"Richard Harrison" wrote in message
...
Art wrote:
"But nobody will question the fact that all computer programs support my
addition to Gaussian law to those of maxwell."

That`s an I dare you.

Gauss's law IS one of Maxwell's equations. In fact both Ramo Whinnery and
Van Duzer's "Fields and Waves in Communications Electronics" (pg 237 in the
1st edition) and Jackson's "Classical Electrodynamics" (compare pg 2 and 33
in the 2nd edition). So every time art makes that assertion he is just
showing his ignorance of the facts.

On 11 Nov, 05:19, "Richard Fry" wrote:
"art" wrote

It has been stated on this antenna newsgroup that with
short antennas the current goes up the radiator and then turns back
and goes down. If this is so then it must be radiating all the time,
yes? If a radiator is radiating all the time then the efficiency is the
same as a full leght antenna. Yes? This does not conform with
reality Right?

Wrong, as regards your "reality." Using the classic definition of
efficiency, an antenna of ANY length (including a point source) will radiate
nearly 100% of the power it accepts from the r-f source driving it.

The radiation patterns of those antennas will vary. Some will radiate more
relative field in some directions and less in some directions than others
will. But, disregarding dielectric and conductor I^2R losses, ALL antennas
radiate ALL of the power they accept from their driving source (ie, their
efficiencies are equal).

So is it possible that the circuit (current) returns along
the path down the center of the radiator...

No, it's not possible. No matter the direction of flow along a solid
conductor, alternating current tends to travel on/near its outer surface.
This is due to the greater number of enclosed lines of magnetic flux
generated by current flowing at/near its center, which increases the
inductive reactance of the conductor in those areas. The result is a
redistribution of the current to the parts of the conductor cross-section
having the least reactance, ie, on and near its outer surface. Read
Terman's RADIO ENGINEERS' HANDBOOK, 1943 edition, pp 30-31 for more on this
(or many other sources).

IF it was possible then radiation figures accepted by hams
would coincide with respect to short antennas. Yes?.
Then why do all the "experts" reject the notion of the circuit
continueing down the center of the radiator?

Because it doesn't do that.

RF

To say that an AC current will not flow in copper unless it has clear
axis
access to the copper surface is balderdash. Cover the copper with an
insulator
with any thickness that you desire for safety incase you are in error
and then drill
into the center of the copper. Without a safe guard you will die!
What provides resistance on the outside als skin depth can by the
reverse contain current flow to the inside. You like many use the word
"tends"
with respect to external current flow. The word "tends" does not
make the current passage an undeniable fact. Yet you have hung
your hat on that premise. I repeat...balderdash
Art

I repeat...balderdash
Art


Artsy,
Finally you summarized your "writings" and your repeating of it.
Balderdash trophy of the year goes to Art da ex G man.

Have you considered fishing or other activities?

bada BUm

"art"
What provides resistance on the outside als skin depth can
by the reverse contain current flow to the inside.

This is another of your beliefs that not supported either by theory
or practice.

The word "tends" does not make the current passage
an undeniable fact.

I wrote "tends" because there is no discrete boundary near the outer surface
of a conductor where ALL of the alternating current flowing near its surface
is confined. But almost all of that current flows within several "skin
depths."

The 1.8 MHz skin depth in a round, copper conductor is about 0.06 mm, which
means that a tubular conductor with a wall thickness at least 3 times that
can be used in place of a solid conductor of the same outer diameter, with
no practical change in performance at that frequency.

RF

Richard Fry wrote:
"Read Terman`s RADIO ENGINEERS` HANDBOOK, 1943 edition, pp 30-31 for
more on this (or many other sources)."

Amen. Terman doesn`t say different things in different places. He is
consistent. In Terman`s 1955 edition of "Electronic and Radio
Engineering" he writes on page 21:
"It is to be noted that some of this (magnetic) flux exists within the
conductor and therefore links with, i.e., encircles, current near the
center of the conductor while not linking current flowing near the
surface. The result is that inductance of the central part of the
conductor is greater than the part of the conductor nesr the surface;
this is because of the greater number of flux linkages existing in the
central region.

That`s why we have skin effect and why hollow pipes carry HF current as
effectively as solid rods with the same external surface area in most
cases. The pipe`s interior doesn`t carry current unless its diameter is
at least 1/2 wavelength (its cutoff as a waveguide).

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Richard Fry wrote:
"Read Terman`s RADIO ENGINEERS` HANDBOOK, 1943 edition, pp 30-31 for
more on this (or many other sources)."

Amen. Terman doesn`t say different things in different places. He is
consistent. In Terman`s 1955 edition of "Electronic and Radio
Engineering" he writes on page 21: "It is to be noted that some of this
(magnetic) flux exists within the conductor and therefore links with,
i.e., encircles, current near the center of the conductor while not
linking current flowing near the surface. The result is that inductance
of the central part of the conductor is greater than the part of the
conductor nesr the surface; this is because of the greater number of
flux linkages existing in the central region.


What Terman says is true, for the particular example that he chooses.
But it may leave an incorrect impression that the conductor needs to be
completely encircled by flux linkages.

In fact the skin effect will develop on the surface of any conducting
material of any shape, wherever there is RF current flowing.

Here is a link to a detailed mathematical proof, from 'Transmission
Lines for Communications' by C W Davidson (Macmillan Press, 1978, ISBN 0
333 32738 1): http://www.ifwtech.co.uk/g3sek/misc/skin.htm

Davidson's analysis starts with the most general assumption possible:
that RF current is flowing over any small patch of a conductor's
surface. No assumption is required about the reason for the RF current
to be present, only that it is. Likewise no assumption is required about
the cross-section of the conductor, only that it has an exposed surface
(and by implication, that there are no constraints due to a small radius
or insufficient depth). Davidson then derives all the usual equations
for the skin effect. The only drawback of this derivation is that it is
highly mathematical, and difficult to put into words; but it's still
physically correct.

To repeat, I am not saying that Terman's explanation is incorrect; only
that the skin effect is a far more general phenomenon than his
particular examples imply.

This is important because, by taking the existence of the skin effect as
a guaranteed starting-point, the explanations for the behaviour of
coaxial cables, 'bazooka' baluns, 'shielded' loops and many other
devices will all fall neatly into place.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On 11 Nov, 14:18, Ian White GM3SEK wrote:
Richard Harrison wrote:
Richard Fry wrote:
"Read Terman`s RADIO ENGINEERS` HANDBOOK, 1943 edition, pp 30-31 for
more on this (or many other sources)."

Amen. Terman doesn`t say different things in different places. He is
consistent. In Terman`s 1955 edition of "Electronic and Radio
Engineering" he writes on page 21: "It is to be noted that some of this
(magnetic) flux exists within the conductor and therefore links with,
i.e., encircles, current near the center of the conductor while not
linking current flowing near the surface. The result is that inductance
of the central part of the conductor is greater than the part of the
conductor nesr the surface; this is because of the greater number of
flux linkages existing in the central region.

What Terman says is true, for the particular example that he chooses.
But it may leave an incorrect impression that the conductor needs to be
completely encircled by flux linkages.

In fact the skin effect will develop on the surface of any conducting
material of any shape, wherever there is RF current flowing.

Here is a link to a detailed mathematical proof, from 'Transmission
Lines for Communications' by C W Davidson (Macmillan Press, 1978, ISBN 0
333 32738 1):http://www.ifwtech.co.uk/g3sek/misc/skin.htm

Davidson's analysis starts with the most general assumption possible:
that RF current is flowing over any small patch of a conductor's
surface. No assumption is required about the reason for the RF current
to be present, only that it is. Likewise no assumption is required about
the cross-section of the conductor, only that it has an exposed surface
(and by implication, that there are no constraints due to a small radius
or insufficient depth). Davidson then derives all the usual equations
for the skin effect. The only drawback of this derivation is that it is
highly mathematical, and difficult to put into words; but it's still
physically correct.

To repeat, I am not saying that Terman's explanation is incorrect; only
that the skin effect is a far more general phenomenon than his
particular examples imply.

This is important because, by taking the existence of the skin effect as
a guaranteed starting-point, the explanations for the behaviour of
coaxial cables,

Ian, I have no disagreement to your reply above other than you are
being to king in your response
I personaly would have put more emphasis on what you stated with
respect
to RF traveling along a path that has no external surface .With
emphasising
where many have about RF travel without which one CANNOT understand
coaxial cables or braid The inside of braid on a coax CAN and DOES
carry
RF current but it does NOT radiate, because it does NOT have an
exposed surface
other than a dielectric interface. The outside surface can and DOES
radiate if a
RF current flows on the outside of the braid. I would also add that
copper/braid
itself does not turn into a dielectric or contain a diode thus it
also WILL
also pass a RF current at its centre but of course does NOT radiate.
This very fact was refuted by popular vote on this newsgroup where
poll
standings always overule science. So yes, without true understandings
errors
are sure to congregate and eventually will create a "fact".
Art KB9MZ...xg





'bazooka' baluns, 'shielded' loops and many other
devices will all fall neatly into place.

--

73 fromIanGM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek

"art" wrote
I would also add that copper/braid itself does not turn into a dielectric
or contain a diode thus it also WILL also pass a RF current at its
centre...
____________

art... so by your post you reject the theory and experience of physical
science?

RF

"art" wrote
I would also add that copper/braid itself does not turn into
a dielectric or contain a diode thus it also WILL also
pass a RF current at its centre but of course does NOT radiate.
_____________

art, you really need to buy and read Terman's RADIO ENGINEERS' HANDBOOK or
similar source, instead of relying on your intuition. Terman provides the
following equation for the r-f attenuation of air-insulated, copper coaxial
transmission line:

a = 0.00362 SQRT(f)*(1+ D/d) / D*log(D/d) dB per 1,000 feet

where f = frequency in MHz, D = inner diameter of outer conductor, d =
outer diameter of inner conductor.

Note that the attenuation is the same whether the inner conductor is solid
or tubular. This is the result of "skin effect," which for r-f frequencies
1.8 MHz and higher confines the r-f current on the inner conductor from its
outer surface to a depth of less than 0.18 mm.

RF