（单词翻译:单击）
Focal Length - Distance from the exact center of the dish to the center of the feed.
Focal Point - The physical point in space toward which the satellite reflector dish directs the received signal so it can be processed.
Format1 - This is (1) the general makeup2 and organization of a file, or (2) the arrangement of bits of characters within a group.
Forum3 - This is a section of a website or online service, wherein you can communicate with other forum members about a common subject.
Forward - This is the act of redirecting a particular email, an entire email address, or a telephone number.
Forward Error Correction (FEC) - The purpose of this element is to add unique codes to the digital signal at the output source so problems can be detected at the signal receiver.
Freeware - This is software that is free to use and distribute. Some freeware, though, requires that you don't make any changes or alterations4 to the code.
Frequency - The number of times that a wave or wave-like process goes through its complete cycle per second of time. Frequency is measured in hertz (Hz), which is one cycle per second.
Frequency Band - This is a particular band of frequencies in the electromagnetic spectrum5, expressed in Hertz, in which satellite signals are transmitted.
Frequency Coordination6 - A process that is implemented7 to attenuate8 frequency interference between different satellite networks.
Frequency Division Multiplexing - This is an older method of dividing the bandwidth available for transmission into distinct narrow bands for individual transmission channels.
Frequency Modulation9 (FM) - The signal carries the desired information by varying the frequency of the carrier wave.
Frequency Shift Keying (FSK) - This is another modulation technique (see Frequency Modulation) used to transmit data. It shifts the frequency above and below the carrier frequency (representing 1 and 0, respectively).
Frequency Spectrum - This is a range of frequencies (and is similar to bandwidth).
FSK - see Frequency Shift Keying.
Full Duplex - This is the same as Duplex and is simultaneous transmission of data in two opposite directions.
