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Old March 16th 06, 09:54 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
Posts: n/a
Default Current through coils

Roy Lewallen wrote:
For that case, it's been theoretically and demonstratively shown to be
equal at both ends.


Only one of the reported measurements showed the magnitudes of
the currents to be equal and that was a small toroidal coil
quite unlike a 75m bugcatcher coil. Wes's web page shows the
currents to be unequal at the ends of the coil. Figure 3 shows
1.03 amps at the bottom of the coil and 0.66 amps at the top
of the coil. That's not equal.

http://www.k6mhe.com/n7ws/Loaded%20antennas.htm

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Here's an example from EZNEC where the currents are not
only unequal, but if one considers to standing wave current
to be flowing, more current is flowing into the bottom of
the coil than out the top. What does the lumped-circuit model
have to say about that? This technical question goes unanswered.

http://www.qsl.net/w5dxp/qrzgif35.gif

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As for phase shift using standing wave current, consider the
following half of a dipole:

FP----------x----------y----------

'x' is at the 30 degree point and 'y' is at the 60 degree
point. What is the standing wave phase shift between point
'x' and point 'y'? We can see from Figure 14-4 in Kraus'
"Antennas for All Applications", 3rd edition, that the
measured phase shift would be zero between 'x' and 'y'.
So why is it a surprise that if the wire between 'x' and
'y' is replaced by a coil, the phase shift remains zero?
The measured phase shift in the wire and the coil are the
same. This technical question goes unanswered.
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73, Cecil http://www.qsl.net/w5dxp