Cecil Moore wrote:
John Popelish wrote:

Since, in both standing waves and traveling waves, current at a point,
changes magnitude and sign in exactly the same way (at a point, they
are indistinguishable), they can both be described with phasor notation.


Limiting oneself to a point measurement is handicapping onself. When
the equation for standing wave current is compared to the equation
for traveling wave current, the real differences are obvious.

I was just making sure we were using the same definitions for things
like current and phasors. You are jumping ahead. :-)

For standing waves, the phasor of a neighboring point has the same
phase shift, ...


Exactly! Therefore, it cannot be used to measure the phase shift
through a coil or even through a wire.

I agree, unless you use phase measurement to hunt for the location of
the current nodes that have moved as a result of adding the coil.
Finding a phase reversal at opposite ends of the coil, for instance,
implies that an odd number of nodes reside in the coil.

But at any point along both standing waves and traveling waves, there
certainly is a phasor that represents the current at that point.

For the standing wave current it is a phasor that doesn't rotate
all up and down the wire.

A phasor rotates at the reference frequency, and with a phase angle
that represents the angular difference between the value in question
and the reference cycle. Pick a point on the conductor, and if it
carries either a standing or traveling wave (or any combination of
traveling waves at the reference frequency), the current at that point
is describable as a phasor (having a specific magnitude, and a
specific phase with respect to the reference cycle).

You have to admit, that's a weird phasor.
It's more akin to DC than anything else.

This is your mental block. A phasor describes the activity at a
point, not whether that activity is a result of an energy wave moving
past in one direction, the other, or some combination of those.

You need to get past this misconception that standing waves are not
current and are not describable by phasors.


Standing waves current is the superposition of two essentially equal
currents traveling in opposite directions.

No. Currents do not travel. Current is the movement of charge past a
point. Cyclic current is a sloshing back and forth of charge at some
frequency. If you want to picture that process with respect to time,
you can refer to it as a cycle or wave, but it is a wave on a scope
trace or time graph, not a physical wave of something moving along a
wire. The physical wave is charge slushing back and forth along the wire.

Both traveling energy waves and combinations of them (standing waves,
for example) involve energy traveling in various directions, but the
current does not travel. It occurs at a point, as charge moves back
and forth past that point. When you can separate the concept of
current from the concept of energy waves, you might see this snap into
focus.

I am not trying to be the guru, here. My earlier posts confused these
same concepts, when I mentioned current waves traveling in various
directions. I was mistaken, and have seen my error, and am trying to
get you to see it, also. I should have been speaking of charge waves
that produce current. Correct thinking requires correct speaking.
You cannot be sloppy with words and have (let alone express) clear
thoughts. This thread has done a lot to help me clear up both my
words and thoughts, and I thank you for that. I am not absolutely
sure that I have eliminated all mistakes from this way of talking
about the process under discussion, so I may have to make some more
corrections. That is the reason I am watching this thread.

If it was equal DC currents traveling in opposite directions,
what would the net current be?

Their algebraic sum, same as for non equal currents. Same for any
combination of currents that result from charge being shoved back and
forth by passing energy waves. Instantaneously the current is the
algebraic sum of all components passing through that point. If the
components are AC at the same frequency, the sum will be some
resultant instantaneous current that varies with that same frequency.

I think I agree with just about every conclusion you are making about
treating coils as slow wave transmission lines. The nits I am picking
is in the language you are using to describe these effects to justify
those conclusions. I think terminology is at the root of most of the
disagreements in this thread.

Roy Lewallen wrote:
The total current ("standing wave current" in Cecil's parlance)
certainly does have an associated phase angle, and its phasor certainly
does rotate.

The standing wave current phasor in a 1/2WL thin-wire dipole *DOES
NOT ROTATE* and is fixed *CONSTANT AT ZERO DEGREES*. Please reference
Figure 14-2 in Kraus' "Antennas for All Applications", 3rd edition,
page 464. It shows *ZERO* phase shift in the standing wave current
from tip to tip in the 1/2WL thin-wire antenna. It is obvious from
the standing wave current equation that the phase angle doesn't
change with position.

This one misconception is what has got you and Tom totally confused.
Please correct your misconception. It's the forward current phasor
and reflected current phasor that does the rotating. Since they are
rotating in opposite directions, the phasor sum of those two
phasors is essentially *CONSTANTLY ZERO ACCORDING TO Kraus*.

(By "phase" I mean time phase.) A sinusoidal traveling
current wave can be expressed as a phasor whose value is a function of
position. When you add a forward traveling wave to a reverse traveling
wave, you're adding two phasors. The result is a phasor whose value is
the vector sum of those two phasors. This is the total current. It has
magnitude and phase like any other phasor, and the same rotational speed
as its components. A common manifestation of this is the standing wave
pattern along a transmission line.

Roy, those two phasors that get added are *ROTATING IN OPPOSITE
DIRECTIONS!* The phase of the sum of those two phasors is *CONSTANT*!
If you had read: http://www.qsl.net/w5dxp/current.htm you would
know that already. That's the mistake that you and Tom have been
making for years and you are still making the same arrogant mistake.

Don't you believe what Gene Fuller posted?
************************************************** ******************
Regarding the cos(kz)*cos(wt) term in a standing wave:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe, there is no
remaining phase information. Any specific phase characteristics of the traveling
waves died out when the startup transients died out.

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. The so-called "phase reversal" in longer antennas is
not really about phase either. It is merely a representation of the periodic
sign reversal seen in a cosine function.
************************************************** *******************

In a transmission line with two current waves traveling in opposite
directions, the phase of the total wave changes with position along the
line.

No, it does NOT! at least not by more than a few degrees. In
Func(kx)*Func(wt), the phase is divorced from position on the line.
If you don't believe me, would you believe EZNEC? When I told Tom
that I had measured unchanging phase all along a dipole, you said
EZNEC shows the same thing.

Only in the special case where the two waves are equal in
amplitude (i.e., when the line is lossless and open or shorted at the
end) does the phase of the total current -- the sum of the forward and
reverse traveling waves -- turn out to be the same at all points along
the line. This can be easily seen from the very well known equations
describing wave behavior on transmission lines.

That's true. Now take a look at Kraus' diagram referenced above. Kraus
assumes the forward current and the reflected current on a 1/2WL thin-
wire dipole are *EQUAL* in magnitude. The same assumption is approximately
true for a 75m mobile antenna.

There's no special "standing wave current" that's a "misnomer" or which
is a phasor which "doesn't rotate". The total current is indeed a phasor
-- its rotation speed is the rotational frequency, 2 * pi * f, just like
the traveling wave components from which it can be made by simple addition.

Sorry, Roy, you are just wrong on that one. Please dust off your old
math book. Func(kx)*Func(wt) DOESN'T ROTATE with 'x'. For any 'x', it
just stands there exchanging energy between the E-field and H-field.

I think the problem Cecil is having ...

Methinks you had better do something about that beam in your own eye
rather than worry about the speck in mine.

... with it is that the currents on an
antenna behave in a manner that's similar to an open circuited
transmission line, which results in the phase angle of the total current
-- which can be represented as a phasor -- being the same at every point
along the line.

That's not a problem. That's exactly what Kraus and EZNEC both say.
You are the one having a problem with it and you really need to correct
your misconceptions before the discussion can progress.
--
73, Cecil http://www.qsl.net/w5dxp

Roy Lewallen wrote:
There's very little about Cecil's theories that I agree with.

But you did say EZNEC agreed with the phase measurements
I reported for my dipole, i.e. so close to zero I couldn't
tell any difference from zero.

This leaves you in the unenviable position of disagreeing
with (EZNEC and me).
--
73, Cecil http://www.qsl.net/w5dxp

John Popelish wrote:
He is so close, but still has a couple misconceptions blocking him.

If those are technical misconceptions, please
let's discuss them. Last time, when I rewrote
my posting to make the meaning clearer, you
agreed with it. Perhaps, this is also another
example of my poor writing style.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
John Popelish wrote:

He is so close, but still has a couple misconceptions blocking him.


If those are technical misconceptions, please
let's discuss them. Last time, when I rewrote
my posting to make the meaning clearer, you
agreed with it. Perhaps, this is also another
example of my poor writing style.

Or another mistake on my part. I am more interested in clearing up
the later. As far as what is happening in a loading coil, I am in
general agreement with you and EZNEC. It is only the details of the
discussion of the cause that I am still tripping over.

It may be you or I may have an untied shoe.

John Popelish wrote:

Cecil Moore wrote:
Exactly! Therefore, [standing wave phase] cannot be used to measure the phase shift
through a coil or even through a wire.

I agree, unless you use phase measurement to hunt for the location of
the current nodes that have moved as a result of adding the coil.
Finding a phase reversal at opposite ends of the coil, for instance,
implies that an odd number of nodes reside in the coil.

John, I didn't say the amplitude couldn't be used to determine
phase. The current nodes are associated wiht amplitudes, not phase.

A phasor rotates at the reference frequency, and with a phase angle that
represents the angular difference between the value in question and the
reference cycle. Pick a point on the conductor, and if it carries
either a standing or traveling wave (or any combination of traveling
waves at the reference frequency), the current at that point is
describable as a phasor (having a specific magnitude, and a specific
phase with respect to the reference cycle).

Yes, but the standing wave phasor doesn't change phase with position.
The traveling wave phasors change phase with position. That's a big
difference.

No. Currents do not travel. Current is the movement of charge past a
point.

So current doesn't flow and all the references to "current flow" are
wrong? If so, your task is a lot bigger than mine. May I suggest a
new thread titled, "Current Doesn't Flow".
--
73, Cecil http://www.qsl.net/w5dxp

John Popelish wrote:
It may be you or I may have an untied shoe.

In any case, Jim, oops, I mean John, here's the IEEE Dictionary's
definition of current.

"current - The flow of electrons within a wire or a circuit:
measured in ampheres." And no, there is no definition for
"current flow" in the IEEE Dictionary.

"Current flow" and "power flow" are commonly used terms to
signify "charge movement" and "energy movement". Objecting
to the use of the words "current flow" is really picking at
infinitessimal nits.
--
73, Cecil http://www.qsl.net/w5dxp

John Popelish wrote:
. . .
I think I agree with just about every conclusion you are making about
treating coils as slow wave transmission lines. . .

A coil itself isn't a slow wave transmission line. In conjunction with
shunt C, it can be analyzed as a transmission line, but only in
conjunction with shunt C. Remove the shunt C and it ceases looking like
a transmission line. The earlier example of the modification to Cecil's
EZNEC model illustrated this -- when the ground (the other side of the
shunt capacitor) was removed, the current drop across the coil disappeared.

As far as considering a coil itself as a "slow wave structure", Ramo and
Whinnery treat this subject. It's in the chapter on waveguides, and they
explain how a helix can operate as a slow wave waveguide structure. To
operate in this fashion requires that TM and TE modes be supported
inside the structure which in turn requires a coil diameter which is a
large part of a wavelength. Axial mode helix antennas, for example,
operate in this mode. Coils of the dimensions of loading coils in mobile
antennas are orders of magnitude too small to support the TM and TE
modes required for slow wave propagation.

Roy Lewallen, W7EL

Roy Lewallen wrote:
A coil itself isn't a slow wave transmission line. In conjunction with
shunt C, it can be analyzed as a transmission line, but only in
conjunction with shunt C.

A 75m bugcatcher has its own shunt C called "distributed capacitance".
It's what causes the self-resonant frequency of my 75m bugcatcher coil
to be only 60% higher than the 4 MHz operating frequency.

Remove the shunt C and it ceases looking like a transmission line.

That's true *only* for a lumped-circuit inductance. It is NOT true
for a 75m bugcatcher which has it very own distributed capacitance
built in. It is *IMPOSSIBLE* to remove the distributed shunt
capacitance from a 75m bugcatcher coil.

The earlier example of the modification to Cecil's
EZNEC model illustrated this -- when the ground (the other side of the
shunt capacitor) was removed, the current drop across the coil disappeared.

That may be true but please tell us how to remove the ground from a
75m mobile bugcatcher mobile antenna installation.

Coils of the dimensions of loading coils in mobile
antennas are orders of magnitude too small to support the TM and TE
modes required for slow wave propagation.

Sorry Roy, Dr. Corum disagrees with your statement. You really should
read the details of the Dr. Corum web page references that I posted.

His test for the validity of his helix equations is:

5*N*D^2/lamda(0) = 1 where N is number of turns, D is diameter,
and lamda(0) is the self-resonant frequency.

That value for my 75m bugcatcher coil is 0.4 so his equation for
velocity factor is valid. The velocity factor for my 75m bugcatcher
coil calculates out to be 0.0175. Now that's what I call a "slow
wave" coil.

But I have offered all these references weeks ago. Are you too
arrogant to even have read them? (Another rhetorical question)
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
John Popelish wrote:

Cecil Moore wrote:

I agree, unless you use phase measurement to hunt for the location of
the current nodes that have moved as a result of adding the coil.
Finding a phase reversal at opposite ends of the coil, for instance,
implies that an odd number of nodes reside in the coil.


John, I didn't say the amplitude couldn't be used to determine
phase. The current nodes are associated wiht amplitudes, not phase.

If you can measure phase, you can see that it is opposite on opposite
sides of a node. There is a 180 degree phase shift each time the
measurement passes over a node. Do you disagree?

A phasor rotates at the reference frequency, and with a phase angle
that represents the angular difference between the value in question
and the reference cycle. Pick a point on the conductor, and if it
carries either a standing or traveling wave (or any combination of
traveling waves at the reference frequency), the current at that point
is describable as a phasor (having a specific magnitude, and a
specific phase with respect to the reference cycle).


Yes, but the standing wave phasor doesn't change phase with position.
The traveling wave phasors change phase with position. That's a big
difference.

That's exactly the difference. But if you measure a single point, you
can't tell whether you are measuring a point on a traveling wave or a
standing wave. Agree?

No. Currents do not travel. Current is the movement of charge past a
point.


So current doesn't flow and all the references to "current flow" are
wrong?

Afraid so. The concept of current already includes the concept of
flow. Current is charge flow. Current flow is charge flow flow??

If so, your task is a lot bigger than mine. May I suggest a
new thread titled, "Current Doesn't Flow".

I wonder how long that thread would "flow".