A Very Small Aperture Terminal (VSAT), is a two-way satellite ground station or a stabilized maritime Vsat antenna with a dish antenna that is smaller than 3 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Data rates typically range from 56 Kbit/s up to 4 Mbit/s. VSATs access satellites in geosynchronous orbit to relay data from small remote earth stations (terminals) to other terminals (in mesh configurations) or master earth station "hubs" (in star configurations).
VSATs are most commonly used to transmit narrowband data (point of sale transactions such as credit card, polling or RFID data; or SCADA), or broadband data (for the provision of Satellite Internet access to remote locations, VoIP or video). VSATs are also used for transportable, on-the-move (utilizing phased array antennas) or mobile maritime communications.
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History
The concept of the geostationary orbit was originated by Russian theorist Konstantin Tsiolkovsky, who wrote articles on space travel at the turn of the century. In the 1920s, Hermann Oberth and Herman Potocnik, aka Herman Noordung described an orbit at an altitude of 35,900 kilometers whose period exactly matched the earth's rotational period, making it appear to hover over a fixed point on the earth's equator.
Arthur C. Clarke contributed to the understanding of satellites through an article published in Wireless World in October 1945 titled "Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?". In this article, Clarke not only determines the orbital characteristics necessary for a geostationary orbit, but also discusses the frequencies and power needed for communications.
Live satellite communication was developed in the sixties by NASA, named Syncom 1-3. It transmitted live coverage of the 1964 Olympics in Japan to viewers in the US and Europe. Soon after, on April 6 1965 the first commercial satellite was launched into space, Intelsat I, nicknamed 'Early Bird'
The first commercial VSATs were C band (6 GHz) receive-only systems by Equatorial Communications using spread spectrum technology. More than 30,000 60 cm antenna systems were sold in the early 1980s. Equatorial later developed a C band (4/6 GHz) 2 way system using 1 m x 0.5 m antennas and sold about 10,000 units in 1984-85. In 1985, Schlumberger Oilfield Research co-developed the world's first Ku band (12–14 GHz) VSATs with Hughes Aerospace to provide portable network connectivity for oil field drilling and exploration units. Ku Band VSATs make up the vast majority of sites in use today for data or telephony applications. The largest VSAT network (more than 12,000 sites) was deployed by Spacenet and MCI for the US Postal Service.
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Future applications
Advances in technology have dramatically improved the price/performance equation of FSS (Fixed Service Satellite) over the past five years. New VSAT systems are coming online using Ka band technology that promise higher bandwidth rates for lower costs.
FSS satellite systems currently in orbit have a huge capacity with a relatively low price structure. FSS satellite systems provide various applications for subscribers, including: telephony, fax, television, high speed data communication services, Internet access, Satellite News Gathering (SNG), Digital Audio Broadcasting (DAB) and others. These systems are applicable for providing various high-quality services because they create efficient communication systems, both for residential and business users.
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___________________________________________________ Constituent parts of a VSAT configuration
• Antenna
• Block upconverter (BUC)
• Low-noise block converter (LNB)
• Orthomode transducer (OMT)
• Interfacility Link Cable (IFL)
• Indoor unit (IDU)
All the outdoor parts on the dish are collectively called the ODU (Outdoor Unit), i.e. OMT to split signal between BUC and LNB. The IDU is effectively a Modem, usually with Ethernet port and 2 x F-connectors for the coax to BUC(Transmit) and from LNB (Receive). The Astra2Connect has an all-in-one OMT/BUC/LNA that looks like a QUAD LNB in shape and size which mounts on a regular TV sat mount. As a consequence it is only 500 mW compared
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