On 9/23/2012 6:51 PM, Wes Attaway (N5WA) wrote:
Tom is obviously correct in saying that you can't infer much about claims of
performance unless you have some good test data to back up the claims.
FWIW, I have not heard or seen K2AV making unreasonable "claims" of
performance. Guy says that it works as well as,some compromise radial
and counterpoise solutions that many of us are forced into by our
surroundings, our real estate, our XYLs, and our budgets, better than
some other solutions, and not as good as others. .I have yet to hear of
another 160M counterpoise that works as well and can fit in 66 feet! He
has done extensive design work on it, he has published that work in a
very clear way, he has described how he thinks it works.
Most important, it is a solution for small city lots. It has already
allowed dozens of guys to get on 160M from a QTH where they had
previously given up. The "barrier to entry to "the gentlemen's club" --
sorry, "the gentlemen's band" has been greatly lowered -- a guy no
longer needs an acre of land and $2,000 worth of copper on the ground to
put a signal on 160M whose sidebands might compete with one of those
super weak signals DX signals 10 dB below the noise level.
As to real measured data -- Over the last few weeks, I've been doing an
extensive study and review of the literature that I can find on the
topic of radial systems, and in response to my request last week on this
list, One of those guys whose work I've seen a lot of, and which is
published extensively by ARRL, is Al Christman, K3LC. I've read a LOT of
his articles, and I've yet to see a single measurement -- everything is
based on simulations.
W4TV suggested that I look up a series of posts by N7CL in the early
days of the Topband. When I did, I found an escellent series of tutorial
posts that, in essence, put everyone back in school. I owe Joe a
six-pack for that one! As a consultant to both broadcasting and the
military, Eric has been able to measure, with all the resources that
those clients could bring to bear, the characteristics and performance
of many types and variations of antennas and ground systems, over a wide
range of frequencies, at test ranges representing virtually every sort
of soil condition imaginable.
Eric had also done considerable modeling, and he emphasized that if the
model will fall short if the person doing the modeling misses some
elements of the problem that are present in the real world. Tom's
discovery that the FCP was reactive at the operating frequency is a
great example of that, and it explains why a good ferrite choke would
overheat -- it is because the reactance causes the antenna to be
seriously unbalanced, which places a very high common mode voltage
across choke.
Eric's tutorials spoke then (and still do) with the authority of a solid
EE background and extensive experience, and his writing is both VERY
clear and reasonably concise. I have printed all that I could find, and
have studied them carefully.
I have done the same with the extensive and carefully analytical work of
Rudy Severns, N6LF. It consists of a very good mix of both careful
measurement, followed up by modeling to try to understand what he
measured. His most recent paper, about 30 pages split between two
recent issues of QEX, can only be described as a tour de force. In it,
he shows extensive modeling, mostly on 80M, to uncover the REASONS why
some measurement results seemed counter-intuitive.For example, he has
discovered WHY certain radial lengths work better than others -- what
the specific mechanisms are that are causing losses to be much greater
in one situation than another There many very useful revelations in this
piece. It, and all his work, is on his website.
Both his work and Eric's work are easily found using google. To find
Eric's work, I think I searched on N7CL radials. The stuff I found was
from 1997 and 1998. For Rudy, I searched on N6LF.
73, Jim K9YC
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