lifehacker has an article showing us a Mac hidden tool that can show the wireless networks around you. The tool is called: Wi-Fi
Diagnostics tool.
First, you can 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..."
Open the tool (if you browsed for it by folder, you can copy the app to your Utilities folder or Dock first).
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.
Technorati has
an article on how to use this tool as well.
The "Signal" number specifies the signal strength
between your Mac and the Wi-Fi access point or router. The higher this
number is, the better. But note that these are negative numbers so a
Signal of -60 is higher (and stronger) compared to a Signal of -80. The
Noise number represents the amount of wireless noise that can interfere
with the Signal. In this situation, we want lower numbers. So again,
because we have negative Noise numbers, a Noise level of -94 is better
than one of -90.
Finally, we can take the Signal and Noise
numbers to come up with a Signal-to-Noise ratio (SNR) for our wireless
connection. So for example, If I have a Signal level of -60 and a Noise
level of -91, the difference between these two numbers is 31. The higher
the SNR is, the better the Wi-Fi performance will be. Typically a SNR
of 25 or higher will give you great Wi-Fi performance.
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.
*
Another article about this tool on OS X Daily.
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