Tuning Advice for an End-Fed Half-Wave (EFHW) Antenna
Tuning Advice for an End-Fed Half-Wave (EFHW) Antenna
End-Fed Half-Wave (EFHW) antennas remain popular because they cover multiple bands using a single radiator. However, they come with compromises, especially below 20 m. At RF.Guru, we focus on EFHW designs that prioritize efficiency — not just low SWR. That’s why you won’t find us selling (<20 m EFHWs are lossy and mostly inefficient) or relying on “magic capacitors” to mask transformer problems.
Understanding the EFHW Design
- Feedpoint & Transformer: A 49:1–70:1 transformer is required to bring the several-kΩ feedpoint impedance down to 50 Ω. Build quality and ferrite choice dictate efficiency.
- Radiator Length: Typical configurations:
- What we don’t sell: Non-efficient EFHWs such as 40-10 m or 80-10 m versions. Their radiation patterns and transformer losses make them poor choices compared with alternatives like the EFOC29.
Tuning Process
- Initial Setup: Aim for at least 10 m height on 40–20 m wires and 15 m on 160–80 m versions. Keep clear of metalwork and trees where possible.
- Measure SWR: Sweep all bands with an analyzer. Note resonance dips.
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Adjust Length:
- If dips are below band → shorten radiator.
- If dips are above band → lengthen radiator.
- Better: fold back excess wire instead of cutting until final trim.
- Add a Common-Mode Choke: Place at least one effective choke near the feedpoint or shack to stop feedline radiation and reduce noise pickup.
- Grounding: A DC path to ground at feedpoint or shack protects against static buildup and lightning surges.
Band Behavior
- Low Bands (160/80/40 m): Require full wire length; performance depends heavily on height.
- Mid Bands (20/15 m): Usually align well with harmonics, but wire length tweaks may shift resonance.
- High Bands (12/10 m): Expect multiple lobes and less predictable patterns — not the strength of EFHW designs.
Common Issues
| Issue | Cause | Solution |
|---|---|---|
| High SWR everywhere | Transformer issue | Verify turns, ferrite mix, and connections |
| Poor low-band efficiency | Antenna too low | Raise radiator; use better ground plane |
| Noise / RF in shack | Common-mode current | Install serious CMC choke |
Mini-FAQ
EFHW Antenna – Quick Answers
- Do you recommend EFHWs below 20 m? — No. Efficiency and pattern issues make them poor performers.
- Do your EFHWs use capacitors? — No. We design transformers correctly so no compensation caps are needed.
- What’s the biggest mistake in tuning? — Cutting the wire too short. Always fold back until final resonance is confirmed.
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