802.11b Homebrew Antenna Shootout (Pringles Wins!)

http://www.turnpoint.net/wireless/has.html ^

[narses]

802.11b Homebrew Antenna Shootout - 2/14/2

Update 2/16/2:
I've been Slashdotted!
Some grammatical/spelling errors corrected

Update 2/21/2
How To finshed, linked.

• Introduction
• What the huh?
• The Shootout
• Performance Summary
• The How To

Greg's obsession de' jour
In my efforts to add the words "wireless savvy" to my network admin resume, I've been reading books and web pages on radio propagation, antenna theory and design, and building wireless networks with 802.11. One of the first things that got me excited was the Pringles Can Antenna.  Published on the internet and in a fine book by Rob Flickenger, the net admin for O'Reilly, this design for a do-it-yourself, VERY inexpensive antenna made from a recycled junkfood container is as cool as the other side of the pillow.  It seems that everyone is building and using these.  The various community wireless network groups all talk about them and folks are reporting that they do the job.

A friend of mine built his before me and looking at his finished antenna got me excited to understand the theory of how it works. Reviewing his plan, I came up with different spacing that he Rob did.  To see if I could improve upon the design, I built mine with corrected spacing.  While waiting for some wireless equipment to come in, I started looking for my next antenna project.  Oddly, the more I studied, the less I understood.  There seems to be quite a bit of confusion on how the Pringles antenna works and what design category it falls under.  The inner lining of a Pringles can looks metallic, but my tests show it not to be. The Pringles Antenna design, and some designs that pre-date it, seem to treat it as though it were metallic.  While folks are calling it a Yagi-Uda style antenna, the design of the driven element in the Pringles can antenna looks like a Waveguide style design.

Waveguide antennas don't use the director assembly (the washery bits), and therefore are much simpler to build. An old tin can of the right size, about $5 in parts and 10 minutes of time are all that are needed. The math for computing correct sizing of the components in a waveguide antenna is simple. Formulas in hand, I started searching my cupboards for tin cans that fit the spec. I found myself staring at the products on the canned food aisle at the grocery store. I even went so far as going grocery shopping with a tape measure. "No no, this spaghetti sauce looks much better. It's about three quarters of a wavelength in diameter, hon!"

What the huh?

On Feb 11th, Rob, posted an article on his newest homebrew antenna - a tin can waveguide! Rob used a large, 39oz. coffee can and placed a quarter wavelength driven element a quarter wavelength from the back of the can. He reported good results - even better than the Pringles can design used by so many. For the antennas I was building, I was using different measurements based on the antenna design material I had been reading. Now I'm a late entry into this wireless stuff and the experts are going a different way than me. It's time to benchmark.

The Shootout
My plan was to get relative performance measurements for various designs (including mine) of homebrew antennas for 802.11b wireless networks. To do this, I setup a wireless link and changed only the antenna- recording each antennas' performance under identical conditions. I didn't compare them to a commercial directional antenna as my only one has a male connector and I don't have the right cable to hook it up yet. The contestants were (click on each for design specifications).

A commercial Lucent "range extender" omni directional A buddy's Flickenger-design Pringles can Yagi My modified design Pringles can A Flickenger design coffee can waveguide A coffee can waveguide with corrected radiator placement A Hunts 26.5oz. pasta sauce can waveguide that fell in the optimum size range A Nalley 40oz. "Big Chunk" beef stew can Waveguide Performance numbers and methodology

The Performance Summary
The results surprised me! In our test, the Flickenger Pringles can did a little better than my modified Pringles design. Both did no better than the Lucent omnidirectional. Now this is just on raw signal strength, noise rejection due to directivity still makes a directional antenna a better choice for some uses even if there is no gain benefit. The waveguides all soundly trounced the Pringles can designs. I mean they stomped them into the ground on signal strength - as much as 9 dBm better. Every three dB is a doubling in power - that's three doublings (8x increase)!

Of the waveguides, the Nalley's "Big Chunk" took top marks. It was followed by the Hunts Pasta Sauce, my modified coffee can, and the Flickenger coffee can in that order. My three waveguide designs, which utilized the correct theoretical spacing, out performed the Flickenger Yuban coffee can handily. It seems that the design formulas for the waveguide design made a sizeable difference in performance. In the yagis, it didn't matter much. This could be because neither Rob's nor my designs are anywhere near right for optimum performance for a Yagi. I've decided that Yagi design is not for the timid or non-radio-expert.

With these results, I'm convinced that the waveguide design is the way to go for cheap wireless networking. The performance is good, the cost is very low and the skill required is minimal. If you can eat a big can of stew, you can make a high performance antenna.

The How To
Build your own Tin Can Waveguide Antenna (Cantenna). It's the easiest antenna design I know of.

[TopQuark]

Thanks for a great introduction into a part of our culture I knew nothing about. And, it appears, I should. Thanks.

[Clinging Bitterly]

Can't buy broadband at my house, but they can a quarter mile away.

But I think you'll find the FCC type acceptance of these devices places limits on the physical characteristics of any antennas, so there are two issues at play here. Stealing internet service, and violating FCC rules.

I don't personally know anyone who would do either of those things, nope.

But seriously, one should be careful about doing anything like this. The FCC rule thing isn't a big deal, technically a "violation" level federal offense, with a threat of big fine (and in reality, almost never enforced). But in regards to the stealing of internet service, and particularly if the provider is a telco or electric utility, I'd advise one to not just go out and do it without permission from the owner of the LAN to which you are connecting, you could get in some serious trouble. This hasn't become such a problem that the providers are out driving around sniffing for people who are hijacking access, but it will, and they can find you as easily as you can find them.

[SauronOfMordor]

Can't buy broadband at my house, but they can a quarter mile away.

This sounds like something somebody would like if they're engaged in downloading things they REALLY would not like to be tracable back to them

[Cacique]

bttfl

[Elsie]

The PICTURES did not show up! Go here!

http://www.turnpoint.net/wireless/has.html

[Rodney King]

OK, I need help here:

I have a Dell wireless setup, and I think that right now it is not encrypted. How do I turn encryption on? Can I just turn it on in windows, or wouldn't I somehow have ot turn it on in the dell setup?

Thanks.

[RadioAstronomer]

We used one pound coffee cans, broom handles, and aluminium snow sleds to build makshift S-band microwave dish antennas. They worked quite well. :-)

[longshadow]

We used one pound coffee cans, broom handles, and aluminium snow sleds to build makshift S-band microwave dish antennas. They worked quite well. :-)

Yes, but was it clockwise, or counter-clockwise polarization coffee?

[RadioAstronomer]

Yes, but was it clockwise, or counter-clockwise polarization coffee?

Eat it right out of the can and it will polarize you forward (or possibly to "the can" (pun intended) for sure! :-)

[tubebender]

Why couldn't you just daisy chain coat hangers from the ceiling...

[upchuck]

FReeRepublic...How bad have you got it...

Pretty bad, I guess. I've been given just three months to live.

[boris]

I guess I am a dinosaur, but I simply don't see the utility in "wireless" stuff.

I use computers that sit on a desk and connect with old-fashioned "wires".

All my phones--save one--has a wire.

My portable phone is almost never used. I got it when my local service went out once too often (rain in the switchbox) so I could order-in pizza.

No, I don't want my phone to take (low quality) pictures, nor do I want to send them to anybody.

I'm too disorganized to use a PDA (if I ever got organized, I'd conquer the world, so it is a good thing that I am disorganized).

In any event, I don't want to play games on my phone, or PDA. I don't want to try to access Excel or Word on my phone or PDA. And I certainly don't want to browse the internet on a 2.5-square-inch screen.

So I "don't get it" and probably never will.

--Boris

[LouD]

And the import and relevance of this article is... what?

...theft.

Or improving the performance of your own wireless network. The range of some of the internal antennas is not particularly great. The fact that this antenna is directional will not only improve performance, but make the theft of your own signal less likely.

[Psycho_Bunny]

The number of persons who use these antennas for legitimate purposes is so small as to not be worth mentioning.

You can buy a far more functional and unobtrusive +14 dBi directional antenna for $100.

[Psycho_Bunny]

WEP stands for "Wired Equivalent Privacy" which, in laymen's terms is conceptually similar to "Really cold boiling water".

In any event...there should be some sort of browser interface for connecting to your router/access point.  I assume Dell has given you instructions to "Open your web browser and type the address 192.168.0.1" and configure your router.

The WEP settings should be in there somewhere.  Be certain to setup WEP on the router before setting up WEP on your adapter...if you set your adapater first, you won't be able to connect to the router.

You might also have a router option for denying wireless access to all MAC hardware addresses except addresses you specify.  I'd suggest using it.  Somewhere in your adapter settings you'll see a number like "00:05:5D:95:ED:B2".  That's your unique, hardware MAC ID.

So the setting will end up looking like :"Deny all access except to 00:05:5D:95:ED:B2"

I know this isn't very helpful but I don't know how Dell handles their wireless stuff.  I'm just trying to give you a general idea of what you need to look for.

Remember, if you lock-down your access point with these two security protocols, and you host a LAN party or something, you're going to have to give your guest your WEP code AND enter their MAC ID before they can connect to your router.

 

[Psycho_Bunny]

Personally, I never had any use for WiFi either - until I moved to a new apartment.  My computers are on the same wall in my living room as my cable so, at first, I had a cable connection.  

But my cable was lousy....I had terrific throughput but my ping was in the 500ms range.  Since I work part-time for a online game hosting company, 500ms was totally unacceptable.  80ms is "slow" in the gaming world.

So I switched to DSL; only my phone jack is in my kitchen on the other side of my apartment.  Instead of running 100 feet of Cat5 up the wall, through the kitchen and living room, I just installed a 802.11a access point.

Given the circumstances, It's convenient, easier and looks better.  I'd rather be wired, though.

[Rodney King]

Thanks, that's very helpful. I think when I set this up I recall interfacing with the router, i'll dig through the stuff that came with it.

[Clinging Bitterly]

>> downloading things they REALLY would not like to be tracable back to them

I reckon so, though I'm not sure what sort of stuff that would be. I think most of the folks you find discussing this on the net are simply doing it because they can, and aren't after any particular sort of content.

The point of my earlier post was that if someone was habitually connecting from the same place all the time, they could be easily found, but if neighbors were sharing a wireless network by mutual agreement, I don't think there would be any criminal issues.

[Rodney King]

Since you guys know computers, I was wondering if you could help me with something. At any given time if I do a ctrl-alt-dlt I have like 31 processes running. What are all these, what can I do to get rid of them? These are waht I have right now:

opera.exe (browser)
taskmgr.exe
zonealarm.exe
msnmsgr.exe
ctfmon.exe
qttask.exe
LMpdpsrv.exe
McVSEscn.ece
MCAGENT.exe
MCVSSHLD.exe
ATIPTAXX.exe
Explorer.exe
VSMON.exe
Spoolsv.exe
svchost.exe
svchost.exe again, and somtimes there are 3 or 4 of these
mdm.exe
svchost.exe again
svchost.exe again
mcvsrte.exe
lsass.exe
services.exe
winlogon.exe
ati2EVXX.exe
csrss.exe
smss.exe
msmsgs.exe
mcvsftsn.exe
system
system idle process

Many thanks to anyone who can help me!!

[Clinging Bitterly]

That looks typical. Those are mostly services that are running as part of the operating system. You can search the names on Google, or wherever, and find out what they do.