unable to configure wireless (iwconfig error)

[Charles E Blair <c-blair@illinois.edu>]

   The Jessie installer did not give me an
option for wireless (using ethernet).  I
subsequently saw, when starting the computer,
a message about missing ath3k firmware.
I used aptitude to install atheros and this
message has gone away.

   I then tried to use wifi-radar.  This recognized
the relevant names of LAN access points, but seemed
to freeze on what I think was search for DHCP.
It never got as far asking me for a password.

   I then tried

iwconfig wlan0 essid "relevant name" key s:password

and got the message

Error for wireless request "Set Encode" (8B2A) :
    SET failed on device wlan0 ; Invalid argument.

ls /dev/wlan0 does not show anything.