Keith Dysart wrote:
Perhaps there is just no reason why the "phase shifts" should add
to 90. That would make the problem go away.

But there is every reason why the phase shifts *must*
add up to 90 degrees (or 270 or 450 or ...).

The only way you can get zero ohms looking into an
open stub is if the phase shift end-to-end is 90
degrees (or 270 or 450 or ...). The reflected current
must arrive back at the feedpoint in phase with
the forward current for the stub to be 1/4WL resonant.

In a typical loaded mobile antenna, the only way
to get a resistive feedpoint impedance is if the
antenna is electrically 90 degrees long.

Take a 1/4WL straight monopole wire. It is
electrically 90 degrees long. Put one turn of
loading in it. Is it still electrically 90 degrees
long or not? Proceed until the antenna is all
coil, i.e. self-resonant. Is it still electrically
90 degrees long or not?
--
73, Cecil http://www.w5dxp.com

On Dec 6, 8:59 am, Cecil Moore wrote:
Keith Dysart wrote:
Perhaps there is just no reason why the "phase shifts" should add
to 90. That would make the problem go away.

But there is every reason why the phase shifts *must*
add up to 90 degrees (or 270 or 450 or ...).

The only way you can get zero ohms looking into an
open stub is if the phase shift end-to-end is 90
degrees (or 270 or 450 or ...). The reflected current
must arrive back at the feedpoint in phase with
the forward current for the stub to be 1/4WL resonant.

In a typical loaded mobile antenna, the only way
to get a resistive feedpoint impedance is if the
antenna is electrically 90 degrees long.

Take a 1/4WL straight monopole wire. It is
electrically 90 degrees long. Put one turn of
loading in it. Is it still electrically 90 degrees
long or not? Proceed until the antenna is all
coil, i.e. self-resonant. Is it still electrically
90 degrees long or not?

You are good at building scenarios that align with
your hypotheseses. To test your hypothesis for
correctness you need to examine the scenarios
that may not align rather than those that do.

And you already have one. You have needed to
invent a phase shift occuring at an impedance
discontinuity to explain the missing "electrical
length".

You should also consider a shortened monopole
where lumped elements are used to tune out
the reactance.

Also consider a lengthened monople where
either distributed or lumped elements are used
to tune it.

You should consider a pure lumped element
circuit that presents the same impedance.
Identify the locations that sum to a 90 degree
"electrical length".

Lastly, for real fun, find the 90 degree
"electrical length" in a crystal.

....Keith

Keith Dysart wrote:
You should also consider a shortened monopole
where lumped elements are used to tune out
the reactance.

Please feel free to pursue that line of
development if you are so inclined.

Since lumped elements do not exist in reality,
they are outside of the scope of real-world
75m mobile loading coils that I am trying to
cover here. I am not proposing a theory of
everything nor do I intend to waste my time
with such. But be my guest.

The ARRL Antenna Book equations for a small loop
are "wrong" for a large loop. Moral: Recognize
the limitations of the model being used.

Lastly, for real fun, find the 90 degree
"electrical length" in a crystal.

Even Einstein's theory of relativity has its
limitations. It is a diversion to try to
require every model to cover every real and
imagined possibility.
--
73, Cecil http://www.w5dxp.com

On Dec 6, 1:23 pm, Cecil Moore wrote:
Keith Dysart wrote:
You should also consider a shortened monopole
where lumped elements are used to tune out
the reactance.

Please feel free to pursue that line of
development if you are so inclined.

Since lumped elements do not exist in reality,
they are outside of the scope of real-world
75m mobile loading coils that I am trying to
cover here. I am not proposing a theory of
everything nor do I intend to waste my time
with such. But be my guest.

You have done this before; postulating
explanations that only work in the complexity
of the "real" world, but fail when presented with
the simplicity of ideal test cases.
Then, when the explanations fail on the simple
cases, claiming these cases are not of interest
because the real world is more complex.

It won't fly. Good explanations also work when
presented with test cases from the simpler
world of ideal components.

....Keith

Keith Dysart wrote:
You have done this before; postulating
explanations that only work in the complexity
of the "real" world, but fail when presented with
the simplicity of ideal test cases.

For Pete's sake, Keith, Ohm's law doesn't even
work when R=0.

Then, when the explanations fail on the simple
cases, claiming these cases are not of interest
because the real world is more complex.

I define the boundary conditions within which my
ideas work. Whether they work outside those defined
conditions is irrelevant. I believe they do work
for ideal conditions, but I don't have the need
to prove a "theory of everything".

Every model that we use has flaws. Asking me to
come up with a flawless "theory of everything"
model is an obvious, ridiculous diversion but
you already know that.
--
73, Cecil http://www.w5dxp.com

On Dec 7, 12:46 pm, Cecil Moore wrote:
Keith Dysart wrote:
You have done this before; postulating
explanations that only work in the complexity
of the "real" world, but fail when presented with
the simplicity of ideal test cases.

For Pete's sake, Keith, Ohm's law doesn't even
work when R=0.

A rather large red herring. Ideal components are
the topic, and we mostly use ideal wire with R=0
without difficulty.

Then, when the explanations fail on the simple
cases, claiming these cases are not of interest
because the real world is more complex.

I define the boundary conditions within which my
ideas work. Whether they work outside those defined
conditions is irrelevant. I believe they do work
for ideal conditions, but I don't have the need
to prove a "theory of everything".

Sounds good, but mostly you do not examine
ideal conditions because they tend to show that
the models fail. With non-ideal conditions, the
discussion is easy to drive far from the target
and prevent resolution of whether the model
works.

....Keith

Keith Dysart wrote:

Sounds good, but mostly you do not examine
ideal conditions because they tend to show that
the models fail. With non-ideal conditions, the
discussion is easy to drive far from the target
and prevent resolution of whether the model
works.

My postulate is that Newton was wrong: moving objects come to a rest
without any external applied force. Every observation made supports
this. There's no need to consider what happens in a frictionless
environment, since such a thing doesn't exist.

Roy Lewallen, W7EL

Keith Dysart wrote:
Sounds good, but mostly you do not examine
ideal conditions because they tend to show that
the models fail.

I believe that is a false statement. Please
prove your assertion.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Keith Dysart wrote:
You have done this before; postulating
explanations that only work in the complexity
of the "real" world, but fail when presented with
the simplicity of ideal test cases.

For Pete's sake, Keith, Ohm's law doesn't even
work when R=0.

Then, when the explanations fail on the simple
cases, claiming these cases are not of interest
because the real world is more complex.

I define the boundary conditions within which my
ideas work. Whether they work outside those defined
conditions is irrelevant. I believe they do work
for ideal conditions, but I don't have the need
to prove a "theory of everything".

Every model that we use has flaws. Asking me to
come up with a flawless "theory of everything"
model is an obvious, ridiculous diversion but
you already know that.

This isn't a diversion: it's the core of the whole dispute.

These days, mathematical models are the normal, everyday way that
engineers go about their business. A bedrock principle is that if a
model is going to be usable and trustworthy, it MUST join up correctly
with existing knowledge. Your model can be as elaborate as you like, but
it always has to prove itself against the simple cases that we already
know about.

Anyone with experience knows that these "simple" reality tests are the
most often the hardest for an elaborate model to pass... but that
doesn't excuse them from the test. If a model cannot handle the simple
situations that we do understand, we can never trust it in more complex
situations.

Ohm's law is a perfect example of a model that works. The whole point is
that Ohms' law IS a good model of reality for a very wide range of
situations, including the simple but extreme case where R equals
exactly zero. It's absurd to suggest that there's a glitch - it simply
means that V would be exactly zero too.

Likewise there are no glitches in the standard circuit models for
inductance and capacitance. They work just fine, for all cases where the
dimensions of the circuit are very small with respect to the wavelength,
so that distributed effects and radiation are negligible. Where those
assumptions are no longer accurate, we can extend the simple model to
include some corrections. But the most important point is, we always
know that we're building up from a solid foundation.

That is also the sensible way to think about loaded antennas. Calculate
it the simple way first, assuming lumped inductive loading, and then
apply corrections as necessary. As I've said before, this simple, solid
method is the one that works. It can take you straight to a workable
prototype, which can be quickly adjusted to frequency. Countless authors
have demonstrated how to do this, and anyone can download G4FGQ's
MIDLOAD program to do the same.

While other people choose to build on those solid foundations, Cecil
insists that simple routine reality tests are a "diversion". He prefers
to keep his floating castles well clear of such hard rocks.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian White GM3SEK wrote:
That is also the sensible way to think about loaded antennas. Calculate
it the simple way first, assuming lumped inductive loading, and then
apply corrections as necessary. As I've said before, this simple, solid
method is the one that works. It can take you straight to a workable
prototype, which can be quickly adjusted to frequency. Countless authors
have demonstrated how to do this, and anyone can download G4FGQ's
MIDLOAD program to do the same.

The point is that IT OBVIOUSLY DOESN'T WORK, Ian, for
the delay through a loading coil. If it worked, W8JI
would not have gotten a 3 ns delay through a 2" dia,
100 TPI, 10" long loading coil. If his test setup
looked like mine, he would have measured a valid
delay around 25 ns.

http://www.w5dxp.com/coiltest.gif

Ian, are you afraid to run that test for yourself?

Cecil
insists that simple routine reality tests are a "diversion".

Please don't twist my words. I insist that simple routine
*UNreality* tests are a diversion. But, my personal opinion
doesn't change anything. The model that I am using works. The
model that W8JI is using doesn't work.

Please take a look at: http://www.w5dxp.com/coil512.ez
and tell me why EZNEC disagrees with W8JI's model.
--
73, Cecil http://www.w5dxp.com