DIY Wifi Extender - Cantenna build with a stand.

This antenna is one of the easiest and cheapest things you could build to extend the range of your wifi network.  Most of the materials are probably sitting in your cupboard right now so it really can be built on a shoestring budget.

Bill of Materials:

Two milo tins or similar
F-Type chassie mount
Pig tale for F to Sma
Short piece of copper wire

Tools:

Tin snips
Can Opener
Soldering Iron
Drill
Drill Bit

Original content avaliable at  BudgetHack.com
 

Step 1: DIY Wifi Extender - Preparing the cans

Now you can build your cantenna with just one tin but chances are you wont meet the suggested overall minimum 3/4 wave length required when using the centenna calculator.  So first thing to do is go to the cantenna calculator and enter the diameter of the opening of your can in mm.  You will see the overall length on the can down the bottom,  if your single can is too short then you will need to use two, Don’t worry if you a little over or under length but it should be fairly close.

Alright then what we want to do is remove the top of one can and the bottom of the other.  Once you have done this on the can with the top removed cut out a small strip approx 10mm across and 15mm down the can.     Then we are going to use this slit so we can push one can inside the other, The can with the slit will deform slightly but don’t worry about it at this point.

Comments

[mnc_co_uk]

I've used a similar design myself with good results. Impedence matching is an important part of the design. The whole of the transmission line, includung the antenna requires impedence matching. when building home brew designs like these demensions will differ from the blueprint.
Using some rf decouplers and high frequency diodes and an oscilloscope it is possible to measure the SWR.

A good match between your antenna and transmission line will result in a low reflected wave. If the reflection is high compared with the foward wave there is a bad match, poor performance will result and the dimensions of the antenna would need altering.

when building a killer antenna impedance matching shouldn't be taken lightly and it's good to know, if you spend time getting this correct, you'll be getting optimal performace out of your hard work.

[Dr.Bill]

If impedance of the antenna is too high or too low, the transmitter (router) will see the antenna as ah dead short resulting in high SWR that can burn up the final amp in the router transmitter.
So impedance matching is Very important. MFJ sells an SWR and impedance analyzer that will tell you when your antenna is perfect. MFJ-259B

[susovit]

I want to try this out but the cantenna calculator is lost???
The link doesnt open the calculator. ????

[frogman31680]

Interesting. Sorta like the pringles cans I have seen around.

I wonder if having a smooth interior or the ribbed kind affect the signal in any way.

Also, I don't use the coax connector for my wifi. I have a USB adapter... So i would have to adjust this somehow.

[Slim49]

According to my reading & due to the length of the 1/4 wave form,
the interior ribs will not be "seen" during the proprogation of the wave.
mine all worked A OK.
Mr. Steve

[Slim49]

Dude,
this one is so easy to do.
need a 18" USB extender. I wrapped a 1" band of aluminum around with 3" of handle below. the ribs are so within the shortest lenght of teh wave as to be no issue. made 2 of these. my friends rave over it.
get a 4" + or- can, I used a tomato juice can.
estimate where the face of the interior trace antenna is & its front facing direction.
cut a slot in the can 1.25" from the rear wall. need a friction fit of your USb donagel.
insert it up inside 1.25" or more, play with it.
You will get some "much improved" signal strenght & more signals that you could ever imagine.
I have built every one of these Wifi antennas.
Mr. Steve

[gora_ji]

Sounds really good... some of it I couldn't understand though.

How about an instructable????! ! ! !

[Slim49]

Go here:
www.turnpoint.net/wireless/cantennahowto.html
its teh best site of all.
read up at several sites.
search for : CANTENNA, lots of info already is out there.
even just getting the USB donagel inside most any can will jump up signal strenght & numbers of sites.
Luch,
Mr Steve

[Javin007]

Posting another completely different website on how to make the exact same thing is more than a little rude. Particularly when you add insult to injury by saying "its teh[sic] best site of all."

And as a side-note, having actually looked at this site, I can certainly say that no, it's not.  And this instructable is far superior.

[Slim49]

Whoops!
no insult intended!
I used elements off you instructable.:-)
Mr steve

[k4gdw]

I've never built one of these before, but as to your question about the coax connector, if your USB WiFi adapter has an external antenna connector, you'll need a coax jumper with the same kind of connector as is on your WiFi adapter. If you're adapter lacks an external antenna connector then I'm not certain how you'd be able to do this. You'd still need coax and you'd need to crack open the WiFi adapter and locate the antenna. Find where it connects to the board and solder the center conductor of the coax where the antenna connects and the coax shield would need to connect to ground. Assuming you were able to identify where to solder the coax, and are skilled enough at working with surface mount boards, it MIGHT work. However, you're just as likely to ruin your adapter.

Working with antennas isn't just a simple matter of hooking it up. A transmitter is designed for a specific impedance, measured in ohms. I'm not going to go into a treatise on antenna theory. A transmitter is designed to use an antenna system that has a specific impedance. If the antenna system's characteristic impedance doesn't match the transmitter, then you have an impedance mismatch which can, if the mismatch is too large, cause physical damage to the final transistors in the transmitter.

[budgethackdotcom]

Thanks for your replys, as far as the ribbing on the can I dont thing this is an issue because if you look at the opening of the can there is actually a lip which I think will compensate for the fact the inside isnt smooth. Also with the impedence if you use the correct 50 ohm cable etc the impedence should be fine also the transmitter should have an impedence matching circuit to prevent damage. Some of the usb wifi adapters can have an external antenna connector added as ive done this before but your right you have to be real careful.

[madworx]

awesome @_@ hahahaa..

[BIGHAIRYDUDE]

<><><><>^^^^^^^^@#@
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[nicky23]

Nice stuff. As I am on budget and want to connect with my friend with wireless I am thanking you for this post and I am off to create the cantenna.

[kashwak]

I have used a similar setup before when i lived 1 mile out of town. but instead of cans I used a old dish from dish network and made it to where i could move it around if needed.

[FuzzyBearGeek]

I really like it. For some reason, I've always loved cleaned out, tin cans. I use them quite a bit for holding nails, screws and repairing mufflers. ;)

[Pyrocantha]

Holding left over paint, loose craft parts,small amounts of dry pet food for travel...the list is so LONG for what they are good for! Coffee Cans ROCK!

[jimvandamme]

This can be tricky because the probe length to the bottom of the can is past a quarter wavelength so it will resonate pretty sharply. You could cut a slot and adjust the slot placement until it was optimized for your channel. That is, cut a slot horizontally in the photo above; there's no current across the slot so it doesn't change the pattern. You could put an inch slot no problem. Or put your USB adaptor in the slot.

Try putting a fatter probe for more bandwidth. At least match the diameter of the connector pin for better match.

Speaking of matching, the can looks like it has a narrower open end which would make a bad match or diffract out the end, so find a can with a straight open end. Prefer a smooth can, although it doesn't make much difference.

If you have an app that gives you signal strength, you can play with antenna parameters to your heart's content. Just remember that decibels are logarithmic; 10 dB is ten times but 20 dB is a hundred.

[raphaelkaplan]

Instead of using cans try round duct and an end cap. These items can be bought at Home Depot