Am 15.08.2015 um 01:55 schrieb Marcus D. Leech: > On 08/14/2015 04:52 PM, Michael Thelen DK4MT wrote: >> Hi, >> >> I have two questions to the above mentioned Tutorial chapter, since I >> realized two differences, even though I think I set it up the same. >> >> a) To get an acceptable view in the Waterfall graph I had to adjust the >> frequency to a fourth of the suggested value in the tutorial picture. >> Please compare in my attachment Flowgraph_2-4-5.png, where the value is >> marked with a red arrow. Why could that be? >> >> b) How could it be managed to set the X-axis of the Waterfall graph from >> -50 to 50 in the picture of the tutorial? In the documentation is stated >> that this is related to the bandwidth value of the GUI Waterfall item. >> So I could only change this by setting the bandwidth to 100k. But than >> the maximum frequency is shown as 40kHz instead of 20kHz and the >> triangle pattern stays the same. This does not seem correct, as the >> frequency reading would be wrong. Please look at Waterfall_2-4-5.png. >> Again marked with red arrows. >> >> Refers to: >> http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorial_GRC >> -- Scroll to 2.4.5 >> >> Best regards >> Mike >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > The "bandwidth" setting on the waterfall is just to allow it compute the > X-axis legend along the bottom, which in your attached pics shows -24kHz > to +24kHz, > although the last actual numeric marker in each direction is +/-20kHz. > > Again, if you set the bandwidth to 100kHz in the waterfall, that will > dutifully calculate the markers to show +/-50kHz. But setting the > "bandwidth" in the > waterfall does *nothing* about the actual delivered sample rate. It's > just a hint to the plotter about the bandwidth of your signal. Nearly > the entirety > of Gnu Radio doesn't really "know" anything about sample rates--they > are an artifice that only becomes "real" at the edges with actual > hardware, and > also as a convenience when calculating filter parameters. > > Hi, yes ok that is clear so far. And this his how it is described in the documentation tab. The question arose, because in the tutorial I cannot explain how the adjustment and the result go together in the pictures. If you look at the flowgraph in the tutorial the bandwidth is set to 48k, but the X-axis labels in the Waterfall GUI go from -50kHz to 50kHz implying that the bandwidth might have been set to 100k. I am just trying to get the basics right.
BR Mike _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
