ISED Basic key terms

The number of complete cycles of a repeating wave that occur each second, measured in hertz. It determines where a signal sits in the radio spectrum and how it behaves in antennas and circuits.

The physical distance a radio wave travels during one complete cycle. It equals the speed of light divided by frequency, so higher frequencies have shorter wavelengths and smaller practical antenna elements.

The portion of the electromagnetic spectrum used for radiocommunication, conventionally from about 9 kHz to 3000 GHz. Access is divided into frequency bands and allocated among services by regulation.

A contiguous range of frequencies grouped under a single label, such as 88 to 108 MHz for FM broadcasting. Bands simplify allocation, equipment design, and the specification of operating limits.

The width of spectrum a signal occupies or a device can pass, expressed in hertz. Occupied bandwidth must stay within regulatory limits, and receiver bandwidth affects noise and selectivity.

The process of varying a carrier wave's amplitude, frequency, or phase to carry information. The chosen modulation affects occupied bandwidth, spectral efficiency, and immunity to interference.

A steady radio-frequency signal that is modulated to convey information. Its frequency, power, and stability are central parameters measured during transmitter testing and certification.

A logarithmic unit expressing the ratio of two power levels. Gains and losses add in decibels rather than multiply, making it the standard way to describe signal levels and interference margins.

An absolute power level referenced to one milliwatt, abbreviated dBm. It allows transmitter output, receiver sensitivity, and interference thresholds to be compared on a common logarithmic scale.

The regulatory assignment of frequency bands to one or more radiocommunication services, such as broadcasting or land mobile. It establishes which services may operate where before individual licences are issued.

The authorization for a specific station to use a particular frequency or channel under defined conditions, such as power and location. It follows allocation and is recorded in the station licence.

A frequency range where devices may operate without an individual radio licence, provided they meet prescribed technical rules. Compliance with power, bandwidth, and antenna limits is mandatory even without registration.

Formal confirmation by a recognized body that equipment meets applicable technical standards before it may be sold or used. It typically relies on documented test results and may lead to a compliance mark or certificate.

A published document specifying minimum performance, emission, and safety requirements for equipment. Standards define test methods so that results from different laboratories can be compared and accepted.

A formal statement, signed by the responsible party, that equipment complies with specified standards and regulations. It is supported by test evidence and identifies the standards applied and the party accountable.

Any unwanted energy that degrades, obstructs, or repeatedly interrupts a radiocommunication signal. It may come from other transmitters, unintended emissions, or electrical equipment, and must be prevented or resolved.

Interference that endangers radio navigation or safety services, or seriously degrades, obstructs, or interrupts a licensed radiocommunication service. Regulators treat it more seriously than mere annoyance and may require corrective action.

The ability of equipment to function satisfactorily in its electromagnetic environment without introducing intolerable disturbance to other equipment. It is achieved through limits on both emissions and immunity.

Unwanted radiation or conduction at frequencies outside the necessary bandwidth of a transmitter, such as harmonics and mixing products. Standards set strict limits because spurious emissions can interfere far from the intended channel.

A signal at an integer multiple of a fundamental frequency, produced by nonlinearity in transmitters and amplifiers. Harmonics are a common source of out-of-band interference and are controlled by filtering and emission limits.

The generation of unwanted signals at sums and differences of two or more frequencies when they pass through a nonlinear device. Products may fall inside a receiver's band and cause interference that filtering cannot easily remove.

The use of conductive enclosures, cable screens, or barriers to contain electromagnetic energy or exclude it from a circuit. Effective shielding reduces both emissions and susceptibility and requires proper bonding and grounding.

A conductive structure that converts guided radio-frequency energy into radiated electromagnetic waves, or the reverse. Its type, orientation, height, and surroundings determine coverage and radiation pattern.

The ratio of power radiated in a specified direction to that of a reference antenna, usually expressed in dBi or dBd. Gain is achieved by concentrating energy, not by creating power, and narrows the beam.

A graphical or numerical description of how an antenna radiates or receives energy as a function of direction. It shows main lobes, nulls, and unwanted back or side radiation.

The orientation of the electric field of a radiated wave, commonly vertical or horizontal. Mismatched polarization between transmitting and receiving antennas causes significant signal loss.

The difference in decibels between an antenna's maximum forward gain and its gain in the opposite direction. A high ratio reduces unwanted radiation behind a directional antenna and limits interference to other areas.

The degree to which an antenna concentrates radiation in one direction compared with an isotropic radiator. It is a pattern property independent of losses, whereas gain includes efficiency.

The power a transmitter would need to produce the observed field strength using a reference antenna, combining transmitter power, feedline loss, and antenna gain. It is the usual regulatory measure for coverage and interference potential.

The radio-frequency power delivered by a transmitter to its antenna feedline, measured at the output connector. It is distinct from effective radiated power because feedline and antenna effects are excluded.

A feedline with an inner conductor surrounded by insulation, a conductive shield, and an outer jacket. Its characteristic impedance and loss per metre affect how much transmitter power reaches the antenna.

The ratio of maximum to minimum voltage along a feedline, caused by impedance mismatch between transmitter, cable, and antenna. A high value indicates reflected power, reduced efficiency, and possible equipment stress.

The condition in which an antenna or circuit presents a purely resistive impedance at the operating frequency. Operating near resonance minimizes reflected power and maximizes energy transfer to the antenna.

An instrument that displays signal amplitude across a range of frequencies. It is used to measure occupied bandwidth, harmonics, and spurious emissions, with settings such as resolution bandwidth and span affecting the result.

The width of the frequency range containing a specified high percentage of a signal's total power, commonly 99 percent. It is measured to confirm a transmitter stays within its authorized channel or band limits.

An instrument, often with a directional coupler, that measures radio-frequency power delivered to a load. It is used to verify transmitter output and to check forward and reflected power in a feedline.

A documented record of measurements, equipment used, test conditions, and results against specified limits. It supports certification and conformity claims and must be traceable and reproducible.

The minimum input signal at which a receiver produces an acceptable output quality, usually stated in dBm. It depends on noise figure and bandwidth and sets the practical limit for usable communication range.

The ratio of wanted signal power to noise power at a given point, expressed in decibels. A higher ratio means clearer reception and determines whether a signal can be decoded reliably.

Connecting equipment and structures to earth through a low-impedance path for safety and for controlling unwanted currents. Proper grounding protects people, reduces noise, and supports lightning and surge protection.

Measures such as bonding, surge arresters, and air terminals that divert or limit lightning current before it reaches equipment or people. Antenna systems require particular attention because they are elevated and exposed.

An authorization issued to a person or organization to operate radiocommunication equipment under stated conditions, including frequencies, power, and location. Operating outside those conditions breaches regulatory obligations.

The reduction in signal power as a wave travels between transmitting and receiving antennas, increasing with distance and frequency. It is used in link budgets together with antenna gain and receiver sensitivity.

A designated frequency slot, or pair of slots, assigned for communication within a band. Channel spacing and width are set by regulation to keep adjacent users from interfering with one another.

A receiver's ability to reject strong signals on nearby frequencies while receiving the wanted channel. Good selectivity reduces interference from adjacent channels and from strong transmitters close by.

A circuit that passes frequencies below a cutoff while attenuating higher ones. Placed at a transmitter output, it suppresses harmonics and other high-frequency spurious emissions before they reach the antenna.

The permitted deviation of a transmitter's actual carrier frequency from its assigned value, usually stated in parts per million or hertz. Tight tolerance prevents overlap with adjacent channels and keeps emissions inside the band.

The amplitude at the top of a spectrum analyzer display, used to position signals on screen without clipping. Correct setting ensures measurements are neither compressed nor lost in the noise floor.