Richard Harrison wrote:
Roy Lewallen, W7EL wrote:
"Am I mistaken, but is this not a clear statement that a copper or
aluminum shield will block magnetic flux along with explanation of why
it happens?"

Yes. And now the rest of the story which I`ve already posted several
times.

At the bottom of page 38 in Terman`s 1955 edition;
"It is possible to shield slectrostatic flux WITHOUT simultaneously
affecting the magnetic field by surrounding the space to be shielded
with a conducting cage that is made in such a way as to provide NO
low-resistance path for the flow of eddy currents, while at the same
time offering a metallic terminal upon which electrostatic flux can
terminate."

I invited readers to look at page 43 in the same book whe
"A grid of wires such as shown in the accompanying figure will provide
electrostatic shielding WITHOUT magnetic shielding---."

I also said that similar grids (metal picket fences) were used in AM
broadcast stations I`d worked in to eliminate capacitive coupling to the
antennas which would otherwise favor harmonics of the broadcast
frequency.

W8JI is yet desiring to drive a stake in the heart of the "myth" that
E&H fields are separable if even for an instant. He is dead wrong.

Certainly the E or H field can disappear for part of a cycle. This
happens routinely in a transmission line or in free space, as the energy
is swapped back and forth between the two components. Tom has never said
this is not so. And for whole cycles you can locally change the ratio of
E/H, but you cannot separate them. Maxwell's equations show this. And if
you do change the ratio of E/H, the normal free space ratio is restored
within a small distance.

The magnetic field alone does quite well in transferring all the wave`s
energy through a special transformer which completely bars the electric
field. Of course, current in the transformer`s secondary produces a
voltage and the E-field is immediately restored.

Yes. And does this restored E field not occupy the space between the
winding and the wire grid? If so, how can you tell that the grid has
"stopped" the E field if it exists on both sides of the grid?

This is not witchcraft. In free-space the electric field and the
magnetic field are repeatedly exchanging all the energy back and forth.
It keeps the wave going.

With this I totally agree. That explanation is related to why you can't
simply remove one component or the other.

At a short or open on a transmission line energy is not lost. It is
merely transferred for an instant into the surviving field.

Similarly, all the energy can be transferred through the electric field
with zero magnetic coupling. Imagine two separately shielded coils. Now,
use a coupling capacitor to transfer the energy from one coil to the
other. Voila! E-field transfer with zero magnetic coupling. It`s no
myth. It`s a fact.

It's a myth that there's no magnetic field in the space between a
capacitor's plates.

Roy Lewallen, W7EL

Roy, W7EL wrote:
"It`s a myth that there`s no magnetic field in the space between a
capacitor`s plates."

Maxwell`s great speculation was that "displacement current", as between
a capacitor`s plates, produced magnetic flux as does conduction current.
His speculation is now proved.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Cecil, W5DXP wrote:
"Does a 60 Hz magnetic field travel virtually unimpeded through a
coaxial shield?"

Surely many readers have toiled with shielded audio cables similar to
coax and they know the answer is yes, if the shield is broken (this
often happens at the ends of the cable).

Best regards, Richard Harrison, KB5WZI


The skin depth of copper at 60 hertz is supposed to be 8.53mm. That's
too thick to make a practical shield. No wonder they're having problems.
73,
Tom Donaly, KA6RUH

Richard Harrison wrote:
Roy, W7EL wrote:
"It`s a myth that there`s no magnetic field in the space between a
capacitor`s plates."

Maxwell`s great speculation was that "displacement current", as between
a capacitor`s plates, produced magnetic flux as does conduction current.
His speculation is now proved.

Yes. So how does a capacitor between two inductors constitute "E-field
transfer with zero magnetic coupling" as you stated?

Roy Lewallen, W7EL

Richard Harrison wrote:

Roy Lewallen, W7EL wrote:
"Am I mistaken, but is this not a clear statement that a copper or
aluminum shield will block magnetic flux along with explanation of why
it happens?"

Yes. And now the rest of the story which I`ve already posted several
times.

At the bottom of page 38 in Terman`s 1955 edition;
"It is possible to shield slectrostatic flux WITHOUT simultaneously
affecting the magnetic field by surrounding the space to be shielded
with a conducting cage that is made in such a way as to provide NO
low-resistance path for the flow of eddy currents, while at the same
time offering a metallic terminal upon which electrostatic flux can
terminate."

I invited readers to look at page 43 in the same book whe
"A grid of wires such as shown in the accompanying figure will provide
electrostatic shielding WITHOUT magnetic shielding---."

I also said that similar grids (metal picket fences) were used in AM
broadcast stations I`d worked in to eliminate capacitive coupling to the
antennas which would otherwise favor harmonics of the broadcast
frequency.

W8JI is yet desiring to drive a stake in the heart of the "myth" that
E&H fields are separable if even for an instant. He is dead wrong.

The magnetic field alone does quite well in transferring all the wave`s
energy through a special transformer which completely bars the electric
field. Of course, current in the transformer`s secondary produces a
voltage and the E-field is immediately restored.

This is not witchcraft. In free-space the electric field and the
magnetic field are repeatedly exchanging all the energy back and forth.
It keeps the wave going.

At a short or open on a transmission line energy is not lost. It is
merely transferred for an instant into the surviving field.

Similarly, all the energy can be transferred through the electric field
with zero magnetic coupling. Imagine two separately shielded coils. Now,
use a coupling capacitor to transfer the energy from one coil to the
other. Voila! E-field transfer with zero magnetic coupling. It`s no
myth. It`s a fact.

Best regards, Richard Harrison, KB5WZI


When did you perform this experiment, Richard? (Perfectly shielding two
coils and then coupling them with a capacitor.) And how did you manage
to shield them if, as you seem to think, the magnetic fields are capable
of penetrating the shield?
73,
Tom Donaly, KA6RUH

Roy Lewallen wrote:
It's a myth that there's no magnetic field in the space between a
capacitor's plates.

What quantum particles support that magnetic field?
--
73, Cecil http://www.qsl.net/w5dxp

Tom Donaly wrote:
The skin depth of copper at 60 hertz is supposed to be 8.53mm. That's
too thick to make a practical shield. No wonder they're having problems.

So 60 Hz magnetic fields penetrate shielded coax?
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
om...
Tom Donaly wrote:
The skin depth of copper at 60 hertz is supposed to be 8.53mm. That's
too thick to make a practical shield. No wonder they're having problems.

So 60 Hz magnetic fields penetrate shielded coax?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil, if ever I had the feeling that I was about to answer a loaded
question, this is it, but here goes anyway - "Yes, I believe a 60 Hz
magnetic field impinging on a piece of shielded coax would penetrate
the shield of that coax significantly if the shield were made of a
non-ferrous conductor."

73, Mike W4EF.............................................

Michael Tope wrote:

"Cecil Moore" wrote:
So 60 Hz magnetic fields penetrate shielded coax?

Cecil, if ever I had the feeling that I was about to answer a loaded
question, this is it, but here goes anyway - "Yes, I believe a 60 Hz
magnetic field impinging on a piece of shielded coax would penetrate
the shield of that coax significantly if the shield were made of a
non-ferrous conductor."

It's not a loaded question. I just always assumed that coax
would shield the system from 60 Hz noise and I guess I was
wrong.
--
73, Cecil http://www.qsl.net/w5dxp

"Richard Harrison" wrote

Similarly, all the energy can be transferred through the electric field
with zero magnetic coupling. Imagine two separately shielded coils. Now,
use a coupling capacitor to transfer the energy from one coil to the
other. Voila! E-field transfer with zero magnetic coupling. It`s no
myth. It`s a fact.

Best regards, Richard Harrison, KB5WZI


I wonder how the gurus 'splain the different behavior of vertical vs.
horizontally polarized antennas, where E field determines the way signals
reflect and form the pattern. If E and H fields are so "inseparable" there
should be no difference, right?

They are ignoring behavior of E and H fields within the near field of
antennas and workings of the shield.

Another example of shield's performance was when I had small shielded loop
next to the Beverage. The combination gave better S/N performance and better
signal levels than each of them alone. Again, shield performing shielding
function in the vicinity of near field of both antennas. Loops were tunable
and performing as an antenna, shield was shielding from the near by
interference and providing symmetry. FACTS - verifiable not subject to wild
speculations about current crawling around the edge to inside of tubing, or
antenna inside of electrostatic shield quitting to work as antenna because
of "W8JI shield is antenna teachings".

--
Yuri Blanarovich, K3BU, VE3BMV