To
better understand how a multiswitch works with a satellite antenna, lets
get an understanding of how the two work together.
The LNB on your satellite dish is capable of tuning to a satellite transponder that is broadcasting in either left-hand or right-hand circular polarity. A technical explanation of this is pretty involved and for the purposes of this explanation you'll just take our word for it. When you tune to a channel on your receiver, the receiver sends a switching signal back up the coax cable to the LNB in the form of a 14-volt or 18-volt DC voltage level to select the correct polarity for the transponder you have requested. This is why you cannot use a splitter for adding additional DSS receivers. If you do, the LNB gets a conflicting set of commands from the two sat receivers if they both try to access transponders of differing polarity. As a result, you can get a signal on one receiver while not the other if different transponders have been selected by each. You can set up two DSS receivers on a dish with a dual LNB using a dedicated line for each receiver. If you want to set up more than two receivers then you need a multiswitch.
A multiswitch is basically a box that contains splitters and A/B switches. The outputs of each LNB are connected to the A and B inputs of the multiswitch. In this configuration, one LNB is dedicated to left-hand polarity transponders and the other LNB is set up for right-hand polarity. The inputs to the multi-switch from the LNBs are split for either 4 or 8 outputs each (more if a larger multiswitch is desired). These split outputs are paired and connected to a series of A/B switches such that one side of the switch sees input A and the other side sees input B.
The outputs of the
multiswitch are routed to each receiver you have in your household. When you tune to a channel, instead of the LNB being switched to the correct polarity, the 14-volt or 18-volt signal selects either transponder A or B by toggling the A/B switch. The LNBs are no longer switched when you change channels. Instead, the switching occurs inside the
multiswitch (hence the name) and the correct polarity is selected for the desired channel/transponder.
Note that there are two different types of
multiswitches available - passive (unpowered) and active (powered). If you have cable runs longer than 100 feet for any receiver, a powered multi-switch is highly recommended. The long run can degrade the voltage output from the receiver and the
multiswitch may not work properly if the voltage drop is too great. A powered
multiswitch detects the difference in the voltage levels and compensates for it.
