Glossary Terms Beginning L

0-9 : A : B : C : D : E : F : G : H : I : J : K : L : M

N : O : P : Q : R : S : T : U : V : W : X : Y : Z

LAN: Local area network (computers).
Latency: Delay through a compression process.
Launcher: Generic term for the feedhorn; vehicle – typically a rocket – used to carry a satellite into orbit.
Layer: MPEG group of audio coding algorithms.
L-band: In SNG terms, the frequency band 1.0-2.0 GHz.
Leasing: The rental of satellite capacity for a fixed term, typically one week to five years.
Left-hand circular polarization: See Circular polarization.
LEO: Low Earth orbit: below 5000 km.
LES: Land earth station (fixed); ground station; INMARSAT ground station.
Level: In MPEG, the level defines the image resolution and luminance sampling rate, the number of video and audio layers supported for scaleable profiles, and the maximum bit-rate per profile.
Licence: Formal authority permitting radio transmissions, usually incurring a fee.
Linear polarization: Geometric plane in which the electromagnetic signals are transmitted. Linear polarization is divided into vertical (Y) and horizontal (X) polarization.
Line-up: Period of time before the beginning of a transmission when operational technical parameters are checked and confirmed with satellite control centre.
Link budget: Calculation to ascertain the performance of a complete satellite link system.
Lip-synch error: Where the audio is out of synchronism with the video – commonly seen on compressed transmissions due to system errors.
Live shot: Short live transmission, typically for a brief news update.
Live stand-up: See Stand-up.
LNA: Low noise amplifier.
LNB: See Low noise block-downconverter.
Look-angle: Azimuth and elevation angles that an uplink or downlink has to be orientated along to point towards the desired satellite.
Loopback; Lookback: Ability at the uplink to receive its own signal downlinked from the satellite for verification.
Lossless: Compression process that creates a perfect copy of the original signal when it is decompressed at the end of the signal chain.
Lossy: Compression process that relies on the fact that the human eye and ear can tolerate some loss of information yet still perceive that a picture or sound is of good or adequate quality.
Low-noise amplifier: LNA: pre-amplifier between the antenna and the earth station receiver, located as near the antenna as possible for maximum effectiveness, usually attached directly to the antenna receive port. The LNA is especially designed to contribute the least amount of thermal noise to the received signal.
Low-noise block downconverter: LNB: combination of a low-noise amplifier and downconverter built into one device attached to the feed; it amplifies the weak signal from the satellite and frequency shifts it down from Ku-band (or C-band) to L-band, as required at the input to the satellite receiver.
Luminance: Brightness of a video picture.