RadioBanter - Fractal antennas

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Fractal antennas

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

"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

==================================

Fractal antennas at HF stay up long enough to discover they don't work any
better than multi-band dipoles. Or simple verticals.

The radiation patterns, of course, are somewhat modified but not enough to
make any practical difference. Particularly as they are not rotatable.
What's the point in having a rotable antenna which from one band to another
is omni-directional?

Efficiency-wise you can't improve on 95 to 98 percent anyway.

All this can be deduced just by looking at them. Like conventional antennas
they are just a few wires in space at various angles. How can an additional
bend in a wire have a significant effect?

But as you are a confirmed experimenter I guess I am unable to discourage
you from your next project. I'm sorry I do not have any antenna wire
dimensions readily at hand.

As for me, in my time I have had experience with a variety of dogs-hind-leg
fractals without being aware of it. Is an inverted-L a first-order fractal?
----
Reg, G4FGQ

Reg Edwards wrote:

Fractal antennas at HF stay up long enough to discover they don't work any
better than multi-band dipoles. Or simple verticals.

The radiation patterns, of course, are somewhat modified but not enough to
make any practical difference. Particularly as they are not rotatable.
What's the point in having a rotable antenna which from one band to
another is omni-directional?

Efficiency-wise you can't improve on 95 to 98 percent anyway.

All this can be deduced just by looking at them. Like conventional
antennas they are just a few wires in space at various angles. How can an
additional bend in a wire have a significant effect?

But as you are a confirmed experimenter I guess I am unable to discourage
you from your next project. I'm sorry I do not have any antenna wire
dimensions readily at hand.

As for me, in my time I have had experience with a variety of
dogs-hind-leg
fractals without being aware of it. Is an inverted-L a first-order
fractal? ----
Reg, G4FGQ

OK, I get your point. If you've already have a complete set of antennas, it
will probably be no use of building such a new one.
From my point of view, fractal antennas seem to be MUCH smaller than the
full size ones. So it would be an ideal solution if you live on an
appartment or don't have the permission to place a full-sized antenna
somewhere.

So for me, it would just be a better solution than 2 times 5m of wire with a
balun in the middle.

Jan, ON5DOA

Reg, G4FGQ, dismisses fractal antennas as not improving on the
efficiency of radiation, but that may not be the intent.

Kraus, in "Antennas" says:
"They also provide new insights into antenna and array design----.
----Interestingly, the self-repeating different-size structure of a
log-periodic antenna qualifies it as a fractal form."

Best regards, Richard Harrison, KB5WZI

Jan,
Very simply, they don't work worth a 'hoot'. If
you lack antenna space a 'fractal' antenna is not
the solution. Sorry...
'Doc

'Doc wrote in message ...
Jan,
Very simply, they don't work worth a 'hoot'. If
you lack antenna space a 'fractal' antenna is not
the solution. Sorry...
'Doc

I wouldn't invest in an Isotron, either.

Here is a link to some practical advice - -

http://www.alphalink.com.au/~parkerp/nooct97.htm

Speaking of "frac" tennas, here is a recent paper on the subject of
small antenna technology, which does not mention fractals (what
happened to that "Disruptive Technology" - - did the "paradigm shift"
again?)

(Looong url)

http://users.ece.gatech.edu/~durgin/...r%20Better.pdf

'Doc wrote:
Very simply, they don't work worth a 'hoot'. If
you lack antenna space a 'fractal' antenna is not
the solution. Sorry...

As Richard Harrison pointed out, a log-periodic is
a fractal antenna, by definition.
--
73, Cecil http://www.qsl.net/w5dxp

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On Tue, 11 May 2004 11:59:10 +0200, Jan Van Belle
wrote:

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

Hi Jan,

The reason you see such a void of examples is because of your very
question:
who has built one?

This question above is the one that follows:
which one to build?

And this question above is the one that follows:
what limitations do I have?
or:
what qualities do I want?

Your question is raised here on sporadic occasions, and the poster
NEVER returns to report a successful outcome. This is not due to lack
of information. For such (the largest compilation in the world)
visit:
http://www.qsl.net/kb7qhc/antenna/fractal/index.htm

You should immediately notice that the first impediment is found in
the very nature of fractal shapes.

Do you want gain? Seems not, you do not describe having a large
enough space to do that.

Do you want multi banded resonances in a small space? Probably, but
you will find very, very few examples worth the effort (frankly none).
In all likelihood you would need a tuner, and if you had a tuner, you
should skip the complication of this academic trash.

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

Cecil,
And as you know, that wasn't exactly what he asked
about. Was it?
'Doc