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Amateur Radio Glossary

Amateur Radio Glossary

Amateur operator: A person holding a written authorization to be the control operator of an amateur station.

Amateur service: A radio communication service for the purpose of self-training, intercommunication, and technical investigations carried out by amateurs, that is, duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.

Amateur station: A station licensed in the amateur service, including neces­sary equipment, used for amateur communication.

Ammeter: A test instrument that measures current.

Ampere (A): The basic unit of electrical current. Current is a measure of the electron flow through a circuit. If you count electrons, 6.24 × 1018 electrons moving past a point in one second equal a current of one ampere. Abbreviated as amps. (Numbers written as a multiple of some power are expressed in exponential notation, as shown here.)

Amplitude modulation (AM): A method of combining an information signal and an RF (radio-frequency) carrier. In voice AM transmission, the voice infor­mation can vary (modulate) the amplitude of an RF carrier. Shortwave broad­cast stations use this type of AM, as do stations in the Standard Broadcast Band (535 to 1710 kHz). A variation of AM, known as single sideband, is very popular.

Antenna: A device that picks up or sends out radio frequency energy.

Antenna switch: A switch that connects one transmitter, receiver, or trans­ceiver to several different antennas.

Antenna tuner: A device that matches the antenna system input impedance to the transmitter, receiver, or transceiver output impedance. Also called an antenna-matching network, impedance-matching network, or Transmatch.

Autopatch: A device that allows repeater users to make telephone calls through a repeater

Balun: Contraction for balanced to unbalanced. A device to couple a balanced load to an unbalanced source, or vice versa.

Band spread: A receiver quality that describes how far apart stations on dif­ferent nearby frequencies seem to be. Usually expressed as the number of kilohertz that the frequency changes per tuning-knob rotation. The amount of band spread determines how easily signals can be tuned. Band-pass filter: A circuit that allows signals to go through it only if the sig­nals are within a certain range of frequencies. It attenuates signals above and below this range.

Bandwidth: The width of a frequency band outside of which the mean power is attenuated at least 26dB below the mean power of the total emission, including allowances for transmitter drift or Doppler shift. Bandwidth describes the range of frequencies that a radio transmission occupies. Battery: A device that converts chemical energy into electrical energy.

Beacon station: An amateur station transmitting communications for the purposes of observation of propagation and reception or other related exper­imental activities.

Beam antenna: A directional antenna. A beam antenna must be rotated to provide its strongest coverage in different directions. Beat-frequency oscillator (BFO): A receiver circuit that provides a signal to the detector. The BFO signal mixes with the incoming signal to produce an audio tone for CW reception. A BFO is needed to copy CW and SSB signals. Broadcasting: Transmissions intended to be received by the general public, either direct or relayed.

Capacitor: An electrical component usually formed by separating two con­ductive plates with an insulating material. A capacitor stores energy in an electric field.

Chirp: A slight shift in transmitter frequency each time you key the transmitter.

Closed repeater: A repeater that restricts access to those who know a special code.

Coaxial cable (Coax): Pronounced kó-aks. A type of feedline with one conduc­tor inside the other.

Continuous wave (CW): Morse code telegraphy.

Control operator: An amateur operator designated by the licensee of a station to be responsible for the transmissions of an amateur station.

Control point: The locations at which the control operator functions are performed.

Courtesy tone: A tone or beep transmitted by a repeater to indicate that the next station can begin transmitting. The courtesy tone is designed to allow a pause between transmissions on a repeater, so other stations can call. It also indicates that the time-out timer has been reset.

CQ: The general call when requesting a conversation with anyone — “Calling any station.”

Crystal oscillator: A device that uses a quartz crystal to keep the frequency of a transmitter constant.

Crystal-controlled transmitter: A simple type of transmitter that consists of a crystal oscillator followed by driver and power amplifier stages.

CTCSS (Continuous Tone Coded Squelch System): A sub-audible tone system used on some repeaters. When added to a carrier, a CTCSS tone allows a receiver to accept a signal. Also called PL.

Cubical quad antenna: An antenna built with its elements in the shape of four-sided loops.

Current: A flow of electrons in an electrical circuit.

CW (Morse code): A communications mode transmitted by on/off keying of a radio-frequency signal. Another name for international Morse code.

D region: The lowest region of the ionosphere. The D region contributes very little to shortwave radio propagation. It acts mainly to absorb energy from radio waves as they pass through it. This absorption has a significant effect on sig­nals below about 7.5 MHz during daylight.

Data: Computer-based communications modes, such as packet radio, which can be used to transmit and receive computer files, or digital information.

DE: The Morse code abbreviation for “from” or “this is.”

Delta loop antenna: A variation of the cubical quad with triangular elements.

Digipeater: A packet-radio station used to retransmit signals that are specifi­cally addressed to be retransmitted by that station.

Digital communications: Computer-based communications modes. These modes can include data modes, such as packet radio, and text-only modes like radioteletype (RTTY). Dipole antenna: See 1⁄2-wave dipole. A dipole not 1⁄2 wavelength long is called a “doublet.”

Director: An element in front of the driven element in a Yagi antenna and some other directional antennas.

Driven element: The part of an antenna that connects directly to the feedline. Dual-band antenna: An antenna designed for use on two different Amateur Radio bands.

Dummy antenna: A station accessory that allows you to test or adjust trans­mitting equipment without sending a signal out over the air. Also called dummy load.

Dummy load: See Dummy antenna. A device that allows a dual-band radio to use a single dual-band antenna.

Duty cycle: A measure of the amount of time a transmitter is operating at full output power during a single transmission. A lower duty cycle means less RF radiation exposure for the same PEP output.

DX: Distant, foreign countries.

E region: The second lowest ionospheric region, the E region exists only during the day. Under certain conditions, it may refract radio waves enough to return them to Earth.

Earth ground: A circuit connection to a ground rod driven into the Earth or to a cold-water pipe made of copper that goes into the ground.

Earth station: An amateur station located on, or within 50 kilometers of, the Earth’s surface intended for communications with space stations or with other Earth stations by means of one or more other objects in space.

Earth-Moon-Earth (EME) or Moonbounce: A method of communicating with other stations by reflecting radio signals off the moon’s surface.

Electron: A tiny, negatively charged particle, normally found in an area surrounding the nucleus of an atom. Moving electrons make up an electrical current.

Emergency traffic: Messages with life and death urgency or requests for med­ical help and supplies that leave an area shortly after an emergency.

Emission: The transmitted signal from an amateur station.

Emission privilege: The permission granted by your license to use a particular emission type (such as Morse code or voice).

Emission types: Term for the different modes authorized for use on the Ama­teur Radio bands. Examples are CW, SSB, RTTY, and FM.

F region: 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.

False or deceptive signals: Transmissions intended to mislead or confuse those who may receive the transmissions. For example, transmitting distress calls with no actual emergency are false or deceptive signals.

Feedline: The wires or cable used to connect a transmitter, receiver, or trans­ceiver to an antenna. See Transmission line. Filter: A circuit that allows some signals to pass through it but greatly reduces the strength of others.

“Five-Nine”: A common signal report on voice that means “Your signal is strong and easy to understand.” The equivalent on CW or Morse code is “599.” See also Signal Report.

Frequency: The number of complete cycles of an alternating current that occur per second.

Frequency bands: A group of frequencies where amateur communications are authorized.

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 discriminator: A type of detector used in some FM receivers.

Frequency modulated (FM) phone: 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 (see Amplitude modulation). Voice or data vary the frequency of the transmitted signal. FM broadcast stations and most professional communications (police, fire, taxi) use FM. VHF/UHF FM voice is the most popular amateur mode.

Frequency privilege: The permission granted by your license to use a partic­ular group of frequencies. Front-end overload: Interference to a receiver caused by a strong signal that overpowers the receiver RF amplifier (front end). See also receiver overload.

General-coverage receiver: A receiver used to listen to a wide range of fre­quencies. Most general-coverage receivers tune from frequencies below the standard-broadcast band to at least 30 MHz. These frequencies include the shortwave-broadcast bands and the amateur bands from 160 to 10 meters.

Grace period: The time the FCC allows following the expiration of an amateur license to renew the license without having to retake an examination. Hams holding an expired license may not operate an amateur station until the license is reinstated.

Ground connection: A connection made to the Earth for electrical safety. You can make this connection inside (to a metal cold-water pipe) or outside (to a ground rod).

Ground rod: A copper or copper-clad steel rod driven into the Earth. A heavy copper wire from the ham shack connects all station equipment to the ground rod.

Ground-wave propagation: The method by which radio waves travel along the Earth’s surface.

Half-wave dipole: A basic antenna used by radio amateurs. It consists of a length of wire or tubing, opened and fed at the center. The entire antenna is 1⁄2 wavelength long at the desired operating frequency.

Ham-bands-only receiver: A receiver designed to cover only the bands used by amateurs. Usually refers to the bands from 80 to 10 meters, sometimes including 160 meters.

Harmonics: Signals from a transmitter or oscillator occurring on whole-number multiples (2_, 3_, 4_) of the desired operating frequency. Health and Welfare traffic: Messages about the well being of individuals in a disaster area. Such messages must wait for Emergency and Priority traffic to clear, and results in advisories to those outside the disaster area awaiting news from family and friends.

Hertz (Hz): An alternating-current frequency of one cycle per second. The basic unit of frequency.

High-pass filter: A filter designed to pass high-frequency signals, while block­ing lower-frequency signals. Impedance-matching device: See Antenna Tuner.

Input frequency: A repeater’s receiving frequency. To use a repeater, transmit on the input frequency and receive on the output frequency.

Intermediate frequency (IF): The output frequency of a mixing stage in a superheterodyne receiver. The subsequent stages in the receiver are tuned for maximum efficiency at the IF.

Ionizing radiation: Electromagnetic radiation that has sufficient energy to knock electrons free from their atoms, producing positive and negative ions. X-rays, gamma rays, and ultraviolet radiation are examples of ionizing radiation.

Ionosphere: A region of electrically charged (ionized) gases high in the atmos­phere. The ionosphere bends radio waves as they travel through it, returning them to Earth. See also Sky-wave Propagation.

K: The Morse code abbreviation for “any station respond.”

Lightning protection: You can help prevent lightning damage to your equip­ment (and your house) in several ways, among them unplugging equipment, disconnecting antenna feedlines, and using a lightning arrestor.

Limiter: A stage of an FM receiver that makes the receiver less sensitive to amplitude variations and pulse noise.

Line-of-sight propagation: The term used to describe VHF and UHF propaga­tion in a straight line directly from one station to another.

Lower sideband (LSB): The common single-sideband operating mode on the 40, 80, and 160-meter amateur bands.

Low-pass filter: A filter that allows signals below the cutoff frequency to pass through and attenuates signals above the cutoff frequency. Malicious (harmful) interference: Intentional, deliberate obstruction of radio transmissions.

Maximum useable frequency (MUF): The highest-frequency radio signal that reaches a particular destination using sky-wave propagation, or skip. The MUF may vary for radio signals sent to different destinations.

MAYDAY: From the French m’aidez (help me), MAYDAY is used when calling for emergency assistance in voice modes.

Microphone: A device that converts sound waves into electrical energy.

Mobile device: A radio transmitting device that you can mount in a vehicle. A push-to-talk (PTT) switch activates the transmitter.

Modem: Short for modulator/demodulator. A modem modulates a radio signal to transmit data and demodulates a received signal to recover transmitted data.

Modulate: To vary the amplitude, frequency, or phase of a radio-frequency signal.

Modulation: The process of varying an RF carrier in some way (the amplitude or the frequency, for example) to add an information signal to be transmitted.

Monitor mode: One type of packet radio receiving mode. In monitor mode, everything transmitted on a packet frequency is displayed by the monitoring TNC. The data is displayed whether or not the transmissions are addressed to the monitoring station.

Morse code: See CW.

Multimode transceiver: Transceiver capable of SSB, CW, and FM operation.

National Electrical Code: A set of guidelines governing electrical safety, including antennas.

Network: A term used to describe several packet stations linked together to transmit data over long distances.

Nonionizing radiation: Electromagnetic radiation that does not have sufficient energy to knock electrons free from their atoms. Radio frequency (RF) radia­tion is nonionizing.

Offset: For CW operation, the 300 to 1000-Hz difference in transmitting and receiving frequencies in a transceiver. For a repeater, offset refers to the dif­ference between its transmitting and receiving frequencies.

One-way communications: Transmissions not intended to be answered. The FCC strictly limits the types of one-way communications allowed on the ama­teur bands.

Open repeater: A repeater used by all hams who have a license that authorizes operation on the repeater frequencies.

Operator/primary station license: An amateur license actually includes two licenses in one. The operator license is that portion of an Amateur Radio license that gives permission to operate an amateur station. The primary sta­tion license is that portion of an Amateur Radio license that authorizes an amateur station at a specific location. The station license also lists the call sign of that station.

Output frequency: A repeater’s transmitting frequency. To use a repeater, transmit on the input frequency and receive on the output frequency.

Packet radio: A system of digital communication whereby information is broken into short bursts. The bursts (packets) also contain addressing and error-detection information.

Parasitic beam antenna: See Beam Antenna.

Parasitic element: Part of a directive antenna that derives energy from mutual coupling with the driven element. Parasitic elements are not connected directly to the feedline.

Peak envelope power (PEP): The average power of a signal at its largest ampli­tude peak.

Pecuniary: Payment of any type, whether money or other goods. Amateurs may not operate their stations in return for any pecuniary.

Phone: Another name for voice communications.

Phone emission: The FCC name for voice or other sound transmissions.

Phonetic alphabet: Standard words used on voice modes, which make under­standing letters of the alphabet easier, such as those in call signs. The call sign KA6LMN stated phonetically is Kilo Alfa Six Lima Mike November.


Polarization: The electrical-field characteristic of a radio wave. An antenna parallel to the surface of the Earth, such as a dipole, produces horizontally polarized waves. An antenna perpendicular to the Earth’s surface, such as a 1⁄4-wave vertical, produces vertically polarized waves. An antenna with both horizontal and vertical polarization is circularly polarized.

Portable device: A radio transmitting device designed to have a transmitting antenna that is generally within 20 centimeters of a human body.

Priority traffic: Emergency-related messages, but not as important as Emer­gency traffic.

Procedural signal (prosign): One or two letters sent as a single character. Ama­teurs use prosigns in CW contacts as a short way to indicate the operator’s intention. Some examples are K for “Go Ahead,” or AR for “End of Message.” Product detector: A device that allows a receiver to process CW and SSB signals.

Propagation: The study of how radio waves travel.

Q signals: Three-letter symbols beginning with Q. Used on CW to save time and to improve communication. Some examples are QRS (send slower), QTH (location), QSO (ham conversation), and QSL (acknowledgment of receipt).

QRL?: Ham radio Q signal meaning “Is this frequency in use?”

QRP: Ham radio Q signal meaning “Low Power.” QRP generally means to 5 watts of transmitted power on CW or 10 watts of peak power on phone. QRPp means power less than 1 watt.

QSL card: A postcard that serves as a confirmation of communication between two hams.

QSO: A conversation between two radio amateurs. Quarter -wavelength vertical antenna: An antenna constructed of a 1⁄4-wavelength long radiating element placed perpendicular to the Earth.

Radio Amateur Civil Emergency Service (RACES): A part of the Amateur Service that provides radio communications for civil preparedness organiza­tions during local, regional, or national civil emergencies.

Radio-frequency interference (RFI): Disturbance to electronic equipment caused by radio-frequency signals.

Radioteletype (RTTY): Radio signals sent from one teleprinter machine to another machine. Anything that one operator types on his teleprinter prints on the other machine.

Receiver: A device that converts radio waves into signals you can hear or see.

Receiver incremental tuning (RIT): A transceiver control that allows for a slight change in the receiver frequency without changing the transmitter fre­quency. Some manufacturers call this control a clarifier (CLAR) control.

Receiver overload: Interference to a receiver caused by a strong RF signal that forces its way into the equipment. A signal that overloads the receiver RF amplifier (front end) causes front-end overload. Receiver overload is sometimes called RF overload.

Reflection: Signals that travel by line-of-sight propagation are reflected by large objects, such as buildings.

Reflector: An element behind the driven element in a Yagi antenna and other directional antennas.

Repeater station: An amateur station that automatically retransmits the signals of other stations.

RF burn: A burn produced by coming in contact with exposed RF voltages.

RF carrier: A steady radio frequency signal that is modulated to add an infor­mation signal to be transmitted. For example, a voice signal is added to the RF carrier to produce a phone emission signal.

RF overload: Another term for receiver overload.

RF radiation: Waves of electric and magnetic energy. Such electromagnetic radiation with frequencies as low as 3 kHz and as high as 300 GHz are consid­ ered part of the RF region.

RF safety: Preventing injury or illness to humans from the effects of radio- frequency energy.

Rig: The radio amateur’s term for a transmitter, receiver, or transceiver.

RST: A system of numbers used for signal reports: R is readability, S is strength, and T is tone. (On single-sideband phones, only R and S reports are used.)

Selectivity: The ability of a receiver to separate two closely spaced signals.

Sensitivity: The ability of a receiver to detect weak signals. 73: Ham lingo for “best regards.” Used on both phone and CW toward the end of a contact. Shack: The room where an Amateur Radio operator keeps his or her station equipment.

Sidebands: The sum or difference frequencies generated when an RF carrier mixes with an audio signal. Single-sideband phone (SSB) signals have an upper sideband (USB) and a lower sideband (LSB). SSB transceivers allow operation on either USB or LSB. See also USB and LSB. Signal report: A set of numbers that are exchanged to indicate the relative quality of a signal’s quality in terms of strength, clarity, and purity (see RST).

Simplex operation: Receiving and transmitting on the same frequency.

Single Sideband (SSB) phone: A common mode of voice operation on the ama­teur bands. SSB is a form of amplitude modulation. The amplitude of the trans­mitted signal varies with the voice signal variations.

Skip zone: An area of poor radio communication that is too distant for ground waves and too close for sky waves.

Sky-wave propagation: The method radio waves travel through the ionosphere and back to Earth. Sometimes called skip, sky-wave propagation has a far greater range than line-of-sight and ground-wave propagation.

SOS: A Morse code call for emergency assistance.

Space station: An amateur station located more than 50 km above the Earth’s surface.

Specific absorption rate (SAR): A term that describes the rate RF energy is absorbed into the human body. Maximum permissible exposure (MPE) limits are based on whole-body SAR values.

Splatter: A type of interference to stations on nearby frequencies. Splatter occurs when a transmitter is overmodulated.

Spurious emissions: Signals from a transmitter on frequencies other than the operating frequency.

Standing-wave ratio (SWR): Sometimes called voltage standing-wave ratio (VSWR). A measure of the impedance match between the feedline and the antenna. Also, with a Transmatch in use, a measure of the match between the feedline from the transmitter and the antenna system. The system includes the Transmatch and the line to the antenna. VSWR is the ratio of maximum voltage to minimum voltage along the feedline. Also the ratio of antenna impedance to feedline impedance when the antenna is a purely resistive load.

Station grounding: Connecting all station equipment to a good Earth ground improves both safety and station performance. Sunspot cycle: The number of sunspots increases and decreases in a pre­dictable cycle that lasts about 11 years.

Sunspots: Dark spots on the surface of the sun. With a few sunspots, long-distance radio propagation is poor on the higher-frequency bands. With many sunspots, long-distance HF propagation improves.

 SWR meter: A measuring instrument that indicates when an antenna system is working well. A device used to measure SWR (see Standing-wave ratio).

Tactical call signs: Names used to identify a location or function during local emergency communications.

Teleprinter: A machine that can convert keystrokes (typing) into electrical impulses. The teleprinter also converts the proper electrical impulses back into text. Computers have largely replaced teleprinters for amateur radiotele­type work.

Television interference (TVI): Interruption of television reception caused by another signal.

Temperature inversion: A condition in the atmosphere in which a region of cool air is trapped beneath warmer air. Temporary state of communications emergency: When a disaster disrupts normal communications in a particular area, the FCC can declare this type of emergency. Certain rules may apply for the duration of the emergency.

Terminal: An inexpensive piece of equipment used in place of a computer in a packet radio station. Third-party communications: Messages passed from one amateur to another on behalf of a third person.

Third-party communications agreement: An official understanding between the United States and another country that allows amateurs in both countries to participate in third-party communications.

Third-party participation: The way an unlicensed person can participate in amateur communications. A control operator must ensure compliance with FCC rules.

Ticket: A common name for an Amateur Radio license. Time-out timer: A device that limits the amount of time any one person can talk through a repeater.

Transceiver: A radio transmitter and receiver combined in one unit. Transmission line: The wires or cable used to connect a transmitter or receiver to an antenna. Also called a feedline.

Transmitter: A device that produces radio-frequency signals.

Troposphere: The region in the Earth’s atmosphere just above the Earth’s surface and below the ionosphere.

Tropospheric bending: When radio waves are bent in the troposphere, they return to Earth farther away than the visible horizon.

Tropospheric ducting: A type of VHF propagation that occurs when warm air overruns cold air (a temperature inversion).

Unbalanced line: A feedline with one conductor at ground potential, such as a coaxial cable.

Uncontrolled environment: Any area in which an RF signal may cause radia­tion exposure to people who may not be aware of the radiated electric and magnetic fields. The FCC generally considers members of the general public and an amateur’s neighbors to be in an uncontrolled RF radiation exposure environment to determine the maximum permissible exposure levels.

Unidentified communications or signals: Signals or radio communications in which the transmitting station’s call sign is not transmitted.

Upper sideband (USB): The common single-sideband operating mode on the 20, 17, 15, 12, and 10-meter HF amateur bands, and all the VHF and UHF bands.

Vertical antenna: A common amateur antenna, often made of metal tubing. The radiating element is vertical. Usually four or more radial elements are parallel to or on the ground.

VFO: Variable Frequency Oscillator — the circuit in a receiver or transmitter that controls the operating frequency.

Visible horizon: The most distant point you see by line of sight. Voice: Any of the several methods used by amateurs to transmit speech.

Voice communications: Hams can use several voice modes, including FM and SSB.

Wavelength: Often abbreviated l. The distance a radio wave travels in one RF cycle. The wavelength relates to frequency. Higher frequencies have shorter wavelengths.

Yagi antenna: The most popular type of amateur directional (beam) antenna. It has one driven element and one or more additional elements


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