Editing Satellite modem (section)

== Satellite link ==
{{Main|Satellite link}}

A satellite modem is not the only device needed to establish a communication channel. Other equipment that is essential for creating a satellite link include [[satellite antenna]]s and frequency converters.

Data to be transmitted are transferred to a modem from [[data terminal equipment]] (e.g. a [[computer]]). The modem usually has [[intermediate frequency]] (IF) output (that is, 50-200 MHz), however, sometimes the signal is modulated directly to [[L band]]. In most cases, frequency has to be converted using an [[Block upconverter|upconverter]] before amplification and transmission.

A modulated signal is a sequence of ''symbols'', pieces of data represented by a corresponding signal state, e.g. a bit or a few bits, depending upon the [[modulation]] scheme being used. Recovering a symbol clock (making a local symbol clock generator synchronous with the remote one) is one of the most important tasks of a demodulator.

Similarly, a signal received from a satellite is firstly [[downconverter|downconverted]] (this is done by a [[Low-noise block converter]] - LNB), then demodulated by a modem, and at last handled by data terminal equipment. The LNB is usually powered by the modem through the signal cable with 13 or 18 V [[Direct current|DC]].