Technical Glossary

Assembly Line Diagnostic Link, an OBD-I diagnostic connector used by General Motors vehicles for onboard diagnostics.

Amplitude Modulation, a technique where the amplitude of a carrier wave is varied in proportion to the information signal. Used in broadcasting since the early 1900s.

A method of demodulating AM signals that uses a local oscillator synchronized to the carrier frequency, improving signal quality over simple envelope detection.

Advanced Mobile Phone System, the first-generation analog cellular standard used in North America from 1983.

A device that matches the impedance between a transmitter and antenna, optimizing power transfer and reducing standing wave ratio.

Advanced Television Systems Committee, the digital television standard used in North America and parts of Asia for HDTV broadcasting.

Analog-to-Digital Converter, a device that converts continuous analog signals into discrete digital numbers for processing by computers.

Advanced Encryption Standard, a symmetric block cipher adopted by the U.S. government to protect classified information.

Automatic Frequency Control, a circuit that automatically maintains a receiver's frequency at the correct value despite drift or interference.

Automatic Gain Control, a system that automatically adjusts the gain of a receiver to maintain a constant output signal level.

Automatic Identification System, a marine tracking system using VHF radio to identify and locate ships for collision avoidance.

Amplitude Modulation with Signal Sideband, a variant of AM used in some broadcasting applications for improved efficiency.

A device that converts electrical signals into electromagnetic waves and vice versa, serving as the interface between a transmitter/receiver and free space.

Automatic Packet Reporting System, a real-time digital communications system for exchanging position and status information via amateur radio.

A long-wire directional antenna used for low-frequency reception, named after Harold Beverage. Typically requires a wire several wavelengths long.

The number of bit errors per unit time, expressed as a ratio. A key metric for measuring digital communication channel performance.

A short-range wireless technology standard for exchanging data over short distances using UHF radio waves in the 2.4 GHz band.

The difference between the highest and lowest frequencies in a continuous range. In digital contexts, it refers to the maximum data transfer rate.

The original frequency range of a signal before modulation. In networking, refers to transmitting digital signals directly on the medium.

Bit Error Rate, the ratio of incorrectly received bits to total transmitted bits. A fundamental measure of digital communication quality.

Bayonet Neill-Concelman, a miniature quick connect/disconnect RF connector used for coaxial cable in test equipment and networking.

Controller Area Network, a robust vehicle bus standard designed to allow microcontrollers and devices to communicate without a host computer.

Citizens Band Radio, a two-way radio service operating on 40 channels in the 27 MHz band. Popular for personal and trucking communications.

Code Division Multiple Access, a channel access method where multiple transmitters send information simultaneously over a single communication channel.

Cathode Ray Tube, a vacuum tube that displays images by firing electron beams at a phosphorescent screen. Was the standard display technology for decades.

A type of electrical cable with a central conductor surrounded by insulation, a metallic shield, and an outer jacket. Used for RF signal transmission.

Unwanted coupling of signals between adjacent communication channels, causing interference and signal degradation.

A high-frequency electromagnetic wave whose characteristics are varied to carry information in a modulation process.

Digital Smart Technologies for Amateur Radio, a digital voice and data protocol used in amateur radio communications.

Digital Video Broadcasting, a suite of internationally accepted open standards for digital television transmission.

A logarithmic unit used to express the ratio of two values of a physical quantity, commonly power or intensity. Abbreviated dB.

The process of extracting the original information-bearing signal from a modulated carrier wave.

A type of antenna consisting of two conductive elements, typically a half-wavelength long. The fundamental building block of many antenna designs.

An antenna that radiates or receives electromagnetic waves more strongly in one direction than others. Includes Yagi, log-periodic, and dish antennas.

Digital Mobile Radio, a digital radio standard for professional mobile radio applications offering voice, data, and IP connectivity.

Digital Selective Calling, part of the GMDSS system for maritime communications. Allows automated distress calls and routine communication.

A communication method where both parties can transmit and receive simultaneously. Full duplex allows simultaneous two-way communication.

Direct Sequence Spread Spectrum, a technique where the transmitted signal is spread over a wider bandwidth using a spreading code.

Dense Wavelength Division Multiplexing, a technology that multiplexes multiple optical signals onto a single fiber by using different wavelengths of laser light.

Decibel-milliwatts, a unit of power expressed in decibels relative to one milliwatt. Commonly used in radio and telecommunications.

Digital-to-Analog Converter, a device that converts digital numbers into continuous analog signals for output to speakers or other analog devices.

Digital Signal Processing, the use of digital computation to analyze, modify, and synthesize signals such as audio and radio.

The fraction of time a system is active or producing output. In radar, it is the ratio of pulse duration to pulse repetition period.

Effective Isotropic Radiated Power, the total power that would have to be radiated by a hypothetical isotropic antenna to produce the same signal strength.

Effective Radiated Power, the power radiated by an antenna relative to a half-wave dipole antenna. Used in broadcast regulations.

Emergency Position Indicating Radio Beacon, a safety device that transmits location signals via satellite for maritime and aviation emergencies.

A family of computer networking technologies commonly used in local area networks, metropolitan area networks, and wide area networks.

Electromagnetic Compatibility, the ability of electronic equipment to operate without causing or being affected by electromagnetic interference.

Electromagnetic Interference, unwanted electromagnetic energy that disrupts the operation of electronic circuits and communication systems.

The outline of the amplitude variations of a signal. In AM, the envelope carries the modulated information.

Electrostatic Discharge, a sudden flow of electricity between two electrically charged objects caused by contact or proximity.

Federal Communications Commission license classes (Technician, General, Amateur Extra) that authorize different levels of amateur radio operation.

Frequency-Hopping Spread Spectrum, a transmission technology where the carrier frequency rapidly switches among many frequency channels using a pseudorandom sequence.

Frequency Modulation, a modulation technique where the frequency of the carrier wave is varied in proportion to the information signal.

The amount of signal strength reserve added to a link budget to account for signal fading due to atmospheric conditions and multipath.

The number of cycles per second of a periodic signal, measured in Hertz (Hz). Determines the position in the electromagnetic spectrum.

The maximum difference between the instantaneous frequency and the carrier frequency in FM modulation. Determines the bandwidth of the FM signal.

A circuit or algorithm that passes certain frequencies while attenuating others. Types include low-pass, high-pass, band-pass, and notch.

A method of broadcasting stereo audio over FM radio using a pilot tone and multiplexed signal to encode left and right channels.

A radio receiver that automatically cycles through a range of frequencies, stopping when a signal is detected. Used for monitoring communications.

Global Positioning System, a satellite-based navigation system providing location and time information anywhere on Earth.

Global Maritime Distress and Safety System, an international system using satellite and terrestrial radio technologies for maritime distress communications.

The ability of an antenna or amplifier to increase signal power in a particular direction, measured in decibels (dB) relative to a reference antenna.

A radio wave that propagates along the surface of the Earth. Used primarily for AM broadcasting and maritime communications at low and medium frequencies.

Global System for Mobile Communications, a 2G digital cellular standard used by billions of people worldwide for voice and data.

A digital radio broadcasting technology that allows AM and FM stations to transmit digital signals alongside their analog signals.

High Frequency, the radio frequency band from 3 to 30 MHz. Used for long-distance communications via skywave propagation.

An antenna consisting of two conductors each a quarter-wavelength long, totaling a half-wavelength. The basic reference antenna for gain measurements.

Amateur radio, a hobby and service where licensed operators use various types of radio equipment to communicate for recreation and emergency services.

The process of transferring an active call or data session from one cell tower to another as a mobile device moves through the network.

A sinusoidal signal whose frequency is an integer multiple of the fundamental frequency. Harmonics can cause interference if not properly filtered.

High-frequency Emergency and Distress Radio, a maritime communication system for distress and safety at sea.

In-Band On-Channel, a digital radio broadcasting method that places digital signals in the same band as existing analog signals.

International Mobile Equipment Identity, a unique 15-digit number identifying mobile devices on cellular networks.

International Mobile Subscriber Identity, a unique number stored on a SIM card that identifies a mobile subscriber on the network.

Integrated Services Digital Broadcasting, a digital television and radio standard developed primarily in Japan.

The opposition of a circuit to alternating current, measured in ohms. Important for matching transmitter output to antenna input.

Disturbance caused by unwanted electromagnetic signals that degrade the quality of desired communications.

A region of Earth's upper atmosphere ionized by solar radiation, enabling HF radio wave reflection for long-distance communication.

A hypothetical antenna that radiates equally in all directions. Used as a reference for measuring antenna gain.

A wire loop installed in a room that generates a magnetic field for hearing aid compatibility, allowing direct audio pickup.

Long-Term Evolution, a 4G wireless broadband standard for mobile devices and data terminals, offering high-speed data for mobile phones.

Long Range, a spread spectrum modulation technique for low-power wide-area networks. Enables long-range communication with low power consumption.

A broadband directional antenna with characteristics that repeat periodically with the logarithm of frequency. Provides consistent gain over wide bandwidth.

Radio frequencies below 300 kHz, used for long-distance navigation and communication due to excellent groundwave propagation.

The time delay between the transmission and reception of data across a network. Lower latency improves real-time communication quality.

A comprehensive accounting of all gains and losses from transmitter to receiver, used to predict system performance and reliability.

Local Oscillator, an electronic oscillator within a receiver that generates a signal to mix with the incoming RF signal for frequency conversion.

Low-Frequency Array, a radio telescope system using many small antennas to observe the universe at low radio frequencies.

Multiple-Input Multiple-Output, a technology using multiple antennas at both transmitter and receiver to improve communication performance.

The process of varying one or more properties of a high-frequency carrier signal with a modulating signal containing information.

A measure of the extent of modulation applied to a carrier wave. In FM, it determines the bandwidth of the modulated signal.

Maximum Usable Frequency, the highest frequency that can be reflected back to Earth by the ionosphere for a given path and time.

A phenomenon where radio signals reach the receiving antenna via multiple paths due to reflection, diffraction, and scattering.

The radio frequency band from 300 kHz to 3 MHz, primarily used for AM broadcasting and long-range communication.

A VHF radio transmitter at an airport that provides a directional reference for aircraft during instrument approach procedures.

Medium Frequency, the radio frequency band from 300 kHz to 3 MHz. Used for AM broadcasting, maritime, and aeronautical communications.

The process of combining two signals of different frequencies to produce sum and difference frequencies. Used in frequency conversion in receivers.

New Radio, the 5G radio access technology standard developed by 3GPP for fifth-generation mobile networks.

Navigational Telex, an automated system for transmitting maritime safety information to ships via radio.

Non-Directional Beacon, a radio beacon used for aircraft navigation that transmits a continuous signal for direction finding.

Near Vertical Incidence Skywave, a propagation technique where radio waves are directed nearly vertically to reflect off the ionosphere for regional coverage.

Near Field Communication, a set of communication protocols enabling two electronic devices to establish communication within 4 cm of each other.

National Television System Committee, the analog television system used in North America and parts of South America.

Shortwave radio stations that broadcast encrypted messages to intelligence agents, typically reading strings of numbers in various languages.

A measure of the degradation of the signal-to-noise ratio caused by components in a radio communication system.

The measure of the signal created from the sum of all noise sources and unwanted signals within a measurement system. The minimum detectable signal level.

On-Board Diagnostics, a vehicle's self-diagnostic and reporting system that provides access to various vehicle subsystems.

Orthogonal Frequency-Division Multiple Access, a multi-user version of OFDM that assigns subsets of subcarriers to individual users.

An electronic circuit that produces a periodic, oscillating electronic signal. The foundation of all radio frequency generation.

Over-the-Air, referring to the wireless transmission of data, software updates, or broadcast signals without physical connections.

Phase Alternating Line, an analog television encoding system used in most of Europe and parts of Asia and South America.

Public Switched Telephone Network, the worldwide circuit-switched telephone system that has been the backbone of voice communication.

The position of a point in time on a waveform cycle. Important in modulation and signal analysis.

The orientation of the electric field of an electromagnetic wave. Antennas are designed for specific polarizations (vertical, horizontal, circular).

The behavior of radio waves as they travel through space, affected by reflection, refraction, diffraction, and absorption.

A bandpass filter at the front end of a receiver that attenuates out-of-band signals before they reach the mixer or amplifier stages.

A dimensionless parameter that describes how underdamped an oscillator or resonator is. Higher Q indicates narrower bandwidth.

Quality of Service, a set of technologies that manage network resources to provide prioritized treatment for specific types of data traffic.

A 90-degree phase relationship between two signals. Quadrature modulation techniques allow two independent signals to share the same frequency.

Remote Keyless Entry, a system that allows remote locking and unlocking of vehicle doors using a key fob transmitter.

The ability for a cellular subscriber to automatically make and receive calls outside their home network coverage area.

The reinforcement or prolongation of sound by reflection from a surface or by the synchronous vibration of a neighboring object.

A security feature in keyless entry systems that uses a different encryption code each time the transmitter is activated, preventing replay attacks.

An antenna designed to capture electromagnetic waves and convert them into electrical signals for a receiver.

A device that receives a signal and retransmits it at a higher power or on a different frequency, extending the range of communications.

Radio Frequency, alternating current in the range from about 20 kHz to 300 GHz. The frequency range used for wireless communication.

Radio Frequency Interference, electromagnetic radiation from an external source that affects the operation of an electronic circuit or system.

Séquence couleur à mémoire, an analog television encoding system developed in France and used in parts of Europe and Africa.

Software-Defined Radio, a radio communication system where components typically implemented in hardware are instead implemented in software.

Subscriber Identity Module, a smart card integrated circuit that securely stores the IMSI and keys for authenticating mobile subscribers.

Single Sideband, a refinement of amplitude modulation that transmits only one sideband, improving power efficiency and reducing bandwidth.

A low-power wide-area network technology designed for Internet of Things devices that require small, infrequent data transmissions.

Radio frequencies in the 3 to 30 MHz range used for long-distance international broadcasting and amateur radio.

A radio wave that is reflected or refracted back to Earth by the ionosphere, enabling long-distance HF communication.

The ratio of signal power to noise power, expressed in decibels. Higher SNR indicates a cleaner, more reliable signal.

A radio receiver that automatically tunes across a range of frequencies, stopping when it detects a signal. Used for monitoring various communications.

Standing Wave Ratio, a measure of how well a load is impedance-matched to a transmission line. Lower SWR indicates better matching.

Time Division Multiple Access, a channel access method that allows multiple users to share the same frequency channel by dividing the signal into different time slots.

Terrestrial Trunked Radio, a digital mobile radio standard designed for professional users such as emergency services and military.

A device that combines both a transmitter and receiver in a single unit, sharing common circuits like the antenna and power supply.

A device that automatically receives a signal and transmits a response. Used in radar, satellites, and air traffic control.

An electronic device that generates and amplifies radio frequency signals and feeds them to an antenna for electromagnetic radiation.

Ultra High Frequency, the radio frequency band from 300 MHz to 3 GHz. Used for television broadcasting, mobile phones, and two-way radio.

Very Low Frequency, radio frequencies from 3 to 30 kHz used for submarine communication and time signal broadcasts.

Vestigial Sideband, a modulation technique that transmits one sideband completely and a vestige of the other. Used in analog TV broadcasting.

Voyage Data Recorder, a maritime equivalent of a flight data recorder that stores navigation, audio, and radar data from ships.

Very High Frequency, the radio frequency band from 30 to 300 MHz. Used for FM broadcasting, television, and two-way radio communications.

A compact antenna technology that uses a matching circuit to enable a small physical antenna to operate across multiple frequency bands.

The distance between successive crests of an electromagnetic wave, inversely proportional to frequency. Measured in meters.

A family of wireless networking protocols based on the IEEE 802.11 standards, commonly used for local area networking and internet access.

A directional antenna consisting of a driven element, reflector, and one or more directors. Widely used for TV reception and amateur radio.

A low-power, low-data-rate wireless networking technology based on the IEEE 802.15.4 standard, used for home automation and IoT.