[IRCA] IBOC Revisited

["R. F. Tetro" <rtetro@xxxxxxxxx>]

Now that we have experienced several nights of IBOC operation throughout
the country, and most of us have had a chance to do some initial Dxing
under these new conditions, I am interested in your responses to the
following question:  Has the sky indeed fallen as many of us predicted?

Here is what I have found over the past few evenings.  As we all know,
nighttime IBOC does indeed create the same hash as we have become
accustomed to during the day, particularly on the first channel
adjacents, but to a lesser extent to the second d adjacents, as well.
It must be remembered that the IBOC information is carried on sidebands
from 8kz-15khz removed from the carrier.  So that if IBOC is being
transmitted on 1210 WPHT, its digital artifacts will not just effect
stations on 1200 and 1220, but - to a lesser extent - 1190 and 1230.
This is because the IBOC information has encroached about the second
adjacent's analog sideband by at least 5khz.  To make this more clear a
station on 1230 will receive digital IBOC hash from 1210 on its lower
sideband from 1220-1225 Khz.

I have experimented with several techniques to alleviate this situation,
most of which are available to anyone with a general coverage receiver.


The first technique, and one of the most effective, is to use the USB
and LSB modes on you receiver.  If, for instance, you are receiving IBOC
has from 710 on 690, switch operation to lower sideband so that the hash
on 695-700 becomes diminished or altogether invisible.

Another technique is to use extremely narrow bandwidth filters (such as
2.4 and 1.8 khz), either when monitoring on AM, or when using sideband
techniques.  The narrow bandwidths, coupled with good notch filtering
practices, may render the IBOC hash almost invisible.

So, has the sky fallen?  Are we up against the demon forces of HD radio
to the extent that many of us suspected?  Or, has the IBOC revolution
merely opened up a new chapter in the history of our hobby.?  I tend to
believe the latter.  For instance, in the past two nights I have been
able to log several stations in the digital mode...some stronger than
others, some solid and others with their HD signals fading in and out
and tough to pull in.  

I think this whole IBOC thing may, contrary to what many of us (myself
included) may in the end be a boon to Dxing.  It may force us to develop
new techniques, but it also will afford us the opportunity to pull in
digital signals from hundreds of miles away.  For me, the bottom line is
that it is - for the time being - a mixed blessing, but one which we
Dxers can take advantage of.

Looking forward to a great DX seasons, and glad to be back on the NRC
and IRCA lists after a break during the summer.

73,
Rene'

Rene F. Tetro
Lansdale, PA, USA
W2FIL, WPXG816, WPXU288
Coordinates:  40D12'41"N  75D18'22"W
Grid:  FN20IF
Email:  rtetro@xxxxxxxxx
Websites:  www.westpointcommunityradio.org; www.veronicafm.org;
www.exalt1700.org; www.breezy1630.org; www.dxhub.com  
NOTE:  Opinions expressed are my own and do not necessarily represent
those of my employer, family, friends, co-workers, God himself, or any
others.



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