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Re: [TowerTalk] [Antenna-discussion] Fractal Antennas, Chip Cohen (N1IR)

Subject: Re: [TowerTalk] [Antenna-discussion] Fractal Antennas, Chip Cohen (N1IR) on Nova Last Night
From: jimlux <>
Date: Fri, 17 Dec 2010 13:09:41 -0800
List-post: <">>
David Jefferies wrote:
> Hmm. The interaction of character with a not-very-sound idea about bent wire
> antennas hasn't been very helpful in this case. It IS possible to shrink an
> antenna dipole by periodically bending the wires. See my articles in
> antenneX on the zagis. You can't make a true fractal antenna as the wire
> would be indefinitely long and the efficiency would tend to zero with the
> losses. But this is not the way the authors use the word "fractal" so I
> think you might say there is some sense to the proposals.

I think the fractal antennas really refers to something with some amount 
of scale invariant self similarity, using one of the standard fractals 
as a basis, e.g. Sierpinski gasket.  I believe the fractal antenna folks 
have a variety of iterated functions that are used in their designs.

As many have commented, there's some fundamental physics limits to any 
small antenna, and most designs work pretty much about the same, so you 
need something to distinguish your particular flavor of multiband small 
antenna from some one else's.  Fractals are as good as anything else.

And, if the goal is just "good match over wide bandwidth" without a lot 
of concern for absolute efficiency, then something that distributes loss 
over the whole structure might be more appealing than something simple 
like a 5 dB pad in the feed point to guarantee a 2:1 match.  There's an 
awful lot of systems applications out there that would gladly trade DC 
power for simplicity of operation (e.g. the T2FD wideband antenna)

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