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Old Nov 15, 2010, 05:15 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Mini-HowTo
The "Cantenna": 7dbi in 10 minutes!!!

This is a tutorial for the cylindrical waveguide antenna or the "Cantenna" as it is often referred to. This is very popular in Wifi as it is extremely easy to build. This antenna has a 70 degree cone that it receives directly in front of it.

In this tutorial, I will build a 2.4 GHz cantenna out of two common soup cans. A 1.3 GHz unit can be built with one of those large 5 quart tomato cans that you can find being throw away daily at your local Italian restaurant

This antenna can be used as a tracking antenna in my DIY antenna tracker tutorial

-Alex
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Old Nov 15, 2010, 05:22 PM
Engineer for Christ
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Amherst, VA
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Find your can

The first thing you need to do is find a couple of tin cans and a piece of coaxial cable. Ideally you want the can diameter of the cans to be between 3 and 3.75" (75-95mm). I used Campbell's soup cans as they are 3.05" inner diameter.

Pour the soup out into a bowl and place in the microwave. While your dinner is heating, remove the labels from the cans and rinse them out. Then remove the bottom from one of the cans with a can opener.

Once done, your soup should be ready. Sit down and eat
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Old Nov 15, 2010, 05:30 PM
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United States, FL
Joined Oct 2005
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Will you please do a "how to" for an antenna that is ideal to place on a tracker, has a 50 degree cone, has more than 15dbi, and works for 900mhz?

I saw a version of your bi-quad. It was a quad-bi-quad.

Oh - and will you make the above for me?
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Old Nov 15, 2010, 05:37 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Join the cans

Now that you have a full stomach, you may join the cans. You can use a soldering iron if you like. you can even use your gas stove (if your wife isn't looking) or your grill. Personally, I prefer a torch. It's quick and really easy.

I put a bead of flux around the rim of both cans and placed them together. Then I heated up my soldering iron and made a few quick dabs of solder (it took about 30 seconds before the solder took).

Now fire up the torch and melt down the solder. Roll the can as the solder flows.
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Old Nov 15, 2010, 05:38 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Drilling the hole

Now you need to drill a hole for the cable. Measure from the base of the can, not the bottom lip. The location of your hole depends on your can diameter. Below is a quick list:

3" - 3.75"
3.05 - 3.31" (my Campbell's soup cans)
3.10 - 3"
3.15" - 2.79"
3.2" - 2.62"
3.25 - 2.49"
3.3" - 2.38"
3.35" - 2.28"
3.4 - 2.2"
3.45 - 2.13"
3.5" - 2.07
3.6" - 1.95"
3.75" - 1.85"

You can also use this calculator if you wish: http://www.turnpoint.net/wireless/cantennahowto.html

Now drill your hole at that location.
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Old Nov 15, 2010, 05:48 PM
Engineer for Christ
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Making the feed

Now it's time to make the feed and active element. This is really easy. Strip your coaxial cable so that 1/4 wavelength is showing.

Your 1/4 wavelength can be computed as:

2808/f in MHz = length in inches
or for you metric folks
71323/f in MHz = length in mm

So for 2.4GHz (2450MHz) this computes to 1.146" or 29mm

Now fold back the shield and trim it to 1/2".

Insert the cable into the can and solder the shield to the can.

That's it! you now have a 7dbi waveguide antenna! Nothing to it

-Alex
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Old Nov 15, 2010, 05:51 PM
Engineer for Christ
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Amherst, VA
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Q&a

Q: Will you build this for me?
A: No. This is really easy. I mean incredibly easy. If you can get an FPV system working, this should be a walk in the park.

Q: What if I have a can that doesn't fit the dimensions?
A: Efficiency will drop some. I can't say how much. Cantennas are hard to model.
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Old Nov 15, 2010, 05:53 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by Blue Chip View Post
Will you please do a "how to" for an antenna that is ideal to place on a tracker, has a 50 degree cone, has more than 15dbi, and works for 900mhz?

I saw a version of your bi-quad. It was a quad-bi-quad.

Oh - and will you make the above for me?
That antenna doesn't exist. 15 dbi and a 50 degree cone is impossible. You would need an efficiency of 200%, thus solving the world energy crisis.

The double BiQuad has a 40 degree beam and is 13dbi.

Will I make this for you? - See Q&A

-Alex
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Old Nov 15, 2010, 05:57 PM
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Cool! Does an oven work better than a microwave to warm the soup though?
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Old Nov 15, 2010, 05:59 PM
Thou who know not
Po73's Avatar
USA, MI, Mason
Joined Jul 2010
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Quote:
Originally Posted by rc-mike View Post
Cool! Does an oven work better than a microwave to warm the soup though?
A 2.4GHz VTX works best.
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Old Nov 15, 2010, 06:06 PM
Engineer for Christ
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Amherst, VA
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Quote:
Originally Posted by rc-mike View Post
Cool! Does an oven work better than a microwave to warm the soup though?
Only if you're not hungry. You can build the whole thing while you wait for your soup to warm up
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Old Nov 15, 2010, 06:12 PM
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Yeah, I guess so. However, I would probably do a better job if I wasn't in a hurry to get to the soup before it cools off.

I may try building one of these. Too cheap and simple not to give it a try.
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Old Nov 15, 2010, 06:16 PM
$#|+
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United States, CA, Orange
Joined May 2007
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i think you can squeeze more gain by adding a metal funnel to the front

like this one here

this is an A/C duct adapter from the home depot

Moe
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Old Nov 15, 2010, 06:44 PM
Engineer for Christ
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Amherst, VA
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That would increase gain. I don't know by how much though. I have seen a few with that on the end. However, that means you actually need to buy something...
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Old Nov 15, 2010, 07:04 PM
my karma ranover my dogma
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Edmonton,Canada Eh
Joined Jun 2007
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What happens if I heat the soup in the can first?

I mean... why go to all that trouble to take the soup out of the can?
Just toss the whole thing in the microwave....

Microwave ovens operate on 2.4ghz.... right?

So that would tune the antenna before you even built it....

Seriously, Thanks for all your great tutorials Alex!

This one has got to be the easiest yet!
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