Comment 87 for bug 971809

Wifi connection with an Atheros AR9485 card is very unstable (bad quality, and very bad range).
At the beginning connection quality stays where it reasonably should be, but after few seconds it drops to poor values :

:~$ sudo iwconfig
lo no wireless extensions.

wlan0 IEEE 802.11bgn ESSID:"Pluff"
          Mode:Managed Frequency:2.412 GHz Access Point: 94:0C:6D:C5:8B:B4
          Bit Rate=54 Mb/s Tx-Power=15 dBm
          Retry long limit:7 RTS thr:off Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=46/70 Signal level=-64 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:0 Invalid misc:4 Missed beacon:0
......
:~$ sudo iwconfig
lo no wireless extensions.

wlan0 IEEE 802.11bgn ESSID:"Pluff"
          Mode:Managed Frequency:2.412 GHz Access Point: 94:0C:6D:C5:8B:B4
          Retry long limit:7 RTS thr:off Fragment thr:off
          Encryption key:off
          Power Management:off
          Bit Rate=54 Mb/s Tx-Power=15 dBm
          Link Quality=28/70 Signal level=-82 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:0 Invalid misc:4 Missed beacon:0

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This was tested on (cat /proc/version) :
- Linux version 3.5.0-17-generic (buildd@allspice) (gcc version 4.7.2 (Ubuntu/Linaro 4.7.2-2ubuntu1) ) #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012
which is the standard Ubuntu 12.10 kernel and
- Linux version 3.7.0-999-generic (apw@gomeisa) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #201210210405 SMP Sun Oct 21 08:05:46 UTC 2012
which is the latest upstream kernel

The exact name of the network card is (lspci) :
02:00.0 Network controller: Atheros Communications Inc. AR9485 Wireless Network Adapter (rev 01)

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This bug is related to Ubuntu Launchpad bug n°971809.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/971809