What are Satellite Diplexers and what are they used for?

Satellite diplexers are signal combiners / splitters for combining regular antenna signals with satellite signals along a single coaxial cable.

Most pay satellite services like Dish Network and DirecTV do not provide all the local channels for any particular city. That is where diplexers and a regular antenna (often referred as an off-air antenna or over the air antenna) come in.

Diplexers allow the signals from a regular antenna and a satellite dish to share the same coaxial cable.

This is especially useful for pre-wired homes where there is usually only 1 coaxial cable going from the attic or cable box to each wall drop. Adding more coaxial drops inside a wall can be very costly and a major headache. It is much easier and less costly to just use diplexers for each room where you want to run your regular antenna signal in addition to your satellite service.

The 1st diplexer takes 2 cable inputs, one from a satellite feed and one from an off-air antenna. A diplexer has a single cable output where the two signals are merged. Another diplexer is used at the satellite receiver to separate the two signals back out. A diplexer is a signal combiner and splitter in one. This is why you need two diplexers for each cable run to a receiver. One to merge the two signals, another to split them back out.

If your satellite system is using a multi-switch with a built-in diplexer, then you will only need one diplexer per receiver. The diplexer built inside a mutli-switch combines the off-air antenna signals. This can cut the number of diplexers needed in half since you will only need a diplexer to split the signals back out at each receiver.

See the links to the left for common diplexer setups

Cable Television and Cable Internet Service Applications

Most cable television and cable internet service providers use the same frequency ranges as off-air antennas.

For such applications you can use diplexers to combine your cable service in with your satellite service without having to use extra cabling. Instead of connecting the off-air antenna to the diplexer antenna port, just connect the coaxial input cables of your cable service provider into the diplexer. This is useful for homes that receive both satellite service and cable service (even cable internet service).

Diplexers should not be used for two signals that have overlapping frequency ranges. Check with your cable provider to make sure they only use low frequencies below those used by satellite services (typically below 950 MHz).