Thanks Mike. I'm a little confused. The parameters are listed as follows: sample-rate: channel-bandwidth: freq_step: fft_size:
You mean that I should set sample-rate be 25e6, channel-bandwidth be 8e6, freq_step be 8e6 and fft_size be 25? If we set the fft-size be 25, then which 8 bins I should select to calculate the power? By the way, since the magnitude of FFT bin is decimal, maybe I should change the magnitude of FFT bin values to mw and add the 8 bins, and then transfer to decimal again? Since we cannot straightly add the FFT bin values in decimal. By the way, how about the "self.connect", should I add the log parameter to it? Thanks. Hope for your reply. On Mon, Apr 8, 2013 at 12:11 AM, Mike Jameson <m...@scanoo.com> wrote: > Hi Jincheng, > > Try setting the UHD sample rate to 25e6 and the number of fft bins to 25 > which will give you 1e6 Hz per bin. Adding up the magnitude of 8 bins > (1MHz * 8 = 8MHz) will therefore give you the wanted channel power in > decimal format (magnitude). > > In case you are confused, I recently updated usrp_spectrum_sense.py to > include a --channel-bandwidth setting which rounds up the frequency > displayed to the nearest frequency. I'm working on making it cleaner by > adjusting the fft size to match the wanted channel. In the meantime, set > '--channel-bandwidth=8e6' to make the frequency round to the nearest 8MHz > frequency. > > Hope that helps, > > Mike > > -- > Mike Jameson M0MIK BSc > Email: m...@scanoo.com > Web: http://scanoo.com > > > On 7 April 2013 16:23, Jincheng Zhang <perfume0...@gmail.com> wrote: > >> I want to use usrp_spectrum_sense.py to sweep the Hong Kong TV band which >> ranges from 470MHz to 806MHz and get every channel's power in dB. Each >> channel's frequency band is 8MHz. >> >> Now I'm using USRP2 with TVRX2 daughter board. I have installed the >> latest gnuraio and uhd. But when I use the usrp_spectrum_sense.py to get >> the power of each channel, some FFT bin values are extremely big. In >> particular, I'm not sure abou the self.connect(self.u, s2v, fft, c2mag, >> stats). It doesn't take "log" as the parameter, >> >> FFT size is 2048, sample-rate is 12.5MHz(to let the decimation be 8M), >> freq_step is 8MHz. Anyone has any ideas about how to use >> usrp_spectrum_sense.py to calculate each channel's power? >> >> >> On Sun, Apr 7, 2013 at 8:24 PM, Jincheng Zhang <perfume0...@gmail.com>wrote: >> >>> Hi, all, >>> >>> I use the usrp_spectrum_sense.py to sweep the TV band from 470MHz to >>> 806MHz. But when I use self.connect(self.u, s2v, fft, c2mag, log, stats), >>> the FFT bin values I got are all zero. >>> Also, what's the magnitude of FFT bin value? Thanks. >>> >>> -- >>> Best regards, >>> Jincheng Zhang >>> >> >> >> >> -- >> Best regards, >> Jincheng Zhang >> Department of Information Engineering >> The Chinese University of Hong Kong >> http://personal.ie.cuhk.edu.hk/~zj012/ <http://www.jxqc.org/> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > -- Best regards, Jincheng Zhang Department of Information Engineering The Chinese University of Hong Kong http://personal.ie.cuhk.edu.hk/~zj012/ <http://www.jxqc.org/>
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