Jammer
An active electronic counter-measures (ECM) device designed to deny intelligence to unfriendly detectors or to disrupt communications.

JPEG
ISO Joint Picture Expert Group standard for the compression of still pictures.

Ka-Band
The frequency range from 18 to 31 GHz.

Kbps
Kilobits per second. Refers to transmission speed of 1,000 bits per second.

Kelvin (K)
The temperature measurement scale used in the scientific community. Zero K represents absolute zero, and corresponds to minus 459 degrees Fahrenheit or minus 273 Celsius. Thermal noise characteristics of LNA are measured in Kelvins.

Kilohertz (kHz)
Refers to a unit of frequency equal to 1,000 Hertz.

Klystron
A microwave tube which uses the interaction between an electron beam and the RF energy on microwave cavities to provide signal amplification. The klystron operates on principles of velocity modulation very similar to those in a TWT except that klystron interaction takes place at discrete locations along the electron beam. Common types of klystrons are the reflex klystron (an oscillator having only one cavity), two-cavity klystron amplifiers and oscillators, and multi-cavity klystron amplifiers.

Ku-Band
The frequency range from 10.9 to 17 GHz.

L-Band
The frequency range from 0.5 to 1.5 GHz. Also used to refer to the 950 to 1450MHz used for mobile communications.

Leased Line
A dedicated circuit typically supplied by the telephone company.

Low Noise Amplifier (LNA)
This is the preamplifier between the antenna and the earth station receiver. For maximum effectiveness, it must be located as near the antenna as possible, and is usually attached directly to the antenna receive port. The LNA is especially designed to contribute the least amount of thermal noise to the received signal.

Low Noise Block Downconverter (LNB)
A combination Low Noise Amplifier and downconverter built into one device attached to the feed.

MAC (A, B, C, D2)
Multiplexed analog component color video transmission system. Subtypes refer to the various methods used to transmit audio and data signals.

Margin
The amount of signal in dB by which the satellite system exceeds the minimum levels required for operation.

Master Antenna Television (MATV)
An antenna system that serves a concentration of television sets such as in apartment buildings, hotels or motels.

Megahertz (MHz)
Refers to a frequency equal to one million Hertz, or cycles per second.

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.

Microwave Interference
Interference which occurs when an earth station aimed at a distant satellite picks up a second, often stronger signal, from a local telephone terrestrial microwave relay transmitter. Microwave interference can also be produced by nearby radar transmitters as well as the sun itself. Relocating the antenna by only several feet will often completely eliminate the microwave interference.

Modulation
The process of manipulating the frequency or amplitude of a carrier in relation to an incoming video, voice or data signal.

Modulator
A device which modulates a carrier. Modulators are found as components in broadcasting transmitters and in satellite transponders. Modulators are also used by CATV companies to place a baseband video television signal onto a desired VHF or UHF channel. Home video tape recorders also have built-in modulators which enable the recorded video information to be played back using a television receiver tuned to VHF channel 3 or 4.

MPEG
The Moving Pictures Experts Group, the television industry's informal standards group.

MPEG-2
The agreed standard covering the compression of data (coding and encoding) for digital television.

MPEG-2 MP@HL
Main Provile at High Level - The agreed much higher bit-rate system adopted to provide high definition television in wide screen format.

Multicast
Multicast is a subset of broadcast that extends the broadcast concept of one to many by allowing "the sending of one transmission to many users in a defined group, but not necessarily to all users in that group."

Multiplexing
Techniques that allow a number of simultaneous transmissions over a single circuit.

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