It's not just an offset problem. Even though in the output file, there is a
delayed sequence, it doesn't have the right bits. As it has exactly the
same period it leads me to believe that it's just a problem of phase sync.

Attached is a minimal grc file.

Cheers,
Fabián

On Wed, Oct 3, 2012 at 12:23 AM, Ben Reynwar <[email protected]> wrote:

> On Mon, Oct 1, 2012 at 1:27 PM, Fabián Kozynski <[email protected]> wrote:
> > As sanity check I'm trying a simple flowgraph in GRC with a QAM
> mod/demod:
> >
> > Vector Source ==> Throttle ==> QAM Mod ==> QAM Demod ==> Unpacked to
> Packed
> > ==> File Sink
> >
> > The parameters in the mod/demod are as default. I also have a File Sink
> > before the mod.
> >
> > In the output I see first a bunch of zeros, then a bunch of random
> numbers
> > and after 20 or so bytes I get a sequence with the same period as the
> > original one, but different numbers. I suppose this is a problem of phase
> > sync.
> >
> > What's the right way to simulate a simple mod/demod? How do I add sync
> > between mod and demod?
> >
> > Thanks,
> > Fabián
>
> It sounds like you're comparing bytes in the two files.  First thing
> that I'd check is that the two files aren't offset from each other by
> a few bits so that the bytes don't line up in the same way.
>
> If that's not the problem then email me the grc file and I'll have a look.
>
> Cheers,
> Ben
>
> >
> > _______________________________________________
> > Discuss-gnuradio mailing list
> > [email protected]
> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >
>

Attachment: QAMMod.grc
Description: Binary data

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