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Old May 17th 04, 08:03 AM
Jan Van Belle
 
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Richard Clark wrote:
In open competition between an Amateur and the professional fractal
builder, the professional lost against 6 designs that trounced the
best professional fractal on the basis of gain for the smallest
footprint. That is to say, all seven antennas were bound within a
prescribed "small" area (such as you describe), and the fractal came
in dead last.

73's
Richard Clark, KB7QHC


Sorry,

I've had a little accident while sporting and since I've only
a quick connection at the QRL, I couldn't check my mail and this newsgroup.

OK, thanx for the explanation. It seems I can leave it now! I thought it
would be a nice solution: a big amount of wire on a small area. But if
performance is even lower as other antennas and I can only come out on QRP
(I've got an FT-817) it is probably not the thing to choose for in first
instance.

Thanks all for the replies, links, etc. !!

73's de Jan, ON5DOA

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Old May 25th 04, 09:15 PM
k4wge
 
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"Jimmy" wrote in message .com...
"Jan Van Belle" wrote in message
...
Hello all,

The last days I was searching for more info o how to build fratal
antennas on the web. But besides lots of links to fractenna.com and a few
powerpoint slides I found nothing.

Has anyone sucessfully build such an antenna for HF? Is anyone using it?

Kind regards,

Jan, ON5DOA


A fractal antenna is just another antenna that uses lumped inductance to
shrink the size of the antenna along with destroying the radiation pattern.
The arrl has a nice explantion of why antennas radiate on their web site.
Aplly this info to fractals and small coils and it is easy to see why they
dont work worth a hoot.


An 18 page paper entitled

FRACTAL ANTENNAS
Introduction to fractal technology and presentation of a fractal
antenna adaptable to anytransmitting frequency - The "FRACTENT"
By Werner Hödlmayr, DL6NDJ
January 2004

Can be downloaded at www.antenneX.com

His conclusion:

"The attentive reader will note that the spacing of resonant
frequencies in a fractal structure is logarithmic, whereas most of the
HF amateur bands follow a linear sequence. This means that the antenna
structure has to have a scaling which follows the same logarithmic
law. To build such an antenna is a challenge asking for a professional
simulation program (which allows more than 10,000 segments) and very
much perseverance."

Interesting references:

[2] Jaggard, D.L. (1990): On Fractal Electrodynamics. In Recent
Advances in
Electromagnetic Theory, H.N. Kritikos and D.L. Jaggard, editors,
Springer-Verlag, New York.
[3] Jaggard, D.L. (1991): Fractal Electrodynamics and Modeling. In
Directions in Electromagnetic Wave Modeling. Plenum Publishing Co.,
New York, 435-446
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Old May 26th 04, 05:24 PM
Richard Clark
 
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On 26 May 2004 06:29:27 -0700, (k4wge) wrote:

D.L.Jaggard's webpage:
http://www.seas.upenn.edu/~jaggard/
Too bad he doesn't have a patent pending or he would be the father of
fractal antennas. ;-)

Dare we wonder that these fractal children are legitimate? They sure
are *******s to build and they work like a dead-beat brother-in-law.

73's
Richard Clark, KB7QHC
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Old May 27th 04, 02:33 AM
Cecil Moore
 
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william ewald wrote:
"Zagi antenna construction and measurements
A zagi antenna is made from serrated wire or plate. It has reduced
dimension because of the slow wave characteristics of the periodic
structure. The student is asked to construct and measure a Zagi for
the 225MHz digital broadcast band in the UK. "


Stand by - I am inventing a zig-zagi.



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Old May 27th 04, 09:57 AM
Jan Van Belle
 
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k4wge wrote:


An 18 page paper entitled

FRACTAL ANTENNAS
Introduction to fractal technology and presentation of a fractal
antenna adaptable to anytransmitting frequency - The "FRACTENT"
By Werner Hödlmayr, DL6NDJ
January 2004

Can be downloaded at www.antenneX.com


in fact, that was the article that raised all the questions ;-)
I found it interesting, but wanted to know if hams are really using it!

Kind regards,

Jan, ON5DOA

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Old May 28th 04, 03:32 AM
Brian Kelly
 
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Cecil Moore wrote in message ...
william ewald wrote:
"Zagi antenna construction and measurements
A zagi antenna is made from serrated wire or plate. It has reduced
dimension because of the slow wave characteristics of the periodic
structure. The student is asked to construct and measure a Zagi for
the 225MHz digital broadcast band in the UK. "


Stand by - I am inventing a zig-zagi.


Chip already patented it.




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Old June 3rd 04, 04:57 PM
k4wge
 
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Jan Van Belle wrote in message ...

I found it interesting, but wanted to know if hams are really using it!

Kind regards,

Jan, ON5DOA


Have you looked at the W0FMS page at

http://www.fredspinner.com/W0FMS/fractant/

Fred says, "The purpose of this web page is to further explain the
details of the rather contraversial Fractal Antenna. This antenna uses
a fractal shape to load a radiating element, allowing, according to
Nathan (Chip) Cohen, N1IR 2x to 4x reduction in size with little loss
in gain and/or F/B. I haven't tried this antenna yet, which is patent
pending from Fractal Antenna Systems, Inc. (Fractenna), so I claim
nothing else than to have deciphered the (IMHO) rather cryptic
building instructions in the
http://www.fractenna.com/ham/hampage1.html
page describing a 10-m 2 element quad fractal antenna. In order to
avoid potental criticism, I am stating for the record that the
instructions on the site are adequate for assembling this antenna. I
am also stating that for most, it is very hard to understand these
directions without a starting point of reference. It took me a couple
of hours to figure it out, and I'm a EE... "
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Old June 9th 04, 12:38 PM
Fractenna
 
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in fact, that was the article that raised all the questions ;-)
I found it interesting, but wanted to know if hams are really using it!

Kind regards,

Jan, ON5DOA


Not to my knowledge, Jan.

The presently and easily available (that is, free) info on fractal antennas
for hams is poor in content and often factually inaccurate, in my opinion, and
this is likely to remain so. In the world we live in today, this makes a lot of
a sense in its own quirky fashion.

Commercial uses are a different story, however. Of course, that's not what this
NG is about.

When hams switch to software radios in a big way then fractal antennas targeted
to hams might be worth making more widely known. With some luck, they'll be a
few of us 'hams' left then!

73,
Chip N1IR
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Old June 9th 04, 04:06 PM
Andy Cowley
 
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Fractenna wrote:


When hams switch to software radios in a big way then fractal antennas targeted
to hams might be worth making more widely known. With some luck, they'll be a
few of us 'hams' left then!



Maybe this is a naive question, but how does an antenna, fractal or
otherwise, know what kind of transmitter is driving it? Why are
software radios more suited to this design?

vy 73

Andy, M1EBV


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