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Amplifier
A device used to boost the strength of an electronic signal.

Amplitude Modulation (AM)
The baseband signal is caused to vary the amplitude or height of the carrier wave to create the desired information content.

Analog
A form of transmitting information characterized by continuously variable quantities, as opposed to digital transmission, which is characterized by discrete bits of information in numerical steps. An analog signal is responsive to changes in light, sound, heat and pressure.

Analog-to-Digital Conversion (ADC)
Process of converting analog signals to a digital representation. DAC represents the reverse translation.

ANIK
The Canadian domestic satellite system that transmits Canadian Broadcasting Corporation's (CSC) network feeds throughout the country. This system also carries long distance voice and data services throughout Canada as well as some transborder service to the U.S. and Mexico.

Antenna
A device for transmitting and receiving radio waves. Depending on their use and operating frequency, antennas can take the form of a single piece of wire, a di-pole a grid such as a yagi array, a horn, a helix, a sophisticated parabolic-shaped dish, or a phase array of active electronic elements of virtually any flat or convoluted surface.

Aperture
A cross sectional area of the antenna which is exposed to the satellite signal.

Apogee
The point in an elliptical satellite orbit which is farthest from the surface of the earth. Geosynchronous satellites which maintain circular orbits around the earth are first launched into highly elliptical orbits with apogees of 22,237 miles. When the communication satellite reaches the appropriate apogee, a rocket motor is fired to place the satellite into its permanent circular orbit of 22,237 miles.

Apogee Kick Motor (AKM)
Rocket motor fired to circulate orbit and deploy satellite into geostationary orbit.

Apstar (Asia-Pacific Star)
Name of the Chinese satellite system which carries commercial video services in the region.

Arabsat
This is the Arabsat Satellite Organization and its is headquartered in Riyadh, Saudi Arabia. It provides regional telecommunications services for the Middle East region.

AsiaSat
A satellite system covering the Asia mainland.

Asynchronous Communications
Stream of data routed through a network as generated, rather than in organized message blocks. Most personal computers send data in this format. (See ATM)

Asynchronous Transfer Mode (ATM)
This is the new form of super-fast packet switching operating at speeds in the Gigabits/second.

Attenuation
The loss in power of electromagnetic signals between transmission and reception points.

Attitude Control
The orientation of the satellite in relationship to the earth and the sun.

Audio Subcarrier
The carrier between 5 MHz and 8 MHz containing audio (or voice) information inside of a video carrier.

Automatic Frequency Control (AFC)
A circuit which automatically controls the frequency of a signal.

Automatic Gain Control (AGC)
A circuit which automatically controls the gain of an amplifier so that the output signal level is virtually constant for varying input signal levels.

AZ/EL Mount
Antenna mount that requires two separate adjustments to move from one satellite to another;

Azimuth
The angle of rotation (horizontal) that a ground based parabolic antenna must be rotated through to point to a specific satellite in a geosynchronous orbit. The azimuth angle for any particular satellite can be determined for any point on the surface of the earth giver the latitude and longitude of that point. It is defined with respect to due north as a matter of easy convenience.