WHJJ-920   Decodes OK, audio quality not bad.  Levels at least 10db down
from analog.  Can be annoying.  Slight time sync difference, though only
enough to give a slight reverb effect upon switching.

3.  WBZ-1030  Decodes, but switches back and forth.  Levels close, audio
quality OK.  Very slight time sync with slight reverb effect on switching.

4.  WMKI-1260  Today it decoded solidly.  In the past it did switch a fair
bit.  Audio sounded good, levels and time sync also very good.  Only
difference upon switching is the treble comes up which is expected.

5.  WRNI-1290  Here is a surprise.  It's a 10kw station with the pattern
aimed in my general direction.  Probably in the top 5 strongest stations,
certainly way stronger than the two Boston stations previously mentioned.
It did not decode at all.  Nada.  I had it on for maybe ten minutes and
never got a thing.  Tuned back to 1260 and WMKI decoded fine.  I had a
conversation yesterday with another local engineer and I think he commented
that it wouldn't decode for him, either.  So, here is a station causing
interference to the 1280 in Fitchburg, MA and the 1300 in Quincy, MA and not
getting any digital benefits at all.  I have to wonder if their three-tower
directional is the cause.  It may not have been broadbanded.  The spectrum
does look right, however.

There were a number of other IBOC stations where the digital bands could be
seen on the spectrum analyzer display, but not decoded at all.  WTAG-580,
WFAN-660, WOR-710, WNNW-800, WCBS-880, WTIC-1080 and WXKS-1430.  There are
others that are supposedly running IBOC, but I cannot see the sidebands or
hear the hiss.  WGY-810 is supposed to be IBOC, but the signal here is too
weak to even tell.

Craig Healy
Providence, RI



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