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Mac OS X Wireless Signal Strength in Snow Leopard

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Mac OS X Wireless Signal Strength in Snow Leopard

Mac OS X Wireless Signal Strength in Snow Leopard The AirPort item in the menu bar now includes signal strength for all available wireless networks, so you can see which access point has the best signal before selecting it. Four signal bars appear in the AirPort status icon in the menu bar. The more bars that are black, the higher the signal quality. The bars do not indicate the connection rate, as this will vary according to your environment. [source]

Mac OS X Wireless Signal Strength in Snow Leopard

While I like the simplicity of the four levels of signal strength above I sometimes need signal strength in dBm. dBm is a more granular way of describing the wireless signal strength.

dBm (sometimes dBmW) is an abbreviation for the power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW). It is used in radio, microwave and fiber optic networks as a convenient measure of absolute power because of its capability to express both very large and very small values in a short form. Compare dBW, which is referenced to one watt (1000 mW). In the more granular information about the signal strength. [wikipedia]

Wireless Signal Strength Using the Snow Leopard Menu Bar

Clicking the option key and the signal strength menu icon will display detailed information about the currently connected wireless network.

Mac OS X Wireless Signal Strength in Snow Leopard

PHY Mode – is the type of 802.11 WiFi network (802.11 a/b/g/n)
BSSID – is the MAC address of the access point
Channel – current 802.11 channel
Security – authentication and encryption type
RSSI – received signal strength indicator, aka the signal signal strength in dBm. The closer the number to 0 the stronger the signal.
Transmit Rate – the data rate of the current connection

Airport Signal Strength in dBm Using “About This Mac”

Wireless signal strength is also available using the About This Mac menu bar option and navigating to Network > Airport section.

Mac OS X Wireless Signal Strength in Snow Leopard

RSSI Signal Strength Airport Command Line Utility

The airport utility is located at location below.

/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I

Will provide information about the current wireless connection.

$ airport -I
     agrCtlRSSI: -64
     agrExtRSSI: 0
    agrCtlNoise: -91
    agrExtNoise: 0
          state: running
        op mode: station 
     lastTxRate: 48
        maxRate: 54
lastAssocStatus: 0
    802.11 auth: open
      link auth: wpa-psk
          BSSID: 0:b:55:6:6f:2f
           SSID: SSID
            MCS: -1
        channel: 1

Wireless Signal Strength Using Graphical Tools

WiFi Scanner is the most feature rich and complete WiFi scanning app on the app store and is a great tool for personal use and for IT professionals. All features available on 10.6 and later (Snow Leopard and Lion)

WiFi Scanner is an 802.11/WiFi wireless scanner and connection manager for 802.11 a/b/g/n networks. WiFi Scanner is an easy to use tool for designing, verifying, and troubleshooting WiFi coverage. The tool provides information such signal strength, noise, manufacturer name based on MAC address prefix of device (OUI), and AP channel assignments for WiFi access points.

WiFi Scanner can also be used a security tool for detecting unauthorized and rogue access points. The app includes an audio alert (beep) feature that is directly related to RSSI / access point signal strength. This feature can be used to track down devices by listening for beep frequency instead of watching app screen.

Scan Tab

Mac OS X Wireless Signal Strength in Snow Leopard

• Scans 802.11 a/b/g/n
• Scans both 2.4 GHz and 5 GHz bands
• Displays channel number per device
• Indicates if channel is in 2.4 GHz or 5 GHz channel band
• Detects devices operating using 20 MHz or 40 MHz channel bandwidth
• Correctly identifies if 40 MHz channel width is above (channel, +1) or below (channel, -1) primary channel
• Auto starts scanning when app is launched
• Stop / pause / resume scan / start new scan
• Plot RSSI value for SSIDs for a single, multiple or all detected access points
• Can toggle on / off RSSI value on plot
• Sort any column and app remembers on next open
• Move columns to desired position and app remembers position on next open
• Copy/Paste rows of results into own documents
• Expandable/collapsible graph area
• Expandable/collapsible table view area
• Join button per SSID that allows user to join WiFi network
• Option to merge scan results from similar SSIDs into single strongest signal SSID
• The tool reports signal strength in dBm

Test Name/Scan Name

Mac OS X Wireless Signal Strength in Snow Leopard

• Left column automatically logs each scan session when stop/play is clicked using “Scan #” format
• Double click default scan name to edit and customize name. For example Floor 1, Floor 2, etc
• Review previous scans while app is open. Great for comparing scans per floor/area

Monitor Window

Mac OS X Wireless Signal Strength in Snow Leopard

• Double click results row to view new window with RSSI and graph. See second screen shot below.
• Audio beep in monitor window increases as RSSI increases for access point being tracked. Very handy for rogue access point tracking

Interface Info Tab

Mac OS X Wireless Signal Strength in Snow Leopard

• Turn interface on/off
• Disconnect from access point but leave interface enabled
• Detailed information about connected WiFi network
• Signal and noise plot for connected WiFi network
• Create Ad-hoc network / IBSS
• Transmission rate for connected WiFi network
• Displays supported channels for computer
• Displays supported WiFi types for computer (802.11 a/b/g/n)

Remote GPS Tab

Mac OS X Wireless Signal Strength in Snow Leopard

• UDP listener for use with Sensor Pro remote GPS iPhone app

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Filed under: WLAN Design, WLAN Site Survey, WLAN Tools

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