CAA NZ AME Radio key terms

An authority issued under New Zealand radiocommunications rules permitting a person to operate specified radio transmitting equipment. For aircraft maintenance engineers, it covers the radio systems they test, certify, or maintain.

The New Zealand statute governing radio spectrum management, licensing, and enforcement. It establishes the framework under which aviation radio equipment is operated, inspected, and certified, including offences for unlicensed transmission.

The portion of the electromagnetic spectrum used for radio communication, conventionally from about 9 kHz to 3000 GHz. Aviation uses specific allocated bands, and engineers must ensure equipment operates only within its authorised allocation.

The designation of a frequency band for use by a particular radiocommunication service, such as aeronautical mobile or radionavigation. Allocations are set internationally and reflected in national planning, determining where aviation systems may transmit.

A defined range of frequencies sharing a designation, for example VHF 118–137 MHz for aeronautical voice. Engineers must know which band a system uses to select test equipment and confirm compliance.

The International Telecommunication Union, a United Nations agency that coordinates global radio spectrum use and publishes the Radio Regulations. Its allocations underpin national aviation frequency planning and equipment design standards.

Very high frequency, conventionally 30–300 MHz. Aeronautical voice communication uses 118–137 MHz, and VHF propagation is largely line-of-sight, which influences antenna placement and range expectations.

Ultra high frequency, conventionally 300 MHz–3 GHz. Aviation uses UHF for navigation aids such as DME and some military systems; short wavelengths support compact antennas and line-of-sight coverage.

High frequency, conventionally 3–30 MHz. Used for long-range aeronautical and maritime communication because signals can reflect from the ionosphere beyond line of sight. HF systems require different antenna and tuning considerations.

Radio wave travel in a nearly straight path that is blocked by terrain and Earth curvature. It dominates VHF and UHF aviation systems and explains why range depends on antenna height and aircraft altitude.

Reflection and refraction of radio waves by charged layers in the upper atmosphere, enabling beyond-horizon communication at HF. Engineers need this to understand HF performance variation with time of day and solar activity.

A radio wave that reaches a distant receiver after refraction by the ionosphere. Skywave is the basis of long-range HF communication and contrasts with ground wave and direct line-of-sight paths.

A radio wave that travels along or near the Earth's surface, following its curvature. It supports lower-frequency communication beyond the horizon and is distinct from skywave and line-of-sight propagation.

The process of varying a carrier wave's amplitude, frequency, or phase to carry information such as voice or data. Aviation systems use specific modulation types, and engineers must match test equipment and repairs accordingly.

A modulation scheme in which the carrier amplitude varies with the information signal while frequency stays constant. Legacy aviation voice and some navigation signals use AM, and its sidebands occupy bandwidth around the carrier.

A modulation scheme in which the carrier frequency shifts in proportion to the information signal while amplitude stays constant. FM resists amplitude noise and is used in some aviation and ground communication services.

A band of frequencies above or below the carrier produced by modulation, containing the information. Single-sideband transmission uses one sideband and suppresses the carrier, improving efficiency for voice communication.

A steady radio-frequency signal that is modulated to carry information. Its frequency defines the channel, and its stability and purity are key performance parameters engineers verify during testing.

The peak shift of a carrier's frequency from its centre value under frequency modulation. Excessive deviation causes interference to adjacent channels, so transmitters are adjusted and checked against specified limits.

The frequency separation between adjacent communication channels, such as 8.33 kHz or 25 kHz in aeronautical VHF. Correct spacing prevents interference and dictates receiver selectivity and transmitter stability requirements.

The degree to which an oscillator maintains its assigned frequency over time, temperature, and supply variation. Poor stability causes channel drift and interference, so it is a routine transmitter and receiver check.

A circuit that generates a periodic electrical signal at a set frequency, forming the frequency source for transmitters and receivers. Crystal and synthesised types are common in aviation equipment.

A circuit that derives many selectable output frequencies from one stable reference oscillator, often using phase-locked loop techniques. It allows radios to tune across channels while retaining accurate frequency control.

A feedback control circuit that locks an oscillator's phase and frequency to a reference signal. It is widely used in synthesisers and receivers for stable tuning, and faults can cause drift or unlock warnings.

A transducer that converts electrical signals into radiated electromagnetic waves, or the reverse. Type, location, bonding, and cable condition strongly affect range and clarity, making antenna inspection a routine maintenance task.

Arranging source, transmission line, and load impedances to be equal so maximum power transfers and reflections are minimised. Mismatch wastes transmitter power, reduces receiver sensitivity, and can damage output stages.

A measure of impedance mismatch on a transmission line, expressed as the ratio of maximum to minimum voltage or current. A high SWR indicates reflections and is checked when testing antenna and feeder installations.

A transmission line with a central conductor surrounded by insulation, a braided shield, and an outer jacket. It carries radio signals between equipment and antennas, and connector or shield faults cause loss and noise.

The weakest signal a receiver can detect and reproduce acceptably above noise. It determines usable range and is verified during testing; degraded sensitivity often traces to antenna, feeder, or front-end faults.

A receiver's ability to reject unwanted signals on adjacent frequencies while accepting the desired channel. It depends on filter design and matters increasingly with narrow channel spacing in congested bands.

The ratio of desired signal strength to background noise level at a point in a system, usually expressed in decibels. Higher ratios mean clearer reception, so engineers trace noise sources when performance degrades.

The level of background noise inherent in a system or environment below which signals become hard to distinguish. Electrical interference, poor bonding, and faulty components can raise it and mask weak signals.

Unwanted electromagnetic energy that disrupts equipment operation, caused by other transmitters, wiring faults, or poor shielding. Engineers investigate EMI through bonding checks, filtering, and equipment separation during troubleshooting.

Electrically connecting aircraft structure and equipment to provide a low-resistance return path and equalise potential. Good bonding reduces interference and static discharge risk, and is inspected and resistance-tested in service.

Conductive enclosure or braiding around wiring and equipment that confines or excludes electromagnetic energy. It protects radio and data systems from interference and is only effective when properly grounded and intact.

The release of accumulated electrostatic charge, which can cause radio noise or damage sensitive electronics. Bonding, static dischargers, and careful handling protect avionics from these effects.

A sudden transfer of static charge between bodies at different potentials, capable of destroying semiconductors. Engineers use grounded mats, wrist straps, and protective packaging when handling radio and avionics units.

The International Civil Aviation Organization, which sets international standards and recommended practices for aviation communication and navigation systems. Its provisions shape national requirements for equipment fitment and performance.