Ham radio glossary: 68 terms explained simply

RADIOMETEO · GLOSSARY

The words of radio, explained simply

Ham radio glossary: the terms you meet on RadioMeteo and on the air, with a short definition and a link to the tool that uses them.

68terms explained

6topics

IT · ENsame definitions

Q code and basic jargon

Abbreviations you hear in every contact.

QSO: A complete radio contact between two stations.
QSL: Confirmation of a contact: a card, or an electronic confirmation (LoTW, eQSL). open →
QTH: The location of the station. open →
QRM: Interference from other transmissions or electrical devices. open →
QRN: Natural noise, such as thunderstorms.
QRP: Low-power operating: usually 5 W or less.
QRZ?: Who is calling me? Used to ask for a callsign.
QSY: Change of frequency.
CQ: General call: anyone may answer.
73: Best regards, used at the end of a contact.
Callsign: The identifier assigned to the station, for example IZ6CLV.
RST report: Readability, strength and (in CW) tone of a signal, for example 59 or 599.

On the air

DX, contests and field activity.

DX: A long-distance contact or a contact with a rare country. open →
DX Cluster: Network that collects and shares spots of heard stations in real time. open →
Spot: Report of a heard station: callsign, frequency, time and comment. open →
Pile-up: Many stations calling the same DX station at once.
Split: Listening on one frequency and transmitting on another, typical of DXpeditions (e.g. “UP 5”).
DXpedition: An expedition to operate from a rare or seldom-active place. open →
Contest: A competition to make as many contacts as possible in a set time, under published rules. open →
Cabrillo: File format used to submit a contest log. open →
ADIF: Standard format for exchanging logs between programs. open →
POTA · SOTA · WWFF · IOTA: Activity programmes from parks, summits, protected areas and islands. open →
Repeater: Station that receives on one frequency and retransmits on another to extend coverage. open →
Shift and CTCSS tone: Offset between repeater input and output, and the sub-audible tone used to access it. open →

Propagation and space weather

The indices that tell you which bands are open.

Solar flux (SFI): Solar emission at 10.7 cm. High values favour the upper HF bands. open →
K and Kp index: Measure geomagnetic disturbance over 3 hours. Kp 5 or more is a storm (NOAA G scale). open →
A index: Daily average of geomagnetic activity. open →
MUF: Maximum usable frequency on a path. open →
LUF: Lowest usable frequency: below it absorption dominates. open →
FOT: Optimum working frequency, about 85% of the MUF. open →
foF2: Critical frequency of the F2 layer at vertical incidence. open →
D-RAP: NOAA map of HF absorption in the D layer after solar flares. open →
Solar flare: An explosion on the Sun that can cause HF radio blackouts. open →
Sporadic-E: Ionised clouds in the E layer that open 10 m, 6 m and sometimes 2 m, mostly in summer. open →
Grayline: The band between day and night, favourable to long-distance contacts. open →
NVIS: Near-vertical incidence propagation to cover short distances on HF.

Digital modes and computers

Software, interfaces and computer modes.

FT8 · FT4: Weak-signal digital modes with 15 s (FT8) and 7.5 s (FT4) cycles. open →
WSPR: Very low power digital beacons to study propagation. open →
RTTY: Radioteletype, used in DX and contests. open →
JS8: Weak-signal text messaging derived from FT8. open →
WSJT-X: Free software for FT8, FT4, WSPR and other modes. open →
CAT: Computer control of the radio (frequency, mode). open →
PTT: The command that puts the radio into transmit. open →
VOX: Automatic switch to transmit when audio arrives. open →
ALC: Automatic level control: keep it low in digital modes for a clean signal. open →
Waterfall: Display of signals over time and frequency. open →

Antennas and measurements

The quantities used to build and tune an antenna.

SWR: Standing wave ratio: how well the antenna is matched to the line. open →
Impedance: Opposition to RF current; the station standard is 50 Ω. open →
Dipole: A half-wave antenna fed at the centre. open →
End-fed (EFHW): A half-wave wire fed at one end through a transformer. open →
Balun · Unun: Transformers between balanced and unbalanced lines or between impedances. open →
Choke: Stops RF current flowing on the outside of the coax shield. open →
Velocity factor: How much slower a signal travels in a cable than in free space. open →
Gain (dBi · dBd): How much an antenna concentrates the signal compared with a reference antenna.
dBm: Power in decibels relative to 1 mW. open →
NanoVNA: Low-cost vector analyser for measuring SWR, impedance and resonance. open →
Antenna tuner: Matches the antenna impedance to the radio.
Radials: Wires that form the ground plane of a vertical antenna. open →

Listening, SDR and satellites

Receiving, decoding and tracking satellites.

SWL: Shortwave listener: someone who listens without transmitting. open →
SDR: Software-defined radio: most of the processing is done by the computer. open →
WebSDR: A remote receiver you can use from a browser. open →
NCDXF beacons: A network of 18 beacons transmitting in turn on five frequencies, from 14.100 to 28.200 MHz. open →
WEFAX: Weather charts sent by radio on shortwave. open →
Doppler: Change in received frequency as a satellite approaches or moves away. open →
ARISS: Programme for amateur radio contacts with the International Space Station. open →
Maidenhead locator: A 4 or 6 character code for a location, for example JN62WO. open →
Band plan: Division of the bands by mode and use, agreed within IARU. open →
UTC: Coordinated Universal Time: the reference time for logs, contests and spots.

Short definitions for general information. For regulations and band plans rely on official documents (your national authority, IARU Region 1). Checked on 21/10/2026.