According to the July 1999 issue of Scientific American (available
online at
http://www.sciam.com/article.cfm?art...B7809EC588F2D7),
Motorola started using the fractal antennas inside its cellphones. Do
they still use them? And what about the other manufacturers?

"(....) Cohen, who founded Fractal Antenna Systems four years ago, is
now working with T&M Antennas, which makes cellular phone antennas for
Motorola. T&M engineer John Chenoweth says that the fractal antennas
are 25 percent more efficient than the rubbery "stubby" found on most
phones. (...)
Just why these fractal antennas work so well was answered in part in
the March issue of the journal Fractals. Cohen and his colleague
Robert Hohlfeld proved mathematically that for an antenna to work
equally well at all frequencies, it must satisfy two criteria. It must
be symmetrical about a point. And it must be self-similar, having the
same basic appearance at every scale--that is, it has to be fractal."

this is a very good question
why couldn't we have a big rubbery fractal that folded up so to say.
They have them stuck inside the unit and your have is wrapped around the
antenna, no such a good idea, why not make it in a rubber matrix and be
about 2" * 4" folding up. That would be goog for added sensitivity I
would suspect
Paul (EE)

totojepast wrote:

According to the July 1999 issue of Scientific American (available
online at
http://www.sciam.com/article.cfm?art...B7809EC588F2D7),
Motorola started using the fractal antennas inside its cellphones. Do
they still use them? And what about the other manufacturers?

"(....) Cohen, who founded Fractal Antenna Systems four years ago, is
now working with T&M Antennas, which makes cellular phone antennas for
Motorola. T&M engineer John Chenoweth says that the fractal antennas
are 25 percent more efficient than the rubbery "stubby" found on most
phones. (...)
Just why these fractal antennas work so well was answered in part in
the March issue of the journal Fractals. Cohen and his colleague
Robert Hohlfeld proved mathematically that for an antenna to work
equally well at all frequencies, it must satisfy two criteria. It must
be symmetrical about a point. And it must be self-similar, having the
same basic appearance at every scale--that is, it has to be fractal."

On Sun, 07 Sep 2003 15:29:55 GMT, Paul Victor Birke
wrote:

This is a very good question!!

Unfortunately for such a good question, the answer reveals a mediocre
reality compared to the glowing claims.


Why couldn't we have a big rubbery fractal that folded up so to say.

Proximity often leads to increasing loss, and rarely opportunity for
boundless gain.

They have them stuck inside the unit and you have your hand wrapped
around the antenna-not such a good idea since you are conducting, at
least partially, and therefore shielding the inside antenna.

Quite so, but hardly the fault of the antenna and has nothing to do
with any perceived characteristic.

Why not make it in a rubber matrix and be about 2" * 4" folding up.
That would be goog for added sensitivity I would strongly suspect.

Paul Birke (EE)

Hi Paul,

Soothe your suspicions. A randomly crushed antenna is just as
effective. However "just as effective" means equally in-effective.


totojepast wrote:

According to the July 1999 issue of Scientific American (available
online at

http://www.sciam.com/article.cfm?art...B7809EC588F2D7),
Motorola started using the fractal antennas inside its cellphones. Do
they still use them? And what about the other manufacturers?

They could. Some manufacturers sell antennas complete with resistors
for their own novel characteristics. Some cellphone users paste in a
foil do-dad sold at two for $19.95 on TV too (never mind that a piece
of aluminum foil works just as well for a penny's worth of material
and no shipping/handling fee).

"(....) Cohen, who founded Fractal Antenna Systems four years ago, is
now working with T&M Antennas, which makes cellular phone antennas for
Motorola. T&M engineer John Chenoweth says that the fractal antennas
are 25 percent more efficient than the rubbery "stubby" found on most
phones. (...)

They could also claim to be 55% more efficient than a resistor too.

Just why these fractal antennas work so well was answered in part in
the March issue of the journal Fractals. Cohen and his colleague
Robert Hohlfeld proved mathematically that for an antenna to work
equally well at all frequencies, it must satisfy two criteria. It must
be symmetrical about a point. And it must be self-similar, having the
same basic appearance at every scale--that is, it has to be fractal."


Others, who were not employed selling fractals have proven
mathematically that they are not. Now, if you replace antennas with
cigarettes and mathematics with reports on cancer, guess what clash of
reports you would find there. A simple review into the quality of
science of fractals "antenna research" reveals not very much range nor
depth. Most announcements are repetition of unique examples that you
will never find in that cellphone.

As one poster pointed out YEARS ago, was that if fractals were such a
good idea, we would all have replaced our antennas with them by now.

This, of course, has lead one fractal proponent to simply declare that
all the antennas we do use today, are already fractal! This oddball
of recursive thought leads us to then ask, what merit is there in your
particular kind? That's where you get into math 4 places to the right
of the decimal for complex geometries that could only begin to make
economic sense in the GHz frequencies (if you cared). Anyone could as
easily make the same claims for the unique color of ink in their sales
brochures giving boosted performance.

73's
Richard Clark, KB7QHC

This explains most clearly why MOT has been a bad investment since I quit in
'97.

When I went there in '81 it was a good investment.
We used to have perfect yields.
Now the factories are shut.

Fractal Geometry and Classical Electrodynamics have little to do with one
another at HF.
Or elsewhere.
Mandelbrot's office door had one picture on it when I made my observation in
'84:
Gauss's.
Buy a book.
Drink bourbon; Do math. Die anyway.
nite
H.

"Richard Clark" wrote in message
...
On Sun, 07 Sep 2003 15:29:55 GMT, Paul Victor Birke
wrote:

This is a very good question!!

Unfortunately for such a good question, the answer reveals a mediocre
reality compared to the glowing claims.

snip-

http://www.sciam.com/article.cfm?art...-9EB7809EC588F
2D7),
Motorola started using the fractal antennas inside its cellphones. Do
they still use them? And what about the other manufacturers?

They could. Some manufacturers sell antennas complete with resistors
for their own novel characteristics. Some cellphone users paste in a
foil do-dad sold at two for $19.95 on TV too (never mind that a piece
of aluminum foil works just as well for a penny's worth of material
and no shipping/handling fee).

"(....) Cohen, who founded Fractal Antenna Systems four years ago, is
now working with T&M Antennas, which makes cellular phone antennas for
Motorola. T&M engineer John Chenoweth says that the fractal antennas
are 25 percent more efficient than the rubbery "stubby" found on most
phones. (...)

They could also claim to be 55% more efficient than a resistor too.

snip-
Anyone could as
easily make the same claims for the unique color of ink in their sales
brochures giving boosted performance.

73's
Richard Clark, KB7QHC

Richard Clark wrote:


Proximity often leads to increasing loss, and rarely opportunity for
boundless gain.

I was thinking only of more sustainable gain, certainly not boundless!!

They have them stuck inside the unit and you have your hand wrapped
around the antenna-not such a good idea since you are conducting, at
least partially, and therefore shielding the inside antenna.


Quite so, but hardly the fault of the antenna and has nothing to do
with any perceived characteristic.

Indeed but not a clever design idea wrt antenna placement was my point.

Why not make it in a rubber matrix and be about 2" * 4" folding up.
That would be goog for added sensitivity I would strongly suspect.

Paul Birke (EE)


Hi Paul,

Soothe your suspicions. A randomly crushed antenna is just as
effective. However "just as effective" means equally in-effective.

Ouch!


As one poster pointed out YEARS ago, was that if fractals were such a
good idea, we would all have replaced our antennas with them by now.

Yes well that would be the case except maybe for Patent monies.

all the best
Paul

I think that the tree antenna in:

http://www.josechu.com/moving_fractal/index.htm

would be good for cellphones, provided that the length of the (horizontal or
vertical) branches is a fraction of the wavelength.

Take into account that a grandson branch has exactly half the length of its
grandfather's length.


Josechu


"totojepast" wrote in message
om...
According to the July 1999 issue of Scientific American (available
online at

http://www.sciam.com/article.cfm?art...B7809EC588F2D7),
Motorola started using the fractal antennas inside its cellphones. Do
they still use them? And what about the other manufacturers?

"(....) Cohen, who founded Fractal Antenna Systems four years ago, is
now working with T&M Antennas, which makes cellular phone antennas for
Motorola. T&M engineer John Chenoweth says that the fractal antennas
are 25 percent more efficient than the rubbery "stubby" found on most
phones. (...)
Just why these fractal antennas work so well was answered in part in
the March issue of the journal Fractals. Cohen and his colleague
Robert Hohlfeld proved mathematically that for an antenna to work
equally well at all frequencies, it must satisfy two criteria. It must
be symmetrical about a point. And it must be self-similar, having the
same basic appearance at every scale--that is, it has to be fractal."

Dear Josechu

I saw these about a year ago.
How well do they work? How well could they work wrt to gain sensitivity
which I have just noticed in a cottage situation where reception was
most borderline and involved location phone in a unique spatial vector
postion. Would this antenna somehow be better in this situation re
short whip.

BTW I think there is a US patent on these, yes?



Josechu wrote:
I think that the tree antenna in:

http://www.josechu.com/moving_fractal/index.htm

would be good for cellphones, provided that the length of the (horizontal or
vertical) branches is a fraction of the wavelength.

Take into account that a grandson branch has exactly half the length of its
grandfather's length.


Josechu


"totojepast" wrote in message
om...

According to the July 1999 issue of Scientific American (available
online at


http://www.sciam.com/article.cfm?art...B7809EC588F2D7),

Motorola started using the fractal antennas inside its cellphones. Do
they still use them? And what about the other manufacturers?

"(....) Cohen, who founded Fractal Antenna Systems four years ago, is
now working with T&M Antennas, which makes cellular phone antennas for
Motorola. T&M engineer John Chenoweth says that the fractal antennas
are 25 percent more efficient than the rubbery "stubby" found on most
phones. (...)
Just why these fractal antennas work so well was answered in part in
the March issue of the journal Fractals. Cohen and his colleague
Robert Hohlfeld proved mathematically that for an antenna to work
equally well at all frequencies, it must satisfy two criteria. It must
be symmetrical about a point. And it must be self-similar, having the
same basic appearance at every scale--that is, it has to be fractal."

On Sun, 7 Sep 2003 23:58:30 +0200, "Josechu"
wrote:

I think that the tree antenna in:

http://www.josechu.com/moving_fractal/index.htm

would be good for cellphones, provided that the length of the (horizontal or
vertical) branches is a fraction of the wavelength.

Take into account that a grandson branch has exactly half the length of its
grandfather's length.


Josechu

Hi OM,

Combining a fractal form and scaling it to "a fraction of a/the
wavelength" has no inherent correlation to suitability of application.
There is no fundamental relationship between the physics of gain of an
antenna and any fractal expression drawn out of a hat (or even one
chosen deliberately with a sophisticated guess). Your example is
visually pretty, but that counts for nothing compared to crafted
random path antennas in the hands of a practitioner of the art of
antenna design.

The only way to determine if any particular fractal is suitable, is to
test it against a standard. Few fractals pass this first cut. Worse
yet, no small fractals exhibit any gain beyond that of the
conventional dipole and rarely exhibit more gain than a small dipole.

Physical orientation is another factor if there is gain above and
beyond comparison to a small dipole (which includes a loop form by the
way). Fractals do not exhibit radiation patterns that are intuitive
from their shape (a dipole's best characteristics are broadside, a
fractal could be off at a skew - if you could first guess what the
major axis was).

Let's just cut to the chase and let me point out the poor performance
that fractals exhibit, specifically one of the best fractal examples
from the owner of Fractal Antenna Systems compared to six designs that
trounced it here in this group in open competition. These six designs
have yet to be surpassed by any product from FAS. One might say that
the pretty boy was pounded into the ground by six ugly sticks.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
"These six designs have yet to be surpassed by any product from FAS."

Maybe that`s right. John Kraus and associates are not so dismissive of
"Artistic Antennas" (Fractals) on page 772 of "Antennas For All
Applications".

The Kraus book does illustrate the more complicated impedance variations
of Fractals as compared with a loop or a flat plate used as an antenna.

Best regards, Richard Harrison, KB5WZI

Um, if Kraus (and Marhefka) was not dismissive of Fractals, why name
the chapter "Artistic Antennas"? In my opinion, it was a polite
dismissal.

Please read Steve Best's excellent paper in the IEEE Antennas and
Propagation magazine. It shows that Fractals have no particular
advantage over non-fractal shapes of similar parameters.

-Spencer Webb
KW2S
www.antennasys.com
(and contributor to Kraus' Antennas 3rd. ed.)



Hi Spence--

Always happy to hear from someone at another antenna company:-)

May I thus quote you as saying that the intent of the authors and contributors
was to dismiss fractal antennas?

Steve Best's article :

"A Discussion on the Significance of Geometry in Determining the Resonant
Behavior of Fractal and other non-Euclidean Wire Antennas"; AP Magazine;45,3
(June 2003)

does not show what you said. The statement is made in the magazine, but it is
not shown to be so nor supported by the data.

May I suggest that you monitor the web site:

http://www.fractenna.com

which will host a critique of the article. Indeed, I invite you to also host
the critique on your web site if you wish. The editor of AP Magazine was also
invited to publish the critique(when it comes out) and, indeed, it would make
sense to publish any relevant reviewer reports with it.

The timing of this availability will be decided by Steve's next publication,
which is expected to be in the next few weeks.

Thank you for the opportunity to correct information and post a relevant source
for info on this public forum.

73,
Chip N1IR