G

Gain

The amount of amplification of input to output power often expressed as a multiplicative factor or in decibels.

Gain-to-Noise Temperature Ratio (G/T)

The figure of merit of a dish and LNA. The higher the G/T, the better the reception capabilities of an earth station.

Geostationary Orbit

See Clarke Belt.

Ghosting

A term used to describe the appearance of multiple TV images that is usually caused by reception of a signal via two different paths.

GigaHertz (GHz)

1000 MHz or one billion cycles per second.

Global Beam

A footprint pattern used by communication satellites targeting nearly 40% of the earth's surface below. Many Intelsat satellites use global beams.

Ground Noise

Unwanted microwave signals generated from the warm ground and detected by a dish.

H

Hall Effect Sensor

A semiconductor device in which an output voltage is generated in response to the intensity of a magnetic field applied to a wire. In an actuator, the varying magnetic field is produced by the rotation of a permanent magnet past a thin wire. The pulses generated serve to count the number of rotations of the motor

Hardline

A low-loss coaxial cable that has a continuous hard metal shield instead of a conductive braid around the outer perimeter. This type of cable was used in the pioneer days of satellite television.

Headend

The portion of an SMATV or MMDS system where all desired signals are received and processed for subsequent distribution.

Heliax

A thick low-loss cable used at high frequencies; also known as hard-line.

Hertz

An abbreviation for the frequency measurement of one cycle per second. Named after Heinrich Hertz, the German scientist who first described the properties of radio waves.

High Definition Television (HDTV)

An innovative television format having approximately twice the number of scan lines in order to improve picture resolution and viewing quality.

High Power Amplifier (HPA)

An amplifier used to amplify the uplink signal. Horizontal Blanking Pulse - The pulse that occurs between each horizontal scan line in an analogue television signal and extinguishes the beam illumination during the retrace period.

Horizontal Sync Pulse

A 4.7 microsecond (in the PAL system) rectangular pulse riding on top of each horizontal blanking pulse. It synchronizes the horizontal scanning at the television set with that of the television camera.

HPA Room

The space where radio frequency systems reside. These include modulators, group delay equalizers, upconverters, high power amplifiers and combiner systems

Hum Bars

A form of interference seen as horizontal bars or black regions passing across the field of a television screen.

I

I Signal

One of the two color video signals which modulate the color subcarrier. It represents those colors ranging from reddish orange to cyan.

Impedance

The resistance to alternating current flow in an electrical circuit.

Impulse Pay-Per-View

Impulse pay-per-view (IPPV) is a feature of a decoder that allows an authorized subscriber to purchase a one-time scrambled program at will. IPPV shows are selected by a button on the decoder or its remote control unit.

Inclinometer

An instrument used to measure the angle of elevation to a satellite from the surface of the earth.

Integrated Decoder Access Control

IDAC Integrated Receiver Decoder - IRD - A satellite receiver and decoder contained in one case Interference - An undesired signal intercepted by a TVRO that causes video and/or audio distortion.

Insertion Loss

The amount of signal energy lost when a device is inserted into a communication line. Also known as <169>feed through<170> loss.

Integrated Smartcard Access Control

ISAC

Intelligent Work Station

IWS

Interactive Voice Response

IVR

Interlaced Scanning

A scanning technique to minimize picture flicker while conserving channel bandwidth. Even and odd numbered lines are scanned in separate fields both of which when combined paint one frame or complete picture.

Intermediate Frequency (IF)

A middle range frequency generated after downconversion in any electronic circuitry including a satellite receiver. The majority of all signal amplification, processing and filtering in a receiver occur in the IF range.

INTELSAT

The International Telecommunication Satellite Consortium, a body of countries working towards a common goal of improved worldwide satellite communications.

Isolator

A device that allows signals to pass unobstructed in one direction but which attenuates their strength in the reverse direction.

Isolation Loss

The amount of signal energy lost between two ports of a device. An example is the loss between the feed through port and the tap/drop of a top-off device.

K

Kelvin Degrees (K)

The temperature above absolute zero, the temperature at which all molecular motion stops, graduated in units the same size as degrees Celsius (<198>C). Absolute zero equals -273 <198>C or -459 <198>F.

Kilohertz (kHz)

One thousand cycles per second.

Ku-Band

The microwave frequency band between approximately 11 and 13 GHz used in satellite broadcasting.

L

Latitude

The measurement of a position on the surface of the earth north or south of the equator measured in degrees of angle.

Line Amplifier

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

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 amplifies the input signal to overcome the splitter loss.

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.

Low Noise Amplifier (LNA)

A device that receives and amplifies the weak satellite signal reflected by a dish via a feed. C-band LNAs typically have their noise characteristics quoted as noise temperatures rated in degrees Kelvin. Ku-band LNA noise characteristics are usually expressed as a noise figure in decibels.

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, 950 to 1750 MHz or 950 to 2050 MHz.

Low Noise Converter (LNC)

An LNA and a conventional downconverter housed in one weatherproof 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.