Very interesting presentation. Glad to see you continuing your good works! The possibilities are seemingly endless for this invention! 73 OM
This is really cool. I had no idea I could use fractals in amateur radio. Way back I did research on space-filling curves for dimensionality reduction in database searches (4 patents!) and I'm always on the lookout for random applications of this one very specific, very weird bit of expertise. I mean, I've done some really oddball stuff, including Hilbert curve skirting for my porch: So basically I'm nuts, and specifically nuts about this kind of stuff. A while back I asked myself if a Hilbert curve would make any sense for an antenna, but it looks very much like it would be a terrible radiator with all the parallel bits canceling out. However, it might work excellently as a compact radial or counterpoise. It would be pretty cool to make a vertical for 20m with four long radials laid out Hilbert-style on a 4' square, so it can be mounted nice and high.
Yep. That Hilbert is a lousy radiator, but pretty good counterpoise. I did fractal 'radials' approaching 3 decades ago, and published in Comm Quart on that in, oh 1996. Its an interesting question if switching to such 'electrically long, physically small' radials benefits hams. I tend to believe so, because having a compact radial system indeed let's you get a 20m monopole (as your example) higher up, and thus lowers the launch angle. It certainly is less problematic to deal with than a vertical dipole(center fed). I have to confess (as I have many times) that I've have been ping ponged on ham antennas(for others) thru the years and am somewhat reluctant to jump back in at the moment. But if you enjoy experimenting I heartedly agree and encourage you to have fun in the discovery. You can email me if you get stuck. Have fun!
Here's what I said about Hilbert curves, first posted in 2002(man, time is flying:-( Q: I experimented with a Hilbert curve fractal antenna and tested it, based on some claims about uses for mobile and handheld uses. It small but works very poorly as an antenna. Why? A: There are a near infinite number of possible fractal antennas. While all of them share certain attributes, such as shrinkage; broad bandedness at higher resonances; and so on, only a very few are good or great antennas for a particular application or frequency. Many researchers have not taken the trouble to consider the issue at hand: 'what problem is being solved'? Instead, they often choose a well-known fractal geometric design and report its RF properties. This served the field well in its infancy, but not its present maturity. That’s why we’ve spent over 30 man-years of manual effort and then optimization-directed searching to find the very best fractal antennas for desired applications-- with great success. We are indeed practical: we enjoy solving application problems. We have resisted publishing fractal antenna taxonomy as this fails to contribute to the true science of fractal antennas, and is worthless in exploring practical novelty from an inventive sense. In other words, it doesn’t benefit our customers. We do not publish articles at the ‘minimum publishable unit’. All of our publications have exposed basic insight into fractal antennas and how they work. For small sized antennas, the Hilbert curve doesn’t make the cut. At higher iterations it has the unusual attribute of being its own’ Faraday shield’ and is a remarkably poor radiator. Its radiation cancels in the far field. Peano curves are close behind as poor, small radiators. A better description might be as ‘fractal resonators’; see US patent 6452553. You may wish to ask your citation source why the Hilbert curve was chosen and described as a useful antenna and pose the question: what was the problem to be solved?
I've gotten over a dozen emails regarding my age, in the last week. Yep. I am almost 63, and the photo on the OP was taken Dec 22, 2017. Good lighting. Clean living via metamucil. I am astounded that several people think I am 'faking my age'. Let me make one thing very clear: NO ONE OVER 60 WANTS TO BE OVER 60! No one would ever claim to be over 60 if they were, for example, 45. You have to work at what you have left. That's what I am doing, and I hope you are doing so also I was first licensed at age 11 as WN1HBX. I then traded that horrible novice call for a slightly less horrible general call: WA1JHQ. Here I am with K1IMP (my 'Elmer') in 1968 in my bedroom 'shack'... The occasion was my 'Bar Mitzvah', hence the jackets. The photo is 50 years old. I imagine you can dig out the old callbooks to 'verify' my age. BTW I am holding 'Sputnik' (in the OP photo) because it looks like a Christmas ornament. The replica is being used for radar cross section measurements: a sphere is invariant in its RCS with frequency. That's the context to that photo. Good times! 73 Chip W1YW
Am I correct in thinking the federal government saw this as a national security secret and said 'shut up' until further notice? Btw - congratulations. /73
No. The USG issued the patent(s). They didn't slip through. But if you open Pandora's Box, whether you want to or not, you better look long and hard for Elpis in a tangible way. Wishin' ain't doin'. And inventors have to take some responsibility for preventing the downsides of their inventions. I've had 15 years to think about Pandora and her freakin' box. I sleep well at night. And thanks for the kind wishes
Hi, So I started playing with the idea in simulation, using my old Hilbert curve code. Check this out: I guess that's hard to read, but it's a 1/4 wave vertical for 40m, actually a bit under a 1/4 wave (30 feet), mounted 20 feet off the ground. The radial is replaced with one (2-D) Hilbert curve approximating polygon, with an identical copy at the top. I could erect something like this on my cheapo-depot mast. This is fed at the base, but as you can see it seems to put the current maximum in the middle. Basically it's more like a vertical dipole in terms of wire length, but the effect of the Hilbert curve seems to give a good current distribution even as it is off-center fed. CocoaNec gives this for feedpoint impedance: (SWR, reactance, resistance, directivity, gain dBi) 7.00 ---> (2.57, -50.08, 52.28, 0.00, 2.06) 7.05 ---> (1.87, -32.82, 54.03, 0.00, 2.05) 7.10 ---> (1.36, -15.28, 55.87, 0.01, 2.05) 7.15 ---> (1.17, 2.57, 57.81, 0.01, 2.04) 7.20 ---> (1.52, 20.76, 59.85, 0.02, 2.04) 7.25 ---> (2.06, 39.31, 62.01, 0.02, 2.04) 7.30 ---> (2.76, 58.24, 64.29, 0.02, 2.03) Ignore the gain numbers: I've found that CocoaNEC gives numbers that don't agree with other programs, and I only really trust them in relative terms. The simulated SWR is "three to shining three" across the band, though.
Fiber supplementation is too harsh for me; I prefer the taste of prune juice now! Don't forget to regularly work up a sweat and keep an appropriate caloric balance too. I learned about fractals in 1987 from the prize winning book "Chaos: Making a New Science" by James Gleick. It was and still is a page-turner for me. Chip, your Zed bio indicates the first fractal antenna appeared about a year later in 1988. When, who, how did you first learn about fractal geometry? Was their a particular special motivation or singular moment of inspiration in regards to applying fractals to antennas during your early radio activities? 73 de John - WØPV
I had read 'Objets Fractals' in, oh 1982? I found it in the french section of a book store in Ithaca. Bizarrely, I bought it to practice my french. I had run across Mandelbrot in an amusing situation many years earlier...I recognized the name. In Yiddish it refers to almond bread, so its not hard to remember. That story is more amusing with beverage present. He was talking about turbulence then. I never made an antenna connection. Back then. I was trying to 'think in French.' Must have turned one side of my brain off while using the other! I saw Mandelbrot again in Summer 1987. This time he was preaching a fractals gospel. Here's that story...2008 interview: Another big moment for me, later... 1989?.... was when I did a literature search and saw nothing on elements made of fractals. I also had a distinct revelation at the Boston Public library doing a prior art patent search with the microfiche. It was humbling. Empty set. You rarely see that in patent searches. I had been saving up my slim savings to go out on dates. After that, for a while, the money went to the MIT Flea for junk, as in 'junk box'. So fractals turned me into a celibate priest for , well, awhile(or so it seemed)! Much of my early ham measurement work including aluminum grounding wire from Radio Shack (great for bending fractals) and several TR-22 2M rigs, MFJ SWR analyzers, a coveted precision attenuator. At one point I built a vertical 2M range. KLUDGE CITY! BTW I had made some money on Wall Street earlier, but that quickly got diverted for supporting relatives. No regrets. Remember the crash of Oct 87.....
I know the picture below is a bit corny, but I have been getting emails asking for something to show that I used ham radio to invent fractal antennas. Well, the Comm Quart articles are virtually all OTA ham radio results. And this photo (understandably one of my faves) is from Oct 1994 at WK1O's QTH. That's 24 years ago (!) I am clutching a fractal antenna for 2M (actually part of a fractal Yagi), made with Radio Shack aluminum ground wire. That's an MFJ SWR analyzer in my hand. My 2 year old son is assisting. He is now almost 26 and an expert on the telecom and wireless sectors, and is a senior consultant for a major consulting firm.
