May 132012
 

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I wanted to be able to locate wifi signals, so I built a directional antenna and strapped it onto my panorama robot. The waveguide style antenna built from a used can (explains the name cantenna) looked to be the easiest to build. I bought a pigtail with an N male connector to RP-SMA male connector.  I plugged this into my Alfa Network AWUS036NH. I then fired up inSSIDer and used PuTTY to control the Arduino sketch and aim the antenna.

The signal strength was not what I expected to see at all. I assumed this antenna was directional and would be strongest when I pointed it directly at the AP. It was strongest pointing at about a 45 degree angle to the left of the access point. I’m a complete n00b when it comes to RF, so any feedback on why I’m not seeing what i expected for results would be greatly appreciated.

Note: Will update post if/when I have an answer.

Update:

I am a complete n00b when it comes to build antennas. I goobered another can on there and it works a lot better. I have to give a great thanks to several redditors for pointing me in the right direction. I’m always impressed with how helpful people are. http://www.reddit.com/r/electronics/comments/tmtbi/attempting_wifi_direction_finding_with_a_cantenna/ Even better, I’ve got some reading to do now.

I’ve included links I found useful or interesting and more pictures.


Antenna Links:
http://www.turnpoint.net/wireless/cantennahowto.html
http://support.jefatech.com/cantenna/
http://sacra33.wordpress.com/2009/06/05/how-to-create-a-wi-fi-waveguide-antenna-booster/
http://dorkbotsf.wordpress.com/2009/05/06/homemade-antenna-redux/
http://hackaday.com/2009/07/07/various-cantenna-builds/
http://hackaday.com/2011/04/15/tactical-wifi-cantenna-needs-picatinny-rails/

Advertisement:

Aiming Antenna Links:
http://www.usbwifi.net/wifi-links.php?topic=steercan
http://hackaday.com/2006/08/28/steerable-cantenna/
http://web.archive.org/web/20070324051034/http://www.smithstuff.net/steercan/Steercan.htm
http://www.youtube.com/watch?v=nOcSG-1bjfg

Visualization Ideas:
http://wificamera.propositions.org.uk/
http://hackaday.com/2008/06/10/wifi-telescope/

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