Tom Donaly wrote:

Cecil Moore wrote:
Yet many keep insisting that the net currents at each end of a
loading coil are the same magnitude.

No, "many" don't keep insisting anything of the sort. Those
interested should go to Tom Rauch's web site, read everything
he wrote on the subject, and come to their own conclusions as
to what "many" think.

That's exactly what I am talking about. W8JI completely ignores
the increase in current through a loading coil. How does he explain
the current inside the coil being of a greater magnitude than anywhere
else in the system, including at the feedpoint? (Hint: he doesn't as
he apparently believes that would be a violation of Kirchhoff's laws!)
But it happens all the time in distributed network configurations.

Here's a quote from http://www.w8ji.com

"How much difference is there in loading coil current ENTERING the coil
and loading coil current EXITING the far end? If the antenna beyond the
coil has a low self-impedance compared to the impedance of the shunting
capacitance from the coil to "ground", the currents at each end of the
coil will be essentially equal."

We can imply that w8ji believes that STANDING WAVE currents flow,
"ENTERING" the bottom of the coil and "EXITING" the top. With a
false premise like that, he cannot possibly get anything right from
that point on.

However, if we accept Kraus' approximation in the following quote from
"Antennas For All Applications", ZERO net current will be flowing
through that coil.

Speaking of thin linear standing wave antennas:
"Current-distribution MEASURMENTS indicate that this is a good
assumption provided that the antenna is thin, i.e., when the conductor
diameter is less than, say, 0.01WL. Thus, the sinusoidal current
distribution approximates the natural (current) distribution on thin
antennas." ... "A sinusoidal current distribution may be regarded as
the STANDING WAVE produced by two uniform (unattenuated) traveling waves
of equal amplitude moving in opposite directions along the antenna."

The diameter of #16 wire on 10m is about 0.0001WL, beating Kraus' above
approximation requirement by a couple of magnitudes. (The actual difference
in the forward current and reflected current through the coil appears to
be in the neighborhood of about 5% for a loaded mobile antenna.)
--
73, Cecil http://www.qsl.net/w5dxp


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