On 08/23/2012 11:19 AM, Patrick Connolly wrote:

Mohammed,
      Thanks very much for the response.

    Yes I get "Operation not supported":

# iwconfig wlan0 modu 11b
Error for wireless request "Set Modulation" (8B2F) :
     SET failed on device wlan0 ; Operation not supported.

    ...so what does this mean; what are my options here?  In view of
the fact that the capability of changing modes (from 'g' to 'b'
...etc.) is an essential requirement, am I using the wrong driver
...is there a different driver that supports this chip?  Or is it that
there's no driver that supports this chip so that I would have to put
this functionality into ath9k myself if I want it?

Adding that functionality should not be necessary. The simple command

iw dev $WIFIDEV set bitrates legacy-2.4 1 2 5.5 11

will restrict the device to 802.11b rates, which I think is what you want. This 
command does not involve the device driver, but sets the appropriate parameters 
in mac80211.

Larry