Current through coils
 

"Reg Edwards" wrote:
But the propagation delay, with a true transmission line, should be
constant versus frequency as it depends only on coil dimensions and
hence on L and C. The velocity factor should also be a constant.

Reg, if the SWR on a piece of transmission line is infinite and one tries
to use the standing wave current phase to measure the propagation
delay in a piece of that transmission line, what would be the result?
--
73, Cecil, W5DXP

Current through coils
 

Sorry Cec, but I havn't the foggiest idea what you are talking about.
----
Reg

=========================================
"Cecil Moore" wrote in message
. com...

"Reg Edwards" wrote:
But the propagation delay, with a true transmission line, should
be
constant versus frequency as it depends only on coil dimensions
and
hence on L and C. The velocity factor should also be a constant.

Reg, if the SWR on a piece of transmission line is infinite and one
tries
to use the standing wave current phase to measure the propagation
delay in a piece of that transmission line, what would be the
result?
--
73, Cecil, W5DXP

Current through coils
 

"Reg Edwards" wrote:
Sorry Cec, but I havn't the foggiest idea what you are talking about.

Let me ask it a little differently. We all know what a plot of the standing
wave current magnitude looks like up and down an open-circuit transmission
line.

But what does a plot of the associated standing wave current *phase* look
like up and down that same open-circuited transmission line?
--
73, Cecil, W5DXP

Current through coils
 

Tom, W8JI wrote:
"Many people vizualize current in a small loading inductor as starting
at one end and traveling through the conductor turn-by-turn.

That`s how the experts say the coul in a TWT works, and it is no
different from other coils.

RF energy travels in waves which induce currents on conductors in their
paths which in turn induce more waves.

Energy has no choice but to follow the conductor. It is nonsense to say
this is not the means used by energy traveling through an inductor while
riding on its surface due to skin effect. The energy follows the
conductor wrapping its way around the form fron start to finish.

Energy hits the speed limit of physics if it can at 300,000,000 meters
per second. but
its interaction with any conductor slows it depending on the
characteristics of the conductor guiding it.

An inductor reduces the group velocity (actual energy velocity) of any
wave traveling along its surface. The group velocity is always less than
the velocity of light (300,000,000 m/sec.). Phase velocity may exceed
the velocity of light but only to the extent that the actual group
velocity is slower than the velocity of light.

An inductor reduces the group velocity of a wave traveling upn is
surface.Inductors are also known as "retardation coils".

The RF`s changing current generates waves. In an inductor, it ideally
lags voltage across that inductor (as a circuiy element) by 90-degrees.
Time represented by a 90-degree delay can be calculated by: velocity =
frequency x wavelength. 90-degrees is 1/4-wavelength.

It is possible to measure the delay of a circuit but when your
measurement seems to violate the laws of physics it`s more likely your
measurement was flawed than you have discovered any new physics.

Tight coupling does not speed transfer of energy through a coil. TWT
coils are tightly coupled. Remember, the coil does not allow current to
change instantly. Lenz`s law prevails. Current lag enforces a delay.

Tom also wrote on "Welcome to W8JI.com":
"An inductor delays the flow of current in relationship to applied
voltages as the magnetic field inside the coil expands. Voltage
increases before current starts to flow. This phase relationship berween
voltage and current is often confused with time delay in the inductor."

I`m done with my critique only because I`m out of time.

Best regards, Richard Harrison, KB5WZI

Current through coils
 

"Cecil Moore" wrote in message
. net...
"Reg Edwards" wrote:
Sorry Cec, but I havn't the foggiest idea what you are talking
about.

Let me ask it a little differently. We all know what a plot of the
standing
wave current magnitude looks like up and down an open-circuit
transmission
line.

But what does a plot of the associated standing wave current *phase*
look
like up and down that same open-circuited transmission line?
--
73, Cecil, W5DXP

================================
What is 'phase'?
---
Reg.

Current through coils
 

"Reg Edwards" wrote:
What is 'phase'?

I'll send you a .jpg image of a page from Kraus's book.
Phase is the phase of a phasor. :-)
--
73, Cecil, W5DXP
..

Current through coils
 

Cecil Moore wrote:
"Reg Edwards" wrote:

Sorry Cec, but I havn't the foggiest idea what you are talking about.


Let me ask it a little differently. We all know what a plot of the standing
wave current magnitude looks like up and down an open-circuit transmission
line.

But what does a plot of the associated standing wave current *phase* look
like up and down that same open-circuited transmission line?
--
73, Cecil, W5DXP



By now you should be able to calculate that, Cecil.
73,
Tom Donaly, KA6RUH

Current through coils
 

Tom Donaly wrote:
Cecil Moore wrote:
"Reg Edwards" wrote:

Sorry Cec, but I havn't the foggiest idea what you are talking about.


Let me ask it a little differently. We all know what a plot of the
standing
wave current magnitude looks like up and down an open-circuit
transmission
line.

But what does a plot of the associated standing wave current *phase* look
like up and down that same open-circuited transmission line?
--
73, Cecil, W5DXP



By now you should be able to calculate that, Cecil.
73,
Tom Donaly, KA6RUH

Indeed. And I even gave the answer some time ago -- the phase of the
total current (which Cecil seems to like calling the "standing wave"
current) is the same all along the line. That's true only for the case
of a line that's completely short or open circuited. In any other case,
the phase of total voltage and current vary along the line. This can be
easily calculated by adding the values of the forward and reverse
traveling waves at each point to get the total at each point. Or, if
you're lazy, just plug the numbers into the equations you'll find in
_Reference Data for Radio Engineers_ or your favorite reference. Or if
you're lazier yet you can model a transmission line with EZNEC or the
modeling program of your choice and let it tell you what the phase of
the current is at each point along the line. Any of the three methods
will give the same result if done correctly.

As I mentioned before, a plucked guitar string is a good physical
analogy. Each point along the string moves in the same direction at the
same time, showing that the motions at all points along the string are
in phase.

That's very basic transmission line theory. If Cecil really doesn't know
the answer to the question he asked, it's no wonder he has such
conceptual problems with inductors and transmission lines.

Roy Lewallen, W7EL

Current through coils
 

Richard Harrison wrote:
Tom, W8JI wrote:
"Many people vizualize current in a small loading inductor as starting
at one end and traveling through the conductor turn-by-turn.

That`s how the experts say the coul in a TWT works, and it is no
different from other coils.


That's not correct at all Richard. The coil in a TWT tube behaves
considerably different than a small inductor operted at a low
frequency.

Nearly everyone on this thread seems to understand mutal coupling is
very high in a conventional loading inductor. This is why the inductor
comes close to following a square of the turns change in inductance. A
TWT has a loose coil operated in an entitrely different mode, behaving
much more like a axial mode helice than an inductor.

It can easily be proven inductors don't behave the same way when they
have wide turns spacing and long form factor and low values of
distributed capacitive reactance to the outhside world...when compared
to an inductor who's displacement current is very low compared to
through current.

Coils or inductors can range from having very low phase difference
between each terminal (almost immeasureable) to very high values (a
helical antenna or tesla coil at resonance).

The only real argument against this seems to be from Cecil, and as I
understood it he thinks standing waves are what causes current to be
different at each end and somehow sets the phase difference between
ends of the inductor.

I can have a fixed style of antenna on a fixed frequency, change only
the inductor design, and go from something that almost perfectly
behaves like a lumped component to something that has noticable current
taper across the component.

Most people had this stuff right from about post one.

I rarely see a thread go nowhere like this one has. It reminds me of
the Fractal antenna threads years ago, or that silly conjugate match
stuff that went on for years and years.

800 posts later the same major group of people seem to agree, the same
one or two people seem to think something magical occurs in an antenna
making a regular lumped inductor behave like a self-resonant helice
with standing waves and all.

It's sure a time waster.

73 Tom

Current through coils
 

Roy Lewallen wrote:
Indeed. And I even gave the answer some time ago -- the phase of the
total current (which Cecil seems to like calling the "standing wave"
current) is the same all along the line.

But Roy, you measured the phase of the standing wave current to
try to convince us there was no phase shift through a loading
coil. You cannot have it both ways. You cannot use the phase
of the standing wave current to measure a phase shift through
a loading coil and then tell us the phase of the standing wave
current is the same all along the line. So which story are you
going to chose?

I suspect that when you made those measurements, you didn't
realize that standing wave antennas have standing wave currents
and that the currents reported by EZNEC for standing wave
antennas are standing wave currents with unchanging phase.

If the phase of the standing wave current cannot be used to
measure the delay through a wire, what made you think it could
be used to measure the delay through a loading coil?
--
73, Cecil http://www.qsl.net/w5dxp