Log-Periodic Antenna Design
 

Jim Lux wrote:
Cecil Moore wrote:
http://ieeexplore.ieee.org/Xplore/lo...number=1610336
If you are a member of IEEE, you can access this paper:
Multiband behavior of wideband Sierpinski fractal bow-tie antenna
Yamini, A.H.; Soleimani, M.
Microwave Conference, 2005 European
Volume 3, Issue , 4-6 Oct. 2005 Page(s): 4 pp. -
Digital Object Identifier 10.1109/EUMC.2005.1610336

interesting paper..

The big benefit (from a cursory reading).. is that you have a more
consistent antenna pattern over the frequency range, which the vanilla
bowtie does not. And a somewhat wider match bandwidth. (mostly extending
it to higher frequencies)

There is apparently a "big benefit" for some applications
contrary to the nay-sayers on this newsgroup. Apparently,
the self-symmetry of fractals leads to some predictability
as far as wide-band response goes.

Nothing magic, though.

Don't remember anyone saying that fractals were magic. They
certainly obey Maxwell's laws. I suspect their advantages,
like their straight-wire cousins, lie in the predictability
of their mathematical models.
--
73, Cecil http://www.w5dxp.com

Log-Periodic Antenna Design
 

Cecil Moore wrote:
Jim Lux wrote:
Cecil Moore wrote:
http://ieeexplore.ieee.org/Xplore/lo...number=1610336
If you are a member of IEEE, you can access this paper:
Multiband behavior of wideband Sierpinski fractal bow-tie antenna
Yamini, A.H.; Soleimani, M.
Microwave Conference, 2005 European
Volume 3, Issue , 4-6 Oct. 2005 Page(s): 4 pp. -
Digital Object Identifier 10.1109/EUMC.2005.1610336

interesting paper..

The big benefit (from a cursory reading).. is that you have a more
consistent antenna pattern over the frequency range, which the vanilla
bowtie does not. And a somewhat wider match bandwidth. (mostly
extending it to higher frequencies)

There is apparently a "big benefit" for some applications
contrary to the nay-sayers on this newsgroup. Apparently,
the self-symmetry of fractals leads to some predictability
as far as wide-band response goes.

As opposed to randomly trying other shapes, I guess..

So fractals fit in the "handy design approach" category

Log-Periodic Antenna Design
 

On Mon, 24 Nov 2008 14:02:10 -0600, Cecil Moore
wrote:

predictability
predictability

I dare say the Yea-sayers cannot predict any specific, practical,
fractal characteristic when given fractal
mathematical models.

For the inverse (starting with the practical instead of the
mathematical model) one very simple test:
give the mathematical model for a single fractal
antenna specifically resonant on each frequency:
1.85MHz;
3.8MHz;
7.15MHz;
10.13MHz;
14.15MHz;
18.11MHz;
21.2MHz;
24.93MHz;
28.5MHz,
to within the margins of any Ham band represented by the single
frequency offered.

Solution:
Biconical;
LPDA
(barring, of course, no one can give the fractal mathematical models).
Of course, the joke here is that these are neither very gainful, nor
small - the presumed boon of fractal invention. Yet no other
"fractal" can describe this antenna above. Those "fractals" that come
close (maybe covering 3 of the 9 bands) aren't small or gainful
either. Sometimes you just can't win for trying either.

Going to specifics, what is the mathematical model (not just a word
salad description) for a Sierpinksi Gasket? Using that mathematical
model (what students call plug-n-chug for solving an equation), show
the free space best gain at its sixth iteration, fourth resonance (the
30M band of the description above).

What is the greatest physical dimension of this 9 band antenna? What
would be its greatest physical dimension if implemented in a fourth
iteration Triadic Cantor (if, in fact, one were possible to support
these resonances)?

So, a specific fractal antenna, a specific implementation, a specific
characteristic - and years before anyone here will offer a
demonstration of -dare I say it?- predictability. Hasn't happened
from any other correspondents here to this board in the entire history
of the topic. In that same history, not one other scribbler has
offered a link to someone who can do their work for them.

Fractals, always amusing.

Log-Periodic Antenna Design
 

On Nov 24, 4:02*pm, Richard Clark wrote:
On Mon, 24 Nov 2008 14:02:10 -0600, Cecil Moore
wrote:

predictability
predictability

I dare say the Yea-sayers cannot predict any specific, practical,
fractal characteristic when given fractal

mathematical models.

For the inverse (starting with the practical instead of the
mathematical model) one very simple test:
* * * * give the *mathematical model for a single fractal
* * * * antenna specifically resonant on each frequency:
* * * * 1.85MHz;
* * * * 3.8MHz;
* * * * 7.15MHz;
* * * * 10.13MHz;
* * * * 14.15MHz;
* * * * 18.11MHz;
* * * * 21.2MHz;
* * * * 24.93MHz;
* * * * 28.5MHz,
to within the margins of any Ham band represented by the single
frequency offered.

Solution:
* * * * Biconical;
* * * * LPDA
(barring, of course, no one can give the fractal mathematical models).
Of course, the joke here is that these are neither very gainful, nor
small - the presumed boon of fractal invention. *Yet no other
"fractal" can describe this antenna above. *Those "fractals" that come
close (maybe covering 3 of the 9 bands) aren't small or gainful
either. *Sometimes you just can't win for trying either.

Going to specifics, what is the *mathematical model (not just a word
salad description) for a Sierpinksi Gasket? *Using that mathematical
model (what students call plug-n-chug for solving an equation), show
the free space best gain at its sixth iteration, fourth resonance (the
30M band of the description above).

What is the greatest physical dimension of this 9 band antenna? *What
would be its greatest physical dimension if implemented in a fourth
iteration Triadic Cantor (if, in fact, one were possible to support
these resonances)?

So, a specific fractal antenna, a specific implementation, a specific
characteristic - and years before anyone here will offer a
demonstration of -dare I say it?- *predictability. *Hasn't happened
from any other correspondents here to this board in the entire history
of the topic. *In that same history, not one other scribbler has
offered a link to someone who can do their work for them.

Fractals, always amusing.

Fractal design may prove as good of a way of shrinking an antenna as
any other. Its just pure BS to think it is going to let you make a
smaller antenna with the same gain as the full size antenna it was
derived from. It is Mega BS to think that you are going to shrink the
antenna and achive gain because of anything the fractals will
contribute.

Jimmie

Log-Periodic Antenna Design
 

Richard Clark wrote:
For the inverse (starting with the practical instead of the
mathematical model) one very simple test:
give the mathematical model for a single fractal
antenna specifically resonant on each frequency:
1.85MHz;
3.8MHz;
7.15MHz;
10.13MHz;
14.15MHz;
18.11MHz;
21.2MHz;
24.93MHz;
28.5MHz,
to within the margins of any Ham band represented by the single
frequency offered.

Since fractal antennas are finding practical applications
when etched on a PC board, your discussion is about as
moot at a 160m rotatable Yagi proving that rotatable Yagis
are not feasible.
--
73, Cecil http://www.w5dxp.com

Log-Periodic Antenna Design
 

On Mon, 24 Nov 2008 17:10:00 -0600, Cecil Moore
wrote:

Since fractal antennas are finding practical applications
when etched on a PC board

Like I said - nothing predictable, no math model, etc. etc. etc.

Imagine, an antenna on a PC board - the miracle of the 3rd Millennium!

Log-Periodic Antenna Design
 

"Rich Grise" wrote in message
...
Or, does anyone have a UHF-TV log-periodic design that they'd share? :-)

Thanks,
Rich

Lo and behold, here is one http://tinyurl.com/665r5a but it's a throw-back
to a simpler time when the HP42S calculator was an engineer's prized tool.
If you have a 42S, punch it in and use it. Otherwise, this is mainly a
learning tool to show how simple the calculations are. I think this design
could be put onto a Lotus123 calculating spread sheet where all the output
data windows would suddenly by filled up upon entering the needed input
data.

Log-Periodic Antenna Design
 

Jim Lux wrote:
. . .
http://ieeexplore.ieee.org/Xplore/lo...number=1610336


If you are a member of IEEE, you can access this paper:

Multiband behavior of wideband Sierpinski fractal bow-tie antenna
Yamini, A.H.; Soleimani, M.
Microwave Conference, 2005 European
Volume 3, Issue , 4-6 Oct. 2005 Page(s): 4 pp. -
Digital Object Identifier 10.1109/EUMC.2005.1610336

interesting paper..
. . .

I think you have to be a member of the Microwave Theory & Techniques
Society to it. I'm a member of the IEEE and several of its Societies,
but not that one, and I'm denied access to the paper. Too bad it wasn't
published in Ant & Prop.

Roy Lewallen, W7EL

Log-Periodic Antenna Design
 

"Chuck Olson" wrote in message
...

"Rich Grise" wrote in message
...
Or, does anyone have a UHF-TV log-periodic design that they'd share? :-)

Thanks,
Rich

Lo and behold, here is one http://tinyurl.com/665r5a but it's a throw-back
to a simpler time when the HP42S calculator was an engineer's prized tool.
If you have a 42S, punch it in and use it. Otherwise, this is mainly a
learning tool to show how simple the calculations are. I think this design
could be put onto a Lotus123 calculating spread sheet where all the output
data windows would suddenly by filled up upon entering the needed input
data.

Sorry I didn't fully describe how to get the file. It's a Word document, so
the URL above takes you to a page where you can choose "download", and then
you can open it with Microsoft Word.

Chuck W6PKP

Log-Periodic Antenna Design
 

"Chuck Olson" wrote in message ...

"Rich Grise" wrote in message
...
Or, does anyone have a UHF-TV log-periodic design that they'd share? :-)

Thanks,
Rich

Lo and behold, here is one http://tinyurl.com/665r5a but it's a throw-back
to a simpler time when the HP42S calculator was an engineer's prized tool.
If you have a 42S, punch it in and use it. Otherwise, this is mainly a
learning tool to show how simple the calculations are. I think this design
could be put onto a Lotus123 calculating spread sheet where all the output
data windows would suddenly by filled up upon entering the needed input
data.


I'm really disappointed in the comcast customer's website - - I tried to access the program later in the evening and found it required I sign in - - even though I specified the file to be "public". Let me know if you have trouble getting the file. I would appreciate any recommendation for a better way to access the Word document than the use of this comcast facility.