Satellite television

With satellite radio or satellite television broadcast programs, in particular television programs via satellite to the receivers are transmitted.

In Central Europe -air and transmitted via satellite broadcast programs, for example, broadcast by the Astra or Eutelsat satellites. To receive satellite broadcasting a satellite dish with LNB and a satellite receiver is needed. Of the 34.83 million German households 17.5 million ( about 50%) have directly through individual aerial or a shared reception area with its own satellite receiver reception ( = direct satellite reception ).

• 3.1 Satellite Radio

History

In 1928 published the Austria - Hungarian space theorist Herman Potočnik geostationary position in a narrow strip above the equator, on which satellites 35,800 km altitude resting apparently. In the efforts to use this for broadcasting, in 1977 a worldwide broadcasting satellites plan was adopted at the World Radio Conference (WARC ) in Geneva. From 1 January 1979 was an agreement with a term of 15 years, which allotted each country five channels for television / radio to a satellite position. Share of each country with up to eight other countries (so satellites and ) The particular position should then. These satellites should then be positioned in the orbital position with a distance of 6 ° above the equator. A common satellite position ( 19 ° West TV - SAT), was assigned to Belgium, the Federal Republic of Germany, France, the Netherlands, Italy, Luxembourg, Austria and Switzerland.

The Federal Republic of Germany and France decided on 2 October 1979 in Bonn, a framework agreement to build two state-owned television direct satellite (TV - SAT), Luxembourg decided, however, for a non-state, private project (SES Astra).

In 1982, the " European Telecommunications Satellite Organization " ( "Eutelsat " ) in France was as an intergovernmental organization founded with the goal of creating a satellite- based telecommunications infrastructure for Europe. Eutelsat's satellites were (then equipped only with relatively low transmission power ) is not planned for Direct TV reception, but should serve as a feeder to terrestrial broadcasters and cable television systems. 1985, however, new low-cost, low-noise HEMT LNBs came on the market, which initially ambitious hobbyists enabled the direct reception of Eutelsat ECS 1 ( orbital position 13 degrees East ) at a reasonable cost and in private households. This appeared a few years earlier, at least in Europe still to be unrealistic, as the following published in 1975 assessment shows:

" The final step in the use of satellites is used in the direct care of a sufficiently strong station in a geostationary satellite with directional radiation on the earth for reception by suitable house antennas. This fascinating technology is still problematic and is close to the limit of the physical- technical possibilities. It requires extra effort at the receiver and raises legal problems because of Mitbestrahlung of neighboring areas on. But they will be tested, and you will also be used on success, but probably first in other parts of the world outside Europe. "

The direct reception was initially controversial. Thus, the individual satellite reception equipment at the authority had to be notified, which then rose an ongoing fee.

SES Astra finally helped with their medium -power direct broadcast satellite satellite television in Europe on a large scale breakthrough. In the early 1990s urged the German Federal Post Office, Astra LNB yet with an additional filter at the entrance to equip, " as this can cause its own terrestrial microwave links could be disturbed ." This fear was later found to be unfounded; possibly this request was also only a protectionist measure.

From 1994, a digital transmission (DVB -S) was parallel to the analog satellite television initially for Pay TV services introduced. Driving force behind this were pay-TV channels such as DF1. Leo Kirch went here by propagating its digital d-box high financial risks, DVB- S was definitely popular, finally, by the quality and capacity advantages, which ultimately led to the so-called final analogue switch-off on 30 April 2012.

On 19 August 2005, the German took on the satellite Astra 19.2 ° East the so-called radio transponders in operation. Since then, all German public radio programs of ARD are handy to receive a very high quality. It broadcasts in DVB -S standard. Satellite radio is in Europe ( currently) not a substitute for terrestrial FM sound broadcasting, since only very few private radio broadcasters can be found. Local or regional private broadcasters who are often leaders in their coverage areas, consider the very expensive Europe-wide broadcasts as uneconomical. Often transfer program providers their programs via satellite for the signal feeding the FM station. The situation is different in sparsely populated areas. In the U.S., the company XM Satellite Radio and Sirius Radio reception via satellite offer. The fees are under $ 15 / month. In cities where tall buildings shade the signals used partially pseudolite signal broadcast.

Technical Basics

Transmission

Since the carrier - to-noise ratio ( CNR) is very low in satellite transmissions - typically 10 to 18 dB - ( the transmitted information signal is only slightly above the noise floor between the transmitter and receiver), usually with analog transmission signal by frequency modulation is more resistant to interference made; in digital transmission only modulation method such as 2- PSK, 4 -PSK to 8 -PSK are possible. Current satellite using 4 -PSK and thus a symbol rate of 2 bits per symbol.

The spectral distribution of a frequency modulated composite video signal with analog transmission is somewhat unfavorable, so that in weak signal conditions, although images with low color saturation still can be well transmitted images with intense shades of red, however, to so-called " little fish " tend (black and white smears ).

Developed in the 1980s, analog D2-MAC method that works without color sub-carrier, in this respect is much more robust, even if that was not the primary design goal. Especially in northern countries, it found great popularity.

The reception problems could be completely overcome by the error correction method of the all-digital television technology DVB -S.

Spectrum

The individual transmitters are equipped with a channel spacing of 29.5 MHz as at Astra 1F, lined up. The tapes of the horizontal and vertical polarization are shifted by half the channel spacing. In the low -band ( 10.7 to 11.9 GHz) are mainly housed analog transmitter whose signal is modulated with FM. Nevertheless, there are individual digital signals (DVB -S), for example, modulated with 8 -PSK. The picture shows a photograph of the spectrum ( after the LNB, horizontal polarization ) from 1453 to 1653 MHz. Of the 7 covered channels 5 analog ( colored blue ), and to see two digital (red).

Time delay of the signals emitted

Since the signals of television stations must be sent to the satellite and back to the audience, there is a delay between 239 ms ( the equator) and 270 ms ( 70 latitude) compared to the transmitted signal.

This delay, which is also the analogue reception is increased with the digital reception by establishing ad-

• MPEG-2 or MPEG- 4 encoding: There are reordered images over other images differences are formed.
• Multiplexing transmitters and buffering: intercepting data rates tips, dividing the available data rate between a plurality of transmitters of a transponder.

Usual delay times for digital satellite reception are therefore one to five seconds that you immediately noticed when you simultaneously via digital satellite and a transmission route (eg, radio or cable reception without satellite feeds or analog via satellite) receives the significantly shorter delays has.

Sending and receiving

The radio and television signals are transmitted from an uplink station on uplink frequencies 12.75 - 18.1 GHz sent to the satellite - 13.25 GHz, 13.75 to 14.5 GHz and 17.3. Own transmitter unit with parabolic antenna is used for each transponder. These are located in uplink stations that either the satellite operators are performing there for its customers the uplink or the customers ( broadcasters ) lead with its own facilities through the uplink. This is particularly worthwhile for large broadcasters occupying several transponders because they are so save the transmission path for uplink station of the satellite operator.

The satellite transmits to the downlink frequency ( 11.7 to 12.95 GHz ) at the receiving antennas.

Basically, the conversion of the signals with the satellite reception in the controllable active part of the dish (LNB ) is carried out. Since a coaxial cable has a very high attenuation at the high satellite frequencies in the SHF range of the LNB converts the signals to lower SAT - IF frequencies (950-2150 MHz).

Through various wiring methods (eg satellite block distribution or single-cable ) signals to the consumer ( satellite receiver) are forwarded.

Satellite Radio

Satellite radio, the radio reception through a satellite, there is independently as digital radio or as a " lodger " in the satellite television.

In Ku band you need to receive a satellite dish, LNB and satellite receiver. L-band antenna and a built- in receiver of sight range to the satellite. Via satellite, hundreds of German and European channels are free and free -air. However, there are also some pay - radio providers that offer different transmitters with specific genres to subscribe.

• Satellite Radio as a lodger in the satellite television Radio via DVB -S: Satellite radio via digital TV
• Astra Digital Radio ( transmission set since 30 April 2012)
• Radio (never transfer since 30 April 2012) to analog sound subcarriers in analog satellite television

• Standalone Satellite Radio WorldSpace in Europe and Asia
• Digital Satellite Radio ( DSR), set transfer in Germany.
• Satellite Digital Audio Radio Services ( SDARS - Satellite radio), pay satellite radio especially in the U.S.