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With the introduction of new drivers Stacks mac80211, unlike previous ieee80211, the TX-Power is adjusted/set automatically by CRDA.

Therefore is not longer possible to use the ALFA-AWUS036H USB wireless adapter (chipset Realtek RTL8187L) with all his power for Wireless connections or during Wardriving.

By analyzing the structure of new configuration of mac80211 files and "udev" recall to the Linux Kernel, we can circumvent the obstacle by adjusting the strength of TX-Power of our Wireless card acting on the CRDA. (Central Regulatory Domain Agent)

Remember, that modification of CRDA, not only affects the settings of the maximum usable/permit power (dBm), but also setup the channels of frequencies/band allocated for the Wireless trasmission, which are set globally and for each Country by specific Laws Regulations, so make sure not to violate the Laws of your Country using frequencies or tx-powers not allowed.

After this brief introducion, we see how to permit the full output power of your wireless card, opting for either of these two solutions.

- The creation and editing of the following files must be done carefully.

­ - Tested on Ubuntu Jaunty - Kernel 2.6.28 and 2.6.30.

­- Tested on BackTrack 4 and 5.

- Compatible with latest Ubuntu version only after making some changes to the procedures described below.

- Make sure not to violate the Laws of your Country using frequencies or power (Tx Powers) not permitted.

Update your OS and install these ESSENTIAL and recommended package

NOTE: Before continuing, make sure NOT to be active in Synaptic the Repositories "Proposed" and "Backports"

Install/update "IW"
(Wireless Configuration Utility for drivers based on Stacks-mac80211)

[Firt option] Install iw from Ubuntu Repository

[RECOMMENDED OPTION] Alternatively compiling the latest version available from IW source

FIRST OPTION

If you use more than one Wireless adapter is convenient to change automatically the CRDA when you need and only for your ALFA-AWUS036H usb card.
Therefore, this first option is recommended to simplify but not permanently change the default data of your System.

Create a new file using your favorite text editor, called "crda_change" "

Copy & paste in the new file created this text

Make file executable

Make a copy of Backup of the original file and create a new alias, in the example named --> boost

Now close your shell session, and if you want load the driver RTL8187/mac80211 and change automatically the CRDA use boost command in new terminal

Second Option

­ Create a new file called "crda_change" as described in the previous step ­­--> FIRST OPTION

Create, or if it already exists, edit the following file

Copy and paste the following text

Now, when connecting the usb WiFi adapter into the USB port, the script will run automatically to allow the adjustment of the TX-Power of your usb card connected.

Basic Linux commands to check the CRDA and set the output power (tx power) using IW

To check the current level of output power settings (tx power level)

The use of IW to check the Regulatory Domain settings currently in use by your Kernel

The use of IW to verify the frequencies and output powers allowed by change the regulatory domain settingsthe current CRDA

The use of IW to setting the output power level to 1.000mW/3000mBm (txpower output)

If you use the new configuration utility for Wireless device "IW" instead of "IWCONFIG", remember that the parameters for setting the output power level be expressed in mBm (millibels referenced to 1 milliwatt) and lo longer in dBm (decibels referenced to 1 milliwatt), therefore the scale is as follows: -> 100 mBm = 1 dBm.

Test on Ubuntu

        

Test on BackTrack 5