10-24-2005, 01:53 PM
| | Re: wmi script to display signal strength
"bjs555" <firstname.lastname@example.org> wrote in message
>I couldn't get Netstumbler to work with some of my cards and dongles
> so I did some searching on the net and learned that a wireless card's
> signal strength is available as a WMI (Windows Management
> Instrumentation) value. So I put together this quick and dirty script
> that gives a continuous real time display of received signal strength
> for an active wireless connection. It's worked with all my clients,
> even ones that don't work under Netstumbler. I'm posting it here
> thinking that maybe someone else will find it useful. Perhaps someone
> will suggest improvements too.
> To use the script, just paste the text below into an editor like
> Notepad and save it with the name bjs555monitor.vbs. Then open a
> command window and navigate to the folder where you saved the script.
> Start the script by typing cscript bjs555monitor.vbs. Stop it with
> Ctrl + C. If you try to run it outside of a command window, it will
> work, but you'll only get updates when you press OK and you'll have to
> shut it down by pressing Ctrl+Alt+Del and killing the Windows Script
> Host task or rebooting. You should be connected to an access point
> before you start the script.
> Here it is:
> 'This script will continuously display the received signal
> 'strength of an active wireless connection in a command
> 'window. The update rate is once per second. Start it by
> 'typing cscript bjs555monitor.vbs at a command prompt.
> 'Stop it by pressing Ctrl + C. If you paste this script into a
> 'text editor, just save it with the name bjs555monitor.vbs
> '(or anything ending with .vbs) so that Windows will recognize
> 'it as a vbscript file.
> set objSwbemServices = GetObject("winmgmts:\\.\root\wmi")
> do while 1
> set colInstances = objSwbemServices.ExecQuery _
> ("Select * From MSNdis_80211_ReceivedSignalStrength "_
> & "Where Active = True")
> for each objInstance in colInstances
> signal = objInstance.Ndis80211ReceivedSignalStrength & " dBm"
> wscript.echo signal
> I found out something interesing using this script. I have a Linksys
> WUSB11v4 radio that I tried it on. When I look at the output, I see
> that all readings are multiples of 5 dB. It seems that the Linksys
> client doesn't report signal strength with resolution better than 5
> dB. The other 2 radios I tried it on (Zonet ZEW2501 and Hawking
> HWU54G) both showed readings with resolutions of 1 dB. I'd be
> interested in finding out if all Linksys products show only crude
> approximations of signal strength.
My Linksys WMP54GX mimo PCI adapter shows 1 dB resolutions. Your script is
less intrusive than Netstumbler for aiming my antenna since it doesn't
interupt Windows Wireless Zero Config. Cool. Thanks!