A glossary of technical and uncommon terms
A
ATU (Antenna Tuning Unit) – A device that matches the impedance between the transmitter and the antenna to minimize SWR.
B
Balun – A device that converts between a balanced line (e.g., dipole) and an unbalanced line (e.g., coaxial cable). The name comes from balanced to unbalanced.
Band plan – A conventional subdivision of frequencies allocated to amateur radio by emission type (CW, SSB, digital, etc.).
Beacon – An automatic radio station that transmits identification and test signals to monitor propagation conditions.
Blocking dynamic range – A parameter indicating a receiver’s resistance to strong signals on nearby frequencies without degrading reception of weak signals.
Booster – An additional power amplifier used to increase a transmitter’s output power.
C
CAT (Computer Aided Transceiver) – A control protocol that allows a computer to manage a transceiver’s functions (frequency, mode, etc.).
Choke – An inductor used to block common mode currents on a coaxial cable, often made by winding the cable around a toroid.
Collinear – A vertical antenna composed of multiple in-phase sections that compress the radiation lobe, increasing gain.
CW (Continuous Wave) – A transmission mode used for telegraphy (Morse code).
D
dBd – Decibels relative to a dipole. A unit of antenna gain referenced to an ideal dipole (0 dBd = 2.15 dBi).
dBi – Decibels relative to an isotropic radiator. A unit of antenna gain referenced to a theoretical isotropic antenna.
DDS (Direct Digital Synthesis) – A technique for generating variable frequency signals with high precision.
Dielectric – The insulating material in coaxial cables between the center conductor and the shield.
Discone – A wideband antenna, typically used for reception, with low gain but extensive coverage.
DSP (Digital Signal Processing) – Technology that filters and processes signals through software.
E
EIRP (Effective Isotropic Radiated Power) – The effective power an antenna radiates relative to an isotropic radiator.
EME (Earth-Moon-Earth) – Communication that uses the Moon as a passive reflector (moonbounce).
EMI (Electromagnetic Interference) – Disturbance caused by electromagnetic radiation.
E‑sporadic (Sporadic E) – An anomalous propagation phenomenon that reflects VHF signals from ionization clouds in the ionospheric E layer.
F
Feed – The radiating element positioned at the focus of a parabolic dish.
Field day – An event where amateur radio operators operate in the field, often using portable equipment.
FT8 – A weak-signal digital mode, highly efficient for long-distance contacts with low power.
G
Ground plane – A vertical antenna that uses a ground plane (radials) to create the image of the radiating element.
H
Homebrewing – The do-it-yourself construction of radio equipment.
Horn – A horn antenna, used in microwave bands for its linearity and signal cleanliness.
I
IARU (International Amateur Radio Union) – The international federation of national amateur radio societies.
IMD (Intermodulation Distortion) – A measure of transmitter linearity.
IQ – In-phase and Quadrature signals. A digital representation of a radio signal.
K
Keyer – A device that automatically generates dots and dashes in CW from paddles.
Kp – The planetary geomagnetic activity index, used to assess propagation stability.
L
Ladder line – A balanced transmission line with two parallel conductors separated by insulating spacers.
LNB (Low Noise Block) – A low-noise converter mounted at the focus of satellite dishes for reception.
M
MDS (Minimum Discernible Signal) – The lowest signal level detectable by a receiver.
Mesh – A parabolic reflector made of wire mesh to reduce wind loading.
Mixing dynamic range – A parameter evaluating the impact of phase noise on receiving weak signals adjacent to strong ones.
MUF (Maximum Usable Frequency) – The highest frequency that can be used for a given path via ionospheric propagation.
O
Offset – A type of parabolic dish with the focus shifted away from the center, so the feed does not obstruct the reflector.
OM (Old Man) – Slang term for an amateur radio operator.
P
Panadapter – A real-time graphical display of the radio spectrum.
Paddle – An electronic key for CW transmission.
PLL (Phase Locked Loop) – A circuit that locks an oscillator’s phase to a reference for stable frequency generation.
POTA (Parks On The Air) – An activity that awards contacts made from national parks.
Prime focus – A type of parabolic dish with the feed located at the center, in front of the reflector.
Q
QFH (Quadrifilar Helix) – A four-wire helical antenna used for satellite reception with circular polarization.
QRP – Low power, generally understood as less than 10 watts on HF.
QSO – A radio contact between two amateur stations.
R
Radiantismo – The activity carried out by amateur radio operators (Italian term for amateur radio practice).
ROS (Rapporto di Onde Stazionarie) – SWR. The ratio between forward and reflected power on a transmission line.
S
SDR (Software Defined Radio) – Radio defined by software, where most signal processing occurs digitally.
Shack – An amateur radio station and its set of equipment.
SFI (Solar Flux Index) – The solar flux index at 10.7 cm, an indicator of solar activity.
SOTA (Summits On The Air) – An activity that awards contacts made from mountain summits.
Speech processor – A circuit that enhances voice intelligibility during transmission.
SSB (Single Side Band) – A modulation mode used for voice transmission.
SWR (Standing Wave Ratio) – See ROS.
T
TCXO (Temperature Compensated Crystal Oscillator) – A crystal oscillator with temperature compensation for improved stability.
Trap – A resonant circuit that electrically isolates a section of an antenna.
Troposcatter – Propagation via tropospheric scatter, extending range beyond line-of-sight.
U
Unun – An impedance matching device for unbalanced lines (unbalanced to unbalanced).
V
VFO (Variable Frequency Oscillator) – An oscillator with variable frequency for tuning the receiver or transmitter.
VOX (Voice Operated Transmission) – A function that automatically activates transmission upon detecting voice.
W
WARC – The amateur bands of 30m, 17m, 12m, added after the World Administrative Radio Conference.
Waterfall – A graphical display showing the radio spectrum over time.
Y
Yagi – A directional antenna consisting of a driven element, a reflector, and one or more directors.