The LNB (Low Noise Block Down-Converter) is part of the receive chain of your VSAT. Located on the feed horn, the LNB converts the satellite signal that was reflected off of the satellite antenna’s reflector from C-Band into an L-Band signal. The L-Band signal is in the frequency range of 950 to 1750 MHz and is considered more manageable. This is partially due to the fact that the transmission of the lower frequency signal can be more reliable when using a coaxial cable than is the case when higher frequency C-Band signals are transmitted of on this type of cable. Virtually all new satellite routers today use L-Band inputs. An LNB can be identified by its F-type output connector. 

You can also view the placement of the LNB (Low Noise Block Down-Converter) below in the VSAT Installation Manual Components Chapter: