It's Official: WPEP-AM Defunct

[Dan.Strassberg]

It's not often that one can catch the nearly infallible Scott Fybush
in an error, but this appears to be one of those rare instances. Scott
was probably misled by WPEP's running less than 250W at night. With
that power and even a normally efficient quarter-wave antenna, WPEP
would have remained a Class D. HOWEVER, WPEP's antenna was a)somewhat
more than quarter wave and b)more than normally efficient. As a
result, WPEP's night RMS of ~169 mV/m/kW @ 1 km, was well in excess of
the 141.85 mV/m/kW that was required for it to qualify as a Class B,
and according to CDBS (as reflected in Bob Carpenter's AMSTNS program)
WPEP was indeed a Class B.

As for WNSH becoming a Class B or even just modestly increasing its
night power from 85W, it may happen, but I'm skeptical about the
likelihood. The reason is WNSH's incredibly low antenna efficiency.
The low efficiency is a consequence of the very short (albeit
top-loaded) tower AND perhaps the worst ground system in the US.
Because the tower is built on solid rock, it was (as described in
WNSH's application for the daytime power increase) impossible to bury
the ground radials. They lie atop the rock, which is very close to an
ideal insulator. This situation results in an efficiency of 57.41 mV/m
@ 1kW, which is equivalent to 41.5W from a minimally efficient Class B
or D radiator. Because of the low efficiency, WNSH required a waiver
for its antenna, which the FCC granted because of the unavailability
of an alternative site.

Don't be confused by CDBS's listing of an 85W ND-N RMS greater than
57.41 mV/m @ 1 km to go with the 30-kW ND-D operation. I believe the
correct number _IS_ 57.41, which is the value given for the
(identical) old 85W ND-N operation that went with the old 500W-D. The
higher RMS of 86.53 mV/m @ 1 km appears to be incorrect. If it were
correct, it would imply that WNSH's antenna efficiency was 297 mV/m/kW
@ 1 km, which, I believe, is the value that goes with the top-loaded
tower's 66-degree electrical height. That efficiency assumes a
standard ground system and WNSH's application for increased day power
admitted that the station's ground system failed to meet FCC
requirements by more than a little bit.

Why all this discussion of the REAL antenna efficiency? Because if the
signal does not propagate in the ground plane, it has to go somewhere
and that somewhere is up. WNSH must limit its nighttime power mainly
to protect co-channel CFAV in Laval QC (Montreal). Because of the
relatively short distance between Beverly and Laval, high-angle
skywave is critical for this protection. Using just 85W, WNSH radiates
a high-angle skywave that is about the same as that for which WPEP's
more efficient (in the horizintal plane) antenna needed 225W. The
alternative would be to install a DA to protect Laval, but Keating has
been through that already (he already built a night DA for WNSH at the
Endicott College site and gave up on it). In any event, a DA that
protected Laval would do nothing for WNSH's coverage over land; the
signal maximum would lie to the south--over open water.

Now, if WPEP's demise removes a contributor to the RSS of 10% skywaves
that contribute to CFAV's NIF (nighttime interference-free) signal
level, there MAY be room for WNSH to get a small night power increase,
but don't count on it. The ratchet rule could well prevent such a
change.

The technically correct approach would be for WNSH to diplex with
WESX, whose tall tower could either be physically shortened to ~190
degrees at 1570 or skirted at the top to reduce its electrical height.
WESX could get back its lost coverage by increasing its
power--although WESX nominally runs 1 kW, it in fact runs only a
little more than 600W to protect WBUR (AM) on Cape Cod. With the
higher efficiency of the WESX tower, it appears that, from the WESX
site, WNSH could duplicate its 30-kW ND-D coverage with less than 10
kW and could likely get a significant increase in night power--perhaps
enough to qualify as a Class B (like WPEP was). The problem with this
approach is that it would require the WESX tower to remain standing
and that would run afoul of the late Otto Miller's (recently deceased
owner of WESX) plan to donate the WESX site to the Town of Marblehead.
If that plan should come a cropper (as it may), WNSH would appear to
be making a huge mistake by remaining at the Endicott College site.

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

----- Original Message ----- 
From: "Scott Fybush" <scott@fybush.com>
To: "Donna Halper" <dlh@donnahalper.com>;
<boston-radio-interest@rolinin.bostonradio.org>
Sent: Saturday, October 27, 2007 11:52 PM
Subject: Re: It's Official: WPEP-AM Defunct


> Donna Halper wrote:
>
>> Wow, that's a call letter which has been around for a while.  Could
>> somebody buy the station and put it back on the air, or has that
>> ship sailed already?
>
> That ship has sailed. WPEP was silenced to make way for Keating
> Willcox's daytime power increase to 30 kW at WNSH.
>
> But to answer another question, the disappearance of WPEP's
> nighttime 200-some watts doesn't do anything for WNSH at night.
> That's because WPEP was a class D station, which received no
> nighttime interference protection to begin with, thus creating no
> holes at night by going away.
>
> And even if WNSH didn't implement its power increase, there's no way
> to get the WPEP facility back once it's been surrendered - they
> don't issue new class D licenses now, and when they're gone, they're
> gone.
>
> s
>