On Jan 13, 2:44*pm, "Dave" wrote:
"Art Unwin" wrote in message

...



What diametric ratio must a fractional wave length radiator be to
allow contrary current flow thru it's center. ?
Diameter / wavelength = 1.0, * *0.5, *0.1. * * 0.001, * * *0.0001,
0.00001,...?
Regards
Art

infinite

David
Just for the record, skin depth is proportional to frequency
Thus for very hight frequency the skin depth is exceedingly small
This tells us that the effect of eddy current with respect to the
diameter
is NOT infinite but limit dependent on the applied frequency.
I am not extending this thread, but on rereading it is obvious to me
that
there is a boundary within which a current could possibly travel. But
since the current is zero
at the end I am more inclined to think that applied current is
balanced at the source so that zero current is inevitable at the end
of the radiator, How this is done appears to be something like
a pump action which with laminar flow creates cavitation resistances
in line with Bernoulis theorems.IE velocity changes that are
dependent on distributed load losses of the radiator
The end of this thread !
Art
Art

Art wrote:
"David just for the record, skin depth is proportional to
frequency----."

Not exactly. Skin depth is inversely proportional to the square root of
the frequency.

For example at 1 Hz the skin depth is about 2.6 in. in copper. At 10 Hz.
it is about 0.826 in. and at 100 Hz the depth is about 0.260 in. and at
1000 Hz the depth is 0.0826 in. etc.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Art wrote:
"David just for the record, skin depth is proportional to
frequency----."

Not exactly. Skin depth is inversely proportional to the square root of
the frequency.

For example at 1 Hz the skin depth is about 2.6 in. in copper. At 10 Hz.
it is about 0.826 in. and at 100 Hz the depth is about 0.260 in. and at
1000 Hz the depth is 0.0826 in. etc.

Best regards, Richard Harrison, KB5WZI


don't confuse him with the facts!

Richard Harrison wrote:
Art wrote:
"David just for the record, skin depth is proportional to
frequency----."

Not exactly. Skin depth is inversely proportional to the square root of
the frequency.

For example at 1 Hz the skin depth is about 2.6 in. in copper. At 10 Hz.
it is about 0.826 in. and at 100 Hz the depth is about 0.260 in. and at
1000 Hz the depth is 0.0826 in. etc.

Best regards, Richard Harrison, KB5WZI

Actually, skin depth is inversely proportional to the square root of
frequency only in a good conductor like copper. Some common materials
like dirt are fairly good conductors at low frequencies but behave more
like dielectrics at higher frequencies. And skin depth doesn't change
with frequency in a dielectric. For "average" ground (0.005 S/m
conductivity, permittivity of 13), the transition between conductor
behavior and dielectric behavior is at about 6.9 MHz, in the middle of
the HF range. Well below that frequency, the skin depth changes in
inverse proportion to the square root of the frequency; above it, the
skin depth stays nearly constant. For "average" ground:

Freq MHz Skin Depth m
0.01 71.2
0.5 10.4
1 7.6
2 5.8
4 4.7
6.9 4.2
8 4.1
16 3.9
100 3.8

Roy Lewallen, W7EL

On Jan 23, 4:43*pm, (Richard Harrison)
wrote:
Art wrote:

"David just for the record, skin depth is proportional to
frequency----."

Not exactly. Skin depth is inversely proportional to the square root of
the frequency.

For example at 1 Hz the skin depth is about 2.6 in. in copper. At 10 Hz.
it is about 0.826 in. and at 100 Hz the depth is about 0.260 in. and at
1000 Hz the depth is 0.0826 in. etc.

Best regards, Richard Harrison, KB5WZI

Yes, I should have used "varied" instead of "proportional" But the
essence of the posting is still correct namely, it is false to state
that the skin effect always penetrate thro out the conductor
as is the statement that a current cannot travel thru the center of a
conductor where the material is devoid of eddy currents but enclosedn
by a eddy current shield
This is not to say that with a applied AC current such a route is
chosen as I previously thought
Art

"Art Unwin" wrote in message
...
On Jan 23, 4:43 pm, (Richard Harrison)
wrote:
For example at 1 Hz the skin depth is about 2.6 in. in copper. At 10 Hz.
it is about 0.826 in. and at 100 Hz the depth is about 0.260 in. and at
1000 Hz the depth is 0.0826 in. etc.
Yes, I should have used "varied" instead of "proportional" But the
essence of the posting is still correct namely, it is false to state
that the skin effect always penetrate thro out the conductor
as is the statement that a current cannot travel thru the center of a
conductor where the material is devoid of eddy currents but enclosedn
by a eddy current shield

of course current travels through the center of the conductor, just not the
way you had thought.

On Jan 13, 2:44*pm, "Dave" wrote:
"Art Unwin" wrote in message

...



What diametric ratio must a fractional wave length radiator be to
allow contrary current flow thru it's center. ?
Diameter / wavelength = 1.0, * *0.5, *0.1. * * 0.001, * * *0.0001,
0.00001,...?
Regards

Art





infinite

Is that your final answer
or is your last posting the final answer ?
The clock starts NOW

"Art Unwin" wrote in message
...
On Jan 13, 2:44 pm, "Dave" wrote:

infinite

Is that your final answer
or is your last posting the final answer ?
The clock starts NOW

that is the same as my last posting... and is still correct!

On Jan 25, 12:59*pm, "Dave" wrote:
"Art Unwin" wrote in message

...
On Jan 13, 2:44 pm, "Dave" wrote:

infinite
Is that your final answer

*or is your last posting the final answer ?

The clock starts NOW

that is the same as my last posting... and is still correct!

Going back to the physics books which takes time. Skin depth formula
is derived from the assumption that the radiator is a perfect
conductor where the depth is "finite". A non perfect conductor is some
what different.
Art

On Jan 23, 5:05*pm, "Dave" wrote:
"Richard Harrison" wrote in message

...

Art wrote:
"David just for the record, skin depth is proportional to
frequency----."

Not exactly. Skin depth is inversely proportional to the square root of
the frequency.

For example at 1 Hz the skin depth is about 2.6 in. in copper. At 10 Hz..
it is about 0.826 in. and at 100 Hz the depth is about 0.260 in. and at
1000 Hz the depth is 0.0826 in. etc.

Best regards, Richard Harrison, KB5WZI

don't confuse him with the facts!

My facts were correct as stated. Richard stated the "exact"
proportions
which is really nit picking. Physics books say it is "proportional"
which states that it is frequency change what affects skin depth. It
is stated exactly that way in the book
that Richard has just obtained and quoted
Art