I got an ALFA AWUS036H for some wireless testing. I had trouble getting deauthentication to work. Eventually I ran across this post
I’ve encountered this error in the past many times. I own four different Alfa wireless NICs, and to get around this problem all I have to do is:
service network-manager stop
airmon-ng check kill && airmon-ng start wlan0
ifconfig wlan0 down
airodump-ng -f 1000 mon0 (as an example)
I usually double check wpa_supplicant is not running as it does seem to affect monitor mode.
You’re monitor interface (eg mon0) will still be available even after putting your primary wireless interface (eg wlan0) down. This fixes the -1 channel issue for me without patching any drivers.
This made it work for me
Also, to bump the trsx http://fl3x.us/blog/2013/01/12/setting-alfa-awus036h-to-30-dbm-1w-in-backtrack-5-r3/
Also, this command is useful after a capture
wpaclean <What you want the output cap file to be called> <cap file to clean>