Hi.

I think that whether IBOC is a good idea or not depends upon your
objectives for listening to the AM band.  It seems likely that skywave will
suffer, so if DXing is your thing, it will get harder than ever.  But if
you are looking to get local programming, it could actually be a
significant improvement depending upon how it is implemented.  Digital
signals typically do not degrade from the presensence of noise until the
noise becomes strong enough to capture the signal.  And, if it is like
other digital modes that I've worked with, you will most likely get a
capture effect that will more resemble FM, so no more mixture of two
signals on the same frequency.  The strongest one wins.

Now, where I think there might be trouble is with the selective fading that
is typical at night, particularly on the upper end of the AM broadcast
band.  This type of fading was noticeable on WKBW when I was growing up
from as little as 30 miles away, and they run 50 kW.  I suspect that a
digital signal will lose its lock for a few seconds at a time under such
conditions.

The other thing I am wondering is how much bandwith is required to have
reasonable audio quality.  My experience is that when digital has
insufficient bandwidth, it takes on that watery sound that is so typical of
cell phones.  If that is what my digital will sound like, I think I'd
rather have noisy old analog.  Of course, all of this is speculation on my
part from what I know of digital signals in general, as I have not gotten
my mits on a digital receiver yet (and there isn't any IBOC in my area yet,
anyway.  I do suspect, however, that fidelity issues are the primary reason
why the signal is 30 kHz wide.  My question would be is the same
information sent on both sides of the carrier, which would be a giant
waste, or is there different information on each sideband, like maybe left
and right channels?

I think that if the FCC could figure out a way to prevent medium wave
signals from propagating via skywave, they would do it.  They are clearly
interested in local markets these days, and as long as someone's IBOC
doesn't cut into someone else's primary coverage, I think they are fine
with whatever interference does occur.

73, de Lou K2LKK



Louis Kim Kline
A.R.S. K2LKK
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