On 5/21/2012 4:37 PM, Stuart Rohre wrote:
> If your local soil varies so much that your radial currents are not
> balanced, the effect will likewise alter your pattern, but that does not
> prevent the vertical from working as expected, it just may favor one
> direction over another, slightly.
> The variations in the propagation has a much greater effect on the
> signal and for that we have no control, once the signal leaves the
> antenna.
Of course, we also have little or no control
over the ground conditions under the stick .
For that reason, if I ever get the chance... I will
pull up the sod and lay a huge ground screen made
of welded galvanized fencing, heavy duty lawn fabric
or the like following Rob Sherwood's example - but even
more extensive than he did ! I would have laid some
of that when I put up my big stick, but (as you suggest)
the ground under my stick is far from even - either in
composition or elevation - and I could not imagine how
I would get it to lay flat enough to work its way into
the thatch over time. That stuff could really wreck
my wife's mower if it did not lie flat and disappear
like wire does. I certainly don't wanna have to
start doing the lawn MYSELF !
And seriously folks...
All this talk about the 43 foot vertical... just makes
me wonder how much better something TUNED and
somewhat RESONANT - LIKE THE HY-GAIN HI-TOWER -
might work over a nice, sweet radial field. This is
one of the reasons I shortened my 43 footer to a 33-
foot 40 meter ground plane. I am wondering whether
it will work any better as a tuned, resonant ground plane,
than a somewhat larger non-resonant stick. I am curious
to discover whether the added gain from being longer
outweighs or sufficiently counters the added losses
from higher SWR in the coax and 4:1 Un-Un.
Time will tell, but it was way cool to stick the analyzer
on it and have a 1.35 - 1.38 SWR all across the 40 meter
band, with text-book 38 ohm impedance. AT 43 feet,
it showed 6.8 SWR (without Un-Un) and 2.5 SWR
(with Un-Un).
Should be fun finding out.
Most of the signal influence once radiated depends on the
> earth out beyond the Fresnel Zone, some 5 wavelengths beyond the antenna
> location and usually out of the ham's control as to what is on the earth
> at that distance---buildings, ponds, different terrain or elevation.
Fresnel Zone...! Sheesh!
Now you gotta go and complicate matters ! I was
just getting a handle on the Pseudo Brewster angle...
and now you gotta throw some other nonsense into
the mix !
Er... um... just kidding... ;-)
------------------------------ K8JHR ------------------------------------
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