📡 Ground-Plane / Vertical / J-Pole

Vertical Antenna Types

Quarter-wave ground-plane: The simplest vertical antenna. A single radiator 1/4 wavelength long, with 3-4 radials at the base. The radials act as the "other half" of the antenna. Four radials at 45° downward provide ~50Ω impedance. Four radials at 90° (horizontal) provide ~35Ω. More radials improve the pattern and reduce ground losses.

5/8-wave vertical: A 5/8 wavelength radiator provides about 3 dB gain over a 1/4-wave vertical. The radiation pattern is lower to the horizon, which is better for DX. Requires a matching network (usually an inductor) at the base to match the ~50Ω feedpoint.

J-Pole: A half-wave vertical fed with a quarter-wave matching stub. The matching stub transforms the high impedance of the half-wave element down to 50Ω. No radials needed. The J-pole is end-fed and can be made from copper pipe or ladder line. Very popular for 2m base stations.

Radial Recommendations

• 4 radials at 45°: Good match to 50Ω coax, easy to build
• 4 radials horizontal: Lower impedance (~35Ω), use a 1:1.4 transformer or adjust length
• 8+ radials: Improves efficiency, reduces ground losses, especially important on 160m/80m
• Ground-mounted: Radials should be buried 5-10cm underground
• Elevated: Radials can be 1/4-wave above ground, connected to antenna base