There is a simple way you can scan for available wireless access points using the free Apple Airport Utility application.
Once you have downloaded and installed the application. Then go into Settings and scroll down to AirPort Utility. Once you have done this you see the screen below.
To activate it all you need to do it toggle the switch Wi-Fi Scanner. Once it is activated then load the AirPort Utility Application, in the top right hand corner in Blue you will see Wi-Fi Scan.
Press this once then you can choose to scan Continuous or every X amount of seconds from 10 seconds upward on the slider. Once you have the right time your want click Scan.
You can see below the different things it displays. You can see the MAC address, the noise and Channel etc quite a lot of useful information.
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