Current through coils
 

Jerry Martes wrote:
I've read more than 80% of the posts in this thread.
I still dont understand the objective.

Since the foundation of other's measurements was
the use of standing wave current phase to prove the
percentage of a wavelength occupied by a loading
coil is zero, my objective was simple: To prove
that the standing wave current, with its unchanging
phase, cannot be used to make a valid measurement
of the percentage of a wavelength occupied by a loading
coil.

I proved that using the standing wave current phase to
measure the percentage of a wavelength occupied by a
wire or a whip also yields an answer of zero. If the
coil plus the whip both occupy a percentage of a
wavelength equal to zero, all sorts of laws of physics
are violated. Not to mention a full length 1/2WL wire
dipole occupying a percentage of a wavelength equal
to zero.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil,

I could have sworn that you were insisting the phase still had meaning
in a standing wave environment. It only required the correct measurement
technique.

I am glad to see that you have now adopted the truth, even if the
history appears a bit shaky.

73,
Gene
W4SZ

Cecil Moore wrote:
Jerry Martes wrote:

I've read more than 80% of the posts in this thread.

I still dont understand the objective.

Since the foundation of other's measurements was
the use of standing wave current phase to prove the
percentage of a wavelength occupied by a loading
coil is zero, my objective was simple: To prove
that the standing wave current, with its unchanging
phase, cannot be used to make a valid measurement
of the percentage of a wavelength occupied by a loading
coil.

I proved that using the standing wave current phase to
measure the percentage of a wavelength occupied by a
wire or a whip also yields an answer of zero. If the
coil plus the whip both occupy a percentage of a
wavelength equal to zero, all sorts of laws of physics
are violated. Not to mention a full length 1/2WL wire
dipole occupying a percentage of a wavelength equal
to zero.

Current through coils
 

Gary Schafer wrote:
Rather than a 50 ohm load how about if a load was placed at the end of
the coil to simulate the antenna, a resistor and capacitor to take the
place of the antenna impedance and reactance. Then measure the current
in and out and the phase shift.

The measurement problem is harder than it looks. Here's
a quote from "Field and Waves in Modern Radio", Ramo and
Whinnery, 2nd edition, page 227.

"Difficulties in applying these equations arise since
the current and charge distributions are not known, but
are determined by the field distributions which are
calculated from the retarded potentials which depend
upon current and charge distribution - a vicious circle!
The exact solution of this problem is usually of
prohibitive difficulty."
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Gene Fuller wrote:
I could have sworn that you were insisting the phase still had meaning
in a standing wave environment.

I know that's what you thought, but you were mistaken.
By thinking that, you accidentally posted some support
for my side of the argument. Thanks very much.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

"Reg Edwards" wrote in message
...

Hi Cecil

I've read more than 80% of the posts in this thread. I still
dont
understand the objective. BUT, I sure have learned a few things,
thanks to
you guys who do what is being soughtafter.

Jerry
=======================================

Ah, but how do you know you learned the RIGHT things? Or what you
learned was true and correct?

The participants in the argument NEVER agreed on ANYTHING. So what can
bystanders do?

I learned far more about people than I did about current through
coils. Quite interesting nevertheless.
----
Reg, G4FGQ.

Hi Reg

I note that you question my ability to know if I learned the Right Things.
How do we ever know?? I wrote that I learned a FEW things. Let me be the
judge about whats right for me.
I dont know if you wrote the question about my learning the Right thing to
impune my ability to sort out the Right from the NotRight, or you wrote to
imply that were some statements made in the thread that werent right.
I submit to you that if you find the need to show where any statement made
in the antenna group that isnt True and Correct, you can correct them
directly.
By my standards, all the posts in this thread were worthy of being read.
It is even possible that you learn something from these guys on the
antenna group when you take time to read and think.
Please dont stop trying to learn Reg, you are a great source of good
information and you can improve if you try.

Jerry

Current through coils
 

Gary Schafer wrote:

When the measurements of the coil were done on the bench it seems that
it was done with 50 ohms in and 50 ohms out. That hardly seems like it
would give the same information as when the coil was in actual use as
an antenna loading coil.

A bench test is fine. An inductor is an inductor.

The only problem with a bench test is simulating the load impedance
presented by the antenna and of course strong local fields generated
by the antenna are missing, but the actual error can be reasonably
small.

However, inductors were measured in an actual antenna. I measured
current, and Roy Lewallen measured phase and current.

I couldn't measure time delay or phase in my actual antenna because I
was measuring a mobile antenna. There wasn't any way to measure phase
without perturbing the system and rendering any data unreliable.

This long painful thread (it's been going on years now) started because
K3BU claimed a loading inductor had most of the current in the first
few turns. I made some measurements
and posted them at:

http://www.w8ji.com/mobile_antenna_c...ts_at_w8ji.htm

These measurements show exactly what anyone who understands loading
coils would expect, that it is stray C in comparison to load impedance
on the inductor that determines any current taper, and that for a
reasonable sized inductor the taper is very small.

I wrote a description at:

http://www.w8ji.com/mobile_and_loaded_antenna.htm

I can't see anything in there that needs changed, based on what I've
read here in this thread.

Rather than a 50 ohm load how about if a load was placed at the end of
the coil to simulate the antenna, a resistor and capacitor to take the
place of the antenna impedance and reactance. Then measure the current
in and out and the phase shift.

I've done that also.

You are absolutely correct Gary, it is possible to come very close with
a lumped load on the inductor *except* of course the surroundings are
different.

The inductor test fixture I normally use is a large copper box made
from blank double sided PC board sheets. It has vacuum caps (very high
Q) and various detectors and probes.

I have to characterize large inductors on occasion as part of designing
RF systems. It's less scary than turning on a 50kW PA and having things
misbehave at full power, or building a phasing system or phasing/ATU
combo that doesn't work.

73 Tom

Current through coils
 

wrote:
************************************************** **************
Please turn your technical expertise on this example which I
have asked you about many times with no response from you:

http://www.qsl.net/w5dxp/current.htm

At the bottom of the page, the coil is seen to have 0.17 amps
at the bottom and 2.0 amps at the top. With your lumped inductor
way of thinking, how is that possible?
************************************************** ***************
A bench test is fine. An inductor is an inductor.

But the chosen valid model varies depending upon which inductor
it is. Dr. Corum says the model must be changed over at 15 degrees
of the self-resonant frequency. These are velocity inhibited slow-
wave helical coils that we are talking about.

And standing wave current is certainly not traveling wave
current. Remember what Gene Fuller said? Please read it again.

Gene said about standing wave current:
Phase is gone. Kaput. Vanished. Cannot be recovered.
Never to be seen again. The only "phase" remaining is the
cos (kz) term, which is really an amplitude description,
not a phase.

How can one use a signal where the phase is gone to measure phase?

However, inductors were measured in an actual antenna. I measured
current, and Roy Lewallen measured phase and current.

You and Roy measured standing wave current the phase of which is
unchanging over the coil and whip and entire antenna. You should
have realized over the past week that those measurements were
meaningless. EZNEC shows the same thing. Kraus reports the same
thing.

ONE CANNOT USE THE PHASE OF STANDING WAVE CURRENT TO MEASURE THE
PART OF AN ANTENNA THAT A LOADING COIL REPLACES.

... and that for a
reasonable sized inductor the taper is very small.

The present argument is not about taper, it is about how much of
a wavelength a loading coil occupies. One cannot measure that value
using standing wave current as you and Roy did. Roy reported
accurate phase measurements but standing wave current phase is
meaningless since it has unchanging phase.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:
Gene Fuller wrote:

I could have sworn that you were insisting the phase still had meaning
in a standing wave environment.


I know that's what you thought, but you were mistaken.
By thinking that, you accidentally posted some support
for my side of the argument. Thanks very much.

Cecil,

I am attaching a few of your quotes in this thread. Sorry to hear about
your total loss of short term memory.


[Direct quotes from March 5-7]


Standing wave current is a net charge flow of zero. Standing wave
current is DIFFERENT from traveling wave current. At any and every
point, the standing wave current is NOT moving. Since it is not moving,
there is NO net charge flow.

******

To tell the truth, standing waves are a product of the human mind. The
forward and reflected waves couldn't care less about standing waves

Surely you understand that standing waves in a transmission line don't
flow - they just stand there, which is why they are called "standing
waves". Exactly the same principle applies to standing wave antennas.

The two traveling waves have to be analyzed separately and then
superposed to obtain valid results. If you analyze net current without
superposition, you are doing the same thing as superposing powers, which
is a known no-no.

******

The currents that are doing the flowing are the underlying current
components, the forward current and the reflected current and they are
close to equal. Everything you say about a coil is true for the forward
current and the reflected current. It is simply not true for the
standing wave current which is just a conceptual construct and not a
flowing phasor at all.

If you really want to accurately apply the principles you are asserting,
you must treat the forward current and reflected current separately and
then superpose the results. Applying your above principle to standing
wave current is akin to superposing power and that's a no-no.

I have never seen such a wide-spread blind spot.


[end quotes]

73,
Gene
W4SZ

Current through coils
 

Gene Fuller wrote:
I am attaching a few of your quotes in this thread. Sorry to hear about
your total loss of short term memory.

I'm in a learning process here and using the scientific method to
correct my mistakes. Isn't that what rational people do?

[Direct quotes from March 5-7]
Standing wave current is a net charge flow of zero.

I was corrected on that one and already admitted my mistake. The
charges obviously migrate from end to end in the antenna.

Surely you understand that standing waves in a transmission line don't
flow - they just stand there, which is why they are called "standing
waves". Exactly the same principle applies to standing wave antennas.

This means the same thing as your posting that phase is gone.
A phasor requires a rotating phasor to exhibit flow in the
real sense of the word. Standing wave current doesn't possess
a rotating phasor so it is not flowing in the normal sense of
current flow.

If you think standing wave current is flowing, how do you explain
0.17 amps at the bottom of the coil and 2.0 amps at the top?

http://www.qsl.net/w5dxp/current.htm bottom of page

The two traveling waves have to be analyzed separately and then
superposed to obtain valid results.

Don't see anything wrong with that. If one uses the standing wave
current phase to try to measure phase shift through a coil, one is
making a mistake as has been demonstrated here.

The currents that are doing the flowing are the underlying current
components, the forward current and the reflected current and they are
close to equal. Everything you say about a coil is true for the forward
current and the reflected current. It is simply not true for the
standing wave current which is just a conceptual construct and not a
flowing phasor at all.

You said it yourself, Gene, phase has disappeared from standing wave
current. Do you understand the implications of your statements?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Gene Fuller wrote:
Cecil Moore wrote:
. . .
The two traveling waves have to be analyzed separately and then
superposed to obtain valid results. If you analyze net current without
superposition, you are doing the same thing as superposing powers, which
is a known no-no.

Both those sentences are false.

In a linear system like an antenna or transmission line, superposition
applies. This means, among other things, that we can separately analyze
the system's response to various components, and the sum of the results
we get are the response to the sum of the excitation components. For
example, we can split a current into two -- or more -- components, such
as a forward traveling current wave and a reverse traveling current
wave, with the actual current (or what Cecil calls "net" or "standing
wave" current) at any point being the sum of the two. We can find the
voltage across an inductor, for example, which results from the forward
traveling current. Then we find the voltage across the inductor
resulting from the reverse traveling current. Superposition tells us
that the sum of those two voltages is what results from a current which
is equal to the sum of the forward and reverse traveling current waves.

We must get exactly the same result, in this example the voltage across
the inductor, if we find it by adding the separate voltages due
individually to the two current components, or if we find it directly as
a result of the total current. We don't have to separate the current
into two components then superpose the results as Cecil claims -- we get
exactly the same result either way because superposition holds. This has
nothing to do with attempted superposition of powers or other properties
which don't fit into the boundaries of linear quantities.

We're not restricted to splitting the current into a single forward and
reverse wave, either. We can split it into many separate traveling
waves, as well as any number of other combinations. As long as all the
components add up to the actual total current, we'll get exactly the
same result when we separately sum the responses to each individual
component that we do when we simply look at the response to the total
current.

If Cecil's analysis shows, or his theory requires, that the result be
different when adding the responses to traveling current waves than it
is by calculating the response directly from the total current, then the
analysis or theory is wrong. Superposition requires that the two results
be identical.

Roy Lewallen, W7EL