AC-3 Flexible audio data compression format designed by Dolby laboratories to enable transmission of high-quality multi-channel audio such as Dolby Digital5.1 alongside digital TV signals. A digital TV receiver with the correct hardware recognises the AC-3 signal and passes it to a digital audio output, for decoding by suitable home cinema audio equipment.
Actuator Motor and feedback system to drive a motorised multi-satellite antenna.
Antenna Any device to pick up and deliver satellite microwave signals to the receiver.
Apex The highest point (e.g of a motorised dishes arc)
Arc The imaginary curve connecting the Clarke Belt satellites in the sky.
Aspect Ratio Ratio of the width of a TV picture to its height. Conventionally 4:3 (pronounced 4 by 3). See also Widescreen
Astra Digital Radio System for digital audio broadcasts by satellite using compressed digital audio occupying the audio subcarrier space.
AV (audio-visual) Equipment for all aspects of TV and audio.
Azimuth Compass bearing of a satellite or a dish’s reception path.
Bandwidth Range of frequencies occupied by a signal or allowed by equipment.
Baseband Raw satellite TV signal from a receiver before modulation to a signal suitable for a television.
Beam Satellite transmission pattern; may be wide, narrow or spot beam.
Beamwidth The acceptance angle of a dish.
Belling-Lee Plug/socket type used for UHF (aerial) connections and for LNB connections on a few European receivers.
BER (bit error rate) Accuracy of a digital signal. Equivalent to analogue S/N.
Bird Satellite.
Bit Rate Speed of digital transmission, usually expressed in Mb/s. About 5Mb/s is considered equivalent to a broadcast PAL picture, while about 2.5Mb/s is equivalent to VHS.
Boresight Direction along the principle reception path of an antenna; where it is ‘looking’.
CAM (conditional access module) Electronics used to unscramble a protected digital broadcast.
Cassegrain Design of dish using a convex hyperbolic secondary reflector in addition to the main parabolic reflector.
C-band Signal frequency range (3.700-4.200GHz) used for satellite TV, particularly in the US.
Centre-feed dish Dish with the focal point and feedhorn at the centre. See offset.
Chrominance Part of a television signal carrying the colour information of the picture.
CI (common interface) Connection standard for adding equipment to a digital receiver. Uses the same connector and card format as the PCMCIA computer standard.
Clarke Belt See Geostationary orbit
C/N (carrier to noise ratio) A measure of the performance of an antenna. Ratio of the received power to the noise power, expressed in dB.
Co-ax Co-axial cable and connectors used for aerial and antenna cables.
Co-located Satellites in the same apparent orbital position (within 0.2 degrees of one another)
Composite Video TV signal containing chrominance, luminance and sync information. Used in Scart connectors.
Compressed digital TV Digitised TV signal reduced in size by removing repeated information to allow several TV channels to occupy a single transponder.
Conditional Access Technology which prevents unauthorised viewing of TV or other content, usually by scrambling (encrypting) it and issuing a viewing card.
DBS band Portion (11.700-12.500GHz) of the Ku-band frequencies intended for direct broadcast by satellite channels.
Declination Small offset angle used on a polar mount to tilt the dish towards the horizon and so track the satellite arc.
Decoder Unit to unscramble a protected TV signal for viewing.
De-emphasis Filtering introduced by a receiver, in conjunction with the opposite ‘pre-emphasis’ at transmission to reduce audio noise.
Depolariser Device to convert circular polarised signals to linear polarisation for selection by a conventional polariser.
Digibox Digital satellite receiver for the Sky Digital service incorporating a Videoguard CAM
Digital SwitchoverStarting in 2008 and ending in 2012, TV services in the UK will go completely digital, TV region by TV region. This process is called digital switchover. The UK’s old television broadcast signal (known as “analogue”) is being switched off and replaced with a “digital” signal. Any TV set or video recorder that’s not converted to digital when the switchover takes place will no longer receive TV programmes.
Digital TV See Compressed digital TV.
Digital TV converter (aka DTT converter) Low cost digital terrestrial TV receiver which enables an individual analogue TV or VCR to pickup DTT channels via Scart or analogue UHF input.
DiSEqC (Digital Satellite Equipment Control) Control system for antenna peripherals such as LNBs and switches using digital codes formed from 22KHz pulses on the LNB power supply.
Dish Antenna using a parabolic reflector to collect microwave signals.
Downlink The signal’s path from the satellite to the receiving antenna.
DTH (direct to home) Satellite TV intended for domestic reception.
DTT (digital terrestrial television) Channels broadcast by ground based transmitter masts and received by a standard rooftop or indoor aerial through a DTT converter or IDTV, using a version of DVB standard optimised for terrestrial TV.
Dual-feed See Multi-feed
DVB (digital video broadcasting) Standard for digital broadcasting established in Europe but used worldwide with the exception of the US.
EIRP (effective isotropic radiated power) Measure of a satellites signal strength received on the ground.
El-az (elevation-azimuth) mount Simple fixed dish mount allowing adjustments in horizontal and vertical planes.
Elevation Vertical angle between an antenna’s reception path and the horizon.
Enhanced LNB (9.750GHz local oscillator) or receiver (extended IF) designed for the reception of Astra 1D signals.
EPG (electronic programme guide) Onscreen guide to the programmes showing at the time, and to come, on a number of channels.
Eurocrypt Smart card scrambling system used with many Mac transmissions.
Event timer Programmable timer built into a receiver to switch on and change channels for unattended video recording.
F-Connector A screw-on plug/socket commonly used for LNB-receiver connections
FEC (forward error correction) Tuning parameter for digital broadcasts. Expressed as a fraction of the data used for correcting data errors introduced in the reception.
Feedhorn Collects the microwave signals at the focus of a dish and channels them to the LNB.
Flat-plate antenna Flat (often square) antenna used instead of a dish. Works by adding together the signal from an array of collectors.
Focal point Position in front of a dish reflector where the reflected signals are gathered.
Footprint Area of the Earth in which a satellite’s signal can be received. Also refers to contour map of the received signal strength from a satellite.
Free-to-air Channel broadcast without any conditional access or scrambling, allowing reception with any suitable receiver.
FSS (fixed satellite services) band Portion (10.700-11.700GHz) of the Ku-band frequencies intended for business use, but now the main analogue satellite TV band.
Geostationary orbit Orbit used by TV satellites at a height of 22,250 miles, in which satellites make an orbit in 24 hours, remaining fixed relative to the earth’s surface.
Geosynchronous orbit See Geostationary orbit.
GHz (gigahertz) A billion cycles per second or 1,000MHz.
GPS Global Positioning System is a network of satellites that continuously transmit coded information, which makes it possible to precisely identify locations on earth by measuring distance from the satellites.
Gregorian Design of dish using a concave hyperbolic secondary reflector in addition to the main parabolic reflector.
Half-transponder mode Method of transmitting two TV channels on one transponder by sharing the bandwidth between them (usually two 36MHz channels on a 72MHz transponder). reduces the EIRP of each channel by about 4dB.Horizon-to-horizon Compact polar mount allowing extremely wide range of movement and accurate tracking.
Horn Antenna using an enlarged feedhorn and no reflector.
HDTV (high-definition television) TV system using an increased number of screen lines for a sharper picture.
HEMT (high electron mobility transistor) Type of low noise LNB.
IDTV (integrated digital TV) TV set with a built-in DTT or digital satellite TV receiver, removing the need for an external converter or receiver.
IF (intermediate frequency) Signal in cable between LNB and receiver. Also receiver’s tuning frequency. 950-2050MHz.
IF shifter Device inserted in the LNB cable to enable reception of frequency bands not intended for the LNB.
Inclined orbit orbit inclined relative to the equator. Produces apparent motion of the satellite above and below the arc.
Inclinometer Device to measure a vertical angle.
Interference Picture (or sound) distortion caused by an additional unwanted signal.
Jack See Actuator.
KHz (kilohertz) One thousand cycles per second.
Ka-band Signal frequency range (approximately 21-25GHz) now used for two-way broadband satellite services with small user terminals and dishes of less than a metre diameter.
Ku-band Signal frequency range (10.700-18.000GHz) used for most satellite TV in Europe.
Latitude The distance north or south of the equator, expressed in degrees.
Local oscillator Device inside the LNB which determine which received frequency band is converted to within the receiver’s tuning frequency: 10.000GHz for standard FSS, 9.750GHz for ’enhanced’ FSS, 10.750GHz for DBS, 11.475GHz for Telecom, 10.600GHz for Astra high band and 5.150GHz for C-band.
Longitude The distance east or west of the Prime/Greenwich meridian, expressed in degrees.
Loopthrough pair of output and input connections on a receiver that allows external equipment to be inserted in the TV signal path.
LNB (low-noise block down-converter) Amplifies received signals and converts them from microwaves to lower frequency electrical signal to send down cable to the receiver.
Luminance part of a TV signal carrying the brightness information of the picture (see also Chrominance)
Magnetic polariser Solid state polariser controlled by current from the receiver.
Marconi-type LNB See Voltage-switched LNB.
Mechanical polariser Servo actuated polariser controlled by electrical pulses from the receiver.
MHz (megahertz) one million cycles per second. 1,000KHz
Microwave Radio signal with a frequency of 1-30GHz.
Modulator Device which impresses the TV picture and sound signal onto a radio carrier for broadcast or loopthrough.
Mount Device to hold a satellite antenna and allow aiming adjustments.
MPEG (moving pictures expert group) international body to agree standard for compressed digital TV. MPEG-1: compression standard on VHS quality used in CD-video. MPEG-2: transmission-quality standard used for digital TV broadcasts.
MHEG-5 (Multimedia and Hypermedia information coding Expert Group) International open standard of software for operating interactive TV applications, used for British DTT.
Multi-feed Antenna system with two or more LNBs on a fixed dish to view more than one satellite.
Noise Unwanted constituent of a signal.
Noise figure Measure of the performance (noise contribution) of an LNB, in db - the lower, the better.
NTSC (national television standards committee) TV broadcast standard used in North America and Japan.
NVOD (near video on demand) Multi-channel system broadcasting many editions of a film with staggered start times so a complete film is always available to a viewer after a short wait.
Offset Type of dish antenna with the focus and feedhorn below the centre of the dish.
OMT (orthogonal mode transducer) Waveguide splitter to allow two LNBs to receive horizontal and vertical polarised signals simultaneously.
OpenTV Proprietary software for operating interactive TV applications used by Sky Digital in the UK and the FUN alliance of channels in Germany.
Orbit Path of satellite round the earth.
PAL (phase alternate line) TV system used by terrestrial TV in the UK and on most European satellite channels.
Parental lock receivers PIN operated lock that allows you to block out a specified channels.
Phono Plug/socket type used for receiver connections for audio, video and baseband signals.
PIN (Personal Identification Number) User set security code number which must be entered to watch certain channels, order goods, access menus, etc.
Polariser Device fitted on the dish to separate one polarity signal from the other.
Polarity property of satellite signals to differentiate between signals of similar frequencies and squeeze more channels into the available space. Signals are either linearly polarised (horizontal and vertical) or circularly polarised (left and right handed)
Polar mount Multi-satellite aligned so single movement allows the antenna to track the arc of the Clarke Belt.
Positioner unit to control the motor of a motorised dish to point the dish at pre-programmed positions. Can be included inside a multi satellite integrated receiver/positioner.
PPV (pay-per-view) Pay TV system allowing the purchase of an individual one time TV event.
Primary focus Focal point corresponding to the signals in the dish’s boresight.
Pro-Logic Surround sound decoder system invented by Dolby Laboratories to reproduce cinema sound in the home.
PVR (personal video recorder) Device using a hard disc drive to record TV in digital format, combined with an EPG to make programmed recordings easier.
Quad-band LNB LNB capable of receiving FSS, DBS and Telecom bands (including the 10.700-10.950GHz band first used by Astra 1D) in two ranges, selected from the receiver by altering the supply voltage (13/18V). See Triple band LNB.
Receiver Indoor unit to take signals from the antenna, tune and convert them for display on a TV.
Reflector Dish-shaped surface of an antenna which collects the signal.
Secam (sequence a memoire) A television system used by some French channels. It displays as black and white on UK PAL television.
Skew Fine tuning of polarity to account for different angles of signals from different satellites.
Scart European 21-pin plug and socket standard to link audio-visual equipment.
Secondary focus Focal point of a signal off the boresight of a dish. Used by multi-feed antennas.
Slot Satellite position in the Clarke Belt, expressed as degrees east or west of south (the orbital position above 0 degrees longitude)
Smart card credit card sized electronic key put in a decoder to unscramble a protected channel.
SMATV (satellite master antenna television) Satellite TV distribution system for blocks of flats with single antenna.
S/N (signal-to-noise) ratio ratio of a signal’s power to the noise power in a specific bandwidth, expressed in db.
SNG (satellite news gathering) Use of satellite TV technology to send news material from portable uplink stations.
Sound-in-sync Broadcast format in which audio data is placed in the picture’s sync pulses, producing an unstable silent picture without a decoder.
Sparklies Impulse noise seen as black and white speckles in the picture caused by too low a S/N ratio (too weak a signal).
S/PDIF (Sony/Philips digital interface) Standard for digital audio transmission using both fibre optic and coaxial connections, between a digital TV receiver and a home cinema audio system.
Statistical multiplexing Technique to increase the number of digital compressed channels broadcast in a given bandwidth by dynamically varying the compression ratio for each channel according to proramme content.
Subcarrier Auxiliary signal associated with an analogue satellite TV signal used for carrying the audio soundtrack or additional radio stations.
S-video Video format which maintains seperate chrominance and luminance signals.
Symbol rate Tuning parameter for digital broadcasts. Measure of the rate of supply of data in the signal.
Sync TV signal constituent which synchronises the picture scanning of the TV set with the transmission.
Telecom band Portion (12.500-12.750GHz) of the Ku-band frequencies first used by the French Telecom satellites but more correctly called broadcast satellite services (BSS) band.
Threshold Minimum C/N required to produce a sparklie-free picture. A measure of the sensitivity of a receiver - the lower the figure, the better.
Transponder (transmitter/responder) Equipment inside a satellite responsible for receiving a single uplinked channel and rebroadcasting it back to earth.
Triple-band LNB LNB which is capable of receiving FSS, DBS and Telecom bands in two ranges, selected from the receiver by altering the supply voltage (13/18V)
UHF (ultra high frequency) 300-3000MHz. UK terrestrial TV uses 470-890MHz.
Universal LNB Voltage switched type LNB with two reception frequency bands of 10.700-11.700GHz and 11.700-12.750GHz using local oscillator frequencies of 9.75GHz and 10.60GHz, selected by a 22KHz tone on the LNB power supply.
Uplink The signals path from earth to the satellite.
USALS (universal satellite location system) Enhancement of DiSEqC 1.2 motor control software enabling a motor to calculate the site of any satellite based on the user’s latitude and longitude.
USB (universal serial bus) High-speed data interface for connecting peripherals, such as cameras, PCs, hard disc drives and printers to satellite receivers, DTT converters and PVR.
Videocrypt Smart card operated encryption system used by Sky analogue subscription channels.
Videoguard Smart card operated encryption system used by Sky digital subscription services.
VOD (video on demand) Multi channel system allowing a film to be broadcast immediately it is requested by an individual viewer.
Voltage switched LNB Combined LNB/polariser used on Astra systems with polarity selected by changing the voltage (13/18V) supplied to the LNB.
Waveguide Accurately engineered channel for a microwave signal.
Widescreen TV picture with an aspect ratio greater than the standard 4:3. Usually 16:9, but 14:9, 23:3 and others also seen.
Wideband Very extended receiver’s IF tuning, allowing reception of Astra 1D with a ’standard’ LNB (with 10.000GHz local oscillator). 700-2,050MHz at least.
22KHz tones Control system for LNBs. Conceived to select reception bands on universal LNBs, also used for LNB switches and as basis for the DiSEqC control system.
