[mythtvnz] LNB power with dual DVB-S cards

[David Shepherd]

This had me stumped for a while so thought I'd record what I learned 
today for anyone else who needs it.

I have 2 DVB-S cards in my backend.  A Hauppauge Nova-S and a SkyStar 
Technisat.  I also had a Zinwell/DSE Freeview DVB-S box plugged directly 
in to the TV. (I bought this when I cancelled Sky and before I got the 
DVB-S cards sorted out)

I had the cable from the dish going into the Zinwell then from the 
Zinwell to a single power-pass splitter to each DVB-S card.  Everything 
worked fine, multi-rec from both cards etc.

I just upgraded my telly to one with Freeview HD built in, so I no 
longer needed the Zinwell/DSE Freeview DVB-S box.  I also bought a all 
power-pass splitter because I was pretty sure that the Zinwell was 
powering the LNB.

So after lots of connecting and disconnecting from splitters, probing 
with a multimeter and testing LiveTV, I discovered the following:

1) The Skystar Technisat card provides LNB power (~18V) all the time, 
even when not recording.
2) The Hauppauge Nova-S card provides LNB power ONLY when recording.
3) When feeding both cards from a all power-pass splitter stops BOTH 
cards from working (possibly overpowering the LNB?)
4) Using the single power-pass splitter works fine ONLY IF the Technisat 
card is connected to the power pass side and the Nova-S card is 
connected to the the no-power-pass side of the splitter.

So it all works fine again now.

Cheers
Dave