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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.
If the author wants to add "wireless savy" (sic) to his resume, I'd suggest running it through a spell-checker afterwards...
someone has too much time on their hands...not to say i dont do strange things like that, too.
They should get together with the Sliiiiiiiiiiiiinky guy. Although there might be issues with reception..."HEY MAN! Quit shaking it!"
From the article I just did this testing today (2/14/2), but I'll post detailed specs on how to select a can, do the math, and build a waveguide antenna soon. Until then, consider buying the ARRL Antenna Handbook.
:)
Read more??? Hey, I'm on slashdot. It's rare that I even read the linked article.
That which does not kill me only makes me whinier
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]
Rob says
"If you can eat a big can of stew, you can make a high performance antenna"
Actually I am a vegeterian so make that a big can of beans and you too can be a wave guide. (in more ways the one)
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
Is there anything on the books (FCC, et al.) now that would stop me from *legally* implementing any of these solutions?
(And I'm not talking about ISP usage agreements and such.)
The only question I have is when Georgia Tech (my school) will ban pringle cans on top of dorms...
DAMN would a 802.11b network be cool to run there... Massive internal gnutella network, here we come!
I'm a concientious
What is the point of comparing homemade antennas? They would perform differently for everyone who built one. It would be better to just compare commercial antennas.
... I was just going to turn in my 32oz Bud can for the $.05 deposit!
- If we aren't supposed to eat animals, then why are they made out of meat? - Steven Wright
Wouldn't a conical waveguide work a little better? A dish would be best but probably rather large for the band they are trying to operate in.
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 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.
I just did this testing today (2/14/2)
He may have too much time on his hands, but at least he knows how to spend it. Who needs romance anyway??? Right, CmdrTaco?
;-)
Check out Girl Geek's journal.
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
"I just did this testing today (2/14/2)"
I'm guessing this guy didn't have a girlfriend to spend time with on Valentine's day....
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.
You might as well face it. Pringle canning is dying.
--
Of course, it's also funny as hell. Go geeks! :)
In space, no one can hear you moo.
...about using old DSS/Primestar dishes for this type of thing. You should be able to pick up the dishes for cheap/free now a days. Would anyone care to post some links to resources on this subject?
why not just 8x?
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.
lol. I worked for Procter and Gamble Global IT for the past couple years and we've been experimenting with wireless deployment at certain locations. I wonder if it would be more cost efficient to recycle our Pringles cans toward this operation. It'd be fun to see Pringle's can antennas all over the place. Nice way to recycle.
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
hmmm... why isn't the network up....
...
God dammit mom! you recycled my networking equipment again!
Now i know to use a chunky beef stu can to set up a wireless network to my friends house.
alls thats left is to level all obstructions inbetween the mile strech. That will be the fun part.
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!!
while we're discussing cheap, homebrew antennas to increase TRANSMISSION range, has anyone successfully modified an 802.11b laptop card to increase the range at which it will receive a signal?
"The complicated futility of ignorance" - Kurt Vonnegut
A waveguide antenna feeding into a dish reflector is called a feedhorn. They work very well.
The truth shall set you free!
Instead of screwing around with tin cans, wlan enthusiats would be better off learning real antenna design, and building something appropriate to their situation. In addition to the blind and ignorant 'dB gain' that the slashdot wlan crowd seems to be fixated on, an intelligent consumer would be concerned with the beamwidth, the front/back ration, SWR, and the bandwidth of an 802.11 antenna, and not the oversimplified, crude, and possibly harmful (SWR too high can break radio gear. This may include your 802.11b card) pringles-can type of gear that seems to get a lot of geek press. This doesn't mean that you have to spend hundreds of dollars on a Lucent Orinoco antenna just ot have decent performance, but you do have to do some research into figuring out what you need, and then find a vendor that will provide you that at a reasonable price. guerrilla.net provides provides free plans for an engineered antenna (as opposed to the gross hacks which appear here). Yes it's an omni. Still, you may get better performance, because not so much of the signal is wasted due to poor SWR!
This is supposed to be a "science" project but it uses non standardized measures.
Wasn't that the way NASA dumped a space probe on mars (US-miles, GB-miles or km)? I doubt anyone outside the US is able to build one of theese correctly.
Atari rules... ermm... ruled.
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?
100 watts? On the link listed, that's what they say. But as far as I know, the legal limit to boost a signal in the US is 1 watt. More than that, and someone will hunt you down to shut you down. Right?
It says TRANSMIT, doesn't that mean it's not a bi-directional antenna like you need for 802.11b? Wouldn't something sold over at HyperLink Tech. be better, seeing as they are more specifically designed to be used with 802.11b?
Why all the hype on the directional antennas? I would be MUCH more interested in an omnidirectional antenna so some neighbors and I can ALL see each other, not just 1 to 1. Is it just that they are harder to make?
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.
One big advantage of circular polarization is that it will talk to both horizontal and vertically polarized antennas. You do have to make sure that if you're using two circularly polarized antennas, that they have the same sense, i.e. LHP or RHP.
A Shadeless room is a brighter room.
You know you are a geek when you take calipers to the grocery and measure all the soup cans before buying one.
The regulations do state that if you use a more powerful gain antenna that you have to reduce your power from the maximum by a certain amount for each dBi above the allowed limit.
So in a sense the amount of focusing is limited.
However the Orinoco (Lucent) cards are not anywhere near the maxiumum power, so with a stock card you just can't get an antenna that will make you break the law.
To really do this right you need a bidirectional amplifier like made at hyperlink. A commercial antenna, lightning protector, low impedence cable, and professional adapters are handy too. Hyperlink sells nice kits with all of that.
Anyone who cannot cope with mathematics is not fully human.
I was on a Navy ship once next to another in a bay that was radiating. We closed the hatches because our eyeballs were getting hot and starting to cook.
The phased array flat panel Aegis radar can focus a beam that will drop a poor little feathered creature right out of the air.
...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?