Problema USB Wifi TP- Link TL-WN722N se conecta pero va lento Ubuntu 14.04

LTS vigente - 14.04 Trusty Tahr
Hola a todos, a ver si me podéis ayudar.
En mi nuevo PC de sobremesa he instalado Ubuntu 14.04, y como adaptador wifi TP-Link TL-WN722N porque había leido que funcionaba out-the-box con Linux.
La buena cuestión es que conectar conecta, normalmente al inicio del sistema con velocidad normal, pero al cabo de un par de minutos la velocidad cae drásticamente y ya no se puede navegar. Como ejemplo, al iniciar he puesto a descargar spotify que son 55 Mb y marcaba unos minutos, ahora indica 3h y 52'. He hecho un test de velocidad con speedtest-cli e indica 0.64 Mbit/s de bajada y 0.47 Mbit/s de subida. Problema de la red/router no debe ser porque justo al lado estoy navegando con el macbook sin problemas, y tenemos un netbook y un viejo portátil Toshiba (2002) que con Ubuntu 12.04 se conectan sin problemas.
Al hacer:

$ lsusb
Bus 003 Device 004: ID 0cf3:9271 Atheros Communications, Inc, AR9271 802.11n
$ lsmod | grep iwl
Responde en blanco, lsmod sí que responde una lista.
~$ lsmod
Module Size Used by
nls_utf8 12557 0
isofs 39837 0
uas 23159 0
usb_storage 66545 2 uas
ctr 13049 1
ccm 17773 1
rfcomm 69509 0
bnep 19624 2
bluetooth 446409 10 bnep,rfcomm
6lowpan_iphc 18702 1 bluetooth
arc4 12608 2
joydev 17393 0
hid_generic 12559 0
ath9k_htc 75131 0
ath9k_common 25638 1 ath9k_htc
ath9k_hw 446521 2 ath9k_common,ath9k_htc
usbhid 52616 0
snd_hda_codec_realtek 73089 1
ath 29006 3 ath9k_common,ath9k_htc,ath9k_hw
hid 110426 2 hid_generic,usbhid
snd_hda_codec_generic 68937 1 snd_hda_codec_realtek
mac80211 652718 1 ath9k_htc
cfg80211 494330 4 ath,ath9k_common,mac80211,ath9k_htc
snd_hda_codec_hdmi 47548 1
eeepc_wmi 13151 0
asus_wmi 24094 1 eeepc_wmi
sparse_keymap 13948 1 asus_wmi
mxm_wmi 13021 0
intel_rapl 18783 0
x86_pkg_temp_thermal 14205 0
intel_powerclamp 18823 0
coretemp 13441 0
nls_iso8859_1 12713 2
kvm 452043 0
crct10dif_pclmul 14307 0
crc32_pclmul 13133 0
ghash_clmulni_intel 13230 0
aesni_intel 152552 2
aes_x86_64 17131 1 aesni_intel
lrw 13286 1 aesni_intel
gf128mul 14951 1 lrw
glue_helper 13990 1 aesni_intel
ablk_helper 13597 1 aesni_intel
cryptd 20359 3 ghash_clmulni_intel,aesni_intel,ablk_helper
serio_raw 13483 0
snd_hda_intel 30469 5
snd_hda_controller 31056 1 snd_hda_intel
snd_hda_codec 139682 5 snd_hda_codec_realtek,snd_hda_codec_hdmi,snd_hda_codec_generic,snd_hda_intel,snd_hda_controller
parport_pc 32741 0
snd_hwdep 17698 1 snd_hda_codec
snd_pcm 104112 4 snd_hda_codec_hdmi,snd_hda_codec,snd_hda_intel,snd_hda_controller
mei_me 19696 0
mei 87875 1 mei_me
snd_seq_midi 13564 0
snd_seq_midi_event 14899 1 snd_seq_midi
snd_rawmidi 30876 1 snd_seq_midi
i915 905954 6
snd_seq 63074 2 snd_seq_midi_event,snd_seq_midi
tpm_infineon 17131 0
snd_seq_device 14497 3 snd_seq,snd_rawmidi,snd_seq_midi
snd_timer 29562 2 snd_pcm,snd_seq
drm_kms_helper 61574 1 i915
snd 79468 21 snd_hda_codec_realtek,snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_pcm,snd_seq,snd_rawmidi,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel,snd_seq_device
video 20128 2 i915,asus_wmi
drm 311018 5 i915,drm_kms_helper
soundcore 15047 2 snd,snd_hda_codec
shpchp 37047 0
i2c_algo_bit 13413 1 i915
ppdev 17671 0
acpi_pad 17942 0
mac_hid 13227 0
wmi 19193 2 mxm_wmi,asus_wmi
lp 17759 0
parport 42348 3 lp,ppdev,parport_pc
psmouse 106561 0
r8169 71694 0
ahci 34062 4
mii 13934 1 r8169
libahci 32424 1 ahci

mario@casa:~$ ifconfig
eth0 Link encap:Ethernet HWaddr f0:79:59:6d:90:94
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:1505 errors:0 dropped:0 overruns:0 frame:0
TX packets:1505 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:138770 (138.7 KB) TX bytes:138770 (138.7 KB)

wlan1 Link encap:Ethernet HWaddr c4:6e:1f:11:36:91
inet addr:192.168.1.103 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::c66e:1fff:fe11:3691/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:23516 errors:0 dropped:0 overruns:0 frame:0
TX packets:20726 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26692430 (26.6 MB) TX bytes:4203011 (4.2 MB)

mario@casa:~$ ifconfig
eth0 Link encap:Ethernet HWaddr f0:79:59:6d:90:94
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:1505 errors:0 dropped:0 overruns:0 frame:0
TX packets:1505 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:138770 (138.7 KB) TX bytes:138770 (138.7 KB)

wlan1 Link encap:Ethernet HWaddr c4:6e:1f:11:36:91
inet addr:192.168.1.103 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::c66e:1fff:fe11:3691/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:23516 errors:0 dropped:0 overruns:0 frame:0
TX packets:20726 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26692430 (26.6 MB) TX bytes:4203011 (4.2 MB)

¿Qué puedo hacer? No tengo problemas en cambiar de tarjeta wifi si me recomendais una que funcione sin problemas.

Gracias

Mario

EDITO CON INFORMACIóN ADICIONAL

mario@casa:~$ lsmod | grep ath9
ath9k_htc 75131 0
ath9k_common 25638 1 ath9k_htc
ath9k_hw 446521 2 ath9k_common,ath9k_htc
ath 29006 3 ath9k_common,ath9k_htc,ath9k_hw
mac80211 652718 1 ath9k_htc
cfg80211 494330 4 ath,ath9k_common,mac80211,ath9k_htc
mario@casa:~$ iwlist wlan1 scan
wlan1 Scan completed :
Cell 01 - Address: 30:B5:C2:62:FA:38
Channel:6
Frequency:2.437 GHz (Channel 6)
Quality=53/70 Signal level=-57 dBm
Encryption key:on
ESSID:"kill_intruders"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
24 Mb/s; 36 Mb/s; 54 Mb/s
Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s
Mode:Master
Extra:tsf=000000096672fdb3
Extra: Last beacon: 7405644ms ago
IE: Unknown: 000E6B696C6C5F696E74727564657273
IE: Unknown: 010882848B962430486C
IE: Unknown: 030106
IE: Unknown: 0706455320010D14
IE: Unknown: 200100
IE: Unknown: 23020E00
IE: Unknown: 2A0100
IE: Unknown: 2F0100
IE: IEEE 802.11i/WPA2 Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : CCMP TKIP
Authentication Suites (1) : PSK
IE: Unknown: 32040C121860
IE: Unknown: 0B0501008D0000
IE: Unknown: 2D1A7E1817FFFF000001000000000000000000000000000000000000
IE: Unknown: 3D16060F1600000000000000000000000000000000000000
IE: Unknown: 4A0E14000A002C01C800140005001900
IE: Unknown: 7F03010008
IE: Unknown: DD840050F204104A0001101044000102103B00010310470010D96C7EFC2F8938F1EFBD6E5148BFA8121021000754502D4C494E4B1023000854442D573839373010240003332E301042000C3330423543323632464133381054000800060050F20400011011000A54502D4C494E4B5F4150100800022008103C0001011049000600372A000120
IE: Unknown: DD090010180201000C0000
IE: WPA Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : CCMP TKIP
Authentication Suites (1) : PSK
IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00

mario@casa:~$ iw list
Wiphy phy0
Band 1:
Capabilities: 0x116e
HT20/HT40
SM Power Save disabled
RX HT20 SGI
RX HT40 SGI
RX STBC 1-stream
Max AMSDU length: 3839 bytes
DSSS/CCK HT40
Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
Minimum RX AMPDU time spacing: 8 usec (0x06)
HT TX/RX MCS rate indexes supported: 0-7
Frequencies:
* 2412 MHz [1] (20.0 dBm)
* 2417 MHz [2] (20.0 dBm)
* 2422 MHz [3] (20.0 dBm)
* 2427 MHz [4] (20.0 dBm)
* 2432 MHz [5] (20.0 dBm)
* 2437 MHz [6] (20.0 dBm)
* 2442 MHz [7] (20.0 dBm)
* 2447 MHz [8] (20.0 dBm)
* 2452 MHz [9] (20.0 dBm)
* 2457 MHz [10] (20.0 dBm)
* 2462 MHz [11] (20.0 dBm)
* 2467 MHz [12] (20.0 dBm)
* 2472 MHz [13] (20.0 dBm)
* 2484 MHz [14] (disabled)
Bitrates (non-HT):
* 1.0 Mbps
* 2.0 Mbps (short preamble supported)
* 5.5 Mbps (short preamble supported)
* 11.0 Mbps (short preamble supported)
* 6.0 Mbps
* 9.0 Mbps
* 12.0 Mbps
* 18.0 Mbps
* 24.0 Mbps
* 36.0 Mbps
* 48.0 Mbps
* 54.0 Mbps
max # scan SSIDs: 4
max scan IEs length: 2257 bytes
Coverage class: 0 (up to 0m)
Supported Ciphers:
* WEP40 (00-0f-ac:1)
* WEP104 (00-0f-ac:5)
* TKIP (00-0f-ac:2)
* CCMP (00-0f-ac:4)
* CMAC (00-0f-ac:6)
Available Antennas: TX 0x1 RX 0x1
Configured Antennas: TX 0x1 RX 0x1
Supported interface modes:
* IBSS
* managed
* AP
* AP/VLAN
* monitor
* mesh point
* P2P-client
* P2P-GO
software interface modes (can always be added):
* AP/VLAN
* monitor
valid interface combinations:
* #{ managed, P2P-client } <= 2, #{ AP, mesh point, P2P-GO } <= 2,
total <= 2, #channels <= 1
Supported commands:
* new_interface
* set_interface
* new_key
* new_beacon
* new_station
* new_mpath
* set_mesh_params
* set_bss
* authenticate
* associate
* deauthenticate
* disassociate
* join_ibss
* join_mesh
* remain_on_channel
* set_tx_bitrate_mask
* action
* frame_wait_cancel
* set_wiphy_netns
* set_channel
* set_wds_peer
* Unknown command (84)
* Unknown command (87)
* Unknown command (85)
* Unknown command (89)
* Unknown command (92)
* connect
* disconnect
Supported TX frame types:
* IBSS: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* managed: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* AP: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* AP/VLAN: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* mesh point: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* P2P-client: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* P2P-GO: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
* Unknown mode (10): 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
Supported RX frame types:
* IBSS: 0x40 0xb0 0xc0 0xd0
* managed: 0x40 0xd0
* AP: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0
* AP/VLAN: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0
* mesh point: 0xb0 0xc0 0xd0
* P2P-client: 0x40 0xd0
* P2P-GO: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0
* Unknown mode (10): 0x40 0xd0
Device supports RSN-IBSS.
HT Capability overrides:
* MCS: ff ff ff ff ff ff ff ff ff ff
* maximum A-MSDU length
* supported channel width
* short GI for 40 MHz
* max A-MPDU length exponent
* min MPDU start spacing
Device supports TX status socket option.
Device supports HT-IBSS.

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