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 Interesting Fractal Antenna Development 
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Post Interesting Fractal Antenna Development
This would seem to be of most interest for the Microwave user, as issues of scale would come into play at lower frequencies.
However, the effect on bandwidth is impressive.

http://www.youtube.com/watch?v=QWd0nEXF ... _embedded#!

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Wed Nov 24, 2010 1:58 pm
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 Interesting Fractal Antenna Development 
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arn't these type of antennas used in some mobile phones ?? i read a little on them ages ago but its all gone now..

billy

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Wed Nov 24, 2010 2:07 pm
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 Interesting Fractal Antenna Development 
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I believe so, although there have been fractal antenna designs from 10m to 3cm.

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Wed Nov 24, 2010 2:26 pm
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 Interesting Fractal Antenna Development 
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The increased bandwidth is a disadvantage as you want the antenna to be a tuned circuit that rejects unwanted frequencies.
With a wide bandwidth high level, out of band signals, could have an adverse effect on the RX front end.
In addition I can't think of any application for vertically polarised, omni directional, antennas at microwave frequencies.
So an interesting concept, for cellphone type applications, but I can't see a use for amateur radio.

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Wed Nov 24, 2010 2:41 pm
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 Interesting Fractal Antenna Development 
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my mate is a pc and phone geek and he asked me to find out about fractal antennas for him which i did. i think wikipedia was quite a good info source if i remember . im sure i read or my mate had that these fractal antennas can be "grown" on micro chips.. thats about all i can remember on the subject and im not sure if that little bit is correct..

billy

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Wed Nov 24, 2010 2:54 pm
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 Interesting Fractal Antenna Development 
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Remember this is primarily focused on cellular use, so quad-band phones operate from 900mhz up to 1800Mhz or more.
Hence the desire for bandwidth.
I wouldn't sniff at the extra 3db gain though, not easy to accomplish without lengthening the antenna.

Some directional antennas on 23cm have quite a narrow bandwidth, presumably this technology applied to say the driven element might be interesting.

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Wed Nov 24, 2010 3:15 pm
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There are also a new generation of WiFi-N routers appearing that cover 2.4Ghz up to 5Ghz, this technology would greatly benefit that application.

Believe it or not Tony, there are stations that use vertically polarised omni directional antennas at 23cm and above, not many I grant you,
but they are there.

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Wed Nov 24, 2010 3:19 pm
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 Interesting Fractal Antenna Development 
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Post Re: Interesting Fractal Antenna Development
G7TOK wrote:
There are also a new generation of WiFi-N routers appearing that cover 2.4Ghz up to 5Ghz, this technology would greatly benefit that application.

As I said, interesting as a concept , for cellphone, WiFi and similar applications but no amateur applications I can see.
G7TOK wrote:
Believe it or not Tony, there are stations that use vertically polarised omni directional antennas at 23cm and above, not many I grant you,
but they are there.

Very few, I think you will find, on 23cm and none that I'm aware of above that.
Unless you can can enlighten me as I'm a beginner when it comes to above 1296MHz.

3dB, or more, omnidirectional, gain is easily achieved by using a colinear configuration for vertical polarisation or a cloverleaf, stacked halos or Alford Slot configuration for horizontal polarisation.
23cm TV repeaters and, as far as I know, voice repeaters tend to use Alford Slot antennas.

The narrow bandwidth, and beamwidth, of a Yagi is a desired quality.

For wider bandwidths a log-periodic is generally used.

Personally I would not go down that route but would opt for single band antennas on a common boom in order to maintain a high Q on each band.
A log-periodic is useful as a general purpose RX antenna but not as a serious DX TX antenna.

Cheers

Tony

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Wed Nov 24, 2010 4:04 pm
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Quote:
3dB, or more, omnidirectional, gain is easily achieved by using a colinear configuration for vertical polarisation or a cloverleaf, stacked halos or Alford Slot configuration for horizontal polarisation.
23cm TV repeaters and, as far as I know, voice repeaters tend to use Alford Slot antennas.


True, but all generally require a requisite increase in length, this does not.
It just looks like a 'fatter' radiator.

As far as i can see, 3dB for no increase in length, not bad at all.

Where operation requires the lowest possible profile it could be very valuable.
I am also presuming that the fractal method would also work for horizontally polarised elements.
Presumably the technology could find it's way into many antenna types, not just vertical monopoles.

I'm sure you wouldn't turn your nose up at an extra 3dB of gain for the same size antenna ?

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Wed Nov 24, 2010 4:17 pm
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