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Old March 25th 06, 10:01 AM posted to rec.radio.amateur.antenna
 
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Default Current through coils


K7ITM wrote:
cascaded. Each was 1uH series, followed by 100pF shunt to ground. I
put a 100 ohm load on one end and fed the other end with a 2.5MHz sine
wave with 100 ohms source resistance. Sqrt(LC) is 10 nanoseconds per
section, so I expect 100 nanoseconds total delay, or 90 degrees at
2.5MHz. That's what I saw. Then I added unity coupling among all the
coils, and to keep the same net inductance, I decreased each inductor
to 100nH. The result was STILL very close to a 90 degree phase shift,
with a small loss in amplitude. In each case, the current in each
successive inductor shifts phase by about 1/10 the total. Although the
simulation is less than a perfect match to a completely distributed
system with perfect flux linkage (and just how you do that I'm not
quite sure anyway...), but it's close enough to convince me that
perfect flux linkage would not prevent behaviour like a transmission
line, given the requisite distributed capacitance.


Thanks Tom,

That's very interesting. My thought is the difference in
phase-of-current at each of the inductor would be affected by mutual
coupling, with perfect coupling preventing phase differences in
current, but maybe that is shortsighted.

I'll have to think about that a while and how it might affect what I am
saying.

73 Tom