Sat block distribution
A satellite block distribution (also referred to as SAT IF distribution ) is a frequently used variant of building cabling, in which a radio reception system enables several satellite receivers to be operated jointly on one or more satellite antennas . The main task is to distribute the signals supplied by the LNB (and possibly existing terrestrial antennas) to the individual participants. A satellite block distribution is characterized by the fact that each satellite receiver (e.g. digital receiver) is connected via its own antenna line. The cabling is structured in a star shape. Alternatives to this are the single-cable system and the improved Unicable variant .
Working principle
Modern television satellites receive signals from the ground station at the uplink frequency and convert them into a new downlink frequency using so-called transponders on board the satellite . At Astra , this downlink frequency is between 10.70 and 12.75 GHz. The signals are amplified in the transponders and then sent back to a specific area on the earth's surface via directional antennas. The geographical area in which the satellite signal can be received is called the coverage area . Due to their high frequency, these signals cannot penetrate obstacles such as trees, house walls and roofs, etc. Therefore, a clear view of the satellite is always necessary on the receiving system.
Signals with such high frequencies can not be optimally distributed in building cabling with normal coaxial cables , since the signal attenuation would be too high. This is why the received frequencies are first mixed down to a lower intermediate frequency range by the LNB . The entire frequency band from 10.70–12.75 GHz is not converted, but the band is divided into two roughly equal segments and converted into the same, lower IF band. The automatic switching of the LNB-internal mixing frequencies is controlled by the satellite receiver. The conversion of the very high transmission frequencies of the satellite transponder into a lower band reduces the losses due to the cable attenuation, which are very dependent on the frequency and the type of cable. Using a typical coaxial cable for antenna system construction at 10 GHz / 12 GHz instead of 1 GHz - 2 GHz would mean that hardly anything would arrive at the receiver that was previously received at the antenna. However, the implementation alone is not enough to provide a sufficient level for the satellite receiver. This is why the converter stage (mixer) is also followed by a powerful amplifier that delivers a sufficiently strong signal for the subsequent cable distribution. The LNB, which essentially consists of a small antenna, an input amplifier, a mixer, a line amplifier and a switchable oscillator per channel (horizontal / vertical) per level, is supplied with power and control signals via the coaxial cable.
Since the signals emitted by the satellite are polarized both horizontally and vertically , there are four possible switching states:
- Horizontal polarization, upper frequency range (high band) 11.70–12.75 GHz
- Horizontal polarization, lower frequency range (low band) 10.70–11.70 GHz
- Vertical polarization, upper frequency range (high band) 11.70–12.75 GHz
- Vertical polarization, lower frequency range (low band) 10.70–11.70 GHz
The receiving frequencies mixed down by the LNB are then passed on to the satellite receiver via an ordinary coaxial cable in the frequency range of 950–2,150 MHz . This downmixing usually takes place at 9.75 GHz in the low band and 10.6 GHz in the high band (called local oscillator frequency, or LOF for short). Since the local frequency range is 1,200 MHz, but the standard satellite blocks only use 1,000 (low band) or 1,050 MHz (high band), there is a range that is not used by the receiver as standard. However, you can set the limit between low and high band (called LOF switch) of 11.7 GHz as standard for many receivers and TV cards to a value between 11.55 and 11.9 GHz.
Switching between polarization and frequency range
Depending on which transmitter is to be received, the receiver needs a different polarization plane and / or a different frequency range (see the elongated diagram on the right). To switch over, the receiver transmits various control signals via the antenna cable to the LNB (or, if available, to the multi-switch):
The polarization level is switched by changing the level of the remote feed voltage that is applied between the inner conductor and the outer shield of the coaxial cable. 18 V signal horizontally , 14 V vertically .
The frequency range ( low band or high band ) is switched using a modulated 22 kHz audio frequency signal. If this signal is issued by the receiver, the LNB (or multi-switch) switches to high band . If it is missing, it falls back to the low band .
- Horizontal polarization, upper frequency range (high band): 18 V + 22 kHz
- Horizontal polarization, lower frequency range (low band): 18 V
- Vertical polarization, upper frequency range (high band): 14 V + 22 kHz
- Vertical polarization, lower frequency range (low band): 14 V
Here it becomes clear why it is not possible without restrictions to operate several satellite receivers on a single antenna line (e.g. with a distributor or through sockets): If, for example, one of the receivers outputs the 22 kHz signal, the LNB ( or multi-switch) the high band . Another receiver, which needs the low band at the moment , could then no longer receive anything. Exceptions are the frequencies between 11.55 and 11.9 GHz of the same polarization, which in principle can always be received, but require a situation-specific configuration if the hardware does not recognize this itself. The same applies to switching between the horizontal and vertical polarizations, only without exception . A parallel connection of several receivers is technically possible in principle, as long as you limit yourself to a common frequency band and one polarization level, since the tuners themselves function independently of one another. Due to its higher switching voltage, the horizontal polarization plane behaves “dominantly” compared to the vertical; A second receiver connected in parallel then only receives the transmitters with a horizontal polarization plane despite the "vertical" setting. Series connection is also possible if every device (except possibly the last) has a loop-through output (also RF Out). Which setting dominates depends on the hardware and cannot be said in general.
Practical to note and not to be confused:
- A quad LNB contains four connections. Each connection can be controlled to output one of the four possible reception areas. It is usually controlled via a satellite receiver or multiswitch. A single and a dual LNB can also output all four reception areas at each output if appropriately controlled by the satellite receiver. A Quattro Switch LNB , as it is often found in stores, corresponds to the Quad LNB, as it has an integrated multi-switch and thus has four connections, each of which can be controlled to reproduce one of the four reception areas.
- A Quattro LNB contains four connections. A predetermined reception area is output via each connection; it is not possible to control the assignment of a reception area to a connection during operation. If these four connections are connected to the inputs of an external multi-switch, then all satellite receivers connected to the outputs (e.g. 16, if there are 16 outputs on the multi-switch) can receive all four reception areas by appropriately controlling the multi-switch.
The connection of several receivers to a coaxial cable with an unlimited range of programs is now made possible by a unicable system.
DiSEqC
DiSEqC makes it possible to receive several satellites via one or more satellite antennas with one receiver. The following use cases are possible:
- Control of a motorized rotating satellite antenna for alignment to different satellites (only suitable for one receiver).
- Control of a switch (multi-switch), which is connected to different, permanently mounted LNBs, each of which receives different satellites (e.g. Astra Eutelsat receiving system; suitable for several receivers).
- In the case of newer reception systems, switching between low and high band as well as horizontal and vertical polarization in the LNB can be done using DiSEqC signals, as an alternative to switching voltage and 22 kHz signal.
- Use of special LNBs that loop through the satellite block intermediate frequency (IF) when they are not switched on themselves. A complete multiswitch logic is integrated in each LNB. Several such LNBs are cascaded in series; the desired frequency range and LNBs are then selected using a DiSEqC signal (only suitable for one receiver).
Structure of the wiring
The LNB located in the focal point of a parabolic reflector outputs a certain reception range (intermediate frequency range 950–2200 MHz) of the four transmission ranges transmitted per satellite in the satellite block distribution, depending on the control signal sent by the receiver. Because of the control signals and because an entire frequency block is always output from the LNB to the receiver, an exclusive coaxial line is required for each receiver (cabling in star topology ).
If more receivers are to be operated on a receiving system than an LNB offers, this is done by connecting a multi-switch . From the LNB to the multi-switch, typically four exclusive antenna lines are required for each satellite. After the multiswitch, cabling should again typically be implemented in star topology .
Unused outputs on the multiswitch or LNB are terminated with a 75 Ω terminating resistor. The use of antenna sockets is not absolutely necessary as long as no terrestrial or cable television signals are fed in. An IF line amplifier can be used for long coaxial lines. It should be noted that this must pass through a remote supply voltage without voltage drop and superimposed control signals.
In the case of very large systems, it may also be advisable to install small cascadable multiswitches for each floor in the stairwell or via distributors from the SAT master line directly in the apartment in order to flexibly receive the desired number of SAT signals from the LNBs per residential unit , exclusively for each connected SAT receiver input, to be able to provide in a short way. In this way, numerous different satellite positions can be made available to individual participants on request without the additional costs for the more complex DiSEqC-capable multiswitches having to be borne by all participants.
Multiswitch
A multi-switch is a component of a receiving system in satellite block distribution technology, which enables the joint operation of several satellite receivers on one satellite antenna . The main task is to distribute the signals supplied by the LNB to the individual satellite receivers. It is also used (depending on the design) to feed terrestrial or cable television signals into the antenna lines to the participants.
Differentiation between analog and digital reception technology
The designation "digital" or "analog" multiswitch or LNB is technically incorrect. Correctly it should read : " Analog tape - " or " Analog and digital tape -" suitable multi-switch or LNB
When receiving the initially still analog channels in the low band, switching between the frequency ranges (high or low band) was initially not necessary. It was only switched between horizontal and vertical polarization.
Multiswitches and LNBs suitable for analog band can also provide digital and HDTV transmitters if they broadcast in the low band. The first 200 MHz of the high band, in which z. B. The first SD can be received if the limit to the high band (LOF switch) is increased to 11.9 GHz so that the receiver does not expect that they have been mixed down with the local oscillator frequency of the high band. Conversely, multi-switches and LNBs designated as digital can always provide the analogue transmitters.
The term "digital" was invented by the manufacturers of the high-band-compatible multiswitches and LNBs because on the Astra satellite system, which dominated the market in Central Europe, at the beginning of digital television, all digital channels in the high band were broadcast first, the analog channels in the low band. Numerous digital channels and HDTV channels are now also broadcasting in the low band. In the course of the shutdown of the analogue SAT channels, the low band will be used more for digital and HDTV channels in the future. For this reason, new satellite receivers should preferably be used as so-called HD receivers, as these generally also enable reception of the digital DVB-S standard .
Basically, you can tell the difference between the analog and digital multiswitches by the number of inputs per LNB (two for analog, four for digital). Analog multiswitches are now hardly to be found in stores, since analog receivers can also be operated on digital multiswitches. Analog multiswitches are therefore only connected to the LNB via two connection cables ; usually twin or dual LNBs are used. The use of a digitally compatible Quattro LNB is also possible; then only the two low-band outputs of the LNB are connected, the high-band connections remain unused.
With the universal LNBs, the additional 22 kHz signal only switches the oscillator frequency from 9.75 to 10.6 GHz to receive the high band, but nothing changes in the basic functionality of an LNB, the frequency conversion.
Further functions of the multiswitch
Since the multiswitch is usually installed in the attic, it makes sense to feed the signals from any terrestrial antenna systems that may still be present into the house cabling, for example for receiving VHF radio or DVB-T . Most multiswitches therefore have an additional input for the terrestrial signals. An antenna splitter or a so-called multi-range amplifier with the desired antennas is preferably connected here. Signals from the cable television network can also be fed in in the same way .
The multi-switch transmits these signals to the antenna socket through the same cable as the satellite signals. With a suitable antenna socket (so-called 3-hole socket), the different signals can again be used separately from one another.
When using services in cable television that require return channel capability (e.g. cable modem for Internet or telephone), the return channel capability of the multiswitch is also required.
Multiswitch LNBs
These special LNBs have an integrated multi-switch with four or eight outputs. They are usually referred to as Quad-LNB or Quattro-Switch-LNB (four outputs) or Octo-LNB (eight outputs); the designation varies depending on the manufacturer and is not necessarily uniform. Here the receivers can be connected directly to the LNB without an additional multi-switch. Monoblock LNBs for cross-eyed installations ( multifeed ) can also have integrated multi-switches. Here you can operate a receiver at each output; the receivers work independently, d. H. everyone can receive analog and digital TV programs without affecting the reception of the other receiver.
Such multi-switch LNBs are useful for receiving systems with very few participants. Another multi-switch can be connected to such an LNB, provided that it outputs 14 and 18 V each and (in the case of a digital device) the 22 kHz signal at its LNB inputs. Otherwise the LNB would only deliver the vertical low band at all outputs. The use of a Quattro LNB (without an integrated multi-switch) is, however, preferable. Better quality and easier expandability can be expected with the Quattro LNB and external multiswitch, since the electronics are less tightly built (crosstalk), are not exposed to the weather and the multiswitch usually has its own sufficient power supply.
Multiswitch for several satellites
It is possible to distribute the signals of several satellites with a multi-switch. The multiswitch has additional LNB connections (i.e. four more inputs for each additional Quattro LNB). In this case, the receiver itself controls switching to the respective LNBs using an additional digital DiSEqC signal. It is irrelevant whether the second LNB is installed on the same satellite dish ( multifeed ) or on a second mirror. One LNB is required for each satellite. The use of motor-controlled rotating antennas for several satellites is not sensible in communal reception systems with multi-switches.
Cascadable multiswitches
These are multi-switches that on the one hand distribute at least the four reception areas of an LNB to individual subscribers, on the other hand pass the signal delivered to its inputs and make this available unchanged at other outputs to the next cascadable multi-switch. Cascadable multiswitches are used in large buildings such as apartment blocks in order to be able to flexibly offer and distribute the desired connections per residential unit over a short distance.
The typical installation consists of a satellite antenna and a cascadable multi-switch on each floor. From this the conductors lead to the apartments on the floor and four coaxial cables to the multi-switch for the next floor, etc. Manufacturers such as Spaun, Arcon, GTN, Kreiling and Kathrein offer such systems.
If an additional satellite is required on only one floor, then cascadable multiswitches with eight inputs can also be used. Alternatively, a DiSEqC relay can also be used to switch to other multi-switches that can also be cascaded or directly to the LNBs.
Trade names for multiswitches
The type of multiswitch often includes two digits, e.g. B. 5/8. The first digit indicates the number of inputs from the LNB, the second the number of outputs to the receiver. If the number of inputs is odd, the multiswitch also has a terrestrial input.
Some examples:
- Multiswitch 3/8: 2 inputs from an LNB, 1 input for terrestrial antenna, 8 outputs to 8 receivers (analog multiswitch)
- Multiswitch 5/4: 4 inputs from an LNB, 1 input for terrestrial antenna, 4 outputs to 4 receivers
- Multiswitch 5/8: 4 inputs from an LNB, 1 input for terrestrial antenna, 8 outputs to 8 receivers
- Multiswitch 9/8: 4 inputs from the first LNB, 4 inputs from the second LNB, 1 input for terrestrial antenna, 8 outputs to 8 receivers
- Multiswitch 5/16: 4 inputs from an LNB, 1 input for terrestrial antenna, 16 outputs to 16 receivers
Historical development
The European satellite operator SES Astra enabled a certain EIRP of 50 dBW , but with 16 KU transponders, by resorting to tried and tested PAL technology and a modern, slim satellite concept ( GE Astra Electronics Astra 1A , only an EIRP of 50 dBW , but already on December 11, 1988 ) Diversity of programs, in contrast to the later failed TV-SAT system. The use of the tried and tested technology of telecommunication satellites also included the concept for efficient frequency use by dividing the 16 transponders into a horizontal and a vertical polarization level (frequency blocks). The receiver had to receive the two polarization planes separately in order to obtain the full Astra program variety (for the first time 16 TV programs with one satellite); joint transmission of both satellite IF blocks over a single coaxial cable (as with terrestrial PAL or cable television) was not possible due to the frequency range, which was equally occupied in both polarization levels. The industry soon developed a switching concept called Marconi LNB for easy-to-install reception systems, which switched between the two polarization levels by changing the remote supply voltage (14/18 V). This technology was used in multi-switches with several outputs to operate several satellite receivers on a common mirror.
A further development of this 14/18 volt V / H switching technology, controlled by supply voltage, was made necessary by the use of the DFS-Kopernikus satellite of the Deutsche Bundespost, which was actually intended for telecommunications, for direct television reception (in competition with Astra). Switching to the so-called high band (12.5–12.75 GHz) was achieved by superimposing a 22 KHz control signal on the LNB supply voltage, making four IF bands available for satellite reception for the first time. This concept enabled a later expansion of the high band to include the DBS frequencies (11.70–12.5 GHz) previously reserved for TV-SAT to 11.70–12.75 GHz.
Another further development for switching to other satellites brought the DiSEqC system by Philips and Eutelsat .
A technology called “14/18 Volt, 22 kHz Tone Burst, DiSEqC” always provides the receiver (satellite receiver) with an entire reception frequency block (950–2300 MHz), from which the term satellite block distribution is derived.
Advantages and disadvantages
advantages
If satellite reception is planned generously from the outset when building a property, there are clear advantages with satellite IF distribution (e.g. compared to cable TV). On the one hand, the variety of programs with satellite reception is significantly higher (especially with multi-satellite reception). For example, a few hundred free TV programs can be received with digital satellite reception, while only around 60 free TV programs can be received with digital cable reception (as of 2009). Furthermore, some free HDTV programs can already be received via various satellites, while DVB-C reception in some federal states currently only offers paid HDTV offers.
After all, satellite reception is currently free, so that the initial investment in a satellite reception system (especially in apartment buildings) pays for itself after a few years.
The satellite block distribution by means of multi-switches is easy and flexible to implement and can also be combined with cable television. The reception of several satellite positions and satellite antenna is also possible with this system easily and relatively inexpensively for several participants.
disadvantage
The technique of satellite block IF distribution has arisen historically, from which a main disadvantage is derived: due to the practice of satellite block switching, only one DVB-S or DVB-S2 receiver can be connected to one antenna line. This causes a lot of cabling effort with little flexibility when connecting additional receivers. In contrast, connecting several DVB-C or DVB-T receivers to one antenna line has never been a problem, which is why satellite block distribution is seldom practiced in very large residential complexes to this day. Classic cable television often offers commercial landlords a number of advantages , especially in terms of service and the Internet .
Another disadvantage of a satellite block IF distribution is that the number of connection lines per apartment also indirectly determines the number of satellite receivers that can be operated in an apartment. In the planning phase of a satellite broadcast reception system, many are not aware that today there are several other satellite receivers per apartment (video recorder, kitchen TV, children's room, PC with DVB-S2 card, DVB-S radio reception on the hi-fi system) , connected and operated. For this reason, a satellite block distribution system cannot be compared with the convenience of linear signal distribution (cable TV connection or DVB-T).
Satellite cables can also be looped through or connected in parallel. Many satellite receivers and some DVB-S cards have a so-called loop-through output (also called loop out or RF out) for looping through. However, you have to agree on a switching state for this. At the typical position of 19.2 ° East, almost all digital German channels are in standard quality (SDTV) in the horizontal high band (see the elongated diagram on the right). Primarily Phoenix, arte, Einsfestival, EinsPlus, tagesschau24 from the horizontal low band as well as DMAX, Sport1, Tele 5, Comedy Central and the alternative program slot from arte from the vertical high band are missing. With HDTV, many channels are in the horizontal low band. Here 3sat, KiKA and zdfinfo from the vertical low band as well as Tele 5, WDR and the complete sky package from the horizontal high band are missing. Some receivers and TV applications offer the user the option of adjusting the usual 11.7 GHz limit between low and high band (values between 11.55 and 11.9 GHz are standard-compliant) so that more stations are in the desired band .
If an additional connection or a satellite is required in only one apartment, then cascadable multiswitches with 8 inputs can also be used. Alternatively, a DiSEqC relay can be used to switch to multi-switches or directly to the LNB. However, these switching variants are always associated with considerable additional planning effort, especially in communal systems.
Alternatives
Unicable
Since 2004, however, there has been another standard CENELEC EN50494 for operating up to 8 satellite receivers on a coaxial cable, which can receive the full range of programs of a satellite (e.g. ASTRA) independently of one another. This system is known under the name Unicable . If there is a separate cable in each apartment in existing apartment buildings, a cascade of several such unicable matrices can also be used to upgrade larger residential complexes to satellite reception at a relatively low cost without complex rewiring. To receive the satellite programs, however, a so-called unicable-capable satellite receiver is usually required. The performance of this system is also limited by the unicable matrices used compared to the satellite block distribution with several satellite positions. Also, due to the existing routing of the distributors and the coaxial cables, sometimes not all of the eight Unicable-capable satellite receivers can be operated at will.
Since 2014 there have also been Unicable II multiswitches standardized according to the SCR / CSS CENELEC EN50494 / EN50607 standard. These enable the connection of up to 32 receivers (tuners) via a common coaxial cable. The prerequisite, however, is that all connected devices can at least master the CENELEC protocol EN50494. If more than 8 tuners are supplied, then the other devices must also be able to use CENELEC protocol EN50607. A Quattro LNB is usually used as the low-noise signal converter . But there are also multi-switches to which you can connect wideband LNB. This has the advantage that you can distribute the channels from 2 satellites with just one multiswitch. If more than 32 tuners are to be supplied, then several such multi-switches can be hung one behind the other. The multiswitches can also be cascaded using a combiner. According to the CENELEC EN50607 standard, up to 64 satellites can be received. In 2017, however, only Unicable II multiswitches were on the market that could be programmed with up to 4 satellites. Another possibility with some multiswitches is the assignment of static SCR by programming. In static operation, up to 32 transponders are permanently assigned to the SCR (can also be from different satellites). This has the advantage that almost any number of tuners can be connected to one line and these tuners only have to be normal satuners. The disadvantage is that reception is limited to these 32 transponders.
Single cable systems
Another very simple alternative is the so-called single - cable system , with which many satellite receivers (although limited to approx. 200 satellite TV programs) can be operated on an existing coaxial cable. With this system, the complete range of the satellite operator cannot be used. If satellite transmitters change transponders, they may not be able to be received (or no longer) with the simple single-cable systems; it may then be possible to upgrade to a programmable single-cable system in the head-end station, which then causes additional costs.
Sat-over-IP technology
The Sat-over-IP technology ( Sat-IP for short , also SAT> IP ) is an alternative to the previous HF -based intermediate frequency distribution of DVB-S (2) signals using coaxial cables. With it, the satellite signals are made available digitally in an IP -based architecture for the reception and distribution of digital satellite signals via a local network . As with all other forms of transmission common for the Internet, SAT reception is not carried out via a conventional antenna connection socket, but via a conventional IP network access or via WLAN . Only TV receivers suitable for Sat-over-IP or other SAT> IP clients are required as receivers.
Thanks to the complete IP-based processing of the TV signals, there are no restrictions on cable lengths and forms of transmission due to the SAT intermediate frequency.
Quad / Octo LNB
Instead of a Quattro LNB with a downstream multi-switch, up to eight SAT receivers can be supplied independently of one another, provided that the SAT dish is connected
- Quad-LNB (for up to 4 receivers)
or a
- Octo-LNB (for up to 8 receivers)
is attached.
See also
- Parabolic antenna (TV)
- Low Noise Block Converter
- Multifeed
- Satellite receiver
- Antenna connector
- Sat-over-IP technology
Individual evidence
- ↑ SAT IF distribution. SES Astra , accessed April 22, 2017 .
- ↑ Website Unicableswitch from Inverto. Retrieved November 26, 2017 .
- ↑ Thomas Riegler: Expanding the satellite system. In: digitalfernsehen.de. June 26, 2015, accessed February 27, 2017 .