If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)
Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect. This would, I believe, opposes the progression of
skin depth with respect to frequency.
The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment! Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?
Where has my intuition gone wrong in opposing the books?

Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)

Yes, because the attenuation from an enclosure is made up of a
reflection loss and an absorption loss. The absorption loss is
proportional to both the thickness of the material and the frequency (
amongst other things). So a thin shield will have less attenuation at
low frequencies.

Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect. This would, I believe, opposes the progression of
skin depth with respect to frequency.

Why does intuition tell you that? My intuition tells me that you need
smaller holes as you increase the frequency?

Also when you refer to the size of holes are you referring to their
diameter, spacing or both?


The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment!

Why? The box had no holes! Adding holes will just degrade the screening
from the starting point of a continuous screen. The larger the
diameter of the holes the worse the screening will be degraded at a
particular frequency, and the degradation will also be proportional to
wavelength, large holes wrt wavelength, the more signal will leak through.


Jeff

On Mar 21, 5:42*am, Jeff wrote:
Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)

Yes, because the attenuation from an enclosure is made up of *a
reflection loss and an absorption loss. The absorption loss is
proportional to both the thickness of the material and the frequency (
amongst other things). So a thin shield will have less attenuation at
low frequencies.

Thanks first for your thoughtful response. The article mentions only
skin depth and frequency applied so in effect frequency is the only
variable
Agreed
The above states that as you go down in frequency (a longer
wavelength) that it becomes
easier for propagation to be available at the other side. Stated
another way the deeper the
the skin depth the more penetration occurs

* *Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect. This would, I believe, opposes the progression of
skin depth with respect to frequency.


Why does intuition tell you that? *My intuition tells me that you need
smaller holes as you increase the frequency?

The experiment shows that it is easier for the lower frequency to
penetrate to the other side than the higher frequency. Or another way
as you move higher in frequency a better blocking effect occurs. If I
add perforations the same progression arises with respect to hole
diameter. (Note in the experiment we only have two variables, skin
depth and frequency, everything else is seen as a constant by the
experimenter. Not knowing the thickness of the screen could possibly
bring us into the situation of circuit boards where the skin depth is
deeper than the trace thickness but that may be a red herring)
From my perspective adding holes will provide the FM wavelengths more
leverage
to penetrate to the other side!


Also when you refer to the size of holes are you referring to their
diameter, spacing or bot

I was comparing voids to bulk.



* * The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment!

Why? *The box had no holes! Adding holes will just degrade the screening
* from the starting point of a continuous screen. The larger the
diameter of the holes the worse the screening will be degraded at a
particular frequency, and the degradation will also be proportional to
wavelength, large holes wrt wavelength, the more signal will leak through..

agreed

Jeff

I used the perforations as a method of reducing the screening in both
cases to make a point

Jeff, I am stating that my path of thought took me into a different
direction from the books.
Thus I have to assume that my logic or aproach is in error. The
question thus is where is my error , That is where I need direction?

On Mar 21, 4:49*am, Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)
* *Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect. This would, I believe, opposes the progression of
skin depth with respect to frequency.

wrongo buzzard breath.

* * The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment! Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?
Where has my intuition gone wrong in opposing the books?

everywhere, right from the beginning.

Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)

What did the Harvard experiment in Boston describe as the cause for
this? Some vague reference to an experiment somewhere does not show
anything. Provide a proper link if you want anyone to take the reference
seriously.


Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect.

I believe this conflicts with your particle concepts. Why should hole
size have any effect on spinning particles of different frequencies?

You position also is in conflict with general understanding. If you are
correct, what hole size blocks very high frequencies. You concept would
result in a simple wire frame enclosure.


This would, I believe, opposes the progression of
skin depth with respect to frequency.
The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment!

You may be ignoring the differences in the antennas. AM may have used a
ferrite loop, while FM may have been a whip. (We don't know because you
provide no details.)

Could one antenna be responding the magnetic component of the signal
more than the other? (We don't know because you provide no details.)


Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?

Type of materials, type of antenna, relative dimension may all play a
factor. You need to determine all of the effects that enter into the
situation and not focus on one or two.

Where has my intuition gone wrong in opposing the books?

Probably because you don't pay attention to the details and are relying
upon an understanding of the topic that is not correct.

On Mar 21, 9:15*am, joe wrote:
Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)

What did the Harvard experiment in Boston describe as the cause for
this? Some vague reference to an experiment somewhere does not show
anything. Provide a proper link if you want anyone to take the reference
seriously.

* *Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect.

I believe this conflicts with your particle concepts. Why should hole
size have any effect on spinning particles of different frequencies?

You position also is in conflict with general understanding. If you are
correct, what hole size blocks very high frequencies. You concept would
result in a simple wire frame enclosure.

This would, I believe, opposes the progression of
skin depth with respect to frequency.
* * The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment!

You may be ignoring the differences in the antennas. AM may have used a
ferrite loop, while FM may have been a whip. (We don't know because you
provide no details.)

Could one antenna be responding the magnetic component of the signal
more than the other? (We don't know because you provide no details.)

Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?

Type of materials, type of antenna, relative dimension may all play a
factor. You need to determine all of the effects that enter into the
situation and not focus on one or two.

Where has my intuition gone wrong in opposing the books?

Probably because you don't pay attention to the details and are relying
upon an understanding of the topic that is not correct.

Thanks for your response.
The article only gave me the given facts for the experiment and
nothing more.Yes my concepts on radiation are in opposition to the
norm so I am using the facts presented as a way of destructing or
confirming my perceptions.
When I read up on Faraday shields the concept of "particles"
predominates as opposed to "waves" without exception and I am trying
to make some sense of these differences when considering propagation.
With respect to receive of the radio. Since the foil is flat and
without perforation it should be sensitive to everything thrown at it.

Art Unwin wrote:
On Mar 21, 9:15 am, joe wrote:
Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)
What did the Harvard experiment in Boston describe as the cause for
this? Some vague reference to an experiment somewhere does not show
anything. Provide a proper link if you want anyone to take the reference
seriously.

Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect.
I believe this conflicts with your particle concepts. Why should hole
size have any effect on spinning particles of different frequencies?

You position also is in conflict with general understanding. If you are
correct, what hole size blocks very high frequencies. You concept would
result in a simple wire frame enclosure.

This would, I believe, opposes the progression of
skin depth with respect to frequency.
The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment!
You may be ignoring the differences in the antennas. AM may have used a
ferrite loop, while FM may have been a whip. (We don't know because you
provide no details.)

Could one antenna be responding the magnetic component of the signal
more than the other? (We don't know because you provide no details.)

Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?
Type of materials, type of antenna, relative dimension may all play a
factor. You need to determine all of the effects that enter into the
situation and not focus on one or two.

Where has my intuition gone wrong in opposing the books?
Probably because you don't pay attention to the details and are relying
upon an understanding of the topic that is not correct.

Thanks for your response.
The article only gave me the given facts for the experiment and
nothing more.

If it is this article,
http://www.fas.harvard.edu/~scidemos...SkinDepth.html
Then more was given.

It was an experiment in skin depth.
AM was significantly attenuated, too.
It specified the frequencies used and the associated skin depth.
The radio is also specified.

Using an extremely cheap radio as a measurement tool is not sound
technically.



Yes my concepts on radiation are in opposition to the
norm so I am using the facts presented as a way of destructing or
confirming my perceptions.



When I read up on Faraday shields the concept of "particles"
predominates as opposed to "waves" without exception and I am trying
to make some sense of these differences when considering propagation.

Perhaps it is a problem with how you do searches. On this page
http://en.wikipedia.org/wiki/Faraday_cage
There is no mention of particles as the means of transport to the
shield. Electrons are mentioned as they are part of the cage and respond
to applied fields.

With respect to receive of the radio. Since the foil is flat and
without perforation it should be sensitive to everything thrown at it.

But the experiment in question is about skin depth which does vary with
frequency.

Unless, of course, you are talking about some other Harvard article, but
we only have to guess, because you still don't identify it.

How do you expect us to know what you are really talking about?

On Mar 21, 11:59*am, joe wrote:
Art Unwin wrote:
On Mar 21, 9:15 am, joe wrote:
Art Unwin wrote:
If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)
What did the Harvard experiment in Boston describe as the cause for
this? Some vague reference to an experiment somewhere does not show
anything. Provide a proper link if you want anyone to take the reference
seriously.

* *Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect.
I believe this conflicts with your particle concepts. Why should hole
size have any effect on spinning particles of different frequencies?

You position also is in conflict with general understanding. If you are
correct, what hole size blocks very high frequencies. You concept would
result in a simple wire frame enclosure.

This would, I believe, opposes the progression of
skin depth with respect to frequency.
* * The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment!
You may be ignoring the differences in the antennas. AM may have used a
ferrite loop, while FM may have been a whip. (We don't know because you
provide no details.)

Could one antenna be responding the magnetic component of the signal
more than the other? (We don't know because you provide no details.)

Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?
Type of materials, type of antenna, relative dimension may all play a
factor. You need to determine all of the effects that enter into the
situation and not focus on one or two.

Where has my intuition gone wrong in opposing the books?
Probably because you don't pay attention to the details and are relying
upon an understanding of the topic that is not correct.

Thanks for your response.
The article only gave me the given facts for the experiment and
nothing more.

If it is this article,http://www.fas.harvard.edu/~scidemos...sm/SkinDepth/S...
Then more was given.

It was an experiment in skin depth.
AM was significantly attenuated, too.
It specified the frequencies used and the associated skin depth.
The radio is also specified.

Your statement is correct

Using an extremely cheap radio as a measurement tool is not sound
technically.
Could be but that is what they used.



Yes my concepts on radiation are in opposition to the
norm so I am using the facts presented as a way of destructing or
confirming my perceptions.
When I read up on Faraday shields the concept of "particles"
predominates as opposed to "waves" without exception and I am trying
to make some sense of these differences when considering propagation.

Perhaps it is a problem with how you do searches. *On this pagehttp://en.wikipedia.org/wiki/Faraday_cage
There is no mention of particles as the means of transport to the
shield. Electrons are mentioned as they are part of the cage and respond
to applied fields.
Yes they clearly state electrons which is a particle. It is extremely
small and of minimul mass which is why Einstein states that the speed
of light is a maximum.
The article you point to shows charges or fields which must be carried
by something like particles as proven in other theories such as
Quantum theory.
Fields and waves book by Ramo etc constantly lean on boundary laws
thru out there book and boundary laws clearly state the relationship
of static particles to equations relative to radiation.
If we are to refer to waves then accelleration demands mass so we need
a connection between waves and mass.
Assuming it is a wave that impinges on a Faraday cage we then have to
determine what half a charge comes about so that the charge cancels
and thus reverts to a time varying current. Again another puzzle!
Anyway the article that you point to shows a point charge which is
certainly not a wave which would be represented by a line of the
length used in top band.
As far as penetration goes the mass involved is always of the same
mass and ikt is only the charge that varies in frequency as shown by
the radius of spin in helical form of the charge.Thus again we have to
find a connection between wavelength and charge.Another obstical....
If you can point out why one cannot use boundary rules so that
particles are recognised as the carriers of charge the same as with
Quantum theory I would be very gratified. None of the group excepting
newcomers such as your self has provided proof of the inelligability
of my approach so I am forced to explore other facets
of radiation to determine why my aproach is in error.
I apologise for not being clear in the subject that creats problems
for newcomers such as yourself but to re iterate the discussion which
has been going on for years would be quite a hardship. However if as
a newcomer you can supply why static particles cannot be associated
with propergation you would be doing something different to the group
that are relying on zero facts and replacing it with insult and spam.
Thanks for responding in a sensible way .I would like to point out in
addition that existing antenna programs with optimizer based on
Maxwells equations rely very heavily on the maintenance of equilibrium
which is the foundation of my aproach which includes particles and
certainly not waves.
If we are going to throw out such programs we surely must know why
before we take such a step when the presence of particles appear to be
in the majority of aproaches.
Best regards
Art Unwin.......KB9MZ.....xg






With respect to receive of the radio. Since the foil is flat and
without perforation it should be sensitive to everything thrown at it.

But the experiment in question is about skin depth which does vary with
frequency.

Unless, of course, you are talking about some other Harvard article, but
we only have to guess, because you still don't identify it.

How do you expect us to know what you are really talking about?
I am fully aware that I am not clear with my questions but I have to
live with that.
The point is that I am still trying to find out why the group does not
accept the extension of a static field in equilibrium cannot be
connected to Maxwells equations when adding a time varying field a
train of thought covered by boundary rules that are used in many
places.
If we accept the above then we have agreement with

Art Unwin wrote:


Yes my concepts on radiation are in opposition to the
norm so I am using the facts presented as a way of destructing or
confirming my perceptions.
When I read up on Faraday shields the concept of "particles"
predominates as opposed to "waves" without exception and I am trying
to make some sense of these differences when considering propagation.
Perhaps it is a problem with how you do searches. On this pagehttp://en.wikipedia.org/wiki/Faraday_cage
There is no mention of particles as the means of transport to the
shield. Electrons are mentioned as they are part of the cage and respond
to applied fields.
Yes they clearly state electrons which is a particle.

But the electron is NOT how the signal gets to the shield. You need to
read more carefully.


It is extremely
small and of minimul mass which is why Einstein states that the speed
of light is a maximum.
The article you point to shows charges or fields which must be carried
by something like particles as proven in other theories such as
Quantum theory.
Fields and waves book by Ramo etc constantly lean on boundary laws
thru out there book and boundary laws clearly state the relationship
of static particles to equations relative to radiation.
If we are to refer to waves then accelleration demands mass so we need
a connection between waves and mass.

Try thinking in terms of fields and charges.


Assuming it is a wave that impinges on a Faraday cage we then have to
determine what half a charge comes about so that the charge cancels
and thus reverts to a time varying current. Again another puzzle!

A puzzle because you apply your misconceptions BEFORE first
understanding what is there.


Anyway the article that you point to shows a point charge which is
certainly not a wave which would be represented by a line of the
length used in top band.

Only because you interpret it that way. The article does not mention
point charge as causing the behavior, externally applied fields are
mentioned.

As far as penetration goes the mass involved is always of the same
mass and ikt is only the charge that varies in frequency as shown by
the radius of spin in helical form of the charge.Thus again we have to
find a connection between wavelength and charge.Another obstical....


If you can point out why one cannot use boundary rules so that
particles are recognised as the carriers of charge the same as with
Quantum theory I would be very gratified.

Gauss' laws refer to flux and do not require carriers of charge to exist.

None of the group excepting
newcomers such as your self has provided proof of the inelligability
of my approach so I am forced to explore other facets
of radiation to determine why my aproach is in error.

A lot of that has to do with your inability to communicate adequately.

I apologise for not being clear in the subject that creats problems
for newcomers such as yourself but to re iterate the discussion which
has been going on for years would be quite a hardship. However if as
a newcomer you can supply why static particles cannot be associated
with propergation you would be doing something different to the group
that are relying on zero facts and replacing it with insult and spam.

If you are trying to present a new concept, then it is up to you to show
why, and that, it is right. Do that in a clear convincing way, with the
appropriate math, and you might foster a worthwhile discussion.

The wrong way to do this is throw a half-baked idea out and expect
others to accept it. You'll never prove a point that way.


Thanks for responding in a sensible way .


I would like to point out in
addition that existing antenna programs with optimizer based on
Maxwells equations rely very heavily on the maintenance of equilibrium
which is the foundation of my aproach which includes particles and
certainly not waves.

Which of these antenna programs have you analyzed to the level to make
this statement? Have you looked at the source code of the programs?

If we are going to throw out such programs we surely must know why
before we take such a step when the presence of particles appear to be
in the majority of aproaches.

Why throw out the programs? Using waves is perfectly correct and
adequate for them.

Waves provide an adequate model for propagation. Particles may be
adequate at the quantum level. Both are ways to describe something.
Neither may adequately describe thing in all cases. They are models for
what happens. As long as the models are applied appropriately, there is
no problem. Applying a model inappropriately is bound to cause problems.



Best regards
Art Unwin.......KB9MZ.....xg





snip


How do you expect us to know what you are really talking about?
I am fully aware that I am not clear with my questions but I have to
live with that.
The point is that I am still trying to find out why the group does not
accept the extension of a static field in equilibrium cannot be
connected to Maxwells equations when adding a time varying field a
train of thought covered by boundary rules that are used in many
places.

That is solely because YOU can't describe your concepts adequately.
Putting "+t" on both sides of an equation does not necessarily lead to
anything meaningful. IF you were to describe your thoughts adequately,
perhaps someone would show you where you make errors.


If we accept the above then we have agreement with

On Mar 21, 4:59*pm, joe wrote:


If it is this article,http://www.fas.harvard.edu/~scidemos...sm/SkinDepth/S...
Then more was given.

It was an experiment in skin depth.

Strictly speaking the page describes a demonstration from page 321 of
this book:

G. Bekefi and A. H. Barrett, Electromagnetic Vibrations, Waves and
Radiation, (MIT Press, 1977)

http://www.amazon.com/Electromagneti.../dp/0262520478

http://mitpress.mit.edu/catalog/item...d=7576&ttype=2

A reviewer comments, "MITonline offers the course based on this book
for free. The course is great! This book is a less engaging, but a
more comprehensive version of A.P. French's original text for the
course. There are many gems in the book, such as insights into
microwave oven fundamentals, that are not present in basic texts.
Beware the softcover binding, it needs a gentle hand. "

http://www.amazon.com/Electromagneti...owViewpoints=1