Ubuntu 12.04 test OK!
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example :
set Tx-Power in dBm :
iw dev wlan0 set txpower fixed 0
iw dev wlan0 set txpower fixed 30
restore to default:
iw dev wlan0 set txpower auto
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also to test this (work too):
iwconfig:
iwconfig wlan0 txpower 0
iwconfig wlan0 txpower 17
