HD Callsigns --> Question re AM HD

Dan.Strassberg dan.strassberg@att.net
Tue Nov 20 12:11:00 EST 2007

The digital sidebands do not merely affect reception of
first-adjacent-channel stations "200 miles from the transmitter." The
interference can be quite audible well within the protected local
service area of the affected station. A Canadian broadcast engineer,
Barry McLarnon (Google him), has done a lot of careful analysis and
has written extensively on this subject. In the case of WABC and WJR,
I've read that the interefence begins at something like the 13 mV/m
(groundwave) contour of each station. Note that I said groundwave.
When IBOC is in use, skywave service, which is supposedly protected
down to the 0.5 mV/m 50% skywave contours of these Class A AMs, must
be completely decimated on many nights. In WABC's case, the
interference to the groundwave signal probably occurs well within the
five boroughs of New York City (parts of Queens and Staten Island),
not to mention suburban Nassau, Westchester, and Fairfield Counties.
For WJR, it must certainly occur well within the Detroit metro. There
have been reports of objectionable interference to KDKA from WBZ
within the Pittsburgh city limits. If WBAL is running IBOC at night,
it must seriously interfere with WTIC well within the Hartford metro.
Meanwhile, KDKA must cause objectionable interference to CFRB within
the Toronto city limits.

The first-adjacent problem is so severe because of the very high
modulation levels on the digital sidebands. Even though the sideband
power sounds modest, the nature of the modulation makes the effective
power considerably higher. And the sidebands fall squarely on top of
the first-adjacent channels. The effect is even easily noticeable on
the second-adjacent channel. Try listening to WINS's killer skywave
signal here at night. WBZ's lower digital sideband often completely
inundates WINS.

Dan Strassberg (dan.strassberg@att.net)
eFax 1-707-215-6367

----- Original Message ----- 
From: "Sid Schweiger" <sid@wrko.com>
To: "'B-R-I'" <boston-radio-interest@bostonradio.org>
Sent: Tuesday, November 20, 2007 11:22 AM
Subject: Re: HD Callsigns --> Question re AM HD

>>>Why should Citadel care whether someone 200 miles from New York
> can
> hear a Detroit station, or vice versa? Is WJR selling Syracuse to
> its
> advertisers as a market they can reach? As for WYSL ... geez, I've
> been
> a
> BCB enthusiast for years, but even I realize that the stations on
> the
> band
> are intended to serve their cities of license and immediate areas,
> not
> DXers
> in far-off cities with local broadcasters of their own. How,
> exactly,
> is
> WYSL's complaint actionable? Seems to me that as long as people in
> Avon
> and
> its immediate vicinity can hear WYSL, any other listeners the
> station
> might
> lose to IBOC splatter from WBZ don't matter, right?<<
> I don't know the specifics on the Citadel situation, other than at
> least one report I've seen on the Internet which claims that WJR and
> WABC were interfering with each other at night.  Since both stations
> rely on national and network advertising, and since those buys are
> related in part to station coverage at night (even outside the NIF
> contours), that could directly affect the bottom line.  Bob Savage
> is
> claiming that the interference from WBZ is reducing the nighttime
> interference-free contour of WYSL...that is, the coverage he is
> supposed
> to have *inside* his community of license.  That's apparently the
> nut
> that has to be dealt with on AM-HD...that, if one believes the
> reports,
> the interference from the HD carriers at night affects stations
> hundreds
> of miles away.  This has nothing to do with ticking off DXers.  This
> is
> (again, according to the claims) reducing coverage of a station in
> its
> community of license that it had previously, and upon which its
> business
> was built.  Savage is claiming (and states that he has engineering
> data
> to back up those claims) that people formerly served by WYSL's
> nighttime
> signal can no longer hear it.  His view is that the FCC has
> officially
> sanctioned interference which harms his ability to do business.
> What
> the FCC will do with this claim and the submitted engineering data
> is
> anyone's guess at this point.
> Sid Schweiger
> IT Manager, Entercom New England
> 20 Guest St / 3d Floor
> Boston MA  02135-2040
> Phone: 617-779-5369
> Fax: 617-779-5379
> E-Mail: sid@wrko.com

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