Re: [IRCA] New NRSC-5 Standard is Available online

["Rene F. Tetro" <rene@xxxxxxxx>]

I've been looking at the NRSC-5 standards this morning and found
something that we all knew inherently, but that the standard now shows
definitively.  If you look at the chart showing the hybrid
analog-digital signal with 5KHZ analog audio, you will see that the
actual digital information does not begin until you are 10KHZ removed
from the carrier.  The digital signal takes up 5KHZ of bandwidth from
about 10KHZ-15KHZ from the carrier on upper and lower sidebands.  

Consequently, an AM IBOC station on 1100 will take up spectrum from 1085
to 1115 KHZ, wiping out not only the first adjacents (1090 and 1110) but
creating havoc with the second adjacents (1080 and 1120), as well.
Again, this is pretty much what we have all heard with our own ears
and/or suspected, but is now in print for all to see.  

A random 10 minute spectrum analysis of one IBOC station here in Philly
shows that they are not even close to being within the proposed NRSC-5
mask.  How many others out there are like this?  This particular station
I am sure would be brought into compliance because their engineering
department is exceptional.  But what about all of those little stations
with marginal contract engineers.  That's the kind of thing that worries
me.

The upside (if there is one) is that if and when AM becomes all digital,
and the analog part of IBOC goes away, we will be back to about a 10 KHZ
bandwidth -- actually slightly less.  Of course, a lot of us on the
older end will probably not be around to see this "brave new world."




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