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Old Geek Invents New Stick
the morgawr writes "According to the EE Times and Science Blog, a scientist at University of Rhode Island has developed a new type of antenna design that, by increasing the efficiency, performs as well as the convential quarter-wave design but is only 1/3 as large."
To check his theory, Vincent analyzed and compared the current profiles, output power and a score of other standard tests for measuring antenna performance. All measurements were in reference to comparative measurements made on a quarter-wave vertical antenna for the same frequency, on the same ground system and same power input. "I was able to increase the current profile of the antenna over a quarter-wave by as much as two to 2.5 times," said Vincent.
As a ham (amateur radio operator) this sounds like a very exciting development. I would like to see more "real life" testing in a variety of settings. Still, the idea of an antenna that can be reduced in size by that much (2/3) comes in very handy on the low bands where it's not uncommon to use several hundred feet of wire (Usually into a tuner).
Happy Trails!
Erick
http://www.busyweather.com/
How does it compare against that bizarre antenna developed by genetic algorithms that we saw a story on a few months ago? Or am I comparing apples and oranges here?
-1, "1337" speak
Will we see this at next year's WiFi Shootout?
Kinetic stupidity has a new brand leader: Allen Zadr.
"With the new helix design, Vincent has built a prototype 7-GHz antenna that he claims is indistinguishable from a quarter-wave antenna in all but its size. "Because the new design is completely planar, we could crank these out using thin-film technologies," Vincent said." Sounds like the answer to radio -powered smart cards ios just around the corner?
I still wouldn't mind seeing these in cars. My only question is if this can work with cars tha have "in windshield" antennae, such as mine.
Hmmm... I am no expert, but I thought those AM towers were tall so the antenna could be placed at the highest possible altitude. The radio transmitters in the Philadelphia, PA area are also located in the highest place in the region geographically.
I think the actual antenna is attached to the top of the tower. It's not the entire tower. Can someone help me out here?
Remember... ZG9uJ3QgZm9yZ2V0IHRvIGRyaW5rIHlvdXIgb3ZhbHRpbmU=
I was just reading about something like this just last night.
I'll bet it ends up working on the same principle that Bill Beatty is talking about when he got to thinking about why it is that an atom can absorb light so readily even though the size of the atom is such a small fraction of the wavelength.
Relevent articles:
Energy sucking antenna
On the Possibility That Electromagnetic Radiation Lacks Quanta of Any Kind
Nearfield coupling and tuned circuits
..this will be great, living in the stix has it's advantages and disadvantages (disadv-no cable broadband , adv - can see the stars at night) Disadv -Having to rely soley on Direcway for broadband. This will open the doors also to companies wishing to move to the rural areas.
A bunch of Tech Stuff
to describe a 2d cube, take a photo of a cube face on. congratulations you have one.
to describe a 2d helix, take a photo of one, concgrats you have one.
its basically a sin wave qith a specific frequency.
Although the articles are a bit thin on specs my gut instinct tells me it will be similar or an improvement the EH antenna. Link to definition (pdf) of EH antenna Link to (pdf) how to build an EH antenna.
I hope that despite of the patents the design will be made available for amateurs to use and experiment with.
These kind of innovations just show that Amateur Radio is still alive and can contribute in the advancement of radio.
Amateur Radio also still works for emergencies.
73 de Sjaak, W4RIS ex-PA3GVR
Hmmmm.. a 'ham' making new antenna discoveries...sounds familiar:-)
It is not physically possible to attain a moderate Q or low Q, thin monopole --antenna-- which is 15-18 inches on 21 MHz and is efficient. This is not a statement against K1DFT, or anyone else. It is a statement of fact, based on the physics of very electrically small antennas, and many years professionally devoted to pursuing such issues. K1DFT has apparently pursued a path long since traveled by many others, and not only myself.
Occasionally, in some form factors, it is possible to trade efficiency for gain, but this is too short for that. And so much for bandwidth.
Great care needs to be taken to remove multipath effects in the measurement of gain, and greater care needs to be taken in equating measured comparitive gain with actual antenna efficiency. Based on this anecdotal report, there is no evidence presented that such issues could be removed in the measurements.
Radiation resistance results from an antenna's sampling portions of radiating waves. A short antenna samples a small portion of the wave--and not from the peak, unless the electrical length is 1/4 to 1/2 the wave or more. Multiple current maxima do help increase radiation resistance. Efficiency is derived from the ratio of this radiation resistance to the total resistance--which includes ohmic losses. Distributed discrete loads are moderately lossy, and one would require load Q-factors of 1000 or more to attain even moderate Q antennas with high efficiency.
The optimization of distributed loads in monopoles is an old technology, recently aided via genetic algorithms. I recall, for example, some good work on this approach published in 1996 by Boas et al. Before that, R.C. Hansen made fundamental efforts into such understanding, as well as others. MATLAB is also a poor tool for this, because it is difficult to assess losses properly.
Another concern is: what is radiating? In some cases, ground planes (counterpoises) do, indeed, radiate in the far field and are thus part of the antenna. The monopole 'antenna' is often a loading mechanism in this case, and contributes little to the radiation. There are commercially used 'antennas' that are 1/10 th the height of a 1/4 wave or less; are broad/multiband/ and so on. This is not new. They are used in wireless LAN; RFID; and cell phones; and many other places.
Many here are aware of my efforts in fractal antenna technology--which started in a similar radio amateur vein. Although I applaude continued efforts into antenna experimentation through ham radio, I must confess that my educated opinion is that nothing new has, or will be, attained by such efforts. The state of the art is often not public, and far outstrips what is commonly available in, for example, amateur radio publications. I would enjoy being wrong, however. In fact, I'd get a great kick out of it.
It's sure fun to read about though, and experimenting is fun to do.
When the ionospheric conditions are right it is possible to work (on 28 MHz, at least) the entire world with a 5 Watt FM transceiver. Very spooky!
Most amateurs use way too much power anyway.
KI3J
Yeah, as a ham myself I have to agree with the "snake oil" theory.
Antenna design is a lot like cryptographic algorithm design. That is, a lot of extremely smart people have tried and failed. Often once their work is out in the public for a larger community to examine the flaws start to show through.
Like crypto design, antenna design is mathematically provable. However, it's complicated enough that it's damn near impossible for one person to cover all the bases and make something that really meets all the claims. As I said, even extremely smart and talented people goof up when working on this type of thing. The laws of physics are called laws for a reason.
Good to know that people are still trying though! That's how breakthroughs occur.
The ratio of people to cake is too big
It is only when you start to question those assumptions that you move forward.
That only works when you question those assumptions intelligently. Let me give an example. By the 1920's it was well known that noise power was proportional to bandwidth. Progress in radio reception quite naturally followed the path of narrowing bandwidth (from early spark-gap systems that had poor selectivity and on to elaborate tuned LC circuits). Armstrong, when developing FM, wasted years trying to get good signal-to-noise out of extremely narrowband FM systems, despite the fact that Carson had mathematically proved that this was impossible. If he had taken the time to understand the underpinnings of Carson's proof first (ie, narrowband analysis), he could have started working on wideband FM much sooner.
We know from Maxwell's equations that, given some fairly general assumptions about antenna geometery, size, gain, & bandwidth are a trade-off. It is much better to understand those assumptions (eg, the antenna doesn't change shape) than to challenge Maxwell's equations, or to spend countless hours hacking away in a lab like Armstrong did.
"As others have noted, the tower is the antenna. The output line coming from an AM transmitter is fixed directly to the tower. Usually this is not fixed at ground level to avoid killing a passerby. RF waves WILL arc and kill. Also, if you are feeling especially depressed and want to cause yourself bodily harm, walk up to a hot AM tower barefoot and grab it."
:)
When I was in the Canadian Military I was a Radio Operator. We had a standard practice of informing the operator not to key the antenna when changing the HF antenna on the top of the truck - usually in fact the person doing so went in and physically checked the antenna was disconnected at the set end. Then you went on the roof and unscrewed the antenna and screwed in the new one. If someone forgot the middle step - and the operator keyed the antenna - you would see the person touching it get lobbed a good 10-15 feet off the top of the truck by the shock and it might or might not kill them or at least severely injure them. Only saw this happen once, and the guy wasn't hurt, he got up and was ok in a few seconds - although the operator was hurt shortly thereafter
10,000 watts is not a good thing to run through the body...
"The first time I got drunk, I got married. The second time I bought a chimpanzee, after that I stayed sober" Arian Seid
Granted, I have seen antennas that defy logic until you really understand how they are working.... the Discone antenna for example... but this one still is baffling and the lack of details increases the skeptical thoughts.
It sounds like a cross between a capacitive hat and a rubber-ducky style helix.
A capacitive hat lets you expose the lower part of the 1/4 wave half-dipole (where most of the current is) then cut off the end. The remaining current goes into the capacitive hat and doesn't contribute to the magnetic field radiation.
A helix lets you shorten the entire half-dipole, but still ends up with the current decreasing in the classic cosine fashion as you go up the whip, until it goes to zero near the end.
This sounds like some cross of the two, with a variable wind and a distributed capacitive loading, which allegedly succeedes in keeping the current high (and in-phase) over the full length of the shortened half-dipole.
I'd love to see a better description than the one that was given.
Meanwhile, I'm suspicious of the claim that it is just as good as a dipole. If it's shorter, it's intercepting a smaller amount of the passing wave. To achieve equivalent gain it has to make up for that in some way (like being effectively broader, or the "capacitive loading" structure on the upper end of the device coupling to the electric field in the space beyond).
= = = =
By the way: My favorite "shrunken antenna" is the DDRR. Very narrow band, but tiny.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way