Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
John Popelish wrote:

See all those arrows of various length representing current direction
and magnitude? Why do you ask me about something after erasing my
answer?


As is my custom, I erase everything I agree with.

If the source were known to be to the left, would that change
your answer?


For a pure standing wave, there is effectively a source at each end,
so this question is meaningless.


Exactly! Now try to tell that to W8JI and W7EL who attempt to
assign a direction of flow to standing wave current and use
its phase to determine the phase shift through a wire or coil.

Not my job.

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
John Popelish wrote:

So, add some transmission line to the system so a node's location is
measurable inside the system. By the way, in case you didn't notice,
I am agreeing with you, and elaborating on what you are saying.


I know you are agreeing with me. The only disagreement you
and I have ever had was over my poor choice of words.

Read on.

I just posted something that disagrees with you about something
fundamental. I have no intention of bucking you or supporting you.

I am interested in understanding.

Current across the antenna loading coil - from scratch
 

wrote:
The current in the wire must be in one of two directions, since that is
the only path the wire can provide.

In which direction is that current flowing when its phase
is unchanging with respect to the source?

Any conductor with changing voltage has displacement
current to ite surroundings.

Which are quite often negligible compared to the effect
of the phasor addition of forward and reflected currents.
All I am saying is that the displacement current to ground
is often a secondary effect which can be ignored when only
primary effects are being considered.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

On Sat, 08 Apr 2006 20:30:32 GMT, Cecil Moore
wrote:

Richard Clark wrote:
Cecil Moore wrote:
an SWR meter
Who said anything about the meter movement?

Ta Dah!

No current, no SWR indication.

Current across the antenna loading coil - from scratch
 

On Sat, 08 Apr 2006 10:21:08 -0700, Richard Clark
wrote:

As usual, the question is nonsense when the picture reveals the
answer. Cecil rarely sees the irony - except to brush it off as
1. Rhetoric (no answer needed, an admission of wasting time);
2. Our error for not knowing he made a squinty-eyed mistake
(playing the pity card);
3. A joke (having forgotten one of a bajillion happy faces);
4. His poor choice of words (playing the pity card - 3 of Hearts);

Always room for one more excuse (to be continued).

The challenge continues without upset or serious contest:

The current is flowing in the SWR meter. DUH!

I would, of course, task any/everyone to find any point along the line
where the SWR meter does not exhibit current flow for this
configuration. :-)

Quod Erat Demonstrandum

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

Richard Clark wrote:
"No current, no SWR."

That exact spot producing an SWR induced voltage cancellation must also
have double the voltage of either the forward or reverse wave. Voltage
maxima are concurrent with current minima.

Your SWR meter needs to be able to give a good indication at any spot in
the line including all maxima and minima.

Best regards, Richard Harrison, KB5WZI

Current across the antenna loading coil - from scratch
 

Richard Harrison wrote:
Richard Clark wrote:
"No current, no SWR."

That exact spot producing an SWR induced voltage cancellation must also
have double the voltage of either the forward or reverse wave. Voltage
maxima are concurrent with current minima.

Your SWR meter needs to be able to give a good indication at any spot in
the line including all maxima and minima.

Yes, what happens if the current sample is zero is that the
forward power indication and reflected power indication are
the same and indeed Vv - Vi = Vv + Vi = Vv. The indicated
forward power and reflected power are equal just as they
should be.

But the trivial point that Richard C. was making is that the
meter movement requires current - true but completely
irrelevant.
--
73, Cecil http://www.qsl.net/w5dxp

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
Are you actually saying charges flow two directions at the same time
and place in any given snapshot of time?

Cecil wrote:

Water waves flow two directions at the same time using the same
water molecules. EM waves flow two directions at the same time
using the same carriers. Waves in a rope travel two directions
at the same time using the same molecules. It is a common physical
occurrence. Hint: The carriers of the waves are NOT the same thing
as the waves.

Current is by definition is the flow of charge.

A current of one coulomb per second is one ampere.

By definition and by physics, we cannot have charges flowing two
directions at once at one point. Even if we had some strange mechanism
in the conductor allowing this, radiation and the phase of EM fields
would be determined by the net charge movement.

This is precisely the current we would measure with a current meter
sampling the magnetic field, it is the current we would measure
sampling radiation, and it is the current that would determine phase of
the radiation or induction field.

So please expain to use, even if we allow a conductor to have TWO
voltage gradients of opposite polarity over the same linear area of
conductor, why Cecil's Current is important.

Also, tell us how we can measure and prove in a repeatable test, the
two-way charge movement exists.

The current we would measure at any place with a current indicator and
the phase of that current IS the actual current flow.

What direction is that current flowing when its phase is not
changing relative to the source phase? This is a key question.

Either you are creating diversionary conundrums, or you should be able
to explain how we can have charges moving past a point in a single
conductor that are moving both directions at one instant of time. Tell
us how that happens. Tell us why we suddenly cannot use drift velocity
to calculate current, or current to calculate drift velocity.

The almost universal measurement method of current is magnetic.
Suddenly Cecil's Theory of Current renders universal measurement
methods obsolete!

NEC uses current and voltage, not wave theory. You attempt to use an
engine that uses what you say we can use to prove we are wrong in using
current when there are standing waves!

Don't you think you should have understood the NEC engine used in the
program before using it to prove we cannot use current without
reflections? Eznec uses the very same thing we can measure with a clamp
on meter, so it appears you are the one who is doing something wrong.


It is impossible to have different currents at each end of the inductor
without having displacement currents, or what Reg calls "radial current
flow".

We have different currents at each end of a wire quite often
without having displacement currents. Does having zero amps
and one point and one amp 1/4WL away mean there's displacement
current in a transmission line?

Yes, absolutely. If you don't understand that, you'd better review
basic transmission lines and quit wasting everyone else's time giving
assignments.

When you figure out the answer
to that one, you will understand why the coil can have negligible
displacement current and still have zero amps at one end and
one amp at the other end, just like the wire or transmission line.

Nonsense Cecil. I'd wager almost everyone here understands transmission
lines better than that!

It appears you have wandered off into the land of reflections without
also understanding basic circuits. The transmission line can be
represented as a network of series inductors and shunt capacitors, just
as an antenna (even a single conductor) in space can. The only reason
current changes is displacement currents (the electric field) allow
current to decrease by providing the third path.

If we stopped that third path, the current would not change.

We can analyze any stub with EXACTLY the same results wave theory
produces. Other than imperfect precision in both methods, the results
are the same.

The minute any of us start thinking there is only one model, either
circuit or wave theory, that works and we cannot fit the other method
with the same results, it shows something is wrong. Your model, if you
rule out displacement currents, cannot work. Your model, if it requires
net current flow that does not register as a magnetic induction field
or as a thermal effect, and if the radiation phase and level is not
tied to the same ampere-feet we measure with conventional
instrumentation, is a fantasy.

Go back to what makes charges move, and explian how thay can move two
directions at the same time in a very small crossection of conductor in
terms of the wavelength.

Answer the question Cecil, how can we have charge movement over a small
length of conductor (in terms of the wavelength) in two directions at
the same time, or a drift velocity in two directions at once?

73 Tom

Current across the antenna loading coil - from scratch
 

Richard Clark wrote:


********** W R O N G !! *************

No meter movement moves without current!

Ta Dah!

Richard is wrong too! There are electrostatic meter movements.

73, Roger

--
Remove tilde (~) to reply

Remember the USS Liberty (AGTR-5)
http://ussliberty.org/

Current across the antenna loading coil - from scratch
 

Cecil Moore wrote:
wrote:

The current in the wire must be in one of two directions, since that is
the only path the wire can provide.


In which direction is that current flowing when its phase
is unchanging with respect to the source?

At any point along the wire, and at any particular instant, whether as
a result of a standing or traveling wave, the current flows in the
direction of the wire, one way or the other. Such current does not
have a phase. It has a direction. The sinusoidal cycle of variation
through time is what has a phase with respect to some reference. The
cycle of current in a standing wave, at any point has one of only two
phases.

There is also a current at any point that passes between the surface
of the wire and the surroundings (capacitive current), but you don't
generally measure or describe that current when dealing with antenna
elements, transmission lines or coils. You generally quantify only
the current in the direction of the wire. But it is the displacement
current radial to the wire that is responsible for all variation of
current (magnitude and phase) along a conductor.

Any conductor with changing voltage has displacement
current to ite surroundings.

Which are quite often negligible compared to the effect
of the phasor addition of forward and reflected currents.

Those wave currents could not travel at nearly the speed of light
without the displacement currents. They are what set the wave
velocity (in conjunction with the inductance per length). They can
never be forgotten when dealing with waves. They allow waves to happen.

All I am saying is that the displacement current to ground
is often a secondary effect which can be ignored when only
primary effects are being considered.

Then you are silly. You cannot describe the reason for wave velocity
of a conductor, transmission line or EM wave without displacement
current. It would like trying to describe water surface waves without
referring to the density of water.

For instance, when there is a standing wave current node, and current
is toward that node (charge is piling up), from both sides, where do
you think it is going?

There is only one place.

Displacement current into the space around the node.

And at the node where current is instantaneously heading from the
node, in both directions (that is what 180 degrees across the node
means), simultaneously, there is only one place it can come from.
Displacement current from the space around that node.

If you superimpose the graph of standing wave voltage along the line
with the graph of standing wave current, you will see that the voltage
wave has its peaks at the current nodes, and it is this large voltage
swing that is driving the peak displacement current at those points.

So please stop saying that displacement current is negligible in some
cases of traveling or standing waves. It is a silly thing to say.