Access Point Signal Strength Monitor

Is there anyone knows how to check the signal strength of an access
point ?
I'm building some directional antennas and I would like to test the
signal from home, instead of from the graphic tools generally available
for the wi-fi cards.
A directional antenna can change a lot of its capabilities by just
optimizing some components and I would like to "see" the effects of
these changes immediately in the same way as on the wi-fi cards.
I have a D-Link DWL2100AP and a D-LINK dfe530TX newtork card.
Do you know about some software able to do that ?

Thanks,
Cale.

On 10 Nov 2005 05:07:03 -0800, "CALE" <(E-Mail Removed)> wrote:

>Is there anyone knows how to check the signal strength of an access
>point ?
>I'm building some directional antennas and I would like to test the
>signal from home, instead of from the graphic tools generally available
>for the wi-fi cards.

Netstumbler will report the signal strength and S/N ratio of both ends
of the test link. The DWL-2100AP supports SNMP. You'll find the
signal strengths somewhere in the MIB tree. If you're going to use
such reporting tools, be sure to change the data rate from auto to
some fixed speed as the signal strength will vary with the wireless
data rate.

Also see: bjs555monitor.vbs
http://groups.google.com/group/alt.i...98f887dee9026c

This probably won't work with your DFE530TX, but is interesting:
http://www.allaboutjake.com/network/...lanexpert.html

>A directional antenna can change a lot of its capabilities by just
>optimizing some components and I would like to "see" the effects of
>these changes immediately in the same way as on the wi-fi cards.

Are you looking to characterize the antenna (pattern, vswr, etc) or do
you just want some clue as to the gain increase? If the latter, just
setup a reference antenna with a known gain and compare results with
your home made antenna.

>I have a D-Link DWL2100AP and a D-LINK dfe530TX newtork card.
>Do you know about some software able to do that ?

--
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

On Thu, 10 Nov 2005 09:52:02 -0800, Jeff Liebermann
<(E-Mail Removed)> wrote:

>Netstumbler will report the signal strength and S/N ratio of both ends
>of the test link. The DWL-2100AP supports SNMP. You'll find the
>signal strengths somewhere in the MIB tree. If you're going to use
>such reporting tools, be sure to change the data rate from auto to
>some fixed speed as the signal strength will vary with the wireless
>data rate.

Jeff,

That's a really good point about making the data rate a fixed speed.
Suddenly my measurements make more sense

Thanks,
Bruce

On Fri, 11 Nov 2005 08:24:46 -0500, bjs555 <(E-Mail Removed)> wrote:

>On Thu, 10 Nov 2005 09:52:02 -0800, Jeff Liebermann
><(E-Mail Removed)> wrote:
>
>>Netstumbler will report the signal strength and S/N ratio of both ends
>>of the test link. The DWL-2100AP supports SNMP. You'll find the
>>signal strengths somewhere in the MIB tree. If you're going to use
>>such reporting tools, be sure to change the data rate from auto to
>>some fixed speed as the signal strength will vary with the wireless
>>data rate.

>That's a really good point about making the data rate a fixed speed.
>Suddenly my measurements make more sense
>Thanks,
>Bruce

Yep. I was getting an awful lot of "circular" antenna patterns until
I discovered the obvious. However, you're not done yet. I noticed
that fixing the connection speed doesn't necessary disable some of the
other speed mutilating features. I testing a Dlink DI-624 and found
that if I set the speed to 12Mbits/sec OFDM, I should expect that
802.11b compatibility would also be disabled, since it should never
connect at 802.11b speeds. Nope. It continues to listen for 802.11b
clients that will never be able to connect. I also found that leaving
the super-G, turbo, or whatever modes enabled left it also sniffing
for those, which will never connect. Therefore, turn OFF all advanced
features before trusting the signal strength readings.

As for accuracy, the wireless cards all generate an RSSI (receive
signal strength indicator) reading on a scale of 0 to 254. This is
converted in either the firmware (for SNMP) or in software to -dBm
signal levels. The granularity of the -dBm output largely depends on
how much effort the programmists put into the conversion. In most
cases, it's just a lookup table with no interpolation. They may offer
good resolution for weak signals, where you need it, and use big jumps
at high signals, where nobody really cares. Some manufacturers
calibrate each table individually while others just use a best guess.
There are at least 5 other ways to generate the numbers including "bit
distance" calcs.
http://archives.neohapsis.com/archiv...1-q4/0305.html
http://archives.neohapsis.com/archiv...1-q4/0295.html
--
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

CALE <(E-Mail Removed)> wrote:
> Is there anyone knows how to check the signal strength of an access
> point ?
> I'm building some directional antennas and I would like to test the
> signal from home, instead of from the graphic tools generally available
> for the wi-fi cards.

When testing for proper aiming, I put my laptop "over there", and started
WinVNCServer on it. Then I came back to the desktop, started
WinnVNCViewer, and used that to view the laptop screen, where the client
monitor tool was running. I could adjust the antenna, and see the results.
The traffic of the VNC session itself seemed to make good data for the
client monitoring tool. The card that I had at that time didn't run
NetStumbler.

http://www.RealVNC.com

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5