aa4xx@ipass.net writes:
>
> The following morning after the storm had passed, we started making
> feedpoint measurements to determine why the SWR on each vertical was so
> much higher than back home. Imagine our surprise at finding the
> feedpoint Z of each vertical reading 40 ohms instead of 6 ohms! We then
> started laying out short radials, about 10 feet long, to augment our 16
> long radials that had been previously layed out. After laying out a
> total of fifty radials per vertical, the feedpoint Z for each antenna
> was close to the expected 6 ohms.
Thanks for the info Paul,
I suspect that in all mentioned cases you are talking about radials on the
ground.
Your experiences confirm what would be expected (surprise).
Was any comparison done with elevated radials few vs. many? That is
really what I am after. Thinking and analyzing the situation, there should be
improvement if using many (>60) elevated (or on ground) radials vs. few (<8)
elevated radials over salt water "ground." The question is how much
improvement there is, or is it worth while the effort of going from few to
many on the beach. This is what I am after, not speculations what should
happen, just the facts ma'am!
Modeling and speculation shows that half wave vertical dipole close (<
.01wl) to salty ground seems to be the best/simplest radiator for the beach.
It gets efficient "return" for currents from it's lower half and is looking
at the salt water quarter to half wave out from the base, where it sees the
salt water for low angle for far field pattern.
Looks like there is a need for some hardware experiments to determine the
answers. I have not seen any mention of few elevated vs. many elevated or on
ground in the literature, this is why I am asking for any practical
experiences, to save me some "torture" on the beach :-) Modeling programs
seem to have a weak point in this area. I love EZNEC, helps to explore and
compare various configurations.
BTW re question: ocean vs. salty marsh - the consensus was that if there is
any difference, it would be negligible and perhaps not worth worrying about.
No hard facts obtained by measurements or experiments yet.
Yuri, beach BU/m
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