Terrestrial transmission
Terrestrial transmission (from Latin: terra , earth, terrestrial = ground-based, land-based) refers to radio or television transmission from ground-based radio transmitters to receivers with house or indoor antennas , as well as portable devices and car radios . The term is younger than the technology itself and serves to distinguish it from newer transmission technologies such as satellite television , cable television and the Internet .
In terrestrial transmission, image or sound data are usually transmitted via VHF (ultrashort waves ) and digital audio broadcasting (DAB). For pure radio broadcasting, short wave (KW), medium wave (MW) or long wave (LW) are also used.
Electromagnetic waves behave more and more like light with increasing frequency. Characteristics here are the very weak diffraction behind the viewing horizon of a transmitter and behind hilltops. The radio horizon is therefore hardly larger than the horizon for visual connections at high frequencies . It is therefore necessary to install the transmitting antenna as high as possible and at particularly exposed points in order to achieve sufficient coverage of a larger area. Primarily protruding peaks with high antenna supports such as concrete towers or tubular steel masts are used here. These locations represent so-called basic network transmitters . They receive the program to be broadcast via radio link , underground cable, satellite or ball reception and then broadcast it with a high transmission power (> approx. 1 kW ). However, with basic network transmitters alone, especially on the high frequencies of television in band IV / V, it is not possible to achieve almost full coverage of the population. The field strength of the transmitter is too low mainly in valleys or reflections ( multi-path reception ) occur on larger objects such as slopes or buildings. In such cases, converters ( filling transmitters ) were often installed in the past . These are usually located on a hill in the area to be supplied, receive the signal from the basic network transmitter, convert it to a different frequency and then radiate it, usually directed with low power, into the target area.
In television, the classic terrestrial transmission has been largely replaced by satellite and cable television , but is gaining importance again through the transmission of digital data in DVB-T .
From March 29, 2017, DVB-T was switched off in many parts of Germany and switched to DVB-T2 . Further regions in Germany will follow in spring 2018. Suitable receivers are required for DVB-T2, as DVB-T2 is not compatible with DVB-T.
See also
Individual evidence
- ↑ Terrestrial. In: ITWissen.info. Retrieved October 25, 2019 .