On Jan 3, 12:25*pm, Art Unwin wrote:
On Jan 3, 11:33*am, "Frank" wrote:



wrote in message

....

I've been using 4Nec2, a freeware antenna modeling program based on
NEC-2 (Numerical Electromagnetic Code). I'm wondering if anyone could
provide some insight as to just how it models current at the ends of
wires that are not connected to anything (a.k.a. "free ends" or "open
ends").

Does NEC-2 model "end caps" at free ends, which is equivalent to
assuming wires are solid, or does it just set the current equal to
zero at the free ends, which is equivalent to assuming wires are
hollow? Is it possible that it does both, but the specific model is
determined by the choice of computational kernel (extended vs.
standard)?

I've tried looking through some of the NEC-2 documentation, but I
can't find a definitive answer.

-Dave, K3WQ

This is covered in:http://www.nec2.org/other/nec2prt1.pdf
pp 11 - 12.

Frank

Frank
Please keep in mind the following
NEC is based totally on the *extremely thin wire where various
assumption can be made
such as equations being equal to zero in the limit., These same
assumptions can not be held to
when dealing with thick radiators despite the closeness of the
approximations.
Best regards
Art

Calculus is based on homogenous materials or planes where you can
refer dy/dx to
some thing aproaching zero. In the case of using this aproach where
the antenna diameter aproaches zero
this is an invalid aproach for accuracy but O.K. for aproximations. So
much for the foibles of theoretical mathematics.
The vanishing thin radiator cannot be applied directly to a non
homogenous material because at the limits of the the diameter
is unable to support the presence of eddy currents(skin depth) . In
other words the assumption of limi tess ness cannot be held if the
presence of
skin effect is true. Ofcourse if skin effect is not present then you
have a DC current where only copper losses are present.
As always with mathematics assumptions and preconditions are alway
subject to examination. This in no way takes away from the advantages
oif the NEC programs.
Art

Frank
Please keep in mind the following
NEC is based totally on the extremely thin wire where various
assumption can be made
such as equations being equal to zero in the limit., These same
assumptions can not be held to
when dealing with thick radiators despite the closeness of the
approximations.
Best regards
Art

The reference at http://www.nec2.org/other/nec2prt1.pdf p 21 deals
with the accuracey of NEC 2 in respect to the "Thin wire approximation".
From the NEC-4, theory manual, p 21, para 4: ".... the NEC-4 wire model
employes the extended boundary condition in the thin wire approximation,
so that the current is treated as a tubular distribution on the wire
surface......."

Calculus is based on homogenous materials or planes where you can
refer dy/dx to
some thing aproaching zero. In the case of using this aproach where
the antenna diameter aproaches zero
this is an invalid aproach for accuracy but O.K. for aproximations. So
much for the foibles of theoretical mathematics.

Your comments about calculus are confusing. A derivative
is always non-zero -- unless you are differentiating a constant.
The homogeneity, or otherwise, of a material is irrelevant
to the process of differentiation.

The vanishing thin radiator cannot be applied directly to a non
homogenous material because at the limits of the the diameter
is unable to support the presence of eddy currents(skin depth) . In
other words the assumption of limi tess ness cannot be held if the
presence of skin effect is true.

Most conductors are homogeneous. In fact I cannot think of
a non-homogeneous conductor. Even in plated conductors
the current flows in the plating.

Of course if skin effect is not present then you
have a DC current where only copper losses are present.
As always with mathematics assumptions and preconditions are alway
subject to examination. This in no way takes away from the advantages
oif the NEC programs.
Art

Copper loss still exists for high frequency currents.

73, Frank

On Jan 3, 2:44*pm, "Frank" wrote:
Frank
Please keep in mind the following
NEC is based totally on the extremely thin wire where various
assumption can be made
such as equations being equal to zero in the limit., These same
assumptions can not be held to
when dealing with thick radiators despite the closeness of the
approximations.
Best regards
Art

The reference athttp://www.nec2.org/other/nec2prt1.pdf*p 21 deals
with the accuracey of NEC 2 in respect to the "Thin wire approximation".
From the NEC-4, theory manual, p 21, para 4: ".... the NEC-4 wire model
employes the extended boundary condition in the thin wire approximation,
so that the current is treated as a tubular distribution on the wire
surface......."

Calculus is based on homogenous materials or planes where you can
refer dy/dx to
some thing aproaching zero. In the case of using this aproach where
the antenna diameter aproaches zero
this is an invalid aproach for accuracy but O.K. for aproximations. So
much for the foibles of theoretical mathematics.

Your comments about calculus are confusing. *A derivative
is always non-zero -- unless you are differentiating a constant.
The homogeneity, or otherwise, of a material is irrelevant
to the process of differentiation.
That is exactly my point. The skin is not hogenoius even if you
consider the resistive action to be constant in depth thus you cannot
put a limit on the thicknes
or diameter of the radiator! If you do put a limit anyway on skin
depth then you cannot apply the reasoning to a hollow tube.
We can talk back and forwards for ever on the analogy provided with
vanishingly thin radiators but until we break apart the mathematics
such that there is a reflection at the end of a radiator the posters
question cannot be answered.
If one is to model the situation as Cecil suggests we must first
determine how and where the reflection is created and the
applied math provided to support it. I can see no reference via
mathematics that shows the reversal or reflection of current flow
prior to the end of a cycle.If there were such an instance then there
must be a determination of the resistance radiation or otherwise
so that any assumption made is factual.




The vanishing thin radiator cannot be applied directly to a non
homogenous material because at the limits of the *the diameter
is unable to support the presence of eddy currents(skin depth) . In
other words the assumption of limi tess ness cannot be held if the
presence of skin effect is true.

Most conductors are homogeneous. *In fact I cannot think of
a non-homogeneous conductor. *Even in plated conductors
the current flows in the plating.

No that is not true as homogenous implies equilibrium and for skin
depth the value (e) comes into beingor what so0me would refer to as
decay

Of course if skin effect is not present then you
have a DC current where only copper losses are present.
As always with mathematics assumptions and preconditions are alway
subject to examination. This in no way takes away from the advantages
oif the NEC programs.
Art

Copper loss still exists for high frequency currents.

Very true Frank but the radiation resistance plus the resistance
encoutered by surface flow is not related/
proportional to the pure copper losses where skin resistance is not
present where in the absence of
skin depth leaves one with DC pulses.

I am ofcourse still interested what the NEC programs show for
reflection and consequental resistance
which I believe was in Cecil's thoughts to determine the truth.
Hopefully the dialogue between you and I will not drop to the level of
David's where he contendes that Gaussian law of STATICS
is one of the basic laws that Maxwell applied/used without the
required proof..On top of which he denies the applicability of statics
with electro magnetics thus any mathematical aproach cannot be
applicable which is absolutely crazy
The thrust of this thread is solely on the difference of radiation
with respect to hollow radiators and solid radiators and it should be
kept at that to provide a reasonable answer as required in any formal
debate.

73, *Frank

"Art Unwin" wrote in message
...
On Jan 3, 2:44 pm, "Frank" wrote:
David's where he contendes that Gaussian law of STATICS
is one of the basic laws that Maxwell applied/used without the
required proof..On top of which he denies the applicability of statics
with electro magnetics thus any mathematical aproach cannot be
applicable which is absolutely crazy

well art, here is your proof, from the same ramo whinnery and van duzer book
you like to quote....
compare equation (2) in section 2.09 with equation (1) in section 4.07.
note there is no time in either one of them... and section 2 is specifically
about stationary fields, while sectino 4 is maxwell's equations. only 2 of
maxwell's equations actually are about time varying fields, those are
Faraday's law and Ampere's law. The other two are Gauss's law taken
straight from the static case, and the equivalent for magnetic flux... both
of which are time invarient.

The thrust of this thread is solely on the difference of radiation
with respect to hollow radiators and solid radiators and it should be
kept at that to provide a reasonable answer as required in any formal
debate.

the only thing hollow about this debate is your head.

On Jan 3, 4:56*pm, "Dave" wrote:
"Art Unwin" wrote in message

...
On Jan 3, 2:44 pm, "Frank" wrote:

David's where he contendes that Gaussian law of STATICS
is one of the basic laws that Maxwell applied/used without the
required proof..On top of which he denies the applicability of statics
with electro magnetics thus any mathematical aproach cannot be
applicable which is absolutely crazy

well art, here is your proof, from the same ramo whinnery and van duzer book
you like to quote....
compare equation (2) in section 2.09 with equation (1) in section 4.07.
note there is no time in either one of them... and section 2 is specifically
about stationary fields, while sectino 4 is maxwell's equations. *only 2 of
maxwell's equations actually are about time varying fields, those are
Faraday's law and Ampere's law. *The other two are Gauss's law taken
straight from the static case, and the equivalent for magnetic flux... both
of which are time invarient.

The thrust of this thread is solely on the difference of radiation
with respect to hollow radiators and solid radiators and it should be
kept at that to provide a reasonable answer as required in any formal
debate.

the only thing hollow about this debate is your head.

David
I bought that book because you refered to it some time ago where you
misrepresented
what you alluded to and now you are doing it again. In your method of
reading did the law that a radiator can be any shape, size or
elevation as long as it is in equilibrium? I can't conceive that a
mathematition of Maxwells staturer could have missed that observation
if as you say he extended gaussian law of statics. Perhaps you have an
answer for that also of the back of your head.
Your positions continue to be absurd from an engineering point of view
and nobody as yet has confirmed your position and what is really wierd
none have denied
Art

"Art Unwin" wrote in message
...
I bought that book because you refered to it some time ago where you
misrepresented
what you alluded to and now you are doing it again.

misrepresented??? its right in the book, compare those two formula, are
they not the same? is not guass's law, which is a time invarient equation
directly in maxwell's equations??

In your method of
reading did the law that a radiator can be any shape, size or
elevation as long as it is in equilibrium?

if you can find where 'equilibrium' is a required condition in maxwell's
equations, give me the reference in the book. otherwise you are out of
equilibrium.

I can't conceive that a
mathematition of Maxwells staturer could have missed that observation
if as you say he extended gaussian law of statics. Perhaps you have an
answer for that also of the back of your head.

sure, he didn't 'extend' it... he used it verbatum as the book shows. there
is no need to 'extend' it, its a perfectly good law as it is stated and has
been for many years.

our positions continue to be absurd from an engineering point of view
and nobody as yet has confirmed your position and what is really wierd
none have denied

because they are enjoying laughing at your absurd positions as much as i am!

On Jan 3, 5:57*pm, "Dave" wrote:
"Art Unwin" wrote in message

...

I bought that book because you refered to it some time ago where you
misrepresented
what you alluded to and now you are doing it again.

misrepresented??? *its right in the book, compare those two formula, are
they not the same? *is not guass's law, which is a time invarient equation
directly in maxwell's equations??

In your method of
reading did the law that a radiator can be any shape, size or
elevation as long as it is in equilibrium?

if you can find where 'equilibrium' is a required condition in maxwell's
equations, give me the reference in the book. *otherwise you are out of
equilibrium.

I can't conceive that a
mathematition of Maxwells staturer could have missed that observation
if as you say he extended gaussian law of statics. Perhaps you have an
answer for that also of the back of your head.

sure, he didn't 'extend' it... he used it verbatum as the book shows. *there
is no need to 'extend' it, its a perfectly good law as it is stated and has
been for many years.

our positions continue to be absurd from an engineering point of view
and nobody as yet has confirmed your position and what is really wierd
none have denied

because they are enjoying laughing at your absurd positions as much as i am!

Oh My Do you really believe that you are talking on behalf of the
masses?
When Dr Davis of M.I.T. said contrary to the thinking of this group
that Gauss's law of statics
when extended, as I stated, is mathematically the equal to Maxwells
laws as per Maxwells correction.
Many a post has been written since that day castigating the very idea
of equivalence to Maxwell,w
even questioning the propriety of the mathematics. So far nobody has
concurred with Dr Davis
with respect to the math that he presented. You David stated that the
mathematical stance taken was illegal
because there is no connection with respect to statics ! David you
have no credability as anyone who owns a copy of that book can easily
confirm for themselves..Just look at what you now have stated that you
have found the connection
( tho I doubt it) with respect to Statics. Ofcourse if somebody wants
to debate your statement on your behalf I will be happy to refute what
you say page by page. Until then the book stays on the shelf because
of past experiences with your statements.
In Maxwells time he was given credit for what appeared as proof of the
wave theory even to the point of extrapolating same to light
because of the "c" property in his correction which he obtained by
ensuring compliance to Newtons law with respect to equilibrium.
It was decades before Foucalt came along with his discovery of a field
that matched the Maxwell correction where prior to there was none. Now
we can debunk the wave theory as the particle is now in stone
Art Unwin KB9MZ......xg (uk)