John Popelish wrote:
Thanks much. This helps me to visualize your method in a much more
complete way. I think a photo of the test apparatus would make a fine
addition to your web page documenting this result. I am especially
interested on how all this stuff was arrayed in space during the test.

John, would you agree or disagree with me that for
a well-designed coil, the delay through the coil is
fixed by the laws of physics as 1/4WL on the self-
resonant frequency?

If the self-resonant frequency of a well-designed coil
is measured at 16 MHz, then the delay through the coil
is 90 degrees at 16 MHz and therefore equal to 15.625 nS.

Using the self-resonant frequency to determine the
delay is an easy and accurate way to measure that
delay.

If the delay through the coil, measured at 1/4 the
self-resonant frequency, is appreciably different
from the 15.6 nS measured at 16m, then the measurement
contains an error.

Agree/disagree?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
John Popelish wrote:

Thanks much. This helps me to visualize your method in a much more
complete way. I think a photo of the test apparatus would make a fine
addition to your web page documenting this result. I am especially
interested on how all this stuff was arrayed in space during the test.


John, would you agree or disagree with me that for
a well-designed coil, the delay through the coil is
fixed by the laws of physics as 1/4WL on the self-
resonant frequency?

I haven't formed a strong opinion either way, yet. I am not an
inductor expert, but am learning lots of interesting things, here. I
know that filters with sharp resonances (i.e. multiple db ripple
chebychev) often have a delay that varies dramatically over rather
narrow frequency ranges near cut off.

But I am finding the discussion and test results fascinating. I don't
care who has what opinion. I am just interested in what is factual,
and sometimes that can be tricky to determine and understand in a more
general context. That is why I am interested in the details of the
measurement method as much as I am in the result. I am still having a
bit of trouble visualizing how the coil was instrumented and
terminated to get this result. I am also a beginner when it comes to
S parameters.

My reservation with you and few others is your emotional investment in
being correct. It makes your opinions less trustworthy. I get the
feeling that some of you care more about having had the right answer
than what the result tells us about reality.

I have been wrong lots of times, and I got over it (sometimes with
difficulty). I accept that I will be wrong about lots more things
before I die. The best I can hope for is to realize my mistakes as
rapidly and gracefully as possible.

If the self-resonant frequency of a well-designed coil
is measured at 16 MHz, then the delay through the coil
is 90 degrees at 16 MHz and therefore equal to 15.625 nS.

Using the self-resonant frequency to determine the
delay is an easy and accurate way to measure that
delay.

For a pure delay process, like a classical transmission line, or
acoustic delay line, I agree. I am not so sure for something with
more ways energy communicates across it, like an extended inductor.

That is the open question, in my mind.

If the delay through the coil, measured at 1/4 the
self-resonant frequency, is appreciably different
from the 15.6 nS measured at 16m, then the measurement
contains an error.

Agree/disagree?

No. Not yet. When the test method has been agreed upon, and exactly
what that method measures is understood by all interested parties,
there will be no need for such opinions. The results will be the
results. Then we can work on our opinions of what the results mean in
a more general context (how we extrapolate to other, related, but
different cases.

John Popelish wrote:
I am still having a
bit of trouble visualizing how the coil was instrumented and terminated
to get this result. I am also a beginner when it comes to S parameters.

I think Tom did what I did the other night. I hooked the coil
across my IC-756PRO's output, used minimum power, and tried
to supply 4 MHz power to the 4+j1250 ohm coil that I have.
It naturally rejected (reflected) virtually all of that power.
I found, as Tom did, that the standing wave current at both
ends has virtually identical phases but that is already known.
The delay through the coil simply cannot be tested in that
test arrangement. Tom just repeated Roy's experiment of a
few years ago and obtained the same meaningless results.
So did I so I didn't even bother to report them.

My reservation with you and few others is your emotional
investment in being correct. It makes your opinions less
trustworthy.

Whoa there, I just made a mental blunder about radiation
resistance and readily admitted it. My emotional investment
is in fighting falsehoods, myths, and old wives' tales.
That's all.

The test method for determining the delay through a piece
of transmission line or a coil is the same as it has been
for more than a century. Find the 1/4WL self-resonant
point and calculate the delay. Other methods, resulting
in far different results, are obviously invalid.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
John Popelish wrote:

I am still having a bit of trouble visualizing how the coil was
instrumented and terminated to get this result. I am also a beginner
when it comes to S parameters.


I think Tom did what I did the other night. I hooked the coil
across my IC-756PRO's output, used minimum power, and tried
to supply 4 MHz power to the 4+j1250 ohm coil that I have.
It naturally rejected (reflected) virtually all of that power.
I found, as Tom did, that the standing wave current at both
ends has virtually identical phases but that is already known.
The delay through the coil simply cannot be tested in that
test arrangement. Tom just repeated Roy's experiment of a
few years ago and obtained the same meaningless results.
So did I so I didn't even bother to report them.

My reservation with you and few others is your emotional
investment in being correct. It makes your opinions less
trustworthy.

Whoa there, I just made a mental blunder about radiation
resistance and readily admitted it. My emotional investment
is in fighting falsehoods, myths, and old wives' tales.
That's all.

But the goal of such "fights" should be altering other's opinions.
How's that been working out for you? ;-)

The test method for determining the delay through a piece
of transmission line or a coil is the same as it has been
for more than a century.

Have you got a reference to a Bureau of Standards bulletin on this
method to measure inductive current delay? It doesn't work for
filters made of lumped inductors, capacitors and resistors.
Otherwise, there would not be special designs that sacrifice other
properties, to keep delay almost constant as frequency changes.

Wait a second, an inductor at resonance is a filter made of
inductance, capacitance and resistance (and transmission line
effects). Hmm.

Find the 1/4WL self-resonant
point and calculate the delay. Other methods, resulting
in far different results, are obviously invalid.

"Obvious" must be something in the eye of the beholder.

If a 2 port device (Are there really any perfect 2 port devices that
don't have an implied 3rd port?) involves only a single energy
transport mechanism from one port to the other, this is a bit closer
to obvious. But if the device uses competing, parallel energy
transport mechanisms (EM waves, inter turn capacitance, mutual
inductance, etc.) it is less clear that the combination of energy
transport effects has a constant delay effect on a current wave as
frequency changes.

John Popelish wrote:
But the goal of such "fights" should be altering other's opinions. How's
that been working out for you? ;-)

That's not my goal at all, John. My goal is to discuss the
technical facts. I really don't care if anyone "alters
their opinions" or not. That has been a personality
characteristic since my early days. My sister just
remarked on that same fact a few days ago. She said,
"You have never cared what other people think about
you." It wasn't a criticism, just an observation.

We may understand the results of Tom's latest
measurement by considering the following:

50 ohm source===1 WL 50 ohm lossless coax===8+j2500 load

Since the transmission line is lossless, this doesn't
change anything except for the additional one cycle delay
through the line.

What's the system SWR? I get 16000:1. I asked Tom
to measure the currents in the absence of a high SWR
and he takes his measurements in a 16000:1 SWR
environment. How well do you think he honored my
request for an SWR of 1:1? Shucks, he only missed
it by 1,600,000%. :-)

There is essentially no net energy flow in the above
network. Why are we suprised to measure equal standing
wave currents on each side of the coil? It wouldn't have
surprised me if Tom had measured *zero* phase shift just
like the lumped-circuit model predicts. The traveling-
wave delay through a coil simply cannot be measured
using Tom's methods.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
(snip)
We may understand the results of Tom's latest
measurement by considering the following:

50 ohm source===1 WL 50 ohm lossless coax===8+j2500 load
(snip)

I am not sure I understand this. As I understand an S parameter
tester, both source and load are 50 ohms. Tom says he fed and
monitored the signal with a pair of current transformers. I assume
that one transformer was fed from the 50 ohm source, and the other fed
the 50 ohm load, and S21 is the forward transfer gain parameter that
the analyzer can use to calculate a net delay at any frequency. But
if I am right about these connections, it leaves open the question of
what was on the other side of the current transformers, if the coil
was between them. Were those points grounded, terminated, what?

John Popelish wrote:

Cecil Moore wrote:
We may understand the results of Tom's latest
measurement by considering the following:

50 ohm source===1 WL 50 ohm lossless coax===8+j2500 load

I am not sure I understand this. As I understand an S parameter tester,
both source and load are 50 ohms. Tom says he fed and monitored the
signal with a pair of current transformers.

I don't think he fed the coil with a current transformer.
I think he simply had the coil across the signal generator's
output terminals with current pickup devices at each end
of the coil. The above diagram doesn't change anything
about his configuration but does point out the conceptual
mistake he made which is the identical conceptual mistake
that he and Roy have been making for years. Their model
presupposes their measured results. How could their
results be anything else?
--
73, Cecil http://www.qsl.net/w5dxp