Satellite broadcast reception system
A satellite broadcasting receiving system is a home automation means for reception of satellite broadcasting .
The purpose of such a receiving system is to operate several parties (or several satellite broadcast receivers , "satellite receivers") via a single parabolic antenna (as a community antenna ). There are various technical solutions, some of which are manufacturer-dependent, for operating such a shared antenna.
Sat block distribution
The best solution in terms of program variety and future security is to distribute the satellite signal with a multi-switch and a star-shaped antenna cabling ( satellite block distribution ). This usually requires complex adaptation or rewiring of the antenna system, which is not always possible. Each receiver (second / third television, TWIN receiver) needs a separate line from the multi-switch, so several cables may be required for each apartment.
The polarization level is selected for satellite block distribution by changing the level of the remote feed voltage that is applied between the inner conductor and the outer shield of the coaxial cable. 14 V signal here vertically, 18 V horizontally. Modern DVB-S receivers reduce an LNB supply voltage to an energy-saving 12 volts using technology that is compatible with the DiSEqC protocol throughout. The polarization level is then selected exclusively using DiSEqC commands.
The complete satellite frequency range (10.7–12.75 GHz = 2 GHz) now does not fit into the IF band (950–2150 MHz = 1.2 GHz). It is therefore divided into two areas: the low band with 10.7–11.9 GHz and the high band with 11.55–12.75 GHz. The LNBs of older satellite systems often only convert the low band. Digital signals, on the other hand, were mainly to be found in the (newer) high band up to 12.75 GHz. Digital (including HD) programs are now also set in the low band, since the analog transmission of programs has been discontinued.
That is why digital satellite systems require a universal LNB that converts either the upper or lower band into the SAT IF frequency band. The selection of the reception frequency band for such an LNB, to which a receiver can be connected directly, is made using a further switching criterion, a modulated 22 kHz audio frequency signal. If this signal is issued by the receiver, the LNB switches to the high band; if it is missing, it falls back to the low band.
The designation "digitally suitable" for the LNB is misleading, since every LNB converts both analog and digital signals into the corresponding frequencies. It stems from the fact that the older low band mainly contained analog signals, while the later added high band was primarily used for digital programs.
In the course of the displacement of analog channels in favor of digital broadcasting technology, digital broadcasts can increasingly also be received in the low-band. The term "digitally suitable" for an LNB only means that it can also convert the frequencies or channels of the high band and has nothing to do with any analog or digital electronics in the LNB.
Thus, every new LNB in the Ku band uses four different reception levels (two frequency bands on two polarization levels). One of the four levels is always switched to the coaxial cable by the DVB-S receiver using control signals.
If several satellites with several LNBs are to be received, receivers with so-called DiSEqC protocol and corresponding DiSEqC switches are required.
Single cable system
Another solution is to distribute only those satellite frequencies that actually contain interesting TV channels. The antenna reception system reduces the various Astra or Eutelsat satellite levels to a single one, which can then be distributed in a residential complex as easily as a cable television signal (but in a higher frequency range 950–2200 MHz).
A single-cable system deliberately restricts reception to a single IF band (950–2150 MHz = 1.2 GHz). A pre-selection usually selects the Astra-High band with 11.75–12.75 GHz horizontal as the base frequency band; this already enables the reception of approx. 300 German-language radio and television programs. Other transponders of other reception levels are copied into this band by frequency converters, but this is optional due to the concentration of German-language satellite programs on Astra-Horizontal-High. Since an available frequency band is limited in frequency range, the programs required for reception must be selected, as in cable television.
The resulting RF signal can then be distributed without remote feed and control signals in any structured antenna system in large residential complexes via a single coaxial cable. To do this, the antenna cabling must be adapted for higher frequencies. Most of the time, there is no need to replace the coaxial cable, but generally all antenna sockets and RF distributors have to be replaced, and every television needs its own digital receiver . Each receiver can receive around 200 television, 200 radio and HDTV programs on one antenna cable (H104 single-cable system). Single-cable systems can be operated in combination with DVB-T and DVB-C to receive local television programs. A combination with interactive cable television services is also possible. However, in some cases there may be restrictions on the reception quality, which means that some stations can no longer be received. Furthermore, some areas in the upper frequency band are not supported correctly.
Unicable
This relatively new system is the second best solution, but significantly more expensive than a conventional single-cable system. With the Unicable system, several receivers can be supplied with the full range of programs of a satellite (e.g. Astra) on one cable (including HDTV). A distinction is made between Unicable LNB and Unicable multiswitch solutions. In the latter case, even larger residential complexes can be converted to satellite reception by cascading several Unicable matrices.
A transponder to be received is selected with a Unicable distribution using DiSEqC control signals, which are transmitted between the inner conductor and the outer shield of the coaxial cable as a superimposition of the remote supply voltage to the LNB or the multiswitch. Single-cable devices according to Cenelec EN 50594 are often named after the brand name Unicable from FTA Communications SARL.
This technology is based on a European standard EN 50494 issued in 2004 and an SCR chip (Satellite Channel Router), which extends the DiSEqC command set of the receiver and enables various programs to be selected via a cable. Many of today's digital satellite receivers already support the new command set. In principle, all receivers that meet the EN 50494 standard can be operated. Conversely, these SCR receivers can be operated on all conventional satellite systems. Such systems are e.g. B. from the company Kathrein (EXR matrices) or the company Technisat (TechniRouter).
Instead of a complete IF band (950–2150 MHz = 1.2 GHz), the channel router contained in the Unicable LNB or Unicable multiswitch only provides a section of the respective band that contains the desired frequency (transponder). This is converted to the user band assigned to the respective receiver and fed to the coaxial cable. Several EN 50494-compatible DVB-S receivers can be operated on the coaxial cable, which enables simple cabling in line topography (series connection of the antenna sockets). Unicable enables an unlimited range of programs and is particularly suitable for retrofitting existing apartments with satellite broadcasting. It must be checked whether the existing coaxial cables are suitable for satellites, then the existing cable can be used in an apartment with antenna sockets connected in series. Only the antenna sockets in the apartment have to be replaced. New cabling is necessary at the location of the previous feed (mostly basement).
Several DVB-S receivers can be operated in one apartment. It is advantageous, if not absolutely necessary, to have at least one separate line in each apartment. Each apartment can be connected to its own switchover matrix (e.g. EXR501 from Kathrein). This enables the connection of up to 4 single or two twin receivers per apartment. Different apartments cannot disturb each other in this way.
JESS (EN 50607 from 2013, also referred to as SCD2 or Unicable 2) is an extension of this process and allows the operation of up to 32 receivers on one cable line. A receiving device compatible with EN 50494 can in principle be made JESS-capable by means of a firmware update.
Canal preparation
With this solution, a head-end station can be used, which converts the satellite signal from a common parabolic antenna into a conventional television signal in the VHF and UHF range and enables the television set to be connected easily without an additional satellite receiver. However, with this analog channel processing there is only a limited range of programs because not all satellite channels have space in the conventional television band. The relatively high costs per TV channel implemented also stand in the way. In addition, the image quality suffers with every signal conversion; HDTV reception is not possible.
Cable network operators use this technology to supply up to tens of thousands of subscribers with television and radio programs, but today they are also switching to lossless DVB-C digital technology, which offers a variety of programs similar to satellites and HDTV.
In digital channel processing , selected television channels received via satellite are converted into a low-frequency, easy-to-distribute DVB-C signal using a complex technical process. Such a signal conversion is only economically viable for extensive antenna systems and largely corresponds to digital cable television. A DVB-C receiver is required for each television.
Feeding into a house network
In order to feed satellite television into the home network, a streaming server feeds the information as DVB-IPTV .
See also
Individual evidence
- ↑ Page 8 "The supply voltage is then only 12 volts at any time within the entire system": ( Memento of the original from January 31, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
