"Bill Denton" wrote in message ...

So, the stations must reduce power at night to avoid interference with other
stations on the same frequency. There used to be a type of station known as
a Class IV that was intended to basically serve a single community. They all
operated with 1,000 watts daytime and 250 watts at night. I think I worked
at three different stations that were on 1290.

It's basically the same situation with directional antennas; they are used
to avoid interference with other stations. But they also frequently had a
slightly different purpose; you could use a directional antenna to allow you
to put a station in a geographical location where it would not otherwise be
permitted.


i used to work at a station that had a combination of both of these concepts:
it was licensed for 50kw day, 1kw night. the antenna pattern looked something
like:
a b c
d e f
g

during the day, the 50kw drove c,e,and g. at night, the 1kw drove abcdef. so
we used both power and radiation pattern. we were totally off air from midnight
to 5:00 am. i used to work two morning shifts and one night shift on weekends,
so i had to switch the transmitters and the antenna bank at sunrise and sunset.

as i remember it, the first year i worked there, even though we were licensed
to 50kw, we usually only put out about 25kw. the transmitter was old, and
the exciter panel would arc if you cranked it up. the local neighbors used to
complain a lot about rfi on their telephone lines, etc. finally, a coupla the
locals must have gotten fed up, because one morning i came in to find that
an axe had been taken to the 50kw transmitter. they really screwed themselves,
though, because the insurance paid for a new 50kw xmtr that didn't have the
arcing problem, so instead of only 25kw in the day, it was 50kw all the time.

sorry about hijacking the thread for reminiscing.

g_a