What is an LNB?
LNB is actually an abbreviation for “Low Noise Block” and it is the little box that sits on the arm pointing to the middle of the satellite dish.
The LNB has the signal from the dish reflected on to it
A standard system might have what is called either AN LNB or a Single LNB, this means basically there is only one connector on the LNB and one signal line down from it.
However you might want to be able to watch Television on two different TVs in your Motorhome / Caravan and this is where it gets complicated. You can get a splitter which will act like a T-Piece and divert one signal cable into two different directions to two televisions for instance, however this won’t work as intended if you want two entirely indepedent televisions capable of watching different channels on each at the same time.
Why does this happen?
Satellite receivers send voltage and signals to the LNB to get the LNB to change frequency and ‘polarisation’ as some TV channels are Vertical and some are Horizontal. If you had two receivers both trying to switch the same single LNB only one box would get the channels and the other would get no signal. So although you can split it in this fashion the restriction is that both TVs would really need to be watching the same channel.
If the system has a TWIN LNB i.e. two individual and separate cable connections coming out of the LNB then each individual cable can be diverted to its own dedicated TV and give 100% independent channel watching on each TV.
Alternatively some satellite receivers have twin tuners integrated in to allow you to record one channel whilst watching another, to get this type of functionality twin lnb satellite system configurations are required.