Hello again,
I have some more screen shots that might explain better what I am asking. These
screen shots are from the 825 MHz - 850 MHz band, which should include most of
the GSM 850 uplink channels.
http://img293.imageshack.us/img293/7831/screenshotusrpfft3vt5.png
http://img442.imageshack.us/img442/1311/screenshotusrpfft4go9.png
http://img253.imageshack.us/img253/170/screenshotusrpfft6hr1.png
http://img517.imageshack.us/img517/3041/screenshotusrpfft7jm1.png
http://img253.imageshack.us/img253/9977/screenshotusrpfft8bk9.png
I have circled in red the tops of the spikes I think might be spurious. I
didn't check these against a spectrum analyzer like the ones in my original
question, so I don't know for sure they are spurious. They appear similar to
the ones I'm my original message. Also, disconnecting the antenna doesn't
attenuate them much.
Does any one know what these spikes are and if they are normal? Are they a
software or hardware artifact?
Thanks,
Thomas
Hi everyone,
I am using a USRP with only a DBSRX daughterboard installed. The image at
the following link is a screen capture I took.
http://img340.imageshack.us/img340/3570/screenshotusrpfftfy8.jpg
Does anyone know why the spike at 921.6 MHz is there? I have observed many
of these spikes in other parts of the spectrum using usrp_fft.py. I looked for
them using a real spectrum analyzer connected to an antenna and did not observe
them.
I used the same parameters in usrp_fft.py that were used in the first image
at the following link.
http://273k.net/gsm/find-a-gsm-base-station-manually-using-a-usrp/
This spike does not exist in their plot.
I appreciate your responses.
Thanks,
Thomas
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