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How to build “cantenna”, a wave guide antenna out of a coffee can November 27, 2007

Posted by GuySoft in cantenna, Crictor, diy, Hamakor, linux, open source, wifi, wireless.
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This is really a translation of a post I wrote in Hebrew out of Linmagazine.

Here is my own DIY guide to build a waveguide antenna. This antenna will dramatically boost your wireless connection to a specific direction, enabling connectivity to great distances.

The requirements:

  1. A coffee can with a diameter between 70mm- 110mm
  2. A copper wire, as straight as possible
  3. A female N-type connector
  4. A Pigtail – a cable that connects the cantenna to the wireless card (the card needs an external antenna connector.
  5. A wireless card with an external antenna connector.

stages of building the cantenna

Stage 1: Getting the parts

Of course, the first part is finding the can in the right size. As I wrote, the diameter should be in the magical range of 70mm to 100mm. This number is govern by the oscillation of the radio wave inside that can (The wave in wireless 2.4 GHz). The depth of my can was 117mm, it was a little more than the minimum given. Basically, you need the can to be as deep as possible. Use this online calculator, to calculate the minimal depth, before having serious signal loss.

I found my can at the supermarket. It was supose to be used for storing coffie. there were good reports using wiskey cans. Just to make one thing clear – Pringles cans are too small fore the wavelength and they don’t last well anyway.

The copper I got in a normal electronics store (in this case “Kashayof” in Jerusalem). The calculator i mentond above, will give you the length and position of copper inside the can. My result is 43mm for distance from the base, and 31mm for length. Just make sure you get this right :) .

I also got there the N-type female connector, here is a picture so you can see it:

The wireless card i use is called Engenius EL-2511CD+ EXT2 (picture at the bottom), its pretty old, I am sure you can get now something better. It cost me about 45$, including shimpent, which isn’t much. It has an output of 200mW, Which meens its sensative to long ranges. Really, any card will be alright, but the higher the sensitivity and trasmission, the better.

I also had to get the pigtail cable from eBay, because my card uses a connection called mmcx. A getting this stuff in Israel is impossible. So I orderd it from Hong-Kong, and it cost me about 20$.

There are various qualities for cables, so you better pay attention (I had a low quality cable, its a LMA-100).

Part 2: Assembly

In this part, I’ll mostly use pictures, so you can see all the step (its more effective).

The first thing I did was to take off the paint off the surface we are going to dill on. This wasn’t written anywhere on the net, however I thought I should do it just for safety:

After that, I marked the place where the hole was drilled:

For the next stage, my father will join us. Since he owns the Drill in our house – go dad!!!

Here is all the equipment ready, in the safist place on earth to drill – the kitchen (still, I don’t recommend doing this part at home, use a garden or something).

BTW, if you ever want to see how shakesphare look in Hebrew – the page under the drill is “A midsummer Night’s Dream”.

Of course, don’t forget to secure the can before you drill, this needs to be very precise:

Here I am drilling:

Here I am drilling

Making sure we are on the right track:

Making sure we are on the right track

More drilling:

more drilling

Creative drilling

We have a match of sizes! :

size match

The holes for the screws were added by someone else. I sould have done it myself, but I had no small drilling heads. If you have them, it should be easy:

All holes drilled

Stage 3: Soldering the copper wire to the N-type connector

This is the part I liked best, Soldering the copper wire to the connector. You need to get the wire as straight as you can. For some strange reason, there is no straight wire here for sale. So I did that myself.

Here is a picture of the soldering process:

Soldering the wire

Try not to make pointy edges with the solder, microwaves like smooth surfaces.

Here is a picture of my tidy working place:

Tidy working place

In the end, you better screw the connector to the can, should take a second of two. Here is a picture of the inside of the can, once all is assembled:

Inside of cantenna

And here is a picture of the final product:

cantenna on tripod

And here is a closeup on the connector:

N-type connector on cantanna

stage 4: configuring the card on Linux

The card uses the module hostap_cs. this module works well, and as of kernel 2.6.x is inside the kernel source.But for some reason, it didn’t work right away. It drove me nuts, took me about to days to surf in windows (oh! the shame), but in the end, I figured it out, well 2 problems. The first was that the irq adress was taken, so I fixed that adding the following line in /etc/pcmcia/config.opts :
exclude irq 5 exclude irq 7 exclude irq 3 exclude irq 4 exclude irq 11 exclude irq 10

The harder part was because the card wasn’t working still. Ironically, I found that was because the driver was crashing with the other wifi card I had on the laptop. So i removed that module:
rmmod ipw2200

And thats about it, I found a linksys network not too far from me, about 1km away. And I can surf the net all thanks to a coffee can.

The End

Additional information:

How To Build A Tin Can Waveguide WiFi Antenna
Circular Waveguide Antenna for 2.45 GHz
The useful calculator

Comments»

1. Gerardo - March 25, 2008

Hey congratulations i will do the same i think in a week but however i didn’t get the pigtail cable and i couldn’t also get the elements like connector niether the cable to create one pigtail i will keep trying thanks for posting your proccess it will be very helpfull to me.

2. Antenna Manufacture - October 23, 2008

I am not an electrical engineer, nor do I have access to any fancy test equipment. I’ve built some antennas that worked for me and thought I would share what I learned. I have no idea if this is safe for your radio or wireless network equipment. The risk to you and your equipment is yours.

Building your Cantenna is easy, thank you so much for this!

Cheers,
Kenna

3. guysoft - October 23, 2008

Worked like a charm for over 2 years. All hardware Seems to be fine. However the cantenna did rust a little from the rain, and that lowers the conductivity.

Its basically plugging a big peace of metal to the antenna input. As long as you don’t put in any extra voltage or amperage, you would have to be pretty clever to make any damage. The wifi card was built for external antennas.

4. Joao Marcos - December 5, 2008

I would like to build an antenna Catenna for the frequency band of 7 to 8 GHZ. How can I get the calculations. Thank you

5. Afief Halumi - December 31, 2008

Great guide:) and I thought this kind of stuff only happened in webcomics:

6. guysoft - December 31, 2008

Actualy, Afief, I follow XKCD, and I made the cantenna before that comic came out. I felt that day the comic was just for me :-) .

7. Kevin - January 3, 2009

Thanks for the guide! but is it necessary to solder the copper wire to the N-type connector? Cant you just slide it through? (I dont have a soldering gun)

8. guysoft - January 3, 2009

Kevin,
Yes its essential.
The copper wire is the element of the antenna. Thats where all the microwave light comes in to focus. Its your “eardrum”.

The cantenna was my first serious soldering job I guess. In general I can tell you that you won’t regret buying them, they are cheep and useful for many things.
Also, make sure there aren’t any pointy edges to the solder joint, it would make the reception better.

9. nol - February 22, 2009

Hello, Thank awesome.. I would like to ask how you create the end cable because in your picture only N type connector showing how about at the end did you put to your wireless router? or directly into your computer?

Can you please show me how.

Thank you so much

10. GuySoft - February 22, 2009

nol,
I am not sure I fully understood you (that second sentence needs a little punctuation).

If you look at the post you will see that I got the end cable, also known as “pigtail”, off ebay. And I did not use a router, I used a wireless connection card.

11. joe - August 28, 2009

What type of wireless connection card did you get?
I’m looking all over for one and I can’t find it.

GuySoft - August 28, 2009

If you will read the post you will see I used a high output power Engenius EL-2511CD+ EXT2. Today its quite an old model, any high output power card, with an external antenna connection will do.

12. Gary Schooley - November 4, 2009

All this talk about making cantennas but I have yet to see anyone post a WIRING DIAGRAM of how to wire a PIGTAIL. It goes from USB to (two conductor) N-connector, right? WHICH two pins in the USB connector does the N-connector connect to???

Thank you,
Gary Schooley

GuySoft - November 4, 2009

There is no schematic because its not related. The pigtail connects to the antenna connector of your circuit (you need a wireless card with an “antenna out” port).

13. dilupa - June 15, 2010

the calculator is cool
thanks

14. Ted - February 25, 2011

I have built a “cantenna” and just bought some cat 5 ethernet cable.
I have a Linkskys wireless-g 2.4 GHz router.

Question: which 2 of the 8 cable wires do in the router cable do I connect to the “N” connector (one to the center conductor and the other to ground)?

15. Eric Guth - August 12, 2011

40 years ago a “cantenna” was a paint can with a lid filled with mineral oil and a 50 ohm load sold by Heathkit. I had one under my desk as a dummy load for my low band station. FYI.

http://www.google.co.il/imgres?q=heathkit+cantenna&hl=en&gbv=2&tbm=isch&tbnid=xxHwxCbras568M:&imgrefurl=http://www.radiomuseum.org/r/heath_cantenna_hn_31.html&docid=NGxtk6ynPnjKIM&w=272&h=375&ei=qgpFTqnxC5CVswbH-72yBw&zoom=1&biw=1920&bih=892

-Eric 4Z5UG

GuySoft - August 13, 2011

I wonder what “glowbug” will mean in a few years :)

16. dave - January 4, 2013

not very clear on where to put the hole. my results are Lo = 125 mm Lo/4 = 31 mm
Lg = 143 mm Lg/4 = 36 mm but i have no idea what this means. lo? lg? huh?

GuySoft - January 4, 2013

Dimensions are located here:

17. zohair - July 31, 2013

can you fit a usb connector on it <since most devices have a usb port.

GuySoft - August 1, 2013

You can. The card used is also outdated by now. You can you this for example.

18. Avijit - August 17, 2013

Can i use this without wi-fi card in desktop


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