Richard Harrison wrote:
Ian, G3SEK wrote:
"Hopefully you will agree that an IDEAL INDUCTANCE does not ever have
different currents at its two terminals and does not radiate either."

Sorry to disappoint you, but adequate demonstration has already shown
different currents in and out of a loading coil. I won`t claim it was
an ideal inductor.

In that case you have nothing to discuss with me.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Tom Donaly, KA6RUH wrote:
": how do you take the gradient of the current at a point on a
transmission line?"

Not sure I understand the question. Gradient is the rate of change and
that`s the derivative of the current at a given point. Over a certain
path it is the difference between the path ends and can be averaged for
the path.

For convenience, Kraus has collected transmission line formulas. I`m not
a typist so I`ll just say they are near the end of the new edition, page
890. In the 1950 edition they can be fornd on pages 506 and 507, also
near the end of the book.

Work out your own example.

Best regards, Richard Harrison, KB5WZI

Ian
Would you please describe for me the physical arrangement of an IDEAL
inductance.
I cannot visulise such a thing as I only have seen 'coiled ' inductors
,where each coil has
a scientific and analytical relationship to its adjacent coils which thus
CREATE an
inductance and without which an 'inductance' cannot occur.
I don't want to enter the augument that is ensuing on this thread but just
want to be sure that
there is not an inductance available that is not generated by proximity to
other items including
its own content (wire length)
Using chemical terms, is it an element or a compound if you get my drift ,
since you later
mention that 'inductance.' has a "fundamental physical
property................." that does not change
regardles of a proximity situation.
i.e. Self sufficient.?
TIA
Art


"Ian White, G3SEK" wrote in message
news
Cecil Moore wrote:
I want you to stop and think a moment, about how an IDEAL INDUCTANCE
behaves in an antenna. (Sorry to shout, but every time I type "ideal
inductance" quietly, you seem to read something else :-)

Ian, please take your own advice. It's pretty obvious that you are
thinking about an IDEAL INDUCTANCE in terms of a lumped circuit
analysis
which is invalid when analyzing a STANDING-WAVE ANTENNA.

It makes life easier to compartmentalize your scientific world-view in
that way.... but it is deeply, fundamentally wrong.

In reality, all true scientific knowledge joins up seamlessly - that's
how we *know* it's true! If we can't see how it joins up, that means we
still have work to do. Dividing it into compartments that don't join up
is lazy and will always lead you false.

A fundamental physical property like inductance doesn't change its
behaviour depending on the situation it finds itself in. If you cut the
antenna wire and insert an ideal, lumped inductance, that inductance
will behave in exactly the same way as it does in any other circuit.

If you really looked hard at the math of antennas considered as
transmission lines, you would find there is no problem whatever about
inserting an ideal inductance, with no difference in current between its
two terminals.



--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Tom Donaly wrote:

Cecil Moore wrote:
Heh, heh, so you don't believe there is a current drop between the
current maximum point and current minimum point on a transmission
line with reflections? Seems to me going from 2 amps at a current
maximum to 0.1 amps at a current minimum is a measurable drop in
total current.

Next, Cecil, you're going to be talking about a "current gradient"
and a "scalar current field." Here's a question for you, Cecil, and
Richard Harrison, and Yuri, too: how do you take the gradient of
the current at a point on a transmission line, and, if were possible
to do so, what is the physical significance of the result?

A total current gradient obviously exists on a transmission line
with current minimums and maximums. You can locate those points
with a simple pickup loop. The current gradient is caused
by the superposition of forward and reflected current waves as
described in any transmission line textbook.

"Taking the gradient" seems to me to be unnecessary and just a
logical diversion away from the qualitative conceptual discussion.
--
73, Cecil http://www.qsl.net/w5dxp


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Ian White, G3SEK wrote:

Cecil Moore wrote:
Ian, please take your own advice. It's pretty obvious that you are
thinking about an IDEAL INDUCTANCE in terms of a lumped circuit analysis
which is invalid when analyzing a STANDING-WAVE ANTENNA.

It makes life easier to compartmentalize your scientific world-view in
that way.... but it is deeply, fundamentally wrong.

Would you mind providing some real-world proof of your argument or
are you satisfied just to play games in your mind?

In reality, all true scientific knowledge joins up seamlessly - that's
how we *know* it's true! If we can't see how it joins up, that means we
still have work to do. Dividing it into compartments that don't join up
is lazy and will always lead you false.

Most of our models involve shortcuts. For instance, the shortcut equations
for small loops do NOT work for large loops. Your lumped circuit shortcuts
don't work for distributed networks. When anything in the circuit is an
appreciable percentage of a wavelength, the lumped circuit model doesn't
work. That's why the distributed network model was invented.

A fundamental physical property like inductance doesn't change its
behaviour depending on the situation it finds itself in. If you cut the
antenna wire and insert an ideal, lumped inductance, that inductance
will behave in exactly the same way as it does in any other circuit.

It won't behave at all in reality because an ideal, lumped inductance exists
only in the human mind, not in reality. If you want to play mind games, be
my guest, but please don't try to pass your mental musings off as reality.

The question is not whether your mental current changes through an ideal,
lumped inductance existing only in your mind. The question is whether the
current changes through a real-world bugcatcher coil that exists in reality.

If you really looked hard at the math of antennas considered as
transmission lines, you would find there is no problem whatever about
inserting an ideal inductance, with no difference in current between its
two terminals.

An ideal inductance doesn't exist in reality so you are just playing
games in your mind. Every real-world coil has a phase shift, i.e. a
delay. A phase shift is all that is required for the superposed
currents at each end of the coil to be different from each other.

You seem to be saying that the phases of the forward and reflected
currents don't change through a one-foot diameter, one-foot long bugcatcher
coil made from 60 feet of wire? All I can say is, "Get real!"
--
73, Cecil http://www.qsl.net/w5dxp


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wrote:

Would you please describe for me the physical arrangement of an IDEAL
inductance.

Art, picture a dimensionless point in your mind. Define that point as
an inductance without dimensions, without capacitance, and without resistance.
There is your "IDEAL inductance" and exists ONLY in the human mind and certain
computer models. Since it is dimensionless, the current into the point and the
current out of the point are the same current because they are the same point
and, of course, the dimensionless point is traversed instantaneously.

Now, without modification, extend that dimensionless concept to a one-foot
diameter, one-foot long bugcatcher coil, wound with 60 feet of real-world wire.
Assert that the bugcatcher coil has virtually identical characteristics to that
previous dimensionless point in your mind. Use a computer model's dimensionless
inductor feature to prove your point.

That's the present "physical arrangement". :-)
--
73, Cecil http://www.qsl.net/w5dxp


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Richard Harrison wrote:
Jimmie wrote:
"Coiling the wire has nothing to do with how it does or does not
radiate,---."

Good. Just leave your antenna rolled up.

Best regards, Richard Harrison, KB5WZI


That's exactly what's done in some "frequency independant"
antennas. You can do it with logarithmic spirals or the
Archimedean kind, take your pick.
73,
Tom Donaly, KA6RUH

Richard Harrison wrote:

Tom Donaly, KA6RUH wrote:
": how do you take the gradient of the current at a point on a
transmission line?"

Not sure I understand the question. Gradient is the rate of change and
that`s the derivative of the current at a given point. Over a certain
path it is the difference between the path ends and can be averaged for
the path.

For convenience, Kraus has collected transmission line formulas. I`m not
a typist so I`ll just say they are near the end of the new edition, page
890. In the 1950 edition they can be fornd on pages 506 and 507, also
near the end of the book.

Work out your own example.

Best regards, Richard Harrison, KB5WZI


Thank you, Richard, you just made my point.
73,
Tom Donaly, KA6RUH

wrote:

Ian
Would you please describe for me the physical arrangement of an IDEAL
inductance.
I cannot visulise such a thing as I only have seen 'coiled ' inductors
,where each coil has
a scientific and analytical relationship to its adjacent coils which thus
CREATE an
inductance and without which an 'inductance' cannot occur.
I don't want to enter the augument that is ensuing on this thread but just
want to be sure that
there is not an inductance available that is not generated by proximity to
other items including
its own content (wire length)
Using chemical terms, is it an element or a compound if you get my drift ,
since you later
mention that 'inductance.' has a "fundamental physical
property................." that does not change
regardles of a proximity situation.
i.e. Self sufficient.?
TIA
Art


"Ian White, G3SEK" wrote in message
news
Cecil Moore wrote:

I want you to stop and think a moment, about how an IDEAL INDUCTANCE
behaves in an antenna. (Sorry to shout, but every time I type "ideal
inductance" quietly, you seem to read something else :-)

Ian, please take your own advice. It's pretty obvious that you are
thinking about an IDEAL INDUCTANCE in terms of a lumped circuit
analysis
which is invalid when analyzing a STANDING-WAVE ANTENNA.

It makes life easier to compartmentalize your scientific world-view in
that way.... but it is deeply, fundamentally wrong.

In reality, all true scientific knowledge joins up seamlessly - that's
how we *know* it's true! If we can't see how it joins up, that means we
still have work to do. Dividing it into compartments that don't join up
is lazy and will always lead you false.

A fundamental physical property like inductance doesn't change its
behaviour depending on the situation it finds itself in. If you cut the
antenna wire and insert an ideal, lumped inductance, that inductance
will behave in exactly the same way as it does in any other circuit.

If you really looked hard at the math of antennas considered as
transmission lines, you would find there is no problem whatever about
inserting an ideal inductance, with no difference in current between its
two terminals.



--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek



Can you visualize a point mass, Art? An ideal inductance isn't a point
mass, but according to the textbooks, one is the mathematical analogue
of the other.
73,
Tom Donaly, KA6RUH

Cecil Moore wrote:

Tom Donaly wrote:

Cecil Moore wrote:

Heh, heh, so you don't believe there is a current drop between the
current maximum point and current minimum point on a transmission
line with reflections? Seems to me going from 2 amps at a current
maximum to 0.1 amps at a current minimum is a measurable drop in
total current.


Next, Cecil, you're going to be talking about a "current gradient"
and a "scalar current field." Here's a question for you, Cecil, and
Richard Harrison, and Yuri, too: how do you take the gradient of
the current at a point on a transmission line, and, if were possible
to do so, what is the physical significance of the result?


A total current gradient obviously exists on a transmission line
with current minimums and maximums. You can locate those points
with a simple pickup loop. The current gradient is caused
by the superposition of forward and reflected current waves as
described in any transmission line textbook.

"Taking the gradient" seems to me to be unnecessary and just a
logical diversion away from the qualitative conceptual discussion.
--
73, Cecil http://www.qsl.net/w5dxp


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You and Richard need a refresher course in electromagnetics. I hope
Yuri doesn't fall into the same trap.
73,
Tom Donaly, KA6RUH