Depending on the adapter you use it may be possible to increase its range. Keep in mind that if you can adjust the range of your adapter it is illegal to go above certain output level from country to country.
For example in the United States the max transmitting power allowed is 30dBm when a 6 dBi antenna is used. The max output also changes depending on the dBi of the antenna.
The next thing to watch for is overheating the adapter and destroying it. Most adapters are built to have a output of 20 dBm. If this is increased manually some adapters will become hot and burn up.
For these reasons a novice pen tester should leave an adapter at its default transmit settings. For those who feel comfortable pushing their adapter and know the hazards, here are the commands.
First find which Wlan your adapter is on and substitute it below if it is different.
airmon-ng
Option 1
Open terminal and run the following commands:
iw reg set BO
iwconfig wlan0 txpower 30
If above method gives a error then go use Option 2.
Option 2
ifconfig wlan0 down
iw reg set BO
ifconfig wlan0 up
iwconfig wlan0 channel 13
iwconfig wlan0 txpower 30
If the dBm does not change for an adapter than it most likely doesn’t have the ability to be modified.