Use a laptop as a mobile wireless power meter

Apr 08, '10 07:30:03AM

Contributed by: ALT147

This hint is for people trying to optimise their wireless signal reception in strange places. I recently had to get a wireless network operating over 100 meters away from the base station, and in a metal shed -- not the best environment for microwave communication!

This hint basically does the same job as AP Grapher, but can be run from the command line or over SSH -- so I was able to have someone else carry my MacBook Pro around the shed while I stayed near the wireless router and fiddled with its antennas.

I ssh'd into my MacBook Pro from a computer at the router, and ran the following command in Terminal:

while x=1; do /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | grep CtlRSSI; sleep 0.5; done
This periodically displays the received signal strength indicator (RSSI), basically the power of the microwave radio signal from your router.

The value is in dBm, which is a logarithmic scale so that an increase of 10 units means a factor of 10 increase in power; an increase of 20 means a factor of 100 increase in power; etc. Watching this reading, I was able to position the router and antenna for maximum signal strength at various places in the shed.
The airport -I command alone displays other useful information about your airport connection, like the network name, channel, authorization mode, and the noise on the microwave signal.

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Mac OS X Hints
http://hints.macworld.com/article.php?story=20100405162603767