Ubiquiti SRC & MadWifi

Hi folks !

I have an Ubiquiti Super Range Card and I wanna use it under Linux System.. so I've downloaded MadWifi NG, Madwifi was succesfully installed.
Card is detected as "ath0"..but when I perform a "iwlist ath0 scan" the result is "no scan result" in every case..and I've noticed that Tx/Rx Power is set to 0 !
So...I've downloaded Madwifi Old Version and in this case the card seems to work but with less less power than effective power (300 mw).
Do you know what could be the problem?

I use a PowerBook G4 with Slackintosh 12.0 .

Thanks

Ciao