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Old March 26th 06, 05:39 PM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Current through coils

John Popelish wrote:
Can you use this example, with varying frequency to explore your
assertion that the time delay (frequency times phase shift) of the coil
varies little over a significant range of frequencies up to self
resonance, and that that delay is about 1/4 cycle of the self resonant
frequency?


I will do that when my energy level returns after getting
home at 2 am this morning. Note that anyone can download
the EZNEC file from http://www.qsl.net/w5dxp/test316y.EZ

A graph of delay versus frequency would be useful. It should show over
what frequency range the coil acts mostly like a transmission line and
where it acts mostly like something else (i.e. inductor, parallel
resonant tank).


This coil, operated below its self-resonant frequency, has
phase shift of 15.68 degrees or ~0.044 wavelength (delay of
7.4 nS). Dr. Corum says anything over 15 degrees requires
the distributed network model. 15 degrees will transform
50 ohms to 54+j120 ohms, causing SWR to be erroneously
reported as 7:1 instead of 1:1. That sounds like too
large an error to me.

Since the lumped-circuit model assumes a delay of zero, i.e.
faster than light, seems the use of the lumped-circuit model
results in 100% error, or infinite error if one calculates
it the other way. :-)

BTW, one of the principles on the other side of the argument
sent me a file with a worm in it. I guess he wanted to
extend the silence caused by my trip by bringing down my
computer.
--
73, Cecil http://www.qsl.net/w5dxp