Landsat

An eary resources technology satellite.

L-Band

The frequency range from 0.5 to 1.5 GHz. Also used to refer to the 950 to 1450MHz used for mobile communications.

Latitude

The distance, expressed in degrees, from the Earth's equator to points north or south. The equator is assigned a value of 0 degrees; North and South poles are 90 degrees.

Lay

The length measured along the axis of a wire or cable required for a single strand (in stranded wire) or conductor (in cable) to make one complete turn about the axis of the conductor or cable.

Leased Line

A dedicated circuit typically supplied by the telephone company.

LED

Light emitting diode. Type of semiconductor that lights up when activated by voltage.

LEO

Low Earth Orbit.

LE0sat

Proposed mobile satellite systems using LEO.

LHCP (or LCP)

Left-Hand Circuir Polarization.

Line Amplifier

An amplifier in a transmission line that boosts the strength of a signal.

Line Rotation

Type of videoscrambling.

Line Splitter

An active or passive device that divides a signal into two or more signals containing all the original information. A passive splitter feeds an attenuated version of the input signal to the output ports. An active splitter amplifiers the inputs signal to overcome the splitter loss.

Link Margin

The extent (in dB) by which normal working (or clear sky) C/NR exceeds threshold CINR, or other value at which reception is deemed unusable.

Link Budget

The calculation of power and noise levels between transmitter and receiver (uplink or downlink), taking account of all gain and loss factors, to yield operating values of CII and C/NR, margin above threshold, and ultimate SINR or BER.

LNA

Low-Noise Amplifier.

LNF

A combination of a feed, automatic polarizer and low noise amplifier in a common package.

Local Oscillator

A device used to supply a stable single frequency to an upconverter or a downconverter. The local oscillator signal is mixed with the carrier wave to change its frequency.

Longitude

The distance in degrees east or west of the prime meridian, located at zero degrees.

Longitudinal Shield

A tape shield, flat or corrugated, applied longi- tudinally with the axis of the conductor or cable.

LOS

Line of Sight.

LOS (1)

Loss of Signal.

Loss

Energy dissipated without accomplishing useful work.

Low Noise Amplifier (LNA)

This is the preamplifier between the antenna and the earth station receiver. For maximum effectiveness, it must be located as near the antenna as possible, and is 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)

A low noise microwave amplifier and converter which downconverts a block or range of frequencies at once to an intermediate frequency range, typically 950 to 1450 MHz or 950 to 1750 MHz.

Low Power Satellite

Satellite with transponder RF power below about 30 watts.

Low Noise Converter (LNC)

An LNA and a conventional box. This device converts one channel at a time. Channel selection is controlled by the satellite receiver. The typical IF for LNCs is 70 MHz.

Low Loss Dielectric

An insulating material that has a relatively low dielectric loss, such as polyethylene or Teflon.

LPF

Low Pass Filter.

LPTs

Low-power transmitters used to broadcast terestrial signals over a small area.

Luminance

Light and shade information in a video signal.