I would like to begin testing and working with BackTrack. I have heard that the Alfa AWUS036H wireless adapter works well with BackTrack and allows for packet injection. This adapter, however, is only a wireless b/g adapter. I was curious if there was something similar to this adapter that would allow for packet injection, work on Windows and Linux (especially BackTrack), and would support wireless b/g/n? Support for wireless a would be a plus too, but not a requirement. Also, are there any replacement antenna's that one should consider using with this device?
The first place to look would be the BackTrack wiki: http://www.backtrack-linux.org/wiki/index.php/Wireless_Drivers
There is also a strong community who will provide guidance on the Backtrack forums.
I personally used the following http://www.amazon.com/Edimax-EW-7811Un-150Mbps-Raspberry-Supports/dp/B003MTTJOY with no issues. combining this with hostapd on top of Kali Linux gives you a very powerful wireless pentesting infrastructure