Hangar Academy
Technical Glossary
Aviation and marine electronics terminology — free reference for all professionals.
A
ADFAutomatic Direction Finder. An aircraft radio navigation instrument that senses the direction to an NDB (Non-Directional Beacon).
ATISAutomatic Terminal Information Service. A continuous broadcast of recorded non-control information at busy airports including weather and active runways.
B
BNCBayonet Neill-Concelman connector. A quick-connect RF connector commonly used on test equipment and some aviation electronics.
C
Coaxial CableA type of transmission line consisting of a center conductor, dielectric insulator, outer conductor (shield), and jacket. Used to carry RF signals with low loss.
CTAFCommon Traffic Advisory Frequency. Used for pilot-to-pilot communications at airports without an operating control tower.
D
dBDecibel. A logarithmic unit used to express the ratio of two values, commonly power or amplitude. 3 dB represents a doubling of power.
dBmDecibels relative to one milliwatt. Used to express absolute power levels. 0 dBm = 1 mW, 30 dBm = 1 W.
DMEDistance Measuring Equipment. An aviation navigation system that measures slant-range distance between an aircraft and a ground station.
DMEDistance Measuring Equipment. An aviation navigation system that measures slant-range distance between an aircraft and a ground station.
DSCDigital Selective Calling. An automated system that allows mariners to send distress alerts and establish communications. Operates on Channel 70 for VHF.
E
ELTEmergency Locator Transmitter. An aircraft device that transmits a distress signal on 406 MHz when activated by crash impact.
EPIRBEmergency Position Indicating Radio Beacon. A float-free device that transmits a distress signal to satellites on 406 MHz when a vessel sinks.
ERPEffective Radiated Power. The total power radiated by an antenna system, accounting for transmitter power, feedline losses, and antenna gain.
F
FrequencyThe number of complete cycles per second of a radio wave, measured in Hertz (Hz). Higher frequency means shorter wavelength.
G
GainThe ability of an antenna to direct radiated power in a specific direction compared to a reference antenna, expressed in dBi or dBd.
GMDSSGlobal Maritime Distress and Safety System. An internationally agreed set of safety procedures, equipment, and communication protocols for maritime distress.
I
ILSInstrument Landing System. A precision approach system consisting of a localizer (horizontal guidance) and glideslope (vertical guidance).
ImpedanceOpposition to current flow in an AC circuit, measured in ohms. In RF systems, impedance matching between components is critical to minimize signal loss.
Insertion LossSignal power lost as it passes through a component or feedline, expressed in dB. Lower is better.
N
N-TypeA threaded RF connector rated for frequencies up to 11 GHz. Used in high-frequency and high-power applications.
O
OTDROptical Time Domain Reflectometer. A fiber optic test instrument that sends light pulses into a fiber and measures reflections to identify faults.
P
PL-259A common RF connector used on VHF and HF equipment. Also called the UHF connector despite being commonly used at VHF frequencies.
PolarizationThe orientation of the electric field of a radio wave. Common types include vertical, horizontal, and circular polarization.
R
Radar SpokesRadial interference patterns on a weather radar display caused by interference from another radar source operating at a similar frequency.
Return LossThe ratio of reflected power to incident power, expressed in dB. Higher return loss (more dB) indicates better impedance matching.
S
SARTSearch and Rescue Transponder. A radar transponder that responds to 9 GHz radar pulses, showing as a series of dots on a rescuer's radar display.
SWRStanding Wave Ratio. Similar to VSWR, measures the ratio of maximum to minimum voltage along a transmission line caused by impedance mismatch.
T
TransponderA radio device that automatically receives and replies to incoming signals. Aviation transponders respond to ATC radar interrogations.
V
VORVHF Omnidirectional Range. A type of radio navigation beacon that enables aircraft to determine their bearing from the station.
VSWRVoltage Standing Wave Ratio. A measure of impedance mismatch between a transmission line and its load. A perfect match is 1:1.
W
WavelengthThe physical length of one complete cycle of a radio wave. Wavelength equals the speed of light divided by frequency.
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