I’d run into this as a problem once when I was staying in temporary corporate housing in Los Angeles. The internet provided in the complex was on Channel 6, and someone in a neighboring unit was running their own network on Channel 6 with a stronger signal. Since the main signal was to be my provider and I could not change off the given channel – I had to knock on all the doors of the apartments near by until I found the guy – and helped him to choose a different channel to run his network (which helped him out because he was running pretty slow on Channel 6).
My point is this: a simple tool to track signal strength and identify channels is really mandatory for your toolbox. Check out this new one that is pretty hidden inside Mac OSX Mountain Lion. It could be a lifesaver for you!
If you have OS X 10.7 or above (Lion or Mountain Lion), a handy but hidden built-in utility can monitor your network’s performance and show your network’s signal strength.
OS X Daily has posted the instructions for running the Wi-Fi Diagnostics tool. To find the tool, either go to the folder /System/Library/CoreServices—or hold down the option key while clicking on the Wi-Fi icon in your menu bar and select “Open Wi-Fi Diagnostics”
Once you locate the tool, I recomend that you copy the app to your utility folder to make it easier to locate next time.
For Mountain Lion users only: Ignore the first screen and hit Command+N to open the “Network Utilities” window. Then Hit “Wi-Fi Scan” and you’ll be presented with a list of all the networks near you—even ones that are hidden, as well as their channel, security, and signal and noise levels.
For Lion users Use the Monitor Performance tool on the front screen and hit Continue. You’ll also get a list of networks and the signal/noise info. (More screenshots at Technorati.)
If you have competing networks on the same channel, you could possibly improve your reception by changing your channel on your router to one that’s not used.
Click on the Performance tab if you’re using Mountain Lion to see a chart of your live signal strength and noise meter (as well as network traffic). Basically, the wider the gap between the yellow and green lines, the better.
This could help you decide on if you need to do some adjustments to boost your Wi-Fi, such as moving your router to a different location or making your own antenna booster.
Original info: OSX Daily