Picture of Wireless Internet Cantenna
This is about making an antenna using a usb wifi adapter, and an old fire extinguisher I never got around to refilling

I used a hacksaw, a dremel with the heavy-duty cut-off wheel and some small files

To figure out where to cut, I drew lines to cut along, on the outside of the extinguisher body. This includes a nice ink pen, an architects scale (tri-angle type ruler), and a piece of paper. The ink pen could have been a scribe, instead. A sharpened nail, or ice-pick would work for that

I went and recycled a few photos between steps, as I didn't take enough pictures during the construction
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Step 1: It all started with Pachanka's Wokfi

Picture of It all started with Pachanka's Wokfi
After reading another instructable on how easy it could be to build a parabolic antenna, I wound up with this

And this, is a 24 inch wok I found at Goodwill for $7, mounted on top of a telescope tripod. Handles were removed and the thumb-fi taped and hung off of some string into the focal point

But before I could test this wokfi, I read yet another instructable for a yagi cantenna, and after following some of the links in the comments I decided to build this cantenna

Step 2: In hindsight

Picture of In hindsight
I knew I should've stopped and took pictures, but I didn't.

So this is what I started with, a Kidde fire extinguisher that was empty and had been cluttering up a shelf for several years now.

It has an aluminum body with a nice flat bottom, which I thought would work well as a waveguide.

It measured around 3-1/4 inches outside diameter. This is like the kind you might find in a car or around a kitchen. If it had a plastic body, I suppose it could be wrapped in aluminum foil, but I would've scrapped the idea and gone for some exhaust tubing or something like that.
spawnos37172 years ago
Would it be possible to multiplex a couple more wifi adapters into "the can" to further acquire signals?
Shadetree Engineer (author)  spawnos37172 years ago
As far as I personally know, I very much doubt it. Doesn't mean it's impossible, but I think there'll be all kinds of technical issues that will make such a build way too complicated. Just inserting a dead unit will interfere with the first one. Multiplexing just two USB adapters in any kind of antenna configuration is too much challenge for me! Even if all you did was use the adapters as-is with no can. I think you'll need to write a custom driver to do it.

If all you want to do is just grab more signal, the best approach is to increase the physical size of your antennas 'ear'. In other words, take a look at parabolic dish antennas. The bigger the dish, the more signal you can grab out of the air. And any size dish can be made to work with the same adapter.

A less effective, yet improved alternative is to add a cone to the end of the can.

PS: Something you might want to take a look at is what I'm using these days. A Ubiquiti Bullet.
sn00ze3 years ago
this page has some good images explaining where everything goes
sn00ze sn00ze3 years ago
Shadetree Engineer (author)  sn00ze3 years ago
Nice. That site keeps all the research for can dimensions as simple as possible.
cotton6 years ago
it will work on a old satilite dish
Shadetree Engineer (author)  cotton6 years ago
Yes, it will.
no i meant as in use the oringinal antana at the end of the arm poiting at the dish and wire it into a wireles card
Shadetree Engineer (author)  cotton6 years ago
Oh okay. Main problem is the waveguide that came with the dish is about one inch in diameter, which is for a much higher frequency than 2.94 Ghz. I would recommend installing a coax connector into a can like my fire extinguisher approach, with a tuned length of wire soldered on the inner end to act as the active part of the antenna. Then you can connect a pig-tail from a wireless card to this antenna. Try Seattle Wireless this site seems to have some current info, they link to cantennas, which use this connection method.
enf0rcer1213 years ago
i just completed mine like this and picked up 7 more connections
bugmenot54 years ago
 Had there been any pressure inside the extinguisher there is no possible way you could have opened it by hand. For experimental purposes, try doing so with scuba diving equipment.
Shadetree Engineer (author)  bugmenot54 years ago
Uh Ok.  That must be why I emptied the extinguisher!  Though I dimly recall having thoughts of an exploding white cloud of powder shooting into my eyes as being somewhat instructive.

Your proposed experiment I'm assuming, is to attempt unscrewing a fully pressurized scuba tank?  Huh, I remember wanting to do that when I was in high school.  I don't know if it was the A-Team or McGuyver, both of those shows were playing at the time. But they were the inspiration for that scuba tank fascination.

Did you know that a steel scuba tank if cut in half, has a wall thickness of over 3/8ths inch?  It took me a while with my sawzall, but I've done that once.

11richie214 years ago
do you know if this "cantenna" works with an xbox 360 and can you use a wifi max adapter. thanks
Shadetree Engineer (author)  11richie214 years ago
I'm not too sure about the 360 adapter as I never used one. If it can be connected to the 360 by a cable, maybe 6 feet in length, then it should be no problem as you would just put the 360 adapter inside of the can instead of the adapter I used.  If you are using the official 360 adapter, that appears to use an external antenna, so I would just put the antenna inside the can with the adapter arttached to the outside. Use a usb extension.

The WiFi Max adapter appears to be an access point for your 360 to connect to. It looks like it should work exactly the same way as what I did, just accomplishing a different purpose.

Did you know that you can use a router with built-in wireless on your 360 to connect to another router? Look at DD-WRT, that's an alternative software that can run on a router. It allows turning the router into an adapter, which means you can plug an adapter into the ethernet port instead of the usb.
ok thanks! good to know
sn00ze4 years ago
(removed by author or community request)
Shadetree Engineer (author)  sn00ze4 years ago
Nice site, keeps the panic level down!
McGragger5 years ago
is this the correct way to face the thumbfi ? Which side is the internal antenna on?
Shadetree Engineer (author)  McGragger5 years ago
I'm not sure what you mean by 'facing the thumbfi', but in this photo I made the mistake of inserting the adapter too far inside of the can. I didn't find this out until later, when I adjusted the insertion depth for best signal. I have tried putting the adapter into the can with either side facing forwards, and found no significant change in signal levels. I never cracked this model of adapter, so I'm only assuming that the internal antenna is located at the tip, that it is likely formed directly on the circuit board, and that there are no other components inside of the adapter to block the 'backside' of the internal antenna. ps - check out the 'Conetenna' tutorial, where I add a cone to this can to gain more signal. I think I put in some advice on cone layouts that can be sized for any dimension of can opening. My latest connection with the 'Conetenna' is just over a mile, netting a very useable connection speed.
i would say so!
k_man935 years ago
looks like a cool hideout room thing... and its practical!
geeklord5 years ago
Gotta love those people who leave their wireless' name as the default and don't add any security :D
i love that too
xvitox5 years ago
Hey do you wanna send me a link for the wireless adapter that you used?
Shadetree Engineer (author)  xvitox5 years ago
It would be nice if the transceiver was at the lower side under the can so a boot could be made of silicone to keep water (rain) off the USB connector.
The signal is polarized, it works better if you rotate the antenna for best results, not for water-proofing. If you make a boot, then it shouldn't matter which way it is.
lil jon1685 years ago
how do i get wirless inter bet when i have DSL
Shadetree Engineer (author)  lil jon1685 years ago
DSL is usually a really fast connection to the internet. Faster than most homemade wireless set-ups. I'm going to assume you have a DSL modem and don't mean to abandon the DSL connection, but would like to add wireless to it. Or does the modem have wireless already, and you just need to install wireless on another computer? In either case, buy a router with Wi-Fi built-in, or a Wi-Fi adapter. And in the case of the adapter, follow this instructable or one from the Wi-Fi Group to connect to your modem from the treehouse!
can u send me a link to a wifi adapter cause i dont relly know wat ur talkin about
Shadetree Engineer (author)  lil jon1685 years ago
Ah well, sure. Check your message box.
For some reason, i just don't think a cantenna is as good as a wokfi or parabolic reflector.
Well, in the case of my waveguide 'Cantenna' described here, you are absolutely right! If you should happen to see a newer antenna creation, called the 'Conetenna', you will note that it uses this can - simply adding a cone to the end to increase the signal. A really good parabolic will still beat the Conetenna.
I'll work on it, internet is expensive.
danfolkes5 years ago
Hey, cool instructable. I like the use of USB adapter insead of having to deal with pigtails and wire. You might consider popping off the case to the thumbdrive to see if you can position the inner antenna a little better. It might be out of wack. I am going to make one of these out of a juice can!
Shadetree Engineer (author)  danfolkes5 years ago
Well, I've heard a rumor that the adapters built-in antenna could be oriented 90 degrees wrong for a side mount into the can. It was recommended to put the adapter into the end of the can to compensate. The built-in antenna is usually going to be formed from the copper plating that is a part of the circuit-board. You would be better off converting to a pigtail if you want to perform surgery on any adapter. Not a crazy idea if you consider that there are self-powered usb extension cables to allow some really flexible installations!
deejaydee5 years ago
im going to buy a wireless adapter to connect to my friends wireless thats about a block away .. and i was thinkin of buying something cheap like the "ENCORE ENUWI-G2 IEEE 802.11b/g USB 2.0 802.11G Wireless Adapter" .. and im wondering will that work?
Shadetree Engineer (author)  deejaydee5 years ago
Yeah should be just the same, only the size of the hole you cut will be a bit different. I've run into a good point of view that brings up an issue with how the antenna inside of the adapter is oriented. That is, for some USB adapters, you will get a better signal if you install the adapter on the end of the waveguide tube, instead of on the side like I did here. Check out what happens if you put a tuned cone on the end of the waveguide, like my conetenna instructable.
hey nice one man...but i have a question....should i buy a wireless adapter of good quality or any will do....another thng i wanted to ask was i have an inbuilt wireless in my laptop and have to stand in the window with my laptop on the edge to use do i get abut enhancing the sig for that??
Shadetree Engineer (author)  swsws_75 years ago
I spent $20 for mine, and it still works fine. I'm using it right now to connect to an access that's just over 5,600 feet from me. My laptop has a built-in wireless, but the usb adapter works well, I just ignore the pop-up that reminds me that the built-in isn't connecting to anything and let the other one make the connection. There are 50 foot powered usb extension cables, which is why if you don't need extreme power, a usb adapter is a better choice over a card adapter. For just boosting your laptop's built-in, you would do something like a reflector built around the laptop. Or possibly a passive director array mounted on the windowsill & just park the laptop behind that. But even though using aluminum foil and cardboard to make your entire laptop into an antenna is cheaper, it's less hassle and better if you just buy a decent adapter ie 'namebrand for cheap' Don't trust those dollar store adapters, they only work inside the store you buy them from!
Forgot to say, but my adapter and can shown here is now sporting a signal boosting cone. Look for the 'Conetenna'.
wage6 years ago
how would you go about connecting this to say, a router..? Then you could create a bridge and repeat the signal to several computers :)
Shadetree Engineer (author)  wage6 years ago
With some tape and string? I guess I had to think about that a bit. What about using a router with a wireless connection built-in. Then pull it's antenna and solder on some coax in place of that. I've seen some designs that build in a band-pass filter as a part of the antenna, so I'm not really going to suggest simply stripping off an inch of the coax and taping the end inside of the can....
awkrin6 years ago
it's nice, but doesn't the adapter work better if u remove the plastic case? I mean if u later secure it should be safe from anything. now u done the same mistake soooo many people have done. now there's a button the same size as the others on your keyboard that has written on it "Print Screen"/"Print Scrn" and sometimes it even has "Sys Rq" on it. while you're reading this, I want u to press it, then go to your favorite image editor (ms paint loads the quickest) and then press ctrl+v or paste from the edit menu and amazing things will happen!
I've been reading a LOT of this WiFi stuff here on our extraordinary and was wondering if anyone has tested the strainer method against the coffee can or pringles method and also against using an old directv satellite and such. Which one would give me the best reception? I'm guessing the satellite dish but I am new to this. TIA!
Well, in my limited experience, the strainer is better than nothing, the coffee/pringles cantenna is a lot better, and the dish is even better still.

Here's everything I saved in my 802.11 bookmarks folder:

Homebrew Antenna Shootout

How to build a Tin Can Waveguide Antenna

DWL-122 wifi adapter gets cracked open

USB extension, up to 80 feet

Waveguide Calculator

Frequency/Wavelength Calculator

Technical Info: Satellite feedhorns

Brass Yagi


so... did ya ever test out that big wok? Right now I have a homemade setup similar to the wok but MUCH smaller. It works pretty well, but not as well as I'd prefer.
Yeah I did, shortly before building this. It didn't work as well as the cantenna, but that may be due to a bum curve - that wok isn't even close to being parabolic. I was thinking of making a super-sized horn, but other projects have intervened , and the Dish 500/Cantenna combo I built immediately after this is still working okay. Just yesterday I found an 18 Mb connection across 1/8 mile of water with my dished cantenna. This image is the wok resting on a lawn chair. I was able to do a bit of surfing just before I took the picture.
sonnytiger6 years ago
can it work if you use another size fireextinguisher ore any other type of metal tubing ect? Mail me at
Shadetree Engineer (author)  sonnytiger6 years ago
From what I've seen, the precise inner diameter you use can vary a lot and still work. But, to get the best performance out of 2.4 Ghz, you need to stay within a range of diameters. I can't find my notes at the moment or I'd put some numbers down here, this particular extinguisher was near the small end of the range, so go bigger in diameter. Keep in mind that whatever inner diameter you use, will change the best length to cut the tube, and also for where to cut the hole for the thumb-fi.

You can use any tube, but the extinguisher has the advantage of the end already being capped, and for this extinguisher, capped flat and with an almost perfectly square seam.

If you want to use any other type of can, such as a soup can, you will have as good a result as I did with the same care taken to make all the dimensions come out close. I recommend spending an entire day to read this:

I just remembered this site today, it was bookmarked for a project I was researching two years ago. At that time I was trying to make an antenna that would take all of the energy from a magnetron out of a junked microwave oven, and beam it in one direction like a ray-gun. It took me a few weeks, but it finally dawns on me that I've been seeing several times now that the thumb-fi and the micro-wave ovens are on the same frequency! I had this 2.4 Ghz feed-horn sitting right there on a shelf over the work bench where I made this cantenna! Bigtime slap to the head here....

By the way, I highly recommend going to the site I mentioned and building a feed-horn with metal-lens setup. That might be my next project as it is.
sonnytiger6 years ago
Yeah, i will be ableto use it, i have a laptop, and i never can get a signal, FREE INTERNET:)
Wow... this is a superly super awesome duper Instructable, it's great! This is amazingly done, the pictures are great, and everything is just awesome, nice job! I would love to see more stuff from you, this is just awesome!
My mother thanks you. My father thanks you. My sister thanks you. And I thank you
Well I say thanks/ your welcome. Just me. Nobody else.
I was feeling a bit giddy there...
LinuxH4x0r6 years ago
Cool! Too bad I'm using a wired desktop.
Shadetree Engineer (author)  LinuxH4x0r6 years ago
Don't feel bad, I had to go home and use my wired connection just to upload these pics.
Trust me I don't feel bad. I feel sorry for my dad trying to use wireless on his 9 year old hp laptop running win98. I love wired things (wireless has lots of limitations)
you can get a usb extension cord, you can either make it or buy it
Goislesgo6 years ago
great instructable... i will eventually get to doing this in the future. Not much time to "tinker" these days.
whizzkidtom6 years ago
LOVE the room, funky pipe. Is it for decaration?
Shadetree Engineer (author)  whizzkidtom6 years ago
The funky pipe is very much not for looks. It probably could be an instructable of it's own. But it's been built so many years ago that I will only describe it here. It's part of my auxiliary heating system, in the background you might note a fan, and the bottom half of a 5-gallon propane tank turned upside down. The tank acts as an exhaust hood directly over a propane space-heater (the kind of heater you are not supposed to use indoors) The space heater may not be seen easily in that photo. The, now, top of the hood is connected to several lengths of aluminum clothes dryer exhaust tube, which is that funky pipe you mentioned. The fan blows warm air out of the closet, and along the tubing, which is acting as a radiator. The tube runs the whole length of my travel trailer - along the ceiling, before exiting out through the wall to a 2 inch chimney. I think the chimney thing was supposed to be used for gas fired heaters anyways. Well, the hardware store had it, and it looked useful anyways.
my hero :-) i am in desparate need of a better internet connection. my desktop's internet connection suddenly stopped working (it has a wireless card) but my laptop still works, though incredibly slow. i use a wireless network from who knows where! download speeds are incredibly slow, and bah..when my internet was working on the desktop, i couldn't use things like email, AIM, and other messengers, and i have no clue why. also ,i accidentally made it so that the wirless network thing doesnt show up in network connections, and i have no clue how to get it back so if anyone has any suggestions, they would be gladly appreciated! PM me if you want or just reply to it here so that he gets more comments for his awesome instructable :-)
I had almost nearly the same problem with my laptop. First time I used the wifi to connect, it said I had a connection, my anti-spyware was able to update, but then I go to launch Firefox, and it's trying to use a dial-up connection. Finally, I just made a text file with the dial-up number and deleted that connection from my network settings area. That fixed the problem. Maybe if you could remove, then reinstall the driver cd that came with your wireless? That might put everything back.
Sandisk1duo6 years ago
now you can leech internet off a local library! all on the privacy of your roof!
Shadetree Engineer (author)  Sandisk1duo6 years ago
Or, in my case, from a motel advertising their free internet on a street-side sign.
rotorfied6 years ago
Is it possible to make that cantenna with a pringles tube? Nice instructable!
yeah, that's actually one of the first popular ones, since it's just the right size or something for the wifi waves... just google it and you'll find a few dozen right away
Cool! Great instructable! Just what I was looking for!!