[IRCA] More IBOC discovery

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

Well, I try to limit comments on IBOC to once a month or so.  Here's a
current bit..

Recently I helped install IBOC at a local AM station (Infidel! Infidel!).
It was a rather interesting and informative job.

We all know about the adjacent channel trash that is put out by design.
What is not publicized are the undesired sidebands caused by mixing products
beyond that first adjacent.  This job had sidebands at around +/-25KHz that
were about 65db down though perfectly legal in the mask that the FCC
mandates.  This makes hearing a third adjacent station in that area of the
transmitter site quite unpleasant.  It does carry a fair distance and is
visible on my home SDR-14.  There were also wider sidebands further out than
that of consequence.  All this IBOC noise is additive and destructive to the
band.

Since a third adjacent can be geographically close, it may be more of an
issue than we realize.  It can raise the overall noise floor.  I have to
wonder if my local 1320 station has damage from local 1290 IBOC which is
24/7.

Another thing that came out of this is that not all antenna systems can be
made compatible.  Night pattern in this place was too narrowband.  The IBOC
carriers were there and as noisy as ever.  The distortion caused by the
narrowband antenna system prevented the receiver from decoding them even in
the transmitter building (!).  Neither of my radios would decode it even a
few miles away.  It just flat out wouldn't work.  The consultant spent a lot
of time on that system and got it as good as it can be.  I'm not convinced
that even all digital mode would work on this system.  The bottom line of
all this is that a significant fraction of AM stations may never be able to
implement IBOC.  Therefore, either all those stations eventually fail or
IBOC in general fails.  Mutually exclusive.  I should also mention that the
labor costs for all this is far greater than many stations can handle.

Sales of IBOC receivers isn't exactly as they present.  Let's face it, how
many DXers have bought the Sony XDR-F1HD because it's a stellar analog
receiver and not because they want HD capability?  And how many HD radios
are factory equipped in cars, not because the buyer wanted it?  And how many
are bought by the industry itself?  And how many are bought and returned
because they "don't work"?  None of this is factored in to the sales numbers
posted by the proponents of IBOC.  I've been in radio a long time.  There
has not been even one complaint to any of my clients that they don't have
IBOC.  In fact, in the nearly 40 years I've been in radio, there have been
less than a handful of calls complaining about audio quality.  These radios
don't sell because the average listener doesn't give a flying fig.

This whole system is badly designed, shoved down our throats by overfinanced
and blinder-equipped companies, and flawed in excecution.  The public is
apathetic toward it.  It's dead, Jim...

Craig Healy
Providence, RI


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