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

[Kenneth Aafløy <ke-aa@frisurf.no>]

Sorry about the short replies, in a hurry...

On Saturday 12 June 2004 00:30, Ragnar Sundblad wrote:
> --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.

You did read that my post had nothing to do about voltage levels, as that is 
as easy as riding a bike.

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

Exactly my point.

> >> 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.

I would belive that there is already an amp in there.

> > 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.

And where does that come from?

> > 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.

So we are still in the plenty of mhz area, hmm?

> 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.

Oh, so the tuner (the sensitive part) is in a tin-can and the rest is outside?

> (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?)

Hu, what are we talking about here? The Hauppauge thread recently seen on this 
board?

> > 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.

Are you absolutly sure that this statement is accurate? I've been operating my 
DVB-S card for over a year without hardware flaws, and if you'd like it, I 
could seek some advise from friends who are running DVB with MythTV and other 
transmission standards than DVB-S.

> > 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.

I did not say I used the Video out feature of this card, if you look closely I 
indicate that I don't use it at all, because my DVB-S card is in my server, 
and my frontend is booting off this server.

> > 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.

Would you say that PCI transfer errors are rare or ?

Kenneth