Originally Posted by
AdrianR
You should be able to get away with using the single LNB and looping it through because all your VAST transponders (according to ) are on the vertical polarisation.
You will just have to switch one of the boxes' LNB Power to the "OFF" mode to avoid sending a second 13V voltage down the cable. As far as I know, you would leave the first box's LNB Power to "ON", and the second one that is getting it's signal via loop-through to the "OFF" mode. And, I reckon one should do this before connecting the LNB cable, because default setting is "ON". Switch the box on with no signal being input (zero on strength and quality), change the setting, save it, then power down, attach LNB cables, then power boxes back up. Just for safety's sake. I don't think the LNB would enjoy 26V running into it, or disconnecting/connecting it's feed whilst the box is on and powering it. Also, you can sometimes feel it shocking at the F-connector a little in your fingers if you do it that way.
In other words, the first box in the chain controls the LNB polarity. It will select vertical polarity by powering the LNB. Note that in this configuration, you WILL NOT be able to watch any horizontal channels on the second box, as long as the first box is set to a vertical channel. But, since it is only for VAST, you will only use the vertical channels, so it won't matter.
If they were mixed V and H channels (some transponders H and some V), then you would have a problem and would need to install the dual LNB instead, so each box gets its own feed.
If you were forced to use a single LNB, then to watch a horizontal channel on box 2, you would need to tune box 1 to a horizontal channel first. Basically, in this chain setup, both boxes need to be tuned to the same polarity. The first box controls because it is sending the power. The second box is sending zero power so it can only watch channels on the polarity box 1 is watching. Box 2 depends totally on box 1 basically.
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