[linux-dvb] Re : Re : Re : No lock possible at some DVB-S2 channels with TT S2-3200/linux

manu eallaud at yahoo.fr
Mon Jun 16 04:21:45 CEST 2008


Le 15.06.2008 13:20:30, Ales Jurik a écrit :
> On Sunday 15 of June 2008, Dominik Kuhlen wrote:
> > Hi,
> >
> > On Thursday 22 May 2008, Ales Jurik wrote:
> > > Hi,
> > >
> > > my friend told me that he is sometimes able to get lock by
> decreasing
> > > (not increasing) the frequency. Yesterday I've tested it and it
> seems to
> > > me he was right. So I'm able to get (not very stable, for few
> minutes)
> > > lock as well as by increasing and by decreasing frequency of the
> same
> > > channel (EurosportHD).
> >
> > The derotator code in the stb0899 seems to be setting the initial
> frequency
> > to the lowest search range and never changes this (as it should
> increase
> > steadily to find a lock)
> >
> > > It was also detected (not by me, I don't have riser card) that
> when the
> > > card is connected not directly into PCI slot but with some riser
> card,
> > > the needed difference for getting lock is higher (up to 10MHz). 
> So
> also
> > > some noise from PC is going into calculations.
> > >
> > > I don't think the problem is in computation of frequency but in
> for
> > > example not stable signal amplitude at input of demodulator or in
> not
> > > fluently changing the gain and bandwith of tuner within the band.
> As I
> > > see in the code some parameters are changing in steps and maybe 3
> steps
> > > for whole band is not enough? Especially in real conditions (not
> in lab)?
> >
> > Could you please try the attached patch if this fixes the problem
> with
> > nominal frequency/symbolrate settings?
> >
> 
> Many thanks, but I don't see any improvement. Minimum time after I've
> lock is 
> 150s. 
> 
> The only improvement was done 2weeks ago when Manu Abraham fixed some
> headers 
> with register addresses. From that time it is possible to get lock
> also at 
> problematic channels but very unstable.
> 
> But I've found that all channels with lock problems are DVB-S2, 8PSK,
> FEC 3/4. 
> So all channels broadcasted in QPSK is possible to tune without
> problems and 
> also channels broadcasted in DVB-S2, 8PSK, FEC 2/3 are possible to
> tune to 
> without problems. Channels in DVB-S2, 8PSK with different FEC (to 2/3
> and 
> 3/4) I was not able to test.

For me adding 4MHz solved the lock problems for DVB-S QPSK FEC 3/4, but 
did not solve my problems for a DVB-S QPSK FEC 5/6.
I will try Dominik's patch to see if it improves things.
Stay tuned (oh well)
Bye
Manu







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