（单词翻译:单击）
Fade - This is a reduction in the received signal. It is caused by absorption, refraction, or reflection.
Fax - This is a shortening of Facsimile, and it refers to one fax machine sending a digital representation of a hardcopy over the phone lines to be received and printed out by another fax machine.
FCC - see Federal Communications Commission
F/D - the ratio of antenna1's focal length to the antenna's diameter. If there is a greater F/D it means there is a shallower dish.
FDM - see Frequency Division Multiplexing.
Feature - This term refers to any of the tasks that a particular piece of equipment can perform or carry out.
Feed - this (1) describes the physical feed system of the antenna, and (2) describes the actual signal transmission of the data or information from the distributors.
Feedback - This occurs when part of the output signal returns to the input2 side of the electronic device.
Federal Communications Commission (FCC) - This is the government agency that regulates all interstate communications that originate within the United States. The FCC has no intrastate authority.
Field - This refers to the particular location of a piece of data within a record (which is within a file of a database).
File - This term refers to any intended collection of data with similar characteristics. A file could be anything from a document to a component3 of a computer program.
Filter - This is a device which allows a particular spectrum4 (range of frequencies) to pass through it but prohibits (attenuates) all others from passing.
Firewall - This is a system of both software and hardware, and it has purpose of limiting the vulnerability of a computer or set of computers from outside attack (i.e., hacking).
Flash - This is a function on a telephone or other phone device that rapidly hangs-up and reconnects the telephone line.
Flag - In programming, this is a variable that is used to relay when a particular condition of the program has been met.
Flow Control - This is a method of controlling the transfer of information (messages, characters, etc.) between a network's data points.
