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Re: JD Jackson on the coax, waveguide, and
transmission line
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Alex Yakovlev <Alex.Yakovlev@newcastle.ac.uk>
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22 Jul 2020,
15:00
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to A, Forrest, HARRY, me, Brian, Malcolm, Steve, Anthony, John, Jack
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Thanks, Forrest and Harry (actually
thanks to Harry's email I managed to see Forrest's reply as it got into my
spam box initially - sorry!).
Interesting excerpts from past.
LINEAR was pronounced as the cause of
co-existence of two pulses in the same place in space and time.
It would be worth thinking whether
Linearity is physically universal of course ...
Alex
From: HARRY
RICKER <kc3mx@yahoo.com>
Sent: Wednesday, July 22, 2020 2:47 PM
To: Alex Yakovlev <Alex.Yakovlev@newcastle.ac.uk>; Prof. A
Howie <ah30@cam.ac.uk>; Forrest Bishop <forrestb@ix.netcom.com>
Cc: Ivor Catt <ivorcatt@gmail.com>;
Brian Josephson <bdj10@icloud.com>; Malcolm Davidson <malcolmd3111@hotmail.com>; Steve Crothers
<sjc7541@gmail.com>; Anthony Davies <tonydavies@ieee.org>;
John Raymond Dore <johnrdore@gmail.com>; Jack Dinsdale <jack.dinsdale@tinyworld.co.uk>
Subject: Re: JD Jackson on the coax, waveguide, and transmission
line
Forrest,
Thanks for
sending this "Blast from the past". As I recall, my interaction
with that group was designed to help me to understand antennas, but resulted
in dealing with intolerant people with rigid opinions and hard heads. A lot
of the discussion was fruitless because people were more concerned with
semantics and being a stickler regarding definitions of concepts. Therefore a capacitor can not be
a transmission line, because of definitions. By the way that kind of fits the
discussions we are currently having. Doesn't it?
Harry
On Wednesday,
July 22, 2020, 12:24:22 AM EDT,
Forrest Bishop <forrestb@ix.netcom.com> wrote:
Alex,
The Two Pulses
Problem(s) is extremely important.
The caption for Fig
3. is referring to Prof. Kirk T. McDonald's (Princeton, Physics) claims,
reproduced in part below. FB asks "Fig. 3. When two pulses
overlap, do their fields come to a standstill while two electric currents
obliviously pass though each other? "
FB finds the idea
of standstill fields and electric current passing through each other absurd-
I'm asking it in a rhetorical fashion. Kirk T. is the one that makes these
claims, see below for his "Special Moment" explanation.
Some background-
Kirk is (was?) a sort of star guru at the AntenneX
forum, which in turn is (was?) one of the oldest forums on the internet. I
was invited to join by the owner, then later Harry Ricker and David Tome
appeared. Kirk went off the rails. His behavior
became so obnoxious that they had to create a new sub-forum for him as a sort
of quarantine zone, but not until after some 30 or more of their old-time
subscribers had left. Afaik, the forum has never
been the same since. The exchange below was near the end, while people were
unsubscribing amidst a flurry of private emails.
=================================================================================
From: kirkmcd@princeton.edu
To: antenna-discussion@antennex.com
Date: Sat, 10 Mar 2012 12:31:56 -0500
Subject: Re: [Antenna-discussion] Transmission line pulses
Dave,
All I know about you is what I learn from you emails to this forum, every
one of which spreads misinformation.
1. "within the context of mainstream theory on electric current, how do
two pulses in a transmission line pass right through each other as if they
are waves?".
OK
I1 = exp(z - vt) This
Gaussian pulse moves in the +z direction with speedv
I2 = exp(z + vt) This Gaussian pulse moves in the
-z direction with speedv
Itotal = I1 + I2
Done! The two pulse can coexist because
electromagnetic phenomena are LINEAR.
Each pulse is unaffected by the other.
2. "When I said that a transmission line is basically the same in
principle as a capacitor, you retorted with the single word 'nonsense'. In
actual fact, the only difference between a capacitor and a transmission line
is that a capacitor concentrates a particular effect which is actually
present in all open ended circuits, and in any
circuit when we first switch the power on. "
Again I say "nonsense".
A "capacitor" stores charge/energy, but does not transmit these
from place to place.
A transmission line transmits energy from place to place.
Electromagnetic energy can be characterized as partly electric and partly
magnetic.
In a transmission line there is in interplay between the electric and
magnetic energies.
A capacitor has only electric energy
An inductor has only magnetic energy.
And LC circuit has both electric and magnetic energy, and permits the
interchange of these two types of energy.
If you like thinking of transmission lines in terms of circuit elements, you
can think of a transmission line as a sequence of LC circuits, with both
capacitors and inductors.
http://www.ece.uci.edu/docs/hspice/hspice_2001_2-269.html
It is ridiculous to say that a circuit that involves both capacitors and
inductors is "basically the same in principle as a capacitor".
3. "When I said that there is no adequate explanation in
the literature for what happens when we first switch an electric circuit on,
you replied with the single word 'nonsense'. But we didn't hear your
explanation for what happens."-DT
You give no example of an "inadequate explanation".
Millions of circuits with transient behavior have
been well understood and
analyzed in the literature.
So, I infer that you can't follow any technical literature -- in which
case
one hardly knows how to begins "setting you straight".
4. "None of you have been able to explain how two lots of electrons
moving
in opposite directions along the same a wire, can pass right through each
other as like a wave."-DT
This is a reprise of item 1, but with a more microscopic view.
It sounds as if you are unfamiliar with the so-called Drude Model of electrical conduction, which dates from
1902
http://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/drude_model/drude_model.html
Here is a YOuTube video about this:
http://www.youtube.com/watch?v=dyX5I_io7bg
Electrons don't "pass right through each other". Rather, they
bounce around and pass by one another -- in that a wire is a
3-dimensional entity, not a 1-dimensional structure as you seem to imply.
5. "We can even see this by looking at an AC circuit. Based on
mainstream's belief that we are dealing with a compression and rarefaction in
the two limbs,"-DT
I have no idea what you are talking about here.
???? "Compression" and "rarefaction" in the
"limbs" of a circuit.
"Circuit" means loop, not limbs/arms ????
"Compression" and "rarefaction" of what???????
It sounds like you have a mechanical vision of a "circuit", and
suppose that this view is "mainstream".
Perhaps you have found a few other people who hold such views, but these
views are not "mainstream", in my view.
6. "Finally, you said on one of your mails that the two transmission
line pulses moving in opposite directions cancel each other completely,
magnetic field and all, at the moment of pass over. If that were true, then
what happens to the energy at this moment in time? Does the energy just
momentarily disappear completely? "
OK, let's go into more detail.
I go back to item 1, in which two pulses were considered with Gaussian
current forms.
I did not specify the "circuit" that supported these pulses, so for
simplicity let's consider a (lossless)coaxial cable (with vacuum between the
inner and outer conductors, which we approximate as perfect conductors). The
currents specified in item 1 flow on the inner conductor. Equal and opposite
currents flow on the inside of the outer conductor.
Then the magnetic field H at radius r between the
inner and outer conductor is given by
B = mu_0 I / 2 pi r.
This field "circulates" around the inner conductor
The electric field is directly radially, and has magnitude related related to that of the magnetic field by
E = c B where c is the speed of light in vacuum)
We must now be careful about signs.
For the pulse with current
I1 = exp(z -ct) [ since the speed of the pulse is c
]
the magnetic field B1 is in the +phi direction
and the electric field E1 is in the =r direction
If we want the second pulse to "cancel" the first pulse at time t =
0, we must take its current to be
I2 = - exp(z+ct)
For the pulse the magnetic field B2 is in the -phi direction,
and the electric field E2 is in the +r direction.
So, at time t = 0, the total current is zero, and the total magnetic field is
zero, but the total electric field is twice that of either pulse by itself
At this special moment, all the field energy is "electric", but
in general it is partly electric and partly magnetic.
When the pulses are far apart, the energy is half electric and half magnetic.
Hence the total energy is 4 times the electric energy of each pulse.
When the two pulses "cancel" at time t = 0, the electric field
is twice that of each pulse, the magnetic field is zero, and the total energy
is 4 times the electric energy of each pulse.
That is, energy is conserved.
What we learn is that the term "cancel" in the case of two
counterpropagating pulses applies to the current and to the magnetic field,
but it does not apply to the electric field or to the field energy.
--Kirk
From: j.bordelon@comcast.net
Date: Sat, 10 Mar 2012 14:18:12 -0500
To: antenna-discussion@antennex.com
Subject: Re: [Antenna-discussion] Transmission line pulses
Perhaps the reason for the misunderstanding, David, is that two waves can
exist on the same line and yet separated because the transmission line is a
LINEAR SYSTEM. That means that the voltage at any point on the line is simply
the vector sum of two (or more) waves on the line. The principle of
SUPERPOSITION is therefore applicable and aids us in arriving at a
solution. If you are not aware of the concept of superposition then
you need to become familiar with it before attempting to progress in your
understanding.
John Bordelon, K4JIU
Marietta, GA 30066
Date: Thu, 15 Mar
2012 04:23:55 +0100
From: georg_dasekel@gmx.de
To: antenna-discussion@antennex.com
Subject: Re: [Antenna-discussion] Our forum is in danger of being obliterated
by David T.
Dear Kirk (Prof. Dr. McDonald (!) - as opposed
to Nothing Mr. Tombe, but
of course this will not impress him),
my little opinion goes parallel with those some other people here have
already mentioned. I'd also like to say a big "thank you!" to you
(and also to all the other members of this list, who are making serious
contributions, of course!).
With many of the mails from Mr. Tombe being
plainly hair-raising, I must admit that here and there he is adressing topics which I find highly interesting, and
on which I am always keenly waiting for your reply. At the same time I admire your unbelievable patience, I'm also glad
that my 'luck of the moment' keeps these replies of the group, and especially
from you, flowing in. At least to me, they mean a lot: I can only underline
what Bob said about the benefits, these discussions let me learn many new
things, and in very short time. So, yes, the idea of writing a formal
complaint to the group management did strike me, but - who would want to
destroy his 'luck of the moment'? :-)
Therefore, if you would kindly care to grill David (or
"disassemble" him, "take him apart", as we say here) a
bit more, at least I know I myself would benefit, and probably many others
here will, too. I
personally would continue to be highly exalted: Brilliant
mind meets screwball. Maybe David will eventually even realize that his
ship has sunken long back, already (or rather, that it never has floated).
Don't let him get to you, though, that's surely not worth the
efforts/stress/a heart attack/or even worse, either!
With all the very best wishes
George
Am 15.03.2012 03:30, schrieb Kirk T McDonald:
Folks,
This email from David T. is total nonsense.
-----------------------
The antennex forum is going to have to face up to
the fact that we are being "invaded" by a "virus"
in the form of a human being with very bizarre views, who is capable of
saturating our bandwidth.
I have spent some time on other technical forums, where typically they are
totally saturated by individuals who make several email replies, with zero
content, for every attempt by someone at a "serious" discussion.
The result is that these forums become totally useless.
Our wonderful antennex forum is in imminent
danger of being destroyed by the emails of David Tombe.
How shall we proceed?
--Kirk
=====================================================================================
-----Original
Message-----
From: Alex Yakovlev
Sent: Jul 20, 2020 12:15 PM
To: "Prof. A Howie" , Forrest Bishop ,
HARRY RICKER
Cc: Ivor Catt , Brian Josephson , Malcolm Davidson , Steve Crothers , Anthony
Davies , John Raymond Dore , Jack Dinsdale
Subject: Re: JD Jackson on the coax, waveguide, and transmission line
Harry,
Thank you for your vision regarding
my query and Forrest's paper.
However,
1) I admit that I may have
misunderstood what Fig. 3 is trying to demonstrate, and
2) The range of intentions of why
something is written next to a figure or a formula maybe different, but
3) Ultimately, what I can see is a
fundamental question, so
4) In my email I simply and genuinely
asked Forrest whether he has the/an answer to this question.
I would therefore like to hear from
Forrest what he thinks about this question.
Kind regards,
Alex
From: HARRY
RICKER <kc3mx@yahoo.com>
Sent: Monday, July 20, 2020 7:29 PM
To: Prof. A Howie <ah30@cam.ac.uk>;
Forrest Bishop <forrestb@ix.netcom.com>; Alex Yakovlev
<Alex.Yakovlev@newcastle.ac.uk>
Cc: Ivor Catt <ivorcatt@gmail.com>;
Brian Josephson <bdj10@icloud.com>; Malcolm Davidson <malcolmd3111@hotmail.com>; Steve Crothers
<sjc7541@gmail.com>; Anthony Davies <tonydavies@ieee.org>;
John Raymond Dore <johnrdore@gmail.com>; Jack Dinsdale <jack.dinsdale@tinyworld.co.uk>
Subject: Re: JD Jackson on the coax, waveguide, and transmission
line
Alex,
I think that you
misunderstand what Figure 3 is trying to demonstrate. Forrest has asked a
question, which is fundamental, but unclear. When the two pulses at the top
of Figure 3, pass through each, the electric field is combined additively and
the magnetic field subtracts. There is an additional assumption, which is not
stated, which is that the pulse amplitudes are equal. That means that when
the pulses cross, or pass through each other as waves do, the electric field
is doubled and the magnetic field is cancelled out and so there is no
current. The impedance is therefore infinite. This is what happens in a
capacitor, so the field is said to be a static field, since there is no
current. Forrest is asking, does this mean the static field that exists at
the moment of pulse crossing is now static or not? I think we do know the
answer is that the field is not static, and that answers Howie's objection
when he claims that the field can not be moving as
Catt says.
In electrical
engineering we say that when such things occur, that we have a standing wave.
But in Figure 3 the standing wave is ephemeral, lasting only an instant. In a
capacitor there is a permanent standing wave produced by the continuous
reflection of the EM energy such that the energy of the two waves produces a
standing wave of voltage and no current. Since there is no current, because
the currents of the two waves subtract, there is no resistive loss, although
the two waves are continuously in motion at velocity c while continuously
reflecting in an infinite cycle. Hence the resulting electric field appears
static, although it is composed of two opposite waves moving at velocity c. So the field is both static and moving at velocity
c.
The crux of the
issue is that A. Howie says the standing wave model is impossible because he
says so and offers no proof to back up what he says, just waving his hands
around. Brian J., offers ad hominem type arguments as well as hand waving.
Since we are doing science, the proof lies in the experiments which have
already been done by many different people. These are summarized by the
Wakefield results presented by Forrest. If Howie and Josephson seek to
prevail in this discussion it is incumbent upon them the show that they can
reproduce the Wakefield results by classical electromagnetism, without hand
waving. So far a number of people have attempted to
do that but all have failed. Hence unless they can show correctly that
classical EM theory can explain the results of the experiments Ivor's claim
that classical EM theory is refuted will have to stand as correct.
Harry
On Monday, July
20, 2020, 11:56:42 AM EDT, Alex Yakovlev <alex.yakovlev@newcastle.ac.uk> wrote:
Dear Forrest,
Your paper http://www.naturalphilosophy.org//pdf//abstracts/abstracts_6554.pdf is
really interesting.
Did you manage to find/get a good
answer to your question in Fig.3:
"Fig. 3. When two pulses
overlap, do their fields come to a standstill while two electric currents
obliviously pass though each other? "
I think this is a fundamental
question pertaining to a more philosophical question.
Does anything physical or material,
albeit mass-less, actually move in the file of the pulse or nothing, and what
moves is just information about the change stored in the edge dE/dt (equally dE/dx)?
Presumably, modern physics would say
that it is a photon that is moving, and the photon has the spatio-temporal characteristics such as length, right?
Kind regards
Alex
From: Forrest
Bishop <forrestb@ix.netcom.com>
Sent: Monday, July 20, 2020 3:12 PM
To: Prof. A Howie <ah30@cam.ac.uk>;
Forrest Bishop <forrestb@ix.netcom.com>
Cc: Ivor Catt <ivorcatt@gmail.com>; kc3mx@yahoo.com <kc3mx@yahoo.com>;
Brian Josephson <bdj10@icloud.com>; Malcolm Davidson <malcolmd3111@hotmail.com>; Alex Yakovlev
<Alex.Yakovlev@newcastle.ac.uk>; Steve
Crothers <sjc7541@gmail.com>; Anthony Davies <tonydavies@ieee.org>;
John Raymond Dore <johnrdore@gmail.com>; Jack Dinsdale <jack.dinsdale@tinyworld.co.uk>
Subject: Re: JD Jackson on the coax, waveguide, and transmission
line
 External
sender. Take care when opening links or attachments. Do not provide your
login details.
Dear Archie Howie,
Thank you for the pointer; I had not turned the page to the problem set,
though I vaguely remember looking at this Problem 8.1 years ago. This time, I
went so far as to try to lie, cheat, and steal the answer from one of the
several online Jackson cheat sheets. I did my due diligence here, you
understand, having a reputation to attend.
Anyway, the reason Jackson, Feynman (Lectures), and Griffiths (Intro to
Electro) do not treat the coax, waveguide, and transmission line very well is
because "the bias of a physicist" would be severely compromised by
any in-depth inquiry. I don't have a curated list on all the many reasons why
that is so, but I explain important parts of it here- http://www.naturalphilosophy.org//pdf//abstracts/abstracts_6554.pdf
and here- https://www.scribd.com/document/320890002/The-Forbidden-Equation-i-qc
One of the most important mainstream schisms is on the question of whether or
not the current-carrying lines are neutral or charged. Jackson is silent.
Switching back to the waveguide, I see the Bouncing TEM Wave is beginning to
intrude into the mainstream- https://www.slideshare.net/SyedUmar8/waveguides-44084229
This of course is anathema to Maxwell, as it violates Div
B = 0 among other things.
Forrest
-----Original Message-----
>From: "Prof. A Howie" <ah30@cam.ac.uk>
>Sent: Jul 19, 2020 3:30 AM
>To: Forrest Bishop <forrestb@ix.netcom.com>
>Cc: Ivor Catt <ivorcatt@gmail.com>, kc3mx@yahoo.com,
Brian Josephson <bdj10@icloud.com>, Malcolm Davidson <malcolmd3111@hotmail.com>, Alex Yakovlev
<Alex.Yakovlev@newcastle.ac.uk>, Steve
Crothers <sjc7541@gmail.com>, Anthony Davies <tonydavies@ieee.org>,
John Raymond Dore <johnrdore@gmail.com>, Jack Dinsdale <jack.dinsdale@tinyworld.co.uk>
>Subject: Re: JD Jackson on the coax, waveguide, and transmission line
>
>Dear Forrest Bishop,
>
>I agree that Jackson is a bit remiss not to give more prominent coverage
>to coax. Indeed my initial impression was
that he was saying nothing at
>all on this important topic. However when
you look in more detail
>things get a bit better.
>
>1. There is first of all in the second edition on p. 385 the problem 8.1
>that I alluded to previously. This uses the standard coaxial solution
>for the EM fields (based on the idealised perfect conductor model) to
>compute the EM power flow and (from Ampere's theorem) the total current
>flow I (opposite in wire and sheath). Then, abandoning the restriction
>to infinite conductivity, he uses this current flow to compute the ohmic
>losses and hence the damping (i.e. exponential
decay of he EM signal).
>I have not checked the answer given. The working is complicated by
the
>skin effect which concentrates the current density and ohmic power loss
>close to the surfaces. This approximate approach may provide some
>theoretical backing for the attenuation figures that coax sellers supply
>about their products. Working through this analysis it should be
>possible to discover what fraction if any of the power transmitted at
>any frequency is due to current flow in the electrodes.
>
>2. Earlier on in the same chapter 8 pp 335 - 339 Jackson calculates a
>corrective to the simple assumption that the tangential electric field
>has to vanish at the surface of a metal. From this it is clear that
>when account is taken of the finite conductivity of wire and sheath,
>there will (in addition to the usual purely transverse fields) be a
>small longitudinal electric field going one way at the wire surface and
>in the reverse direction at surface of the sheath. It may be that
the
>following section applying this to hollow cylindrical wave guides could
>be adapted to the coax geometry.
>
>I guess that Jackson's failure to concentrate on wave guides and not
>include coaxial cables more explicitly reflects the bias of a physicist.
>
>Archie Howie.
>
> 2vOn 2020-07-18 21:45, Forrest Bishop wrote:
>> Dear Mr. Howie,
>>
>> I've looked again through my copy of Jackson, 2nd Ed. and cannot
find
>> anything about coax cables in it. He very briefly mentions
>> transmission lines in a couple places, which is nice since our entire
>> electrified civilization depends on them. I looked at the ToC for the
>> 3rd Ed
>> https://www.academia.edu/34300390/Jackson_-_Classical_Electrodynamics_3rd_edition.pdf
>> and still don't see any coax cables or transmission line theory in
>> them. Are you referring to one of his papers, not the book?
>>
>> Some Amazon customers aren't exactly thrilled with Jackson-
>> https://www.amazon.com/Classical-Electrodynamics-Third-David-Jackson/dp/047130932X
>>
>> * " it's the standard textbook
and it's arguably the worst textbook
>> I've used."
>> * "Jackson's book needs no
introduction. Because it covers just about
>> everything in classical electrodynamics with unparalled
mathematical
>> rigor, it's been the standard graduate textbook for electromagnetics.
>> In person, the book is actually quite thin for being the bible of
>> electromagnetics. This is because almost no exposition is given for
>> the concepts presented in the book. Equation after equation is
thrown
>> at you relentlessly, and the entire book is organized haphazardly.
>> Pedagogically, the book is about as bad as it gets."
>>
>> Anyway, on waveguides, this is in Chapter 8 of Jackson (2nd Ed,
1975)
>> which I am familiar with. Turning now to Page 341 we learn that
>> "Before considering the kinds of fields that can exist inside a
hollow
>> cylinder, we take not of a degenerate or special type
of solution,
>> called the _transverse electromagnetic_ (TEM) wave..." He then
goes on
>> to support this claim by assuming the conclusion- that a TEM wave,
>> (along with all other alleged types of TE, TM waves) can only
>> propagate parallel to the long axis of the tube.
>>
>> I show this is a false model-
>> http://www.naturalphilosophy.org//pdf//abstracts/abstracts_6554.pdf
>> The TEM wave is the ONLY type of wave that can propagate in the
>> waveguide, as anyone involved in optical fiber
should know. The wave
>> doesn't propagate straight down the tube; it bounces back and forth,
>> creating the illusion of the TE, TM modes moving slower than the
speed
>> of light.
>>
>> Jackson then goes on to reproduce the standard explanation of the
>> modes using unfounded assumptions of sine wave solutions, contrived
>> boundary conditions, etc. and arrives at the usual conclusion, that
>> this method "constitutes a complete set of fields to describe
an
>> arbitrary electromagnetic disturbance in a waveguide or
cavity." (Page
>> 342)
>>
>> In the process, he is inventing all kinds of "New
Physics", e.g.
>>
>> * The speed of an EM wave depends on
the shape of the metal tube.
>> * The tube creates all kinds of new EM
waves, unknown anywhere
>> outside of the tube.
>> * An electric field, measured in
volts/meter, can close upon itself!
>> So when we measure the voltage along the closed electric field line,
>> starting from any point, we eventually come back to the beginning of
>> the loop, where V = Vtotal AND V =0,
simultaneously.
>>
>> I think Jackson knows this, and is therefore a conscious grifter. He
>> also treated/rebutted Catt, Davidson Walton
>> http://www.ivorcatt.com/2635.htm in a
paper addressed to John Roche
>> (in a European physics journal). In that treatment, he takes an
>> ensemble of static solutions for the charging-state of a capacitor,
>> then adds them together in time as if the charges can move from one
>> state to the next at an infinite speed. Again- a grifter.
>>
>> Now, for coax cable and twin-lead transmission lines, which are the
>> only two cases geometrically possible, the transmission efficiency
of
>> the TEM wave depends in part on the uniformity of the cross section.
>> (This also applies to the waveguide, which Jackson is silent on.).
The
>> great advances in serial communication speeds are in part a result
of
>> better wire-die and drawing technology- which owes exactly nothing
to
>> Classical Electrodynamics.
>>
>> For data transmission using TEM waves, ohmic losses are secondary,
as
>> they do not affect the S/N ratio the way variable impedance does.
>>
>> Forrest
>>
>>> -----Original Message-----
>>>> From: "Prof. A Howie"
>>>> Sent: Jul 18, 2020 9:04 AM
>>>> To: Ivor Catt
>>>> Cc: kc3mx@yahoo.com, Forrest Bishop , Brian
Josephson , Malcolm
>>> Davidson , Alex Yakovlev , Steve Crothers , Anthony Davies ,
John
>>> Raymond Dore , Jack Dinsdale
>>>> Subject: Re: can the the trance
state account for protective
>>> stupidity?
>>>>
>>>> Dear Ivor,
>>> ...
>>>
>>>> I would not badge myself as an expert on coaxial cables or
>>> transmission
>>>> lines but I think that I do have a reasonable grasp by now
of
>>> current
>>>> theory of their operation. The generally used theory of the
TEM
>>> mode in
>>>> a coaxial cable gets simplicity and practical utility by
assuming
>>> that
>>>> the metal components are perfect conductors. The main
practical
>>>> consequence that is lost here is attenuation of the signal
which is
>>>
>>>> certainly a measurable effect with figures quoted by sellers
of
>>>> different brands of coaxial cable. These quoted figures also
>>> increase
>>>> like the square root of the frequency as would be expected.
>>> Fortunately
>>>> the attenuation in a system involving metals can also be
>>> calculated,
>>>> probably to a good approximation by using Ampere's theorem
for
>>> deduce
>>>> the currents from the transverse fields given by the simple
>>>> approximation and then computing the ohmic losses per unit
length
>>> of
>>>> cable (see the problem I referred to in chapter of Jackson).
In the
>>>
>>>> same chapter Jackson calculates an approximate correction to
these
>>>> fields finding a small additional longitudinal electric
field
>>> component
>>>> near wire and sheath with a sign reversal between these. For
those
>>> who
>>>> require it, there is thus a more visible driving force for
the wire
>>>
>>>> current and the reverse current in th
sheath. It would certainly be
>>>
>>>> nice to have a more complete theory which would map out the
>>> Poynting
>>>> vector flow in the dielectric which (as Jackson's field
corrections
>>>
>>>> indicate) would have a small component of energy flow into
the wire
>>> and
>>>> sheath.
>>>>
>>>> There is obviously an incomplete connection between a fully
>>> rigorous
>>>> theory for coaxial cables and practical exploitation (where
the
>>> simple
>>>> theory plus fudged attenuation is good enough). It seems to
me that
>>>
>>>> there may be quite a close parallel with the situation over
house
>>> wiring
>>>> where, as you have pointed out, traditional current flow,
ohm's law
>>> etc
>>>> can apparently be successfully used without reference or
knowledge
>>> of
>>>> energy transport in a surrounding EM field.
>>>>
>>>> I would agree that it would be interesting to explore in
more
>>> detail the
>>>> role of EM fields in the charging or discharge of a
capacitor
>>> through
>>>> coaxial cable. As indicated above however this needs a
better
>>> coaxial
>>>> theory with proper coupling between fields and current in
>>> non-perfect
>>>> conductors. It will not be possible to get consensus however
when
>>> there
>>>> is continuing disagreement about the description of the
state of
>>> charged
>>>> capacitor. As reported by Yakovlev, Wakefield's experiments made a
>>> good
>>>> step in addressing the charging problem. I have not
followed
>>> details of
>>>> the history here but have a suspicion that his work might
have
>>> received
>>>> a better reception had not been festooned with with so many claims
>>> about
>>>> basic failures in electrodynamic theory.
>>> ...
>>>> Archie Howie.
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