Troposcatter
Troposcatter , also known as tropospheric radio , is a form of over-the-horizon directional radio in which the radio waves emitted , especially decimeter waves and microwaves , are scattered back at the troposphere .
This enables ranges of around 800 km which, due to the curvature of the earth, cannot be achieved with conventional radio links, as these require a line of sight between the terminals.
The troposphere radio has largely been replaced or supplemented by satellite communication , but is much cheaper than this, especially at low data rates.
General
The scattering of the radio waves takes place on local inhomogeneities of the refractive index as well as on haze and particles at a height of up to about 5 km. Accordingly, the directional antennas for sending and receiving are aligned almost horizontally. The majority of the radio waves emitted reach space unused, only a small part is scattered back to earth. The volume participating in the scattering is decisive for the strength of the received signal, namely that in which the transmit antenna and the receive antenna bundle cross each other. Therefore, multipath reception naturally occurs , so high data rates cannot be achieved.
Because of the low backscattering of the signals, high transmission powers and / or directional antennas are required for Troposcatter . Long-distance troposphere scatter connections are under certain circumstances more secure and more reliable than shortwave connections and cheaper than directional radio due to the lack of intermediate stations.
The tropospheric overreach , which can be observed particularly in the ultra-short wave range ( VHF band I , band II and band III ), does not belong to the category of tropospheric radio . They are based on the weather-dependent diffraction or refraction effects and only occur in inversion weather conditions .
application
The Troposcatter system TRC-170 transmits with a klystron with only 1.5 kW between 4.4 and 5 GHz via parabolic antennas . It has a range of up to 240 km.
Before the establishment of communications satellites, the White Alice Communications System in Alaska or the military communications links with the Texas Towers off the east coast of the United States were used for long-range communications.
The “BARS” tropospheric communication system installed in the Warsaw Pact states was also based on this effect.
British oil rigs used troposcatter links to land.
Another example is the radio link operated from 1959 to 1991 at 2.2 GHz between the Berlin-Schäferberg telecommunications tower (so-called Richtunkstelle Berlin 3) and the radio relay station Torfhaus in the Upper Harz (distance 190 km). For this purpose, 45 meter high free-standing steel lattice towers were erected at both locations, each of which carried two parabolic antennas, each 10 m in diameter, 15 m apart . Later they worked on the Berlin side with two 18 m Cassegrain parabolic antennas mounted 20 m one above the other on a newly erected concrete mast. The transmitters worked with traveling wave tubes and had an output power of 1 kW.
See also
Web links
Individual evidence
- ↑ a b https://www.electronics-notes.com/articles/antennas-propagation/tropospheric/troposcatter.php Ian Poole: Troposcatter communications & propagation , accessed on June 20, 2020
- ↑ Operation of the Tatical Troposphere Scatter Communications Terminals AN / TRC-170 (V). CECOM LAR, May 1, 2002, accessed April 20, 2020 .
- ↑ https://quizlet.com/191993178/e11-antrc-170-tropospheric-scatter-microwave-radio-terminal-flash-cards/
- ^ Günter Nitsche: The directional radio between West Berlin and West Germany - A bridge to the free world from 1948 to the fall of the Wall , August 2002. PDF; 340 kB, attachment with images , PDF; 4.9 MB, accessed August 18, 2019
- ↑ Pictures of the radio relay systems at Torfhaus and the radio relay station in Berlin-Schäferberg (July 1989 and July 1991) ( Memento from August 16, 2011 in the Internet Archive )