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

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.

"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

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.

"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

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.

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

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.

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.

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