The absolute accuracy of the measurement isn't important. All that
matters is the accuracy of the ratio of currents at input and output,
which is a lot easier to get with reasonable accuracy.

What I'm looking for now, however, is your recommendation for a test
which will clearly show the current ratio you claim will happen, of such
a magnitude that the result will be clear even in the presence of a few
percent error.

Based on my measurements of currents with both probes on the same lead,
and averaging results with probes reversed, I think I can measure the
ratio within about 2% at ratios near 1, and resolve phase shifts of a
few degrees. If you can come up with a test that'll produce 30%
amplitude change and 45 degrees phase shift, I guarantee I tell whether
the result is closer to that or to the zero amplitude change and zero
phase shift I predict.

Roy Lewallen, W7EL

Cecil Moore wrote:
Yuri Blanarovich wrote:

If the feedpoint current was at 0 deg of the radiator length, and coil
replaces
18 deg of wire, the cos 18 deg = 0.951 which should make difference,
drop in
the coil current 5% (or half, 2.5 deg?) Providing current maximum is
exactly at the bottom end of the coil.


It wasn't. The coil made the antenna too long so the current maximum
was inside the coil. But this points up a measurement problem. I
doubt that these measurements are 5% accurate.