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I really begrudge the necessity of posting once more on this newsgroup,
and particularly on this thread. However, I'm dismayed and disgusted by
postings being made by Yuri and Cecil in other forums in which they're
claiming that measurements I made agree with theories and predictions
they allegedly made, and that my measurements therefore validate their
theories. (A quick scan of this thread shows that they even made the
false claims here, after I had quit posting.)
One of the postings is the following, made by Yuri on the eHam TowerTalk
group, Nov. 21, topic "Trap Resonance":
"Why don't you mention what W5DXP came up as explanation for Tom's
errors, why don't you mention what W7EL measured and that it was what I
predicted based on available information and was right on - the 5%
difference for the base loading coil?"
and this one, posted by Yuri on the EHam.net forum topic "Re: Current in
Antenna Loading Coils" on Jan. 7:
"I will leave it here, as the rest of it. W7EL, author of EZNEC measured
toroid coil and found that it HAS different current at its ends, roughly
proportional to the part of antenna that it replaces."
and this one, posted by Cecil on that same group on Jan. 12:
"Roy's data clearly illustrates the phase shift through the coil.
ARCCOS(Iout/Iin) gives an estimate of the phase shift (assuming
forward current and reflected current are of equal magnitude).
In Roy's experiment, Iout/Iin was about 0.95. ARCCOS(0.95) equals
18 degrees, an approximation for the phase shift through the
coil."
As you'll see below (or by looking up the original thread), the first of
my two measurements, for an antenna shortened an equivalent of about 18
degrees, resulted in 3% current attenuation across the coil (not 5%),
and zero phase shift (not 18 degrees). The second test, where the
antenna was shortened more than 33 degrees, measured 5% current
reduction and no phase shift. The method used in the above quote
predicts more than 16% amplitude reduction and 33 degrees of phase shift
for the second test. There's no way my data "clearly illustrates"
Cecil's explanation. To say that it does is a pure fabrication.
I feel compelled to respond to these fabrications, and put the record
straight. I'll do it here, since this is where my measurements were
originally posted.
I made two sets of measurements of the current into and out of a
toroidal inductor at the base of a vertical antenna. The details of the
measurement method and the measurement results were posted here, on this
newsgroup, on this thread. Pictures of the setup were posted on my web
site, with a link posted here.
Before I posted each set of measurements, I asked for predictions of the
results, so that alternate theories could be tested. (I was criticized
for doing this -- it seems that the preferred method of testing a theory
is to look at the results first, then adjust the theory to fit.) Yuri
made a prediction (actually, two different ones) for the first set of
measurements that didn't accurately predict the results. When I
calculated the predicted result for the second set of measurements using
the same method he had used for the first prediction, he retracted any
claim that the method would be valid. (Exact quotes are below.) He
didn't make any prediction at all for the second set of measurements.
Cecil made a number of vague predictions which he later contradicted or
retracted. At the time the second set of measurements were posted, he
had made no prediction at all.
Perhaps Yuri and Cecil have, after the measurements were posted,
developed theories to explain the results. As of the time the
measurements were posted, they hadn't. I highly recommend that anyone
considering their alternative theories to find where they have
calculated the results which agree with my measurements (particularly
the second one, which was designed to produce a testable difference),
and how they derived the equations used for the calculation.
Following is a summary of some of the exchanges between Yuri and me on
this thread last November. The entire thread, "Re: Current in antenna
loading coils controversy" and variants, is available for viewing at
groups.google.com.
------ Summary ------
Here's what really happened. The following quotes are directly from the
google archives of the rraa thread.
I made two sets of measurements. The first had the inductor connected at
the base of a 33 foot vertical. But the vertical was mounted about 1/4"
from a four foot pipe, which reduced the base reactance.
Here, I was asking for predictions for my FIRST measurement -- the one
with the vertical mounted on the pipe.
Yuri posted on Nov. 9:
"In that case,
If the feedpoint current was at 0 deg of the radiator length, and coil
replaces 18 deg of wire, the cos 18 deg = 0.951 which should make
difference, drop in the coil current 5% (or half, 2.5 deg?)
Providing current maximum is exactly at the bottom end of the coil."
and later on Nov. 9:
">Incidentally, I take it that your prediction for the setup I did
measure
>includes an 18 degree phase shift of current from input to output of
the
>inductor?
>
>Roy Lewallen, W7EL
>
Yes, I used Cecil estimate/calculation and taking
cos 18 = 0.951056516 which is 4.8943483%"
So now we have his prediction, using the "cosine rule". The
measurement
I made showed about 3% current reduction from input to output, but with
about 2% (the same amount within measurement error) also occurring when
the antenna was replaced by a series resistor and capacitor -- that is,
no antenna at all. So the 5% prediction was wrong. His prediction of 18
degrees phase shift, which wasn't present, was also wrong. When asked
for the justification for the "cosine rule", he never offered any, so
its origin remains obscure.
However, I saw that the value was too small to be convincing, which is
why I devised the second test. The second test used a more ideal
antenna, with more of the antenna being "replaced" by the inductor.
The
"cosine rule" would predict more than 16% reduction, and more than 33
degrees of phase shift.
Before I gave the results from the second measurement, I posted the
predictions which had been made, as I understood them. Since Yuri had
invoked the "cosine rule" for the first test, I naturally assumed it
would also apply to the second. (This is simply applying the equation
Yuri used in his Nov. 9 posting to the second antenna setup. It's also
the equation now being used by Cecil, as shown in his quote from the
eHam group.) So in my posting I said:
(Quote from my posting on Nov. 11):
"**Yuri's method predicts a reduction of output current magnitude of
16.5% and a phase shift of 33 degrees."
to which Yuri responded, also on Nov. 11:
"It is not my theory. My argument with W8JI and his followers: is the
current in typical loading coil in quarter wave radiator same at both
ends or does it drop with distance from the feedpoint. I have made
temperature observations, W9UCW measured the difference, W5DXP provided
some explanation. Based on Cecils analysis of data you provided, and on
my understanding of the phenomena I guestimated drop in current in your
setup. No theory, no mathematical procedure (yet) just attempt (using
degrees replaced by coil in a radiator) at explanation of what is
happening. I will measure things myself, try to verify previous
measurements and then come up with conclusions and "theory". So far
Cecils (and ON4UN book) theory seems to be closest to the truth. . . "
So now, Yuri has disclaimed the "cosine rule". /He made no other
prediction of the results of the second test./
In summary, Yuri first stated that the "cosine rule" can be used to
calculate the current drop. That would have predicted over 16% current
reduction in the second test. Then he retracted his claim that that
theory would work, before the results from the second test were posted,
and never made any other prediction. He never predicted the 5% result
which was measured, as he's now claiming.
And if you can find a numerical prediction anywhere in the thread which
Cecil made and stayed with, my hat's off to you. $100 goes to the first
person who can point to any prediction made by either Yuri or Cecil
before the second measurement results were posted that predicted second
measurement results of 5% magnitude and zero phase shift. (In the case
of Cecil, this would have to be a prediction that wasn't later modified
or retracted before the second set of results were posted.)
My measurement results are consistent with the fact that the currents
into and out of a physically small inductor are equal. The small
magnitude difference I measured can be explained by stray capacitance on
the order of 7 pF from the output to ground and/or the probe -- not an
unreasonable amount to expect. In no way do my measurements support the
odd theories being proposed by Cecil and Yuri, and any statement that
they do is completely false.
Roy Lewallen, W7EL
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