# Capture and plot 802.11 frames

**URL:** <https://www.ruby-forum.com/t/capture-and-plot-802-11-frames/212520>\
**Category:** GNU Radio\
**Created:** [October 5, 2011, 6:31pm UTC](https://www.ruby-forum.com/t/capture-and-plot-802-11-frames/212520 "2011-10-05T18:31:02Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\
**Post date:** [October 5, 2011, 6:31pm UTC](https://www.ruby-forum.com/t/capture-and-plot-802-11-frames/212520/1 "2011-10-05T18:31:02Z")

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Hello,

I am a new user of the GNU platform.

I managed to install the paltform on my Ubuntu 10.4 PC  
and I am currently trying to capture 802.11 frames that are transmitted  
in  
my  
WLAN.

I am using these tools:  
usrp\_oscope.py -f 2.412G  
uhd\_fft.py -f 2.412G

All I can see is noise on this frequency, although I confirm that  
packets  
are transmitted between my PC and my router on this frequency.

Does my problem have to do something with the settings of these tools or  
do  
I miss something else.

Can you provide me with some tutorial link, where I can find more info  
on  
the basic usage of USRP?

Thank you in advance,  
Stratos.

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**Author:** ![Stratos\_Keranidis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/91b2a8/32.png) [@Stratos\_Keranidis](https://www.ruby-forum.com/u/Stratos_Keranidis)\
**Post date:** [October 5, 2011, 6:34pm UTC](https://www.ruby-forum.com/t/capture-and-plot-802-11-frames/212520/2 "2011-10-05T18:34:44Z")

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On 05/10/2011 12:30 PM, Stratos Keranidis wrote:

> usrp\_oscope.py -f 2.412G
> 
> Thank you in advance,  
> Stratos.

You don’t say what your hardware setup is. Do you have an antenna  
plugged in? Is it on the correct port? Have you tried setting  
the gain upwards in uhd\_fft.py?

What version of Gnu Radio are you running? What version of UHD?

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**Author:** ![Stratos\_Keranidis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/91b2a8/32.png) [@Stratos\_Keranidis](https://www.ruby-forum.com/u/Stratos_Keranidis)\
**Post date:** [October 5, 2011, 6:55pm UTC](https://www.ruby-forum.com/t/capture-and-plot-802-11-frames/212520/3 "2011-10-05T18:55:41Z")

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Hi Marcus,

first I want to thank you for your very fast reply.  
I am sorry for not reporting details about my system setup.

I am using a USRP1 model and I have one XCVR2450 daughterboard attached.  
Two antennas are connected at the pigtails on the daughterboard.  
I usedthebuild-gnuradio install script to for installation and so I  
downloaded the latest versions from the ‘main’ branch for both UHD and  
GNU Radio.

I just set the gain at the maximum level and I notice that signals can  
be received at the level of -35dBm.

Can I use the usrp\_oscope.py to capture plots of the transmitted frames.  
My main aim is to able to plot the exact duration of a transmitted  
frame, ack packets etc.

I hope the information I provided can help you.

Thank you,  
Stratos.