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Carrier To Noise Ratio
The ratio of the received carrier power and the noise power in a given bandwidth, expressed in dB. This figure is directly related to G/T and S/N; and in a video signal the higher the C/N, the better the received picture.
Subcarrier
A second signal "piggybacked" onto a main signal to carry additional information. In television transmission, the video picture is transmitted over the main carrier. The corresponding audio is sent via an FM subcarrier.
Interference
Energy which tends to interfere with the reception of the desired signals, such as fading from airline flights, RF interference from adjacent channels, or ghosting from reflecting objects such as mountains and buildings.
Hertz
The name given to the basic measure of radio frequency characteristics. a An electromagnetic wave completes a full oscillation from its positive to its negative pole and back again in what is known as a cycle. A single Hertz is thus equal to one cycle per second.
VSWR
Voltage Standing Wave Ratio. A measurement of mismatch in a cable, wave guide, or antenna system.
MPEG
The Moving Pictures Experts Group, the television industry's informal standards group.
Microwave
Line-of sight, point-to-point transmission of signals at high frequency. Many CATV systems receive some television signals from a distant antenna location with the antenna and the system connected by microwave relay. Microwaves are also used for data, voice, and indeed all types of information transmission. The growth of fiber optic networks have tended to curtail the growth and use of microwave relays. Modulation The process of manipulating the frequency or amplitude of a carrier in relation to an incoming video, voice or data signal.
Frequency
The number of times that an alternating current goes through its complete cycle in one second of time. One cycle per second is also referred to as one hertz; 1000 cycles per second, one kilohertz; 1,000,000 cycles per second, one megahertz: and 1,000,000,000 cycles per second, one gigahertz.
Channel
A frequency band in which a specific broadcast signal is transmitted. Channel frequencies are specified in the United States by the Federal Communications Commission. Television signals require a 6 MHz frequency band to carry all the necessary picture detail.
Carrier Frequency
The main frequency on which a voice, data, or video signal is sent. Microwave transmitters operate in the band from 0.3 to 300 GHz (a GHz is one billion cycles per second).
Carrier
The basic radio, television, or telephony center of frequency transmit signal. The carrier in an analog signal. is modulated by manipulating its amplitude (making it louder or softer) or its frequency (shifting it up or down) in relation to the incoming signal.
Bandwidth
A measure of spectrum (frequency) use or capacity. For instance, a voice transmission by telephone requires a bandwidth of about 3000 cycles per second (3KHz). A TV channel occupies a bandwidth of 6 million cycles per second (6 MHz).
Band Pass Filter
An active or passive circuit which allows signals within the desired frequency band to pass through but impedes signals outside this pass band from getting through.
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.
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.
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