[mythtv] Current SVN DVB-S zapping problems (diseqc?)

Yeasah Pell yeasah at schwide.com
Mon Aug 28 20:48:37 UTC 2006

Lukas Kasprowicz wrote:
> Am Montag, 28. August 2006 21:15 schrieb Yeasah Pell:
>>> [card1]------|---------------|
>>> [card2]------| 8 ports in   |
>>>                 --| 2 ports out |----(port 1)------- [universal LNB]
>>>                 --| switch        |----(port 2)-------[empty]
>>>                 --|---------------|
>>> cards are connected to ports where i am _not_ able to switch if it has to
>>> use 22kHz for switching low/high. These are only diseqc ports.
>> I see. How does this switch decide which input to route to which output
>> at any given time? (Forgive me for the basic questions, I'm not familiar
>> with big multi-switches like this) I don't see how it can work if both
>> cards get connected to the same LNB, since the cards will both want to
>> supply a specific voltage, as well as a specific tone presence (to
>> control polarization and band) -- and they'll conflict if they are
>> connected to the same device (unless the switch disambiguates it somehow)
> I do not know what it is doing, too but i think it operates similar to a 
> network switch (maybe). Follow the link and you get the manual of the switch 
> i am using. Hope it answers all your questions ;)
> It is the Gigaswitch 11/8 i am using.
> http://www.technisat.com/download/en/man/247.pdf
> Lukas
Wow, that's quite a switch! From the manual, the most clear designation 
on how it functions is on the very first page, which is a picture of the 
top panel of the switch. It's designed to work by connecting a quad LNB 
to four outputs of fixed voltage and tone (generated by the switch 
itself), and as such you will of course need to have four pieces of coax 
running from the "sat-position A" group of switch ports (i.e. 18V low, 
13V low, 18V high, 13V high) to the 4 connections on the quad LNB. 
That's what you have, right? The diagram you drew made me think you only 
had one piece of coax running to the LNB, but it makes sense once you 
see the switch itself.

The switch then routes the receivers to the correct fixed-setup LNB 
output based on the voltage/tone/diseqc observed on that input, but 
doesn't pass the tone or voltage through to the LNB of course. Pretty 
slick. Looks like it even mixes in terrestrial antenna signals to boot.

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