Discussion in 'Amateur Radio News' started by G4TUT, Dec 25, 2010.

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1. G4TUTHam MemberQRZ Page

Nathan Cohen W1YW
was interviewed about his Fractal Antenna for a TV show, Hunting the Hidden Dimension, now available to watch online.

In the show he says:

I was at an astronomy conference in Hungary, and Dr. Mandelbrot was giving a talk about the large-scale structure of the universe, and reporting how using fractals is a very good way of understanding that kind of structure, which really wowed the entire group of astronomers.

He showed several different fractals that I, in my own mind, looked at and said, "Oh, wouldn't it be funny if you made an antenna out of that shape. I wonder what it would do."

I thought back to the lecture and said, "Well, I've got a piece of wire, what happens if I bend it?" After I bent the wire, I hooked it up to the cable and my ham radio, and I was quite surprised to see that it worked the first time out of the box. It worked very well. And I discovered that—much of a surprise to me—that I could actually make the antenna much smaller, using the fractal design. So it was, frankly, an interesting way to beat a bad rap with the landlord.

Using fractals, experimentally, I came up with a very-wide-band antenna, and then I worked backwards and said, "Why is it working this way? What is it about nature that requires you to use the fractal to get there?"

The result of that work was a mathematical theorem that showed if you want to get something that works as an antenna over a very wide range of frequencies, you need to have self-similarity. It has to be fractal in its shape to make it work. And that was an exact solution. It wasn't like, "Oh, here's a way of doing it and there's a lot of other ways of doing it." It turned out, mathematically, we were able to demonstrate that was the only technique we could use to get there.

The 53-minute show was aired by the Public Broadcasting Service (PBS) and can be seen on the web at
http://www.pbs.org/wgbh/nova/physics/hunting-hidden-dimension.html

PBS have blocked the show for certain countries such as the UK but using a US-based Proxy Server will get around it.

Fractal Antenna Systems, Inc.
http://www.fractenna.com/

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2. W1YWHam MemberQRZ Page

What's REALLY important....

Making an invisibility cloak with fractals.. : EASY

Trying to get the H40 guys to op CW and phone and listen for stateside: HARD!

;-)

Merry xmas to all.And BEST of DX!

73,
Chip W1YW

3. KI4TIHam MemberQRZ Page

Hmmmmm...........

It doesn't appear to be all that mysterious.

I most probably will be wrong but it appears to me that this is just another version of a shortened antenna.

By using fractal math this shortened antenna is comprised of a continual length of inductors-capacitors all interacting along the entire length. By using fractals the designer is able to evenly distribute the inductance and capacitance along the entire length.

It may have all the limitations of a shortened antenna.

Please, someone prove me wrong!!

Ron - KI4TI

4. AB8MAPremium SubscriberQRZ Page

I think that the theory is that, even if "shortened" in space, a fractal antenna would have an infinite length. In theory. The fabrication may be an issue though.

5. KD0CACHam MemberQRZ Page

If interested in fractal antenna's , do a search on the Zed / here , there are at least a couple of ongoing threads and some closed , this show aired 1st about 2007 or so .
Has brought up lots of interesting stuff .

6. KI4TIHam MemberQRZ Page

Yes. In theory. But still the L-C interaction apparently imitates a trap. And even though the length is 'infinite', the physical size should give it all the characteristics of a trap antenna that is one continual trap.

In the end it appears to be a compromise compared to a full length antenna with all the limitations of a compromise antenna.

What-a ya think??

Ron - KI4TI

7. K4WGEHam MemberQRZ Page

There was a time when Chip would threaten to sue anyone who said that

Nathan Cohen, Ph.D.

8. W1YWHam MemberQRZ Page

The length is not infinite, every physical rendition of any fractal is finite.

Certainly you get virtual c's in addition to the obvious L. But the big question is current distribution, and how multiple Current max are placed.

Apologies that I don't have time to contribute on this thread.

I am grateful for the huge number of friendly comments I have obtained from this and other recent Zed postings and wish you all the best in 2011.

I wil be writing up an article for hams in 2011.

You might enjoy the series of videos now coming out. See my Zed bio for the link.

73,
Chip W1YW

9. KD0CACHam MemberQRZ Page

Like the other threads , not an expert , just trying to learn .
Off the top of my head / guessing , that because to the layout , it would not be like a coil , so now inductive loss's .

10. NR9FGuest

Good show on PBS

Did't know anything about fractals, until I watched the show.
Enjoyed and learned something new.
Merry Christmas and Happy New Year to Radio Land.

Al
nr9f