7E Communications
   

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.