Wifi transmitter locator

Hi,

I have a curious problem. At home in Bangalore (India) my laptop
informs me about a wifi source. I do not know where it comes from.

Is there any way I can find out more about the source and/or company
that is transmitting it?

Thanks,
Arvind

On 23 Dec 2005 22:46:58 -0800, (E-Mail Removed) wrote:

>I have a curious problem. At home in Bangalore (India) my laptop
>informs me about a wifi source. I do not know where it comes from.
>
>Is there any way I can find out more about the source and/or company
>that is transmitting it?

You can usually get a clue from the SSID (name) of the wireless
"source". However, if it's non-descript, the only other alternative
is to do some direction finding. This is not easy, takes some
practice, but works fairly well.

The basic trick is to have:

1. Wi-Fi card with an external antenna and that is fairly well
shielded. I use a PCMCIA card with aluminum foil wrapped around the
PCMCIA antenna.
2. External directional antenna. I use a 19dBi dish antenna. This
has a -3dB beamwidth of about 15 degrees which is good enough for
direction finding. Other antennas will work but make sure they have a
narrow beamwidth.
3. Software that will display signal strength. This can be part of
the driver that came with the wireless card, stand alone application,
or Netstumbler.

There are many tricks to doing direction finding. Just fumbling
around looking for the strongest signal is a guaranteed failure. You
will be fooled by reflections and obstructions. What I do is use a
map. I locate myself and take a bearing. With the bearing, I draw a
line on the map from my location. I then move to another location and
draw another line. Do this often enough, over a long baseline, and
the majority of the lines will cross one point on the map. There will
be some lines going off in random directions. Just ignore those. This
works especially well while moving in a vehicle.

There is also software that will do this automatically.
http://gpss.tripoduk.com/df1.htm
I haven't tried this one.

Good luck.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks. This is way beyond what I can do!! But it helps to know

On 25 Dec 2005 23:08:02 -0800, "R. Arvind" <(E-Mail Removed)>
wrote:

>Thanks. This is way beyond what I can do!! But it helps to know

Well, then let me suggest a way that you can do it with just your
laptop.

1. Figure out where the antennas are located on your laptop. If you
have two antennas inside your laptop, open the cover to the the
wireless MiniPCI card and disconnect *ONE* of the antennas. The
antenna will probably be somewhere in the LCD part of the laptop, on
the right or left side, near the top. There are often photos on the
laptop manufacturers web site showing the antenna location. If you
have a fancy microwave oven leakage detector, you can sometime locate
the antenna by starting a big file transfer and looking for a signal.
It will be VERY weak, but the oven leakage detector should find it.

2. When you have located the antenna, put a big sheet of aluminum
foil over the antenna on the side facing the display. Hold it in
place with Scotch tape. Wrap the foil around the edge. You can add
additional aluminum foil on the back of the laptop if necessary, but
don't cover the antenna area. The idea is to leave a narrow slit,
approximately the width of the antenna (1/4") on the back of the
laptop, directly over the antenna. This will make the antenna very
directional.

3. You will need to do a boresight alignment. There is no guarantee
that the antenna is pointed exactly perpendicular to the laptop case.
Find a nearby access point and use the signal strength indicator to
determine the direction of maximum signal. That's where the antenna
is pointed.

4. The rest was explained in my previous posting. Use a map. Draw
lines in the direction the antenna points. Move around. Where most
of the lines cross, is the transmitter. Since your laptop can "see"
the mystery access point, Netstumbler should work for signal strength
and identification.



--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558