Topband: Beverage Pointing

Michael Sapp Michael_Sapp_WA3TTS at
Fri Feb 10 16:01:22 EST 2006

To K5PC & Folks:

        Using the average of sunrise and sunset times is only as good as
the source. Your local newspaper or weather station
might not be all that dependable, as you don't know where there data comes
from. GPS would be ideal, or a satellite tracking program
like AMSAT's Instant Trak has Sun and Moon tracking so you could find due
South very accurately. There are also many basic astronomy
programs out there with Sun, Moon & Planetary tracks. If the Moon, Venus
and Jupiter all track a program with good accuracy you could
probably assume the Sun tracking was close. Another advantage for satellite
programs is the Sun track also shows you the greyline, which is convenient
to access at any time  without linking to the Internet.  Even so I can't
see how plus/minus 5 degrees of azimuth is going to make much difference if
the antenna's 3dB beamwidth is 60 or 80 degrees----it's not like you are
pointing a 5 ft dish on 5.7Ghz...( I've seen
3-4 Sunits of QSB up there when the wind was rocking the dish on the rotor
gears.)  Look at a standard beverage azimuth plot for your antenna's stated
length and freq then see what the db curve does for +/- 5 or 10 degrees or
so at the -10db points or greater. It may make a slight difference there
versus the -3db points.

        Mike WA3TTS

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