Szczepan Bia³ek wrote:


You send me to library. Try use his own words. Christofire do it (in
"Spherical radiation patern"):

God forbid that you should actually do some research! What a terrible
thought!

tom
K0TAR

On Fri, 18 Sep 2009 18:54:25 -0500, tom wrote:

Richard Clark wrote:
On Fri, 18 Sep 2009 19:13:17 +0200, Szczepan Bia?ek
wrote:

All is exactly the same like in the fluids mechanics.

"Exactly" makes it very, very easy to show how an analogy fails:
Describe the laminar flow in terms of
the Reynolds number for

Hmm, I think I'd start with a very long K1FO yagi, say 50 elements.
Maybe even extend one to 100 elements to getting very fine details.
Then we look at the longitoodordinal current along the horizontal
element by element. I'll have to work on it a while though.

What are you thinking?

I am thinking that Stefan by lacking a demonstration of this
employment of his own chosen metaphor displays a vacuum in two subject
areas. As it stands, he stumbles through the nuances of RF. Instead,
he is trying to extrapolate them through a second subject, where, of
course, he tumbles over the nuances of fluidics.

The best we can expect is for him to haul a book to the nearest Xerox
and lean on the copy button to produce a snow job. The deepest
impression he will get of that intellectual experience is a paper cut.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

What are you thinking?

I am thinking that Stefan by lacking a demonstration of this
employment of his own chosen metaphor displays a vacuum in two subject
areas. As it stands, he stumbles through the nuances of RF. Instead,
he is trying to extrapolate them through a second subject, where, of
course, he tumbles over the nuances of fluidics.

The best we can expect is for him to haul a book to the nearest Xerox
and lean on the copy button to produce a snow job. The deepest
impression he will get of that intellectual experience is a paper cut.

73's
Richard Clark, KB7QHC

Very perspective.

tom
K0TAR

"Richard Clark" wrote
...

I won't wait for that obvious failure. This is several steps above
your pay-grade. So, you should really attempt to work on first
principles rather than rummaging in the attic for impressive artifacts
of science.

And what should do Richard Harrison who wrote: "At the open circuited ends
of a resonant antenna there is almost double
the forward voltage but zero total current due to cancellation of the
dorward and reflected currents at the open circuit. At the open circuit
in the wire, all the energy in the wave is transferred to the electric
field. "
S*

"Dave" wrote
...

"Szczepan Bialek" wrote in message

In the Gas Analogy the monopole antena is exactly like the Kundt's tube.

Heaviside did the Hydraulic Analogy. All is exactly the same like in the
fluids mechanics.
Next the electrons were discovered. Automatically Heaviside is a history
and the Gas Analogy is in power.

But you, radio people, are very close to waves and should be easy for you
to work out the answer for the Question:
Which Analogy is right?

neither analogy is 'right'. they are useful in limited circumstances to
demonstrate some basic pressure wave physics to young students. but
neither one properly reproduces electromagnetic waves.

"electromagnetic waves" are paper waves. Radio waves are real waves. Now we
must not know what the waves are like. Now we should estabilish from which
part of the radiator radiate the radio waves.
Do you agree with Richard Harisson:
"At the open circuited ends of a resonant antenna there is almost double
the forward voltage but zero total current due to cancellation of the
dorward and reflected currents at the open circuit. At the open circuit
in the wire, all the energy in the wave is transferred to the electric
field."
S*

"Cecil Moore" wrote
...
Richard Fry wrote:
At the top of a monopole, and at the ends
of a dipole the net current is almost zero -- so those locations
generate very little of the total EM radiation from these antennas.

Since the forward current and reflected current are equal
in magnitude and opposite in phase at the ends, they act
like transmission line currents and the magnetic fields
cancel at the ends. They are in phase at the feedpoint -
hence the maximum radiation at that point.

EM means elecro- magnetic. Radiation can start from any of them, See what
Richard Harrison wrote: "At the open circuited ends of a resonant antenna
there is almost double
the forward voltage but zero total current due to cancellation of the
dorward and reflected currents at the open circuit. At the open circuit
in the wire, all the energy in the wave is transferred to the electric
field."
S*

"tom"
. net...
Szczepan Bia³ek wrote:

God forbid that you should actually do some research! What a terrible
thought!

All necessary resarch are done by radio people. You all know how antennas
work. Monopole and dipole means the electric pole because no magnetic poles.
You only do not realize that EM waves can start from the ELECRIC field. The
electric field is radiated from the ends where is high voltage and no
current.
S*

On Sep 21, 12:23*pm, Szczepan Bia³ek wrote:
You only do not realize that EM waves can start from the ELECRIC field. The
electric field is radiated from the ends where is high voltage and no
current.

No, Szczepan, it is you that does not realize that voltage, alone,
cannot produce an electromagnetic field.

Only the change in current and charge flowing along a conductor, over
time, produces far-field EM radiation. That radiation includes both
the magnetic and electric fields, at right angles to each other and to
the direction of travel.

It is untrue that one part of a conductor or antenna radiates the
magnetic field, and another part radiates the electric field, no
matter the claims of the proponents of the E-H antenna (which have not
been demonstrated).

The fact that the ends of a dipole, and the top of a monopole have
very little net current flowing means that those locations cannot
contribute very much to the EM radiation from those antennas.

You really should form your opinions from research in modern textbooks
on antennas, rather than using Wikipedia and inapplicable analogies to
sound waves. At a minimum you could recognize the quotes from them on
this subject that already have been posted here.

RF

"Szczepan Bia³ek" wrote in message
...

"Richard Clark" wrote
...

I won't wait for that obvious failure. This is several steps above
your pay-grade. So, you should really attempt to work on first
principles rather than rummaging in the attic for impressive artifacts
of science.

And what should do Richard Harrison who wrote: "At the open circuited ends
of a resonant antenna there is almost double
the forward voltage but zero total current due to cancellation of the
dorward and reflected currents at the open circuit. At the open circuit
in the wire, all the energy in the wave is transferred to the electric
field. "
S*


What Richard wrote is correct, if written in a slightly provocative manner
(deliberately?). But he wasn't stating that the electric field 'At the
open-circuited ends of a resonant antenna' passes energy into a radiated
radio wave. The energy that makes it that far (i.e. isn't radiated on
account of current in the element) is stored temporarily in an
'electrostatic' field which is one of several 'reactive' or 'induction'
field components that surround a dipole antenna and decay with distance much
faster than the radiation field components (i.e. those that make up a radio
wave). As I've noted before, the term 'electrostatic' should not be
interpreted literally as an unchanging field - it is used to differentiate
between the reactive components and the radiation components of electric
field - if this offends you, just call it a 'reactive' component of electric
field. This stored energy is passed back into the antenna during the
following RF quarter cycle.

And guess what ... one of the reactive field components is longitudinal!

.... but it isn't part of a radio wave - both parts of a radio wave, the
magnetic field and the attendant electric field, are directed transverse to
the direction of propagation, but now I'm repeating myself from a week or
more ago. Power cannot be abstracted from the reactive fields, including
the longitudinal one; they affect the imaginary part of the terminal
impedance of the antenna.

Of course, I expect you will contradict all this but I still recommend that
you read a proper account of the fields around a dipole rather than making
up your own version. Since you appear to have a phobia of libraries, you
could buy a second-hand copy of Kraus, Antennas for only $15 online:
http://www.abebooks.com/servlet/Sear...nnas&x=55&y=10
and there are many, many other sources.

Failing that, you could always search the web for a bootleg copy, or one of
the MIT Radiation Laboratory series of books. I don't condone bootlegging
but someone in another newsgroup recently gave a link to a collection of
illegal copies and, in the hope of ending these ridiculous arguments, I'll
pass on what he wrote:
http://cer.ucsd.edu/~james/notes/MIT...diation%20Lab/

Chris

"Szczepan Bia³ek" wrote in message
...

"Cecil Moore" wrote
...
Richard Fry wrote:
At the top of a monopole, and at the ends
of a dipole the net current is almost zero -- so those locations
generate very little of the total EM radiation from these antennas.

Since the forward current and reflected current are equal
in magnitude and opposite in phase at the ends, they act
like transmission line currents and the magnetic fields
cancel at the ends. They are in phase at the feedpoint -
hence the maximum radiation at that point.

EM means elecro- magnetic. Radiation can start from any of them, See what
Richard Harrison wrote: "At the open circuited ends of a resonant antenna
there is almost double
the forward voltage but zero total current due to cancellation of the
dorward and reflected currents at the open circuit. At the open circuit
in the wire, all the energy in the wave is transferred to the electric
field."
S*


See my post earlier in this thread. You are misinterpreting what Richard
Harrison wrote to suit your own, incorrect, made-up version of how antennas
work.

Please think on this, Szczepan Bia³ek: the likelihood that your personal
version of the physics is correct is vanishingly small - when it conflicts
with the version everyone else (except perhaps Art Unwin) appears to
understand from their education, which is derived from the basis for
antennas that have been in use for more than 100 years.

Chris