Satellite television receiver

Inner workings of a digital satellite receiver

Personal computers that are equipped with an internal or external satellite receiver tuner also count among the satellite receivers.

A satellite television receiver (often also satellite receiver , engl. "Receiver" for "receiver") is a device of entertainment electronics, with the television and radio programs by broadcasting satellite via a parabolic antenna can be received. Image and sound signals are forwarded from the satellite receiver to the corresponding output devices (e.g. television ). Compared to terrestrial reception via antenna, considerably more programs can be received. In contrast to reception via cable television , there is no separate connection fee for access to the transmission medium.

Working principle

A satellite receiver converts the signals received from the Low Noise (Block) Converter (LNB / LNC) (low-noise signal converter) into the frequency range of 950–2150 MHz and then converts them into a video signal that can be played on a television. Usually it also takes over the power supply of the LNB by supplying it with what is known as a remote feed voltage via the receiving cable .

LNB control

When receiving all frequencies available in a satellite position, the problem arises that four intermediate frequency (IF) bands from 950 to 2150 MHz are available, but only one frequency band can be transmitted to the receiver via a coaxial antenna line.

In the early days of satellite reception, two antenna cables were therefore laid to the receiver in order to receive two polarization levels, so a receiver absolutely required two IF inputs. So-called polarization rotors brought a simplification, using a separately laid control line to the LNB in the LNB feed to select the desired SAT level via a small rotor or an electromagnet; a receiver requires special control outputs for this.

With the advent of inexpensive reception systems in Europe, the industry was looking for more practical solutions for their satellite reception systems, which are now also being sold in hardware stores. Using a so-called Marconi LNB, a change between the two SAT IF levels supplied by the LNB was implemented using different remote feed voltages of 14/18 volts, which in turn made the use of new satellite receivers necessary, which, however, quickly fell in price due to the corresponding quantities. A remote feed voltage of 14 volts corresponded to the reception of the vertical polarization plane, a voltage of 18 volts to the horizontal plane.

A further expansion brought the use of the 11.7-12.75 GHz frequency range, which was formerly only used for telecommunications services and direct broadcasting satellites (DBS) , which meant two additional frequency ranges to be received by the receiver; Switching to these third and fourth reception levels was achieved by superimposing the remote feed voltage with a 22 kHz frequency. A satellite receiver was now able to switch between all four polarization and frequency levels supplied by a satellite using the remote feed control signals (14/18 volts, 22 kHz signal on / off). To switch to other satellites, however, it was still necessary to rotate the entire satellite dish using an elaborate rotating system control ( polar mount ).

DiSEqC

In order to enable switching to other satellites without a rotating system, Philips developed the (Digital Satellite Equipment Control) DiSEqC protocol, and the satellite operator Eutelsat developed the specification for an extension of the 22 kHz control signal through pulse modulation, known as the DiSEqC protocol. Philips then sold the rights to Eutelsat.

The DiSEqC protocol is available in versions 1.0, 1.1 and 1.2. Although there should be downward compatibility, DVB-S receivers with DiSEqC 1.2 are seldom compatible with DiSEqC 1.1 and are therefore only suitable for multifeed to a limited extent, they can control a maximum of 4 LNBs, while 1.1 allows up to 64 LNBs. When purchasing the receiver for the use of more than 4 LNBs, it should therefore be ensured that DiSEqC 1.1 is expressly stated in the technical data.

Types

Most satellite receivers are external add-on devices ( set-top boxes ). The advantage of this solution is the low price due to mass production. A theoretical disadvantage is that you need two remote controls (for TV and satellite receiver). In practice, you no longer need the television remote control. The SAT receiver switches the television on and off. The volume control is done by changing the level at the analog output or runs anyway via the hi-fi system and is regulated there.
Almost all current television sets have tuners that can receive DVB-C, T and T2, S and S2 .
There are also receivers with a built-in hard disk drive . You can record programs directly on the hard drive and, if necessary, transfer them to a PC via a USB or network interface . B. burn to DVD. Such receivers also enable time-shifted television ; the broadcast can, for. B. during a phone call , can be interrupted, then you can simply continue looking at this point.
Almost every television has USB ports for connecting mass storage devices.
Many devices from the middle price range have twin tuners. This allows you to watch two different programs at the same time, watch one and record the other, or record two programs. This requires the connection of two coaxial cables.
Additional information can be loaded with receivers that are capable of XBMC or Kodi . This means that there are expansion options through plugins that can be downloaded and installed. Internet platforms such as YouTube or ARD media libraries can be used using Kodi .

Digital satellite receivers

Digital satellite receivers are also called digital receivers . They receive digitally coded television signals and mostly also digitally coded radio signals.

Analog satellite receivers

First analog consumer satellite receiver 1986 from Grundig STR-200 (OEM Kathrein UFD 08) Household direct reception of the early Eutelsat satellites, primarily Eutelsat 13 degrees east

Analog television programs have not been broadcast via satellite since 2012. After a total of 23 years, the analog PAL broadcast on the Astra satellite system ended on April 30, 2012 with the analog switch-off .

technology

An analog receiver could be connected to all types of LNB , including the so-called universal LNB, which receives the entire Ku-band from 10.7 to 12.75 GHz, with transmission above 11.7 GHz mainly digital.

history

Rupert Murdoch , the Australian-American media entrepreneur, was the first customer of the then still young satellite company SES Astra . As early as 1989 he decided to broadcast his TV programs in the conventional PAL television standard . With this simple, inexpensive and widely available reception technology, he gained rapid growth for himself and the private satellite operator Astra and thus the decisive market advantage.

PAL successfully asserted itself against the partially digital broadcasting standard D2-MAC . D2-MAC was a development of the postal monopoly of public broadcasters and the equipment industry, for direct satellite reception via the TV-SAT satellite. D2-MAC had a limited distribution and a short lifetime.

Different frequency information

The frequency lists always contain the five-digit or six-digit downlink frequency (the frequency with which the satellite transmits). In addition there is the polarization and, in the case of digital programs, the symbol rate and the error correction, FEC for short.

Because high line losses would only allow the signals to be transmitted over a few meters in this high frequency range, these signals are already converted into a lower frequency range in the LNB. For this purpose, the received signal is mixed with the LOF ( local oscillator frequency ) in the LNB in order to obtain the satellite intermediate frequency (Sat-IF), which is in the frequency range between 950 and 2150 MHz. This is received by the satellite receiver.

Some analog and practically all digital receivers now show the five-digit downlink frequency in the frequency settings to make it easier for the user to find a station. Others, especially older analog receivers, show the four-digit satellite IF. This is calculated from the downlink frequency minus the LOF.

The LOF is 9.75 GHz for the low band and 10.6 GHz for the high band.

Example digital:

ARD-Das Erste auf ASTRA 1H:
11836,5 MHz (= Downlink-Frequenz) Polarisation: horizontal, Symbolrate 27500 FEC 3/4 laut Frequenzliste,
Sat-ZF: 11836,5-10600 = 1236,5 Sat-ZF

Example analog (switched off):

RTL auf ASTRA 1F:
11229 MHz (= Downlink-Frequenz) Polarisation: vertikal laut Frequenzliste,
Sat-ZF: 11229-9750 = 1479 Sat-ZF

Very old analog LNBs (before approx. 1995) had a LOF of 10 GHz, with such an LNB the SAT-IF is displayed as "lower" by 250 MHz.

11229-10000 = 1229 Sat-ZF

The SAT IF is therefore always 250 MHz higher with newer LNBs.

Encryption

Satellite programs can be encrypted (coded) or unencrypted (uncoded) by the broadcaster. To receive encrypted satellite programs, an access authorization system is required at the satellite receiver.

Receivers, which due to their construction can only receive unencrypted satellite programs, are marketed with the attribute “Free to Air”.
Receivers that are marketed with the attribute “CI” have a “ Common Interface ”, a PCMCIA compatible slot into which a so-called Conditional Access Module can be inserted. This contains all the hardware necessary for decoding, so a wide variety of encryption standards can be supported by such a satellite receiver.
Receivers that are marketed with an “ HD + ” attribute have a special “ Common Interface ”. This "HD +" module cannot be replaced by a "CI" module and only supports the HD + encryption standard.
Receiver with a built-in decoder module. Such devices only support this one or more specified decoding standards.

Some pay TV operators do not allow their encryption standard to be sold via conditional access modules , as they fear that the CI interface represents a security gap. For reception they require satellite receivers with a permanently installed decryption module, which means that CI receivers cannot receive such programs despite the common interface.