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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/
Can it be adjusted to fit on top of my tinfoil hat?
"performs as well as the convential quarter-wave design but is only 1/3 as large"
Behold! I give you the twelfth-wave design!!
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.
this is patents at their best: the little guy innovates, and becomes the not-so-little guy in reward
that should be the purpose of patents, to protect the little guy who innovates
let us hope that we can back to this world, a world where patents reward innovation, instead of suppress it
it is a delicate balance, but there are hordes of ip lawyers and corporate whores out there who are hard at work, having sold their conscience, hard at work warping the balance in the direction of those who don't deserve to be rewarded for suppressing true innovation like this
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
"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?
All i could see is that it is a 2-dimensional helix, so it's likely to be directional, if radio waves aren't hitting it on the perpendicular they will miss.
The other thing I saw was that you tuned the antenna for a frequency with components - does this mean potentiometers or does it mean scrapping it and buying another 2d helix tuned to the specific wavelenghth?
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=
There are several parameters for an antenna system (receive parameters in parens):
Most compact designs trade bandwidth for performance - the work well at f=NNN.N MHz, but not well at f=NNN.N +
This gets to be REALLY important for wide band systems like CDMA and UWB.
www.eFax.com are spammers
That the University of Rhode Island and the Physics dept were made beneficiaries of the patent.
I can see this generating alot of revenue, and people (corporations) that may try to rip this off.
At least they will have a vested interest in fighting for the patent.
He found that by using those pringles mini cans, he could get similar reception to that of a regular-sized pringles can.
He expects to get a 10x power boost from metal chewing gum wrappers, and 50x from a microwaved AOL CD!
stuff |
c'mon, i don't care what you say... if it's 1/3 as large no woman on earth would believe it performs as well! :p
Rats, so that means I got to get good at using it then :( All along I was counting on my size...
Of antena that is ;)
photoplankton
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
I wish them well but FWIW, it got a skeptical response on this popular ham site qrz.com
I'd love to see a picture of this as I don't know much about antennae.
Here.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.
From the simplistic description given, this design has hundreds of thousands or prior art examples already sold in the marketplace, and has had for maybe 45 years.
Most any CB'er that wasn't running a full 1/4 wave stick on the roof of his car, and getting it mangled by driving thru any overpass with less than 14 feet of clearance, was using a shortened antenna of this design. They were also a bit narrowband, having extreme difficulties in getting 1.3/1 or better vswr performance over the 40 channels of the cb band.
They alsa radiate a disproportionate amount of their power well above the horizon, reducing the gain in the real world.
New? Yeah, somewhat like me, I'll be 70 in a few months.
I suspect that there are, or were (some having gone on to that big retirement party in the sky held for failed companies or merged into oblivion entities) plenty of patents that will prove prior art, if the patent office wasn't too understaffed and lazy to search for them. Avanti & HiGain are just 2 names that come to mind.
Scuse me while I chuckle at yet another of the patent offices incompetant blunders.
Cheers, Gene
Groan. This is not as unique as most would have you think.
First, most PCS phone antennas don't have to be shortened. The wavelength is such that it's not hard to get 1/4 wave across your typical portable phone. It's a mere 4.1 cm.
Just so that most of you understand, a monopole antenna is really half of a folded dipole. It has a wire going up and then it goes back down the pole to a field of radials. It has a characteristic impedance of half what a folded dipole would be --about 150 ohms.
In contrast, a normal quarter wave vertical has a characteristic impedance of about 37 ohms (assuming a very good radial system).
Now, remember the part about heating up the antenna? The reason it happens with very short vertical antennas is because there is a current node right there at the base feedpoint. Even a small amount of resistance will generate heat. As you shorten the antenna the characteristic impedance drops. For anything less than a tenth of a wave long, it can drop to less than an ohm. At that point, ANY antenna resistance, even the normal resistance of copper or silver, becomes very relevant. If someone were to use a superconductor, it might make a very big difference.
So a shortened vertical isn't such a good deal. We use them because sometimes that's all we can afford to install on a mobile system. This is why most hams who operate on longer wavelength bands try to locate the loading coil closer to the middle of the antenna. It gets the loading coil away from the worst of the current node, reducing i^2r losses, and increasing efficiency.
Now, take the monopole: The current node is near the top of a quarter wave monopole, not the bottom. We still need a loading coil, however, so that we can match the impedance to something we'd expect a transmission line to have. If we shorten the monopole, we move the current node. The key is to move the current node away from the loading coil, because loading coils don't radiate well.
Thus, what this designer has done is to distribute the loading coil of a shortened monopole so that he avoids the current node.
There are problems, however. First, you still need an effective radial system. Without one, you simply won't have anything that radiates worth a damn. Second, while coil Q factor is less relevant where it stays away from the current node, it still has to be damned good. Further, the current node at the top needs to have very good surface conductivity.
Finally, no matter what, a shortened vertical antenna will have a shortened bandwidth, proportional to how much the antenna itself is shorter than a regular 1/4 wave. TNSTAAFL.
Don't misunderstand, a short antenna doesn't have to be inefficient. However efficiency is not the same thing as gain. Short antennas can not have much gain. That's a matter of physics and mathematics. And the shorter an efficient antenna gets, the less bandwidth it can cover. Despite the steady parade of publicists, that's the reality. Don't buy any snake oil, folks... This isn't really that novel.
Nearly fifty percent of all graduates come from the bottom half of the class!