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FCC (Federal Communications Commission)
The U.S. federal regulatory body, consisting of five members, one of who is designated chairman, appointed by the President and confirmed by the Senate, which regulates interstate communications under the Communications Act of 1934.

F/D
Ratio of antenna focal length to antenna diameter. A higher ratio means a shallower dish.

FDMA
Frequency division multiple access. Refers to the use of multiple carriers within the same transponder where each uplink has been assigned frequency slot and bandwidth. This is usually employed in conjunction with Frequency Modulation.

Feed
This term has at least two key meanings within the field of satellite communications. It is used to describe the transmission of video programming from a distribution center. It is also used to describe the feed system of an antenna. The feed system may consist of a subreflector plus a feedhorn or a feedhorn only.

Feedhorn
A satellite TV receiving antenna component that collects the signal reflected from the main surface reflector
and channels this signal into the low-noise amplifier (LNA).

FM - Frequency Modulation
A modulation method whereby the baseband signal varies the frequency of the carrier wave.

FM Threshold
That point at which the input signal power is just strong enough to enable the receiver demodulator circuitry successfully to detect and recover a good quality television picture from the incoming video carrier.

Focal Length
Distance from the center feed to the center of the dish.

Focal Point
The area toward which the primary reflector directs and concentrates the signal received.

Footprint
A map of the signal strength showing the EIRP contours of equal signal strengths as they cover the earth's surface. Different satellite transponders on the same satellite will often have different footprints of the signal strength. The accuracy of EIRP footprints or contour data can improve with the operational age of the satellite. The actual EIRP levels of the satellite, however, tends to decrease slowly as the spacecraft ages.

Forward Error Correction (FEC)
Adds unique codes to the digital signal at the source so errors can be detected and corrected at the receiver.

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.

Frequency Coordination
A process to eliminate frequency interference between different satellite systems or between terrestrial microwave systems and satellites. In the U.S. this activity relies upon a computerized service utilizing an extensive database to analyze potential microwave interference problems that arise between organizations using the same microwave band. As the same C-band frequency spectrum is used by telephone networks and CATV companies when they are contemplating the installation of an earth station, they will often obtain a frequency coordination study to determine if any problems will exist.

Frequency Reuse
A technique which maximizes the capacity of a communications satellite through the use of spe
cially isolated beam antennas and/or the use of dual polarities.


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