Arduino Robotic Directional Wifi Scanning

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.