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I'm having a problem with disconnections with my Alfa. I face the same problem on Linux Mint 15. On Windows though everything works perfect.

$ iwconfig 
wlan2     IEEE 802.11bg  ESSID:"OTE5D8A0C"  
          Mode:Managed  Frequency:2.437 GHz  Access Point: 20:F3:A3:5D:8A:14   
          Bit Rate=54 Mb/s   Tx-Power=27 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=61/70  Signal level=-49 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:1   Missed beacon:0

wlan1     IEEE 802.11bgn  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=27 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off

eth0      no wireless extensions.

lo        no wireless extensions.


$ nm-tool

NetworkManager Tool

State: connected (global)

- Device: wlan2  [OTE5D8A0C] ---------------------------------------------------
  Type:              802.11 WiFi
  Driver:            rtl8187
  State:             connected
  Default:           yes
  HW Address:        00:C0:CA:51:2B:9B

  Capabilities:
    Speed:           54 Mb/s

  Wireless Properties
    WEP Encryption:  yes
    WPA Encryption:  yes
    WPA2 Encryption: yes

  Wireless Access Points (* = current AP)
    Green n Blue:    Infra, AC:86:74:0D:6C:22, Freq 2432 MHz, Rate 54 Mb/s, Strength 45 WPA WPA2
    govas:           Infra, 00:16:B6:E4:04:8C, Freq 2437 MHz, Rate 54 Mb/s, Strength 45 WEP
    *OTE5D8A0C:      Infra, 20:F3:A3:5D:8A:14, Freq 2437 MHz, Rate 54 Mb/s, Strength 71 WPA
    conn-x91da80:    Infra, CC:1A:FA:91:DA:80, Freq 2412 MHz, Rate 54 Mb/s, Strength 54 WPA
    OTEB35984:       Infra, 00:26:44:B3:59:84, Freq 2452 MHz, Rate 54 Mb/s, Strength 44 WPA WPA2

  IPv4 Settings:
    Address:         192.168.1.2
    Prefix:          24 (255.255.255.0)
    Gateway:         192.168.1.1

    DNS:             192.168.1.1


- Device: wlan1 ----------------------------------------------------------------
  Type:              802.11 WiFi
  Driver:            ath9k_htc
  State:             disconnected
  Default:           no
  HW Address:        00:26:F2:52:D9:E0

  Capabilities:

  Wireless Properties
    WEP Encryption:  yes
    WPA Encryption:  yes
    WPA2 Encryption: yes

  Wireless Access Points 


- Device: eth0 -----------------------------------------------------------------
  Type:              Wired
  Driver:            r8169
  State:             unavailable
  Default:           no
  HW Address:        94:DE:80:2B:FE:78

  Capabilities:
    Carrier Detect:  yes

  Wired Properties
    Carrier:         off


$ sudo lshw -C Network  *-network               
       description: Ethernet interface
       product: RTL8111/8168 PCI Express Gigabit Ethernet controller
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: eth0
       version: 06
       serial: 94:de:80:2b:fe:78
       size: 10Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl8168e-3_0.0.4 03/27/12 latency=0 link=no multicast=yes port=MII speed=10Mbit/s
       resources: irq:74 ioport:d000(size=256) memory:dc104000-dc104fff memory:dc100000-dc103fff
  *-network:0
       description: Wireless interface
       physical id: 1
       bus info: usb@8:1.4
       logical name: wlan2
       serial: 00:c0:ca:51:2b:9b
       capabilities: ethernet physical wireless
       configuration: broadcast=yes driver=rtl8187 driverversion=3.8.0-19-generic firmware=N/A ip=192.168.1.2 link=yes multicast=yes wireless=IEEE 802.11bg
  *-network:1
       description: Wireless interface
       physical id: 2
       bus info: usb@2:5.2
       logical name: wlan1
       serial: 00:26:f2:52:d9:e0
       capabilities: ethernet physical wireless
       configuration: broadcast=yes driver=ath9k_htc driverversion=3.8.0-19-generic firmware=1.3 link=no multicast=yes wireless=IEEE 802.11bgn

Here is an output from iwscanner. At the end as you can it disconnected. enter image description here

What i have tried so far: 1 - I disabled the IPv6 for my alfa. I read in another question that this may cause some conflicts.

2 -

$ sudo modprobe -rfv rtl8187
rmmod rtl8187
rmmod eeprom_93cx6

$ sudo modprobe -v rtl8187
insmod /lib/modules/3.8.0-19-generic/kernel/drivers/net/wireless/rtl818x/rtl8187/rtl8187.ko

So far the nothing worked.

UPDATE

So far the problem persists.

NOTE - I think i have found a pattern. The adapter rarely disconnects when i am just browsing. But when i am downloading somthing especially if it is big (ex bigger than 100M) it is more likely that it will disconnect. Also, but this may be just in my mind, i think it disconnects after the download speed hits it's peak.

Additionally i have noticed that after it disconnects, in the netwotk indicator the adapter is up and it lists all the available networks except mine (the one it just disconnected from).

What is going on?

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