RadioBanter - Current through coils

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Current through coils

Tom Donaly wrote:

Cecil, there are two Corums and they're both Tesla coil
crackpots. Secondly, Tom is right, you have to have capacitance
to somewhere or your transmission line analogy becomes mired in
absurdities. Third, it isn't enough to think something up in
your head to make a convincing theory, you have to be able to
predict behavior with it. Finally, you have to understand your
subject before you even start thinking. I'm surprised you didn't
even take the time to make a real coil and at least try to
determine its characteristics before wasting everyone's
time by starting this thread.
73,
Tom Donaly, KA6RUH

Tom,

You, and everyone else is, as we put it in the midwest, and probably
elsewhere, "****ing into the wind".

You cannot win an argument with someone that does not acknowledge reality.

tom
K0TAR

Current through coils

Tom Ring wrote:
You cannot win an argument with someone that does not acknowledge reality.

I've found that out, Tom. None of you guys are willing to
answer any technical questions about the material presented
on my web page at: http://www.qsl.net/w5dxp/current.htm,
in particular: http://www.qsl.net/w5dxp/1WLDIP.GIF

The current through a coil placed in a standing wave
environment either depends upon where it is placed in
that environment or it doesn't. It's not rocket science.

The gurus have refused to discuss at least 95% of my
technical questions. No amount of personal wise cracks,
like yours above, will erase that fact.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils

Cecil Moore wrote:

Tom Ring wrote:

You cannot win an argument with someone that does not acknowledge
reality.

I've found that out, Tom. None of you guys are willing to
answer any technical questions about the material presented
on my web page at: http://www.qsl.net/w5dxp/current.htm,
in particular: http://www.qsl.net/w5dxp/1WLDIP.GIF

The current through a coil placed in a standing wave
environment either depends upon where it is placed in
that environment or it doesn't. It's not rocket science.

The gurus have refused to discuss at least 95% of my
technical questions. No amount of personal wise cracks,
like yours above, will erase that fact.
Cec;

I hate to be the one to break it to you but you are the one they are
talking about.
When everyone says you are drunk, like down, your drunk.

Dave N

Current through coils

Early... too early... on Saturday morning, I wrote:

Tom Donaly wrote:

What lumped circuit theory? It's a simplification and everyone
knows it. Don't set up any more straw men than you have to, Cecil.

It's a simplification of any real-life coil - but loading by
pure-and-simple lumped inductance is also a vital test case.

This form of loading is the simplest imaginable. If a theory about the
behaviour of loaded antennas fails to give correct results for this
very simplest test case, it cannot be valid... and all the further
elaborations about real-life coils will not be valid either.

Evidently I was in too much of a hurry to leave for the GMDX convention,
because what I mean to write next was:

"Cecil's theory does not work for this test case, "

[ I definitely did type the word "not", but it accidentally disappeared
from the version that was posted. ]

So, from the top of the paragraph:

Cecil's theory does not work for this test case,
because it requires that basic electrical properties like current and
inductance switch into a different kind of behaviour in what he calls a
"standing wave environment". But it is an absolutely basic fact that
the physical world does NOT change its behaviour according to the way
we choose to think about it. If any theory requires that, it's an
absolute proof that such theory is false.

For the avoidance of doubt (as they say in Scottish legal documents):
It certainly IS possible to analyse and predict the behaviour of
coil-loaded antennas in terms of travelling and standing waves. My
objection is specifically against Cecil's method, which is provably
incorrect.

Sorry for any confusion that typo may have caused. This corrected
version is now fully consistent with what I meant to say.

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

Current through coils

Tom Ring wrote:

Tom Donaly wrote:

Cecil, there are two Corums and they're both Tesla coil
crackpots. Secondly, Tom is right, you have to have capacitance
to somewhere or your transmission line analogy becomes mired in
absurdities. Third, it isn't enough to think something up in
your head to make a convincing theory, you have to be able to
predict behavior with it. Finally, you have to understand your
subject before you even start thinking. I'm surprised you didn't
even take the time to make a real coil and at least try to
determine its characteristics before wasting everyone's
time by starting this thread.
73,
Tom Donaly, KA6RUH

Tom,

You, and everyone else is, as we put it in the midwest, and probably
elsewhere, "****ing into the wind".

You cannot win an argument with someone that does not acknowledge reality.

tom
K0TAR

If we don't pee into the wind Cecil will end up telling everyone his
crackpot theories are received truth, and eventually we'll be reading
them in _The ARRL Handbook_. I appreciate the fact that it's a waste of
time, otherwise. Entertaining, though. Cecil's an interesting Character.
73,
Tom Donaly, KA6RUH

Current through coils

David G. Nagel wrote:
I hate to be the one to break it to you but you are the one they are
talking about.

I know that, Dave. At best it is the pot calling the kettle
black. At worst, it's just another falsehood, one of many.

The problem here is not "Current through coils". The problem
is that a lot of the gurus are completely ignorant of the
nature of standing wave current and refuse to alleviate
their ignorance.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils

Ian White GM3SEK wrote:
Evidently I was in too much of a hurry to leave for the GMDX convention,
because what I mean to write next was:

"Cecil's theory does not work for this test case, "

[ I definitely did type the word "not", but it accidentally disappeared
from the version that was posted. ]

Well there you have it, folks. Gurus don't even make typo mistakes.
Some evil server removed that "not" on purpose from Ian's posting.

Cecil's theory does not work for this test case,
because it requires that basic electrical properties like current and
inductance switch into a different kind of behaviour in what he calls
a "standing wave environment".

RF current switches from a different kind of behavior than DC current.
Phase, capacitance, inductance, and wavelength all have to be taken
into account in the steady-state analysis. That is a technical fact
that I'm sure you appreciate.

Why is it such a stretch to recognize that standing wave current behaves
differently from traveling wave current? That standing wave current is
different from traveling wave current is readily apparent from the
equations. In the following equations, 'K' is used for a constant,
'z' is the linear distance up and down the line, and 'w' is omega.

Forward traveling wave current = K1*cos(kz+wt)
Reflected traveling wave current = K2*cos(kz-wt)
Standing wave current =
K1*cos(kz+wt) + K2*cos(kz-wt) = K3*cos(kz)*cos(wt)

If tK1 = K2, then the standing wave doesn't move. Please dust off
your old math books and realize what the above equations imply at
a physical level.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils

"Ian White GM3SEK" wrote in message
...

From the beginning, then:
snippydidudaa

As we have seen, if the whip is loaded by pure inductance only, there is
no change in current between the two terminals of the inductance - but
there's a big step increase in voltage. At the upper terminal, the current
is the same but the voltage is very high, so we're into a much
higher-impedance environment.

Reality check here. I need explanation how the above could happen. "Current
stays the same ... and the big step increase in voltage." As far as "idiot"
professors taught me, (current x voltage) = power. So, am I to discover
that the pure inductance is better than perpetual motion amplifier of power?
More power coming out of the coil than going in? Eureka!!! How could I
overlook that? :-)

As we go further up towards the top of the whip, current magnitude has to
taper off to zero at the very top. This also means that the voltage
magnitude has to increase even more as we approach the top of the whip.

So it tapers across the straight piece of conductor, but not in the wound
up conductor? Magine that! Reality check #2.

Single-point loading by pure inductance has thus created almost all the
major features that we see in a practical centre-loaded whip -
particularly the big step change in voltage across the loading coil.

So the "teaching" is that there is a big step change in the voltage across
the coil, but no-way change in the current? Who's law, theory, invention is
that? (We are still talking about real RF currents, not "my voltage" and
"your invincible, steady, unchengeable current"?)

What we don't see in a practical antenna are exactly equal current
magnitudes and zero phase shift between the terminals of a real-life
loading coil - but that is ONLY because a real-life coil is not a pure
inductance. The harder we try to reach that ideal (by winding the coil on
a high-permeability toroidal core which confines the external fields and
allows the whole thing to become very small), the closer the currents at
the bottom of the coil come to being equal. Solid theory and accurate
measurements come together to support each other. The only gap between
theory and practice is due to our inability to construct a pure inductance
that has no other complicating properties.

The whole argument is about REAL LIFE loading coil in the antennas. But you
obviously ignored or not noticed that W9UCW also used toroid coil and found
very similar results, about 40 - 60 % less current at the top end and NOT
(just about) EQUAL as the arguments IS about. Who cares about or needs
"pure" inductance? What for? Just to twist the argument that "gurus" were
right? Gimme a break!

If we can agree about pure inductive loading, we all have a firm place to
stand. Then we can then put back those "other" complicating properties of
a real-life loading coil, and see what difference they make.

As firm as driving my Buick in the free space!
Halooooo! Go measure it! See what it IS! Then if the coil IS hot at both
ends, or you measure current almost equal at both ends, describe the
experiment so we can verify it and we will rest our case and admit to be a
bunch dummies stuck on stooooopid!
(We are still talking about quarter wave resonant, loaded typical mobile
antenna with loading coil about 2/3 up the 8 - 10 foot mast, no detours to
la-la pure inductance in the vacuum with no resistance, free space
no-nothing thing :-)
And as Cecil mentioned, we are not disputing that there is no capacitance to
the surroundings, or no losses through resistance and radiation amounting to
SMALL (you put figure on it Richard) drop, versus more SIGNIFICANT (like
40 -60%) drop across the loading coil.

I am sorry to beeing away for a zilion of posts, but real life is more
important and I am trying to be in touch. I will try to find the W8JI
response to my first (start from scratch) post in order to find where I went
wrong, if he will engage in some technical discussion. I hate to be wrong.

Happy second April foolsday!

Yuri, K3BU.us

[1] This principle of "conservation of charge" is also the underlying
principle of Kirchhoff's current law. If you connect three ordinary wires
together, the current flowing into the junction from one wire must be
exactly and instantaneously balanced by the currents flowing in or out on
the other two wires. If this was not so, there would have to be some means
of adding, storing or losing electrons at the junction... which
contradicts our initial assumption of three simple wires with no special
properties.

It is not strictly accurate to say that Kirchhoff's current law applies to
pure inductance, but the underlying principle of "conservation of charge"
does apply.
--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

What "other two wires"? I see RF current flowing through one wire (base)
then another wire in series (coil) than another one in series (tip - whip)
then "finding" the tip, aka END reflecting form it, and going back, creating
standing wave with proper current AND voltage distribution according to sine
(or if you like cosine) function.
What about energy (power) conservation law? How can coil "make" more voltage
at the top, while "having" the same current on the top as at the bottom?

73 + 88 from Yuri K3BU, jus' inquiring mind

Current through coils

On Sun, 2 Apr 2006 16:00:16 -0400, "Yuri Blanarovich"
wrote:

I am sorry to beeing away for a zilion of posts, but real life is more
important and I am trying to be in touch. I will try to find the W8JI
response to my first (start from scratch) post in order to find where I went
wrong, if he will engage in some technical discussion. I hate to be wrong.

Didn't you start a new thread to clear out the cobwebs? That seems to
have gone the way of the dodo.

Hi Yuri,

Instead of chewing old gum over and over again, why not simply fulfill
a promise offered two years ago?

I hope it warms up, so I can get out, dig the car from the snow and do some
experimenting.

First experiment will be with 80m Hustler coil in order to use "standard"
(lousy) typical coil. I will paste LCD strip thermometers on the coil to
measure temperature changes at various positions, ends, middle.

Experiment #1:
I will drive DC current through the coil in order to generate heat and observe
the temperatures across the coil. I predict that thermometers will be tracking
each other very closely or be identical (ideal case).

Experiment #2:
I will insert the same coil in the Hustler mobile antenna, tune to resonance
and fire 100W to it. I will observe temperatures between the end and center and
between two ends. I expect difference indicating difference in current at
various points.

This will be the least disturbing measurement setup, no conductive nothing
disturbing the coil or antenna. I am assuming LCD thermometer is RF transparent
and I will verify that it does not detune the antenna/coil. Perhaps not very
accurate, but sufficient to demonstrate the debated differences.
The next measurements will be with current probes and RF ammeters. This will
give more accurate values.

Any problems with that?

Yuri, K3BU.us

No problems with that, but no results either.

73's
Richard Clark, KB7QHC