Hi Soumaya, could you please keep the mailing list in the loop?
Well, on USB2, the maximum sampling rate is, if I remember correctly, somewhere between 8 MS/s and 10 MS/s. Maybe the raspberry Pi isn't the optimal platform for broadband signal observation... $((2**16)) gets evaluated by your shell to the value of 2¹⁶ . Best regards, Marcus On 01/16/2017 12:48 PM, Soumaya el barrak wrote: > Dear Marcus, > > > Thank you again for your explanations, but I installed Gnuradio on a > Raspberry pi 3, model B board, so the usb ports are USB2 not 3. That’s > why I cannot use a high sample rate. I got an error because of the USB > bandwidth limitations. If you can guide me to the right parameters to > choose with this kind of host machine? > > Also, Can you please explain for me what does this parameter refer to > : $((2**16)) > > > The script which I use is this one: > > https://github.com/gnuradio/gnuradio/blob/master/gruhd/examples/python/usrp_spectrum_sense.py. > > > > Thank you in advance > > Kind Regards > > Soumaya > > > 2017-01-16 12:28 GMT+01:00 Marcus Müller <marcus.muel...@ettus.com > <mailto:marcus.muel...@ettus.com>>: > > Hi Soumaya, > > while tuning, there will simply be transients, mostly of > oscillator energy leaking into the receiver. You cannot use the > data that you get while tuning. > > You might want to define "strange power values"; 2.4 GHz is an ISM > band, so a lot of traffic is to be expected there, and that > traffic is also probably very bursty, so that your observed values > might temporarily vary a lot, since your observation time is much > longer than the bursts in e.g. WiFi, your observed power is > basically the product of number of burst, burst energy of the > individual transmitter, and path loss between your receiver and > the transmitter. > > Still, why are you using such small sampling rates as 8 MS/s? With > a good USB3 controller and a reasonably fast computer, you should > easily be able to do 40 MS/s with the usrp_spectrum_sense program. > In fact, on my throttled thinkpad X240, I'm currently doing > > ./usrp_spectrum_sense.py -s 40e6 -g 76 -F $((2**16)) 2.4e9 2.5e9 > > and it works just fine. > > Best regards, > > Marcus > > On 01/16/2017 10:32 AM, Soumaya el barrak wrote: >> >> Hi Marcus, >> >> >> Thank you so much for your reply, I followed your >> recommendations, I used a sample-rate of 8MS/s and FFT-size 1024 >> and I kept the tune-delay and dwell-delay at 0.25 s. But I still >> receive some strange power values while scanning the 2.4 GHz band. >> >> >> I also obtained high power picks while tuning from one center >> frequency to another. Could you please explain for me where I am >> mistaken? And what is the explanation of those power picks? >> >> >> Best.. >> >> Soumaya >> >> >> 2017-01-13 14:46 GMT+01:00 Marcus Müller >> <marcus.muel...@ettus.com <mailto:marcus.muel...@ettus.com>>: >> >> Hi Soumaya, >> >> the B200 tunes slower and might need up to half a second when >> tuning further. >> >> You should hence minimize the amount of tuning, and instead >> of 4MS/s use a higher rate, a larger FFT size, and tune less >> often. >> >> The power normalization is truly, 100%, arbitrary. Since >> these dB are all "relative to digital 1", they only have >> linear relation with real-world powers. >> >> >> Best regards, >> >> Marcus >> >> >> On 01/13/2017 11:40 AM, Soumaya el barrak wrote: >>> Dear all, >>> >>> I am working with USRP B200 for spectrum sensing, I want to >>> scan the band from 2.4 to 2.5 Ghz, I use fft size 256, and >>> sample_rate 4M, and tune _delay 0,001s. I am not sure if the >>> parameters are correctely chosen because when I try to scan >>> another band without wireless activities, I still receive >>> hight power levels. Can anyone has any idea about where I am >>> mistaken ? >>> >>> Also, in the formula used to calculate the PSD : >>> >>> Power_dB = 10*math.log10(m.data[i_bin]/tb.usrp_rate); >>> >>> Normally it is the magnitude squared averaged , I want to >>> know why it is averaged by the usrp_rate ? >>> >>> >>> Thank you in advance ! >>> >>> Soumaya >>> >>> -- >>> >>> *EL BARRAK Soumaya* >>> >>> *Telecommunication & Networking Engineer / Phd Student* >>> >>> *Innovative Technologies Laboratory* >>> >>> *National School of Applied Sciences of Tangier - (ENSA Tanger)* >>> >>> *Abdelmalek Essaâdi University - Morocco* >>> >>> *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 >>> <tel:+39%20327%20198%205064>* >>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> <https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> >> _______________________________________________ >> Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org >> <mailto:Discuss-gnuradio@gnu.org> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> <https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> >> >> -- >> >> *EL BARRAK Soumaya* >> >> *Telecommunication & Networking Engineer / Phd Student* >> >> *Innovative Technologies Laboratory* >> >> *National School of Applied Sciences of Tangier - (ENSA Tanger)* >> >> *Abdelmalek Essaâdi University - Morocco* >> >> *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 >> <tel:+39%20327%20198%205064>* >> > -- > > *EL BARRAK Soumaya* > > *Telecommunication & Networking Engineer / Phd Student* > > *Innovative Technologies Laboratory* > > *National School of Applied Sciences of Tangier - (ENSA Tanger)* > > *Abdelmalek Essaâdi University - Morocco* > > *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064* >
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