Well, the whole point of using elevated radials is to provide a return
path for currents independent of whatever is below them (lossy ground,
etc). I have several times modeled a vertical with "tuned" radials at
various points above ground (i.e., the vertical extends all the way to
ground but the radials attach higher and the feedpoint is just above the
radials) ... in every case, if the radials are "tuned" they choke off
all current below them. It's actually a relatively easy way to make a
multiband vertical just by switching in/out the upper set of radials.
I've only used EZNEC+ for this, but we're not talking the
wires-near-ground limitation of NEC2 here.
So if the radials are indeed resonant, I don't see how whatever current
might be induced into the ground screen ever gets back to the feedpoint
to improve efficiency. Maybe somebody smarter than me can educate both
of us ...
73,
Dave AB7E
On 3/17/2015 7:11 AM, Ed Sawyer wrote:
3. Elevated radials make sense versus using an extensive ground screen
over really poor ground, but again ... that only affects efficiency and
not pattern, and doing both makes little sense. The elevated radials
mostly shield the ground screen from providing any useful benefit unless
the ground screen is a lot larger than the area of the elevated radials.
Try listening to K3LR running EU on 80M and think again. Ohio/Penn soil is
not salt water and a 4 sq is a 4 sq. So if the extensive ground screen over
elevated radials is so useless - what is your explanation of the
performance.
Dave AB7E
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