Hi Karin,
The lurking-in-the-shadows, most often ignored 1000 pound gorilla in the
room, is that the driving impedances and performance of four squares depend
hugely on the type, quality and specific implementation of the counterpoise
scheme for the system.
My experience with vagaries of many counterpoise systems, is that a single
published set of Z will not be close in at least half of attempts.
The issue is that the subject of counterpoise is an absolute jungle, far
more complex and hard to understand than anything about the up-in-the-air
antennas themselves.
One aspect of doing a 4 square well is the absolute need to make each
vertical AND ITS COUNTERPOISE, AND ITS ENVIRONMENT, as identical as
possible.
Since we have firmly, without question, established that ground in a given
backyard radius can have remarkably different qualities than the ground in
a different radius in the same back yard, it is entirely possible that
creating identical elements in a 4 square simply cannot be done at a
particular single address.
For example, in North Carolina, two or three feet of sand/mixed vegetation
rot tripe, can be over a three foot tilted layer of sand that emerges to
the surface 50 feet away, over a foot layer of hard red clay, over a foot
of charcoalish remnant of some ancient forest fire, over tens of feet of
hard-pan gray clay, over a layer of something or another that moves water
and is where the wells drill to.
The topology of where these are low and where these are high and where
tilted and in what direction depends entirely on where all the creeks went
over the last 500,000 years of history.
Or you can be suburban or urban, and what is immediately beneath depends on
what, from old asphalt and concrete scraps to sand, to dirt suitable for a
lawn, lies hidden below in your nice flat building lot that carves out and
fills in the original shape of the land.
All of that murkiness does not mean your 4 square will not perform, just
that you may have simply zero chance of your Z spreadsheet looking like
someone's else's.
Pay attention to "identical" to the extent you can, put the rest out of
your mind, and get on the air. You might find nulls vary wildly from very
deep to not much at all. Nulls are very "twitchy", far more so than forward
gain. Get on in a contest and work stuff.
Above all, keep in mind that the counterpoise for each vertical is its most
important component. Potential losses in a poorly done counterpoise can be
non-intuitively high, even though this now firmly verified conclusion has
not yet made it into common low-band lore and urban legend.
Good luck and keep us up to date on how it goes.
73, Guy K2AV
On Thu, Oct 27, 2016 at 12:31 PM, Karin Johnson <karinann@tampabay.rr.com>
wrote:
> I am trying to replicate a spreadsheet which computes the driving point
> impedances for a four square
>
> Using the formulas in ON4UN's "Low Band DXing". The results are not coming
> out per the example given
>
> In chapter 11, which I downloaded. I don't have the actual publication, so
> don't have access to the previous
>
> Chapters. Basically the math doesn't work per the example given in the
> book, using the book's formulas.
>
>
>
> Anyone have any insight to this??
>
>
>
> Karin K3UU
>
> Palm Harbor, FL
>
> _______________________________________________
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> Antennaware@contesting.com
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>
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