RadioBanter - View Single Post

March 8th 06, 12:08 AM posted to rec.radio.amateur.antenna

wrote:
What you are missing is the flux inside the coil links all the turns at
light speed. When it does that, current appears at nearly the same
instant of time (light speed over the spatial distance of the inductor)
in all areas that are linked by flux.

I am not missing the flux linkage. What you are missing is the known
phase lag that the current undergoes compared to the voltage. Whatever
voltage phase shift you measured (60 degrees), the lagging current
phase shift is likely to be more than double that value. Hint: an
ideal inductor forces the current to lag the voltage by 90 degrees.
If the current propagates at the speed of light, the voltage propagates
much faster than the speed of light so it can lead the current. Please
explain that one to us.

The flux coupling also tries to equalize currents throughout every area
of the coil.

A well known fact. It applies to the forward current and reflected
current, not to the standing wave current which is not flowing
into or out of the coil at all. There is no net charge flow in
a standing wave and therefore, no net current flow. At any point
on a 1/2WL thin wire dipole, the only thing happening is that the
energy is migrating between the H-field and the E-field. There is
zero energy flow away from that point in either direction. That's
why the phase angle of the reflected current is constant and fixed
at zero degrees. It is simply not flowing. What is flowing is the
forward and reflected component currents which indeed to obey all
the rules you have listed here.

Charge conservation also dictates that any current flowing into the
coil has to be equalled by a like current flowing out the other
terminal, less any displacement currents caused by stray capacitance
(electric fields) to the outside world.

Absolutely no argument here. Even assuming the coil is lossless, the
magnitude of the forward current flowing into the coil is equal to
the magnitude of the forward current flowing out of the coil. Likewise
for the reflected current. So this part of your argument is somewhat
irrelevant. What you seem to be missing is the phase shift in those
component currents.

We cannot have a two terminal "black box" with confined fields that
behaves any other way, standing waves or not.

If a piece of transmission that is an appreciable percentage of a
wavelength is coiled into a coil that is an appreciable percentage
of a wavelength, why is it surprising to you that the coil responds
somewhat like the piece of wire that it replaces? The answer is that
you assumed the proof in your argument. It goes something like this:

A lumped inductance doesn't have any magnitude change or phase shift
through the coil. A bugcatcher loading coil is a lumped inductance.
Therefore, a bugcatcher loading coil doesn't have any magnitude change
or phase shift through the coil. The first proof that you offered some
months ago was that the lumped inductance modeled in EZNEC didn't show
any magnitude change or phase shift. Do you see the fallacy in your
thought processes? You assumed the proof in your argument and you
are still falling into that logical trap. Is it any surprise that
a software program shows no magnitude change or phase shift? Please
open up your mind and think the unthinkable. You will be rewarded.

The only flaws in having zero current phase shift and zero current
difference are the less-than-perfect flux coupling and
less-than-perfect confinement of the electric field.

There you go, assuming the proof in your argument. A lossless non-
radiating transmission line doesn't even obey those rules. Why should
you expect a real-world coil made from that transmission line wire to
obey those rules? Before you respond with the 2-terminal Vs 4-terminal
argument, please realize that a horizontal #14 wire 30 ft. above ground
is considered to be a single-wire transmission line with a Z0 of around
600 ohms. Thus, a horizontal dipole is simply a lossy transmission line.

If you would like, I can quote Balanis on all of this.

Any deviation from
following perfect two-terminal rules are directly tied to the ratio of
load impedance on the inductor to the stray capacitance to the outside
world, and of course less than perfect flux linkage from end-to-end in
the coil.

Assuming the proof again. 1/4WL apart in a lossless, non-radiating
transmission line, the standing wave currents are wildly different.
Why are you surprised when we take that 1/4WL of wire, wind it into
a coil, and achieve a lot of the same conditions?

If you can stay on topic and we process only one point at a tme, I'm
sure you will be able to learn how this works.

I'm certainly game for that. We can start by agreeing that the forward
current through a loading coil has the same magnitude at each end of
the coil but suffers a phase shift through the coil. You measured a
voltage phase shift of 60 degrees through a 100uH coil at 1 MHz. Since
the current lags the voltage in a coil, the current phase shift has to
have been greater than 60 degrees, maybe even 120+ degrees depending
upon the Q of the coil. Tom, even I can measure the traveling wave
current phase shift in a 75m bugcatcher coil so please don't insult
my intelligence by asserting that a phase shift doesn't exist.

If a coil could eliminate phase shifts, Intel would be using them in
their computer busses. The truth is, a coil in a computer bus
increases the phase shift, not decreases it. So please give us a
break on that irrational concept. You have been fooled by your model.
--
73, Cecil http://www.qsl.net/w5dxp