[mythtv-users] LNB configuration for second DVB-S2

Josu Lazkano josu.lazkano at gmail.com
Fri Aug 12 10:39:02 UTC 2011

2011/8/12 Simon Hobson <linux at thehobsons.co.uk>:
> Josu Lazkano wrote:
>>Hello forum, I just bought an other DVB-S2 device and I have problem
>>with LNB frecuency.
>>I have a dish pointed to Astra19.2E and with one DVB-S2 device I have
>>no problem, I just configure it as Universal LNB and it works great.
>>But for the second device, I add this on the cable:
>>I connect the two outputs to both devices and now I have no signal on
>>both devices. I must configure the LNB with other frecuencies?
> You have a big problem doing that.
> The LNB actually does part of the tuning - it selects one of four
> combinations of polarisation (horizontal or vertical) and band (low
> or high). Thus at any time you will only ever get about 1/4 of the
> available channels down the cable. The tuner sends signals up the
> cable that both power the LNB, and instruct it which of the four sets
> of signals to select.
> This is VERY different to terrestrial or cable systems where the
> entire set of channels comes down the wire at the same time - and you
> just pick out the one you want.
> It is possible to split the signal - provided you have enough of it
> to start with - but you will have to do two things :
> 1) You will need to disable or block the signals from one of the
> tuners - otherwise you could have one sending a control signal for
> one group, and the other sending a different signal. Even if they
> select the same group of channels to be sent down the wire, the
> signals can interfere such that the LNB doesn't get anything it
> understands.
> 2) You will need to configure the system so that it knows that it can
> only tune channels on tuner 2 that are in the group selected on tuner
> 1. I don't know if Myth can handle this, and if it does, how to
> configure it.
> The other problem you may have is that a passive splitter loses a lot
> of signal - each output gets less than half the power fed into the
> splitter. Unless you have an excess of signal, you may not have
> enough left for the tuners to work (reliably, or possibly at all).
> So in summary, no matter how difficult, you really want to get a twin
> output from the LNB. I'm guessing you have an old Sky minidish - you
> may find the following links useful :
> http://www.satcure.co.uk/tech/page10.htm
> http://www.satcure.co.uk/accs/quad_sky_lnb.htm
> This guy has a LOT of information on his site.
> Or just stump up and get a whole new dish fitted.
> --
> Simon Hobson
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
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Thanks Simon, I just want to watch Digital+ channels:

This are the frequencies:

10729.00	V
10788.00	V
10817.50	V
10847.00	V
10876.50	V
10935.50	V
10979.00	V
11038.00	V
11097.00	V
11126.50	V
11156.00	V
11317.50	V
11435.50	V
11508.50	V
11597.00	V
11626.50	V
11685.50	V
11739.00	V
11778.00	V
11817.00	V

All of them are on the same polarization.

I need to configure both devices with same parameters? I have a DC
blocker to put on the splitter, is this necessary?

Sorry for the newby questions, this is new for me.

Thanks for your great help.

Kind regards.

Josu Lazkano

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