Air America's night signal

[Dan Strassberg]

WXKS's night signal is equivalent to 3 kW at an azimuth of 54 (arc) degrees,
which is the center azimuth of the pattern--that is, the azimuth of a line
between the two towers. At zero degrees (due north), the signal is
equivalent to 2 kW. Those equivalent-power values assume that you use WXKS's
pattern RMS of 319.7 mV/m/kW @ 1 km as the radiation produced by the actual
antenna-input power of 1 kW. Another means of reckoning the equivalent power
normalizes to an RMS of 281.7 mV/m/kW @ 1km, which is the RMS
inverse-distance field from a minimum-efficiency radiator for a Class B
station. (Such a radiator would be approximately 56 electrical degrees high,
whereas WXKS's towers are taller than 100 electrical degrees.) If you use
the lower figure for the 1 kW-equivalent signal, you get higher equivalent
powers of about 3.75 kW at 54 (arc) degrees and 2.55 kW at zero (arc)
degrees.

I don't know what WXKS's NIF (nighttime interference-free) contour is. My
guess is that it's in the neighborhood of 50 mV/m. Fortunately, the short
distance between 99 Revere Beach Parkway and the nearest points of land in
Everett is covered by salt water, so you can use the inverse-distance rule
to compute the signal strength at the water's edge in Everett. I'd be
surprised if that distance were more than 500' (1/6 km) at the closest
point. So WKXS probably puts a nighttime signal of about 2V/m over the
closest point of land in Everett. From there, the signal strength drops off
at something between the square and the cube of the ratio of the distance to
1/6 km. I calculate therefore, that the NIF contour lies approximately 2.5
miles to the northeast. I suspect that nearly all of Everett lies within the
NIF contour. But the signal should be quite listenable at distances at least
twice as great and maybe even further.

--
Dan Strassberg, dan.strassberg@att.net
eFax 707-215-6367

----- Original Message -----
From: "Laurence Glavin" <lglavin@lycos.com>
To: "Scott Fybush" <scott@fybush.com>; <bri@bostonradio.org>
Sent: Tuesday, January 04, 2005 4:55 PM
Subject: RE: Air America's night signal


> >From: "Scott Fybush" <scott@fybush.com>
> >To: bri@bostonradio.org
> >Subject: RE: Air America's night signal
> >Date: Mon, 03 Jan 2005 22:51:03 -0500
>
> >
> > As for 1430, the Endicott facility is a barn-burner. I was just
> > there a few weeks ago visiting the TX site. They've got a new BE
> > AM6A transmitter there that gets out well, and the night pattern is
> > a five-tower in-line teardrop that blasts to the northeast (maximum
> > lobe field strength is 1887 mV/m at 1 km, quite impressive for a 5
> > kW station.) And did I mention that it's up on a hill, so the array
> > really launches that skywave towards Boston?
> >
> Right at this minute, about 20 minutes after local sunset in
> January, skywave is very subdued and WXKS is audible 25 miles
> north of Wellington Circle.  A few weeks ago, due to a solar hiccup, there
> was little difference between day and night (one person posted to
> the New York city radio board that he could pick up Stamford's
> outlet at 1400 in the City!) and during that period, I could listen
> to WXKS-AM easily in my home; even WJIB-am at 5 watts was
> at least as audible as it would be during the day if the station's
> switcher failed to boost to 250 watts at sunrise.  So it
> appears that WXKS-AM is legally putting out the equivalent of
> several hundred watts, or even a kilo due north,  NW and NNE...
> yet it is still clobbered by WENE.  In the morning, when I'm on
> route 128 north of Boston, I can pick up the two Marks AND
> Imus on WENE simultaneously!  It's amazing that even Everett
> gets sufficient quieting!
> --
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