Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
Ian White GM3SEK wrote:

Ian, I am leaving on a 6 state motorcycle trip and won't be
back until Monday. I would like for you to answer this
question while I am gone.

I've heard that, while operating portable, if I attach
a wire to my 75m mobile whip and run it up a tree, I
will be able to make more contacts. So I attach a 1/4WL
wire to the whip of my 75m mobile bugcatcher system.

I decide to measure the current "into" the bottom of the
coil and "out" of the top of the coil. To my utter amazement
I measure 1.3 amps flowing "into" the bottom of the coil and
2.1 amps flowing "out" of the top of the coil.

How does your lumped circuit theory explain that? Where is
that extra 0.8 amps of current coming from?

Please don't insult our intelligence by saying it cannot
happen. It does happen. I suspect you are at a loss to
explain it.

I do not expect equal currents at the top and bottom of any real-life
coil. That is a strawman argument, based on what *you* claim other
people are saying.

But you can make coils that come quite close to behaving like an ideal
lumped inductance. And the closer they are, the closer to equal I expect
the currents at the two ends to become, and the closer to zero I expect
the phase shift in current to be... because that is how pure inductance
behaves, with no exceptions due to "special situations".


Cecil, in all sincerity, have a good trip and please drive safely. I'd
have been much safer on the roads last weekend if I hadn't been thinking
about this stuff as well.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Current across the antenna loading coil - from scratch
 

On Wed, 12 Apr 2006 19:55:08 GMT, Cecil Moore
wrote:

Richard Clark wrote:
But you CAN afford to be paranoid? What a WUSS!

It doesn't cost anything to be paranoid. :-)

You must have a Xerox bulk copy rate.

Current across the antenna loading coil - from scratch
 

Cecil,

I will retain the entire message below, so that I am not accused of
misattribution.

Where did you get this idea that the velocity factor is constant?
Specifically, why is the velocity factor of a resonant coil the same as
the velocity factor of a significantly shorter coil? It is pretty well
accepted that the inductance of coils does not scale linearly with the
length of the coil. Therefore any arguments about based on direct
calculation of Vf from L and C would seem to fail to support your model.

I can think of two possibilities.

The first is that you treat this entire problem as a transmission line.
Most people would accept that the velocity factor for 200 feet of RG8 is
indeed the same as the velocity factor for 100 feet of the same cable.

However, the velocity factor appears to be the crux of your latest
argument about the behavior of a loading coil. It is not exactly
acceptable technique to include the desired answer as part of the proof.


The other possibility is that you are taking the lead from one of the
Corum papers. In particular, I am referring to the paper labeled:

"TELSIKS 2001, University of Nis, Yugoslavia (September 19-21, 2001) and
MICROWAVE REVIEW"

If so, I suggest you go back and reread what was written. He
specifically says (page 4, left column) that the equations for velocity
factor that show Vf as a function of diameter, spacing, and wavelength
apply only at resonance. The exact words a

" . . . an approximation for M has been determined by Kandoian and
Sichak which is appropriate **for quarter-wave resonance** and is valid
for helices . . ."

The emphasis on quarter-wave resonance was in the original; I did not
change a thing. The remainder of the paper clearly indicates that he is
talking about coils near or at resonance. There is no extension of the
Vf equations to short non-resonant coils. Indeed, he comments several
times that his model smoothly joins with the lumped circuit model for
smaller coils. That would require a non-constant Vf.

You attempt at decomposition of a resonant coil into smaller
subcomponents simply fails.

This is not an "ignorant diversion". If you have a third method of
supporting your claim of constant Vf, let's hear it.

73,
Gene
W4SZ

Cecil Moore wrote:
Gene Fuller wrote:

Cecil Moore wrote:

Gene Fuller wrote:

So you think adding turns to a coil is a nice linear process that
allows you to then subdivide the resonance effects according the
number of turns in each subsection?


That appears to me to be the most valid measurement that we
can make of the delay through a coil. If you have a better
way, please present it.


C'mon, you know as well as anybody that inductance of a coil tends to
increase as n-squared. Yes, there are all kinds of special cases and
correction factors.


Increasing the length of a coil or transmission line doesn't
change its velocity factor at a fixed frequency.

Adding turns and then pretending everything is nice and linear,
thereby allowing decomposition into subcomponents, is just plain silly.


Velocity factor is *nice* and linear, i.e. it is constant.

Please stop these diversions. I'm sure you are not that ignorant.

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
Richard Clark wrote:

Paper trail? Phil, push over those stacks of "research" and fire up
the Xerox!


I am indeed printing out the postings just in case the false
attributions result in a lawsuit against me. I can't afford
not to be careful.

Cecil, no one but a madman would ever sue you for anything.
Your presence alone would wreck any legal proceeding even
in a state as idiosyncratic as Texas.
73,
Tom Donaly, KA6RUH

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
John Popelish wrote:

A series inductor (a non real, ideal one) with absolutely no phase
shift or magnitude change in the current from one end to the other,
still produces a phase shift of input voltage to output voltage, ...


If the voltage is leading the current, and the current
experiences no phase shift through the coil, doesn't that
imply that the voltage must travel faster than light and
indeed jump forward in time to catch up with the phase
of the current?

What does it mean to the E-fields and H-fields to say
the voltage is leading the current?

It means that the current at both ends of the coil was delayed
(relative to its phase if the coil had not been there). It means that
there was a voltage difference across the ends of the coil that drove
that current through the coil.

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
Gene Fuller wrote:

Is 10 degrees of phase shift "roughly" equal to 75 degrees of phase
shift?


Of course not. The 10 degrees of phase shift has already been
proven to be wrong because of reflections within the coil.
Why do you insist on bringing up old invalid data?

Please note that *nobody* is alleging that the phase shift
through a 75m bugcatcher coil is 75 degrees. That is just
another one of your straw men.

Now why don't you become a rational, ethical person and
suggest a valid way of measuring the phase shift through
a coil? Can you improve on my suggestion of yesterday?

Cecil,

You spent a lot of time developing the "10 degree" model for the
bugcatcher coil. When and how did it get proven wrong? The only thing I
can recall is that you said it did not make sense technically, and
therefore it must be wrong. Recently you launched into this business
about adding turns to make the coil resonant. As I just explained, I
believe that approach is total nonsense.

You keep referring everyone to the now famous gif image on your web
page. The question becomes why is EZNEC correct in supporting your
position at some times and incorrect when it does not support your
position at other times?

73,
Gene
W4SZ

Current across the antenna loading coil - from scratch
 

Ian White GM3SEK wrote:
Cecil, in all sincerity, have a good trip and please drive safely. I'd
have been much safer on the roads last weekend if I hadn't been thinking
about this stuff as well.

Sincerely, Ian, how do you explain one amp on the source side of
a coil and two amps on the whip side of a coil? Nothing in your
response even came close to answering that question.

If you are dedicated to technical correctness, your evasion
of this technically simple question is perplexing.

How is it possible to have one amp "flowing into" the bottom
of a coil and two amps "flowing out" of the top of the coil?
If you really believe that one amp is flowing from the earth
ground to the coil through displacement current, please just
say so.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Richard Clark wrote:

Cecil Moore wrote:
It doesn't cost anything to be paranoid. :-)

You must have a Xerox bulk copy rate.

I got a free printer with my new Dell computer.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Like I posted earlier today, Tom, all of this provides an interesting
window into Cecil's mind.

Imagine my reaction when I read today's (2006-04-12) edition of the
Lola comic strip: http://www.comics.com/comics/lola/index.html

Cheers,
Tom

Current across the antenna loading coil - from scratch
 

Gene Fuller wrote:
I will retain the entire message below, so that I am not accused of
misattribution.

Gene, to the best of my knowledge, you have never
misattributed anything.

Where did you get this idea that the velocity factor is constant?

The equation for velocity factor includes coil diameter,
turns per inch, and wavelength. Keeping the coil diameter
constant, the turns per inch constant, and the wavelength
constant should ensure that the velocity factor is constant.

Specifically, why is the velocity factor of a resonant coil the same as
the velocity factor of a significantly shorter coil? It is pretty well
accepted that the inductance of coils does not scale linearly with the
length of the coil. Therefore any arguments about based on direct
calculation of Vf from L and C would seem to fail to support your model.

You are obviously mistaken. If you increase the L by lengthening
the coil, you have also increased the C by the same percentage.
The L and C for any unit length are the same no matter how long
the coil or transmission line is.

" . . . an approximation for M has been determined by Kandoian and
Sichak which is appropriate **for quarter-wave resonance** and is valid
for helices . . ."

Yes, but if one doesn't change the frequency or the diameter or
the turns per inch, the approximation should hold since nothing
in the VF equation changes by shortening the coil. One should be
able to shorten or lengthen the coil andmaintain the same VF.

Seems it is up to you to prove what you are saying. Please prove
that the ratio of L to C ratio of a coil changes with length. That
should be an interesting proof.
--
73, Cecil http://www.qsl.net/w5dxp