WSRO Power Boost

[Dan.Strassberg]

Since WSRO is on 650 and is using an array that was designed for almost
twice that frequency (1200), you can scarcely expect that the pattern would
be ideal--although Garrett's observation about the mandatory pattern
symmetry is absolutely correct. Even at 1200, the tower spacing was only 79
degrees. At 650, it is only 42.8 degrees, which is very close and can lead
to problems with pattern stability, which might be why Charlie Hecht, the
consulting engineer who designed the new pattern, did not try for anything
too exotic. Fortunately, the towers were very tall for 1200--189 degrees,
top loaded to 214 degrees. You'd almost think that, when they constructed
those towers back in 1981, the Fairbanks folks were thinking about use of
the array by a station lower on the dial. Also, at 650, the towers are 115.9
degrees, which is more than adequate for the lower frequency, even with a
ground system that was designed for 1200.

Anyhow, the azimuth of the line of towers is 35 degrees (10 degrees north of
northeast). The WKOX pattern minima were, IIRC, at 180 and 250 degrees. WSRO
does not depart much from that; the minima are at 183 degrees and 247
degrees. At these minima, the equivalent power is only about 7% (1/14th) of
the pattern RMS. Using the night parameters, WSRO sends the equivalent of
only about 4.4W toward WSM. Since the ND night power was 9W, you have to
wonder whether, in a year or so, after the array stability has been
demonstrated, Hecht might be thinking of applying for a night power increase
to something closer to, but still below, the 250W Class D maximum--low
enough to keep the Class D status, but also high enough to provide a
listenable nighttime signal somewhat east of Route 128. There probably is no
way WSRO could change its CoL from Ashland to Framingham (it is Ashland's
only radio station and probably has an NIF of ~10 mV/m, which means that,
using the Mt Wayte Ave array, even with 250W at night, I don't think it
could meet the Class B signal requirements for Ashland--an NIF signal or
better over at least 80% of the town's population).

For those wondering what kept Alex Langer from building this power increase
before WKOX's move to Newton and WBIX's move of its daytime operation to
Ashand, the answer is that the 650 upgrade became practical only after WKOX
and WBIX moved out--remember that 1200 ran 10 kW by day and 1060 was also
using the site during the daytime at high power (40 kW-D/22 kW-CH). With two
other high-power stations at the site, replacing the 250W-ND 650 with a
higher-power directional version would have been prohibitively complex and
expensive.

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

----- Original Message ----- 
From: "Laurence Glavin" <lglavin@mail.com>
To: <boston-radio-interest@lists.BostonRadio.org>
Sent: Saturday, July 14, 2012 4:27 PM
Subject: WSRO Power Boost


>I guess it's no big deal, but WSRO-AM 650 seems to have gone ahead with its
>power boost, with or without Governor Patrick's
> assistance. My radio that displays relative signal strength shows an
> uptick in the signal during the day, but only a little. My table radio
> in-house is receiving a clearer signal and on my car radio, it can be
> heard while I'm driving
> around Methuen and Lawrence. Previously I could only get it on the
> highways around here. The coverage
> graph at fcc.gov shows a pattern sending its strongest signal during the
> day to the northeast. I would have
> expected a major lobe due east. Does anyone know if WKOX-AM 1200's pattern
> was directed due east or a
> skosh to the northeast? It also appears that WSRO's directional daytime
> pattern sends less signal to the NW, W and SW
> than its 250-watt NDA.