Signal sensitivity problem with if_rum

[Gustau Pérez]

  Hi,

  I think this is right place to post, if it is not, please let me know.

   I'm experiencing problems with two different devices using if_rum.
One is a Hercules Guillemot and the other is a Linksys Cisco WUSB54GC

  The first one is about sensitivity, which is very low: for example,
I'm detecting just two or three networks around me (with windows both 
usb devices detect around 14 or 15 networks) and the reported signal is 
very low.Placing the sensor very near to my wireless network AP (which 
is a FreeBSD machine with atheros card placing the txpower to 20) 
reports a signal quality of 50% or 60%.

  Linux presents the same problem (my wife's laptop with ubuntu shows
the same figures, more or

  The other one is that having such a low sensitivity makes those
dongles unusable when making large transfers, mostly when using scp/sftp
or sshfs (samba seems to make it work better for longer transfer, but
finally the problem appears). At some given point, the dongles seem to
lose contact with the AP (making ifconfig shows that wlan0 is still
associated), waiting for a period of time (usually one or two minutes)
the transfer continues. Probably both problems are related.

  In order to debug the problem I tried looking dmesg in both my AP and
my laptop (no trace). Tried looking at the ssh logs (when making large
transfers, no clue). In the only place I found something was in the
samba logs, only saying that there was a problem with the transfer
(broken pipe, the socket is closed).

  So :

  In the linux world, I found that the register which controls the
sensitivity is bbp17 :

http://209.85.229.132/search?q=cache:H8W6R5Ds3mYJ:forum.aircrack-ng.org/index.php%3Ftopic%3D2235.0+bbp17+ralink+linux&cd=1&hl=ca&ct=clnk&gl=es&client=firefox-a

   Tried looking in
/usr/src/sys/dev/usb/wlan/if_rum.c, but I got lost. Tried with sysctl -a
| grep rum or grep wlan0, but no MiB related to sensitivity appeared.

  Is there anything I can try ? How can I force bbp 17 to get 0 value ? 
Tried with rum_def_bbp in if_rum.c, changing 17 to 0. No luck.

  Regards,

  Gus