On 1/11/22 1:55 PM, Wes wrote:
I've already posted a copy of what N7CL posted to this group years
ago. His work, as well as the work of others, can also be found in
ON4UN's "Low Band DXing" starting on page 9-14 of the 5th edition.
The answer is there.
Additionally see: "A Closer Look at Vertical Antennas With Elevated
Ground Systems" by Rudy Severns N6LF. He recommends 10-12 elevated
radials as a minimum.
Wes N7WS
My ON4UN is not readily to hand, so I couldn't check it.
Rudy has a wealth of modeled and measured data, but the only comparison
I saw with height of radials was between 8 feet (about 0.03 lambda) and
6" (0.002 lambda).
And the difference was <0.25 dB (Figure 13).
Jim's comment was that N6BT had recommended 20ft for 160m and that Jim
saw a significant improvement going from 6 ft to 20 ft. Which is
inconsistent with Rudy's observations.
But what I was getting at was not just the phenomenology but the
underlying physics.
The radials over ground thing is an interesting problem, because there's
a lot going on.
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