Art Unwin wrote:

Mike you forget.
I do not subscribe to the wave theory over the particle aproach.
I cannot see any other way to fit that "radiation is from the
acceleration of a charge". And I can not find any explanation of this
in any books. Only mass is able to have spin and at the same time
transport energy, at least to my mind.

So are you saying that FR energy has mass, or that it doesn't have spin?



Therefore accelaration is the
creation of two forces that are not in the same plain ala a shear
action where the combination of gravity and the Coriolis force are the
weakest forces known in the std model.

What is the acceleration of RF?

- 73 de Mike N3LI -

In article ,
Jeff Liebermann wrote:

I forgot to connect my comments to the original question. Sorry(tm).
You're correct. There's no way to get a good isotropic radiator
pattern with a simple vertical radiator. However, you can still get
fairly close if you make the antenna sufficiently small relative to
the operating wavelength. As the physical antenna size approaches a
point radiator, the pattern starts to look rather spherical.

The difference in pattern between a half-wavelength dipole,
and an infinitesimally-short dipole (i.e. one whose length
approaches a point source) is actually quite small. Both are
torus-shaped patterns, with a deep null along the axis of the antenna
(theoretically, the null is infinitely deep directly along the axis).

An infinitesimally-short dipole has a maximum gain of 1.76 dBi.

A half-wavelength dipole has a gain of 2.15 dBi.

There really isn't much to distinguish the two, as far as the pattern
and gain go.

Unfortunately, the gain drops, efficiency drops, and feed point
impedance drops, resulting in a rather inferior antenna.

Yeah, the low radiation resistance and high reactance of the short
dipole are its biggest drawbacks.

--
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!

On Fri, 4 Sep 2009 16:44:48 +0100, "christofire"
wrote:

"Jeff Liebermann" wrote in message
.. .
However, you can still get
fairly close if you make the antenna sufficiently small relative to
the operating wavelength. As the physical antenna size approaches a
point radiator, the pattern starts to look rather spherical.

That doesn't sound right. The directivity gain of an infinitesimal electric
doublet (i.e. a dipole with infinitesimal length) is about 0.4 dB less than
that of a half-wave dipole.

I'll plug a series of shortened dipoles, possibly with loading coils,
into 4NEC2 and see what happens. You may be right.

As I recall, the big holes in the pattern, that are inline with the
elements gets smaller is diameter as the antenna gets electrically
smaller. The rounded circular donut pattern tends to flatten. I
wanna play with the models to be sure. This still begs the question
of how close to spherical does the pattern need to be in order to call
it isotropic? Dunno.

I was once told a true isotropic radiator would have to be circularly
polarised

"Near isotropic circularly polarized antenna"
http://www.google.com/patents?id=saMgAAAAEBAJ
CP satellite antenna used on Intelsat V. I've been looking at the
patent for a while trying to figure out how it works.

Yeah, it should be CP because that would correctly fit the definition
of the field being identical along the sphere, in all possible
measurement antenna orientations. Note that the isotropic simulator I
posted is *NOT* circularly polarized. If you plug the deck into 4NEC2
and instead of looking at the total gain in the 3D window, look at the
vertical and horizontal gains individually, you'll see something
really ummm.... interesting.
http://802.11junk.com/jeffl/antennas/isotropic/isotrop2-vert.jpg
http://802.11junk.com/jeffl/antennas/isotropic/isotrop2-horiz.jpg
Needless to say, that the polarization is not even close to being
uniform over the sphere. (I'll add these to the menu as soon as I can
figure out what the latest JAlbum update broke in my photo
collection).

Drivel: Just got 4NEC2 setup on my new computah (Dell Optiplex 755
E8500 with 4GB). A messy tower and antenna simulation, that took over
an hour on my old PIII/1GHz clunker, now takes about 4 minutes. I'm
happy (for now).




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sep 4, 12:48*pm, Michael Coslo wrote:
Art Unwin wrote:
Mike you forget.
I do not subscribe to the wave theory over the particle aproach.
I cannot see any other way to fit that "radiation is from the
acceleration of a charge". And I can not find any explanation of this
in any books. Only mass is able to have spin and at the same time
transport energy, at least to my mind.

So are you saying that FR energy has mass, or that it doesn't have spin?

Therefore accelaration is the
creation of two forces that are not in the same plain ala a shear
action where the combination of gravity and the Coriolis force are the
weakest forces known in the std model.

What is the acceleration of RF?

* * * * - 73 de Mike N3LI -

The speed of light.

Dave wrote:

wrote in message
...
On Sep 3, 10:33 am, Art Unwin wrote:
And I imagine that there are still many readers world wide
who are still wondering what constitutes "equilibrium" in
an antenna system.

not any more, he defined it just the other day, equilibrium==isotropic.

And again today in response to Cecil concerning a full wave loop versus
full wave dipole, equilibrium == no reflections.

I don't think he's sure what equilibrium is except that it's his trump
card in an argument.

Art Unwin wrote:
On Sep 4, 12:48 pm, Michael Coslo wrote:
Art Unwin wrote:
Mike you forget.
I do not subscribe to the wave theory over the particle aproach.
I cannot see any other way to fit that "radiation is from the
acceleration of a charge". And I can not find any explanation of this
in any books. Only mass is able to have spin and at the same time
transport energy, at least to my mind.
So are you saying that FR energy has mass, or that it doesn't have spin?

Therefore accelaration is the
creation of two forces that are not in the same plain ala a shear
action where the combination of gravity and the Coriolis force are the
weakest forces known in the std model.
What is the acceleration of RF?

- 73 de Mike N3LI -

The speed of light.

Acceleration isn't expressed as C.

Does RF energy have mass?

Mike Coslo wrote:

The speed of light.

Acceleration isn't expressed as C.

Does RF energy have mass?


If it does that could explain the weight gain over my years as a ham.

tom
K0TAR

"Art Unwin" wrote in message
...
On Sep 4, 12:48 pm, Michael Coslo wrote:
What is the acceleration of RF?
The speed of light.

and you call yourself a mechanical engineer?? how are speed and
acceleration related in your mechanical world?

On Sep 4, 3:03*pm, Mike Coslo wrote:
Art Unwin wrote:
On Sep 4, 12:48 pm, Michael Coslo wrote:
Art Unwin wrote:
Mike you forget.
I do not subscribe to the wave theory over the particle aproach.
I cannot see any other way to fit that "radiation is from the
acceleration of a charge". And I can not find any explanation of this
in any books. Only mass is able to have spin and at the same time
transport energy, at least to my mind.
So are you saying that FR energy has mass, or that it doesn't have spin?

Therefore accelaration is the
creation of two forces that are not in the same plain ala a shear
action where the combination of gravity and the Coriolis force are the
weakest forces known in the std model.
What is the acceleration of RF?

* * * * - 73 de Mike N3LI -

The speed of light.

Acceleration isn't expressed as C.

Does RF energy have mass?

Yes if you see it as a particle and not a electromagnetic wave.

On Sep 4, 3:29*pm, "Dave" wrote:
"Art Unwin" wrote in message

...
On Sep 4, 12:48 pm, Michael Coslo wrote:

What is the acceleration of RF?
The speed of light.

and you call yourself a mechanical engineer?? *how are speed and
acceleration related in your mechanical world?


Because acceleration is following a parabolic curve beyond which it
has attained the speed of light. I cannot determine the acceleration
as that is a determinate of. L. and C As it happens the speed of
light was determined after radiation which to my mind puts it firmly
into the particle arena