|Tip 127||See Every Wi-Fi Detail|
Once you’ve joined a wireless network, hold down the Option key and click the Wi-Fi icon at the top right of the screen. Along with the usual options of switching networks, you’ll be shown a list of interesting technical details about the connection.
Checking Signal Strength
For information about signal strength, pay particular attention to the line labeled RSSI (for received signal strength indication), about halfway down the list. It’ll probably be a minus figure, like -40 or -73. The closer this figure is to 0, the stronger the signal. So, -30 is better than -50. The scale is from -100 to 0. My experience is that networks beyond -80 are impossible to connect to, but your mileage may vary. See Figure 22, Viewing the technical details of a Wi-Fi connection.
Checking Data Transfer Speeds
The transmit rate figure is also worth paying attention to. It tells you the maximum data speed possible with the connection. For example, at the moment, my MacBook Pro’s transmit rate figure reads 54, indicating a 54Mb/sec connection speed and also indicating I’m connected to the Wi-Fi base station using 802.11g—the older but still widely used Wi-Fi standard. Using a more modern 802.11n router over a good connection, the transmit rate figure will read anything up to 300, indicating speeds of up to 300Mb/sec.
Performing a Wi-Fi Diagnostic
OS X has a hidden Wi-Fi diagnostics tool that lets you monitor the performance of the connection, among other things. It’s primarily for those who understand the technical details of how Wi-Fi works, however. To access it, again hold down Option while clicking the Wi-Fi icon, and then select Open Wi-Fi Diagnostics at the bottom of the menu that appears. (If you don’t see this option, open a Finder window, hit Shift+Command+G, and type /System/Library/CoreServices. Then double-click the Wi-Fi Diagnostics entry in the list of files.)
Click the Learn More button in the program interface to discover what each available option in the program offers. It’s possible to monitor signal strength over a period of time using the Monitor Performance option (hit Command+5), for example, or to capture raw frames.
Of significant interest if you experience Wi-Fi problems is the Wi-Fi “stumbler,” which will detect all Wi-Fi base stations in the vicinity—even hidden ones that don’t broadcast their station ID (SSID). You’ll also see technical details about each station, such as the channel it uses, its signal strength relative to your position, and what kind of encryption it uses (i.e., WEP, WPA, or WPA2). To invoke the stumbler, hit Command+6 while the Wi-Fi Diagnostics program is running. The scan will take a few seconds to complete and will appear in a new window—see Figure 22, Viewing the technical details of a Wi-Fi connection.
Just close the window when you’re done and then quit the Wi-Fi Diagnostics program.