"Hidden" Wi-Fi Diagnostic Tool

ByMike Moffit

In my internet wanderings I discovered a few articles pointing to a mysterious Wi-Fi diagnostic tool that Apple snuck into Mountain Lion. A common reason people check machines into our service department relates to perceived poor Wi-Fi service, so I wanted to share this with our readers.

This tool is available for anyone running 10.7 or later. The tool is slightly different for Lion users than it is for Mountain Lion users. If you’re running Mountain Lion (10.8) hold down the option key on your keyboard and click on the Wi-Fi icon in your menu bar. It’s the one that is pie wedge shaped. You’ll see a menu item called “Open Wi-Fi Diagnostics.” If you’re running Lion you’ll need to navigate to it manually by going to the following folder: /System/Library/CoreServices. As with most applications you don’t want to move it from it’s original install location, so do not move the application from that folder! If you want to make a shortcut to it to keep somewhere else that’s fine.

If you’re on Mountain Lion press Command+N to open a utilities window and then click on “Wi-Fi Scan.” For Lion users you’ll want to use the Monitor Performance tool. Both will give you the list of available networks as well as their signal and noise information.

Here’s some information from Technorati on how to tell if you have a good signal:

“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.”

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