I have done some measurements of skywave patterns with some success by
integrating a number of readings over time for each azimuth setting. I have a
little software utility I wrote that facilitates this. I usually average
several runs to further minimize the path variations. The results of some of
the tests can be seen on my website at www.telepostinc.com/n8lp.html under the
E-Beam link, along with some detail about the process. The tests were run with
WWV and other commercial stations as sources. It also helps, of course, to run
the tests when the band is open and propagation is stable. When conditions are
good, though, the results can be surprisingly good.
Larry N8LP
----- Original Message -----
From: Tom Rauch
To: w3frg ; towertalk@contesting.com ; Pete Smith
Sent: Friday, June 25, 2004 11:06 PM
Subject: Re: [TowerTalk] Actual LP Performance vs Tribanders
> But let's ask a practical question. If you are trying to
evaluate a
> horizontally polarized antenna, either versus another or
more generally,
> won't the relative signal to a station a mile or two away.
as you rotate
> the antenna, give you some indication?
Ground effects are attenuating or nulling ANY horizontal
signal following the earth. The worse possible way to
measure anything is in the null, because small changes in
the system which includes everything between and around the
antennas can cause big changes in FS.
The slightest amount of feedline radiation or polarization
tilt of a horizontal wave caused by reflections from other
structures can cause huge changes in FS over groundwave,
because path attenuation is significantly less for vertical
polarization at HF frequencies and lower.
With that in mind, what would a groundwave measurement tell
us?
This is exactly what mislead a certain fellow into thinking
his stub-matched all band dipole was several S-units louder
than a tuner matched but otherwise *identical* dipole. Poor
measurement methods are at the root of much misinformation
we see. Measuring a horizontally polarized antenna over a
large distance (more than a few wavelengths) is definitely a
very poor method.
It would be much more reliable to measure skywave in an A/B
test than groundwave of a horizontal antenna.
73 Tom
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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