RadioBanter - Contrary current flow within a radiator

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Contrary current flow within a radiator

Warning - dilletente alert! Maybe even worth an embarrassing dolt cringe

This question may have been asked before, but is there a physical
experiment that is good for verifying skin effect?

Initially, It seemed pretty straightforward, but giving some thought to
the matter indicates it "ain't necessarily so".

I'm assuming that any thick conductor is going to have "skin" to any
where I can put a sensor, so even if I drilled an internal sensor, the
drill tunnel would form a part of the skin.

Giving that some thought, is it possible to make say a ribbed conductor
that resembled a tubular heat sink, would this device allow for more
current flow because of the greater amount of skin exposed compared to a
solid tube?

Just a little thought experiment.

- 73 de Mike N3LI -

Contrary current flow within a radiator

On Jan 30, 10:00*am, Michael Coslo wrote:
Warning - dilletente alert! Maybe even worth an embarrassing dolt cringe

This question may have been asked before, but is there a physical
experiment that is good for verifying skin effect?

Initially, It seemed pretty straightforward, but giving some thought to
the matter indicates *it "ain't necessarily so".

I'm assuming that any thick conductor is going to have "skin" to any
where I can put a sensor, so even if I drilled an internal sensor, the
drill tunnel would form a part of the skin.

Giving that some thought, is it possible to make say a ribbed conductor
that resembled a tubular heat sink, would this device allow for more
current flow because of the greater amount of skin exposed compared to a
solid tube?

Just a little thought experiment.

* * * * - 73 de Mike N3LI -

All charges will congregate along the peaks of the ribs so I can't see
how a greater
area is generated for utelization !
Regards
Art

Contrary current flow within a radiator

Michael Coslo wrote:
Just a little thought experiment.

Something else that I have wondered about:
Given a threaded rod with about double the surface
area of a piece of tubing, does the VF decrease?
Can a threaded rod be used to decrease the length
of a resonant vertical?
--
73, Cecil http://www.w5dxp.com

Contrary current flow within a radiator

Art Unwin wrote:
On Jan 30, 10:00 am, Michael Coslo wrote:
Warning - dilletente alert! Maybe even worth an embarrassing dolt cringe

This question may have been asked before, but is there a physical
experiment that is good for verifying skin effect?

Initially, It seemed pretty straightforward, but giving some thought to
the matter indicates it "ain't necessarily so".

I'm assuming that any thick conductor is going to have "skin" to any
where I can put a sensor, so even if I drilled an internal sensor, the
drill tunnel would form a part of the skin.

Giving that some thought, is it possible to make say a ribbed conductor
that resembled a tubular heat sink, would this device allow for more
current flow because of the greater amount of skin exposed compared to a
solid tube?

Just a little thought experiment.

- 73 de Mike N3LI -

All charges will congregate along the peaks of the ribs so I can't see
how a greater area is generated for utelization !

Is what you are saying then that it is not truly a "skin" effect, which
would have the maximum current riding near the surface, but rather some
sort of effect that has that maximum current getting as far away from
the center of the conductor? In other words the vertical component of
the ribbing would have current flow as if it were at that distance from
the surface of a solid conductor.

Not trying to change th eworld here, just trying to get my head around
the issue. Lot's of things have misnomers as a name.

- 73 de Mike N3LI -

Contrary current flow within a radiator

"Cecil Moore" wrote
Something else that I have wondered about:
Given a threaded rod with about double the surface
area of a piece of tubing, does the VF decrease?
__________________

The velocity of propagation of Andrew HJ8-50B, 3" OD, air-dielectric
Heliax® is 0.933c.

Both the inner and outer conductors of that coaxial cable are heavily
corrugated, so using threaded rod instead of smooth tubing may not
matter much to v.p.

RF

Contrary current flow within a radiator

On Jan 30, 12:23*pm, Michael Coslo wrote:
Art Unwin wrote:
On Jan 30, 10:00 am, Michael Coslo wrote:
Warning - dilletente alert! Maybe even worth an embarrassing dolt cringe

This question may have been asked before, but is there a physical
experiment that is good for verifying skin effect?

Initially, It seemed pretty straightforward, but giving some thought to
the matter indicates *it "ain't necessarily so".

I'm assuming that any thick conductor is going to have "skin" to any
where I can put a sensor, so even if I drilled an internal sensor, the
drill tunnel would form a part of the skin.

Giving that some thought, is it possible to make say a ribbed conductor
that resembled a tubular heat sink, would this device allow for more
current flow because of the greater amount of skin exposed compared to a
solid tube?

Just a little thought experiment.

* * * * - 73 de Mike N3LI -

All charges will congregate along the peaks of the ribs so I can't see
how a greater area is generated for utelization !

Is what you are saying then that it is not truly a "skin" effect, which
would have the maximum current riding near the surface, but rather some
sort of effect that has that maximum current getting as far away from
the center of the conductor? In other words the vertical component of
the ribbing would have current flow as if it were at that distance from
the surface of a solid conductor.

Not trying to change th eworld here, just trying to get my head around
the issue. Lot's of things have misnomers as a name.

* * * * - 73 de Mike N3LI -

What I am saying is that the ribs could prevent the flow of eddy
currents which operate as a completed circular circuit. This is how
the detection of fissures in material is found by non destructive
means. If eddy current is not present then radiation cannot occur,
thus all is not known about radiation !
Frankly I would like to know of another situation where energy flows
in the absence of a completed circuit which would provide more insight
of the circuitry of a fractional wavelength antenna, as the existing
explanation appears to be a bit to glib
Regards
Art

Contrary current flow within a radiator

"Art Unwin" wrote in message
...
On Jan 30, 12:23 pm, Michael Coslo wrote:
If eddy current is not present then radiation cannot occur,
thus all is not known about radiation !

eddy currents needed for radiation, now that is a good one. do the eddy
currents do the levitating of the magical diamagnetic neutrinos?

Frankly I would like to know of another situation where energy flows
in the absence of a completed circuit which would provide more insight
of the circuitry of a fractional wavelength antenna, as the existing
explanation appears to be a bit to glib

lets see:
1. energy flows from a flame, but not back into it
2. electromagnetic waves carry energy but don't need a complete circuit
3. sound waves carry energy but don't make a complete circuit
4. water waves carry energy but don't make a complete circuit
5. magical diamagnetic levitating neutrinos flow out from the sun and carry
energy but never go back... actually a whole bunch of charged and uncharged
particles flow out from the sun in the solar wind and never go back.

Contrary current flow within a radiator

In article ,
Michael Coslo wrote:

Warning - dilletente alert! Maybe even worth an embarrassing dolt cringe

This question may have been asked before, but is there a physical
experiment that is good for verifying skin effect?

Here's one, fairly simple in principle although I imagine it would
require care in the implementation in order to prevent measurement
error due to other effects.

[1] Construct a balanced transmission line using a pair of solid
cylindrical conductors, having a known characteristic impedance.

[2] Terminate this transmission line with a dummy load - a pure
resistance which matches the line's characteristic impedance.

[3] Drive this transmission line via a suitable RF signal generator or
source, having a known (or carefully measured) output power into
the line's impedance.

[4] Measure the RF power delivered into the line, and the RF power
being dissipated by the dummy load. This could be done via an RF
millivoltmeter, for instance.

[5] Calculate the amount of power being lost in the transmission line.

[6] Replace the solid cylindrical conductors in the transmission line
with tubular conductors of the exact same material - hollow in the
center, but with a wall width of at least 5 skin depths at the
frequency you are using. Make sure that the outer diameter, and
spacing of the tubular conductors matches the OD and spacing of the
solid-conductor version of the line.

[7] Drive this new line, and repeat the measurements and calculate the
loss in this line.

[8] Calculate the cross-sectional area of the solid conductor, and of
the actual conductive portion of the hollow tubular conductor, and
then the ratio between the two.

[9] Calculate the ratio between the power losses in the two types of
transmission line.

[10] Compare these two ratios.

You could in principle do a similar test by making two dipoles out of
solid and tubular elements, driving them with identical signals, and
measuring the field strength. I suspect this test would be harder to
do reliabily.

In either case, what you ought to be able to demonstrate, is that two
transmission lines (one solid-conductor , the other hollow-conductor,
but otherwise identical) which are long enough to exhibit substantial
losses (e.g. 3 dB or 50% of the input power) would have near-identical
losses, even though the amount of conductive material in the
hollow-conductor line is less than 10% that of that in the
solid-conductor line.

This would be good evidence that only the outer perimeter of the
solid conductors was carrying a significant amount of current, since
"removing the center" doesn't decrease the loss.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Contrary current flow within a radiator

Michael Coslo wrote:
Warning - dilletente alert! Maybe even worth an embarrassing dolt cringe

This question may have been asked before, but is there a physical
experiment that is good for verifying skin effect?

Initially, It seemed pretty straightforward, but giving some thought to
the matter indicates it "ain't necessarily so".

I'm assuming that any thick conductor is going to have "skin" to any
where I can put a sensor, so even if I drilled an internal sensor, the
drill tunnel would form a part of the skin.

Giving that some thought, is it possible to make say a ribbed conductor
that resembled a tubular heat sink, would this device allow for more
current flow because of the greater amount of skin exposed compared to a
solid tube?

Just a little thought experiment.

- 73 de Mike N3LI -

An experiment to verify skin effect:

Make or obtain a self-contained RF signal source. Put it into a
completely sealed conductive box -- PC board material soldered together
with no gaps would be fine. Then try to detect any signal outside the
box. If the RF current could penetrate the conductive material, that is,
if there were no skin effect, you'll be able to detect the signal.

Here's another: http://w8ji.com/skindepth.htm.

The problem with your ribbed conductor is the same general thing that
causes skin effect -- currents cause fields which repel other currents.
The result would be more current on the tips of the ribs and less
current in the valleys.

You can make a pretty good surface current sniffer by winding a bunch of
turns of wire on 1/2 of a ferrite core, and connecting it to a scope or
other detector. Put the two core piece ends on the surface, so it looks
like an upside down U when on a flat horizontal conductor.

Roy Lewallen, W7EL