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.