# Thread: [BT4] Possible conflict between drivers?

1. ## [BT4] Possible conflict between drivers?

Hello, I will explain my situation.

I recently bought a new notebook (Dell Latitude D400), and installed BT4 on it dual boot with XP.

The laptop already has an internal WIFI card. I am using a Netgear PCMCIA card wich worked out of the box before with BT3 on another laptop.

When I start airodump-ng, the power levels are all in negative (- in front). My own AP is show as -34. As I understand it, it's a driver issue. But why would there be any driver issues because the card worked fine with BT3 on another laptop...

So is it possible that there's a conflict between the internal WIFI card and the PCMCIA card? Because my old laptop did not have any internal WIFI cards..

2. It's normal to show negative units
Just remember that the greatest is the closest ( -40 is greater than -80)

3. Depending on your driver, the power might be expressed in milliwatts or in dBm.

With milliwatts, you're always gonna get a positive number (e.g. 34 milliwatts).

However with dBm's, it's possible to get a negative number. Here's how dBm's convert to milliwatts:

milliwatts = 10 ^ (dBm / 10)

Look at the above equation and think about what happens if you substitute a negative number in for "dBm". For instance, if "dBm" is -30 then it will work out as follows:

milliwatts = 10 ^ (-30 / 10)
milliwatts = 10 ^ (-3)
milliwatts = 0.001

So -30 dBm is equal to 0.001 milliwatts (or 1 microwatt).

Even if you have a negative figure for dBm's, it will always become positive when you convert it to milliwatts.

When you see a negative number for dBm's, it simply means that the power is less than 1 milliwatt, reason being that 1 milliwatt is equal to 0 dBm.

4. Originally Posted by Virchanza
Depending on your driver, the power might be expressed in milliwatts or in dBm.

With milliwatts, you're always gonna get a positive number (e.g. 34 milliwatts).

However with dBm's, it's possible to get a negative number. Here's how dBm's convert to milliwatts:

milliwatts = 10 ^ (dBm / 10)

Look at the above equation and think about what happens if you substitute a negative number in for "dBm". For instance, if "dBm" is -30 then it will work out as follows:

milliwatts = 10 ^ (-30 / 10)
milliwatts = 10 ^ (-3)
milliwatts = 0.001

So -30 dBm is equal to 0.001 milliwatts (or 1 microwatt).

Even if you have a negative figure for dBm's, it will always become positive when you convert it to milliwatts.

When you see a negative number for dBm's, it simply means that the power is less than 1 milliwatt, reason being that 1 milliwatt is equal to 0 dBm.
But why is it suddenly negative? Also, when I want to associate with my WIFI (in XP), the signal strength from my AP is low. And all the other AP's are like 0 power..

EDIT:

I have just tested the same card, on the same laptop but with BT3! And now the power levels seem to be normal (no negatives). So it's definitely a OS/driver issue. I must change the drivers in BT4.. can anyone point me in the right direction to do that? Where I can start etc.?

5. same problem here

after i haveinstalled BT4 Final to my laptop i have also negative PWR figures
in BT3 i never had negative figures before.

i think in bt4 there is another driver used, because in BT3 my monitor mode interface was called wlan0 and in BT4 Final mon0 (google says that depends on the driver either mac80211 or ieee802111)

how can i fix the negative PWR

or

how to change the driver to another one

i got an ALFA AWUS036E

greetz

6. PROBLEM SOLVED

i searched through the aircrack-ng.org doku and found a solution

it depends on the drivers with the negative PWR

you have to blacklist the mac802111 driver so that the other one will be used

Edit /etc/modprobe.d/blacklist and add “blacklist rtl8187” as a new line
Be careful that the other driver is not blacklisted like it was in my BT4 Final then you have no wireless^^

aircrack-ng.org/doku.php?id=r8187

Found here under Point Troubleshooting -> blacklisting driver

greetz

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