[linux-dvb] Re: DVB-S with CI card to buy

[Ragnar Sundblad <ragge@nada.kth.se>]

--On den 11 juni 2004 23:44 +0200 Kenneth Aafløy <ke-aa@frisurf.no> wrote:

> The question if this is the case, which
> is pretty  obvious to me is who is to blame? The card producer that makes
> a card that is  borderline or the maker of the PSU which obviously has to
> be out of spec?
"the PSU which obviously was out of spec"?

I had to replace PSU too, and it absolutely wasn't out of spec.
It had a little low 12 V, but far above 11.9 V which is really
fine for every other use, and well within specs.
The new PSU had a 12 V of about 12.1 V, and that made my DVB-T FF
tuner work more reliably. Still not reliable though.

The one to blame is the one who don't make parts that accepts
the entire spec range. Actually, a well designed item should
accept environments beyond the specs, one of the things we do
know is that parts age, and then they may go a little out of
spec.

My new PSU had newer capacitors and maybe filters out noise
better. That might be the entire thing.

> > That is not the only problem with those cards;
> > My DVB-T FF card has an impedance mismatch between the tuner
> > and the demodulator that most probably explains why its
> > reception is so much worse than my set top box.
> Are you saying that the manafacturer used a lot of bad components on this
> board, or just that they put in the wrong capacitor?
They should probably have put an amp between the tuner output
and the demodulator input, I guess the best would have been
as part of the filter that sits in between.

> It sounds like you are getting the frequency of the power grid out on the
> composite output, at least in this context.
I you mean power grid as in the 230 V power that is absolutely
not the case, the lines/waves are of entirely different frequencies.
I have spoken to two different persons that have both a DVB-T FF
and some other DVB-x FF card, and both had this problem on the
DVB-T card and obviously used their other cards for video out.
The problem most probably comes from the power distribution
on the card.

> So the DVB-C/T cards does not have a ground shielded tin-box?, now is not
> that  just lame design, the cards receive frequencies around what DVB-S
> does (at  least after the LNB did it's job), and definatly higher than
> VHS+ :) or?
DVB-C and T is in the 50-900 MHz range, DVB-S is in the 1000-1800,
that really doesn't matter to much to the design in this case.

The difference I was talking about is that there are complete
tin modules with tuner and demodulators in a single readily
designed box for DVB-S, while for DVB-T and DVB-C designs
with only the tuner in a box with an analog output and the
demodulator on the board seems to be the common choise.
So far - there are intergrated tuner and demodulators for
DVB-C and T too now, maybe in a few years they will find
their way on the DVB PCI cards.

(Is there any card on the market that actually uses parts
that haven't been discontinued for at least a year?
Where do they get the parts?)

> All in all DVB-S cards are good, DVB-C/T cards are bad? ;)
I have no idea, but as I said there seems to be less common
with problems with the DVB-S cards.

All in all, the DVB cards I have bought are just not well
engineered. They have caused me a lot of trouble, and every
now and then they act up in one way or another. The system
isn't reliable at all.

> I can however go good for my Hauppauge Nexus-S, as a premium buy,
Just watch out for connecting the video without disconnecting
everything from the power grid, or earthing everything together
first, several are those that have fried their video outputs
on their FF cards since it isn't protected from even smaller
overvoltages (as every good design of course should be).
But maybe they have finally fixed this on the Nexus cards.

> as my
> only  problem was that motherboard that did not follow specs, which is
> very rare.
I wouldn't call different PCI problems on mother boards rare,
but the system tends to often work anyway.

/ragge