On 10/17/2012 05:21 AM, Hemant Saggar wrote: > Hi all, > > I am new to USRP and I started by trying to calibrate the received power in > USRP by giving a known sine signal. I gave a signal of *100.2 MHz at -30 dBm > * to USRP which sampled it at 1MHz then passed it to a 1024 point FFT scope > in Gnu Radio Companion. I saw a level of about* -52 dB at 100.2 MHz*. > > I also modified the *usrp_spectrum_sense.py* to find FFT of same signal > using gr_fft_vcc function and then print the magnitude squared value to a > csv file. When I took 10*log10(value) the plot showed me about* -30dB level > at 100.2 MH*z. Following are my queries > > 1) Is the power level in GRC -52 dB or -52 dBm? Accordingly why is the -22 > dB loss? ( My antenna and channel gain were set to 0dB) >
The WX gui FFT plotter is scaled for dBfs. 0 dBfs is equivalent 1.0 sample counts, which is fullscale. > 2) Why are fft squared amplitude in dB different here and which one is > correct? > See ./gr-blocks/lib/nlog10_ff_impl.cc This uses the gr_fft_vcc and does various scaling compensation -josh _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
