On 7/27/2024 6:59 PM, jim.thom jim.thom@telus.net wrote:
Quarter wave sloper ?
Just to be xtal clear, when I said 1/4 wave sloper,
Yes, and that's been a popular way to do it. I chose another, and
described it. It is, indeed, a quarter wave, and it slopes.
BTW -- those rods under the tower are an effective earth connection for
lightning. But they are NOT a low-impedance path for RF, simply because
the earth is a big resistor.
The only function of an earth connection for transmitting antennas is
lightning protection. The earth is a big resistor. The functions of
radials are 1) to SCREEN (shield) the field produced by the antenna from
lossy earth; and 2) to provide a low resistance path for the antenna's
return current. A counterpoise provides only the second function.
N6LF has been publishing some excellent work on radial systems,
describing an interactive research process wherein he models various
conditions, then built and measured them extensively, revising his model
or modeling different variables, depending what he learned in the
measurements, and so on. It is excellent engineering, and has given me
many new understandings/insights of why radial systems behave the way
they do. Many of us consider it the most important work on LF antennas
in fifty years.
https://www.antennasbyn6lf.com/
The 2009 series on ground systems and the 2012 series on elevated radial
systems are the material I find so worthwhile. Grab them and settle in
with a nice Scotch.
73, Jim K9YC
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