On 17.07.2015 14:56, Bill Eaton wrote: >> What I meant was that you plot the result of your timing + phase recovery > >> into an XY plot, that would take care of those additional points > you're seeing. > > I have to confess that I don't even know what that means or how to go > about accomplishing it. I have to take baby steps because I'm a baby. > ;-) If you could point me to an example or some other things to try, > that would be helpful.
OK, this is starting to get into basics of digital comms and this mailing list is probably not a good place for that. In brief, what you're plotting is the output of the QAM Mod -- which is *not* a QAM constellation, but rather the complex baseband signal that can be transmitted. This does include the QAM constellation. > I looked through the examples that ship with GNURadio and didn't see > anything obvious. Also, I looked through the GRC block tree to see if I > could try something. There's a Synchronizers section. Something from there? Try the examples in gr-digital. > You thought maybe it was oversampled. It occurred to me that maybe the > X-Y chart rate should be samp_rate/8, but I tried that and the chart > still look largely the same. That's not quite the right terminology, but if you plotted only a subset of the samples of your signal, you would see the constellation. It seems you're fine using GNU Radio itself, so I recommend you get an intro book to digital comms and map what the say to the GNU Radio examples. Cheers, Martin > > > > mlist_qam_constellation_xy.grc.png > > > > > > > > -----Original Message----- > From: discuss-gnuradio-bounces+billeaton=aeroantenna....@gnu.org > [mailto:discuss-gnuradio-bounces+billeaton=aeroantenna....@gnu.org] On > Behalf Of Martin Braun > Sent: Friday, July 17, 2015 1:20 PM > To: discuss-gnuradio@gnu.org > Subject: Re: [Discuss-gnuradio] trouble with QAM mod/ WX GUI > Constellation Sink > > > > On 17.07.2015 12:43, Bill Eaton wrote: > >> From Martin Braun: > >> > >>>My preference is to build the demod/sync chain with it's own blocks, > >>>and then just output the complex symbols > >> > >>> into either an X/Y plot (WX) or the QT Constellation Sink > >> > >> Even an X/Y plot ends up looking funny. I’ve attached a GRC file for > >> X-Y, and when you turn on persistence, it looks better. But it’s very > >> strange. Maybe my bits_per_symbol is wrong. Or maybe the sample rate > >> for the X-Y chart should be different than the random sample rate? > >> Here’s the 4 QAM X-Y. > > > > Your plot looks fine, it's just oversampled (but perfectly > time-synchronized, I'm guessing this is post-pulse shaping + noise?). > > > > What I meant was that you plot the result of your timing + phase > recovery into an XY plot, that would take care of those additional > points you're seeing. > > > > M > > > > > > _______________________________________________ > > Discuss-gnuradio mailing list > > Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
