Adjacent Channels
Any of two TV channels are considered adjacent when their frequencies
are next to each other in frequency or channel number.
Amplifier A device that boosts the strength of a television
signal.
Analog A method of signal transmission in which information
is relayed by continuously altering the wave form of the electromagnetic
current. Now used in AM radio or most voice telephone circuits. In telephone
transmission, the signal being transmitted voice, video or image is
"analogous" to the original signal.
Antenna A wireless system component that converts wired
electrical energy to wireless radio waves, and directs them through
the air in some pattern.
Antenna Array An antenna comprising a number of radiating
elements, generally similar, which are arranged and excited to obtain
directional radiation patterns.
Attenuation In general terms, a reduction in signal
strength.
Automatic Frequency An arrangement whereby the frequency
of an oscillator is automatically maintained within specified limits.
Automatic Gain Control A circuit for automatically
controlling amplifier gain in order to maintain a constant output voltage
with a varying input voltage within a predetermined range of input-to-output
variation. A process by which gain is automatically adjusted as a function
of input or other specified parameter.
Axial Ratio The ratio of the axes of the polarization
ellipse.
Backhaul Point-to-point video transmission from a remote
site back to a central site for further distribution.
Band A clearly defined range of radio frequencies dedicated
to a particular purpose.
Bandwidth The number of cycles per second (Hertz) expressing
the difference between the lower and upper limiting frequencies of a
frequency band; also, the width of a band of frequencies. The range
of frequencies within which the performance of the antenna, with respect
to some characteristic, conforms to a specified standard. Greater bandwidth
generally provides for a more robust system because changes in the installation
environment will not degrade antenna performance.
Bandwidth A range of frequencies on the electromagnetic
spectrum.
Beam width In a plane containing the direction of the
maximum of a beam, the angle between the two directions in which the
radiation intensity is one half the maximum value of the beam.
Bi-directional Communications between two points where
each point both transmits and receives.
Bird Slang for communications satellite.
Bounce Sudden variations in picture presentation (brightness,
size, etc.,) independent of scene illumination.
Broadband A descriptive term for evolving digital technologies
that provide consumers a signal switched facility offering integrated
access to voice, high-speed data service, video-on-demand services and
interactive delivery services.
Broadband In television system use, a device having
a bandpass greater than the band of a single VHF television channel.
CATV Cable TV A service through which subscribers pay
to have local television stations and other programs brought into their
homes from the antenna via coaxial cable
C-Band The 3.7 - 4.2 GHz (Gigahertz) frequency band
is used for the distribution of programming by virtually all satellite/cable
networks. There are 22 C-Band satellites in operation over North America
today. They range in power from 5-11 watts per transponder, requiring
receive antennas of 5-12 feet in diameter. Beginning in 1992, the fleet
was gradually replaced with higher powered (10-17 watt) satellites.
This allows the average size of a C-Band installation to be reduced
to 90 inches in diameter.
Channel A 6 MHz wide portion of the RF spectrum carrying
TV video and audio carriers.
Clarke Belt The name given in honor of Arthur C. Clarke,
to the orbit 22,300 miles directly above the equator where satellites
can maintain a stationary position in relation to the earth. Also called
geostationary orbit.
Coax Short for coaxial cable.
Coaxial Antenna An antenna comprised of an extension
to the inner conductor of a coaxial line and a radiating sleeve which
in effect is formed by folding back the outer conductor of the coaxial
line.
Coaxial Cable A type of cable capable of transmitting
a range of frequencies with low signal loss. Commonly used for transmitting
video and audio in security systems.
Coaxial Cable A type of cable commonly used in cable
(CATV) and direct broadcast satellite (DBS) television systems. Composed
of two concentric conductors (an inner wire and a braided shield) separated
by a dielectric material. The whole thing is usually wrapped in another
insulating layer and an outer protective layer. Most coaxial cable used
in CATV and DBS applications has an impedance of 75 ohms. A coaxial
cable has great capacity to carry great quantities of information. It
is typically used to carry high-speed data and in CATV (multiplexed
TV stations.)
Compression A term used to denote reducing the amount
of bandwidth needed to transmit video or audio, thus increasing the
capacity of a satellite transponder. The reduction in gain at one level
of a picture signal with respect to the gain at another level of the
same signal.
Crosstalk An undesired signal from a different channel
interfering with the desired signal.
dB Decibels A technique for expressing voltage, power,
gain, loss, or frequency in logarithmic form against a reference. Typical
references include volts, Watts or Ohms. An analog unit of measure of
signal strength, volume or signal loss due to resistance as expressed
in logarithmic form. A measure of the power ratio of two signals. In
system use, a measure of the voltage ratio of two signals, provided
they are measured across a common impedance.
Hz. Decibels are calculated using the expression: dB
= 10*log(x/y)
dBi A ratio of decibels to an isotropic antenna that
is commonly used to measure antenna gain. The greater the dBi value,
the higher the gain and, as such, the more acute the angle of coverage.
dBmV A signal measurement whereby 0 dBmV equals 1000
microvolts across 75 ohms. A recommended signal level for a TV to receive
is 10 dBmV.
DBS Direct Broadcast Satellite A high-powered satellite
that transmits or retransmits signals which are intended for direct
reception by the public. The signal is received by a small (typically
18-inch diameter) dish mounted on the sides of homes or on other buildings.
Signal content is generally television programing.
Decibel A unit to measure the relative levels of current,
voltage or power. This is the scale used to measure the strength of
a TV signal. An increase of 3 dB indicates a doubling of power.
Demodulation The process for retrieving an information
signal that has been modulated onto a carrier.
Descrambler Set-top box. A device which corrects a
signal (often video) that has been intentionally distorted to prevent
unauthorized viewing. Used with satellite TV systems.
Digital A method of storing, converting and sending
data in the form of binary digits ( 0 or 1). In displays, the use of
digits for direct readout. In telecommunications, in the recording or
in computing, digital is the use of a binary code to represent information.
Analog signals (like voice or music) are encoded digitally by sampling
the voice or music analog signals many times a second and assigning
a number to each sample. Recording or transmitting information digitally
has two major benefits. The signal can be reproduced more precisely
so digital transmission is much "cleaner" than analog transmission.
The second major benefit of digital is that the electronic circuitry
to handle digital is getting cheaper and more powerful.
Digital Recording Technology that enables video images
to be stored on a hard drive or other digital storage medium rather
than on an analog medium such as a videotape.
Dipole A type of low gain antenna consisting of two
(often internal) elements.
Directional Antenna An antenna having the property
of radiating or receiving electromagnetic waves more effectively in
some directions than others.
Dish cover A cylindrical weather protection device.
Dish Size Refers to the diameter of the dish, or antenna,
used in satellite reception.
Dish Slang term for antenna.
Distortion The deviation of the received signal waveform
from that of the original transmitted waveform.
Distribution Amplifier A device that provides several
isolated outputs from one looping or bridging input, and has a sufficiently
high input impedance and input-to-output isolation to prevent loading
of the input source.
Diversity Antenna An intelligent system of two antennas
that continually senses incoming radio signals and automatically selects
the antenna best positioned to receive it.
Downlink To receive from a satellite also, the dish
used for reception.
DSL Digital Subscriber Line A generic name for a family
of evolving digital services to be provided by local telephone companies
to their local subscribers. Such services go by different names and
acronyms - ADSL (Asymmetric Digital Subscriber Line), HDSL (High Bit
Rate Digital Subscriber line) and SDSL (Single Pair Symmetrical Services).
Such services propose to give the subscriber up to eight million bits
per second one way, downstream to the customer and somewhat fewer bits
per second upstream to the phone company.
DTH Direct-To-Home. A term referring to all home
satellite platforms.
DVR Digital Video Recorders (same as PVR).
Dynamic Range The difference between the maximum acceptable
signal level and the minimum acceptable signal level.
Embedded Antenna Typically an antenna that is enclosed
into a product's housing or case, or one that is not readily discernible
by a casual observer. The antenna forms an integral, inseparable part
of the product.
Encryption/ Decryption Encryption is the process of
electronically altering a video and/or audio from its original condition.
Decryption is the process of returning the video and/or audio to its
original condition.
EPG Electronic Programming Guide.
F-connector The final piece of hardware on a cable
designed for CATV or DBS or other signal distribution applications.
It is cylindrical with a center pin sticking out, that plugs into the
set-top box, cable ready TV, satellite receiver, or VCR.
Feedhorn The part of the satellite system that collects
and focuses satellite signals reflected by the antenna.
Fiber Optics Fiber A shortened way of saying "fiber
optic." Fiber is made of very pure glass. Digital signals, in the form
of modulated light, travel on strands of fiber for long distances. The
big advantage that fiber has over copper is that it can carry far, far
more information over much, much longer distances.
Field of View The maximum angle of view that can be
seen through a lens or optical instrument.
Field One of the two equal but vertically separated
parts into which a television frame is divided in an interlaced system
of scanning. A period of 1/60 second separates each field start time.
Filter A circuit that selects the frequency of desired
channels through the use of band pass, low pass, and high pass filters
remove certain unwanted signals to make room for the insertion of a
new modulated TV channel
Frequency Response The range of band of frequencies
to which a unit of electronic equipment will offer essentially the same
characteristics.
Frequency The number of times an electromagnetic wave
goes through a complete cycle in one second, measured in Hertz.
FSS Fixed Satellite Service.
Gain An increase in voltage or power, usually expressed
in dB. In a given direction, 4 pi times the ratio of the radiation intensity
in that direction to the net power accepted by the antenna from the
connected transmitter. A measure of amplification expressed in dB. Gain
of an amplifier is usually specified at the highest frequency of operation.
Ghost A spurious image resulting from an echo.
GHz Gigahertz; one trillion cycles per second (a measure
of frequency).
Ground Plane A conducting or reflecting plane functioning
to image a radiating structure.
GSO Geosynchronous Orbit; satellites in geosynchronous
orbit travel around the earth in an area approximately 22,300 miles
from the surface at the same rate that the earth turns, therefore completing
one revolution every 24 hours.
Headend A cable TV systems control center where incoming
signals from satellites and other sources are put into the system. (Head
End) The originating point of a signal in cable TV systems. At the head
end, you'll often find large satellite receiving antennae. A central
control device required within some LAN systems to provide such centralized
functions as remodultaion, re-timing, message accountability, connection
control, diagnostic control, and access.
Headend Homerun Wire The Homerun Wire is most often
a single wire (usually an RG6 or RG59 coaxial cable) that runs from
each apartment building's meter room to each apartment and is designed
to deliver television or telephone services. Some of the modern day
Homerun Wires are being used to deliver all services, cable and satellite
television, telephone and fax and high-speed Internet connections.
High Definition Television Technology that significantly
increases the resolution of digital video signals offering vastly improved
picture quality over the current NTSC standard.
Hum Electrical disturbance at the power supply frequency
or harmonics thereof.
Hybrid Satellite A satellite that carries two or more
different communications payloads (i.e., C-Band and Ku-Band).
Hz Hertz Cycle per second; a measure of electromagnetic
frequency that represents the number of complete electrical waves in
a second. One kilohertz (kHz) is one thousand cycles per second; one
megahertz (MHz) is one million; one gigaHertz (GHz) is one billion.
Impedance (input or output) The input or output characteristic of a
system component that determines the type of transmission cable to be
used. The cable used must have the same characteristic impedance as
the component. Expressed in ohms. Video distribution has standardized
on 75-ohm coaxial and 124-ohm balanced cable.
Impulse Pay-Per-View Technology that allows the consumer to
purchase a movie or special event instantly via a computerized order
processing center. This technology allows for the processing of a high
volume of orders in a short time period.
Input Impedance The impedance presented by an antenna
at its terminals.
Inside Wiring That wiring located inside your premises
or building. Inside wiring starts at the telephone or cable company's
Demarcation Point and extends to the individual extensions. Traditionally,
Inside Wiring was installed and owned by the installing company.
Interference Extraneous energy which tends to interfere
with the reception of the desired signals.
IPG Interactive Programming Guide.
IRD(integrated receiver decoder) A device capable of
receiving and tuning satellite signals. The output of the receiver can
be either Baseband video for use with video monitors or RF for use with
standard TV sets.
Isolation Amplifier An amplifier with input circuitry
and output circuitry designed to eliminate the effects of changes made
at either upon the other.
Isolation Between Antennas A measure of power transfer
from one antenna to another - the ratio of power input to one antenna
to the power received by the other, usually expressed in decibels.
Isotropic A hypothetical antenna having equal radiation
intensity in all directions.
Jitter Small, rapid variations in a waveform due to
mechanical disturbances or to changes in the characteristic of components.
Supply voltages, imperfect synchronizing signals, circuits, etc.
kA-Band A higher frequency than Ku-Band, operating
from 18 to 31 gigaHertz.
kHz Kilohertz.
Ku-Band The 11.7-12.7 GHz (Gigahertz) frequency band.
This band has been split into 2 segments by the FCC. The first is the
11.7-12.2 GHz band known as FSS (Fixed Satellite Service)
There are 22 FSS Ku-Band satellites in orbit over North America today.
They range in power from 20-45 watts per transponder, requiring a 3-5
foot antenna for clear reception. The 12.2 - 12.7 GHz segment is known
as BSS (Broadcast Satellite Service). Satellites in this band range
in power from 100 - 200 watts per transponder, allowing the use of receive
antennas as small as 12-18 inches.
L-Band Potion of electromagnetic spectrum commonly
used in satellite and microwave applications with frequencies in the
390 MHz to 1550 MHz range. The GPS (global positioning
system) frequencies are in the L-Band. GPS uses 1227.6 MHz and 1575.42
MHz
LEO Low Earth Orbit; satellites placed in orbit less
than 22,300 miles above the earth.
Light Electromagnetic radiation detectable by the eye,
ranging in wavelength from about 400 to 750 nm.
Line Amplifier An amplifier for audio or video signals
that feeds a transmission line; also called program amplifier.
Line of Sight An unobstructed straight line between
two transmitting devices. Line of sight is typically required for long-range
directional radio transmission. Due to the curvature of the earth, the
line of sight for devices not mounted on towers is limited to 16 miles
(26 km).
LNB Low Noise Block convertor. System devise used to
amplify and convert satellite signals into frequencies sent to the tuner.
Loop Through Also called looping. The method of feeding
a series of high impedance circuits (such as multiple monitor/displays
in parallel) from a pulse or video source with a coax transmission line
in such a manner that the line is bridged (with minimum length stubs)
and that the last unit properly terminates the line in its characteristic
impedance. This minimizes discontinuities or reflections on the transmission
line.
Loss A reduction in signal level or strength, usually
expressed in dB. Power dissipation serving no useful purpose.
Low-Frequency Distortion Distortion effects which occur
at low frequencies. In television, generally considered as any frequency
below the 15.75 kHz line frequency.
Matrix Switcher A device that routes any of its inputs
to any of its outputs. Inputs are normally cameras or alarms, and outputs
are normally recorders or monitors. A matrix switcher allows a user
to control what information is sent where within a large security network.
MHz Megahertz, a measure of frequency in millions (mega)
of cycles per second.
MMDS Multipoint Multi-channel Distribution Service.
MMDS is a way of distributing cable television signals, through microwave,
from a single transmission point to multiple receiving points. Often
used as an alternative to cable-bases cable TV. An MMDS service, "in
digital form, will provide more than 100 channels to a radius of approximately
40 miles from the transmitter. The MMDS transmitter delivers video to
homes that are in its 'line of sight.' MMDS transmissions are limited
by the terrain and foliage of a given market. The microwave signal is
received by an antenna on the subscriber's home, then sent down coaxial
cable to a box atop the customer's TV set. The box decodes and decompresses
the digital signal." MMDS is increasingly being called "Wireless Cable."
Modems Acronym for Modulator/Demodulator. Conventional modems
comprise equipment which converts digital signals to analog signals
and vice versa. Conventional PC modems outputs data in the form of "1's"
and "0's" which are represented by varying levels of voltage. The modem
converts the digital data signal into variations of the analog sine
wave so the data can be transmitted over the device with a digital bit
stream. The modulation techniques include some combination of Amplitude
Modulation (AM), Frequency Modulation (FM) and Phase Modulation (PM),
also known as Phase Shift Keying (PSK). Used in combination, these techniques
allow multiple bits to be represented with a single (or single set)
OF SINE WAVES). In this fashion, compression is accomplished, which
allows more data to be transmitted in the same period of time and which
therefore reduces the connect time and the associated cost of the data
transfer.
Modulation The process of superimposing an information
signal onto a carrier for transmission. The process where some characteristic
of one signal is varied in accordance with another signal. The carrier
may be modulated in three fundamental ways: by varying the amplitude,
called amplitude modulation; by varying the frequency, called frequency
modulation; by varying the phase, called phase modulation. The creation
of a TV channel from a video and audio source for transmission over
a distribution coaxial cable network.
Modulator The electronic equipment required to combine
video and audio signals and convert them to TV radio frequencies (RF)
for distribution to other equipment (including televisions) on a cable
network.
MPEG Motion Pictures Experts Group.
Multiplexer A device that can accept a number of camera
inputs and almost simultaneously display them on a single monitor. Can
be used to transmit multiple cameras over the same transmission medium.
A device that accepts video signals from more than one camera and encodes
them onto one signal that is sent to a digital recorder or VCR. The
multiplexer also decodes the recording so it can play back video from
one camera or several cameras at once on a monitor.
NAB National Association of Broadcasters.
NCTA National Cable Television Association.
Noise The word "noise" originated in audio practice
and refers to random spurts of electrical energy or interference. In
some cases, it will produce a "salt-and-pepper" pattern over the televised
picture. Heavy noise is sometimes referred to as "snow".
NTSC Abbreviation for National Television Systems Committee.
A committee that worked with the FCC in formulating standards for the
present day United States color television system. A television industry
group that develops standards for standard television broadcasting and
receiving equipment in the US.
Off-Air Reception of a TV signal that has been broadcast
through the air by a TV station.
Omni-directional Antenna An antenna having an essentially
non-directional pattern in azimuth, and a directional pattern in elevation.
Output The signal level at the output of an amplifier
or other device.
Packet Data A process where stored data is transmitted in discrete units,
called packets, allowing for more efficient use of channel capacity
and reliability of transfer.
Patch Cords Cables used to interconnect electronic
equipment often terminated with modular or RCA-type plugs.
Patch Panel A panel where circuits are terminated and
facilities provided for interconnecting between circuits by means of
jacks and plugs.
PCS Personal Communications System.
Peak Pulse Amplitude The maximum absolute peak value
of a pulse, excluding those portions considered to be unwanted, such
as spikes.
Peak-to-Peak The amplitude (voltage) difference between
the most positive and the most negative excursions (peaks) of an electrical
signal. A full video signal measures one volt peak to peak.
Personal Video Recorder (PVR) Product that tracks viewing
habits, records programs and has other interactive features such as
pause and rewind.
PIFA Planer Inverted F Antenna.
Polarization In a given direction, the polarization
of the wave radiated by the antenna. Alternatively, the polarization
of a plane wave incident from the given direction which results in maximum
available power at the antenna terminals.
PVR Personal Video Recorder. A consumer device which
uses a hard disk drive to record television programs based on the user's
preferences.
QPSK Quaternary Phase Shift Keying; a digital modulation
scheme used in transmission communications that allows increased sending
capacity
Radiation Pattern (antenna pattern) A graphical representation
of the radiation properties of the antenna as a function of space coordinates.
Radome An enclosure for protecting an antenna from
the harmful effects of its physical environment, generally intended
to leave the electrical performance of the antenna unaffected.
Resolution (horizontal) The amount of resolvable detail
in the horizontal direction in a picture. It is usually expressed as
the number of distinct vertical lines, alternately black and white,
which can be seen in a distance equal to picture height.
RF Radio Frequency The area (or band) of the electromagnetic
spectrum where most radio communication takes place, typically from
100 KHz to 100 GHz. A frequency at which coherent electromagnetic radiation
of energy is useful for communication purposes. Analog electrical signals
sent on cable or over the air. Conventional (broadcast) television and
radio, as well as cable TV, deliver RF signals to your television/radio.
Ripple Amplitude variations in the output voltage of
a power supply caused by insufficient filtering.
Satellite Antenna (Dish) A parabolic antenna that collects
satellite signals. C-Band antennas range in size from 5-12 feet in diameter;
K-Band antennas range from 18 inches to 6 feet.
Satellite Programmer A company that produces, packages
or distributes video, audio, and/or data services for distribution to
the home satellite dish and cable markets.
SCPC Single Channel Per-Carrier; an economical way
to get multiple signals on one transponder.
Scrambling Altering a video signal transmission so
it can not be received without an authorized operating decoder.
Signal Leakage (Leakage) is a cable TV term. Leakage
occurs when certain radio frequencies ooze out of the CATV's coaxial
cable in such strength that they are evident outside the home. They
might be sufficiently strong to interfere with aircraft navigation.
Leakage is really a shielding problem.
Smart Card Technology that allows for the upgrade of
encryption security through the use of a consumer-installable card containing
a new computerized security code.
SMATV Dish & DBS Dish The dish-like antenna used
to receive satellite signals.
SMATV Satellite Master Antenna Television; or private
cable; a miniature cable system that receives programming by one satellite
dish and serves an entire housing complex, hotel or apartment etc.
Splitter A passive device (one with no active electronic
components) which distributes a television signal carried on a cable
in two or more paths and sends it to a number of receivers simultaneously.
Spread Spectrum A means of transmission in which encoded
information is carried in discrete packages of information, then spread
over a wide bandwidth for transmission to specific receivers that filter
out the coded material.
Stubby Antenna A short thick monopole.
Sun Outage When the sun passes behind a satellite in
relation to the earth and its energy momentarily interferes with the
satellite signals. This happens two times each year during spring and
fall equinox.
Superstation A local TV station whose signal is satellite
delivered to cable systems and backyard antennas across the country.
Switcher A simplified SEG that selects and mixes video
signals from two or more sources.
TDMA Time Division Multiple Access is one of several
technologies used in digital wireless transmissions that increases the
efficiency of the network by allowing a greater number of simultaneous
transmissions. Networks using TDMA assign 6 time slots for each frequency
channel. Devices using the wireless network send bursts of information
that are reassembled at the receiving end.
Terrestrial In communications parlance, this refers to earth, land or
ground-based telecommunications systems.
TNC (RP-TNC) A connector type unique to Net WORLD radios
and antennas. Part 15.203 of the FCC rules covering spread-spectrum
devices limits the types of antennas that may be used with transmission
equipment. In compliance with this rule, Net WORLD, like all other wireless
LAN providers, equips its radios and antennas with a unique connector
to prevent attachment of non-approved antennas to radios.
Transceiver A combination transmitter and receiver.
Transients Signals which exist for a brief period of
time prior to the attainment of a steady-state condition. These may
include overshoots, damped sinusoidal waves, etc.
Transponder A satellite component that receives and
retransmits a TV signal or perhaps many narrower-band data or audio
channels.
TVRO (Television Receive-Only) An industry term used
to describe a home satellite system that only receives and does not
transmit satellite television signals.
UHF Ultra High Frequency The part of the radio spectrum
from 470 MHz to 806 MHz, including TV channels 14 through 83.
Uplink To transmit to a satellite for relay; also,
the dish used to transmit.
Vertical Resolution The number of horizontal lines
that can be seen in the reproduced image of a television pattern.
VHF Very High Frequency. The part of the radio spectrum
from 54 to 88 MHz and 174 to 216 MHz, which includes TV channels 2 through
13.
Video Amplifier A wideband amplifier used for passing
picture signals.
Video Band The frequency band width utilized to transmit
a composite video signal.
Video Signal (Non-Composite) The picture signal. A
signal containing visual information and horizontal and vertical blanking
(see also Composite Video Signal) but not sync.
Wireless Transmission A technology in which electronic
devices send information to receivers using radio waves rather than
wiring.
Wireless A system without outside wires, for example
cellular telephony or satellite television.
Zapping Changing the channel by remote control during
a program to avoid a commercial.
Zipping Fast-forwarding through commercials when playing
back a program on a VCR.
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