[linux-dvb] Re: TT budget DVB-C 1.0 tuning issues

[Esa Loukkola <esa@nic.fi>]

--On 23. September 2003 13:43 +0200 Robert Schlabbach <robert_s@gmx.net> 
wrote:

Hello and thanks for the tip,

> > 146MHz, symbol rate 6900 and QAM128 and 154/6900/128 do not tune at all;
> > The common denominator for the two frequencies that don't tune are that
> > they are the lowest in my network. 162MHz and all above it tune well
> As to your card, this sound like it might be a band switching problem. I'm
> not sure if the frontend driver has been programmed according to the ALPS
> TDBE2 specs - at least I have _not_ been able to find them anywhere, so
> maybe the current code is just "guesswork".
Yes, that would indeed seem to be the case, judging by this email:
http://www.linuxtv.org/mailinglists/linux-dvb/2002/10-2002/msg00087.html

> So look at the function tuner_set_tv_freq() in VES1820.C, the ALPS TDBE2
> is tuner_type == 1 and buf[3] is the band selection. I'd suggest
[snip]
> Now for 0x??, try all possible combinations of the lower nibble, i.e. 0x80
> through 0x8F. You could also try different charge pump settings, i.e.
> 0x0?, 0x4?, 0xC?.
I did just this, and wrote a small piece go through different combinations 
for the buf[3] settings. Alas, none of them worked :(.

Would playing with the other values in the buf-variable be of any use?

> If all of this doesn't work, the next thing would be to try and hunt down
> the ALPS TDBE2 data sheet, maybe it has some information on proper band
> selection...
Do you think this data sheet will tell us something which cannot be found 
in the datasheet mentioned in the above email (i.e. 
http://assets.zarlink.com/DS/zarlink_SP5659_MAY_02.pdf), e.g. related to 
the other buf values?

Also, importantly, I tested the card on Windows, and the same problem 
appeared also there -- which may suggest it might be a hardware limitation 
(or simply the driver is not up to it there either -- as low frequencies 
seem to be rare in the main market areas)?

Does anyone else have experiences with these DVB-C budget cards on low 
frequencies?

--
Esa Loukkola
esa@nic.fi



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