Vlad It is apparent to me that you did not understand Josh's explanation. Possibly he was not forceful enough. ;-).
This is not an error. It is the mathematical consequence of doing QAM with rotational symmetries. YOU MUST provide your OWN synchronization to remove the phase ambiguity. It is not a bug or an error. It is a feature. It is the mathematical nature of the beast. Bob On Thu, May 19, 2011 at 7:55 AM, Vlad Stoianovici < stoianovici_v...@yahoo.com> wrote: > > Dear list and Josh, > I'm still getting this error when using the QAM Demod block (qamX_demod is > not connected internally). > Are there any new developments concerning these blocks? > > Vlad. > > > Josh Blum-2 wrote: > > > > Well, when you receive a qam signal, and lock to it, you still have some > > unknown phase offset. Lets suppose qam8 has two possible phases: 0 and > > 180 degrees. Since you don't know which phase is correct, you can look > > for the packet header in the received signal at 0 degrees and > > simultaneously at 180 degrees. Whichever phase offset yields a valid > > packet is the winner. Of course, this all assumes that you are framing > > your data with some kind of packet headers. > > > > Anyone else have some qam demodulation ideas to share? > > > > -josh > > _______________________________________________ > > Discuss-gnuradio mailing list > > Discuss-gnuradio@gnu.org > > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > -- > View this message in context: > http://old.nabble.com/QAM-demod-Error-in-GRC-tp23722153p31655276.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 > -- Bob McGwier rwmcgw...@gmail.com Amateur Radio Station: N4HY Engineer, Mathematician (Ph.D Brown University)
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