On 12/18/2025 7:35 AM, Radio KH6O wrote:
Grounding rods will be driven in at each corner.
The earth is a big resistor. The only function of ground rods on
transmitting antennas is lightning protection. They do NOT make
transmitting antennas work better.
The functions of radials is NOT to couple to earth, but rather to SHIELD
the antenna's field from it, and to provide a low impedance return for
antenna current -- that is, they are the other half of the antenna.
I agree with KH6AQ's advice. And I suggest that you read my piece about
160M radial systems, which is really a compilation of great engineering
work by others on the topic.
http://k9yc.com/160MPacificon.pdf
Even better, go to the most important source, Rudy Severns, N6LF.
https://www.antennasbyn6lf.com/
Rudy lit the big lightbulb for me about radial systems and loss. He
analyzed radial systems by studying the distribution on them of the
antenna's return current. Several important takaways.
1) That current divides between them numerically. The closer they are to
the earth, the more current they induce in the earth, which shows up in
each radial as series resistance. The loss in each is I squared R, where
R is that loss coupled R. The total loss in the radial systems is the
sum of I squared R numbers.
2) As we increase the number of radials, current in each is
proportionally less, but LOSS in each is reduced by the SQUARE of the
number of radials. THAT'S why more is better!
3) Each radial exhibits the same current distribution as any other part
of an antenna.
4) An antenna will be lengthened (that is, VF less than 1) by close
proximity to the earth. For example, I've measured VF on the order of
0.75 on 160M for radials laying on the ground at my QTH in the Santa
Cruz Mountains (poor soil, very rocky). SO -- at my QTH, a quarter-wave
on-ground radial is about 100 ft.
5) Current distribution on antenna elements is determined by length, and
must be near zero at the far end. An antenna (that radial) longer than a
quarter wave but shorter than a half wave will result in a peak value of
current along it that is greater than at the feedpoint, which can
increase the loss coupled from the earth. Rudy recommends that radials
be slightly shorter than a quarter wave.
6) #2 and #5 are why, when space is limited or "stuff" limits their
length in some directions, a lot of radials shorter than a quarter-wave
can be an effective counterpoise (return for antenna current).
73, Jim K9YC
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