Hello, I would like to capture signals using the USRP1 (rev 4.5) with DBSRX. For the first test I am using CW signal from generator at 1.501GHz, 0 dBm (verified to be precise). To capture the signal I use the usrp_rx_cfile.py (usrp_rx_cfile.py -R a -d 8 -f 1.500G -N 40064 -s -g 45 usrp.dat) I plot the FFT using Matlab (rectangular window, FFT length 65536). At first it appears fine (there is a DC component, but OK): http://www.nabble.com/file/p23724900/unzoomed_1.5GHz.png Zooming in the CW peak: http://www.nabble.com/file/p23724900/zoomed.png There is a lot of noise, the peak is not sharp (width 2 kHz). Looks like phase noise to me. Or is there very fast frequency drift? Thinking the signal might be saturated, I've reduced the gain. The frequency range is smaller, but also the SNR http://www.nabble.com/file/p23724900/zoomed_25dB%2Bgain.png I've tried to use hi quality external reference clock (64MHz), following the instructions form USRP Clocking Notes. Unfortunately there was no improvement. Is there an explanation for this behavior? Thank you. PS: Sorry for multiple posts, if any... -- View this message in context: http://www.nabble.com/USRP1-DBSRX-phase-noise-tp23... Sent from the GnuRadio mailing list archive at Nabble.com.
on 2009-05-26 19:04