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."

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

Can you please tell us what happened to the 10meter amateur band fractal
antenna design that was on your web site?

We would appreciate it being put back if possible as I had not got around to
building one before you took it off.

Michael

"Fractenna" wrote in message
...


May I suggest that you monitor the web site:

http://www.fractenna.com

73,
Chip N1IR

On Sun, 21 Sep 2003 11:10:09 GMT, "Michael Hart"
wrote:

Can you please tell us what happened to the 10meter amateur band fractal
antenna design that was on your web site?

We would appreciate it being put back if possible as I had not got around to
building one before you took it off.

Michael


Hi Michael,

Two words of caution.

1. DO NOT ASK WHY.
2. Do not ask here.

Either constitutes the most fruitless appeal offered in this forum.
Approach him directly and ask for only what you want without comment,
color, or explanation. Failure to observe protocol will invariably
lead to difficult correspondence, unless of course you approach on
your knees with hands clasped and raised (a few "hosannas" might be
appreciated too). ;-)

To date (for 4 years?), absolutely no other such plea has been
fulfilled. There have been absolutely no reports of any successful
constructions of this design (although it is not particularly
difficult once you do some preparation).

73's & Good luck, write when you have one warming the air,
Richard Clark, KB7QHC

I strongly endorse that caution. A couple of years ago, Chip (Dr. Nathan
Cothen) of Fractenna posted a "$1000 Challenge", offering $1000 for a
design that could better his fractal design in specific properties he
specified. Steve Best produced several, along with EZNEC models, which I
posted on my web site. (They're still there -- you can download them
from ftp://eznec.com/pub/MI2/.) The result was a long series of threats
by Chip/Cohen, and postings on numerous newsgroups and private groups
accusing me of piracy and theft of intellectual property. I wouldn't
take Chip up on any offer without great caution. At least go to
groups.google.com and see how this now-calm and rational sounding
individual has reacted in the past to anyone who dares to publicly
suggest that fractal antennas just might not be the best thing since
canned beer.

Roy Lewallen, W7EL


Robert Hohlfeld won that challenge, Mr. Lewallen. It was not a "couple of years
ago". This and other information is available on google as you state. It is
also apparent from such postings that Steve Best did not enter the challenge.
Indeed, Steve's loop(s) weren't anywhere near the best, even if they had been
submitted.

Best did not enter and did not win.

For the FOM chosen, there are certainly better loops--fractal loops--than MI2,
which was the entire point of the challenge. That is also a matter which is
archived. The challenge has obviously succeeded in firing such investigations,
which means that 'I had impact' as they say. Nothing pleases me more.

The MI2 antenna is a very useful one in some applications. It has helped
inspire a breakthrough approach to antenna optimization, which Bob Hohlfeld has
championed, based upon some earlier (published) work by me in 1996/1997. The
system incorporates genetic algorithms; fractal coding; and a supercomputer
(grid) cluster made of off the shelf PC's. You and othersmay find a
description of the system at:

http://www.fractenna.com

under the FRAGO system.

The FRAGO system is working on a daily basis on antenna optimization,
successfully I might add. It has assessed over 2 million antennas a month. It
has also been described in several publications and conferences; indeed it will
be described at one this coming week.

With regards to the statements you have made above: In October, 2001 you had an
attorney send me a letter of complaint for defamation and issued a demand of
$50,000--based upon an alleged loss. You had counsel claim that such damages
were suffered from my statements regarding ownership of copyright.

You threatened to sue myself; Fractal Antenna Systems,Inc.; Boston University;
and others.

Certain matters regarding a potential counterclaim(s) were tendered to your
counsel, and compelling evidence regarding ownership of copyright files was
also provided. Incidentally, you did not provide any evidence of damages.

Regarding MI2: Steve Best has recently published an interesting paper--as you
know--and I am quite certain there are many here who will benefit from my
corrections of factual error; omissions of citation; and so on; which will be
presented in due time.

A very brief summary: Steve's paper confirms my statement that the Small Loop
Approximation is incorrect (at least for the regimes of antennas being
considered); Steve has shown other fractal loops that share the very high (over
90%) efficiency and dipole gain; and so on, thereby corroborating the advantage
of fractal in loops of that size and need.

Clearly I see no issue, Mr. Lewallen, with you or anyone else discussing
fractal antennas or any other sort of antenna. In fact, I never have. I
presume, however, that accuracy and fact are also of some merit in the
enterprise, and I invite you to strive for that; along with me and everyone
else, in future discussions.

With Best wishes to all,

Chip N1IR