L band is a fequency range between 390MHz and 1.55GHz which is used for satellite communications and for terrestrial communications between satellite equipment.

The high frequencies utilized by C band, Ku band, and Ka band would suffer from high signal loss when transported over a copper coax cable such as an Intra-Facility Link.

An LNB is used to convert these higher frequency bands to L band, which can be transmitted over the IFL and processed by the IDU.

Some satellites transmit on L band, such as GPS satellites.