RadioBanter - View Single Post

March 12th 06, 12:34 AM posted to rec.radio.amateur.antenna

wrote:
I offered to make a measurement if he would even loosely predict
results and tell us in advance what they would mean. When he didn't
respond, I made the measurements anyway.

Huh? I predicted 14 degrees at 1.9 MHz and 28 degrees at 3.8 MHz
based on Reg's assertion that the coil was self-resonant at 12 MHz.
Once you know the self-resonant frequency, the VF can be calculated.
From there, one can calculate a ballpark delay through the coil.
Your 3 nS measurement seems outside of all possiblity.

This is really simple physics, Tom. If your measurements disagree
with the boundary conditions set by the laws of distributed-
network physics then something is wrong with your measurements.

Let's take a closer look. If the delay through the coil is indeed
3 nS at 4 MHz, the phase shift through the coil at 4 MHz is 4.32
degrees. For a self-resonant phase shift of 90 degrees, the self-
resonant frequency of the coil has to be near (90/4.32)4 MHz =
83 MHz. Now if the self-resonant frequency is really 83 MHz, all
is well, and your measurements agree with distributed network
theory.

But, Tom, don't you think you are insulting our intelligence when
your 100uH coil must have a self-resonant frequency of 83 MHz and
a velocity factor of 0.28 for your measurements to be valid? My
75m bugcatcher coil has a VF of 0.015. Why is your coil 20 times
better than my bugcatcher?

And I have that same coil with 68.5 turns but it is self-resonant
at 57 MHz. How do you explain 2/3 of the number of turns being
self-resonant 25 MHz lower? If you cannot, something is wrong with
your measurements. Don't you care that your 3 nS results are so
outside the bounds of possibility as to be laughable?

Please measure the self-resonant frequency of that coil, Tom.
If it's not 83 MHz, your measurements are bogus. I suggest the
self-resonant frequency is actually lower than the 12 MHz
predicted by Reg.

Incidentally, the IEEE would surely be interested in your ability
to violate the distributed-network laws of physics. Maybe you
can talk them into replacing that body of physics with your pet
lumped-circuit model. Good luck on that one.

3 nS delay through a 100 uH coil???? That would be funny if it
was April First. That's why I requested that you describe your
test setup which you refused to do.
--
73, Cecil http://www.qsl.net/w5dxp