[Neil]

The LNB can actually receive a wide range of frequencies in both horizontal and vertical polarity (circular polarity is used on some satellites). The LNB converts the signal you require to view into a lower frequency that can be transmitted done the cable to your box. You have 4 choices, horizontal and vertical on both high and low band - it can only convert one of the 4 at once and send it to the box. That is why you need 1 cable per receiver.

It is possible to use 1 cable but you need expensive equipment. It is easier and cheaper to use a standard quad lnb with 4 outputs and a cable for each receiver.