Radio Words, Made Clear
Start with the everyday meaning. Connect it to the precise radio term. Then see where the analogy stops.
Antenna gain
How strongly an antenna sends or receives in a particular direction compared with a reference.
Technically speaking
A directional comparison that includes antenna efficiency. The reference matters: dBi uses an isotropic radiator and dBd a half-wave dipole.
Picture it
A flashlight reflector concentrates light in a direction; it does not create more light.
CHIRP
Free software for organizing and programming memories in supported radios.
Technically speaking
An open-source radio-programming application; support and transfer procedures depend on the exact radio model.
Picture it
Like a spreadsheet for radio memories, but each radio has its own supported fields. Back up each radio before editing.
Current
How much electric charge flows each second.
Technically speaking
Rate of charge flow, measured in amperes.
Picture it
Like water flow in the simple DC analogy. Current flows around a complete circuit.
Decibel
A convenient way to compare signal levels and add gains or losses.
Technically speaking
A decibel, abbreviated dB, expresses a logarithmic ratio. For power, dB = 10 log10(P2/P1).
Picture it
About +3 dB doubles power and −3 dB halves it. That does not mean twice the range or twice the perceived loudness.
Dummy load
A test load that takes the place of an antenna and absorbs transmitter power.
Technically speaking
A suitably rated load, commonly near 50 ohms, designed to dissipate RF power as heat with little radiation.
Picture it
Think of a test bench for the transmitter. Use a load rated for the frequency, power and duration; it can get hot.
HF skywave
A way for shortwave radio signals to reach beyond the horizon.
Technically speaking
HF signals can be refracted by the ionosphere back toward Earth. HF means high frequency: 3–30 MHz.
Picture it
A bending path is more accurate than a bounce off a hard ceiling. Frequency, ionization and launch angle matter.
Impedance
How an electrical circuit opposes alternating current at a particular frequency.
Technically speaking
Impedance combines resistance and reactance and is measured in ohms. Reactance introduces a phase relationship between voltage and current.
Picture it
A gearbox is a limited analogy for matching source and load. Matching does not eliminate cable loss or make an antenna efficient.
Offset
The difference between your receive and transmit frequencies.
Technically speaking
A repeater offset specifies the magnitude and direction of the frequency shift used for transmission relative to reception.
Picture it
Two one-way lanes: you listen on the repeater output and transmit on its input.
PL tone
A low audio tone that can tell a repeater to accept your transmission.
Technically speaking
PL is a trade name commonly used for CTCSS: continuous tone-coded squelch system. A receiver can require a matching tone before opening its squelch.
Picture it
Like an access gate, not a secret password. It does not encrypt your conversation. Transmit tone and receive tone squelch are different settings.
Propagation
How a radio signal travels from one place to another.
Technically speaking
The behavior of radio waves as they travel, including reflection, refraction, diffraction and absorption.
Picture it
Think of possible routes, not a fixed range printed on a box. Terrain and atmospheric conditions change which routes work.
Resistance
How strongly a component resists current flow.
Technically speaking
Resistance is measured in ohms. For an ohmic resistor, voltage equals current multiplied by resistance.
Picture it
A restriction in a pipe helps explain a resistor in a simple DC circuit. A radio is not just a fixed resistor.
Resonance
A frequency where the reactive effects of a circuit or antenna balance.
Technically speaking
At resonance, net reactance is zero at the stated measurement point. The remaining resistance is not necessarily 50 ohms.
Picture it
Pushing a swing at its natural rhythm helps explain frequency preference. It does not explain impedance matching or antenna efficiency.
SWR
A measure of how well a load matches its transmission line.
Technically speaking
Standing wave ratio is the ratio of maximum to minimum voltage along a line with incident and reflected waves. A perfect match gives 1:1.
Picture it
A good match does not prove good radiation. A dummy load can show a good SWR while turning power mostly into heat.
Voltage
The electrical push between two points.
Technically speaking
Electric potential difference, measured in volts.
Picture it
Water pressure is a useful introductory analogy for DC circuits, not a complete model of electricity.
Ham radio terminology: common questions
How do I look up an unfamiliar radio term?
Use the term index here, or activate an underlined glossary term in a guide. Read the plain definition first, then the technical meaning and example.
Are the analogies exact technical definitions?
No. Each entry separates the plain-language explanation from the technical definition and points out limitations of its analogy.