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Old April 8th 06, 04:47 PM posted to rec.radio.amateur.antenna
John Popelish
 
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Default Current across the antenna loading coil - from scratch

Cecil Moore wrote:
Gene Fuller wrote:

I am feeling dizzy. I am quite comfortable with my understanding of
the entire problem, but I am seriously confused about your position.
Nobody has ever talked about efficiency or the length of wire needed.
The issue has always been replacing "degrees of antenna". I have
captured a few excerpts from April 7.



What you quoted from me is my reporting of what EZNEC says about
standing wave current Vs traveling wave current at:

http://www.qsl.net/w5dxp/travstnd.GIG

The 'x' axis for both conditions is just a piece of 1/4WL wire.
One can calculate the phase shift in any section of wire in two
ways:

1. For traveling waves, the phase shift is given by the graph
of the phase (red line). The magnitude (blue line) contains
no phase information.

2. For standing waves, the phase shift is given by taking the
arc-cosine of the magnitude (blue line). The phase (red line)
contains no phase information.


Agreed, with one exception.

There is a phase reversal each time you pass through a node, so you
can tell by phase measurement, if you are on the far end of an odd
numbered node or an even numbered node, once you decide which of the
two possibilities of the phase is at the far end of node zero (or some
other reference point). But between any pair of nodes, yes, you have
to use the phase information obtained from the ARC-COS(magnitude), or
the distance from that point to a node (as a fraction of a wavelength
in the line), to infer where you are within that half wavelength.

Of course, you can find the node either as a point with zero
magnitude, or the point between phase reversals.