G5RV Antenna
Notes and considerations about the G5RV antenna, including design, variants, and installation.
Description
The G5RV antenna, with an overall length of 31.10m (102ft), functions as a 3/2-wave on 20 meters when installed horizontally at 12m (39ft), exhibiting a resonant frequency of 14.150MHz and an approximate resistance of 80 ohms. Its 10.36m (34ft) stub line, designed as a 1/2-wave on 14.150MHz with a 0.97 velocity coefficient, acts as an impedance transformer across other bands, aiming for multiband operation without traps.
On 20m and higher frequencies, the G5RV demonstrates improved gain compared to a standard dipole, attributed to the collinear effect from multiple 1/2-waves along the wire. The original design sought a multiband solution for limited spaces, often requiring an Antenna Tuning Unit (ATU) for effective operation across bands like 80, 40, 30, and 20m, particularly with modern solid-state PAs.
Variants, such as the F8CI modification, incorporate a 1/4 current balun at the stub line's base for symmetrical-to-asymmetrical transition, known as a remote balun. Proper flat-top or inverted-V installation is critical for maintaining symmetry and collinear gain, with inverted-V apex angles below 120° progressively diminishing higher-band performance.