I have a diplexer and a twin LNB. My primary decoder is the 4 series, secondary is the 5 series decoder.
So with the info supplied, both decoders would be configured for normal network settings for a Universal LNB.
Secondly, the HB cable connection have to be via a separate cable from the RF OUT or IN port on the Primary 4U.
Then the HB cable would have to be combined with the LNB cable before connection to the 5S decoder.
The diplexer would need to be connected in reverse to its normal connection for optimum performance and placed behind the 5S.
The ANT port connected to the cable coming from the Primary decoder as the HB.
The LNB cable connected to the SAT port. The I/O port connected to the LNB IN port of the 5S.
This assumes that there is a cable from the LNB to the 5S in the other room.
Octo LNB; 2 by 2x4 MS; 2 by ES 5-2; Dedicated PSU for LNB, ES's, MS's; HD PVR 4P x 2; Explora 1; DSD 660; FSM
So you have two houses or something? In the other threads you had an Explora 1 and no 4 series.
Anyway, the info should be complete for what you need here.
No, a twin LNB would be enough to handle those two, even with future proper Hi band. But the 5 series would operate a bit better with unicable so a LMX502 SLNB is recommended (or LMX501 - see my later reference).
With a twin LNB, the 5 series needs a diplexer in reverse for the HB which is then separately connected to a 4 series RF port.
With a SLNB, the 4 series just needs a diplexer. Should then allow HB via SLNB, but that's not guaranteed to work.
If an Explora decoder was added later (the only expansion option offered by MC here), you would need to change to a SLNB, and then need the LMX501.
But HB via SLNB is known to possibly cause problems in this specific set of choices, so the conventional HB method suggested with the twin LNB option is maybe the best HB choice all round if there's room for the extra cabling.
Re another thread: if you want further help - please make sure you answer any questions fully, else there's not enough info to help you.