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Ground Plane Antenna

Vertical Antennas

A quarter-wave vertical with radials that form an artificial ground.

Band: HF to UHF
Gain: ~1-3 dBi
Polarization: Vertical

Photos

Real-world photo of a Ground Plane Antenna in use — Real-world example. Source: Wikimedia Commons (Public domain; F1jmm).

Radiation / wave patterns

Idealized radiation pattern of the Ground Plane Antenna — Idealized azimuth radiation pattern (illustrative, generated). Radial scale in dB.

How & why it works

A ground-plane antenna makes the monopole practical up in the air by replacing earth with three or four quarter-wave 'radials' that fan out from the base. These radials supply the return currents and define the image plane, so the antenna no longer depends on the soil beneath it. Sloping the radials downward raises the feedpoint impedance from about 36 ohms toward 50 ohms for a direct coax match, while preserving the low-angle, omnidirectional pattern that verticals are valued for.

Real-world uses

VHF/UHF base stations, scanner and repeater antennas, and elevated HF verticals.