RadioBanter - View Single Post

March 21st 06, 03:47 PM posted to rec.radio.amateur.antenna

wrote:

Cecil Moore wrote:
If you are technically correct, why are you so technically
silent on the subject?

I'm not silent.

You are silent on the subject of how the lumped-circuit model
explains more current at the top of the coil than exists at
the bottom of the coil. Please share that knowledge with us.

I think I've done a good job of explaining things, and I've made
measurements and posted results.

Have you made measurements with 1/4WL added to the top of
a mobile antenna? Will you believe your measurements when
you measure more current "flowing" into the bottom of the
coil than out of the top of the coil?

At least a dozen of my technical questions have gone
unanswered by being ignored. Lot's of readers have
noticed and commented in emails to me.

So what?

:-)

1.) I told you weeks ago I'm too busy working right now to get deeply
involved in this.

:-)

2.) When measurements are made, you dismiss them as "measuring current
in a system with standing waves".

It has been proven beyond a reasonable doubt that standing wave
current, func(kx)*func(wt) is not like traveling wave current,
func(kx +/- wt). Since standing wave current phase is devoid of
phase information, its phase cannot be used to determine the phase
shift through a coil. Standing wave current phase is what W7EL
measured. He drew conclusions about phase from measuring the
phase of a signal devoid of any phase information. I pointed
that technical fact out to him at the time and he ignored me.
I also pointed out that the phase information was actually
embedded in the amplitude measurement as a variation of a
cosine function. He rejected that assertion with a personal
remark.

If you will repeat your measurements with 1/4WL added
to the top of the base-loaded mobile antenna, you will
start to understand the physics involved. The current
taper through a coil depends upon where in the standing
wave environment that the coil is installed.

Then why can I measure a fixed inductor location in a dfixed antenna,
and range from no taper at all in current to just under 1/3 reduction
in current? Does you standing wave model explain this very repeatable
measurement?

Of course! If you measure the current taper at a point where the
standing wave current slope is near zero, you will measure near
zero taper. If you measure the current taper at a point where
the standing wave current slope is near maximum, you will measure
lots of taper. If you measure at just the right point, you will
measure current flowing into both ends of the coil at the same
time. That's another thing I have asked you to explain with no
response.

The lumped-circuit analysis fails for the typical
75m amateur radio mobile antenna.

I disagree. Unless we want to say so does the standing wave model.

The "standing wave model" is a component of the distributed-network
model which is known to work in the presence of standing waves. The
lumped-circuit model is known to fail in the presence of standing
waves. Quoting Dr. Corum: "There are no standing waves on a lumped
element circuit component. (In fact, lumped-element circuit theory
inherently employs the cosmological presupposition that the speed
of light is infinite, as every EE sophmore should know. See, e.g., -
"Electric Circuits", by J.W.Nilsson, Addison-Wesley, 1983, p. 3."

Dr. Corum's first sentence above means: *There are no standing waves
*allowed* in a lumped element circuit model.*

The antenna can be modelled as a series of lumped inductors with
capacitance to the outside world just as well as any other method.

But that is not what you and W7EL have done. You have modelled it
as a single coil with distributed capacitance. That approach is
known to fail when the coil is longer than 15 degrees and installed
in a standing wave environment.

If you use enough lumped inductors and capacitors, you have the
distributed network model but with a lot more math to do.
--
73, Cecil http://www.qsl.net/w5dxp