USB - rt73: Maximum tx power 7 dBm

Live forum: http://rt2x00.serialmonkey.com/viewtopic.php?t=5492

Genar

13-07-2009 22:46:31

I am using a USB Wi-Fi device which has the rt73 chip. It works OK, but the maximum transmission power is 7 dBm. If I execute the command "iwconfig wlan1 txpower 4" then the transmission power is set to 4 dBm, so this is the expected behavior; however, if execute the command "iwconfig wlan1 txpower 20", the transmission power is 7 dbm and this is the maximum transmission power that I can configure. Here you are the execution of "iwconfig wlan1". The configuration of my wlan1 is

wlan1 IEEE 802.11bg ESSID"BBgenar"
ModeAd-Hoc Frequency2.412 GHz Cell 36692A2B14B8
Tx-Power=7 dBm
Retry min limit7 RTS throff Fragment thr=2352 B
Encryption keyoff
Link Quality0 Signal level0 Noise level0
Rx invalid nwid0 Rx invalid crypt0 Rx invalid frag0
Tx excessive retries0 Invalid misc0 Missed beacon0

The kernel I am using is 2.6.26-8, but I am also installed and checked the kernel 2.6.29 and the result is the same; that is the maximum transmission power is 7 dBm.
The loaded modules related to the rt73 chip in the 2.6.26-8 kernel are (command "lsmod | grep rt")

rt2500usb 21825 0
rt73usb 24001 0
crc_itu_t 6081 1 rt73usb
rt2x00usb 11969 2 rt2500usb,rt73usb
rt2x00lib 33089 3 rt2500usb,rt73usb,rt2x00usb
rfkill 11481 1 rt2x00lib
mac80211 175669 3 rt2x00usb,rt2x00lib,ath5k
cfg80211 25417 3 rt2x00lib,ath5k,mac80211

The most surprising is that in a Fedora Core 8; that is, kernel 2.6.23, I can increase the transmission power up to 27 dBm (at least in theory). In Fedora core 8 the result of "iwconfig wlan1" is

wlan1 IEEE 802.11g ESSID"BBgenar"
ModeAd-Hoc Frequency2.412 GHz Cell 02DAE90D4079
Tx-Power=27 dBm
Retry min limit7 RTS throff Fragment thr=2346 B
Encryption keyoff
Link Quality0 Signal level0 Noise level0
Rx invalid nwid0 Rx invalid crypt0 Rx invalid frag0
Tx excessive retries0 Invalid misc0 Missed beacon0

and the result of "lsmod | grep rt" is

rt2500usb 24641 0
rt73usb 26945 0
rt2x00usb 12097 2 rt2500usb,rt73usb
rt2x00lib 19009 3 rt2500usb,rt73usb,rt2x00usb
rfkill 9169 1 rt2x00lib
input_polldev 7369 1 rt2x00lib
crc_itu_t 6081 1 rt2x00lib
mac80211 131409 4 rc80211_simple,rt2x00usb,rt2x00lib,ath5k

Any comment will be appreciated, thanks.

Genar

28-07-2009 20:19:37

Hello,

I have solved the problem installing

http/homepages.tu-darmstadt.de/~p_larbig/wlan/rt73-k2wrlz-3.0.3.tar.bz2

The compilation of this source code will create a rt73.ko module; so it is this module which has to be used (so it will be necessary to put in the blacklist modules like rt73usb.ko, ...).

I am using a Edimax USB WiFi and in order to modify the transmision power you can use the parameter "txPowerTuning" when the module is loaded using modprobe (you can see all the possible parameters executing the command "modinfo rt73", and at the end you will be able to see all the parameters that can be passed to the module.

I compiled successfully this module in both Debian Lenny and Fedora Core 8 updated to the kernel 2.6.26.8-57.fc8.

Take into account that the range (distance) of the Edimax USB WiFi is limited by the inner antenna and the real power supplied by the device, so do not expect very long ranges.

Regards,