F - Foxtrot - di-di-dah-dit
F.
F1B.
FSK telegraphy mode, such as RTTY.
See also: Radio Emissions page.
F3E.
FM mode speech communication.
See also: Radio Emissions page.
F Region or Layer.
A combination of the two highest ionospheric regions, the F1 and F2 regions. The F region refracts radio waves and returns them to Earth. Its height varies greatly depending on the time of day, season of the year and amount of sunspot activity.
Fading.
Signal reduction due to atmospherics.
Facsimile (Fax).
Facsimile machines worked by optical scanning of a document or drawing spinning on a drum. The reflected light, varying in intensity according to the light and dark areas of the document, was focused on a photocell to be converted to an electrical signal varying in frequency. This audio tone was then transmitted. At the receiving end the varying tone was converted into mechanical movement of a pen or pencil to reproduce the image on a blank sheet of paper on an identical drum rotating at the same rate.
See also: Digital Modes page.
False or deceptive signals.
Transmissions that are intended to mislead or confuse those who may receive the transmissions. For example, distress calls transmitted when there is no actual emergency are false or deceptive signals.
FAQ.
Frequently Asked Questions, originally a computer term that is more widely used now.
Farad.
The SI unit of capacitance. It is named after the British physicist Michael Faraday (short history).
The farad is defined as: The capacitance of a dielectric for which a potential difference of one volt results in a static charge of one coulomb.
The farad is a very large unit compared to typical requirements in electronic devices, values of capacitors are usually in range of microfarads (µF), nanofarads (nF), or picofarads (pF). The picofarad is comically called a "puff" in laboratory usage.
Far Field (of an antenna).
The region of the electromagnetic field surrounding an antenna where the field strength as a function of angle (the antenna pattern) is essentially independent of the distance from the antenna. In this region (also called the free-space region), the field has a predominantly plane-wave character. That is, locally uniform distributions of electric field strength and magnetic field strength are in a plane perpendicular to the direction of propagation.
Fast Scan TV (FSTV).
'Home made' Television transmitted in the Amateur band allocation, using the same standards as the analogue Broadcast TV service. In the United Kingdom the 23cm and 13cm bands normally are used.
FCC.
FEC.
Federal Communications Commission (FCC).
The independent United States government agency that regulates all non-Federal Government use of the radio spectrum for interstate telecommunications and international communications that originate or terminate in the United States. The FCC's jurisdiction covers the 50 states, the District of Columbia, and U.S. possessions.
Feed Horn.
A satellite dish and antenna design term, a feedhorn (or feed horn) is a horn antenna used to convey radio waves between the transceiver (transmitter and/or receiver) and the reflector. If combined with the low-noise blockconverter (LNB), the feedhorn is part of an LNBF (low-noise blockconverter feedhorn).
Feed Line.
The wires or cable used to connect a transmitter, receiver or transceiver to an antenna. See Transmission line.
Field Strength Meter.
A simple test instrument used to show the presence of RF energy and the relative strength of the RF field.
Filter.
A circuit that will allow some signals to pass through it but will greatly reduce the strength of others.
Flattopping.
A distorted audio signal produced by an SSB transmitter with the microphone gain set too high. The peaks of the voice waveform are cut off in the transmitter because of overmodulation. Also called clipping.
FM.
FM Deviation.
FM Wide.
Forward Error Correction (FEC).
A system of error control for data transmission, whereby the sender adds redundant data to messages, which allows the receiver to detect and correct errors without the need to ask the sender for additional data. The advantage of FEC is that retransmission of data can often be avoided, at the cost of higher bandwidth requirements on average, and is therefore applied in situations where retransmissions are relatively costly or impossible.
Fox Hunt.
A friendly Amateur Radio competition to locate a hidden transmitter. Amateurs practice their direction-finding, which can be useful in tracking down interference sources.
Frequency.
The number of complete cycles of an alternating current that occur per second.
Frequency Allocation.
A band of radio frequencies identified by an upper and lower frequency limit earmarked for use by one or more of the terrestrial or space radiocommunications services defined by the International Telecommunication Union under specified conditions.
Frequency Allotment.
The designation of portions of an allocated frequency band to individual countries or geographical areas for a particular radiocommunication service; for a satellite service, specific orbital positions may also be alloted to individual countries.
Frequency Assignment.
Authorization given by a nation's government for a station or an operator in that country to use a specific radio frequency channel under specified conditions.
Frequency Bands.
A group of frequencies where amateur communications are authorized.
See : band.
Frequency Coordination.
Allocating repeater input and output frequencies to minimize interference between repeaters and to other users of the band.
Frequency Coordinator.
An individual or group that recommends repeater frequencies to reduce or eliminate interference between repeaters operating on or near the same frequency in the same geographical area.
Frequency Deviation.
1. The amount the carrier frequency in an FM transmitter changes as it is modulated.
See: Deviation page in the Appendix for a full explanation.
.
2. In a transmitter, receiver or transceiver it can be the amount of drift that the VFO has
Frequency Discriminator.
A type of detector used in some FM receivers.
Frequency Drift.
The amount the carrier frequency shifts from the desired or displayed frequency.
Frequency Modulated / Frequency Modulation (FM) telephony.
The type of signals used to communicate by voice (phone) over most repeaters. FM is a method of combining an RF carrier with an information signal, such as voice. The voice information (or data) changes the RF carrier frequency in the modulation process. As you might suspect, we use voice or data to vary the frequency of the transmitted signal. FM broadcast stations and most professional communications use FM. On the VHF & UHF amateur bands FM voice is the most popular amateur mode.
Frequency Privilege.
Permission to use a particular group of frequencies.
Frequency Shift Keying (FSK).
A method of frequency modulation in which the frequency of the transmitted tone switched between two frequencies.
See also: AFSK, MSK, PSK, Digital Modes page.
Frequency Synthesizer.
A programmable VFO circuit which is capable of producing a range of frequencies, usually controlled by a CPU or user input.
Front-end Overload.
Interference to a receiver caused by a strong signal that overpowers the receiver RF amplifier ("front end").
See also Receiver Overload.
Front-to-Back Ratio.
The energy radiated from the front of a directional antenna divided by the energy radiated from the back of the antenna.
FSK.
FSTV.
Full Break In (QSK).
With QSK, an amateur can hear signals between morse code characters. This allows another amateur to break into the communication without waiting for the transmitting station to finish.
Full Duplex.
A mode of communication in which you transmit on one frequency while you simultaneously receive on another frequency.
See also: Duplex Operation, Half Duplex Operation, Simplex Operation.
Full Quieting / Fully Quieting.
(Repeater Term) A phenomenon on FM transmissions where the incoming signal is sufficient to engage the receiver limiters - thus eliminating the noise due to amplitude fluctuations. "You're fully quieting into the box".
Full-Wave Bridge Rectifier.
A full-wave rectifier circuit that uses four diodes and does not require a center-tapped transformer. May be a single component (1) or 4 diodes arranged as in (2)
Schematic symbol: (1)
(2)
Full-Wave Rectifier.
A circuit basically composed of two half-wave rectifiers. The full wave rectifier allows the full ac waveform to pass through; one half of the cycle is reversed in polarity. This circuit requires a center-tapped transformer:
Fuse.
A thin metal strip mounted in a holder. When too much current passes through the fuse, the metal strip melts and opens the circuit.
Schematic symbol: 