Now I have another problem related to peaks in the fft plot, but in this case, with no transmitter.
Why does a peak appears at the center of the fft plot for some frequencies and not for the others. I mean, I am using a USRP2 to receive just noise and plot its fft and when I center my receiver in the frequencies 5.0GHz, 5.5 GHz and 6.0 GHz I have no peaks but for the other frequencies in the same band I do have them. In this case it is not related to LO leakage since I can't get rid of them and I have no transmitter. Also, the peak always appears at the center of the plot frankist wrote: > > Oops. problem solved. I had to increase the LO offset in the transmitter > (not the receiver)! *Facepalm* > > Thanks for the support > > > mleech wrote: >> >> On 07/04/12 10:12 AM, frankist wrote: >>> Hi, >>> >>> I am using GNU Radio for 2 weeks. I always get in the receiver side a >>> signal >>> with a peak in the carrier frequency when I turn on the transmitter even >>> if >>> I send a signal made of zeros. You can see it in the picture >>> http://old.nabble.com/file/p33648622/usrp_carrier_peak.png >>> >>> In spite of being handy to discover the frequency offset of my signal, >>> it is >>> influencing my results when I try to measure the power of the received >>> signal. I thought this was the DC offset, but I read somewhere that >>> USRP2 >>> eliminates the DC Offset. >>> >>> So, do you know what it is and how to remove it? >>> >> This is LO leakage. What is you setup here--two USRPs with XCVR cards? >> >> Mixers always have some amount of LO leakage at the output port. >> Depending on your signal bandwidth, >> you can use an LO offset to move that leakage outside of your >> applications passband, but there'll still be >> leakage--just not at a place that matters to you. >> >> -- >> Principal Investigator >> Shirleys Bay Radio Astronomy Consortium >> http://www.sbrac.org >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > > -- View this message in context: http://old.nabble.com/USRP-inserts-a-peak-in-the-carrier-frequency-tp33648622p33688986.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
