[linux-dvb] Lifeview LR306 clone does not receive ch 7.

[Hartmut Hackmann]

Hi, Folks

Peter D. wrote:
> On Sunday 17 September 2006 16:18, Philip Shead wrote:
> 
>>Hartmut Hackmann wrote:
>>
>>>Hi,
>>>
>>>Peter D. wrote:
>>>
>>>>On Friday 15 September 2006 06:16, Hartmut Hackmann wrote:
>>>>
>>>>>Hi, Peter
>>>>>
>>>>>Peter D. wrote:
>>>>>
>>>>>>Hi,
>>>>>>
>>>>>>I have an MSI TV at nywhere A/D that mostly works when "saa7134
>>>>>>card=94" is in /etc/modprobe.preload.  One of the interesting
>>>>>>quirks is that it does not recognize digital channel 7.  (I
>>>>>>think that that is transmitted on physical channel 6.)  It can
>>>>>>find and display all of the other channels, digital and
>>>>>>analogue, in the local area (Melbourne Australia).  Signal
>>>>>>strength should be O.K. My other dvb-t card can receive all of
>>>>>>the local channels, including ch 7.
>>>>>>
>>>>>>Any clues?
>>>>>
>  > >>> This can easily be a problem in your channels.conf file. There
> 
>>>>>are 2 possible causes:
>>>>>- some onf the conding parameters like FEC or GI are wrong.
>>>>>Some channel decoder ignore them, the driver for the tda10046
>>>>>does not. - In some countries, the transmitters are +/- 167kHz
>>>>>off the center frequencies. With the current driver, the
>>>>>tda10046 can't lock with this offset,you need to correct the
>>>>>center frequency.
>>>>
>>>>How do you determine what the correct center frequency is? 
>>>>Trial and error edits to /etc/dvb/channels.conf-dvbt-australia? 
>>>>Or do I just wait until the driver evolves to the standard of
>>>>the driver for the Kworld with its cx8800?
>>>
>>>Try and error or search for appropriate information.
>>>I will change the locking algorithm some time. But this is a
>>>difficult change and definitely not be there within few days.
>>
>>  Well I'm bemused by this. I have had the same card in my desktop
>>box (with no other pci card in it) and I had perfect service
>>on all 5 channels (working off the same frequencies as Peter D).
>>But today I pulled it out of that machine and stuck it in
>>my mythbox (with a Visionplus branded Twinhan card (dvb-bt8xx)
>>and a Kworld DVB-T card (using cx88-dvb)) and I am now
>>suffering the exact same problem with Channel 7 being unable
>>to tune. This machine has a much better antenna input (being
>>a short better shielded cable from a wall socket v 3 cables
>>strung together over 10m) and even skipping the passthrough
>>on the kworld and putting the  antenna into the msi card by
>>itself Channel 7 is not visible. 
> 
> 
> So, when the signal goes from the wall socket to the Kworld DVB-T card 
> in the first computer, out of the Kworld, across the room, into the 
> MSI in a different computer it can tune to channel 7.  But when the 
> signal goes directly from the wall socket to the MSI it can not tune 
> to channel 7.  This is interesting.  
> 
> 
>>On both machines I have a 
>>very old version of kaxtv (0.23) (config file copied from one
>>to the other) and on one the card could receive the missing
>>channel but on other it does not work.
> 
> 
> My other card is a Kworld V-Stream Xpert DTV DVB-T with Connexant 
> chips and a Zarlink tuner.  
> 
> Something is interacting badly with something else.  It could be that 
> each component behaves by itself but the system is unstable, or maybe 
> one (or more) component is broken in such a way that a simple system 
> can cope but a complex one can not.  
> 
> Maybe the signal strength is too strong.  I'll try attenuating it 
> later.  
>
This is possible with this tuner type. It has no sharp preselection,
so a very strong transmitter in the same band can distrb another.
An attenuator might help.

> Maybe EMF from one card is interfering with the other.  I might try 
> putting an insulated sheet of metal between the cards.  That could be 
> rather nasty if I short things out.  
> 
> Other people are running multiple tuner cards, so I guess it is 
> unlikely that one driver is interfering with the other - unless there 
> is something really odd about the MSI. 
> 
Is the tuner of the MSI card shielded ?

Hartmut