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Fractal antennas
Hello all,
The last days I was searching for more info o how to build fratal antennas on the web. But besides lots of links to fractenna.com and a few powerpoint slides I found nothing. Has anyone sucessfully build such an antenna for HF? Is anyone using it? Kind regards, Jan, ON5DOA |
"Jan Van Belle" wrote in message ... Hello all, The last days I was searching for more info o how to build fratal antennas on the web. But besides lots of links to fractenna.com and a few powerpoint slides I found nothing. Has anyone sucessfully build such an antenna for HF? Is anyone using it? Kind regards, Jan, ON5DOA ================================== Fractal antennas at HF stay up long enough to discover they don't work any better than multi-band dipoles. Or simple verticals. The radiation patterns, of course, are somewhat modified but not enough to make any practical difference. Particularly as they are not rotatable. What's the point in having a rotable antenna which from one band to another is omni-directional? Efficiency-wise you can't improve on 95 to 98 percent anyway. All this can be deduced just by looking at them. Like conventional antennas they are just a few wires in space at various angles. How can an additional bend in a wire have a significant effect? But as you are a confirmed experimenter I guess I am unable to discourage you from your next project. I'm sorry I do not have any antenna wire dimensions readily at hand. As for me, in my time I have had experience with a variety of dogs-hind-leg fractals without being aware of it. Is an inverted-L a first-order fractal? ---- Reg, G4FGQ |
Reg Edwards wrote:
Fractal antennas at HF stay up long enough to discover they don't work any better than multi-band dipoles. Or simple verticals. The radiation patterns, of course, are somewhat modified but not enough to make any practical difference. Particularly as they are not rotatable. What's the point in having a rotable antenna which from one band to another is omni-directional? Efficiency-wise you can't improve on 95 to 98 percent anyway. All this can be deduced just by looking at them. Like conventional antennas they are just a few wires in space at various angles. How can an additional bend in a wire have a significant effect? But as you are a confirmed experimenter I guess I am unable to discourage you from your next project. I'm sorry I do not have any antenna wire dimensions readily at hand. As for me, in my time I have had experience with a variety of dogs-hind-leg fractals without being aware of it. Is an inverted-L a first-order fractal? ---- Reg, G4FGQ OK, I get your point. If you've already have a complete set of antennas, it will probably be no use of building such a new one. From my point of view, fractal antennas seem to be MUCH smaller than the full size ones. So it would be an ideal solution if you live on an appartment or don't have the permission to place a full-sized antenna somewhere. So for me, it would just be a better solution than 2 times 5m of wire with a balun in the middle. Jan, ON5DOA |
Reg, G4FGQ, dismisses fractal antennas as not improving on the
efficiency of radiation, but that may not be the intent. Kraus, in "Antennas" says: "They also provide new insights into antenna and array design----. ----Interestingly, the self-repeating different-size structure of a log-periodic antenna qualifies it as a fractal form." Best regards, Richard Harrison, KB5WZI |
Jan, Very simply, they don't work worth a 'hoot'. If you lack antenna space a 'fractal' antenna is not the solution. Sorry... 'Doc |
'Doc wrote in message ...
Jan, Very simply, they don't work worth a 'hoot'. If you lack antenna space a 'fractal' antenna is not the solution. Sorry... 'Doc I wouldn't invest in an Isotron, either. Here is a link to some practical advice - - http://www.alphalink.com.au/~parkerp/nooct97.htm Speaking of "frac" tennas, here is a recent paper on the subject of small antenna technology, which does not mention fractals (what happened to that "Disruptive Technology" - - did the "paradigm shift" again?) (Looong url) http://users.ece.gatech.edu/~durgin/...r%20Better.pdf |
'Doc wrote:
Very simply, they don't work worth a 'hoot'. If you lack antenna space a 'fractal' antenna is not the solution. Sorry... As Richard Harrison pointed out, a log-periodic is a fractal antenna, by definition. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Tue, 11 May 2004 11:59:10 +0200, Jan Van Belle
wrote: Hello all, The last days I was searching for more info o how to build fratal antennas on the web. But besides lots of links to fractenna.com and a few powerpoint slides I found nothing. Has anyone sucessfully build such an antenna for HF? Is anyone using it? Kind regards, Jan, ON5DOA Hi Jan, The reason you see such a void of examples is because of your very question: who has built one? This question above is the one that follows: which one to build? And this question above is the one that follows: what limitations do I have? or: what qualities do I want? Your question is raised here on sporadic occasions, and the poster NEVER returns to report a successful outcome. This is not due to lack of information. For such (the largest compilation in the world) visit: http://www.qsl.net/kb7qhc/antenna/fractal/index.htm You should immediately notice that the first impediment is found in the very nature of fractal shapes. Do you want gain? Seems not, you do not describe having a large enough space to do that. Do you want multi banded resonances in a small space? Probably, but you will find very, very few examples worth the effort (frankly none). In all likelihood you would need a tuner, and if you had a tuner, you should skip the complication of this academic trash. In open competition between an Amateur and the professional fractal builder, the professional lost against 6 designs that trounced the best professional fractal on the basis of gain for the smallest footprint. That is to say, all seven antennas were bound within a prescribed "small" area (such as you describe), and the fractal came in dead last. 73's Richard Clark, KB7QHC |
Cecil, And as you know, that wasn't exactly what he asked about. Was it? 'Doc |
"Jan Van Belle" wrote in message ... Hello all, The last days I was searching for more info o how to build fratal antennas on the web. But besides lots of links to fractenna.com and a few powerpoint slides I found nothing. Has anyone sucessfully build such an antenna for HF? Is anyone using it? Kind regards, Jan, ON5DOA A fractal antenna is just another antenna that uses lumped inductance to shrink the size of the antenna along with destroying the radiation pattern. The arrl has a nice explantion of why antennas radiate on their web site. Aplly this info to fractals and small coils and it is easy to see why they dont work worth a hoot. |
Richard Clark wrote:
In open competition between an Amateur and the professional fractal builder, the professional lost against 6 designs that trounced the best professional fractal on the basis of gain for the smallest footprint. That is to say, all seven antennas were bound within a prescribed "small" area (such as you describe), and the fractal came in dead last. 73's Richard Clark, KB7QHC Sorry, I've had a little accident while sporting and since I've only a quick connection at the QRL, I couldn't check my mail and this newsgroup. OK, thanx for the explanation. It seems I can leave it now! I thought it would be a nice solution: a big amount of wire on a small area. But if performance is even lower as other antennas and I can only come out on QRP (I've got an FT-817) it is probably not the thing to choose for in first instance. Thanks all for the replies, links, etc. !! 73's de Jan, ON5DOA |
"Jimmy" wrote in message .com...
"Jan Van Belle" wrote in message ... Hello all, The last days I was searching for more info o how to build fratal antennas on the web. But besides lots of links to fractenna.com and a few powerpoint slides I found nothing. Has anyone sucessfully build such an antenna for HF? Is anyone using it? Kind regards, Jan, ON5DOA A fractal antenna is just another antenna that uses lumped inductance to shrink the size of the antenna along with destroying the radiation pattern. The arrl has a nice explantion of why antennas radiate on their web site. Aplly this info to fractals and small coils and it is easy to see why they dont work worth a hoot. An 18 page paper entitled FRACTAL ANTENNAS Introduction to fractal technology and presentation of a fractal antenna adaptable to anytransmitting frequency - The "FRACTENT" By Werner Hödlmayr, DL6NDJ January 2004 Can be downloaded at www.antenneX.com His conclusion: "The attentive reader will note that the spacing of resonant frequencies in a fractal structure is logarithmic, whereas most of the HF amateur bands follow a linear sequence. This means that the antenna structure has to have a scaling which follows the same logarithmic law. To build such an antenna is a challenge asking for a professional simulation program (which allows more than 10,000 segments) and very much perseverance." Interesting references: [2] Jaggard, D.L. (1990): On Fractal Electrodynamics. In Recent Advances in Electromagnetic Theory, H.N. Kritikos and D.L. Jaggard, editors, Springer-Verlag, New York. [3] Jaggard, D.L. (1991): Fractal Electrodynamics and Modeling. In Directions in Electromagnetic Wave Modeling. Plenum Publishing Co., New York, 435-446 |
On 26 May 2004 06:29:27 -0700, (k4wge) wrote:
D.L.Jaggard's webpage: http://www.seas.upenn.edu/~jaggard/ Too bad he doesn't have a patent pending or he would be the father of fractal antennas. ;-) Dare we wonder that these fractal children are legitimate? They sure are *******s to build and they work like a dead-beat brother-in-law. 73's Richard Clark, KB7QHC |
william ewald wrote:
"Zagi antenna construction and measurements A zagi antenna is made from serrated wire or plate. It has reduced dimension because of the slow wave characteristics of the periodic structure. The student is asked to construct and measure a Zagi for the 225MHz digital broadcast band in the UK. " Stand by - I am inventing a zig-zagi. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
k4wge wrote:
An 18 page paper entitled FRACTAL ANTENNAS Introduction to fractal technology and presentation of a fractal antenna adaptable to anytransmitting frequency - The "FRACTENT" By Werner Hödlmayr, DL6NDJ January 2004 Can be downloaded at www.antenneX.com in fact, that was the article that raised all the questions ;-) I found it interesting, but wanted to know if hams are really using it! Kind regards, Jan, ON5DOA |
Cecil Moore wrote in message ...
william ewald wrote: "Zagi antenna construction and measurements A zagi antenna is made from serrated wire or plate. It has reduced dimension because of the slow wave characteristics of the periodic structure. The student is asked to construct and measure a Zagi for the 225MHz digital broadcast band in the UK. " Stand by - I am inventing a zig-zagi. Chip already patented it. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Jan Van Belle wrote in message ...
I found it interesting, but wanted to know if hams are really using it! Kind regards, Jan, ON5DOA Have you looked at the W0FMS page at http://www.fredspinner.com/W0FMS/fractant/ Fred says, "The purpose of this web page is to further explain the details of the rather contraversial Fractal Antenna. This antenna uses a fractal shape to load a radiating element, allowing, according to Nathan (Chip) Cohen, N1IR 2x to 4x reduction in size with little loss in gain and/or F/B. I haven't tried this antenna yet, which is patent pending from Fractal Antenna Systems, Inc. (Fractenna), so I claim nothing else than to have deciphered the (IMHO) rather cryptic building instructions in the http://www.fractenna.com/ham/hampage1.html page describing a 10-m 2 element quad fractal antenna. In order to avoid potental criticism, I am stating for the record that the instructions on the site are adequate for assembling this antenna. I am also stating that for most, it is very hard to understand these directions without a starting point of reference. It took me a couple of hours to figure it out, and I'm a EE... " |
in fact, that was the article that raised all the questions ;-)
I found it interesting, but wanted to know if hams are really using it! Kind regards, Jan, ON5DOA Not to my knowledge, Jan. The presently and easily available (that is, free) info on fractal antennas for hams is poor in content and often factually inaccurate, in my opinion, and this is likely to remain so. In the world we live in today, this makes a lot of a sense in its own quirky fashion. Commercial uses are a different story, however. Of course, that's not what this NG is about. When hams switch to software radios in a big way then fractal antennas targeted to hams might be worth making more widely known. With some luck, they'll be a few of us 'hams' left then! 73, Chip N1IR |
Fractenna wrote:
When hams switch to software radios in a big way then fractal antennas targeted to hams might be worth making more widely known. With some luck, they'll be a few of us 'hams' left then! Maybe this is a naive question, but how does an antenna, fractal or otherwise, know what kind of transmitter is driving it? Why are software radios more suited to this design? vy 73 Andy, M1EBV |
Maybe this is a naive question, but how does an antenna, fractal or
otherwise, know what kind of transmitter is driving it? Why are software radios more suited to this design? vy 73 Andy, M1EBV True frequency and waveform agility is the goal in SDR . Wideband, or controlled multiband, is needed. Ham requirements are well met at present with a variety of antenna designs that are nearly periodic in a fairly narrow frequency coverage, a fairly easy problem to solve. 73, Chip N1iR |
Translation: fractured antennas are horse****.
"Fractenna" wrote in message news:20040609122135.15248.00000404@mb- True frequency and waveform agility is the goal in SDR . Wideband, or controlled multiband, is needed. Ham requirements are well met at present with a variety of antenna designs that are nearly periodic in a fairly narrow frequency coverage, a fairly easy problem to solve. 73, Chip N1iR |
On Sat, 12 Jun 2004 18:45:30 -0700, "CW"
wrote: Translation: fractured antennas are horse****. Unfortunately, that association is an aspersion upon horse****. ;-) |
LOL!
"Richard Clark" wrote in message ... On Sat, 12 Jun 2004 18:45:30 -0700, "CW" wrote: Translation: fractured antennas are horse****. Unfortunately, that association is an aspersion upon horse****. ;-) |
In message , Richard Clark
writes On Sat, 12 Jun 2004 18:45:30 -0700, "CW" wrote: Translation: fractured antennas are horse****. Unfortunately, that association is an aspersion upon horse****. ;-) Not a good analogy. Horse**** can be quite useful (ask any organic gardener). Ian. -- |
Ian Jackson wrote:
In message , Richard Clark writes On Sat, 12 Jun 2004 18:45:30 -0700, "CW" wrote: Translation: fractured antennas are horse****. Unfortunately, that association is an aspersion upon horse****. ;-) Not a good analogy. Horse**** can be quite useful (ask any organic gardener). Ian. Equine Excrement is a tad difficult for some gardening. IT has lots of plant material that needs a good bit of time to compost correctly. Mushroom growers love it, tho'. - Mike KB3EIA - |
Ian wrote,
In message , Richard Clark writes On Sat, 12 Jun 2004 18:45:30 -0700, "CW" wrote: Translation: fractured antennas are horse****. Unfortunately, that association is an aspersion upon horse****. ;-) Not a good analogy. Horse**** can be quite useful (ask any organic gardener). Ian. -- Right. It's absolutely indispensable to cowboys and politicians. 73, Tom Donaly, KA6RUH |
A consortium to investigate fractal electrodynamics theory (FET) has a
webpage at this URL. http://www.tsc.upc.es/fractalcoms/ From the site: "There is [a] potential limitation of fractal microwave devices that must be investigated: the loss efficiency. It has been shown that in fractal geometries electromagnetic fields and currents concentrate into very small regions. Since the power loss due to Joule effect is proportional to the square of the electric current density integrated along the device surface, current concentration in small areas produce much larger power losses than more uniform current distributions. This effect may result in antennas having much lower gain... " The articles and links are very interesting. |
A consortium to investigate fractal electrodynamics theory (FET) has a
webpage at this URL. http://www.tsc.upc.es/fractalcoms/ From the site: "There is [a] potential limitation of fractal microwave devices that must be investigated: the loss efficiency. It has been shown that in fractal geometries electromagnetic fields and currents concentrate into very small regions. Since the power loss due to Joule effect is proportional to the square of the electric current density integrated along the device surface, current concentration in small areas produce much larger power losses than more uniform current distributions. This effect may result in antennas having much lower gain... " The articles and links are very interesting. |
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