Do you mean adding a text label on the vertical axis, or scaling the spectrum? For the latter, you would have to feed the USRP a known (calibrated) noise source that is well above the USRP noise floor such as an HP 346 noise source. Then read the value from the spectrum and just re-scale the samples to your known PSD. If you change the FFT bin size, decimation, tuning, etc, you may need to re-scale.
I suppose you could also feed the USRP with a CW tone of known power to figure out it's gain, then terminate the input with 50 ohms (i.e. -174 dBm/Hz) and measure the power (which would be -174 dB/Hz + NF + gain). In either case, you need a known power source to convert the dB to dBm, and noise to fill your bandwidth to get the 1/Hz. Lou KD4HSO activecat wrote > I am using USRP to receive signal, and then plot the signal using "WX GUI > FFT Sink". > I hope to get the vertical axis as "Power Spectral Density in dBm/Hz". > Is there any way to do that? -- View this message in context: http://gnuradio.4.n7.nabble.com/PSD-in-dBm-Hz-tp52572p52578.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
