Cantenna Workshop Followup – Pictures & Lessons Learned

I wanted to post a quick follow-up on the “Build Your Own Cantenna” workshop that I facilitated at the University of Advancing Technology as a part of their Tech Forum 2010.

While we limited the number of registrants to 15, we were able to sneak in a few others last minute because we had the available supplies and space.  All together, we made 18 cantennas.

We were building simple waveguide antennas using tin cans.  We used the instructions from Turnpoint Wireless.  I had acquired several different sizes and types of cans for the workshop.  I thought part of the fun would be the experimentation. While it says it in the instructions, cans with a diameter of less than 3.25” do not work.  This is because you need to place the antenna element at a specific point on the can related to the ¼ wavelength of the 2.4 GHz frequency.  There were a few small cans (for canned veggies) that we tried where the diameter was less than 3” – when we made the measurement of where to place the antenna connector, we found out the can was not long enough!

Also, the instructions call for #6 ¼” nuts and bolts.  I bought the N-Type connectors from Fleeman, Anderson, & Bird.  When they arrived, I took one to a Home Depot to size out the nuts and bolts.  Size #6 seemed to be a little too big, so I downsized to #4 ¼ bolts.   If I did it over again, I would have actually bought #4 ½ bolts because the connector does not sit flush, due to the curve of the can.   This was the worst with the widest cans – they seemed to have the deepest curve. Because the connector wasn’t flush, the bolts weren’t long enough to hold the connector in place.  We worked around this by cutting a much larger hole for the N-Type connector in the can.  We used a circular drill bit to accomplish this – my advice on this is to go slow and apply steady pressure, or you’ll severely warp the opening as the bit goes through the can.

Here are a few photos from the workshop:

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4 comments so far

  1. Alessandra on

    Interesting!
    What is the optimal can size from your tests?

  2. wifijedi on

    Right in the 3.5″ – 4″ diameter range. Also depends on how long the can is. You really need to use the calculator in the instruction (linked from my article) to calculate the 1/4 wavelength for any particular can and then ensure it’s long enough.

  3. Alessandra on

    it is much wider than the pringles can that we heard about years ago…

  4. wifijedi on

    You know, I’m not 100% sure, but I think the Pringles cantenna is more of a yagi-type, where this was a simple waveguide antenna. I didn’t find anything on this with a quick Google search, but you might be able to find instructions for the Pringles cantenna if you dig a bit deeper.

    Yes, the can’s I was suggesting are much wider than the Pringles can.

    Thanks for your participation on my blog – I appreciate it!


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