What is VSAT?

Very Small Aperture Terminal

     VSAT is a term widely used in the satellite industry to describe an earth station that is installed on the ground to receive communications from a satellite or to communicate with other ground stations by transmitting to and receiving from satellite spacecraft. The ground station may be used only for reception, but is typically capable of both receiving and transmitting. Major components of a VSAT are generally grouped in two categories, ODU (outdoor unit) and IDU (indoor unit).

ODU - Out Door Unit
     The ODU, so named because the components reside outdoors, includes; the antenna (typically ranging in size from 2.4 meters down to as small as 50cm in diameter), equipped with a feed system capable of receiving and transmitting, a microwave radio, also known as a "BUC" Block-Up-Converter, and an LNB (low noise block down converter) used to convert the signal gathered by the feed.
     Transmit Radios (BUC's) are available for use in C, Ku, or Ka frequency bands and are sold by wattage capability. A complicated calculation called a "Link Budget" is performed by the satellite operator to determine both the size of the antenna and how much power (wattage) will be required to complete the transmission link between the ground station and the satellite. Transmit Radios are sometimes combined with the LNB's which are used as part of the receiving operation. The resulting combination is called a "transceiver" and saves some integration time during the installation process. T1 thruput, 27.5-Mb/s burst rate, 30-GHz uplink, 20-GHz downlink.
     IDU - Indoor Unit
     The indoor unit is typically composed of a single unit called a modem. A satellite modem is different than a telephone modem, and is used to convert the data, video, or voice generated by the customer application for transmission over satellite. The modem takes the signals from your computer, phone or other device and changes them so they can be sent to the ODU which transmits them out to the satellite and eventually to other ground stations.

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