Reduce WiFi Transmit Power of a Raspberry Pi

The following command can be used to check the WiFi transmit power of your Raspberry Pi running Raspbian:

iwconfig wlan0

Output:

wlan0 IEEE 802.11 ESSID:"SSID" 
Mode:Managed Frequency:2.437 GHz Access Point: XX:XX:XX:XX:XX:XX
Bit Rate=5.5 Mb/s Tx-Power=10 dBm 
Retry short limit:7 RTS thr:off Fragment thr:off 
Power Management:on 
Link Quality=40/70 Signal level=-70 dBm 
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 
Tx excessive retries:19 Invalid misc:0 Missed beacon:0



Here the transmit power is Tx-Power=10 dBm. The following command can be used to change the WiFi transmit power:

sudo iwcofig wlan0 txpower 1

Then running the previous command will give the following output:

wlan0 IEEE 802.11 ESSID:"SSID" 
Mode:Managed Frequency:2.437 GHz Access Point: XX:XX:XX:XX:XX:XX
Bit Rate=5.5 Mb/s Tx-Power=1 dBm 
Retry short limit:7 RTS thr:off Fragment thr:off 
Power Management:on 
Link Quality=40/70 Signal level=-70 dBm 
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 
Tx excessive retries:19 Invalid misc:0 Missed beacon:0