Hello, first off im using a laptop with Interface:wlan0 Chipset:Atheros Driver: ath9k - [phy0]
Aircrack-ng has been installed and im following this guide and when i have to enter the command sudo airodump-ng mon0 I get the following

Interface mon0:
ioctl(SIOCGIFINDEX) failed: No such device

What does this mean? Google has not helped me enough on this one.