Roy Lewallen wrote:
A standing wave is the result of, and the sum of, two or more traveling
waves. There aren't points which are "on" one or the other. If you can
separately measure or calculate the values of the traveling current
waves at any point, you can add them to get the total current (what
Cecil calls "standing wave current") at that point. If you add the
traveling current waves at each point along the line and plot the
amplitude of the sum (that is, of the total current) versus position,
you see a periodic relationship between the amplitude and position. It's
this relationship which is called a "standing wave". It's so called
because its position relative to the line stays fixed. It's simply a
graph of the total current (the sum of the traveling waves) vs. position.

And there's no such thing as current imbalance based on standing
wave currents being different at each end of a loading coil.
"Current imbalance" is a concept that doesn't apply to standing
waves. "Phase rotation with position" is a concept that doesn't
apply to standing waves. Standing wave current is NOT ordinary
current. It is the superposition of two ordinary currents.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

And there's no such thing as current imbalance based on standing
wave currents being different at each end of a loading coil.
"Current imbalance" is a concept that doesn't apply to standing
waves. "Phase rotation with position" is a concept that doesn't
apply to standing waves. Standing wave current is NOT ordinary
current. It is the superposition of two ordinary currents.

You two are so close to agreement. Standing waves have a current that
varies with position. The fact that the EZNEC simulation of a loading
coil shows differing current in a situation that is a fairly pure
standing wave situation (more energy bouncing up and down the antenna
than is radiating from it) means that the RMS current will vary along
the standing wave. And, since the simulation shows a different
current magnitude at the two ends of the coil, a significant part of a
standing wave cycle must reside inside the coil (more than the
physical length between the two ends of the coil would account for).

In one case (the highest frequency one) the phase of the current even
reverses from one end of the coil to the other, as well as an
amplitude variation, indicating that a standing wave node occurs some
where inside the coil, and the two ends are on opposite ends of that
node. If the two currents had been equal, but 180 degrees out of
phase, the node would have been in the center of the coil.

John Popelish wrote:

You two are so close to agreement. Standing waves have a current that
varies with position. The fact that the EZNEC simulation of a loading
coil shows differing current in a situation that is a fairly pure
standing wave situation (more energy bouncing up and down the antenna
than is radiating from it) means that the RMS current will vary along
the standing wave. And, since the simulation shows a different current
magnitude at the two ends of the coil, a significant part of a standing
wave cycle must reside inside the coil (more than the physical length
between the two ends of the coil would account for).

No, you're misinterpreting what you're seeing. Imagine an LC L network
with theoretically lumped series L and shunt C. If you look at the
currents at the input and output of the perfect inductor, you'll find
that they're exactly the same. If, however, you look at the currents in
and out of the *network* you'll see that they're different, because of
current going to ground through the C. And, as I said before, you can
even pretend it's a transmission line and measure forward and reverse
traveling waves and a standing wave ratio. But with zero length, there
can be no standing waves inside the inductor. Yet the terminal
characteristics of the network are the same as a transmission line. You
don't need to imagine standing waves residing inside the inductor in the
LC circuit, and you don't need to imagine them inside the inductor in
Cecil's model, either.

When you look at the currents reported by EZNEC for the model on Cecil's
web page, the current at the top of the coil is the equivalent to the
*network* current described above. It's the current flowing through the
inductance minus the current being shunted to ground via the C between
the coil and ground. You can tell just how much this is by looking at my
modified model and subtracting the current going into the coil from
ground from the current going into ground from the added wire. They're
not the same -- the difference is the displacement current through the C
from the inductor to ground. When I removed the ground, you could then
see the current flowing through the inductor, by itself, without the
current being shunted off. And lo and behold, it's nearly the same at
both ends of the inductor, showing that the inductor is behaving very
much like a lumped L. Only in conjunction with the C to ground does the
combination mimic a transmission line -- just like any other lumped LC
circuit.

Of course, at some length and/or poorness of interturn coupling, a coil
will start behaving in a way we can't adequately model as a lumped L.
But that's not the case here.

. . .

Roy Lewallen, W7EL

Roy Lewallen wrote:
If, however, you look at the currents in
and out of the *network* you'll see that they're different, because of
current going to ground through the C.

The main effect in a standing wave environment are the forward
and reflected phasors rotating in opposite directions. The
standing wave current is ZERO when those phasors are 180 degrees
out of phase. The standing wave current is maximum when those
phasors are in phase. "Current going to ground through the C"
is not even required.

But with zero length, there
can be no standing waves inside the inductor.

You keep saying stuff like this as if a zero length inductor
actually existed in reality. Wake up, Roy, and smell the
roses. That zero length inductor exists only in human minds.


When you look at the currents reported by EZNEC for the model on Cecil's
web page, the current at the top of the coil is the equivalent to the
*network* current described above. It's the current flowing through the
inductance minus the current being shunted to ground via the C between
the coil and ground.

Huh? How do you explain the current at the top being greater than
the current at the bottom of the coil? Is the coil sucking current
from the ground?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Roy Lewallen wrote:
If, however, you look at the currents in
and out of the *network* you'll see that they're different, because of
current going to ground through the C.

The main effect in a standing wave environment are the forward
and reflected phasors rotating in opposite directions. The
standing wave current is ZERO when those phasors are 180 degrees
out of phase. The standing wave current is maximum when those
phasors are in phase. "Current going to ground through the C"
is not even required.

That's utter nonsense Cecil, and why people aren't buying into your
misconceived theories.
Maybe you can take some time to rethink your position while on
vacation.

A two-terminal network that transforms impedance, now there's a
concept!

An inductor behaves exactly the same way in or out of your so-called
standing wave environment. It follows the same rules all the time.

Since your theory says otherwise, it has to be wrong.

Wave theory is just another way of analyzing a complex system. It
doesn't change how things inside the system behave.

73 Tom

wrote:
That's utter nonsense Cecil, and why people aren't buying into your
misconceived theories.

Sorry, Tom, that's distributed network analysis, something you
and others seem to be totally ignorant of and confused by.

I get emails every week from people who are buying into the
distributed network analysis. Otherwise, they are forced to
accept your magical thinking about reality.

A two-terminal network that transforms impedance, now there's a
concept!

It isn't a two-terminal network. It is a single-wire transmission
line over ground. It has forward and reflected waves working against
ground, similar to a two-wire transmission line.

An inductor behaves exactly the same way in or out of your so-called
standing wave environment. It follows the same rules all the time.

Quoting Dr. Corum again: "There are no standing waves [allowed]
on a lumped element circuit component. (In fact, lumped-element
circuit theory inherently employs the cosmological presupposition
that the speed of light is infinite, as every EE sophmore should
know.)"

"Lumped circuit theory fails because it's a theory whose
presuppositions are inadequate. Every EE in the world was warned
of this in their first sophmore circuits course."

Tom, where did you attend your sophmore EE classes?

Since your theory says otherwise, it has to be wrong.

It is the distributed network theory, Tom, developed to handle
just such cases of failure of the lumped-element model. Both
models work in some instances. The distributed network model
works when the lumped-element model fails.

Wave theory is just another way of analyzing a complex system. It
doesn't change how things inside the system behave.

Exactly! But lumped-circuit theory changes how things inside
the system behave when standing waves are present. One can
observe its magical effects in your explanations. Unfortunately,
it is not supposed to change anything. When a model tries to change
the laws of physics, it's time to move to a more power model that
doesn't.

Bottom line: By every valid measurement and calculation, a 75m
bugcatcher coil occupies roughly 60% of a mobile antenna.
--
73, Cecil http://www.qsl.net/w5dxp

wrote:

A two-terminal network that transforms impedance, now there's a
concept!

(My opinion follows, please correct me. Dang, I should put that in my
sig.)

In reality, there is no such thing as a two terminal network, unless
one of those terminals is grounded. For all other cases, there is an
unavoidable implied ground terminal that covers all the stray
capacitance of the device.

So the bug catcher coil is recognized as a 3 terminal device, with
ground being the third terminal. It can be modeled as a pi, T or
transmission line structure, as long as you want to understand what to
quantify it at only one frequency (or a narrow band), and the choice
is arbitrary. If you are concerned with modeling a large frequency
range (that goes well past the first self resonance), one of those
models (or a more complicated one) will be superior.

John Popelish wrote:
wrote:

A two-terminal network that transforms impedance, now there's a
concept!


(My opinion follows, please correct me. Dang, I should put that in my
sig.)

In reality, there is no such thing as a two terminal network, unless one
of those terminals is grounded. For all other cases, there is an
unavoidable implied ground terminal that covers all the stray
capacitance of the device.

So the bug catcher coil is recognized as a 3 terminal device, with
ground being the third terminal. It can be modeled as a pi, T or
transmission line structure, as long as you want to understand what to
quantify it at only one frequency (or a narrow band), and the choice is
arbitrary. If you are concerned with modeling a large frequency range
(that goes well past the first self resonance), one of those models (or
a more complicated one) will be superior.

You fellows lack imagination. As long as you're trying to morph a coil
into a transmission line, why not just imagine it as a shorted stub?
There's more than one way to make an inductive reactance.
73,
Tom Donaly, KA6RUH

Roy Lewallen wrote:
John Popelish wrote:

No, you're misinterpreting what you're seeing. Imagine an LC L network
with theoretically lumped series L and shunt C.

Okay, I am imagining an idealized, network made of perfect, impossible
components that is simple to analyze. Got it.

If you look at the
currents at the input and output of the perfect inductor, you'll find
that they're exactly the same.

Right.

If, however, you look at the currents in
and out of the *network* you'll see that they're different, because of
current going to ground through the C.

Got it. Same for any pi, T, or more complicated LC network.

And, as I said before, you can
even pretend it's a transmission line and measure forward and reverse
traveling waves and a standing wave ratio.

Yes. Under some specific conditions.

But with zero length, there
can be no standing waves inside the inductor.

Yes. There are no waves in a single ideal lumped component, so there
can be no waves inside any of them, only a phase shift between the
voltage across them and the current through them. But a network made
of them can mimic lots of processes that internally involve
propagation of waves, including the phase shift between voltages
across the terminals and current into the terminals, and even group
delay, but only over narrow frequency range. It is a model with this
severe limitation.

Yet the terminal
characteristics of the network are the same as a transmission line. You
don't need to imagine standing waves residing inside the inductor in the
LC circuit, and you don't need to imagine them inside the inductor in
Cecil's model, either.
(snip)

Whether or not we need to imagine them to picture what is happening at
the terminals is not the question at hand. The question in my mind is
what is the actual mechanism, inside the device in question that is
causing the effects we see at the terminals. I am not interested in
the full range of models that predict the effect, but in the actual
cause. I accept that my motivation is not necessarily the same as yours.

John Popelish wrote:
Standing waves have a current that
varies with position. The fact that the EZNEC simulation of a loading
coil shows differing current in a situation that is a fairly pure
standing wave situation (more energy bouncing up and down the antenna
than is radiating from it) means that the RMS current will vary along
the standing wave. And, since the simulation shows a different current
magnitude at the two ends of the coil, a significant part of a standing
wave cycle must reside inside the coil (more than the physical length
between the two ends of the coil would account for).

And since a significant part of a standing wave cycle resides inside
the coil, it occupies a non-negligible percentage of a wavelength.
By every valid method, measured or calculated, a 75m bugcatcher
coil occupies tens of degrees of a wavelength (out of 360 degrees).
My best estimate is 60 degrees in a 75m mobile antenna.

In one case (the highest frequency one) the phase of the current even
reverses from one end of the coil to the other, as well as an amplitude
variation, indicating that a standing wave node occurs some where inside
the coil, and the two ends are on opposite ends of that node. If the
two currents had been equal, but 180 degrees out of phase, the node
would have been in the center of the coil.

Yes, if a current node exists inside a coil, the standing wave currents
are flowing into the coil at the same time from both ends and 1/2 cycle
later they are both flowing out of the coil at the same time. Wonder
how a lumped-circuit inductance handles that? :-)
--
73, Cecil http://www.qsl.net/w5dxp