Austria Theory AM key terms

An official authorisation granted by a national administration allowing a person to operate radio equipment on amateur bands, subject to stated conditions and the privileges of the assigned licence class.

A unique identifier assigned to a licensed amateur station, structured with a national prefix and suffix letters or digits, used to identify the operator during transmissions and in logbooks.

A range of frequencies allocated by international and national regulation exclusively or shared for amateur radio use, with each band defined by its lower and upper frequency limits.

The official assignment of radio spectrum to one or more radio services, specifying which services may use the frequencies and under what conditions.

A voluntary or recommended arrangement within an amateur band that designates sub-sections for particular modes or activities, helping operators avoid interference and coordinate use.

A written or electronic record of transmissions kept by an amateur, typically including date, time, frequency, mode and the callsign of each correspondent.

Any emission or radiation that seriously degrades, obstructs or repeatedly interrupts a radio communication service operating in accordance with regulations.

Operation of a station without a licensed operator present at the control point, permitted only under specific regulatory conditions such as automatic identification and remote control.

A message passed by an amateur on behalf of a person other than the operator, allowed only when regulations of both countries concerned permit it.

The relationship stating that current through a conductor equals voltage divided by resistance, expressed as I equals U divided by R, with units of amperes, volts and ohms.

The rate at which electrical energy is transferred, equal to voltage multiplied by current, and also calculable as current squared times resistance or voltage squared divided by resistance.

A passive component that opposes current flow with a defined resistance, dissipating energy as heat and often used to set bias or divide voltage.

A standard scheme of coloured bands printed on components such as resistors, where each colour represents a digit or multiplier used to read the component's value.

A component that stores electrical charge between two conducting plates separated by an insulator, opposing changes in voltage and passing alternating current more readily at higher frequencies.

A component, usually a coil, that stores energy in a magnetic field when current flows, opposing changes in current and presenting higher reactance as frequency rises.

The frequency-dependent opposition to alternating current offered by a capacitor or inductor, measured in ohms and causing current to lead or lag the voltage.

The total opposition to alternating current in a circuit, combining resistance with reactance as a complex quantity expressed in ohms.

The condition in a circuit containing inductance and capacitance where their reactances cancel, giving minimum or maximum impedance at a particular frequency.

A semiconductor device that conducts current mainly in one direction, used for rectification, protection and signal detection in radio circuits.

A three-terminal semiconductor device that can amplify or switch signals, forming the basic building block of most modern electronic circuits.

A circuit, usually using diodes, that converts alternating current into direct current by allowing current to flow in only one direction.

A circuit that increases the amplitude of a signal, typically described by its gain in decibels and its class of operation such as A, AB or C.

The ratio of output to input signal amplitude or power, often expressed in decibels, describing how much an amplifier or antenna system strengthens a signal.

A logarithmic unit used to express ratios of power or voltage, convenient for describing gain, loss and signal levels over a very wide range.

A simple antenna consisting of two straight conducting elements fed at the centre, with a length near half a wavelength at the operating frequency.

The physical distance between successive corresponding points of a radio wave, equal to the speed of light divided by the frequency.

A measure of how much an antenna concentrates radiated power in a particular direction compared with a reference radiator, usually expressed in decibels.

The ratio of maximum to minimum voltage or current along a transmission line, indicating how well the load impedance matches the line impedance.

The impedance a transmission line presents to a travelling wave, determined by its conductor geometry and dielectric, commonly 50 or 75 ohms in radio systems.

A transmission line with a central conductor surrounded by a tubular outer conductor, providing shielding and a stable characteristic impedance.

A matching network placed between transmitter and feed line that transforms the load impedance to present a low standing wave ratio to the transmitter.

The upper region of the atmosphere containing ionised layers that refract and reflect high-frequency radio waves, enabling long-distance communication.

The way radio waves travel from transmitter to receiver, including ground wave, ionospheric sky wave and tropospheric effects that vary with frequency and conditions.

The minimum distance from a transmitter at which a sky wave returns to earth for a given frequency and ionospheric condition, leaving a zone with no sky-wave reception.

An unwanted emission outside the necessary bandwidth of a transmission, such as harmonics, which must be suppressed to avoid interfering with other services.

A signal at an integer multiple of a fundamental frequency, produced by non-linear circuits and capable of causing interference far from the intended transmission.

A filter that passes signals below a cutoff frequency while attenuating higher frequencies, often used after a transmitter to suppress harmonics.

The ratio of desired signal power to noise power at a receiver, indicating how clearly a signal can be understood above background noise.

The minimum input signal level a receiver needs to produce usable output, determined by its noise figure, bandwidth and gain.

Techniques and devices used to reduce unwanted emissions or susceptibility, including filtering, shielding, grounding and careful antenna placement.