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Re: [Discuss-gnuradio] atsc signal plots
From: |
Charles Swiger |
Subject: |
Re: [Discuss-gnuradio] atsc signal plots |
Date: |
Sat, 06 May 2006 10:16:15 -0400 |
On Fri, 2006-05-05 at 14:45 -0700, Matt Ettus wrote:
> > The 2.0 port isn't doing as well - a few eyes show up here
> > and there:
> >
> > http://webpages.charter.net/cswiger/g2_eq_data-1.jpg
> >
> > and that's with the NOP equalizer. The LMS eq is all noise
> > all the time.
>
> To me it looks like the symbol timing tracker is not tracking properly.
> As the sample time shifts relative to the correct sample time you come
> in and out of alignment. As I recall, the equalizer comes after the
> timing sync, so it won't work. It needs proper symbol timing, and
> without it will actually make things worse.
>
Yep - looking at the 0.9 bit-timing-loop output:
http://webpages.charter.net/cswiger/g09_btl_data-1.jpg
vs a 2.x port of it shows something going wrong, using
the same input data:
http://webpages.charter.net/cswiger/g2_btl_data-1.jpg
could be something to do with differences in buffering,
scheduling, etc between gr0.9 and gr2.x.