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

Dominik Kuhlen dkuhlen at gmx.net
Sun Jun 15 11:47:19 CEST 2008


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?
> 
> But under Windows no problems were detected, so it seems that all that 
> problems are solveable by driver (software).
> 
> BR,
> 
> Ales
> 
> 
> 
> _______________________________________________
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> linux-dvb at linuxtv.org
> http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
> 


Dominik
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