The reduction of signal strength as it travels through a cable or medium. Measured in dB. Higher frequency signals experience greater attenuation over the same cable length.

The range of frequencies over which an antenna or system operates within acceptable performance limits (typically defined by VSWR < 2:1).

Bayonet Neill–Concelman connector. A quick-connect RF connector commonly used on handheld radios, scanners, and test equipment. Rated to ~4 GHz.

A type of electrical cable with an inner conductor surrounded by a tubular insulating layer and a conductive shield. Used to carry RF signals with minimal interference.

Decibels relative to an isotropic radiator. Measures antenna gain compared to a theoretical antenna that radiates equally in all directions. Higher dBi = more focused beam.

Decibels relative to a half-wave dipole antenna. 0 dBd = 2.15 dBi. Used as an alternative gain reference in some antenna specifications.

A basic antenna consisting of two conductive elements. The standard reference antenna for gain measurements (0 dBd). Commonly used in base station and portable radio applications.

The coaxial cable connecting a radio transceiver to the antenna. Signal loss in the feedline directly reduces effective radiated power.

The number of oscillations per second of an electromagnetic wave, measured in Hertz (Hz). Common RF bands: VHF (136–174 MHz), UHF (400–520 MHz), 2.4 GHz (WiFi/Bluetooth).

A measure of how much an antenna focuses energy in a particular direction compared to a reference antenna. Gain does not add power — it redirects it.

A conductive surface (e.g., a vehicle roof) that acts as the reflective "other half" of a monopole antenna. Required for quarter-wave antennas to function correctly.

An antenna with a radiating element equal to half the wavelength of the target frequency. Does not require a ground plane, making it suitable for non-metal mounting surfaces.

The opposition to alternating current flow in a circuit, measured in Ohms (Ω). RF systems are standardized at 50Ω (data/voice) or 75Ω (video/TV). Mismatched impedance causes signal reflections.

A brand of low-loss coaxial cable (e.g., LMR-200, LMR-400) widely used in professional RF installations. Offers significantly lower attenuation than standard RG cables.

Power lost due to impedance mismatch between the antenna and feedline. Expressed in dB. Directly related to VSWR — a VSWR of 2:1 results in approximately 0.51 dB mismatch loss.

A single-element antenna that uses a ground plane as its second element. Common in mobile vehicle-mounted antennas.

A threaded RF connector rated for use up to 11 GHz. Commonly used in high-power and high-frequency base station antennas and professional repeater systems.

A common RF connector used on HF, VHF, and UHF mobile transceivers. Despite the "UHF" name, it is most effective below 300 MHz. Used by Icom, Kenwood, and Yaesu radios.

The orientation of the electromagnetic wave emitted by an antenna. Vertical polarization is standard for mobile and handheld radios. Mismatched polarization between transmitter and receiver causes signal loss.

The ratio of reflected signal power to incident power, expressed in dB. A higher return loss value indicates a better impedance match. >14 dB return loss corresponds to VSWR < 1.5:1.

A family of coaxial cable standards (RG58, RG174, RG6, etc.). "RG" stands for Radio Guide. Different RG types have different impedances, diameters, and loss characteristics.

SubMiniature version A connector. A small threaded RF connector rated to 18 GHz. Widely used on modern handheld radios (Baofeng, Anytone) and WiFi/cellular antennas. Note: SMA Male and SMA Female refer to the center pin, not the thread.

Standing Wave Ratio / Voltage Standing Wave Ratio. Measures the efficiency of power transfer from the feedline to the antenna. Ideal VSWR is 1:1. Values above 3:1 can damage radio equipment.

Threaded Neill–Concelman connector. A threaded version of the BNC connector, offering better performance at higher frequencies and in vibration-prone environments.

The radio frequency range from 30 MHz to 300 MHz. Common VHF band for mobile/ham radio: 136–174 MHz. VHF signals travel farther in open terrain but are blocked more easily by buildings.

See SWR. Voltage Standing Wave Ratio — the standard measure of antenna-to-feedline impedance match quality.

The physical length of one complete cycle of a radio wave. Calculated as: λ = c / f (speed of light ÷ frequency). Antenna element lengths are typically fractions of the wavelength (¼, ½, ⅝).