[linux-dvb] Re: Couple of frontend questions

[Oliver Endriss <o.endriss@gmx.de>]

On Saturday 28 February 2004 22:46, Johannes Stezenbach wrote:
> Oliver Endriss wrote:
> > 
> > In the past I did some tests and found that tuning is always faster if zig-zag
> > scan is disabled. So the first thing I do after a check-out is disabling this
> > cra^Wstuff. -> Never had any problems (QPSK BSRU6, Grundig 29504-451).
> 
> Normally it doesn't need to do zigzag. If it does unnecessary zigzag,
> then it needs to be fixed properly (which is what Andrew tries to do).

I haven't tried the new code yet. The old code had the problem that it could
obtain a lock on the neighbour transponder. This must not happen.

Due to different AFC ranges the zig-zag range should be adjusted depending on
the frontend type. A zigzag_range parameter could be added to the dvb_frontend
struct. [*]

> > (b) the LNB is broken (high LNB drift)
> 
> Well, I'm not an experienced LNB guy, but IMHO what you call "broken"
> is just normal behaviour. Low price -> high drift. And it also
> depends on how large the temperature variations are.

For me, 'broken' is a drift which is larger than the AFC range. ;-)
I remember we already had this discussion some time ago. At that time I had a
phone call with Kathrein technical support. They stated that LNB drift can be
corrected by AFC.

My personal experience is that it is safe to disable zig-zag scan.
So I would prefer a module parameter to disable this feature.

Using [*] this could be easily implemented as a module parameter of the
frontend driver. So zig-zag scan could be disabled or adjusted for each
frontend type. What do you think?

Oliver


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