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O'Reilly's Antenna Shootout
nickynicky9doors writes: "From Rob Flickenger O'Reilly Network's Systems Administrator :
'Gregory Rehm hosted an Antenna Battle Royale between a Lucent popsicle stick, a couple of Pringles Cans, our Coffee Can, a Hunt's Tomato Sauce can, and a 40oz can of 'Big Chunk' beef stew. Who was the winner?'" Let's just say it doesn't come loaded with saddle-shaped styro-chips.
If you're doing no better than omni, you may have an impedance mismatch to overcome. Pattern might be just fine.
They should get together with the Sliiiiiiiiiiiiinky guy. Although there might be issues with reception..."HEY MAN! Quit shaking it!"
But hey, it's a quarter wavelength. I guess anything's possible. If you'll excuse me I'll go and attach an N connector to that birdcage now.
icqqm [ICQ:11952102]
Does this really do the job? I know nothing about wireless networks (even though mine works great) but I have to wonder if beefing up one end of the system really works.
I mean, if the card in my laptop still sucks can improving the base station really help? Don't you need to improve both sides for a system that sends and receives?
That which does not kill me only makes me whinier
I don't think you run into legal issues until you start selling them commercially. Then they probably need to be FCC certified, which costs losts of money, etc. Also, there may be some restrictions on maximum signal strength on the ISM bands that 802.11b uses...but that, I'm not sure about, they might just regulate power output.
"(Man) tries to live his own life as if he were telling a story. But you have to choose: live or tell." --Sartre
might one of these antenas be mounted in reverse, on a small DSS/primestar style dish to improve reception?
just place the end of the pringles can at the focal point of the dish? i would suspect a significant gain from this, but then again the whole point of a pringles can antena is to be cheap, how cheap can a person get a dish?
also, what do you suspect the range to be on one of these homebrew antenas? could it span 2 miles to a passive repeater, then two more miles? or would the repeater have to be and active 802.11b access point?
if i were to hack an 802.11b access point to install a pigtail for a homebrew antena, could i install two pigtails for two antenas? and would it be advisable to further hack the accesspoint to boost the signal to 80-90dB?? i believe the FCC limits these 2.4Ghz signals to 100dB, but dont quote me on that.
The point of building this particular antenna was to create a unidirectional unit for building point-to-point wireless networks. Making it unidirectional also cuts down on the noise.
the lucent popsicle is nothing more than a 5/8ths wave antenna.. signals not at the horizon will suffer (up.down)
The pringles can is nothing more than a basic beam.. 1 driven element and 1 reflector (the metal bottom) it is not acting like a waveguide because the "metallic substance" is not electrically conductive (in my tests... if people in other parts of the country would test theirs? it would be interesting.)
The metal cans are a type of waveguide... more of a feedhorn design.. they would be awesome pointing at the focal of a dish. if you were to put a 45Deg cone around the opening you would further increase the gain of the can.
The best thing to do is modify a existing 2.4ghz feedhorn or antenna. you'll find them on Primestar dishes and KU band old sattelite dishes. they need a bit of tweaking (filing on the stub) but work best and the little aluminum concentrator on the old sattelite dish types ( the set of concentric rings around the feedhorn opening) will give another 2-3db not in gain but in selectivity and rejection of off axis signals. (better noise floor)
Do not look at laser with remaining good eye.
yes, the regulations are all about ERP(effective radiated power), not how much power your putting into your feed line. For many services this means that if you are running the maximum power, and add an antenna with more gain, you must drop your power. But for point to point networking in the 2.4ghz ISM(industrial, scientific, medical) band you are are allowed to use directional antenna for point to point communictations, upto i belive 6db gain and still run maximum power. Above that you must drop your power, but the requiered drop is something like 1db less power for every 2db of gain, so it's not to bad. Keep in mind that my numbers are not correct.
But the other thing to consider is that i think most cards dont run the maximum allowed power, so you should be able to use a high gain antenna with any problems.
ALso, keep in mind that the regulation allowing high gain antennas without lower power specifies point to point communications, so that 20db gain yagi ontop of your car might not be legal.
The other thing to remember with 802.11b, is that 802.11b isnt the only thing on the 2.4ghz ism band, and ISM isnt the only thing 2.4ghz is allocated for. There is also amatuer allocation covering the same frequencies, and there has been at least on case of someone having to shutdown an 802.11b network do to interference it was causing. Also always keep in mind
-- free as in swatantryam - not soujanyam.
You might try this guy out - its mainly build for AO-40 work in the 2.4 ghz range - should work really well for you 802.11 distance freaks :).
http://www.n3iyr.com/
He makes a big deal about which antenna had the most raw gain. This is only *half* the story. He only makes some vague hint about needing to consider the receiver noise but doesn't consider it like it needs to be considered. Antenna reception is rated in G/T (gain over noise temp). The story talks about G but no one knows what T is. Thus G/T is unknown and his conclusions are somewhat less than useful. A big signal is of no use if it is drowned in a heap of noise.
Yoghurt
That's right, not a yagi but a yogi antenna. It is similar to a yagi (classic unidirectional antenna) but has logarithmic descending elements. In a traditional yagi antenna, all elements in the array are the same size/shape.
I hooked one up to my TiBook via a hacked-together pigtail and lucent/orinoco connector to avoid the weak internal TiBook antenna, and got about 12 dBi out of it, this with no external power. For some yogi antenna info, see: www.ve3gk.com/stacked.htm
http://tinyurl.com/4ny52
But with slightly different subject matter, and a different set of suckers. See here. It's amusing to see this kind of hoax fool people.
That's definitely a phrase I need to use more often.
Second, people have done the Primestar dish thing before and report 22db gain with it, not 30-50.
Third, according to the ARRL antenna handbook, the 200" optical receiving antenna known as "Mt. Palomar" has 148db gain. Frankly, I don't think anyone's satellite dish compares to this (or could, at microwave frequencies)
Remember, 100db gain means 10 million watts of effective radiated power for every milliwatt of input power.
Antennas with over 30db of gain simply are not that common.
These things perform miserably, for a much better design, have a look at:
http://users.bigpond.net.au/jhecker/
For a 2.4GHz hellical that is simple to build, these things are great.
This page gives actually useful measurements and a great bulding guide. I would (and do) use one of these over these non-functioning cans any day.
In this case, I doubt it's a hoax. The soup cans comprise a waveguide/feedhorn at the frequencies that the 802.11 cards operate at. Certain cans (such as old Hi-C cans) are fairly good feedhorns because they're shaped right and are the right length to get a good signal in them. I know, HBO used to use 2GHz beamed signals to households (Before cable was prevalent- it was more economical than satellite, etc.) and there was plans, etc. out at that time to snag the signals they were sending out so that you didn't have to pay the monthly service fee for the rig they were using to broadcast it. The varying plans for these recievers usually included an antenna design using a certain sized Folger's or Hi-C can for a feed horn and a metal dish sled for the parabolic reflector. Worked pretty good as a makeshift 2GHz antenna. I'm sure the feedhorn part would make for a decent unidirectional range booster for an 802.11 card with an antenna jack.
I am not merely a "consumer" or a "taxpayer". I am a Citizen of the State of Texas
But the question remains, does attaching this higher performing antenna end up exceeding the effective radiated power beyond the limits set by regulations? If it does, you've got problems. The soup can doesn't and gets passable gain improvements over a bare card with a diversity antenna.
I am not merely a "consumer" or a "taxpayer". I am a Citizen of the State of Texas
Let's just say it doesn't come loaded with saddle-shaped styro-chips.
As any discerning antenna hacker knows, Pringles are CRISPS, not chips. Sheesh...
In the article, he describes having to point the antenna to one side of the target. This sounds rather like the antenna dimensions were wrong. In a yagi array, the main lobe will be to the front, with minor lobes coming off at various angles. The same should be true of any antenna (directional) either waveguide or dish. I couldn't see where he'd allowed for 'velocity factor' in any material length calculations. Also, when constructing a half wave di-pole radiating element, the capcitance across the antenna will cause actual dimensions to be shorter than theoretical. Driven element spacing also affects the shape of the pattern. It can be that a lower overall gain acheives better results than by having a better radiated pattern, the pattern can be affected by driven element position etc. Its a very technical subject, its worthwhile looking at the 'VHF & UHF Handbook' for more information. Still, a very interesting article combining two of my interests!
Merlin --- We're an autonomous collective... Help, Help, I'm being oppressed!!
A waveguide antenna feeding into a dish reflector is called a feedhorn. They work very well.
The truth shall set you free!
You can find other 802.11b antenna experiments in Finland and in Belgium with HomeMade antennas (this is in french, sorry). The 'KoekelBerg2 experiments' show the signal strength for a 3.9 km link with home made helicals and tin cans. We also got -85/-98 dBm with a can on a side and a simple lambda/4 wire on the other (the measure is on this side). We don't know if the apparent better performance of tin cans over helical antennas (which are much more difficult to build) is due to some error in our helical design (based on Jason Hecker's design) or not. I've got some other links here And, just a note about dB's : adding 6 dB allows you to double the distance.
What I find interesting about the shootout is the fact that while the antenna design is definitely not exactly what you call optimum, this is truly homebrew electronics design at its best.
I'm sure anyone who's read the ARRL handbooks on antenna design will come up with a slightly more expensive, but still home-built design that will substantially outperform the food can antennas. Indeed, one other poster mentioned a homebuilt antenna built in Australia that really worked well for 802.11b wireless networking using PVC tubing.
Here's an old article, where a fellow achieved 14km in testing (not just signal strength, but actual data flowing).
Also reports of 57km achieved by Lucent engineers, staying within FCC specs.
-me
Love many, trust a few, do harm to none.
I understand your sentiment, but what pending or passed legislation even came close to touching this sort of experimentation?
I've had enough abrasive sigs. Kittens are cute and fuzzy.
Once upon a long time ago, I lived a day's hike from any TV stations, and was too broke to buy a real TV antenna. So I made one out of what was to hand:
:)
About 100 feet of 4-strand telephone wire run from TV, out the window, to the metal roof of a large shed some 50 feet away, with a large tangle of barbed wire hanging from one corner of the roof (the barbed wire seemed to be critical to reception).
It worked amazingly well. Tho it's a wonder the TV didn't blow up.
Of course, it wasn't nearly as portable as a Pringles can!
~REZ~ #43301. Who'd fake being me anyway?
On my web site http://www.pythonemproject.com there are some FDTD Python programs that you can use to simulate waveguide antennas. Now these are not GUI based, and there is a learning curve. You basically set up the metal so that its tangential E fields are 0, thats called PEC, perfect electrical conductor. Each bit of metal corresponds to a matrix element. I've been meaning to try out a slotted waveguide antenna on one of my programs, maybe I will get to it and post it there. All of the FDTD programs are GPL, and you can use Animabob to view the E fields in real time.
Quick definition please. What does SWR standfor/mean?
In Bushworld, they struggle to keep church and state separate in Iraq as they increasingly merge the two in America.
Check out http://trevormarshall.com/biquad.htm
I have the dish, I have the biquad, now I just need to marry them together and VERY high gain antenna, thank you.
In Bushworld, they struggle to keep church and state separate in Iraq as they increasingly merge the two in America.
I like vegans. :).
Some of my favorite foods are vegeterians
--= Isn't it surprising how badly I spell ?
...but I worked with a fellow back in the '80s who built, for his MSEE thesis, a stripline antenna out of pieces of a Coke can for a GPS receiver. As I recall, his thesis included photos of the antenna that showed enough of the Coca Cola logo that everyone could see what it was made out of. It was fun conducting tours of the labs and telling high school kids that ``this project here is tracking satellites with an antenna made from a Coke can''. Loved the look on their faces. (Wonder where Sam is now...)
CUR ALLOC 20195.....5804M
The phased array flat panel Aegis radar can focus a beam that will drop a poor little feathered creature right out of the air.
Yeah, I have heard a few times that when au Navy ships in Sydney move out past the heads, into open water, poor unsuspecting seagulls near the ships drop dead into the water when they fire up the main RADAR.
BTW, I was told back then, that our eyes have no natural cooling mechanism (no natural need I guess), which is not good when you get a face full at close range.
War crimes, torture, lies, illegal spying... Would someone give Bush a blowjob, already, so he can be impeached?