According to
ifconfig(8), you are setting your wireless NIC to an ESSID of "default" -- if you don't have an Access Point configured to broadcast ESSID "default" your NIC will not connect to your network.
If you want your NIC to find the nearest Access Point, do net set your nwid at all, or set it to "".
If you actually
do have a WiFi network called "default" then you are configuring your connection correctly. If so:
- ath(4) discusses the AR5210-AR5212, not the AR5213.
- Please post your dmesg. You can obtain it either via dmesg(8) or from the contents of the /var/run/dmesg.boot file.
- Please post the output of /etc/hostname.ath0 as well.