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====== Glossary of amateur radio terms ======
//The RSGB manuals lack a consistent index or glossary, so this has been created to aid in study. The definitions have been taken from the texts, or where the definition does not exist in the manuals, from other reliable sources. If you see an error, notify @trainers on the Discord server and it will be checked & corrected as necessary. - There is also [[jargon|Jargon and Acronyms list]] //

**Amplitude** - The amplitude is the power of a signal: the greater the amplitude, the greater the energy carried in the signal.

**Amplification** - The process of making a signal stronger; for example, amplifying an audio signal makes it louder.

**Antenna** - The physical interface between electrical currents in a conductor and electromagnetic waves travelling in space. It is synonymous with //aerial//.

**Attenuation** - The process of reducing the power or amplitude of a signal. It is the opposite of amplification.

**Bandwidth** - The total range of frequency required for a modulated signal to be transmitted without loss of data.

**Capacitance** - the ability of a component to store an electric charge, or quantity of electricity. It is measured in farads, C.

**Carrier (Signal)** - A carrier, or carrier signal, is a steady waveform (in amplitude or frequency) that will have information added to it through modulation.

**Current** - The stream of electric charge through a conductor, related to the number of electrons passing a point in a second. It is measured in amps, A.

**Demodulation** - The process of retrieving the original data (e.g. voice) which was added to the carrier before transmission.

**Impedance** - The opposition to the flow of alternating current (AC) in a circuit by the combined effect of resistance and reactance. It is measured in ohms, Ω.

**Inductance** - The tendency of an electrical conductor, or component, to oppose a change in the electric current flowing through it. It is measured in henrys, L.

**Ionisation** - The process by which gases in the atmosphere are affected by ultra-violet radiation from the sun: molecules of gas have an electron knocked from their orbit, creating two parts: a free electron with a negative charge [-ve] and a gas ion which now has a positive [+ve] charge.

**Isotropic** - An object that has a physical property which has the same value when measured in different directions. Isotropic radiation will have the same intensity regardless of the direction of measurement.

**Modulation** - The process of converting data (e.g. voice) into radio waves by adding that information to a carrier signal.

**Oscillation** - A repetitive variation (usually in time) for a measure or value about a central value, e.g. a sine wave oscillates regularly between two peak values (positive/negative) about a central value of zero.

**Packet** - in the context of amateur radio, refers to [[packet|packet radio]]. There is a glossary of packet radio specific terms [[packet:glossary|here]].

**Polarisation** - The property of a wave (usually transverse) that defines the geometrical orientation of the oscillation of that wave, e.g. a sine wave could be said to have vertical polarisation.

**Propagation** - Any of the ways in which waves travel. Electromagnetic (radio, light etc.) waves can travel in a vacuum; sound waves by comparison cannot.

**Radiation** - Energy that travels away from a source. The energy has two fields associated with it (electrical, magnetic) and shows wavelike properties. Radio waves radiate at the speed of light (c, or approximately 300,000,000 metres per second), sound waves considerably more slowly (approximately 343 metres per second).

**Reactance** - The opposition to the flow of alternating current (AC) in a circuit by a component due to a combination of inductance and capacitance. It is measured in ohms, Ω.

**Resistance** - The opposition to the flow of current in a component. It is measured in ohms, Ω.

**Selectivity** - The ability of a receiver to reject signals outside the desired band width.

**Sensitivity** - The ability of a receiver to detect weak signals.

**Voltage** - A measure of the energy possessed by a quantity of electricity: a source of energy of one volt is able to deliver one joule of energy for each coulomb of charge that flows. It is measured in volts, V.