Why a Half-Wave Vertical Doesn’t Need a Ground Field

— and When Radials Actually Matter

It’s often said that improving ground conductivity helps any antenna, and that a half-wave vertical “works without radials but performs better with them.” That sounds intuitive — but it’s only partly true. Whether ground improvement helps depends entirely on where the RF current flows, and that changes drastically between a quarter-wave and a half-wave radiator.

What Actually Matters: Where the RF Current Flows

Loss in the ground is proportional to the square of the current flowing through it:

Ploss = I² × Rground

• If large RF current returns through the soil, improving that resistance (with radials or a mesh) can recover several dB of radiated power.
• If almost no current flows in the soil, improving conductivity can’t make a measurable difference — there’s very little loss to begin with.

Quarter-Wave vs. Half-Wave Verticals

Quarter-wave (¼λ) base-fed verticals rely on the ground (or a radial field) as the missing half of the antenna. The current maximum is at the base, and poor ground conductivity introduces real loss. Adding radials dramatically reduces that loss and increases field strength.

Half-wave (½λ) vertical dipoles are self-contained. One half of the dipole provides the return path for the other, so no ground current is required. Ground radials under a half-wave dipole don’t increase efficiency — they only alter the pattern slightly if the lower end is close to earth.

Half-wave end-fed verticals (EFHW, J-pole, etc.) have very small base current because the feedpoint voltage is high and the impedance is several kilo-ohms. That means ground loss is inherently tiny, even on poor soil.

Example: at 100 W into a 5 kΩ load, current ≈ 0.14 A. Even with a 5 Ω ground path, loss ≈ 0.1 W — essentially nothing. That’s why adding an on-ground radial field doesn’t produce any “significant” improvement.

Why People Think Radials Help Their ½-Wave

• Improved SWR: a short “radial” or counterpoise defines the return path and stops the coax from radiating. The match stabilizes, but efficiency doesn’t change much.
• Less RFI: a good choke or counterpoise reduces common-mode current on the feedline. That’s not extra dB radiated — just cleaner operation.
• Pattern interaction: if the lower end of a ½-wave is very near the ground, the soil influences the near field slightly. A small mesh can smooth this, but it’s a fraction of a dB at most.

Ground Loss Is Still Relevant — Height Matters

Even though a half-wave vertical doesn’t depend on the ground for its RF return, it still interacts with it through the near field. At very low heights, that interaction introduces some loss and distorts the radiation pattern. Raising the antenna reduces capacitive coupling to the soil and improves radiation efficiency — especially for end-fed verticals, which can be deceptively lossy when installed just a meter or two above poor soil.

That’s why EFHW verticals perform best when mounted high — typically at least 0.05–0.1 λ above ground, and ideally several meters higher for low bands.

Why 17–10 m EFHWs Often Work Better Without a Transformer

At higher HF bands, the feedpoint impedance of a short vertical section can fluctuate widely, and ferrite transformers become less efficient. In these cases, it’s often smarter to skip the transformer entirely and use monoband EFHWs with feedline transformation instead — for example, matching through 75 Ω coax or open-wire feed.

This approach avoids ferrite losses, maintains cleaner phase symmetry, and provides higher radiation efficiency on 17–10 m, where the antenna’s current distribution is very sensitive to height and feed reactance.

Practical Takeaways

• ¼-wave verticals: radials are essential. The ground is part of the RF circuit — treat it like part of the antenna.
• ½-wave vertical dipoles: no radials needed. Just a 1:1 choke at the feed and some clearance above ground.
• ½-wave EFHWs: no ground field required, but do provide a defined return path (short counterpoise or choke). Mount them high to minimize near-field coupling loss.
• On higher bands: for 17–10 m, consider monoband EFHWs matched by feedline impedance rather than broadband ferrite transformers.

Bottom Line

Half-wave verticals are not ground-dependent antennas. Their efficiency is already high because the ground is not in the main RF path. Improving soil conductivity or adding on-ground radials rarely makes a measurable difference — what matters is height, feedline control, and avoiding transformer losses on higher bands.

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