HD Callsigns --> Question re AM HD

Dan.Strassberg dan.strassberg@att.net
Tue Nov 20 10:43:02 EST 2007

The short answer to your question is "no;" not all AMs will be able to
transmit in HD, but not for the reasons you mentioned. Two local
examples of stations whose facilities are reportedly unsuited to HD
are WHYN in Springfield and WGIR in Manchester NH. Both of these are
low-on-the-dial AMs with relatively short towers. I've heard that the
bandwidth of these antenna systems is too low to properly transmit the
HD sidebands.

On the other coast, KJR 950 in Seattle (50 kW-U) is diplexed with KGNW
820 (50 kW-D/5 kW-N). KJR's CE has reported that the filtering
requirements, which result from the proximity of several other
high-powered Seattle AMs on Vashon Island (710, 770, 1000, 1090),
would necessitate equipment that the company cannot economically
justify and that would be too large to fit in the Tx building, so
there are no plans for KJR to run HD. Meanwhile, Salem, the owner of
KGNW, has indicated that it has no current plans for adding HD at any
of its AMs.

A key issue that was overlooked in the misbegotten design of the AM HD
system (and which iBiquity and its acolytes have tried to sweep under
the rug) is pattern bandwidth. At night, the vast majority of US AMs
use directional antennas. In many cases, the required pattern is
achieved only within the channel bandwidth (charitably, about +/- 9.75
kHz from the carrier frequency). Outside of this bandwidth, where the
digital sidebands with their extremely high average modulation levels
lie, radiation is not suppressed to the degree necessary to protect
co-channel and first-adjacent-channel stations. iBiquity's approach to
this very real problem is simply to insist that it's not a problem.
Those who want to be fooled have been. The problem, however, cannot be
fooled into extinction and never will be.

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

----- Original Message ----- 
From: "Jim Hall" <aerie.ma@comcast.net>
To: "'B-R-I'" <boston-radio-interest@bostonradio.org>
Sent: Tuesday, November 20, 2007 8:49 AM
Subject: HD Callsigns --> Question re AM HD

> With all this discussion of HD the last couple of days, I'd like to
> ask a
> question of the experts. Will *all* AM stations be able to broadcast
> in HD?
> I am thinking specifically of the situation between WCRN 830 and
> WEEI 850,
> and to a lesser extent between WBZ 1030 and WBIX 1060. Here we have
> powerful
> stations that are very close on the dial to each other. We all know
> the
> racket that WBZ makes from 1010 to 1050 kHz, but what if WBIX were
> also
> transmitting HD. Would it affect WBZ's HD signal, or vice-versa? (I
> doubt
> WBZ would let it). And WCRN and WEEI are even closer on the
> dial...would
> their HD signals interfere with each other or with the analog
> service?
> Thanks.
> -----Original Message-----
> From: boston-radio-interest-bounces@tsornin.BostonRadio.org
> [mailto:boston-radio-interest-bounces@tsornin.BostonRadio.org] On
> Behalf Of
> Jeff Lehmann
> Sent: Tuesday, November 20, 2007 7:38 AM
> To: 'Ken VanTassell'; 'B-R-I'
> Subject: RE: HD Callsigns
>> The WEEI legal ID now Lists WVEI-FM HD2 as a seperate part of the
>> ID
>> I have a HD radio in my car and the coverage on that radio here in
>> chelmsford is pretty bad. The Boston stations go in and out of HD
>> all
>> the time so the HD-2 channels are all but useless.
> It's actually "WVEI-FM and WVEI HD1" that they've added to the ID.
> Jeff Lehmann
> Hanson, MA

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