Oh man, not this again. I published,in Comm Quart, a lengthy article in....1996? It showed that Kraus's small loop approximation (SLA) was wrong. I used NEC4 (could have been NEC2) to calculate --radiation resistance-- as the loop got small and smaller. Yes, I did this for a fractal loop. The SLA does not work correctly on very small loops IF you characterize by AREA, 'A'. Everyone here knows the decades of flack I got on fractal antennas; for that reason, I am not opening the door (again), almost 25 years later, on SLA arguments (for me). That is, I don't need that aggravation. Kraus's equation is simply wrong. Works fine for high-end of 'small' loops--only. 73 Chip W1YW
re: "I published,in Comm Quart, a lengthy article in....1996? I" I wasn't on the 'mailing list'. ( I was also doing cellular about that time with little exposure to loops!) Neither was the author of this article, who cites Kraus and copies his equation in this pub: High Frequency Design/SMALL ANTENNAS From February 2007 High Frequency Electronics Copyright © 2007 Summit Technical Media, LLC Title: "Basic Principles of Electrically Small Antennas" By Gary Breed, Editorial Director Bad information continues to be spread ....
Which begs the questions: 1) Where is the dividing line for this "high-end of 'small' loops? 2) If the geometry is the same, why does Kraus's equation turn to poop at this yet to be defined point?
Because area is not the defining parameter. For simple euclidean shapes, its a good approximation, but as A<<(1/10 wave diameter squared) the approximation stinks.
Miron (Douglas) makes the same mistake in his book: "Small Antenna Design" Copyright © 2006 pg 34, "Example 2.3 Loop Impedance and Efficiency" using his eq. 2.50 http://bbs.hwrf.com.cn/downpeef/small_antenna_design_1882.pdf
BTW, Gary Breed (K9AY) is a great guy, and I presume he was just writing up an article that summarized Kraus. He was editor of 'High Frequency' a while back. Doug Miron is KC0NKY---I could be wrong on the callsign. I do have his book. I know some of you guys are very interested in loops. Unfortunately, I have moved on. I will try, at some point, to dig out the Comm Quart article, but IMO , you should find someone else who has it. Its not that I don't think that its important, its just that it left a bad taste in my mouth, and my memory is too good to brush that part of the experience aside. Also, as I get older, my family wants me to emphasize the other stuff, which right now is massive MIMO; fractal metamaterials; fractal electromagnets; and fractal superconductivity; and others. Its a focus issue given the reality that at some point, the clock runs out of time But not soon-- Clearly adoption of innovations in antennas is on scale of decades, and that is what is driving the 'focus' issue. BTW, as most of you know, its really the ohmic losses that drive the issues on small loops. And yes, there are 'small fractal loops' by others besides me; some folks in Britain went gaga over them a while back. If you dig hard you might find it on the web.
Don't worry about it! I would like to see your pub, but no rush. I've arrived at the point where I view all these author's work with a bit of suspicion now (I think they copy each other en masse for starters), unless they can show some repeatable 'lab work' that supports their thesis. I was considering some improvements to the vicinity/the environment my loop occupies, eg. metamaterials, with a couple of simple pre-cursor experiments to verify some thoughts before my sight worsened the year before last (2017) ... restored now, but another year has passed in the process. Between WSPR and hand-held S11 'test sets' (antenna analyzers) these things have allowed a lot more purported 'theory' to be tested, verified.
Here's a review---I had no input or knowledge it was being built. This is an outside corroboration as I see it. Review I have one of GM0SDV's fractal magenetic loops. I was using wire antenna and the nose levels were so high it was useless to operate on the lower HF bands. I have a loop installed in the loft which is covers 80 60 and the 40 metre bands. ( see picture attached). The antenna is only 1 metre in diameter. I have to say I was very sceptical when installing the antenna, thinking that surely this cannot be much good . In practice, this was totally different. These antenna have a very high Q and so when tuned for use at a specific frequency the bandwidth for example on 40 metres is only a few Khz. To tune , I listen to the radio and peak the noise and this gets the tuning very close to what is needed. Then I connect my MFJ antenna analyser to the antenna and get it spot on for SWR and 50ohms impedance. You can of course use an SWR meter. Having such a narrow bandwidth has the big advantage of acting as a band pass filter on the front end of the receiver so any artifacts cause by adjacent strong signals are eliminated. I used WSPR ( Weak Signal Propagation Reporter) and running 5 watts enabled me over the last few months to see what the propagation pattern is like and also let me see who could hear me and what I could hear. I have enclosed a screen shot of the performance which on average band conditions is very typical. This is only for a period of 30 minutes. You will see that on 40 metres I was being heard in Sydney , Australia ! That is good enough for me. European coverage is good too. I also like to operate on PSK-31. The fractal loop is perfect for this type of operation. PSK-31 is fixed on one frequency so once you have tuned the loop for 40 metres , you never touch the antenna tuning again. On any of the PSK-31 programmes you just click on the signal on the " waterfall " and start typing. A club member was in North France on holiday in September with his caravan so he had a vertical and low power. We had several QSO's on PSK-31 on 5 watts with ease over the period of his holiday. I have found that the antenna tuning is extremely stable. Over a period of weeks working on PSK-31 the antenna was on one frequency. Over time and with varying temperature changes in the attic, I thought the antenna would have needed re-tuning. I never needed to adjust it. This made for very simple and dependable operation. My next job is to dump my wire antennae for 14-28 MHz and try out a fractal loop. For these bands these antenna look ridiculously small at about a 1/3 metre diameter. So if you cannot put up an outside antenna and even if you have a really small loft space there is really no excuse for not operating on the higher HF bands !! Cheers Stewart G8YQN, Filey, North Yorkshire, UK
Here's a survey of what I thought was the more notable loop literature (and projects!), and, on other pages, useful "tools" like an "AC resistance" calculator (actually, links to same, and "resistance" owing to skin effect) I put together maybe 6 (six) years ago now ... I didn't address any of the fractal material, after all, one must start somewhere so I stuck with the basics. https://thetruthaboutloops.wordpress.com/reference-library/
I am repeating a comment by G8YQN--- My next job is to dump my wire antennae for 14-28 MHz and try out a fractal loop. For these bands these antenna look ridiculously small at about a 1/3 metre diameter.
I always thought it was always 983.6/f in MHz.... 491.8, 468... po-tay-to, po-tah-to. Relax and have fun.
I see Amateur Radio as a social enterprise in which we use the tools of technology to effect that social interaction. I think experienced Amateurs and those Amateurs with a scientific and/or engineering background can help those who are less experienced. However, those less experienced also have a responsibility to do some research themselves before asking a question. Pheel
