Internal somehow more sensitive than External Wifi adapter

[valterra]

I have an external "400mw" USB wifi dongle. I got it because I didn't think my laptop's internal card worked with BT4. A little experimentation with kismet.conf and airmon-ng quickly set me straight. However, it seems the internal card is way more sensitive than the one with the detachable 5 db antenna.

By the way, the dongle is at:

hxxp://w w w.data-alliance.net/-strse-117/RealTek-USB-400mW-WiFi/Detail.bok

and I've seen it at various other places, along with eBay. It seems to be a common generic card available at "cheaper" computer stores.

Internal Card: Atheros AR5007 b/g adapter (as reported in Windows)
External Card: Realtek 8187B (RTL8187B) USB dongle.

I wrote a thread earlier about Kismet and Wireshark together only seeming to see Broadcast traffic from my router. This post seeks to expand and clarify that.

I got Kismet to use the internal card (ath0 / wifi0) by editing the sources section of kismet.conf. It found nearly twice the number of access points that the external card did. And I successfully was able to place it in Monitor mode and use it with wireshark on my own network (which is unencrypted).

I typed in iwconfig and noticed something interesting. Or not? Many of the levels on my external card equal zero. Is there a sensitivity setting or something that I am missing? Or is this an issue of airmon-ng simply not passing on some of the information?

For the record: BT4 beta, USB boot persistent, built-in drivers for the RTL8187.

I'd be happy to help myself find the answer or help you all by providing whatever information necessary. Thanks!

Here is the console output:

root@bt:~# airmon-ng


Interface       Chipset         Driver

wifi0           Atheros         madwifi-ng
wlan0           RTL8187         rtl8187 - [phy0]
ath0            Atheros         madwifi-ng VAP (parent: wifi0)
mon0            RTL8187         rtl8187 - [phy0]

root@bt:~# iwconfig
lo        no wireless extensions.

eth0      no wireless extensions.

wifi0     no wireless extensions.

wmaster0  no wireless extensions.

wlan0     IEEE 802.11bg  Mode:Monitor  Frequency:2.437 GHz  Tx-Power=27 dBm
          Retry min limit:7   RTS thr:off   Fragment thr=2352 B
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

ath0      IEEE 802.11g  ESSID:""  Nickname:""
          Mode:Monitor  Frequency:2.437 GHz  Access Point: 00:24:2B:4A:45:99
          Bit Rate:0 kb/s   Tx-Power:16 dBm   Sensitivity=1/1
          Retry:off   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=0/70  Signal level=-96 dBm  Noise level=-96 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

mon0      IEEE 802.11bg  Mode:Monitor  Frequency:2.437 GHz  Tx-Power=27 dBm
          Retry min limit:7   RTS thr:off   Fragment thr=2352 B
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

[kidFromBigD]

Hmmm. I may have something meaningful to offer here...

My experience has proven similar. What I discovered is that my laptop has 2 antennas located on the bezel of the display. The bezel is that part surrounding the flat panel display. They knew what they were doing: The antennas are arranged such that they provide maximum sensitivity along with polarity diversity. That means basically anything one antenna cannot grab the other will likely pick up. The inputs are combined and the resulting feed to the internal card is a bonanza of activity. Like you, I can observe nearly double what a USB dongle reports.

[valterra]

What weirded me out was all the zeros. I can see how a dual antenna system on a laptop would be better.
The advantage of a USB dongle then would be its ability to be mounted high on a wall via an extension cable.