Diplexer: What Is It?!
April 18, 2008 5 Comments
A diplexer is an RF (radio frequency) coaxial device that operates and looks quite similar to a standard RF splitter/combiner. The diplexer is a reversible three-port device.One port can be used as an input, and the other two ports as outputs. In this fashion, the diplexer acts as a splitter.When reversed, two ports can be used as inputs and the third, as an output. The diplexer then acts as a combiner.
However, the diplexer is a bit more specialized than the standard splitter/combiner. Unlike the splitter/combiner, the diplexer is a frequency-selective device. When the diplexer is used as a combiner, filters inside of the diplexer allow two different frequency bands, each at its own power level, to be multiplexed and outputted on a single coaxial cable. The signals are not mixed, meaning that at the output of the diplexer, there are two distinct frequency bands, instead of just one wide band, and the power levels are not added together. Diplexers are typically used with high frequency satellite signals, and low frequency CATV/OTA (over-the-air) antenna signals, for transmission down a single coaxial cable.
A second diplexer, acting as a splitter at the opposite end of the coaxial cable, then separates the two frequency bands, each with its own respective power. The satellite signal goes out of one port to the satellite receiver, and the CATV signals go out the other port to the TV tuner.
Here are two diplexer products.
- The first is the OnQ Diplex Filter Assembly. One filter assembly is required at each of of the coaxial cable.
- The second is the OnQ 1×4 Satellite Diplexer Module. The module is designed for installation within an OnQ enclosure, and multiplexes the signals together for distribution out to four locations. Do note that four Diplex Filter Assemblies are required to complete the system, one at the far end of each coaxial cable coming from the 1×4 module.
So there you go. The next time you encounter an installation requiring both satellite and CATV/OTA, or even modulated signals from a security camera, and all you have to work with is a single coax cable, break out with the diplexers, and call it a day.
This is splendid. I have DISH network and a Comcast cable modem, and I am a TIVO addict – it is way better than Dish’s DVRs, but with the battles between Dish and TiVo just nearing an end, it’s not likely any changes will effect my older equipment from either company – but THESE nifty buggers will let me run Comcast basic cable down the same wire as the Dish feed, and once in the room, split it off as required. Looks like there is only one device type and it whether it muxes or demuxes depends on how you’re connecting it, is that correct? Only nub is that the twin leads out appear to be all male – so I’ll use a barrel connector to gender change as needed on the “mux”/diplex side, correct? Somebody hip me please…thanks much!
ps – shoulda known you’d have a cool website – you’re in San Diego – the miraculous city in which my robot leg was reconstructed back in April 2008! peace & blessings to all San Diegans 4ever!
Hello, Dave G,
I’m glad you found the blog topic useful. You are correct in that the OnQ Diplex Filter Assembly will either combine or seperate the satellite and CATV/OTA signals depending on how it’s connected with reference to the signal source.
The picture on our website does not clearly show the connectors of the diplexer, but to clarify, yes, the twin leads have male F connectors, however, the single connector on the body of the diplexer is a female F connector. The female F will have the combined signals for transmission down a single coaxial cable, and the male Fs typically connect directly to the source or destination hardware.
Robot leg? Work done at UCSD maybe? Drop by and say “hello!” if you are ever in town!
pls i ned a diagramatic representation on how to connect two satellite reciever together via their RF output to other tv’s.pls send to my mail box.thanks
Can you set the RF output on one of your satellite receivers to Channel 3, and the other to Channel 4? If yes, use two splitter/combiners. Use one splitter/combiner (two in, one out) to combine the two RF channels, and a second splitter/combiner (one in, two out) to split the signals going out to the RF input of your two TVs. Tune the TV to either channel 3 or 4.
If you can’t do the above, and your receivers have a composite video output (yellow RCA) and L/R audio output (white and red RCA), you can take these outputs and run them through a two-channel modulator. The modulator will convert the analog signals and produce two RF channels, each viewable on your TV via the tuner.