Dave wrote:

"Art Unwin" wrote in message
...

( I am assuming that skin depthg is not limitless.)

of course it is limitless, it is an exponential function so it never
goes to zero. the so called 'skin depth' is only the point where the
current has dropped to 1/e or about 37% of the surface value, still a
significant current.

The plots at the link Frank provided show current going rather abruptly
to zero - even negative ("contrary"?) in some cases. I wouldn't presume
to know whether it is modeled correctly.

ac6xg

The plots at the link Frank provided show current going rather abruptly
to zero - even negative ("contrary"?) in some cases. I wouldn't presume
to know whether it is modeled correctly.

ac6xg

Having some expience of Ansoft's FEM modeling software I feel the
results are highly credible. Also Rudy Severns publishing list is pretty
impressive:
http://www.snubberdesign.com/Springt...terprises.html

73,

Frank (VE6CB)

On Jan 13, 10:19*pm, "Frank" wrote:
The plots at the link Frank provided show current going rather abruptly
to zero - even negative ("contrary"?) in some cases. *I wouldn't presume
to know whether it is modeled correctly.

ac6xg

Having some expience of Ansoft's FEM modeling software I feel the
results are highly credible. *Also Rudy Severns publishing list is pretty
impressive:http://www.snubberdesign.com/Springt...terprises.html

73,

Frank (VE6CB)

Frank, I am not saying he is not credible but he is part of the older
generation and there was not enough detail supplied to determine
whether I accept it on trust. When the antenna programs
throw out the yagi in favor of arrays or radiators in equilibrium form
should we throw it out in favor of conforming with the past? Yes,the
article is in line with what the older generation has lived with
but the new generation have more tools and information than the
present dying generation.
Problem with present day authors is up against the "publish or
perish" format regure references to prior papers in quantity to
provide legitamacy to any new papers, without which they will have a
hard time publishing. Greasing the wheels of fellow contributers or
white paper authors is much preferable to declaring those who judge
are in error. Frank, a lot of the theory of antennas is either based
on vanishingly thin radiators without regard to room required for eddy
field and in some cases with transmission lines where it is possible
to get three different current flows together with a closed circuit,
yet we are now protecting the idea of non closed circuits where the
current flow
is on top of each other. No wonder it is said over the last 100 years
that we don't fully understand radiation especially when it takes over
70 posts on how to make a cantenna from a panel of experts
Best regards
Art

Frank, I am not saying he is not credible but he is part of the older
generation and there was not enough detail supplied to determine
whether I accept it on trust. When the antenna programs
throw out the yagi in favor of arrays or radiators in equilibrium form
should we throw it out in favor of conforming with the past? Yes,the
article is in line with what the older generation has lived with
but the new generation have more tools and information than the
present dying generation.
Problem with present day authors is up against the "publish or
perish" format regure references to prior papers in quantity to
provide legitamacy to any new papers, without which they will have a
hard time publishing. Greasing the wheels of fellow contributers or
white paper authors is much preferable to declaring those who judge
are in error. Frank, a lot of the theory of antennas is either based
on vanishingly thin radiators without regard to room required for eddy
field and in some cases with transmission lines where it is possible
to get three different current flows together with a closed circuit,
yet we are now protecting the idea of non closed circuits where the
current flow
is on top of each other. No wonder it is said over the last 100 years
that we don't fully understand radiation especially when it takes over
70 posts on how to make a cantenna from a panel of experts
Best regards
Art

I would hardly call the tools used in this simulation "Older".
Ansoft produces some of the most sophisticated, and up to
date FEM software available. I have seen Ansoft's HFSS
accurately model current flow through PCB vias, around an end-
launch connector at 20 GHz. CST Microwave also
produces high end FEM software. All the models are
done in full 3 D, with actual physical dimensions. This
FEM software started to apear about 10 years ago and
costs in the range of $40,000 to $50,000, with a $10,000
per year maintenance fee.

"Publish or perish" is usually applied to university positions.
It is doubtfull that too many people are able to pubish in
the Proceedings of the IEEE, or one of the IEEE Society
Transactions.

On Jan 13, 11:23*pm, "Frank" wrote:
Frank, I am not saying he is not credible but he is part of the older
generation and there was not enough detail supplied to determine
whether I accept it on trust. When the antenna programs
throw out the yagi in favor of arrays or radiators in equilibrium form
should we throw it out in favor of conforming with the past? Yes,the
article is in line with what the older generation has lived with
but the new generation have more tools and information than the
present dying generation.
Problem with present day authors is *up against the "publish or
perish" format regure references to prior papers in quantity to
provide legitamacy to any new papers, without which they will have a
hard time publishing. Greasing the wheels of fellow contributers or
white paper authors is much preferable to declaring those who judge
are in error. Frank, a lot of the theory of antennas is either based
on vanishingly thin radiators without regard to room required for eddy
field and in some cases with transmission lines where it is possible
to get three different current flows together with a closed circuit,
yet we are now protecting the idea of non closed circuits where the
current flow
is on top of each other. No wonder it is said over the last 100 years
that we don't fully understand radiation especially when it takes over
70 posts on how to make a cantenna from a panel of experts
Best regards
Art

I would hardly call the tools used in this simulation "Older".
Ansoft produces some of the most sophisticated, and up to
date FEM software available. *I have seen Ansoft's HFSS
accurately model current flow through PCB vias, around an end-
launch connector at 20 GHz. *CST Microwave also
produces high end FEM software. *All the models are
done in full 3 D, with actual physical dimensions. *This
FEM software started to apear about 10 years ago and
costs in the range of $40,000 to $50,000, with a $10,000
per year maintenance fee.

"Publish or perish" is usually applied to university positions.
It is doubtfull that too many people are able to pubish in
the Proceedings of the IEEE, or one of the IEEE Society
Transactions.

Frank,
It has not yet been proven that current does not flow thru the center
of a radiator.
I see it as a manufactured statement to satisfy the idea of an
uncompleted circuit where the current
passes over or thru and in a different direction than the same current
that generates its existence !
It does all this where the books state it is a series circuit where
the paths taken by the current are not identical. Why manufacture all
these happenings to prove what is just a theory, while at the same
time destroying the reasoning of a closed circuit without an
explanation how such actions
creat radiation, especially when it is admitted that radiation is not
fully understood?
I think the time as come to review again from the time of Maxwell and
build up afresh in line with
a century of findings and then re evaluate.
A good start would be to evaluate why antenna programs based on
Maxwells laws provide solutions based on equilibrium while discarding
all other designs. Saying that it can't be! Because" "if true it
would have been discovered a 100 years ago" while silently adding "all
is known about antennas and the patent offices should be closed"
Regards
Art

On Jan 14, 12:07*am, Art Unwin wrote:

It has not yet been proven that current does not flow thru
the center of a radiator.

Assuming that significant r-f current exists at the center of a
radiating conductor, where does it go when it reaches the end of that
conductor?

RF

Richard Fry wrote:
On Jan 14, 12:07 am, Art Unwin wrote:

It has not yet been proven that current does not flow thru
the center of a radiator.

Assuming that significant r-f current exists at the center of a
radiating conductor, where does it go when it reaches the end of that
conductor?

RF


It doesn't "go" anywhere. As the conductor (and it's return path;
ground or whatever) is resonant, the generator sees it as a resistor.
The current is "absorbed" by this "load". But instead of pure heat, an
electromagnetic field ensues. Nothing goes anywhere.

Richard Fry wrote:
On Jan 14, 12:07 am, Art Unwin wrote:

It has not yet been proven that current does not flow thru
the center of a radiator.

Assuming that significant r-f current exists at the center of a
radiating conductor, where does it go when it reaches the end of that
conductor?


Ahh.. the famous "boundary condition"..

Say you've got a big bar 100 feet long and a foot in diameter, and
you've induced a rf current along it by some means. All those equations
with the Bessel functions tell you the magnitude and phase of the
current in some infinitely thin slice in the middle.

But, at the end, those equations don't hold. Essentially, the "reverse
current" flows radially across the end and forms part of the "forward
current" on the surface.

I doubt there is a good analytical solution of this. There's probably
some decent approximations (within 5% or something), but anyone who
really cares is going to do a FEM analysis of some sort and solve the
problem numerically.


RF

Art wrote:
"Frank, It has not yet been proven that current does not flow through
the center of the radiator."

It definitely has been proven that significant current does not
ordinarily flow through the center of a radiating conductor.

Skin effect is an accepted and observed phenomenon.

An RF conductor has a radial E-field, its lines terminating on its
surface. Also, the current carrying conductor has has an H-field whose
lines encircle it. The E-field lines are not exactly
perpendicular to to the conductor`s surface but inclined at a slight
angle to it. The surfaces of equal phase are cupped inward slightly on
the forward side as if the wave were dragging its feet along the
conductor`s surface. The H lines are parallel to the conductor`s
surface. Direction of propagation of the energy is at right angles to
both the E and H fields, but not quite parallel to the conductor`s
surface. It is inclined slightly toward the inside of the conductor.
Direction of propagation can be indicated by a vector P. P can be
resolved into two components, PL and PR . PL represents the longitudinal
component of vector P. PR represents the small amount of energy which is
being drained away from the transmitted signal and dissipated as heat in
the conductor. Radial E lines of force tilted forward in propagation
along the conductor are slowed and short-circuited by the conducting
material through which they are moving. This current flowing through the
resistance of the conductor causes I squared R losses. It also gives
rise to a magnetic field within the conductor which opposes the external
H field.

The result of the above is that the density of the current is quite high
at the copnductor`s surface, diminishing as we look inward toward the
center. The relative phase of the current, in addition, is not the same
at all depths; because of the slow velocity of propagation of the wave
within the conductor, the phase of the current is progressively delayed
as we examine it at greater depths. At some depth, the phase of the
current may be 180 degrees behind that of the surface current, which
means that it is flowing in the opposite direction! The integral of the
current density, integrated over the entire cross-sectional area of the
conductor, will of course be equal to the current in the conductor as
would be read by an ammeter.

Not all conductors are solid copper or aluminum. Seawater has been
thoroughly inveatigated in regard to communication with submarines.
Actual RF currents at all depths have been calculated and measured.

Best regards, Richard Harrison, KB5WZI

Frank,
It has not yet been proven that current does not flow thru the center
of a radiator.

I thought I did prove it at:
http://www3.telus.net/nighttrainexpr...in%20depth.htm
Or are you saying that the developers of FEM software at Ansoft,
CST Microwave, and many others do not know what they
are doing? FEM software (and NEC) has been verified countless
times experimentally. Are you saying that nobody knows how to
use test equipment. Check out the testimonials for CST at:
https://www.cst.com/Content/Company/Testimonials.aspx
In fact there is a procedure that will measure the distribution
of current through a cylindrical conductor.

I see it as a manufactured statement to satisfy the idea of an
uncompleted circuit where the current
passes over or thru and in a different direction than the same current
that generates its existence !
It does all this where the books state it is a series circuit where
the paths taken by the current are not identical. Why manufacture all
these happenings to prove what is just a theory, while at the same
time destroying the reasoning of a closed circuit without an
explanation how such actions
creat radiation, especially when it is admitted that radiation is not
fully understood?

It sounds like you are confusing this with a DC circuit.

I think the time as come to review again from the time of Maxwell and
build up afresh in line with
a century of findings and then re evaluate.
A good start would be to evaluate why antenna programs based on
Maxwells laws provide solutions based on equilibrium while discarding

How do you know the programs are based on "Equilibrium"? --
Whatever that means. Can you provide any mathematical or
experimental evidence. Since you have admitted you do not
understand high school math how can you possibly make such
statements.

all other designs. Saying that it can't be! Because" "if true it
would have been discovered a 100 years ago" while silently adding "all
is known about antennas and the patent offices should be closed".

Judging by the "IEEE Transactions on Antennas and Propagation"
nobody thinks all is known about antennas.


Regards
Art