[TowerTalk] fractal antenna

[Fred Hopengarten]

From:
Fred Hopengarten  K1VR               781/259-0088
Six Willarch Road
Lincoln, MA 01773-5105
permanent e-mail address:  fhopengarten@mba1972.hbs.edu

K1VR:  

	As usual, Tom, you ask the right questions. Of course  I define
"the right questions" as the ones I ask myself.

On Wed, 23 Dec 1998 20:47:09 -0500 "w8ji.tom" <w8ji.tom@MCIONE.com>
writes:

>There is no electrical advantage to packing a ton of 
>wire in a small space, unless the goal is a heater. 


K1VR:  You should probably never accept engineering opinions from a
lawyer, but if I heard it right, I think N1IR is saying that the
"advantage" of a fractal antenna is that it is more "efficient" than
other  reduced to similar size antennas. I don't think I've ever heard
him claim that it is more efficient than a full sized antenna of similar
design (i.e., a fractal two el. quad is less efficient than a full size
two el. quad)..

>So far as I know, no one has ever answered the simple question "why 
>does fractal folding offer a performance advantage?".


K1VR:  N1IR has an article in in the works that will further attempt to
do that. But it would be wrong to assume absolute performance advantage. 
The advantage is only when compared to antennas occupying the same real
estate.

>I see two major issues that are unresolved:
>
>1.) The data is based almost entirely on models. There are many losses 
>not
>accounted for in modeling when wires are bent at fractional wavelength
>intervals. Performance could be a whole lot worse than expected in 
>many cases.

K1VR:  I believe that N1IR has built at least four (and perhaps more) of
these beasts. I think they offer the greatest "advantage" when they can
be lithographed, but his present 10 meter quad is pretty damn small and
appears to work very well. I saw his logbook at a party at his house last
Sunday.

[Yeah, yeah.  You can buy my endorsement for some really good roast beef
sandwiches and a beer.]


>2.) The antennas are virtually impossible to construct.

K1VR: I agree, at frequencies below 28 MHz. And below frequencies where
they can be screen printed, they are still awkward. But I'm always
charmed by experimentation, and he's not only modeling -- he's also
building.

Again, I fully concur that these are the right questions to ask, and I
know that Chip will, in due course, be trying to answer them.
.
.
.
.
.
.
.
.

___________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
or call Juno at (800) 654-JUNO [654-5866]

--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm