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I often have trouble connecting to wifi with my MacBook Pro. To help identify the problem, I was wondering if there were any tools for measuring wireless signal strength.

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up vote 15 down vote accepted

If you're just looking for a quick signal strength number, option-click on the AirPort icon in the menu bar. Under the connected network you will see several pieces of information:

alt text

RSSI is your signal strengh in dB. Higher (closer to 0) is better.

If you're looking for noise or the signal strength for multiple access points, I suggest checking out iStumbler:

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You can get quite a bit of info from the command line, with the (well-hidden) airport utility. With the -I flag it'll tell you about the current network:

$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I
     agrCtlRSSI: -43
     agrExtRSSI: 0
    agrCtlNoise: -96
    agrExtNoise: 0
          state: running
        op mode: station 
     lastTxRate: 130
        maxRate: 130
lastAssocStatus: 0
    802.11 auth: open
      link auth: wpa2-psk
          BSSID: 0:24:1:0a:42:93
           SSID: My Wireless
            MCS: 15
        channel: 5

...and -s will show more info about other visible networks:

$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -s
                            SSID BSSID             RSSI CHANNEL HT CC SECURITY (auth/unicast/group)
                     My Wireless 00:24:01:fa:42:93 -44  5       Y  -- WPA(PSK/TKIP,AES/TKIP) WPA2(PSK/TKIP,AES/TKIP) 
                          hobbit 00:15:05:19:8a:03 -86  7       N  -- WEP 
                     My Wireless 00:24:01:ef:91:ab -75  3       Y  -- WPA(PSK/AES,TKIP/TKIP) WPA2(PSK/AES,TKIP/TKIP)

It doesn't have a man page, but if you run it without any options it'll list its options.

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System Profiler will list available Wireless Networks as well as the following information

  PHY Mode: 802.11n
  BSSID:    c0:3f:e:df:1b:be
  Channel:  6
  Network Type: Infrastructure
  Security: WEP
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If you find that your connection problems occur in the same location, you could use a tool like NetSpot that would let you visually see areas of low signal. NetSpot is free and available within the App Store.

See below for an example of how a map of your apartment's wifi signal could look.

Screenshot showing map of signal strength

Macworld reviewed Netspot and published a brief tutorial last year about how it could be used.

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Another, out-of-the-box way (at least on Mountain Lion):

  1. Click on the Apple (top left)
  2. About this Mac
  3. More Info
  4. System Report
  5. WiFi

This will show you all the info you want for all the networks in range, without needing to install additional software.

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Does this method show you the signal strength of visible WiFi networks? I can't confirm at the moment. – Dan J Mar 6 '13 at 20:49
@DanJ it shows Signal/Noise values! – Alex Mar 6 '13 at 21:38
yes it shows signal/noise (same as the graphic displays softwares) so you want the signal as high as possible while the noise as low as possible :) I know it is not as fancy as the graphic displays but you do not have to install some 3d party software – user44516 Mar 7 '13 at 10:56

I typically use WiFi Explorer. Its newer than iStumbler and provides the following features:

  • Easy-to-use, intuitive user interface.
  • Graphical visualization of the wifi environment.
  • Works with 802.11a, b, g and n wireless networks.
  • Supports 2.4 GHz and 5 GHz frequency bands as well as 20 and 40 MHz channels.
  • Signal quality estimations based on signal-to-noise ratio (SNR).
  • Accurate conversion from dBm to percentage (%) for easier analysis and optimization.
  • Export metrics and network details to CSV file format.
  • Full screen mode (10.7 or above).
  • Comprehensive help.
  • Runs in Snow Leopard, Lion and Mountain Lion.

It's available in the Mac App store. It's priced at .99 cents. Developers are responsive to questions.

enter image description here

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What a Jungle in Spain on the Costa de Soll Is this useful ? I am actually in a relatively small village, not in New York, or LA :)

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Can you add some more details about the tool the screenshot is from, where to get it from and why you recommend it? – patrix Mar 7 '13 at 18:13
You can see in the top bar that it's NetSpot. I think it might be intended as a response to the recommendation for NetSpot above. I like WiFi Explorer, as the channel view shows you (possible) congestion by frequency. – Tim B Mar 7 '13 at 18:26
I just tried the NetSpot and showed an example of my neighborhood :), than I UNistalled the netspot since it slows down my computer and as said above OsX already shows the needed information, not in so fancy form, but how often do you care about WiFi landscape, you just want the best signal to connect to and OsX shows that. – user44516 Mar 9 '13 at 18:06

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