On Tue, Jun 12, 2012 at 4:03 PM, Vivian Paola Triana Galeano <motis1232...@gmail.com> wrote: > Hi Everyone, > My name is VIvian and I am working with GMSK modulation. I have a little > doubt about it. > > I am transmitting a cosine signal using UHD sink and source blocks, USRP1, > daughter board RFX 2400. The spectrum that I transmit is the one that you > can see in the attached files. > > I use a network analyzer to see the real spectrum that I am sending and the > spectrum that I obtain can be seen in the other photo that I attach. > > Finally I look the spectrum received in GNU Radio, which is attached to this > email too. > > I found that the spectrum that I send is the half of the size that I see in > the network analyzer. I mean the spectrum that I send has a bandwidth of 200 > KHz ( I see this in GNU Radio) but the one that I obtain looking at the > network analyzer is approx. 400 KHz. When i see the received signal in GNU > Radio is perfect, its bandwidth is the same that I send ( 200 KHz). I dont > know why I see a different bandwidth in the network analyzer. Anyone knows > what is happening? > > I would appreciate any help you can give me. Thanks in advance. > > Vivian.
Hi Vivian, Just remember that the GNU Radio scope plots don't have to tell you the truth. Everything in GNU Radio really just runs off a unitless sample rate of 1, so samples/second are actually meaningless to it. We tell the scope what the sample rate is and it sets the x-axis scale accordingly, but we can easily lie to it. My guess is that there is a factor of two in the sample rate of the system that you aren't accounting for when creating the plot. Tom _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
