Roy Lewallen wrote:
The impedance of the antenna doesn't change with the feed method ...

One feed method is center feed. Another feed method is off-center feed.
The feedpoint impedance of the antenna changes with position since
for 1/2WL, for instance, the net voltage is a sine wave referenced
to the center, and the net current is a cosine wave referenced to the
center. The feedpoint impedance is approximately sin(x)/cos(x)=tan(x)
where 'x' is the number of degrees away from center.
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73, Cecil http://www.qsl.net/w5dxp