On my MacBook Air, MacBook Pro and Mac mini, the status bar includes the standard "radiating sector" wifi icon which you can click on to select a wifi network, or Option-click on to see additional info such as BSSID, Channel, RSSI, transmit rate. The icon itself show 1, 2, 3 or 4 lines in black to indicate how good the wifi connection is. My question is this - what do the different numbers of lines indicate? Is it various thresholds in signal-to-noise ratio? Transmit speed? RSSI? Bit-error rate?
The built-in WIFI Diagnostics app (I'm running Mountain Lion 10.8.4) tells me that RSSI is -65 to -70 dBm, noise is between -85 and -90 dBm, SNR is between 10 and 25, Quality is either Good or Excellent, and Tx Rate is between 1.0 and 11 Mbps.
The reason for asking is that I'm at the end of a pretty poor wifi connection right now, but the wifi icon is constantly showing all 4 lines in solid black! Why?