Switch off radio on the Atheros AR5006X Wlan card

Hi,

I am using MAdwifi driver 0.9.4. I am not able to switch off the radio of the Atheros AR5006X Wlan card from a program. I am using the ioctl SIOCSIWTXPOW. IF i set the transmit power to 0, the radio is still on. Any help will be very useful.

thanks,
Shashi