GregS wrote:

Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band.
It could be improved by making it a full fractal.

greg

That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?

Roy Lewallen, W7EL

On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote:
GregS wrote:

Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide
band. It could be improved by making it a full fractal.

That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?


http://www.google.com/search?hl=en&q...earch&aq=f&oq=

Hope This Helps!
Rich

Rich Grise wrote:
On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote:
GregS wrote:
Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide
band. It could be improved by making it a full fractal.
That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?


http://www.google.com/search?hl=en&q...earch&aq=f&oq=

Hope This Helps!
Rich

Sorry, it doesn't. Among the claims, trolls for investors, and
testimonials, where is the quantitative data showing that a fractal
antenna is in any way better than a bow tie, in what ways, and how much?
In other words, exactly where is the evidence on which you based your
statement?

Roy Lewallen, W7EL

Roy Lewallen wrote:
Sorry, it doesn't. Among the claims, trolls for investors, and
testimonials, where is the quantitative data showing that a fractal
antenna is in any way better than a bow tie, in what ways, and how much?
In other words, exactly where is the evidence on which you based your
statement?

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
--
73, Cecil http://www.w5dxp.com, IEEE

In article tonline, Roy Lewallen wrote:


Rich Grise wrote:
On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote:
GregS wrote:
Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide
band. It could be improved by making it a full fractal.
That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?



http://www.google.com/search?hl=en&q...oogle+ Search
&aq=f&oq=

Hope This Helps!
Rich

Sorry, it doesn't. Among the claims, trolls for investors, and
testimonials, where is the quantitative data showing that a fractal
antenna is in any way better than a bow tie, in what ways, and how much?
In other words, exactly where is the evidence on which you based your
statement?

Roy Lewallen, W7EL

I don't have data. I think the home made TV antenna in the video, is very much like a bow tie,
and could have better bandwidth by making the elements different lengths. The gain factor
is going to be narrow band since the feed length is constant. I would have also used 12ga
copperweld or solid copper. You can also get closer to fractal by using many more different
sized elements.

greg

On Thu, 20 Nov 2008 16:58:46 -0800, Roy Lewallen wrote:
Rich Grise wrote:
On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote:
GregS wrote:
Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide
band. It could be improved by making it a full fractal.
That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?

http://www.google.com/search?hl=en&q...earch&aq=f&oq=

Sorry, it doesn't. Among the claims, trolls for investors, and
testimonials, where is the quantitative data showing that a fractal
antenna is in any way better than a bow tie, in what ways, and how much?
In other words, exactly where is the evidence on which you based your
statement?

The only "evidence" I have is a "testimonial" by the guy who invented it,
on some PBS show. And they claimed that that's how they pack so much
antenna into a box the size of your thumb. ;-)

And, having a passing familiarity with fractals, it just sounds eminently
plausible to me. :-)

Cheers!
Rich

On Fri, 21 Nov 2008 00:51:28 GMT, Rich Grise wrote:

On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote:
GregS wrote:

Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide
band. It could be improved by making it a full fractal.

That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?


http://www.google.com/search?hl=en&q...earch&aq=f&oq=

Hope This Helps!
Rich


Hi Rich,

Tacking the new-age term of "fractal" to antenna does not
automatically bring:
1. Widebandedness;
2. Gain;
3. Small size.

The link above fairly confirms it in the fog of offering.

I could expand upon this - but the interest of those who become
suddenly engaged with the topic rarely translates into a meaningful
discussion, and never leads to an actual construction.

73's
Richard Clark, KB7QHC

On 19 Nov, 22:45, Rich Grise wrote:
My current UHF antenna is a 14" Radio Shack clip lead clipped from the
center of my coax to the venetian blind. I have to hand-adjust it
for the channel, weather conditions, phase of the moon, etc. I can
do this because I can _see_ an indication of signal strength.

Well, with this new Fascist "No More Free TV" crap, I'm gonna need
a real UHF antenna. My budget is exceedingly limited, but I have
a supply of materials (GTAW filler rod, with some coppery-colored
coating, so it solders like a dream, and is as stiff as piano wire)
to build an antenna with.

But I've been searching the web for some weeks now, and I can't
seem to find any kind of formula, except there was this program
I downloaded - LPDA.EXE, which runs on DOS. Unfortunately, it's
in Russian or Polish or Uzbekistani - one of those East Yurp
languages. Here's a screen snap:http://mysite.verizon.net/richgrise/...rog-Output.gif

Which I went through pretty much by-guess-and-by-gosh - can
anybody read that stuff?

There are a lot of factors I don't know about, like "Tau", and
all of the specific designs on the web are flat - something is
telling me I want one of those pyramid-shaped ones, but I really
don't know the difference (between that and flat) - it's probably
something to do with bandwidth or F/B ratio or whatever.

My local library has no ARRL Antenna Book (!), and did I mention
I have a seriously limited budget?

So, how do I pursue this? It'd be nice to have a program that will
calculate the whole thing for me, but am I dreaming? If I want to
send myself to Log-Periodic School, where should I start?

Or, does anyone have a UHF-TV log-periodic design that they'd share? :-)

Thanks,
Rich

I have used the procedure in the following paper:
http://www.urel.feec.vutbr.cz/ra2008...tracts/116.pdf

I slightly modified the design (e.g. I used several different
diameters for the elements), but basically I used the same formulae.
I did not use their formula for deciding the right spacing between the
support tubes to get the right characteristic impedance, because I
suspect that maybe it is only valid over a limited range of spacing.
Instead, I measured the characteristic impedance of just the tubes
with no elements attached on a VNA that could plot impedance vs
distance in a sort of TDR mode, and I adjusted the spacing until it
was right. I epoxied some very small (roughly 1mm cube) spacers
between the support tubes to keep the distance right, once it was
adjusted properly. It is important that the space between the support
tubes is mostly filled with air, not epoxy or any other dielectric,
because the wave needs to propagate at the right speed between the
tubes so that the elements are fed in the right relative phase, and
this won't happen if there is something with a higher dielectric
constant in there. I used those brass tubes that you can get in hobby
shops, but unfortunately brass is fairly resistive and I did not
silver plate it. I would have used aluminium if it were easier to
solder in a reliable way.

The finished antenna had a good return loss over the desired frequency
range (sorry, can't remember the numbers) and it did the job for which
it was intended although I don't have a measured gain value etc.
because I don't have an antenna range.

I have a spreadsheet for calculating the element lengths (in
Openoffice.org format) if you are interested.

Chris

"Rich Grise" wrote in message
news
My current UHF antenna is a 14" Radio Shack clip lead clipped from the
center of my coax to the venetian blind. I have to hand-adjust it
for the channel, weather conditions, phase of the moon, etc. I can
do this because I can _see_ an indication of signal strength.

Well, with this new Fascist "No More Free TV" crap, I'm gonna need
a real UHF antenna. My budget is exceedingly limited, but I have
a supply of materials (GTAW filler rod, with some coppery-colored
coating, so it solders like a dream, and is as stiff as piano wire)
to build an antenna with.

It may not take too much antenna. I picked up one of the converter boxes
and hooked it to a 432 mhz beam at 70 feet and got 21 stations on the auto
tune. Then to a 9 element M2 2 meter bem and it picked up 29 stations.
This was at the end of about 130 feet of low loss rg-8 size coax and then 25
feet of rg-6.
Several of the stations were the same transmitter,but differant chanels on
the TV.

"Ralph Mowery" wrote in message
...

snip

It may not take too much antenna.

It doesn't.

I have two converter boxes, one Magnavox, one Zenith. I just now tried my
local stations with them using a straight 24-inch alligator clip lead as the
antenna. Location is a residential garage in the San Diego suburbs. Stucco
walls, metal garage door closed, overhead fluorescent lights on.
Transmitters in three different locations.

All the UHF locals came in, 10 transmitters with about twenty total
programs. The one low-power VHF did not. Looping the clip lead back and
clipping the end to the F-connector produced about the same results. (Lost
one TJ station.)

When I "upgraded" to a POS 2-bay bowtie in the rafters (about 8 feet up),
all eleven locals came in, plus KCBS from LA . On the Zenith box, arguably
a better unit, I got two more LA channels, although one of them had some
intermittent freezing and tiling.

If even poor antennas work well, why all the whining?

"Sal"
(KD6VKW)