Hello Richard (my middle name is Ricardo = Richard. We are
"Tocayos"...)

Richard wrote:

Can there be an escape? Ron's question was posed with an impossible
proposition. A collapsing sphere of electromagnetic energy?

Ron wrote:

Assume an incoming rf signal has exactly the same strength in all 3
dimensions i.e., completely omnidirectional.

If I have understood well Ron's question...

What about a number tending (spreading?, going to? - a limit, as in
calculus ) to infinite, of coherent punctual electromagnetic identical
sources on the inner surface of a sphere with testing antennas in
center of it? (I think it isn't necessary neither coherence or
identicals sources. Noise sources fix well in my interpretation of the
concept that (I believe) Ron it wanted expose to us).

Can it these conditions to be thought?
Could it be simulated with an electromagnetic CAD as FEMLAB?
Are they agree with Ron question?

What do you say Ron?

Miguel Ghezzi (LU 6ETJ)

PS: I have another physical doubt, if you can help me.
Can a real DC current radiate electromagnetic energy?.
It is not captious or cheat question. I think yes, but I don't want to
condition your answers with my hypotesis.

Thank you in advance for your answers.
-------------------------------------------------------------------------------------------------------------------
Richard escribió:

Puede haber una salida?. La pregunta de Ron fue presentada con
proposicion imposible. Una esfera de energía electromagnetica colapsandose?

Ron escribio:

Asuma una señal de rf entrante que tiene exactamente la misma intensidad en las tres dimensioes, por ej, que es completamente omnidireccional.

Si he comprendido bien la pregunta de Ron...

Que tal un numero tendiendo a infinito de fuentes electromagneticas
puntuales identicas, situadas sobre la superficie interior de una
esfera y las antenas de prueba en el centro de la misma? (creo que no
es necesaria ni coherencia ni fuentes identicas, fuentes de ruido van
bien en mi interpretacion del concepto que (creo) que Ron quiso
presentarnos.

Pueden estas condiciones ser pensadas?
Podrian simularse en un CAD de electromagnetismo, tal como FEMLAB?
Estan ellas de acuerdo con la pregunta de Ron?

Que dices tu Ron?

Miguel Ghezzi (LU 6ETJ)

PS: Tengo otra duda física si ustedes pueden ayudarme. Puede una CC
real irradiar energía electromagnetica?
No es una pregunta capciosa ni una broma. Yo creo que si, pero no
quiero condicionar sus respuestas con mi hipotesis.

Agradezco sus respuestas por adelantado.

Richard Clark wrote:

On 30 Oct 2005 15:50:50 -0800, "lu6etj" wrote:


although that is
not possible for the whole universe (I suppose this allows me to escape
elegantly of Richard's question... ; D

73=B4s for all, and thank you very much for your very interesting and
instructive habitual postings.


Hi Miguel,

Can there be an escape? Ron's question was posed with an impossible
proposition. A collapsing sphere of electromagnetic energy? This has
so many so many fantastic presumptions built in.

On all but the smallest of scales, the sky is quite uniform in its
luminosity. It can hardly be described as a "collapsing sphere"; not
even from the point of view of a geocentric model of the universe.

ac6xg

On 31 Oct 2005 09:35:09 -0800, "lu6etj" wrote:

PS: I have another physical doubt, if you can help me.
Can a real DC current radiate electromagnetic energy?.
It is not captious [capricious] or cheat [trick] question. I think yes, but I don't want to
condition your answers with my hypotesis.

Hi Miguel,

A "real" DC current?

Yes.

A "real" DC current (at some point in time) starts - and stops. It is
at each of these two points that the step change offers radiation. The
"time" it takes to go from one level to the other defines that
frequency, and its harmonics.

A "perfect" DC current has always been on, and will always be on. No
change, no radiation.

73's
Richard Clark, KB7QHC

On Mon, 31 Oct 2005 10:16:07 -0800, Jim Kelley
wrote:

On all but the smallest of scales, the sky is quite uniform in its
luminosity. It can hardly be described as a "collapsing sphere"; not
even from the point of view of a geocentric model of the universe.

Hi Jim,

Perhaps not, but "quite uniform" is rather in the eye of the beholder.
When I take panagraphic photographs (a broad scale), it is quite
evident that the uniformity is not very uniform. Another variable is
that polarization is not very uniform either (which, photographically
may be saying the same thing).

The eye is a wonderful device, but not very precise.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On Mon, 31 Oct 2005 10:16:07 -0800, Jim Kelley
wrote:


On all but the smallest of scales, the sky is quite uniform in its
luminosity. It can hardly be described as a "collapsing sphere"; not
even from the point of view of a geocentric model of the universe.


Hi Jim,

Perhaps not, but "quite uniform" is rather in the eye of the beholder.

It's quite impossible to behold anywhere near the smallest of scales by
eye, Richard.

When I take panagraphic photographs (a broad scale), it is quite
evident that the uniformity is not very uniform. Another variable is
that polarization is not very uniform either (which, photographically
may be saying the same thing).

The eye is a wonderful device, but not very precise.

It's like the internet in that regard, where people, with just the right
amounts of terminology and pomposity, can assume the status of expert at
just about anything and everything! ;-)

ac6xg

Hi, all folks and Dear Richard (Is right this salutation?)

Thanks for your patience to me...

Imagine a simple DC generator in steady state, the closing circuit
(sure, with a serie resistance, no short), forms a physical loop, the
current travel accross it in a uniform circular movement, therefore
charges have a centripet acceleration = charges accelerated =
electromagnétic radiation.

Electron orbiting nucleus problem - quantum theory solution.

Am I in the correct way?. DC current produce electromagnetic radiation
(on solenoid more, of course)?

I never read something in such a sense (except in atomic theory, of
course), but I find reasonable to suppose it.

Thanks in advance

Miguel Ghezzi (LU 6ETJ)
------------------------------------------------------------------------------------------------------------

Hola a todos y estimado Richard. (es correcto saludar asi?)

Gracias por su paciencia.

Imagine un simple generador de CC en regimen estacionario, el circuito
que lo cierra (por supuesto con una resitenci, no en corto) forma un
lazo físico. La corriente viaja a traves de el en un movimiento
circular uniforme, por lo tanto las cargas poseen una
aceleracion centripeta = cargas aceleradas = radiacion
electromagnetica...

El problema del electron orbitando el nucleo - solucion de la teoria
cuantica.

Estoy en lo correcto? La corriente continua produce radiacion
electromagnetica (mas en un solenoide, por supuesto)?

Nunca lei nada en tal sentido (excepto en la teoria atomica, por
supuesto) pero me parece razonable suponerlo

Miguel Ghezzi (LU 6ETJ)

Question (repeated here for convenience):
--------------------------------------------------------------------
Assume a receiving antenna is in the center of a sphere and the
received signal is coming in equal amounts from all points on the
surface of the sphere. Which receiving antenna would capture more
power, an omni or a high gain beam? There are no noise and no losses.
---------------------------------------------------------------------

First, thanks for all the comments. They have helped me better
understand the answer. I am leaning toward the belief that the omni
(isotropic) antenna would capture more power and, as odd as it may
seem, would have more gain than a high gain beam (or any other
directional antenna for that matter). Here is my thinking:

This is a very unusual RF field. Usually the field is assumed to be
planar with coherent rays - then antennas behave as expected. But this
field originates uniformly from all points on the surface of a sphere.
It does not spread but converges at the focal point of the sphere.

An isotropic antenna placed at the focal point would collect all of
the rays whereas a directional antenna at would not.

Therefore, in this particular situation, the isotropic would have
higher gain and capture more power than any directional antenna.

Please correct me if I am wrong.

Ron, W4TQT

On 31 Oct 2005 12:07:29 -0800, "lu6etj" wrote:

Hi, all folks and Dear Richard (Is right this salutation?)

Hi Miguel,

It is fine.

Imagine a simple DC generator in steady state, the closing circuit
(sure, with a serie resistance, no short), forms a physical loop, the
current travel accross it in a uniform circular movement, therefore
charges have a centripet acceleration =3D charges accelerated =3D
electromagn=E9tic radiation.

You are using acceleration in its usual sense. Unfortunately, it is
based on a poor description for radiation. It is a poor description
in English, or any language.

Electron orbiting nucleus problem - quantum theory solution.

Circular motion is always acceleration, and orbital electrons are
always in circular motion. They are not always radiating. This one
observation is enough to invalidate the general description of
accelerating electrons causing radiation (it takes more than that).

An orbital electron only radiates when it changes orbital levels to a
LOWER orbit. Read about deBroglie waves. When an Hydrogen electron
in the 3rd orbital falls (acceleration) to the 2nd orbital, it
radiates a photon with a wavelength of 653 nM. You see this every
night with Neon signs.

Am I in the correct way?. DC current produce electromagnetic radiation
(on solenoid more, of course)?

No.

I never read something in such a sense (except in atomic theory, of
course), but I find reasonable to suppose it.

Reasonable, as I have described above, but not logical.

73's
Richard Clark, KB7QHC

Question (repeated here for convenience):
--------------------------------------------------------------------
Assume a receiving antenna is in the center of a sphere and the
received signal is coming in equal amounts from all points on the
surface of the sphere. Which receiving antenna would capture more
power, an omni or a high gain beam? There are no noise and no losses.
---------------------------------------------------------------------

First, thanks for all the comments. They have helped me better
understand the answer. I am leaning toward the belief that the omni
(isotropic) antenna would capture more power and, as odd as it may
seem, would have more gain than a high gain beam (or any other
directional antenna for that matter). Here is my thinking:

This is a very unusual RF field. Usually the field is assumed to be
planar with coherent rays - then antennas behave as expected. But this
field originates uniformly from all points on the surface of a sphere.
It does not spread but converges at the focal point of the sphere.

An isotropic antenna placed at the focal point would collect all of
the rays whereas a directional antenna at would not.

Therefore, in this particular situation, the isotropic would have
higher gain and capture more power than any directional antenna.

Please correct me if I am wrong.

Well, for one thing, your model assumes something which does not and
cannot exist. It assumes the existence of an actual isotropic
antenna. Such cannot actually be constructed - there's no way to get
a truly omnidirectional radiation pattern without violating Maxwell's
equations.

I suspect that you'll find the same problem existing, in the reverse
direction, if you try to construct the sort of RF field you're talking
about. If you try to specify the E-plane and H-plane field components
for a uniform, arriving-from-all-points-of-a-sphere field, I believe
that you'll find that you can't achieve your goal: there will always
be "seams" (abrupt discontinuities or cancellations) in the field
components in some directions.

--
Dave Platt AE6EO
Hosting the 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!

Ron wrote:

Question (repeated here for convenience):
--------------------------------------------------------------------
Assume a receiving antenna is in the center of a sphere and the received
signal is coming in equal amounts from all points on the surface of the
sphere. Which receiving antenna would capture more power, an omni or a
high gain beam? There are no noise and no losses.
---------------------------------------------------------------------

First, thanks for all the comments. They have helped me better
understand the answer. I am leaning toward the belief that the omni
(isotropic) antenna would capture more power and, as odd as it may seem,
would have more gain than a high gain beam (or any other directional
antenna for that matter). Here is my thinking:

This is a very unusual RF field. Usually the field is assumed to be
planar with coherent rays - then antennas behave as expected. But this
field originates uniformly from all points on the surface of a sphere.

Uniformly inward, outward, or both?

It does not spread but converges at the focal point of the sphere.

By focal point of the sphere do you mean the center of the sphere? How
big of a sphere are we talking about, and where is the antenna in
relation to the sphere?

An isotropic antenna placed at the focal point would collect all of the
rays whereas a directional antenna at would not.

Probably.

Therefore, in this particular situation, the isotropic would have higher
gain and capture more power than any directional antenna.

Not according to the accepted use of the term 'gain' in connection with
antennas.

Please correct me if I am wrong.

Ron, W4TQT

In the instance you describe, the antenna with gain will pick up less
signal than an antenna without gain. The gain antenna will be able to
sense signal arriving from only a fraction of the sphere, whereas the
isotropic antenna responds to signals arriving from the entire 4-pi
sphere. Therefore, the antenna with less gain produces the greater
signal level. But this should often be the case when a directional
antenna is pointed away from most of the signal. The omni, on the other
hand, is 'pointed toward' this particular signal in all directions.

Out of curiosity, what kind of signal source are you interested in?

ac6xg