On 06/30/2011 07:13 AM, Aleš Povalač wrote: > Dear all, > > I have been testing USRP2 with WBX board (#957). Using GNU Radio, I > have created a simple CW TX system. The problem: output signal is > oscillating when I set the TX frequencies to 900MHz band. Signal > output (in time domain) at TX/RX connector from the FSL analyzer is in > the attachment. > > Settings: > 868 MHz, 200 kSps, gain 15 dB > > Same results with: > ./tx_waveforms --rate 250000 --freq 868000000 --gain 15 > > The oscillation with ca. 1dB amplitude is present for almost all gain > settings except the lowest values. I have observed the problem at > several frequencies from 700M to 1G, sometimes with amplitude over > 2dB. > > Any ideas about the cause of this problem? Some PA instability or AGC > loop issue?
There is DC offset in the signal. Since you are using a 10 MHz RBW, you are seeing both the DC offset and the desired signal beating with each other. If you take your spectrum analyzer out of zero-span mode and zoom in on the signal you will see that the amplitude is constant. Matt _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
