Guide To TV Aerial & Satellite Combiners – Diplexers, Triplexers & Quadplexers
With all the types of broadcast services that are now available to us. It’s possible that if you wanted to receive TV Aerial, satellite, FM & DAB radio signals in your property, or just a couple of these. You could literally have hundreds of cables run all over the place. A lot of the time this is completely unnecessary as you could combine many of the services onto one cable dramatically reducing the amount of that need to be installed.
As each of the services mentioned above employs a different frequency band to transmit on. The signals can be combined without interfering with each other. Well technically this isn’t 100% true but signals from different frequency bands will only ever cause a problem really when the become too strong, so it’s not the combination of the signals that is the problem but the strength of the signals.
To understand how to combination of signals works it helps to have an understanding of frequencies and frequency bands. I am in the process of writing a more detailed blog on this butt here are some basics for you to get you started.
Frequencies & Frequency Bands
A radio wave with all TV and radio signals are broadcast on is an electro-magnetic current which is transmitted wirelessly from a transmitter to a receiving antenna or some sort of aerial. TV aerial signals like that used by Freeview are broadcast from a land-based transmitter and received by a TV aerial, the same is true with FM & DAB radio signals are received by an FM aerial and DAB aerial respectively. Satellite TV on the other hand is broadcast by way of geo-stationary satellites in space and received with a satellite dish. To avoid each of these different transmissions from interfering from one and another, plus loads more like those used for mobile internet services, each are broadcast using different frequencies.
Hertz, Kilo-Hertz, Mega-Hertz & Giga Hertz
A frequency (Hertz) is the amount of times that an alternating wave current (AC), also knows as a Sine wave that completes a rotation between a negative charge to a positive charge and back again per second. So, one cycle per second would be 1Hz. Mains electricity uses 50Hz in the UK so that would be 50 cycles per second. Radio waves that are used for radio and terrestrial TV and broadcast in the VHF and UHF, which stands for Very High Frequency & Ultra High Frequency.
Kilo which is metric for one thousand, means that Kilo-Hertz which is one common representation of TV frequencies stands for 1000 Hertz. Mega in the metric system stands for one million making 1Mhz actually 1,000,000 Hertz or 100,000Khz. Giga which is metric for one thousand million or one billion makes 1GHz equivalent to 1,000,000,000Hz, 1,000,000 Khz and 1000Mhz. That’s a phenomenal amount, right? Regarding TV distribution the highest frequencies we deal with are Gigahertz that are used in satellite broadcasts. But things like Terahertz (Thz) exist are for things like X-rays, gamma rays and visible and non-visible light.
VHF – Very High Frequency
The VHF, short for Very High Frequency is a frequency band that is used for radio signals such as FM & DAB. The VHF is covers all frequencies between 30Mhz-300Mhz. TV Signals used to be broadcast within this range but it’s main use is for radio today. FM uses a frequency band of 88Mhz-108Mhz. This means that when you tune your car radio in between stations you are alternating between broadcasts with this frequency range. DAB uses a frequency band of 170Mhz-240Mhz.
UHF- Ultra High Frequency
The UHF, which is short for Ultra High Frequency is a frequency range between 300Mhz to 3Ghz. This really is a busy part of the spectrum now with TV signals now being broadcast between 474Mhz to 786Mhz with Tetra signals, which is a communication band for the emergency services which operates around 395Mhz and 4G mobile broadband signals now broadcasting between 794Mhz to 850Mhz. It’s worth noting that although this hasn’t happened at the time of writing this but may be in use by the time of you reading this 5G will be broadcast using a frequency band between 706Mhz to 786Mhz.
Satellite KU Band & Satellite Intermediate Frequency Band (IF)
Finally, the most relevant frequency bands concerning TV and radio reception are the satellite frequency bands. As satellite TV is broadcast using frequencies that are way to high (KU band) to be contained within the connecting coaxial cables, these are oscillated down at the LNB of the satellite dish to a usable frequency band that the coaxial cables can handle without exception cable losses (Satellite IF). Satellite TV mainly broadcasts on the KU band which ranges between 12-18Ghz with satellite TV broadcasts in Europe using a downlink between 10.7Ghz to 12.75Ghz. After this has been received and oscillated at the satellite dish this uses a 950Mhz-2150Mhz range. This is what we are most concerned with in regard to combining TV and radio signals.
Combining Two Signals Together – Diplexers
Now that you can see that two different frequency groups can be combined without one and another affecting each other. Actually, two exact same signals can be combined together to increase the signal strength but it’s not very common or a task for the feint hearted as when done incorrectly the two signals could as easily cancel each other out rather than add together, but that’s not relevant today and I will get back to the point!
If you want to combine two signals together the piece of equipment you will require is called a diplexer and this would need to be appropriate for the signals you wish to combine together. A two-way splitter installed in reverse, so that the outputs become inputs and vice versa can actually work to combine signals together but’s not a good way of doing things. One, because you will lose more signal associated with the combination and two because a diplexer will actually help only filter through the signals that you wish to combine. For example, an FM aerial can actually still pick up TV signals, albeit a fair amount weaker and when combined with a two-way splitter these unwanted TV signals drifting in from the FM aerial can actually cause problems with TV reception.
Thus, if you wanted to combine a TV aerial and satellite signal together this can be done with a TV/Sat diplexer. Or if you wanted to a FM and TV aerial together you would need a TV/ FM diplexer or a UHF/ VHF diplexer. You should be careful when combining TV aerial and satellite signals together that you’re not combining onto an aerial cable that is carrying line power, like that used for the powering of masthead amplifiers and remote eyes as the same coaxial cable can not be used to carry two separate DC voltages to power an LNB and other piece of equipment. You can also purchase indoor and outdoor versions, they’re basically the same but the outdoor model will usually be slightly more expensive as they come with a weather proof housing. A common diplexer for combing aerial and satellite signals together is called a DIP2 diplexer.
If you wanted to combine FM & DAB radio signals together, rather than installing two separate aerials and a combiner. There is actually an appropriately named FAB aerial on the market which is two omni directional FM and DAB dipoles combined together which will achieve the same result. The forward gain on the aerials isn’t great when compared to directional aerials, but simply getting the aerial installed outside near your TV aerial should make a huge improvement to your radio reception and it’s usually small enough to fit onto your existing aerial mast, meaning that you don’t usually need to install separate brackets for the antenna.
Combing 3 Signals Together – Triplexer
Following on from the same principles as diplexers, to combine three different signals together you need a diplexer. Again, a three-way splitter installed in reverse could be used but this really wouldn’t be a good way of doing things for the same reasons already described. There are various triplexers on the market giving you the option of combining TV/ Radio & satellite signals together. If you wanted to combine radio, tv aerial and satellite signals together you would need something like a VHH/ UHF/ Sat Triplexer.
The most common reason that I install triplexers would be for communal IRS systems. Most launch amplifiers and multi-switch amplifiers have one terrestrial input for VHF & UHF signals and 4 separate inputs for the satellite bands from the Quattro LNB. This means that to have TV/ FM & DAB all present on the system a triplexer would need to be installed. This would usually be done at the aerial array or the headend equipment.
Combing 4 Signals Together – Quadplexers
I’m sure by now you can guess what this will be. A Quadplexer combine TV Aerial/UHF, FM & DAB and satellite signals all onto one cable. Usually this will be done to combine all the services to the lounge, so you can have them all off one cable. A second cable would also usually be installed in this type of situation to the lounge also from a satellite dish so a satellite PVR can be installed, like a Sky+ or Freesat+ box, but not a Sky Q box. I will get to that later!
Separating TV/ FM/ Sat Signals On One Cable
Once you have combined the signals onto one cable, more often than not you would need to separate these at the other end so that you can both or more services all running simultaneously. This can be done with a similar diplexer installed at the TV or radio side to separate the signals installed in reverse, or if you have to a two way/ three splitter but never with satellites as these won’t work properly through a passive splitter. I would suggest the best and most neat way of doing this as well as being the most popular would be through a Diplexed, Tripxed or Quadplexed wall plate. These have separate outputs that you can connect your coaxial cables into to each piece of equipment but beware just because you may have a wall plate that has two separate outputs, TV and satellite for example. If doesn’t necessarily mean that it is a diplexed wall plate and it may have separate cable inputs meaning that you can’t use a diplexer with these and must install separate cables.
Diplexed Wallplates – Separating Two Signals On One Cable
To separate two signals that have been combined with a wall socket, you will need a diplexed wall plate. The most common of these would be a TV/ FM socket or TV/Radio socket which would allow both DAB and FM through on the radio side. Lots of different types are available so it’s really just a case of buying and fitting the appropriate diplexed outlet that you require. Another common one would be the TV/ Sat Diplexed wall plates.
Triplexed Wallplate – Separating Three Signals on One Cable
When you need to separate three signals that have been combined onto one cable you will need a Triplexed wall plate. Like the diplexed sockets there are couple of different types available to you but by far away the most common Triplexed wall plate would be a TV/ Sat/ Radio version. These are most commonly associated with single feed communal IRS TV system where each flat and apartment would be able to receive TV via a TV aerial, FM and DAB radio and satellite. As there is only one radio output to have both FM and DAB feeding into separate radio inputs this would need to be either split with a splitter or via a FM/ DAB diplexer. You can buy plug in versions of these that just plug into the front of the wall plate to overcome this problem.
Quadplexed Wallplate – Four Signals In One Wall Socket
Now I know what you’re thinking as the way that this blog has gone so far, that I quadplexed wall plate would be a wall plate for satellite, TV Aerial, FM and DAB radio and these do exist but by far the most common and certainly the one most aerial and satellite installers would be referring to when they describe a quadplexed wall plate would be a wall plate with TV Aerial, Radio, Sat 1 and Sat2 outputs. This would allow all the benefits of a triplexed wall plate with the added benefit of being able to connect a satellite PVR, like a Sky+HD box or Freesat+ box. Quadplexed sockets differ from diplexed and triplexed wall-plates in the sense that they require two cables to connect to them. Quadplexed wall plates have a triplexed side that separates TV/ Radio and Sat signals from a single cable on input 1 and just a straight through connection on input two with no filtering and separation of frequencies. These are most commonly installed in communal IRS TV systems and as most likely both cables connect back the same multi-switch amplifiers so more times than not input 2 will also have TV aerial and radio signals on it too so often you can connect a second TV for another room for a TV aerial/ Freeview connection without having top fit any distribution or splitting equipment which is a nice little trick! The radio side would work the same as a triplexed wall plate where if you wanted FM and DAB you would need to install either a splitter or a FM/ DAB diplexer.
Combing Satellite Signals
There are certain things that apply to the combination of satellite signals that do not necessarily apply to combining TV and radio signals. This is because satellite requires a line power provided by the satellite receiver itself, to power the LNB on the satellite dish or at the multi-switch amplifier and to choose the satellite channels that it requires. It does this by switching the DC voltage between 13V and 18V and by switching a 22Khz tone off and on. Therefore, isolated wall plates that prevent a DC voltage from passing through for electrical safety will not work with satellite. Ultimately this means that TV aerial signals which may be carrying line power like that used for masthead amplifiers from power supply units or for remote eyes must not be used when combining with satellite signals. It will not work with the two separate DC voltages and the satellite must take priority in this situation as it will always need DC voltage present to work regardless.
Combining 2 Satellite Signals On One Cable
It’s possible to combine two or more satellite signals onto one cable. What equipment you use will depend on what you are trying to combine. Are you trying to combine two signals from the same satellite dish, so you can have recording facilities over one cable or are you trying to combine two satellite signals from two or more satellite dishes or LNB’s?
Stacker/ De-Stacker – Two Satellite Signals Down One Cable
A Stacker/ De-Stacker has got me our of trouble of a few occasions where extra cables can not be installed. A Stacker/ De-Stacker works by connecting two satellite signals onto one cable with a “stacker”. One coaxial cable will then leave this and run to where ever you need to “de-stack” the signals. At the other end a De-stacker will be installed to separate the signals, so you can connect your PVR. As there would be a frequency clash and a whole host of other reasons why this could not work otherwise, one of the cables that is connected to the Stacker, converts the signal to a higher frequency band that sits above the normal Satellite IF frequency band that finishes at 2150Mhz. This itself can cause problems for many reasons and several things must be correctly implemented if you’re to have success with a stacker/ de-stacker. Firstly, only the highest quality coaxial cable can be used between the stacker and de-stacker. This is because the higher frequency band used on one of the cables in just about within the limits of what a coaxial cable can carry and although there will be very high signal losses. For this reason, when you install a Stacker/ De-Stacker you need to pay close attention to the maximum cable distance of the model that you have as if you are to exceed this there is a very good chance that one of your satellite signals will not work properly. There are some models that have extra built in amplification or come with a separate line amplifier that will allow distances of up to 30m-40m so again you need to make sure that you buy the correct one before you install it. A good aerial and satellite engineer should be able to help you with this. You also should avoid the installation or fitting of any joins or wall-plates between the stacker and de-stacker, especially diplexed, triplexed or quadplexed models. These can usually be installed after the de-stacker if you really wanted a wall plate.
DISEqC Switches – Combing Two Or More Different Satellite Dishes/ LNB’s Together.
If you wanted to combine two or more satellite dishes or LNB’s on a multi-sat arrangement this can be done with a DISEqC switch, these come in varying types with some combining up to four separate satellite signals onto one cable. Although this isn’t common with Sky or Freesat set ups it’s very common with TV from Europe and foreign TV systems as there are a few different satellites carrying French, German, Spanish, Italian, Polish and all the countries around TV signals. Most common are the Astra 2, Astra 1 and Hotbird satellites. Once combined these can be connected to a single satellite receiver and when you switch between different satellites the DISEqC switch will simply switch to the satellites that you require. If you wanted more satellite signals from different satellites or the signals that you require are far apart you may benefit from a motorised satellite installation where the dish motor physically moves between satellites allowing access to some 30 different satellites!
If you wanted more than one satellite present on your communal TV system, this can also be done using DISEqC technology. In this instance you would install different satellite dishes or LNB’s with Quatrro LNB’s and connect these into your multi-switch amplifiers which will need to have at least 9 different inputs. Four for satellite 1, four for satellite 2 and 1 for terrestrial services like FM and DAB. This process can be extended for communal IRS systems with a 13-wire back bone (3 satellites) and a 17-wire backbone (4 satellites).
That’s it for this one, I hoped that you liked it. If you have any questions or need some help or advice. Please LEAVE A COMMENT in the section below. I’m unable to help or advice over phone or via e-mail to anyone outside our coverage area in the South East of the UK. Sussex and Kent. But if you leave a comment I will get back to you ASAP.
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