30 Glossary: A-C
Description
This article is from the TeleVision Receive Only Satellite-TV FAQ, by TVRO Hobbyists drlev@hotmail.com with numerous contributions by others.
30 Glossary: A-C
Addressability: Remote-control function of equipment that allows a
program distributor to activate, disconnect or unscramble the signal
received by a subscriber.
Analog: A format in which information is transmitted by modulating a
continuous signal, such as a radio wave.
Antenna: (communications usage) The basic element of a satellite
receive site; a parabolic dish-shaped device that is either fixed
(locked onto a particular satellite), steerable (able to "look at"
more than one satellite of the same sort), or even dual (able to
receive both C- and Ku-Band signals, one at a time or both
simultaneously).
Aspect Ratio: The ratio of a television screen's width to its height,
the standard being a 4:3 ratio. Projection equipment may produce a
variance from this standard.
Attenuation: (communications usage) Signal strength loss between the
transmission and reception points. For example: Heavy rainstorms can
cause microwave signals to seem to fade, i.e., to attenuate, as the
rainstorm passes through an area.
Audio Subcarrier: The audio signal that is part of a video
transmission is carried on a specific frequency (above the visual
signal), known as a sub-carrier, which can be either on one or more
channels.
Azimuth: The angle between an antenna's beam and the meridian plane,
measured along the horizon. Along with "elevation," azimuth is a
coordinate used to precisely point an antenna at a particular
satellite.
Backhaul: 1. A point-to-point transmission in real-time from a remote
site to the mix point or to the network distribution center. 2. To
send a program from a remote site to the network operations center for
real-time distribution.
Bandwidth: A measure of the information capacity in the frequency
domain. The greater the bandwidth, the more information it can
carry. For example, television signals require a bandwidth of 3
million hertz, while telephone conversation needs only 3,000 hertz.
C-Band: Frequency range from approximately 4 to 6 gigahertz (billion
cycles per second) used by communications satellites.
Component Video: A method of generating television images, either
analog or digital, where the information is carried in separate
signals representing the red, blue, green and brightness of the
televised scene, and combined into a master signal before transmission
to the viewer.
Composite Video: A method of generating television images in which
color and brightness are combined into a signal. Any single signal is
comprised of several components.
Component vs. Composite: (video usage) In composite video, all the
elements in a television signal-sync, color, audio, etc.-travel
together and interfere with each other in slight, almost imperceptible
ways. Conversely, in component video, the signal is broken down into
parts traveling separately. Because there is no chance for
interference between the components, a higher quality video results.
Compressed Video: Technology which makes it possible to transmit
multiple high quality television signals simultaneously in the amount
of bandwidth previously needed to carry only a single television
signal.
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