WITS/Red Sox

[Doug Drown]

<<WKOX, which, at night, currently also uses a two-tower array to produce a
modified cardioid pattern, has even taller towers. (They are top-loaded to
an electrical length of 214 degrees.) These produce even higher
 efficiency--426 mV/m @ 1 km using a power of 1 kW.>>

Question from a broadcasting non-professsional (I've done a lot of
broadcasting but have little understanding of radio engineering other than
running a board): I've read a lot of posts like this in this forum, and
would like to know if any of you could recommend any good textbooks that
would explain, in comparatively simple terms, the sort of thing you're
talking about here.  I find it fascinating, but I don't know what all the
terms mean, and aside from knowing (for example) what kHz, kW, and "null"
refer to, the technical lingo is almost entirely lost on me.   Any
suggestions?

-Doug

----- Original Message ----- 
From: "Dan Strassberg" <dan.strassberg@att.net>
To: "Laurence Glavin" <lglavin@mail.com>; "Garrett Wollman"
<wollman@csail.mit.edu>; <bri@bostonradio.org>
Sent: Saturday, October 07, 2006 5:26 PM
Subject: Re: WITS/Red Sox


> WUNR uses the same two-tower directional pattern day and night. The towers
> are spaced 105 degrees apart along an axis at 70 degrees. As you observed,
> the towers are quite tall--greater than half wave--205 degrees to be
> precise. Consequently, the efficiency shown in CDBS is quite high--410
> mV/m/kW @ 1 km, although it has been speculated that maybe the ground
> system, which is almost 60 years old if it has never been replaced, is in
> serious disrepair. A deteriorated ground system could explain an
efficiency
> significantly lower than the value shown in CDBS. The pattern is a
modified
> cardioid with radiation minima 31 or 32 degrees off axis at 219 degrees to
> protect WWRL and at 282 degrees to protect E Longmeadow. (A true cardioid
> consists of towers exactly 90 degrees apart and has only one radiation
> minimum, along the axis of the array.)
>
> WKOX, which, at night, currently also uses a two-tower array to produce a
> modified cardioid pattern, has even taller towers. (They are top-loaded to
> an electrical length of 214 degrees.) These produce even higher
> efficiency--426 mV/m @ 1 km using a power of 1 kW. The axis of WKOX's
array
> is 35 degrees; in other words, WKOX's current pattern is rotated
> counterclockwise from WUNR's pattern by 35 degrees. I believe that WKOX
was
> built that way because, when the move to 1200 was granted, secondary
> stations on what had been Class IA channels were restricted to 1 kW at
> night. The 35-degree orientation allowed a 1 kW signal to cover
Marlborough
> pretty well at night. Had WKOX been allowed higher night power when it
first
> moved to 1200, the orientation of its towers would probably have been more
> clockwise because the azimuth of WOAI is 33 degrees clockwise with respect
> to the azimuth of WKOX's towers. (And then later on when WBIX moved in
with
> WKOX, it would not have needed to use lower power during critical hours.)
>
> When it looked as if Newton would never approve tower construction at 750
> Sawmill Brook Parkway, I urged that WKOX move there anyhow and use WUNR's
> two existing towers to operate DA-2. It turns out that the existing WUNR
> towers have, within inches, the same physical spacing as the WKOX towers
> (105 degrees at 1600 is 78.75 degrees at 1200). Running 50 kW-D from the
> existing WUNR towers should have presented no problem for WKOX. The night
> power would have had to be much lower than 50 kW, however. Because the
WUNR
> towers' more clockwise orientation would have reduced radiation to the
> northwest, it might have been possible for WKOX to run 5 kW at night and
> still adequately protect CFGO--I'm not sure. But even with 5 kW from a
site
> within the City of Newton, it did not appear that WKOX could deliver an
NIF
> signal to the requisite 80% of the CoL's population. Hence, the FCC would
> have had to grant a waiver.
>
> At 1200, WUNR's existing towers are 153.75 degrees high. The resulting
> efficiency would have been about 7.5% higher than what WKOX will achieve
> from its new 195' towers--the equivalent of more than 15% higher
power--not
> a huge difference, but not trivial either. Since there will be five towers
> at the site (of which WKOX will use only three), and two of the three
> stations that share the site are on frequencies lower than 1600, the area
> covered by the new ground system will be greater than that covered by the
> existing WUNR ground system. Part of the reason that WKOX is projecting an
> efficiency as high as 339 mV/m/kW @ 1 km, is that the ground system of the
> two towers that WKOX will not use is still considered to be part of WKOX's
> ground system. If WKOX were going to use the existing WUNR towers, a
larger
> than normal ground system could also have been employed, somewhat
improving
> on the antenna efficiency that would have been achieved from the
> 153.75-degree towers.
>
> --
> Dan Strassberg, dan.strassberg@att.net
> eFax 707-215-6367
>
> ----- Original Message -----
> From: "Laurence Glavin" <lglavin@mail.com>
> To: "Dan Strassberg" <dan.strassberg@att.net>; "Garrett Wollman"
> <wollman@csail.mit.edu>; <bri@bostonradio.org>
> Sent: Saturday, October 07, 2006 12:15 PM
> Subject: Re: WITS/Red Sox
>
>
> >----- Original Message -----
> >From: "Dan Strassberg"
> >To: "Laurence Glavin" , "Garrett Wollman" , bri@bostonradio.org
> >Subject: Re: WITS/Red Sox
> >Date: Fri, 6 Oct 2006 14:49:15 -0400 In any event, if you find WKOX's
> current signal listenable for
> >only a short distance past Worcester (I find it pretty good all the way
to
> >the Connecticut border on I-84), the new, "stronger" signal will become
> >unsatisfactory to you near the west side of Framingham.
>
>
> In this particulat case, I wasn't doing any radio-geekery, that is trying
to
> hold a station to see how far it would go;  I was actively listening to
> Stephanie Miller and wanted to continue to do so.  I knew AM 1600 in
> suburban Springfield was carrying it and when I flipped to 1600 I
> expected a battle between it and WUNR, but was surprised to get the
> station I wanted quite clearly.  In the past I never had any reason to
> sample AM 1600 out of Longmeadow, so I had no idea what I'd find.
> It does indicate that even during the day, WUNR's signal WNW is no great
> shakes,
> which backs up your previous assertion that the Samill Brook location
> isn't exceptional, even though those towers APPEAR efficient for a
> 1600 khz operation.
>
> --
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