[linux-dvb] KNC1 SNR goes/went bad

Manu Abraham abraham.manu at gmail.com
Mon Aug 13 21:55:32 CEST 2007


> > Can you describe the problem that you face ? other than low SNR ? ie
> > have you checked whether your cables are okay, Dish is aligned proper
> > etc etc ? It will help to avoid a lot of frustration later. :)
> >
> >
> > Manu
> >
>
> That's great!
>
> The problems I face: I have a lot of BER, measured with femon -h (with
> my patch applied for decimal readings). The sky is clear. Visiosat Bisat
> G3C dish.
>
> On ZDF on Astra 19,2 east (Astra 1), I see nothing (and I mean
> _nothing_) but green and purple blocks and loud aliens in my speakers
> constantly. BER is into 65000.
>
> On Omroep Brabant on Astra 1D at 23,5 east, I see some bits from the
> image but constantly lots of complete stripes with corrupted MPEG, and
> the audio is also bad. So this stream is also corrupt. BER into 65000.
>
> Now ZDF is one of the weakest transponders on 19,2 east and Astra 1D is
> old so doesn't perform optimal either. But this is not normal.
>
> On BBC One/Two/Three/Four on Astra 2D, and that beam is strong in my
> location, the picture is good most of the time, but once approx every
> minute a small visible corruption passes by. Just as long as it does
> _not_ start to rain, I can follow the program. BER into 65000.


I understood your problem.

> On the Dutch channels on Astra 1 at 19,2 east again, like Nederland 1 at
> 12515.25 H (Astra 1G) or RTL 5 at 12343.50 H (Astra 1H) the picture is
> perfect, and BER hoovers and shows 0, 256 or 512 (which is low).
>
> There are also values in between. n-tv on Astra 1 at 19,2 east shows
> around 17000-18000. Perfect picture.
>
> But.. When it starts to rain, the whole party is over.


During rain, don't expect anything much with DVB-S


> So that's my problem. When I swap the KNC1 for my Technotrend S-1500,
> all the channels work, including ZDF, perfectly, and the BER is zero
> everywhere, even ZDF works with zero BER. There are many other channels
> that do not work but I couldn't possibly list them all, I don't think
> that would make sense anyway. And sure, there could be a little
> difference in tuner quality and stuff in favor of the Technotrend, but I
> really don't believe it would be that big for cards from the same price
> range. And it's not like Philips is a bad or cheap brand either.


Though i am not saying it is bad, devices designed improperly leads to
bad results. However good the components are. We have examples, but
not stating that is the case here, but a possibility.


> I'm actually not sure the SNR number in femon is low, I was really
> talking about Signal to Noise ratio - with all that corruption and
> horrible performance it has to be bad.
>
> On Windows, I can watch ZDF with the KNC1, but I see some "error" level
> in the  Windows software, that "error" most likely means BER. But it's
> not much. Last time I checked anyway, it's been a while since I've seen
> Windows.


If this is an overall problem that you see, then it has nothing to do
with the drivers. I thought in your case, the driver was misbehaving

The TT card you have behaves similarly ?

> The problem seems to be getting worse, because some days/weeks ago I
> believe I had zero BER at the Dutch channels, and now it's around
> 256-512. But the weather, temperature and other stuff also varies, so
> it's always hard to say.


Maybe it has something to do with your dish alignment, LNB alignment
etc ? A LNB skew can cause a lot of errors to happen, eventhough the
dish is aligned correctly.



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