Glossary of Terms A-M

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22KHz tone The signal generated by a satellite receiver and relayed to an LNB to select the "high" local oscillator.
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Amplifier A circuit that increases the power or voltage of a signal.
Amplitude The strength or magnitude of a signal
Amplitude modulation (AM) A transmission system in which the modulating waveform is made to vary the carrier amplitude.
Analogue A mode of transmission of information. An analogue waveform has a physical similarity with the quantity it represents.
Aerial or Antennae A device used to transmit or receive radio waves.
Aspect ratio The ratio of width to height for a TV screen.
Astra The "trade" name for satellites operated by SES ("Societe Europeenne des Satellites").
Attenuator A passive device that decreases signal power.
Attenuation The loss in power of electromagnetic signals between transmission and reception points.
Azimuth A compass bearing east or west of true south
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Balun A balance-to-unbalance transformer (sometimes an integral part of an aerial) used to match an unbalanced coaxial cable to a balanced device such as an aerial dipole or receiver input.
Bandpass filter A circuit that passes a restricted band of frequencies. Unwanted lower and upper frequencies are attenuated.
Bandwidth The total range of frequencies occupied by a signal. It is normally measured between half-power points.
Baseband The band of frequencies containing information after demodulation.
Beamwidth An aerial acceptance angle measured between half- power points.
Bit A binary digit (a "1" or "0").
Bit error ratio (BER) A ratio of the number of errors in a data stream to the total number of data bits.
Bit rate The number of digital bits transmitted per second.
Blu-ray Disc (BD) Is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs.
Boltzmann's constant The relationship between the energy of a particle and its motion is related to its absolute temperature multiplied by Boltzmann's constant, which has the value of -228.6dB. This very small factor exerts a powerful influence on the effects of noise and thus on quality.
Boresight The principle centre axis of an aerial or dish antenna.
Bouquet A number of programmes grouped within a multiplex.
BSkyB British Sky Broadcasting.
Braid The interwoven outer conductive layer of coaxial cable made up of several bare conductors coming together to form a solid or nearly solid layer or shield. Braid is rated by percentage of coverage and by pixels per inch. Pixels per inch indicate the number of crossings of the braid in one inch of cable.
BSS (Bus. Satellite Services) The band of frequencies 11.7-12.5GHz
Byte A group of 8 digital "bits".
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C120 flange A standard mating flange for circular Ku band waveguides.
CAM "Conditional Access Module". Normally fits into the PCMCIA socket of a satellite receiver, to hold a viewing card.
Capacitance A energy storage device that is formed wherever an insulator separates two conductors between which a voltage difference exists. Capacitance is measured in "Farads".
Carrier-to-noise (C/N) ratio A ratio of the received carrier power to the noise power in a given bandwidth, in dBs.
Cascade amplifier A line-powered amplifier that also passes the powering voltage to its input terminals.
Cassegrain A dish with a paraboloid prime focus main reflector and a convex sub-reflector.
Catenary wire A supporting wire for an overhead coaxial cable between buildings or structures.
Cathode ray tube (CRT) An evacuated glass vessel in which an electron beam produces a luminous image on a fluorescent screen.
CATV Community (Cable) Antenna Television.
C band The band of frequencies 3.6-4.2GHz.
CCIR "International Radio Consultative Committee".
CCIR impairment scale A 5 point scale of subjective analogue picture quality.
CCTV "Closed Circuit TeleVision"
CDM (construction/design/maint) Regulations concerning activities on a building site that must be complied with in certain circumstances.
Ceefax The teletext service of the BBC.
Channel The frequency band over which information (data, audio TV) is relayed.
Characteristic impedance The impedance in ohms of a device in the path of a communications signal
Circuit protective conductor A cable used to earth a mains power socket.
Circular polarity Electromagnetic waves whose electric field uniformly rotates along the signal path. Facing an incoming wave, clockwise rotation is called Right-Hand Circular (RHCP) and anti-clockwise rotation is called Left-Hand Circular Polarisation (LHCP).
Chrominance The hue and saturation of a colour. A chrominance signal carries the colour information.
Cinemascope A widescreen TV picture format, usually 16:9.
Cladding The outer coating of a glass fibre which provides a reflective surface.
Clarke belt The circular orbital belt 35 786 Km above the equator, at which all satellites appear to be stationary.
Cliff effect The effect of a digital picture suddenly blocking or freezing when the signal parameters degrade below a certain level.
Cluster amplifiers A series of filters/channel amplifiers tuned to amplify and pass a single cluster of analogue and/or digital terrestrial TV channels.
Cluster filter A series of filters, each tuned to attenuate a single cluster of analogue and/or digital terrestrial TV channels.
Coaxial cable An internal conductor surrounded by an insulating dielectric and one or two outer conducting screens..
Co-channel interference Interference on a single terrestrial TV channel resulting from signals on the same TV channel.
COFDM "Coded Orthogonal Frequency Division Multiplex". The method of modulation used for digital terrestrial broadcasts in Britain.
Composite baseband The raw demodulator analogue output before filtering, clamping and decoding.
Composite video A complete video signal, including luminance, sync. and colour information but not audio or data sub-carriers.
Constellation diagram A representation of the amplitude and phase of each bit of information in a digital symbol.
Consumer Electronic Control (CEC) CEC is an HDMI feature designed to allow the user to command and control up-to 15 CEC-enabled devices, that are connected through HDMI, by using only one of their remote controls (for example by controlling a television set, set-top box, and DVD player using only the remote control of the TV). CEC also allows for individual CEC-enabled devices to command and control each other without user intervention.
Cross colour A TV picture defect that results in swirling coloured patterns.
Cross luminance A TV picture defect that results in brightness variations and colour changes.
Cross modulation A form of interference caused by the modulation of one or more carriers affecting that of another signal. It can be caused by non-linearity or the overloading of an amplifier, or signal imbalances.
Cross-polarisation Signals of the opposite polarity to those being received.
Cross-polar discrimination The ratio of the amplitude of the wanted polarity to the unwanted one.
Cross talk Interference between two or more video or audio baseband signals.
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D2MAC A satellite analogue encryption technique whereby the luminance and chrominance components of a video signal are transmitted seqentially. Used by European broadcasters.
DAB "Digital Audio Broadcasting".
dBi The gain of an aerial relative to an isotropic source. This is normally 2.15dB more than the gain relative to that of a half-wave dipole.
dBm dB power relative to a 1 milliwatt standard.
DBS (Direct Broadcast Satellite) The band of frequencies 11.7-12.5 GHz
dBw dB power relative to 1 watt.
DC pass The ability of a circuit element (usually a splitter, diplexer or outlet plate) to pass dc voltages – this is necessary to power a masthead amplifier or LNB, or to pass remote control signals.
DCT (Discrete Cosine Transform) An MPEG technique that converts pixel values from the time domain to the frequency domain and "quantises" the values to compress the data bandwidth.
Decibel (dB) The logarithmic ratio of voltage or power levels, used to indicate the gains or losses of signals.
Declination offset The adjustment angle of a polar mount between the polar axis and the plane of a satellite dish used to aim at the geosynchronous arc. Increases from zero with latitude away from the equator.
De-emphasis A reduction of the higher frequency parts of a signal to neutralise the effect of pre-emphasis.
Deep Colour Deep color is a gamut comprising a billion or more colors. The xvYCC, sRGB, and YCbCr color spaces can be used with deep color systems.
Demodulator A device that extracts the baseband signal from a transmitted carrier wave.
Depolarisation The twisting of the polarisation of a radio wave as it travels through the atmosphere.
Deviation The maximum amount the carrier frequency is shifted by the modulating signal.
Dielectric Insulating material used to separate the conductors of a coaxial cable or the conducting circuits of a capacitor.
Dielectric plate A device for insertion into a feedhorn to convert circularly polarised signals to a linear polarity.
Digibox A generic name for a satellite or terrestrial digital receiver.
Direct-Stream Digital DSD is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media that are used for the Super Audio CD (SACD).
Diplexer A frequency-conscious device for combining or splitting signals in different frequency bands. A diplexer has a lower insertion loss than the equivalent splitter.
Dipole Normally a single aerial element half a wavelength long with cable connections at its centre point.
Director element An element mounted on an aerial boom in front of the dipole that modifies the aerial characteristics.
Discriminator A type of circuit used to demodulate an FM signal.
DiSEqC "Digital Satellite Equipment Control". An extension of the 22 KHz concept to provide control of multiple devices.
Dolby True HD Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc and HD DVD. It is the successor to the AC-3 Dolby Digital surround sound codec which was used as the audio standard for DVDs
Down conductor A conductive link to an earth termination to provide lightning protection.
Down-conversion A reduction of a band of high frequencies to a lower band.
Downlink The transmission path from an orbiting satellite to a receiving dish.
Drip loop A loop formed in a coaxial cable so that water will drip off instead of penetrating apparatus or a structure.
Drop-in cable A coaxial cable linking each dwelling unit to the signal distribution network.
DSB (Double SideBand) A form of amplitude modulation where both the upper and lower sidebands (which result from modulation of the carrier by the signal) are transmitted.
DTH (Direct-to-home) Satellite transmissions intended for reception in homes.
DTS-HD Master Audio DTS-HD Master Audio is a lossless audio codec created by Digital Theater System. It was previously known as DTS++
DTT Digital Terrestrial Television.
DVB (Digital Video Broadcast) Definitions of the methods of digital signal modulation.
DVD-Audio Commonly abbreviated as DVD-A is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos.
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Earth bonding The connection of a system to an earth point
Earth station A ground-based transmitting or receiving satellite installation.
EBU European Broadcasting Union.
EIRP The power of a transmitter with reference to that of a point (isotropic) source.
EIT (Event Information Table) Programme data relating to events occurring within a digital multiplex.
Electromagnetic wave The technical name for a radio wave, so called because it comprises electric and magnetic fields moving in unison.
Elevation The vertical angle measured from the horizon up to a target satellite.
Encoding Converting a message to code eg when characters are stored in binary code. Often used to describe a process in which the form of an electronic signal is changed.
Encryption The process of hiding information or keys needed to unlock scrambled signals.
Energy dispersal A low frequency signal added to the baseband signal before modulation. Used to reduce the peak power per unit of bandwidth of an FM signal to reduce its interference potential.
EPG (Electronic Prog. Guide) A compilation of all the programmes available.
ESA European Space Agency.
Eutelsat European Telecommunications Satellite Organisation.
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F/D ratio A ratio of the focal length to the diameter of a dish.
FEC (Forward Error Correction) A10 A technique for improving the accuracy of data transmission. Excess bits are included in the outgoing data stream so that error correction can be applied by the receiver,
Feeder cable The main coaxial cable emanating from the head end equipment and connected to one or more spur distribution cables.
Feedhorn A device that collects microwave signals from the surface of a dish (located at the focal point).
Fibre optics The relay of signals on glass fibres using light waves.
Field One half of a complete TV picture or frame. There are 50 fields per second in a PAL system.
Filter A device used to pass or reject a specified range of frequencies. This normally comprises one or more tuned circuits.
Filter/leveller A series of filters with adjustable attenuation, each tuned to a single analogue terrestrial TV channel.
Flat screen display A TV screen using LCD or plasma display techniques instead of a cathode ray tube.
Flylead A plug-in lead to link together two domestic satellite or TV products.
FOB (Flush Outlet Box) A TV or satellite outlet designed for flush mounting on to a flush conduit or surface pattress box.
Focal length The distance from the reflective surface of a parabola to its focal point.
Focal point A point in front of a satellite dish to which all the reflected energy is focussed.
Folded dipole Two half-wave dipoles connected in parallel in order to modify the centre impedance.
Footprint The geographical area towards which a satellite downlink signal is directed. The contours indicate lines of equal signal strength.
Frame One complete TV picture, composed of two fields.
Frequency The number of oscillations per second of an electrical or electromagnetic signal, expressed in cycles/sec or Hertz
Frequency modulation (FM) A transmission system in which the modulating waveform is made to vary the carrier frequency.
Freznel zones Circular regions of an electromagnetic wave where the signals are in the same phase
Front-to-back ratio The ratio of the gain of an aerial in the forward direction to that in the reverse direction.
FSS (Fixed Satellite Service) The band of frequencies 10.7-11.7 GHz
Fused spur A mains electrical power supply outlet comprising a fuse and captive mains cable (but not including a power socket).
Fusion splice The low-loss glass fibre jointing technique using heat to join two fibres together.
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Gain The amplification of input to output power in dBs.
Geostationary orbit The circular orbital belt 35 786Km above the equator.
Galvanic isolator An in-line device to improve lightning protection and electrical safety by providing dc isolation between different parts of a cable network. Satellites in this belt appear to be stationary.
Galvanization Is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. Although galvanization can be done with electrochemical and electrodeposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc. (see article on Galvanization)
Ghosting Multiple TV images usually caused by the reception of a signal via two different paths.
Gregorian A dish with a parabolic offset main reflector and a concave sub-reflector.
Grid aerial A series of stacked "X" arrays with a grid reflector, to give a high front-to-back ratio. (see JBB/4)
G/T (Gain/noise Temperature) The figure of merit of a dish and LNB. The higher the G/T ratio, the better its reception capabilities.
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Half power beamwidth The beamwidth angle of a transmitting antenna that produces a beam footprint contour on which the signal power is 3 dB lower than the maximum value.
Half transponder A compromise method of broadcasting two signals through one transponder.
Harmonic A component of a wave having a frequency an integral number of times that of the basic (fundamental) frequency eg if the fundamental frequency is f Hz, then the harmonics are 2f,3f,4f etc.
HD DVD Short for High-Definition/Density DVD is a discontinued high-density optical disc format for storing data and high-definition video.
HDTV (High Definition TV) A TV format with 1250 scanning lines to improve picture resolution and viewing quality.
HDMI (High-Definition Multimedia Interface) Is a compact audio/video interface for transferring uncompressed video data and compressed/uncompressed digital audio data from an HDMI-compliant device ("the source device") to a compatible digital audio device, computer monitor, video projector, or digital television. HDMI is a digital replacement for existing analog video standards.
Head-end equipment The portion of an MATV system where all the signals are received and processed prior to distribution.
Hertz (Hz) An abbreviation for the frequency measurement of one cycle per second.
High-pass filter Circuit that passes signals above a designated frequency.
Home gateway An STB interface between the delivery platform and appliances or systems throughout the home.
Horizontal polarisation A radio wave where the electrical field is horizontal and the magnetic field is vertical.
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Impedance The resistance to alternating current flow in an electrical circuit.
Impulse noise External interference from terrestrial sources such as thermostats, fridges etc, that can cause a DTT receiver to block or freeze.
Inclinometer An instrument used to measure the angle of elevation to a satellite from the surface of the earth.
Inductance The effect of a magnetic flux created by a current flowing in an electrical circuit. An inductor is normally a coil of wire mounted on a former. Inductance is measured in "Henries".
Insertion loss or through loss The signal loss in dB caused by inserting a splitter or insert into a communications line.
Interframe (temporal) compression An MPEG compression technique transmitting only changes between frames.
Interlaced scanning A technique to minimise picture flicker whilst conserving channel bandwidth. Even and odd-numbered lines are scanned in separate fields to make one complete frame.
Intermediate frequency (IF) A middle frequency range generated after down- conversion in an LNB or receiver.
Intermodulation A form of interference caused by the modulation of one carrier affecting that of another signal in the same frequency band. It can be caused by non-linearity or the overloading of an amplifier.
Intraframe (spatial) compression An MPEG compression technique eliminating repitition.
Ionosphere A layer of the atmosphere that refracts or reflects electromagnetic radio waves,
Ingress Protection Rating

The IP Code classifies and rates the degree of protection provided against the intrusion of solid objects dust, accidental contact and water in mechanical casings.

Format is two digits reference. The first digit indicates the level of protection that the enclosure provides against access to hazardous parts (e.g., electrical conductors, moving parts) and the ingress of solid foreign objects. The second digit indicates the level of protection that the enclosure provides against harmful ingress of water. For example, an electrical socket rated IP55 is dust (Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact) and from splashing water (Water splashing against the enclosure from any direction shall have no harmful effect)

LPCM Linear pulse-code modulation (LPCM) is a method of encoding audio information digitally. The term also refers collectively to formats using this method of encoding.
IRD "Integrated Receiver-Decoder".
IRS "Integrated Reception System".
Isotropic Ideally, a point source that transmits signals of equal power in all directions.
ITU International Telecommunications Union.
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Ka band A band of frequencies 20-30 GHz.
Kelvin A degree of temperature in degrees Celcius or Centigrade. The Kelvin scale starts at absolute zero so Oº Celsius is equivalent to 273º Kelvin.
Krone tool A specialist tool for connecting telephone wires to phone sockets using the insulation displacement technique.
Ka band The band of frequencies 20-30 GHz.
Ku band The band of frequencies 10.7-18 GHz.
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Ladder styles The vertical part of a ladder to which the rungs are attached.
LAN (Local Area Network) A system to link computer terminals together.
Laser diode A device used in an fibre-optic transmitter that emits light waves at a single frequency.
Latitude The measurement of a position on the surface of the earth north or south of the equator, in degrees of angle.
L band A band of frequencies at 1.7 GHz
Letterbox A format for viewing widescreen pictures on a 4 x 3 TV screen.
Lightning protection A system to minimise the effects of a lightning strike.
Lip-Sync Audio to video synchronization (also known as audio video sync, audio/video sync, AV-sync, lip sync, or by the lack of it: lip sync error, lip-flap) refers to the relative timing of audio (sound) and video (image) parts during creation, post-production (mixing), transmission, reception and play-back processing. When sound and video have a timing related cause and effect, Lip-Sync can be an issue in television, videoconferencing, or film.
Link budget An overall calculation of power gains and losses from transmission to reception.
Linear polarisation Horizontally or vertically polarisation (as opposed to circular polarisation).
LNB "Low Noise Block downconverter". A low noise microwave amplifier and converter that downconverts a block or range of frequencies to an IF range.
Local oscillator A device used to supply a stable frequency to a down- converter. The local oscillator signal is mixed with the carrier wave to change its frequency.
Loft box or StarBox A unit containing all the devices commonly needed for the reception and distribution of terrestrial and satellite services within the home. (see proSTR range)
Log-periodic aerial A wideband TV aerial with elements of different lengths.
Longitude A distance in degrees east or west of the Greenwich meridian
LTE Long Term Evolution is the new protocol standard for all 4G phone systems and as its name suggests will be updated over time as new facilities are standardised. (see LTE FAQ)
Loop-wired network An MATV network (no longer recommended) where the cable loops from room to room between padded outlet plates
Low pass filter A circuit that only passes signals lower than a designated frequency.
LSOH (Low smoke/zero halogen) A type of cable specified for use in public buildings to minimise the fire risk.
Luminance The part of a TV waveform that contains the brightness information.
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Macro block A defined group of pixels used in MPEG compression.
Magnetic north The earth can be considered as a huge magnet having north and south magnetic poles. The line joining these poles is inclined slightly to the axis of rotation, hence true north and magnetic north do not coincide. A compass points to magnetic north.
Magnetic variation (or deviation) The difference between true north and the north indication on a compass.
MATV Master Antenna Television System. (see proLTA41)
Method statement A statement of the method to be used to carry out tasks.
Microwave The frequency range from 1-30GHz and above.
Mini DiSEqC A simple version of DiSEqC with only two states.
Mixer A device used to combine signals together.
Modem (modulator/demodulator) A telephone interface used in computers and digital TV receivers
Modulation A process by which information is added or encoded on to a carrier wave
Modulation error ratio (MER) A form of S/N ratio measurement, the noise being measured within the active channel.
Modulation index The ratio of peak deviation to the highest modulating frequency.
Modulator A device that modulates a video signal or MPEG2 transport stream onto a radio frequency carrier.
Monochrome A black and white TV picture
Motor feedback Information fed back to a motorised satellite receiver concerning the orientation of the dish
MPEG "Moving Picture Experts Group".
MPEG2 A set of digital TV compression standards.
MPEG4 A new compression standard that is "object-based".
Multicrypt A digital scrambling system that uses a common PCMCIA interface. Several CAMs can be daisy-chained in a single receiver.
Multimode A low-bandwidth mode of fibre-optic transmission using more than one light frequency. Used predominantly for telecommunication applications.
Multiplex (mux) The simultaneous transmission of several signals or programmes over a single communication channel.
Multiple dwelling unit (MDU) A group of homes, sometimes within the same building.
Multiswitch An IF switching unit to enable any satellite receiver to access either polarity or band using voltage and 22 KHz tone commands. Some versions relay terrestrial signals and allow access to multiple satellites using DiSEqC control signals.
Mutual isolation The isolation in dBs between drop-in cables connected to the same network tee insert.
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