post-sunset authorization query

[Dan Strassberg]

Many Class D AMs can stay on the air 24/7. WJIB is an example. It's on a
Canadian clear channel and needs to protect the Canadian Class A station's
0.5 mV/m 50% skywave contour only within Canadian borders (actually, only ON
LAND within Canadian borders). So the distance between Cambridge and
wherever along the US-Canada border CHWO's 50% skywave signal drops to 0.5
mV/m provides a buffer zone for WJIB's 5W night signal to be attenuated down
to 25 microlts/meter. Some daytimers with full night authorzations also have
and use PSSAs. A local example is WSRO, 650 in Ashland. WSRO begins
operating under its PSSA at local sunset in Ashland but operates with full
daytime power (250W) until local sunset in Nashville. (The dominant Class A
on 650 is WSM.) In most months, Nashville sunset is an hour after Boston
sunset, but it varies. WSRO then reduces power (to a rumored 50W) until two
hours after Ashland sunset, when its PSSA ends. At that point, WSRO reduces
power still further to 9W, which level it maintains until Ashland sunrise.

WSRO is an example of a station located OUTSIDE and to the east of the 0.5
mV/m 50% skywave contour of the dominant co-channel Class A station. Class D
stations located to the east of the dominant station but within that contour
are permitted to remain on the air at reduced power only until local sunset
at the dominant station. An example is WILD, which is within the 0.5 mV/m
50% skywave contour of WBAL. WILD operates with reduced power (I think
around 70W, but I'm not sure) between Boston sunset and Baltimore sunset.

The maximum PSSA power is alleged to be 500W, and indeed Grady Moates
reports that when WBIX was still a daytimer, this was the power it used for
the 15 minutes between Natick sunset and Philadelphia sunset. WBIX also used
its critical-hours daytime pattern during that 15-minute interval. WBIX,
being outside KYW's 0.5 mV/m 50% skywave contour (despite the short distance
between Natick and Philadelphia, WBIX is the beneficiary of KYW's
directional pattern, which protects first-adjacent WEPN in New York City)
actually could and sometimes did legally remain on the air under PSSA until
two hours after Natick sunset, but after the first 15 minutes, the power was
so low, coverage was pretty much restricted to the part of Mt Wayte Ave in
Framinham near the transmitter site.

The power that a station is permitted under a PSSA is not easy to explain,
except it's low and is never supposed to exceed the lesser of 500W or the
station's critical-hours power (which, for most stations, is the daytime
power). PSSA powers (at least for stations on Class A channels) actually
vary from month to month and they are generally lower in the winter than in
the summer. There is no known public FCC database that lists PSSA or PSRA
(pre-sunrise) powers for the many hundreds of AMs that have been granted
PSRAs and PSSAs. The use of PSRAs and PSSAs as well as the nighttime use of
full-time facilities by Class D AMs is optional. If a station doesn't like
its PSRA or PSSA power, it can just not operate during the hours when the
authorization applies. Similarly, some stations actually use lower power
under PSRA or PSSA during certain hours when they could use higher power but
with a directional pattern they consider to be less favorable than the
pattern they use under PSRA or PSSA. A local example is WXKS (AM), which was
granted a 500W ND PSRA when it was still a daytimer. WXKS is now a fulltimer
authorized to run 1 kW-DA at night, but in the winter months, WXKS continues
to use the 500W ND PSRA between 6:00 AM and local sunrise because it covers
the market much better that way than it does running 1 kw DA.

Well, Donna, that's it in a very large nutshell. More, I'm sure than you
ever wanted to know--but not quite all you wanted to know, because the
information for answering the "how much power" part of your question is just
not available.

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

----- Original Message -----
From: "Donna Halper" <dlh@donnahalper.com>
To: <boston-radio-interest@rolinin.BostonRadio.org>
Sent: Wednesday, March 16, 2005 2:07 AM
Subject: post-sunset authorisation query


> Maybe the rules changed or maybe I wasn't totally clear about them, but if
> you have a day-timer, how long can you stay on the air after sunset, and
> with what wattage?  I heard a daytimer on the air long after sunset
tonight
> and they sounded as if they were at just about their full wattage-- I
> thought you can only use reduced power if you are on after sundown.  Do I
> have this all wrong?
>