A Glossary of Cable and Satellite Terms
A/B Switch
A Switch that selects one of two inputs (A or B) for routing to a common output while providing adequate isolation between the two signals.
AFC (Automatic Frequency Control)
A circuit which locks an electronic component onto a chosen frequency.
AGC (Automatic Gain Control)
A circuit that uses feedback to maintain the output of an electronic component at a constant level with a variable input.
Absolute Zero
The coldest possible temperature at which all molecular motion ceases. It is expressed in degrees Kelvin as measured from absolute zero. Zero degrees Kelvin equals minus 273.16 °C or minus 459.69 °F. Adjacent ChannelAn Adjacent channel is immediately next to another channel in frequency. For example, NTSC channels 5 and 6 as well as 8 and 9 are adjacent. However, channels 4 and 5 or channels 6 and 7 are separated by signals used by non-TV media.
Agile Receiver
A satellite receiver, which can be tuned to any, desired channel.
Alignment
The process of fine-tuning a dish or an electronic circuit to maximize its sensitivity and signal receiving capability.
Ambient Temperature
The existing dry bulb temperature.
Amplifier
A device used to increase the power of a signal.
Analog
A system in which signals vary continuously in contrast to a digital system in which signals vary in discrete steps.
Analog-to-Digital Converter
A circuit that converts analog signals to an equivalent digital form. The varying analog signal is sampled at a series of points and times. The voltage at each of these points is then represented by a series of numbers, the digital value of the sample. The higher this sampling frequency, the finer are the graduations and the more accurately is the signal represented.
Antenna
A device that collects (and transmits) and focuses electromagnetic energy, i.e., contributes an energy gain. Satellite dishes, broadband antenna and cut-to-channel antennas are some types of antennas encountered in private cable systems. In the case of satellite antennas, gain is proportional to the surface area of the microwave dish.
Antenna Efficiency
The percentage of incoming satellite signal actually captured by an antenna.
Antenna Illumination
Describes how a feedhorn "sees" the surface of a dish as well as the surrounding terrain.
Aperture
The collection area of a parabolic antenna.
Aspect Ratio
The ratio of television screen width to height. The standard aspect ratio is 4 to 3.
Attenuation
The decrease in signal power that occurs in a device or when a signal travels to reach a destination point (path loss).
Attenuator
A passive device which reduces the power of signal. Attenuators are rated according to the amount of signal attenuation.
Audio Sub carrier
The carrier wave that transmits audio information within a video broadcast signal. Satellite transmissions can relay more than a single audio sub carrier in the frequency range between 5 and 8.5MHz.
Automatic Brightness Control
A television circuit used to automatically adjust picture tube brightness in response to changes in background or ambient light.
Automatic Fine Tuning
A circuit automatically maintains the correct tuner oscillator frequency and compensates for drift and for moderate amount of inaccurate tuning. Similar to AFC.
Automatic Brightness Control
A television circuit used to automatically adjust picture tube brightness in response to changes in background or ambient light.
Automatic Frequency Control (AFC)
A circuit that locks onto a chosen frequency and will not drift away from the frequency.
Automatic Fine Tuning
A circuit that automatically maintains the correct tuner oscillator frequency and compensates for drift and for moderate amounts of inaccurate tuning. See automatic frequency control (AFC).
Automatic Gain Control (AGC)
A circuit that locks the gain onto a fixed value and thus compensates for varying input signal levels keeping the output constant.
Azimuth-Elevation (Az-El) Mount
An antenna mount which tracks satellites by moving in two directions: the azimuth in the horizontal plane; and elevation up from the horizon.
Azimuth
A compass bearing expressed in degrees of rotation clockwise from true north. It is one of the two coordinates (azimuth and elevation) used to align a satellite antenna.
Back Match
The matching of the resistive values of the input and output of electronic devices to reduce signal reflection and ghosting. Also known as impedance meeting.
Back Porch
That portion of the horizontal blanking pulse that follows the trailing edge of the horizontal sync pulse. BalunA transformer used to match 75-ohm coaxial cable to a 300-ohm input on older televisions. This acronym is derived from combining the two words, Balanced and Unbalanced.
Band
A range of frequencies
Band Separator
A device that spills a group of specified frequencies into two or more bands. Common types include UHF/VHF, high/Low-band and FM separators. This device is essentially a set of filters.
Bandpass Filter
A circuit or device that allows only a specified range of frequencies to pass from input to output. BandstopSee bandpass filter.
Bandwidth
The frequency range allocated to any communication circuit.
Baseband
The raw audio and video signals prior to modulation and broadcasting. Most satellite headend equipment utilizes baseband inputs. More exactly, the composite unclamped, non-de-emphasized and unfiltered receiver output. This signal contains the complete set of FM modulated audio and data subcarriers.
Beamwidth
A measure used to describe the width of vision of an antenna. Beamwidth is measured as degrees between the 3dB half power points. BirdJargon or nickname for communication satellites.
Blanking Pulse Level
The references level for video signals. The blanking pulses must be aligned at the input to the picture tube. Blanking SignalPulses used to extinguish the scan illumination during horizontal and vertical retrace periods.
Block Downconversion
The process of lowering the entire band of frequencies in one step to some intermediate range to be processed inside a satellite receiver. Multiple block downconversion receivers are capable of independently selecting channels because each can process the entire block of signals.
BNC Connector
A weatherproof twist lock coax connector standard on commercial and broadcast video equipment and used on some brands of satellite receivers.
Boresight
The direction along the principle axis of either a transmitting or a receiving antenna.
Broadband
A device that processes a signal(s) spanning a relatively broad range of input frequencies.
Buttonhook Feed
A rod shaped like a question mark supporting the feedhorn and LNA. A buttonhook feed for use with commercial grade antennas is often a hollow waveguide the directs signals from a feedhorn to an LNA behind the antenna.<
CATV
An abbreviation for community antenna television- another name for cable TV.
CCD
Charge coupled device. In this device charge is stored on a capacitor, which are etched onto a chip. A number of samples can be simultaneously stored. Used in MAC transmissions for temporarily storing video signals. C-BandThe range of frequencies that includes 3.7 to 4.2 GHz for downlink and 5.7 TO 6.2 GHz FOR UPLINK.
Cable-Ready Television
A television receiver that can receive unscrambled cable television channels without the use of a converter. Cardioids PatternA heart-shaped pattern that is typical of some directional antennas.
Carrier
A pure-frequency signal that is modulated to carry information. In the process of modulation it is spread out over a wider band. The carrier frequency is the unmodulated frequency on any television channel.
Carrier-to-Noise Ratio (C/N)
The ratio of the received carrier power to the noise power in a given bandwidth, expressed in decibels. The C/N is an indicator of how well an earth receiving station will perform in a particular location, and is calculated from satellite power levels, antenna gain and the combined antenna and LNA noise temperature.
Cassegrain Feed System
An antenna feed design that includes a primary reflector, the dish, and a secondary reflector, which redirects microwaves via a waveguide to a low noise amplifier.
Channel
A segment of bandwidth used for one complete communication link.
Chrominance
The hue and saturation of a color. The chrominance signal is modulated onto a 4.43 MHz carrier in the PAL television system and a 3.58 MHz carrier in the NTSC television system.
Chrominance Signal
The color component of the composite baseband video signal assembled from the I and Q portions (NTSC) or U and V (PAL). Phase angle of the signal represents hue and amplitude represents color saturation.
Circular Polarity
Electromagnetic waves whose electric field uniformly rotates along the signal path. Broadcasts used by high power DBS intelsat and other international satellites use circular, not horizontally or vertically polarized waves as are common in the North American and European C-Band transmissions. Circularly polarized waves are used for satellite telephony because Faraday rotation does not alter their behavior.
Clamp Circuit
A circuit that removes the dispersion waveform from the downlink signal.
Clarke Belt
The circular orbital belt at 22,247 miles above the equator, named after the writer Arthur C. Clarke, in which satellites travel at the same speed as the earth's rotation. Also called the geostationary orbit. Color BarsA test pattern of specifically colored vertical bars used as a reference to test the performance of a color television and transmission paths.
Coaxial Cable
A cable for transmitting high frequency electrical signals with low loss. It is composed of an internal conducting wire surrounded by an insulating dielectric, which is further protected by a metal shield. The impedance of coax is a product of the radius of the central conductor, the radius of the shield and the dielectric constant of the insulation. In an SMATV system, coax impedance is 75 ohms.
Color Sync Burst
A "burst" of 8 to 11 cycles in the 4.43361875 MHz (PAL) or 3.579545 MHz(NTSC) color subcarrier frequency. This waveform is located on the back porch of each horizontal blanking pulse during color transmissions. It serves to synchronize the color subcarrier's oscillator with that of the transmitter in order to recreate the raw color signals.
Combining Network
An active or passive network that serves to combine several signals into one output while maintaining a high degree of isolation between each input.
Composite Baseband Signal
The complete audio and video signal without a carrier wave. Satellite signals have audio baseband information ranging in frequency from 55 to about 10,000 Hertz. NTSC video baseband is from zero to 4.2 MHz. PAL video baseband ranges from 0 to 5.5 MHz.
Composite Video Signal
The complete video signal consisting of the chrominance and luminance information as well as all sync and blanking pulses.
Companding
A form of noise reduction using compression at the transmitting end and expansion at the receiver. A compressor is an amplifier that increases its gain for lower power signals. The effect is to boost these components into a form having a smaller dynamic range. A compressed signal has a higher average level, and therefore, less apparent loudness than an uncompressed signal, even though the peaks are no higher in level. An expander reverses the effect of the compressor to restore the original signal.
Cone
An abbreviation for the European continent.
Converter
A device used to transfer signals from a channel of one frequency to another.
Contrast
The ratio between the dark and light areas of a television picture.
Conus
An abbreviation for the continental United States.
Cross Modulation
A form of interference caused by the modulation of one carrier affecting that of another signal. It can be caused by overloading an amplifier as well as by signal imbalances at the headend.
Cross Polarization
Term to describe signals of the opposite polarity to another being transmitted and received. Cross-polarization discrimination refers and rejects the signals having the opposite sense of polarity.
Crosstalk
Interference between adjacent channels often caused by cross modulation. Leakage can occur between two wires, PCB tracks or parallel cables.
Dc Power Block
A device, which stops the flow of dc, power but permits passage of higherfrequency ac signals.
Decibel (db)
The logarithimic ratio of power levels used to indicate gains or losses of signals Decibels relative to one watt, milliwatt and milllivolt are abbreviated as dBw, dBm and dBmV, respectively. Zero dBmV is used as the standard reference for all SMATV calculations.
Declination Offset Angle
The adjustment angle of a polar mount between the polar axis and the plane of a satellite antenna used to aim at the geosynchronous arc. Declination increases from zero with latitude away from the equator.
Decoder
A circuit that restores a signal to its original form after it has been scrambled.
De-emphasis
A reduction of the higher frequency portions of an signal used to neutralize the effects of pre-emphasis. When combined with the correct level of pre-emphasis, it reduces overall noise levels and therefore increases the signal-to-noise ratio.
Dehydrator
A device used to compress and dry the air that is contained inside an air dielectric transmission line.
Demodulator
A device, which extracts the baseband signal from the transmitted carrier wave.
Detent tuning
Tuning into a satellite channel by selecting a preset resistance
Digital
Describes a system or device in which information is transferred by electrical "on-off," "high-low," or "1/0" pulses instead of continuously varying signals or states as in an analog message.
Digital-to-Analog Converter
A circuit that converts digital signals into their equivalent analog form.
Diplexer
A device used to combine the video and audio components of a wireless signal. This component is internal to the transmitter at lower powers ranging from 1 to 50 watts but is external at higher powers.
Dipole Antenna
A two-element receiving or transmitting antenna that is typically center-fed and half a wavelength in length. Direct Broadcast Satellite
(DBS)
A term commonly used to describe Ku-band broadcasts via satellite directly to individual end-users. The DBS band ranges from 11.7 to 12.2 GHz.
Direct Pickup
Signal ingress from local services into a distribution system.
Directional Coupler
See Tap DishJargon for a parabolic microwave antenna.
Distribution System
A communication system consisting of coax but occasionally of line-of-sight microwave links that carriers signals from the headend to end-users
Domsat
Abbreviation for domestic communication satellite.
Downconverter
A circuit that lowers the high frequency signal to a lower, intermediate range. ThereAre three distinct types of downconversion used in satellite receivers: single downconversion; dual downconversion; and block downconversion.
Downlink Antenna
The antenna on-board a satellite which relays signals back to earth.
Drifting
An instability in present voltage, frequency or other electronic circuit parameter.
Drop Cable
The cable used to route a signal from outside distribution equipment to a subscriber television receiver and other equipment.
Dual-Band Feedhorn
A feedhorn, which can simultaneously receive two different bands, typically the C and Ku-bands.
Earth Station
A complete satellite receiving or transmitting station including the antenna, electronics and all associated equipment necessary to receive or transmit satellite signals. Also known as a ground station.
Effective Isotropic Radiated Power (EIRP)
A measure of the signal strength that a satellite transmits towards the earth below. The EIRP is highest at the center of the beam and decreases at Angeles away from the boresight.
Elevation Angle
The vertical angle measured from the horizon up to a targeted satellite.
Encoder
A device for scrambling a signal.
Energy Dispersal
The modulation of an uplink carrier with a triangular waveform. This technique disperses the carrier energy over a wider bandwidth than otherwise would be the case in order to limit the maximum energy compared to that transmitted by an unclamped carrier. By spreading the spectrum, there is less chance of interfering with other users of the same frequencies. A clamp circuit in a satellite receiver removes this triangular waveform.
Equalizing Pulses
A series of six pulses occurring before and after the serrated vertical sync pulse to ensure proper interlacing. The equalizing pulses are inserted at twice the horizontal scanning frequency.
F-Connector
A standard RF connector used to link coax cables with electronic devices.
FCC
The federal communications commission, the regulatory board which sets standards for communications within he United States
F/D Ratio
The ratio of an antenna's focal length to diameter. It describes antenna "depth".
Feedhorn
A device that collects microwave signals reflected from the surface of an antenna. It is mounted at the focus of all prime focus parabolic antennas.
Field
One half of a complete TV picture or frame composed of 262.5 scanning lines. There are 60 fields per second for black/white TV and 59.94 fields per second for color TV in NTSC transmission. In the PAL broadcast system there are 50 fields per second.
Filter
A devise used to reject all but a specifeid range of frequencies. A bandpass filter allows only those signals within a given band to be communicated. A rejection filter, the mirror image of a bandpass filter, eliminates those signals within a specified band but passes all other frequencies.
Focal Length
The distance from the reflective surface of a parabola to the point at which incoming satellite signals are focused, the local point.
Footprint
The geographic area towards which a satellite downlink antenna directs its signal. The measure of strength of this footprint is the EIRP.
Forward Error Correction
FEC is a technique for improving the accuracy of data transmission. Excess bits are included in the out-going data stream so that error correction algorithms can be applied upon reception.
Frame
One complete TV picture, composed of tow fields and a total of 525 and 625 scanning lines in NTSC and PAL systems, respectively.
Frequency
The number of vibrations per second of an electrical or electromagnetic signal expressed in cycles per second or Hertz.
Front Porch
The portion of the horizontal blanking pulse that proceeds the horizontal sync pulse.
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 an antenna and LNA. The higher the G/T, the better the reception capabilities of an earth station.
Geostationary Orbit
See Clarke Belt.
Ghost
A weak image either offset to the left or right of the primary image in a received television picture, a result of multipath conditions.
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.
Guard Band
An unused band of frequencies between two active channels that can serve to prevent mutual interference.
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 MIRROR.
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 system where all desired signals are received and processed for subsequent distributions. HeliaxA thick low-loss cable used at high frequencies; also known as hardline.
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 Pass Filter
An electronic circuit designed to pass all frequencies above a specified frequency while attenuating signals with frequencies below the rated value
High Power Amplifier (HPA)
An amplifier used to amplify the uplink signal.
Home Run
A method to wire a distribution system using individual drop cables to each subscriber.
Horizontal Blanking Pulse
The pulse that occurs between each horizontal scan line and extinguishes the beam illumination during the retrace period.
Horizontal Sync Pulse
A 5.08 microsecond (4.7 microsecond in the PAL system) rectangle pulse riding on top of each horizontal blanking pulse. It synchronizes the horizontal scanning at the television set with that of the television camera.
Hum Bars
A form of interference seen as horizontal bars or black regions passing across the field of a television screen caused by the mains 50 or 60-cycle power.
I Signal
One of the two-color NTSC video signals which modulate the color subcarrier. It represents those colors ranging from reddish orange to cyan.
IF Rejection
Rejection of signals that fall in the same band as the desired signal.
ITFS
An abbreviation for instructional television fixed services, a block of frequencies allocated for broadcast of wireless signals by educational institutions in the United States.
Image Frequency
An undesired signal obtained in frequency conversion using a mixing or heterodyning process.
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.
IIPV
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. Input ImpedanceThe effective impedance measured across the input terminals of an electronic device
Interference
An undesired signal intercepted by a TVRO that causes video and/or audio distortion.
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
A middle range frequency generated from creation of two or more beats between carriers. Beat frequencies are given by fbeat = nf1 + mf2 where n and m are integers.
Intermodulation
A form of interference that is generated after downconversion in any electronic circuit including a satellite receiver. The majority of all signal amplification, processing and filtering in a receiver occur in the IF range. Insertion LossThe amount of signal energy lost when a device is inserted into a communication line. Also known as "feed through" loss.
INTELSAT
The international Telecommunication Satellite Consortium, a body of 154 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.
Jumper
A short piece of transmission line used to interface components in a broadcast system.
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 (°C). Absolute zero equals -273 °C or - 459 °F. Used to rate noise in on LNA.
Kilohertz (KHZ)
One thousand cycles per second.
Ku-Band
The microwave frequency band between approximately 11 and 13 GHz used in satellite broadcasting.
Latitude
The measurement of a position on the surface of the earth north or south of the equator measured in degrees of angle.
Leakage
Egress interference, namely an undesired leakage of radiation from a cable or other closed circuit system
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 east or west of the prime meridian, zero degrees, as measured in degrees.
Low Band
Television channels 2 through 6. Low Noise Amplifier
(LNA)
A device that receives and amplifies the weak satellite signal reflected by an antenna via a feedhorn. C-band LNAs typically have their noise characteristics quoted as noise temperatures rated in degrees Kelvin. K-band LNA noise characteristics are usually expressed as a noise figure in decibels.
Low Noise Converter (LNC)
An LNC 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.
Low Pass Filter
An electronic circuit designed to pass all frequencies below a specified frequency while attenuating signals with frequencies above the rated value.
MDS
An abbreviation for multipoint distribution service, a band of frequencies in the United States allocated for wireless television broadcast service.
MMDS
An abbreviation for multichannel multipoint distribution service, a band of frequencies in the United States allocated for wireless television broadcast service.
Magnetic Variation
The difference between true north and the north indication of a compass.
Master Antenna TV (MATV)
Broadcast receiving stations that use one or more high-quality centrally located UHF and/or VHF antennas which relay their signals to many televisions in a local apartment/condo or group-housing complex.
Match
The condition that exists when 100 percent of available power is transmitted from one device to another without any losses due to reflections.
Matching Transformer
A device used to match impedance between devices. A matching transformer is used, for example, when connecting a 75 ohm coax to a television 300 ohm input terminal.
Megahertz (MHz)
One Millions Cycles per second.
Microprocessor
The central processing unit of a computer or control system, either on a single integrated (IC) circuit chip or on several ICs.
Microwave
The frequency range from approximately 1 to 30 GHz and above.
Midband
Cable television channels A through I that lie between VHS channels 6 and 7.
Mixer
A device used to combine signals together.
Modulation
A process in which a message is added or encoded onto a carrier wave. Among other methods, this can be accomplished by frequency or amplitude modulation, known as AM or FM respectively.
Monochrome
A black and white television picture.
Mount
The structure that supports an earth station antenna. Polar and az-el (azmuth- Elevation) mounts are the most common variety. Multiple Analog Component
(MAC) Transmissions
An innovative television transmission method which separates the data, chrominance and luminance components and compresses them for sequential relay over one television scan line. There are a number of systems in used and under development including A-MAC,B-MAC,C-MAC,D-MAC,D2-MAC,E-MAC and F-MAC.
Multiplexing
The simultaneous transmission of two or more signals over a single communication channel. The interleaving of the luminance and chrominance signals is one form of multiplexing, known as frequency multiplexing.
MAC
transmissions make use of time division multiplexing.
N-Connector
A low-loss coaxial cable used at the elevated C-band microwave frequencies.
NTSC
The national television standards committee which created the standard for North American TV broadcasts.
NTSC Color Bar Pattern
The standard test pattern of six adjacent color bars including the three primary colors plus their three complementary shades
Negative Picture Phase
Positioning the composite video signal so that the maximum level of the sync pulses is at 100% amplitude. The brightest picture signals are in the opposite negative direction.
Negative Picture Transmission
Transmission system used in North America and other countries in which a decrease in illumination of the original scene causes an increase in percentage of modulation of the picture carrier. When demodulated, signals with a higher modulation percentage have more positive voltages.
Noise
An unwanted signal which interferes with reception of the desired information. Noise is often expressed in degrees Kelvin or in decibels.
Noise Figure
The ratio of the actual noise power generated at the input of an amplifier to that which would be generated in an ideal resistor. The lower the noise figure, the better the performance.
Noise Temperature
A measure of the amount of thermal noise present in a system or a device. The lower the noise temperature, the better the performance.
OFS
An abbreviation for operational fixed services, a block of three channels for designated with the letter H, originally intended for use by banks and other businesses for transmission of high speed data.
Odd Field
The half frame of a television scan which is composed of the odd numbered lines.
Offset Feed
A feed which is offset from the center of a reflector for use in satellite receiving systems. This configuration does not block the antenna aperture.
Omnidirectional Antenna
An antenna that radiates power with equal strengths in all directions.
Orthomode Coupler
A waveguide, generally a three-port device, that allows simultaneous reception of vertically and horizontally polarized signals.The input port is typically a circular waveguide. The two output ports are rectangular waveguides.
PAL
Phase alternate line. The European color TV format which evolved from the American NTSC standard.
Pad
A concrete base upon which a supporting pole and antenna can be mounted.
Passband
The band of frequencies that a circuit passes with a little attenuation.
Path Loss
The attenuation that a signal undergoes in traveling over a path between two points. Path loss varies inversely as the square of the distance traveled.
Parabola
The geometric shape that has the property of reflecting all signals parallel to its axis to one point, the focal point.
Pay-Per-View
Pay-Per-View is a method of purchasing programming on a per-program basis.
Persistence of Vision
The physiological phenomena whereby a human eye retains perception of an image for a short time after the image is no longer visible.
Phase
A measure of the relative position of a signal relative to a reference expressed in degrees.
Phase Distortion
A distortion of the phase component of a signal. This occurs when the phase shift of an amplifier is not proportional to frequency over the design bandwidth.
Picture Detail
The number of picture elements resolved on a television picture screen. More "crisp" pictures as the number of picture elements is increased.
Polar Mount
An antenna mount that permits all satellites in the geosynchronous arc to be scanned with movement of only one axis.
Polarization
A characteristic of the electromagnetic wave. Four senses of polarization are used in satellite transmissions: horizontal; vertical; right-hand circular; and left-hand circular.
Positive Picture Phase
Positioning of the composite video signal so that the maximum point of the sync pulses is at zero voltage. The brightest illumination is caused by the most positive voltages.
Preamplifier
The first amplification stage. In an SMATV system, it is amplifier mounted adjacent to an antenna to increase a weak signal prior to its processing at the headend.
Pre-emphasis
Increases in the higher frequency components of an FM signal before transmission. Used in conjunction with the proper amount of de-emphasis at the receiver, it results in combating the higher noise detected in FM transmissions.
Primary Colors
Red, Green and Blue Prime Focus AntennaA parabolic dish having the feed/LNA assembly at the focal point directly in the front of the antenna
Q Signal
One of two color video signal components used to modulate the NTSC color subcarrier. It represents the color range from yellowish to green to magenta.
Radio Frequency
The approximately 10 KHz to 100 GHz electromagnetic band of frequencies used for man-made communication.
Raster
The random pattern of illumination seen on a television screen when no video signal is present.
Reed Switch
A mechanical switch uses two thin slivers of metal in a glass tube to make and break electrical contract and thus to count pulses which are sent to the antenna actuator controller. The position of the slivers of metal is governed by a magnetic field applied by a bar or other type of magnet.
Reference Signal
A highly stable signal used as a standard against which other variable signals may be compared and adjusted.
Repeater
A device that receives and re-broadcasts signals to extend the range of an original broadcast facility.
Return Loss
A ratio of the amount of reflected signals to the total available signal entering a device expressed in decibels.
Retrace
The blanked-out line traced by the scanning beam of a picture tube as it travels from the end of any horizontal line to the beginning of either the next horizontal line to the beginning of either the next horizontal line or field.
SAW (Surface Acoustic Wave) Filter
A solid state filter that yields a sharp transition between regions of transmitted and attenuated frequencies.
SLM
Abbreviation for signal level meter
Satellite Receiver
The indoors electronic component of an earth station which downconverts, processes and prepares satellite signals for viewing or listening.
Scanning
The organized process of moving the electron beam in a television picture tube so an entire scene is drawn as a sequential series of horizontal lines connected by horizontal and vertical retraces.
Scrambling
A method of altering the identity of a video or audio signal in order to prevent its reception by persons not having authorized decoders.
Screening
A metal, concrete or natural material that screens out unwanted TI from entering an antenna or a metal shield that prevents the ingress of unwanted RF signals in an electronic circuit.
Serrated Vertical Pulse
The television vertical sync pulse which is subdivided into six serrations. These sub-pulses occur at twice the horizontal scanning frequency.
Servo Hunting
An oscillatory searching of the feedhorn probe when use of inadequate gauge control cables results in insufficient voltage at the feedhorn
Side Lobe
A parameter used to describe an antenna's ability to detect off-axis signals. The larger the side lobes, the more noise and interference an antenna can detect.
Sidebands
The signals falling in the band of frequencies on either side of a carrier resulting from the process of modulation.
Single Channel Per Carrier (SCPC)
A satellite transmission system that employs a separate carrier for each channel, as opposed to frequency division multiplexing that combines many channels on a single carrier.
Signal-to-Noise Ratio (S/N)
The ratio of signal power to noise power in a specified bandwidth, usually expressed in decibels. SkewA term used to describe the adjustment necessary to fine tune the feedhorn polarity detector when scanning between satellites
Slant Range
The distance that a signal travels from a satellite to a TVRO.
Snow
Video noise or sparkles caused by an insufficient signal-to-noise input ratio to a television set or monitor.
Solar Outage
The loss of reception that occurs when the sun is positioned directly behind a target satellite. When this occurs, solar noise drowns out the satellite signal and reception is lost.
Sparklies
Small black and/or white dashes in a television picture indicating an insufficient signal-to-noise ratio. Also known as "snow." Spherical AntennaAn antenna system using a section of a spherical reflector to focus one or more satellite signals to one or a series of focal areas.
Splitter
A device that takes a signal and splits it into two or more identical but lower power signals. SubcarrierA signal that is transmitted within the bandwidth of a stronger signal. In satellite transmissions a 6.8 MHz audio subcarrier is often used to modulate the C-band carrier. In television, a 3.58 MHz subcarrier modulates the video carrier on each channel
Surface Acoustic Wave
A sound or acoustic wave traveling on the surface of the optically polished surface of a piezoelectric material. This wave travels at the speed of sound but can pass frequencies as high as several gigahertz. See SAW Filter.
Synchronizing Pulses
Pulses imposed on the composite baseband video signal used to keep the television picture scanning in perfect step with the scanning at the television camera.
TVRO
A television receive-only earth station designed only to receive but not to transmit satellite communications.
Tap
A device that channels a specific amount of energy out of the main distribution system to a secondary outlet. Television Receive-Only
(TVRO)
A satellite system that can only receive but not transmit signals.
Terrestrial Interference (TI)
Interference of earth-based microwave communications with reception of satellite broadcasts. TiltThe uneven attenuation of a broadband signal as it travels through a coaxial cable. In general, attenuation increases as signal frequency increases.
Thermal Noise
Random, undesired electrical signals caused by molecular motion, known more familiarly as noise.
Trace
The movement of the electron beam from left to right on a television or oscilloscope screen.
Threshold
A minimal signal to noise input required to allow a video receiver to deliver an acceptable picture.
Transponder
A microwave repeater, which receives, amplifiers, downconverters and re-transmits signals from a communication satellite.
Trap
An electronic device that attenuates a selected band of frequencies in a signal. Also known as a notch filter.
UHF
Ultrahigh frequencies ranging from 300 to 3,000 MHz. North American TV channels 14 through 83. European TV channels 21 to 69.
Upconverter
A device that increases the frequency of a transmitted signal
Uplink
The earth station electronics and antenna which transmits information to a communication satellite.
VHF
Very high frequencies in the range from 54 MHz to 216 MHz, NTSC TV channels 2 through 13.
VSWR (Voltage Standing Wave Ratio)
The ratio between the minimum and maximum voltage on a transmission line. An ideal VSWR is 1.0. Ghosting can result as the VSWR increases. It is also a measure of the percentage of reflected power to the impinging upon a device.
Vertical Blanking Pulse
A pulse used during the vertical retrace period at the end of each scanning field to extinguish illumination from the electron beam.
Vertical Sync Pulse
A pulse which occurs during the vertical blanking interval to synchronize the scanning process at the television with that created at the studio. See also serrated vertical pulse.
Video Signal
That portion of the transmitted signal containing the picture information.
Voltage Tuned Oscillator (VTO)
An electronic circuit whose output oscillator frequency is adjusted by voltage. Used in downconverters and satellite receivers to select from among transponders.
Video Monitor
A television that accepts unmodulated baseband signals to reproduce a broadcast. Yagi AntennaAn antenna consisting of a driven element that is typically a folded dipole, a parasitic reflector and one or more directors.