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Old April 3rd 06, 01:48 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Coils and Transmission Lines.

Ian White GM3SEK wrote:
I don't intend to - that quotation is perfectly correct. It means that
in a test-case situation where the lumped model *does* apply, the
distributed model will give EXACTLY the same results.


Ian, you know nothing is "EXACTLY" the same. All you can say is that
the two models give acceptably similar results within a certain range
of accuracy.

To paraphrase Roger Whittaker: "'EXACTLY' is for Children Spinning
Daydreams".

This is the test case that I'm trying to make you apply, to check that
with a lumped-inductance load, your antenna theory predicts the correct
behaviour, namely no phase shift in the current through a lumped
inductance.


:-) That's like proving there's no loss in a lossless transmission
line, Ian. Please send me a 100 uH lumped inductance and I will
run some tests on it and report back to you. What do you want to
bet the lumped circuit model will be wrong?

Some people have a problem with their model trying to dictate reality.
You seem to have fallen into that trap. Allow me to raise my voice.

THERE IS NO SUCH THING IN REALITY AS A LUMPED INDUCTANCE!!!!

The lumped circuit model is an approximation to reality. It has
been patched numerous times as situations came up that it could
not handle. Sometimes it works and sometimes it doesn't work.
Since the distributed network model is a superset of the lumped
circuit model, if there is ever any disagreement between the two
models, the distributed network model wins every time.

The test is not whether the distributed network model yields the
same results as the lumped circuit model. The test is whether
the lumped circuit model yields the same results as the
distributed network mode. That's what the argument is all about.
The distributed network model is the GOLD standard. The lumped
circuit model is just a pale approximation to reality.

There's no problem with the distributed circuit model. There's no
problem with the lumped circuit model as a subset of that. All the
problems are with your incorrect application of those models.


That may be true, but we will never know until you (and others)
recognize the difference between standing wave current and
traveling wave current as explained in my other posting. But
in case you missed it, here is a one wavelength dipole fed 1/4
WL from the right end. ///// is a 90 degree loading coil.

------A------B-/////-D-------------fp-------------

The current at B is measured by an RF ammeter at one amp. The
current at D is measured by a similar RF ammeter at zero amps.
I can provide an EZNEC model if you like. How does your lumped
circuit model explain those measured results?
--
73, Cecil http://www.qsl.net/w5dxp