All You Need To Know about Satcom (Satellite Communications) Modems

Satcom Modems are devices used to establish data modulation and demodulation used with a BUC, LNB and dish using a communications satellite as a relay.

What is a Satellite Modem?

A modem is an electronic device that performs two basic functions – Modulation of a digital input to a microwave signal and its demodulation, which is the reverse process. “Modem” is a word meaning a combination of modulator and demodulator. If a modem performs only a demodulation function (receive only), with no modulator, the satellite can only allow downloaddata received from the satellite. This makes them satellite receive-only modems, and satcom modems can be used for satellite Internet access, for example. With sitcom modems, the uploaded data can transfer through a conventional PSTN modem or an ADSL modem, for example.

Function of a Satellite Modem

A satellite Modem requires other equipment to create a satellite link. It works with satellite antennas and frequency converters. An upconverter converts the IF frequency to a suitable microwave frequency via an amplifier, feed and dish for transmission to a satellite.


The Digital Video Broadcasting- Satellite –Second Generation (DVB-S2) is a special modulation and coding standard and encapsulation used for digital television broadcasting, a development of the widely popular DVB-S system as a part of the DVB project. The DVB-S2 improves the DVB-S and finds use in the standard and HDTV broadcast services. The standard is also widely used in internet access and data content distribution. DVB-S2x is an extension of this, allowing 5% (and others) roll off for tighter packing of multiple carriers in the satellite transponder, and higher order MODCODs (modulation and coding) for example.

The Need for DVB-S2

With growing advancement in the various satellite signal properties, and the introduction of the HDTV and new video codecs using advanced compression techniques defined in H.264 (MPEG-4 AVC) and H.265, the older standard was not designed with the necessary protocols to handle the newer video formats.

DVB-S2 modulator uses a powerful coding and modulation scheme based on the LDPC code and a Variable Coding and Modulation (VCM) and Adaptive Coding Modulation (ACM) that allows optimizing the transmission in high rain fade conditions that would otherwise seriously degrade the signal and received picture quality etc.

Thus, a satcom modem is a special device used for satellite modulation and demodulation for TV and digital signal transmission. The DVB-S2/x is a coding and modulation standard that accommodates the growing needs for the transmission of new video standards, like ultra high definition (4X) and 3D, via compression systems defined in h.264 and 265 etc.