What is scr on freesat?

Single-cable distribution is a satellite TV technology that enables the delivery of broadcast programming to multiple users over a single coaxial cable, and eliminates the numerous cables required to support consumer electronics devices such as twin-tuner digital video recorders (DVRs) and high-end receivers.

Without single-cable distribution, providing full-spectrum access for multiple receivers, or receivers with multiple tuners, in a single-family home has required a separate coaxial cable feeding each tuner from the antenna equipment (either multiple LNBs, a multi-output LNB or a multiswitch distribution system) because of the large bandwidth requirement of the signals.

Single-cable distribution technology enables one coaxial cable from the antenna equipment to multiple tuners, to provide independent tuning across the whole range of satellite reception for each tuner.

A European industry standard for distributing satellite signals over a single coaxial cable - CENELEC EN50494 - was defined in 2007 and developed by a consortium led by SES.

Single-cable distribution technology can be found in commercial equipment with the Unicable trademark from FTA Communications Technologies. Unicable uses an integrated software and hardware solution that allows Unicable-certified DVRs and receivers to multiplex selected programming when using Unicable LNB or multiswitching products.

The Unicable Interoperability Platform is open to companies designing and/or marketing satellite and other broadcast-related products. The platform is designed to facilitate the acceptance of Unicable-certified solutions in the consumer TV broadcast market.

Each satellite receiver in the installation has a dedicated user band of a bandwidth approximately the same as a transponder. The receiver requests a particular transponder frequency via a DiSEqC-compliant command. A mixer in the dish-end equipment (an LNB or distribution unit) converts the received signal to the correct user band IF centre frequency for that receiver.

The converted transponders of the various users are then combined, and sent via the single coaxial cable to the receivers. The combined signal is tapped or split to reach every user.

Silicon vendors have developed complex integrated circuits that greatly reduce the cost of implementing the single-cable distribution function. A channel-stacking switch IC is a multiple-input multiple-output device. It typically has N 1.2 GHz inputs that can be cascaded to additional chips as required (to expand output capacity). These inputs are fed into a large N-pole M-Throw switch that outputs to M mixers. Each mixer path then translates only the user requested transponder to a predetermined fixed frequency within the 950-2150 MHz band. This fixed frequency is unique for each tuner on the single cable output. Each tuner in the STB always stays at this fixed frequency while the CSS IC translates the user requested content down the cable to this exact frequency. This architecture requires no hardware change to the STB design. Communications protocol between the CSS IC and the STB is handled via the CENELEC EN50494 standard or proprietary systems.

Special LNBs have been developed for use in single-cable distribution systems. All four sub-bands of the Ku band (low frequency/horizontal polarity, high frequency/horizontal polarity, low frequency/vertical polarity, high frequency/vertical polarity) are received by a conventional front end, amplified and downconverted to the L-band, to be fed to a number of SatCR (Satellite Channel Router) – one for each user that can be connected - to further downconvert the required section of the received spectrum to centre on the user band IF frequency. The LNB further includes a combiner (i.e. reverse splitter) to merge the user bands and a microcontroller to receive the instructions as to which frequency is required by each user and control the SatCR chips.

Alternatively, a single-cable distribution system can use a conventional LNB feeding the four sub-bands to a separate SatCR receivers, as a substitute for a traditional multiswitch, that needs a dedicated coaxial cable for every receiver (or tuner) connected.

Unicable LNBs and SatCRs also usually include either a legacy mode of operation or a legacy output which provides conventional LNB IF for use with an installation of non-Unicable receivers.

A receiver required to operate in a single-cable distribution installation can be essentially conventional. It should be able to tune to the user channel (within the normal IF tuning range) and modulate the LNB power voltage with the 22 kHz signal required for issuing DiSEqC commands. It will then require only software modification to operate as a single-cable distribution receiver.

For correct operation, two-way splitters are required to feed the combined signal to each receiver. These allow bi-directional passage of both RF and DC signals, to provide for the passing of DiSEqC commands between the LNB and receiver(s).

As of March 2010, SES' Single Cable Distribution factsheet lists 88 receivers as supporting single-cable distribution technology although this list is not exhaustive. Several receivers for the HD+ German high definition platform broadcast from Astra 19.2°E are compatible with the SatCR system.

Existing communal integrated reception systems (IRS) often provide only one satellite feed to each household, preventing the use of dual-tuner DVRs. Upgrading the multiswitches and cabling to provide two or more feeds per household is usually both costly and invasive. However, individual households or sections of the system can be converted to SatCR distribution so that multiple tuners within a household can be fed via the single existing coaxial cable.

Equipment such as Inverto's Unicable Cascadable Switch can be connected to a conventional quattro LNB to provide a single SatCR output and a conventional LNB output. The four IF inputs from the Quattro LNB are looped through to outputs so the unit can be cascaded to further SatCR switches or to the existing multiswitches of the IRS, so an SatCR-enabled output is provided without replacing the existing LNB or affecting the provision for conventional receivers in other households served by the rest of the system.

Versions of the Unicable Switch to provide for four and eight tuners within a household are available, and to combine a digital terrestrial signal onto the SatCR-enabled output as well.

Global Invacom's SatCR Adaptor unit performs a similar function but is connected to the existing multiswitch outputs, to provide SatCR compatibility for one connection (one household) of an existing IRS.

The SatCR Adaptor connects to four outputs of an IRS multiswitch and provides a single SatCR output that is typically connected to the existing single coaxial cable to the household to be converted. A further four conventional IF outputs are provided to recover usage of the existing multiswitch outputs for other households. Within the SatCR enabled household, a splitter and power injector provides power to the SatCR Adaptor and splits the signal to feed the separate tuners connected.

Global Invacom developed the SatCR Adaptor in conjunction with BSkyB to enable flats and homes with single-feed distribution systems to fit Sky+ and Sky+ HD dual-tuner DVR receivers. While BSkyB SCR is slightly different to the CENELEC EN50494 standard most European SCR compatible multiswitches support both standard and BSkyB modes. Most Sky branded receivers including the Sky Q model can be used on SatCR systems by enabling a hidden option. Sky Italia receivers comply with the unicable standard.

An alternative approach to that provided by single-cable distribution of the signal from a single LNB to multiple receivers, or receivers with multiple tuners, is offered by the use of fibre satellite distribution using optical fibre. The high bandwidth of optical connections allows for the full satellite spectrum received at the dish to be accommodated on one fibre optic cable, which can be easily optically split to provide that full spectrum signal to a large number of receivers.

UK company Global Invacom (which also developed and markets SatCR single-cable distribution equipment) has developed a low cost system of fibre optic distribution suitable for domestic installations and small or medium commercial communal dish systems, with an optical output LNB, fibre cables, splitters, and converter units to return the optical signal to an electrical one compatible with legacy receivers.

The extremely low signal loss through fibre optic cables and complete elimination of interference and noise picked up by the cable mean that such a system can support very long cable runs between the dish and the converters in a widespread communal dish system, and a smaller dish can be used as the communal antenna.

Global Invacom won the Astra Innovation Contest run by satellite operator SES in 2007 for the proposal and initial development of optical fibre distribution systems for satellite TV.

This blog has been written to help you pick the correct LNB for your satellite dish. As there are numerous different types, makes and models,picking the wrong one could mean that your satellite TV will not work. In this blog I discuss what a LNB is, what a LNB does and different types of LNB that are used for different satellite TV services like Sky and Freesat. Let’s begin.

The LNB, which stands for Low Noise Block is the attachment at the end of the satellite dish in which the coaxial cables that feed your satellite receiver connect to. Each different type of LNB works in it’s own way but one of the main functions is to take the amplify the satellite broadcast signal and oscillate the signal to a lower frequency band that the coaxial cable can contain without excessively cable losses and the higher the frequency the greater the cable resistance and the quicker you will lose signal down the cable length. Most LNB’s, but not all of the oscillate the signal down to the satellite intermediate frequency band which is between 950Mhz to 2150Mhz.

There are lots of different types of “universal LNB” and contrary to as it sounds not all LNB’s are universal with all satellite dishes. As many don’t fit, like universal LNB’s used for Sky and Freesat MK4 style satellite dishes have a 38mm collar and nearly all other satellites dishes use an LNB with a 40mm collar. While this is not the end of the world when fitting a 38mm collar to a satellite dish which accepts a 40mm collar as a couple of wraps can around the collar can be enough to build the gap and create a secure fixing so that the LNB skew can be set correctly. Trying to do this the other way around however will not work as an LNB with a 40mm collar will not fit a 38mm collar holder.

Just to be clear I do not advise installing an LNB intended fora MK4 style Sky mini-dish onto a conventional type offset satellite dish as these are designed for an elliptical satellite dish and not a rounder dish. So, you should always purchase the correct LNB for best signal.

Universal LNB’s work by varying a supplied voltage form the satellite TV receiver which will switch the LNB between receiving horizontal and vertically polarised signals and by applying continuous 22Khz tone it switches the LNB between a high and low band. It does this as the bandwidth on transmission is greater than the bandwidth available on the coaxial cable, this means that at any one time there is only ¼ of the available satellite services on the coaxial cable at any one time. Therefore, you can’t just split a satellite signal off a universal LNB and why separate cables need to be installed with separate direct connections to the LNB, which I will explain more on shortly.

For your reference universal LNB’s oscillate signals within the KU satellite band which is 10.7Ghz to 12.75Ghz down to the IF satellite band, 950Mhz to 2150Mhz.

Low band signals oscillate the frequencies between 10.7Ghz-11.7Ghz by 9750Mhz

High band signal oscillates the frequencies between 11.7Ghz-12.75Ghz by 10600Mhz.

Here is a useful guide for remembering what satellite bands what DC voltage are and or 22Khz tone will need to be applied by the satellite receiver to receive them.

Vertical Low (VL) – 13V

Horizontal Low (HL) – 18V

Vertical High (VH) – 13V+22Khz

Horizontal High (HH) 18V+22Khz

There a several types of universal LNB, the most common ones between single LNB’s and Quad LNB’s. The difference between them all is the amount of outputs that the LNB itself has, this allows extra satellite receivers to be added for extra TV points and for the addition of satellite PVR’s that has recordable, pause, play and rewind TV services, like Sky+ and Freesat+that require two separate LNB connections to work properly.

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A single LNB has a single LNB connection for a coaxial cable to be connected. This will allow you connect a standard satellite receiver like a Sky or Freesat box. You can connect a Sky+ or Sky+HD box but the Sky box must be set to single feed mode and you will lose the ability to record one programme and watch another.

These are really not that common, as it makes as much sense if upgrading an LNB from a single to provide extra satellite connections or installing a satellite dish for the first time to just install a Quad LNB instead as this will future proof the installation further and allow for an additional two connections. The cost difference really isn’t that much, in fact Quad LNB’s are often cheaper due to them being installed and produced in greater volumes. A Dual LNB will allow for two separate satellite receivers to be connected or a one satellite PVR. If you have recently upgraded to Sky Q and see that your LNB has two connections only, please be aware that this is not a dual LNB but a Sky Q wideband LNB that works very differently.

Quad LNB’s are the most common LNB that are installed, and I personally install them as standard with all our standard Sky and Freesat installations.A Quad LNB will allow up to four satellite receivers to be connected, two PVR’s or one PVR and two standard satellite receivers. If more connections are required,then the LNB must be upgraded to an Octo LNB.

Octo LNB’s as I’m sure that you can guess have eight separate outputs allowing for eight coaxial cables to be connected and feeding up to 8 separate satellite receivers, four PVR’s or a combination of both. If you need more connections off a single satellite dish, unfortunately there are not any freely available LNB’s that allow for more connections. Instead a new approach must be adopted. This is the installation of a Quattro LNB, which is very different to a Quad LNB and a multi-switch amplifier. See our previous blog on how many TV's can be fed off one dish.

As both Sky & Freesat both use the same satellites for their services which are located at 28.2E, the exact same satellite dish and LNB can be used. This is perfect for when people wish to cancel their Sky subscriptions as they can continue to receive Freesat through the same satellite dish. If you’reusing a MK4 style Sky mini-dish satellite dish, then the LNB must have a 38mm collar and not a 40mm collar otherwise it won’t fit the LNB holder on the satellite dish. Adapter holders can be purchased to accept a 40mm collar but it is just one more thing to order in or keep in stock, so I advise ordering the correct LNB to begin with. I won’t go through all the different types again as these are single, Quad and Octo LNB’s.

You may or may not be aware that Sky Q uses a completely new style of LNB to traditional Sky and Freesat. I’m sure that they have their reasons for doing this but making it more difficult to cancel your Sky subscription is a reason as to cancel your subscription and go to Freesat will now involve changing the LNB on the satellite dish as well as the satellite receiver itself.

It’s good that I have already gone over how universal LNB’s work as it will help you understand the Sky Q LNB and how the Sky Q LNB is different to a universal LNB. Sky Q LNB’s have two separate cable inputs like a dual LNB but they work very differently. One cable is connected to a vertical output and the other a horizontal output. There is not switching of the LNB between horizontal and polarised signals as both the cables are carrying different services. This means when using a Sky Q wideband LNB that the Sky Q box must be connected with two cables must be connected to receive all the services and channels. There are ways of connecting a Sky Q box with a single cable as I mention later on the blog.

For the sharpest among you may be wondering how come all the same services can be fitted onto the two cables without the need for a high and low band oscillator? This is because the LNB uses greater frequency range than universal LNB’s do, this is between 300Mhz-2340Mhz meaning that it steals bandwidth which used to be reserved for TV aerial signals meaning that now switching at the LNB is necessary. This however does present big problems with diplexed TV and satellite systems and communal IRS systems as the Sky Q and TV aerial signals can no longer be combined onto the same cable.

A common and very welcome additional is that of hybrid LNB’s. These are a combination of the wideband LNB used for Sky Q and Quad LNB’s used for normal Sky and Freesat. This means that a single satellite dish can be used to connect a Sky+HD or Freesat box in one room and a Sky Q box in another and this allows us to future proof the satellite dish installation as much as possible and give greater flexibility to our customers. Hybrid LNB’s come with 6 outputs and not all hybrid LNB’s are the same. Some allow either a Sky Q or normal Sky/Freesat box to connect to every single output of the LNB and others have 2 wideband outputs and 4 universal outputs. The latter meaning that if you need to make sure that the cables that feed each satellite receiver corroborate with the connections on the LNB otherwise it will not work.

Although this type of LNB can be used for numerous satellite TV systems abroad, the only reason you would typically install this LNB type in the UK is for Sky Q, so this section has been written with this in mind.

A dSCR or dCSS LNB will allow a Sky Q box to be connected on a single feed which is helpful for when extra cables can not for any reason be installed between your satellite dish and Sky Q box. When you do this, you must change the LNB setting to ‘SCR’ mode with the settings menu on the Sky Q box. There is not switching on the LNB again, it instead looks for the frequency of the transponder for the channel that the satellite receiver has requested and oscillates it to the lowest available frequency. This allows for multiple programmes to be recorded at the same time without the need for extra satellite LNB connections,like is required with universal LNB’s.

The LNB oscillates down to the Intermediate frequency band which begins at 950Mhz and means that a terrestrial aerial signal can be combined onto the same cable making it the LNB of choice for diplexed TV/ Sat systems that are not using a multi-switch amplifier. dSCR technology is what is used with Sky Q compatible communal systems.

There is another dSCR Quad LNB on the market, which has one SCR output for connecting a Sky Q box onto a single feed mode and 3 traditional universal LNB outputs for connecting normal Sky or Freesat boxes.

When you install a communal IRS TV system, traditional LNB’s can’t be used as the amount of connections required is usually far greater than available on an Octo LNB. For this reason, a new approach must be adopted, and this is done via a Quattro LNB and multi-switch amplifiers. This blog isn’t about the installation of communal TV systems, so I won’t go into great detail here.

Although a Quattro and Quad LNB both have 4 outputs, a Quattro LNB differs in the sense that it supplies the four satellite bands separately over the four cables whereas a Quad LNB switches between them all of all the cables.This means that when installing a Quattro LNB, it can’t be connected directly to a satellite receiver. It must be connected to a multi-switch amplifier with separate VL, VH, HL and HH inputs where the switching instead takes place and the cables must not be mixed from the LNB and the input of the amplifier. By using this concept only four cables need to be installed between the satellite dish and multi-switch amplifier concept can be extended to serve hundreds of satellite TV points.

As there is switching from the LNB, providing you’re using a splitter that is both DC passing and capable of serving the satellite IF band frequencies, the signals can be split between multi-switch amplifiers. Just remember that you will need four separate splitters or a splitter with four separate inputs.

A Monoblock LNB is an LNB with two separate feedhorns and is effectively two separate LNB’s combined into one with a 6 degree separation,making it perfect for combined Astra 1 (19.2E) and Hotbird (13E) installations.A Monoblock LNB designed for use with 80cm satellite dishes or larger for signal reception.  The LNB has one cable output for connecting to a diESqC compatible satellite receiver that can be setup to be able to switch between the different LNB signal inputs.

You may have come across the term “high gain” LNB.  To understand this, it’s best to think of the LNB as the first stage of amplification. As satellite signals are beamed down to earth is very low strength one of the main roles of the LNB is amplify the signal. Most LNB’s are around 50dB gain but some models, High Gain LNB’s may be around 60dB gain or more.

These LNB’s are intended for use with long satellite cable runs where the cable resistance could cause loss of signal. It’s not a good idea to install these in situations with short cable runs as you could overload the satellite receiver and cause poor TV reception.

There are load more different types of LNB, like LNB’s used for fibre installations or iLNB’s used for some satellite broadband installations and I may update this blog at a later date but I’m not going to go into them here at this time. As always is you have any LNB or satellite related questions please LEAVE A COMMENT in the blog comment section below. Please DO NOT CALL OUR TELEPHONE LINES and please DO NOT E-MAIL us, we simply do not have the facility to deal with all the questions we get asked. I certainly do not have the time to speak on the phone and I do not give out my mobile phone telephone number as is regularly requested. That being said, I respond to blog comments as this gives me a central location to deal with all the questions and everyone reading the blog gets the benefit of the question asked and the answer given.