Coil Current Summary
 

Here are some valid conclusions that can drawn from the
"Current through coils" thread.

A mobile antenna is a standing wave antennas. Some mobile
antennas use loading coils within that standing wave
environment.

There is no useful phase information in standing wave
current. Therefore, standing wave current cannot be used
to determine the percentage of a wavelength that is
occupied by the coil.

Standing wave current cannot even be used to determine
what percentage of a wavelength is occupied by the whip
above the coil. Standing wave current has virtually
unchanging phase the entire length of the mobile antenna.

The percentage of a wavelength occupied by any element
can be estimated using that element's velocity factor.
The velocity factor of the whip is known. The velocity
factor of the coil can be measured or estimated using
applicable formulas.

The presuppositions of the lumped-circuit model render
it ineffective in any attempt to analyze large coils
in a standing wave environment. Either the distributed
network model or Maxwell's equations must be used to
obtain valid analysis results.
--
73, Cecil http://www.qsl.net/w5dxp

Coil Current Summary
 

Cecil Moore wrote:
Here are some valid conclusions that can drawn from the
"Current through coils" thread.

A mobile antenna is a standing wave antennas. Some mobile
antennas use loading coils within that standing wave
environment.

There is no useful phase information in standing wave
current. Therefore, standing wave current cannot be used
to determine the percentage of a wavelength that is
occupied by the coil.

I think I disagree with this. A standing wave has one of two phases
with respect to time, but the two waves traveling through both the
antenna elements and any loading coils do have phase shifts, both with
respect to time and with respect to position. But when the two waves
are superposed, all that is left of this phase information is phase
with respect to position. The phase shift of both the single
direction waves can be inferred by the shift in position of where they
combine to form a node (if you make the (reasonable?) assumption that
the delay in both directions is equal.

Standing wave current cannot even be used to determine
what percentage of a wavelength is occupied by the whip
above the coil.

There is information about this in the amplitude versus position of
the standing wave. But the only very definite points in this
variation are the nodes, so is the length is less than a half
wavelength, you have only the node at the end to work with, so you
have to use the sinusoidal amplitude curve to work with.

Standing wave current has virtually
unchanging phase the entire length of the mobile antenna.

With respect to time, yes. With respect to position, no. The
amplitude is different at different locations, so you can use phase of
the wave with respect to position. It is just a bit of a mental
switch to change from phase in time to phase (fraction of a 180 degree
half cycle of amplitude wave from one node to the next).

The percentage of a wavelength occupied by any element
can be estimated using that element's velocity factor.

Or the velocity factor of the traveling waves can be measured by the
interference pattern they produce as a standing wave. One cycle of
the standing amplitude wave has to occupy the length that carries one
cycle of the traveling wave.

The velocity factor of the whip is known.

Lets say that it has been measured for some cases, and generalized to
others.

The velocity
factor of the coil can be measured or estimated using
applicable formulas.

If they apply to this particular coil construction. Or you could
measure the standing wavelength with an without the coil and, so,
measure the coil's "length" in standing wave (and thus, traveling
wave) lengths.

The presuppositions of the lumped-circuit model render
it ineffective in any attempt to analyze large coils
in a standing wave environment.

Or any other environment where they have a net delay (electrical
length) that is not insignificant with respect to the frequency in
question.

Either the distributed
network model or Maxwell's equations must be used to
obtain valid analysis results.

Or you work with amplitude measurements versus position of the
standing wave.

Coil Current Summary
 

"John Popelish" wrote:
Cecil Moore wrote:
There is no useful phase information in standing wave
current. Therefore, standing wave current cannot be used
to determine the percentage of a wavelength that is
occupied by the coil.

I think I disagree with this. A standing wave has one of two phases
with respect to time, but the two waves traveling through both the
antenna elements and any loading coils do have phase shifts, both with
respect to time and with respect to position. But when the two waves
are superposed, all that is left of this phase information is phase
with respect to position. The phase shift of both the single
direction waves can be inferred by the shift in position of where they
combine to form a node (if you make the (reasonable?) assumption that
the delay in both directions is equal.

I don't disagree with you so I need to rephrase my apparently
poorly worded statement above to make it more understandable.

There is information about this in the amplitude versus position of
the standing wave. But the only very definite points in this
variation are the nodes, so is the length is less than a half
wavelength, you have only the node at the end to work with, so you
have to use the sinusoidal amplitude curve to work with.

Or the velocity factor of the traveling waves can be measured by the
interference pattern they produce as a standing wave. One cycle of
the standing amplitude wave has to occupy the length that carries one
cycle of the traveling wave.

I agree, one can use knowledge and indirect methods. That's
exactly what I do and have been recommending. You and I seem
to be in agreement.
--
73, Cecil, W5DXP

Coil Current Summary
 

Cecil Moore wrote:
"John Popelish" wrote:
(snip)
Or the velocity factor of the traveling waves can be measured by the
interference pattern they produce as a standing wave. One cycle of
the standing amplitude wave has to occupy the length that carries one
cycle of the traveling wave.


I agree, one can use knowledge and indirect methods. That's
exactly what I do and have been recommending. You and I seem
to be in agreement.

I am not sure we have the exact same thoughts, but I think there are
areas of agreement.

The real revelation for me, from this discussion is how the concept of
"phase" takes a dimensional jump (from time to position) when you
change from taking about a traveling wave to the standing wave that
results from the superposition of a pair of oppositely traveling waves
of the same frequency.

Coil Current Summary
 

"John Popelish" wrote:
The real revelation for me, from this discussion is how the concept of
"phase" takes a dimensional jump (from time to position) when you
change from taking about a traveling wave to the standing wave that
results from the superposition of a pair of oppositely traveling waves
of the same frequency.

Yet some people continue to argue that standing wave current is
the same in form and function as traveling wave current. There
certainly is quite a difference between cos(kz)*cos(wt) and
cos(kz+wt)
--
73, Cecil, W5DXP

Coil Current Summary
 

Cecil Moore wrote:
"John Popelish" wrote:

The real revelation for me, from this discussion is how the concept of
"phase" takes a dimensional jump (from time to position) when you
change from taking about a traveling wave to the standing wave that
results from the superposition of a pair of oppositely traveling waves
of the same frequency.


Yet some people continue to argue that standing wave current is
the same in form and function as traveling wave current. There
certainly is quite a difference between cos(kz)*cos(wt) and
cos(kz+wt)

When the two waves combine, information is lost, just as when two DC
currents pass through the same wire. You can measure the total
current, but information as to what each of the original two currents
were, is lost. All you can say is that the two waves add to zero at
some points, and add to an alternating current (at the original
frequency) at some magnitude at other points. These measurements tell
you a lot about the two waves (their physical wavelength on the
conductor, for instance), but it doesn't tell you enough to
reconstruct both of them, completely, without some assumptions.

Coil Current Summary
 

Cecil Moore wrote:
There is no useful phase information in standing wave
current. Therefore, standing wave current cannot be used
to determine the percentage of a wavelength that is
occupied by the coil.

Please replace the above with:

There is no useful phase information contained in the
standing wave current phase measurement. Therefore,
the standing wave current phase measurement alone
cannot be used to determine the percentage of a
wavelength that is occupied by the coil. The
standing wave current amplitude measurement does
contain some implied information about the underlying
forward and reflected waves, e.g. they are equal and
out of phase at a point where the standing wave amplitude
is zero.

How's that, John?
--
73, Cecil http://www.qsl.net/w5dxp

Coil Current Summary
 

This reminds me of the famous Fractenna Threads of years ago, where
Fractenna argued and argued, couldn't convine most people of anything,
and then declared himself correct.

Coil Current Summary
 

On Fri, 17 Mar 2006 18:50:50 GMT, Cecil Moore wrote:
How's that, John?
Sounds like you've finally come around to impeaching your references.

Coil Current Summary
 

wrote:
This reminds me of the famous Fractenna Threads of years ago, where
Fractenna argued and argued, couldn't convine most people of anything,
and then declared himself correct.

What is really strange is that you believe what it "reminds you
of" is of technical importance. How about a technical rebuttal?
Guilt by association is an easily recognized diversion of the
issue. For the record, I argued with Chip as much as you did.
In fact, Tom, I always take your side when you are right.

Gene appears to me to be incredulous that you could possibly
believe there is any information at all in the standing wave
current phase measurement. Hint: There is none, just as Gene
asserts.

I suspect that Roy, W7EL, has discovered that same thing and
realizes that his standing wave current measurements, though
perfectly accurate, didn't provide any information that wasn't
already available from EZNEC or Kraus.

What I suspect is that neither you nor Roy realized that the
standing wave current phase is virtually constant from the
feedpoint to the tip of the antenna in a mobile antenna,
*whether a coil is present or not*. (When I reported the same
results as EZNEC, you implied my measurements were wrong.)
Roy said my measurements agreed with EZNEC. Is EZNEC wrong?

So when is one going to correct the errors on one's web page?
(Please note the use of the objective, third-person, impersonal
pronoun, "one".)
--
73, Cecil http://www.qsl.net/w5dxp

Coil Current Summary
 

John Popelish wrote:
. . .
The real revelation for me, from this discussion is how the concept of
"phase" takes a dimensional jump (from time to position) when you change
from taking about a traveling wave to the standing wave that results
from the superposition of a pair of oppositely traveling waves of the
same frequency.

Of course, we can speak of the phase (temporal or spacial) of any
periodic waveform. But it might be important to keep in mind that the
spacial amplitude distribution of a standing wave isn't generally
sinusoidal. When the forward and reverse traveling waves are equal in
magnitude, the amplitude distribution -- that is, the "waveform" if you
plot magnitude versus position -- is the absolute value of a sine
function. For all other cases, it's described by hyperbolic trig
functions. So the "jump" from time to position involves more than phase;
it also involves a change in waveshape.

Roy Lewallen, W7EL

Coil Current Summary
 

Cecil,

It is often entertaining to see someone switch positions and then claim
that's what he meant all along. (Yes, I am talking about you.) However,
I assure you that I am not "incredulous" about anything to do with this
topic.

73,
Gene
W4SZ

Cecil Moore wrote:
wrote:

This reminds me of the famous Fractenna Threads of years ago, where
Fractenna argued and argued, couldn't convine most people of anything,
and then declared himself correct.


What is really strange is that you believe what it "reminds you
of" is of technical importance. How about a technical rebuttal?
Guilt by association is an easily recognized diversion of the
issue. For the record, I argued with Chip as much as you did.
In fact, Tom, I always take your side when you are right.

Gene appears to me to be incredulous that you could possibly
believe there is any information at all in the standing wave
current phase measurement. Hint: There is none, just as Gene
asserts.

I suspect that Roy, W7EL, has discovered that same thing and
realizes that his standing wave current measurements, though
perfectly accurate, didn't provide any information that wasn't
already available from EZNEC or Kraus.

What I suspect is that neither you nor Roy realized that the
standing wave current phase is virtually constant from the
feedpoint to the tip of the antenna in a mobile antenna,
*whether a coil is present or not*. (When I reported the same
results as EZNEC, you implied my measurements were wrong.)
Roy said my measurements agreed with EZNEC. Is EZNEC wrong?

So when is one going to correct the errors on one's web page?
(Please note the use of the objective, third-person, impersonal
pronoun, "one".)

Coil Current Summary
 

You disappoint me Tom.
After reading what you wrote about a week ago about how bad it was some
years back
you have now reverted back to the old days. There is no need to smear
Cecil like you did with Chip. It will only poison the forum and force
you to leave again. Be nice
and don't get personal with those who do not fall in line with you
Art

Coil Current Summary
 

Roy Lewallen wrote:
When the forward and reverse traveling waves are equal in
magnitude, the amplitude distribution -- that is, the "waveform" if you
plot magnitude versus position -- is the absolute value of a sine
function. For all other cases, it's described by hyperbolic trig
functions. So the "jump" from time to position involves more than phase;
it also involves a change in waveshape.

Exactly! That's why the current waveforms through the coils
are not perfect cosine waves. To maintain the same forward
and reflected power, when the phase between the voltage
and current changes, their amplitudes must change accordingly.

Conservation of energy dictates that V*I*cos(A) must remain
constant (assuming no storage) so if the (A) angle changes,
voltage and current magnitudes must change accordingly.
--
73, Cecil http://www.qsl.net/w5dxp

Coil Current Summary
 

Gene Fuller wrote:
It is often entertaining to see someone switch positions and then claim
that's what he meant all along.

My basic position has been consistant for years and so
has Tom's. If you google the newsgroup from a couple
of years ago, I asserted to Roy that his standing wave
phase measurements were meaningless. I asserted that he
had measured the wrong parameter. Where were you?

Years ago, I indeed thought it was a simple problem.
I no longer think it is a simple problem. If that's
defined as "switching positions", then I am guilty.
--
73, Cecil http://www.qsl.net/w5dxp

Coil Current Summary
 

Cecil Moore wrote:
Cecil Moore wrote:

There is no useful phase information in standing wave
current. Therefore, standing wave current cannot be used
to determine the percentage of a wavelength that is
occupied by the coil.


Please replace the above with:

There is no useful phase information contained in the
standing wave current phase measurement. Therefore,
the standing wave current phase measurement alone
cannot be used to determine the percentage of a
wavelength that is occupied by the coil. The
standing wave current amplitude measurement does
contain some implied information about the underlying
forward and reflected waves, e.g. they are equal and
out of phase at a point where the standing wave amplitude
is zero.

How's that, John?

Much better.