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