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Current across the antenna loading coil - from scratch
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April 12th 06, 02:33 PM posted to rec.radio.amateur.antenna
Cecil Moore
Posts: n/a
Current across the antenna loading coil - from scratch
wrote:
The loading coil doesn't "replace" missing electrical degrees, it
primarily corrects power factor by compensating reactance.
If correcting the power factor didn't cause a phase shift, the
power factor wouldn't change but we know it does. That phase
shift is exactly what we are talking about. The coil shifts
the phase of both the forward wave and reflected wave thus
furnishing some much needed electrical degrees in order to
resonate the antenna by bringing the phasor sum of the forward
and reflected voltages into phase with the phasor sum of the
forward and reflected currents.
Any power engineering textbook will tell you what happens to the
phase when the power factor is corrected. Hint: If the phase
stayed the same, as you assert, nothing would change. But we
know that correcting the power factor changes the phase. That's
exactly what correcting the power factor is all about.
The truth is the loading inductor almost never has the same phase shift
in current as the missing antenna area it replaces, and it almost never
has the same "current drop".
The inductor does indeed
contribute a phase shift that is not zero. In a one wavelength
system, the coil can just as easily contribute a current RISE
as a current DROP. That fact alone is reason to drop the flawed
model. Current cannot be created in a coil by sucking it out of
earth ground which is what your theory have us believe. But of
course, you have refused to discuss the subject.
I can have an antenna of given dimensions with a loading coil at one
fixed spot. The difference in current flowing into one end and out the
other can go all over the place, depending only on the coil's physical
design wity the antenna resonant on the same frequency. This happens
ONLY by changing the coil.
Of course, but that is beside the point. Every real world inductor does
contribute its own unique phase shift and its own unique current change,
rise, fall, or equal at current nodes and antinodes. You have absolutely
refused to discuss that current rise. One wonders why.
If I had a coil that was compact and not against the groundplane with
low stray capacitance compared to the antenna area above the coil,
current difference between each terminal or through the coil could be
immeasurable with reasonably good instrumentation. Phase shift in
current could also be nearly zero. None of this would be anywhere near
the area the coil replaces.
Resorting to a specially designed coil completely different from
anything used in the real world has been your specialty. If your
theory only works for only one special case and is not valid for
the general case, it's time to junk that theory.
After failing a dozen times to achieve equal current at both ends
of numerous coils, you finally declared victory using a small
toroidal coil. Uhhhh Tom, one out of twelve doesn't prove much.
I have shown you how to achieve equal current with any coil. It
just depends upon where the coil is placed in the standing wave
environment.
A few people have violated the rules of charge conservation, charge
movement, and misapplied the concept of standing waves, but the single
largest error is standing behind the myth or misconception that that
loading coil somehow acts like the "missing area of antenna".
The coil's function is to bring the forward and reflected waves
into phase so the feedpoint impedance will be purely resistive.
It cannot do that if it has no effect on phase. Your theory
is full of holes.
The coil affects the electrical length of the antenna, not the
physical length. Nobody has ever said it replaces the missing
physical length of the antenna. Your implication is that same
tired old straw man riding that same old dead horse.
Please stop trying to twist what we are saying and fix the
twist in your own misconceptions. For instance, how does your
theory handle a current rise through a coil as illustrated at:
http://www.qsl.net/w5dxp/test316.GIF
in the right hand part of the graphic. Why do you refuse to
discuss this current RISE?
--
73, Cecil
http://www.qsl.net/w5dxp
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