The End-Fed Half-Wave Myth: Why Most EFHWs Are Doing It Wrong
Updated August 21, 2025
At RF.Guru, we design EFHW antennas differently. You won’t find random multi-band gimmicks in our EFHW catalog — only carefully engineered dual‑band and monoband designs. We do offer multiband antennas in other categories like our EFOC line; these are still compromises, but they perform far better than generic “8010/4010” EFHWs. They’re not magic DX machines — just smart, practical solutions grounded in physics.
Why Only Half‑ and Full‑Wave Dual‑Band Configurations?
Because physics matters.
An EFHW performs efficiently only when each radiating segment is a half or a full wavelength on the operating band. Forcing a wire to act “multi‑resonant” across many unrelated bands (e.g., 80–10 m with one radiator) leads to:
- Unpredictable impedance curves
- Poor pattern control and lobe placement
- High magnetic strain and heating in the ferrite core → higher loss and lower reliability
- Increased current on unintended paths (feedline, surroundings)
Our EFHW Design Philosophy
We only build EFHWs in:
- Monoband Half‑Wave (e.g., 20 m)
- Monoband Half‑Squares (20/30/40 m)
-
Dual‑Band Full/Half‑Wave pairs such as:
- 160 m / 80 m
- 80 m / 40 m
- 40 m / 20 m
We match impedance with optimized transformer ratios. That’s why we offer 49:1, 68:1, and 70:1 variants — selected by band, feedpoint height, and geometry (inverted‑L, sloper, vertical, half‑square).
Why We Do Not Offer EFHW Designs for 17–10 m
On 17–10 m, a long EFHW behaves like a multi‑half‑wave system with distributed current peaks. Small length errors move those peaks; feedpoint Z swings; bandwidth narrows; and impedance becomes highly installation‑dependent. Consistent, efficient performance is difficult without “tuning tricks” that compromise current distribution and efficiency — so we don’t sell them.
Capacitors? No Thanks.
We deliberately avoid “compensation” capacitors in EFHW radiators or at transformers. They can force an SWR dip but distort the standing‑wave pattern, shift current nodes, create high‑voltage hotspots, and mask loss. A pretty SWR curve is not the same as efficient radiation.
Why Not Use a 49:1 on Everything?
Because one size doesn’t fit all.
A horizontal EFHW >10 m high often lands near the classic ~2.4–3 kΩ region suited to a 49:1. But with an inverted‑L or vertical EFHW, the feedpoint impedance frequently rises to ~4–6 kΩ+. A 49:1 then under‑transforms:
- Higher residual SWR
- More reactive mismatch (often capacitive)
- Lower pattern efficiency and higher transformer stress
EFHW Antennas in Our Catalog
All are engineered as low‑angle DX antennas and rated ~2–4 kW ICAS (model‑dependent).
| Configuration (Bands) | Transformer Ratio | Mounting Height | Suitable Layout |
|---|---|---|---|
| 40 m / 20 m Dual‑Band | 49:1 | > 10 m | Horizontal or Sloper |
| 20 m Monoband | 49:1 | > 10 m | Horizontal or Sloper |
| 80 m / 40 m Dual‑Band | 70:1 | 3–5 m feedpoint | Inverted‑L |
| 160 m / 80 m Dual‑Band | 68:1 | 1–3 m feedpoint | Inverted‑L |
Typical Radiation Behavior
| Configuration | Radiation Angle Type |
|---|---|
| 40 m / 20 m Dual‑Band | Low‑angle DX |
| 20 m Monoband | Low‑angle DX |
| 80 m / 40 m Dual‑Band | Low‑angle DX |
| 160 m / 80 m Dual‑Band | Low‑angle DX |
Deploy with Knowledge. Radiate with Purpose.
At RF.Guru, every EFHW is engineered — not guessed. No gimmicks, just performance.
Mini-FAQ
- Why do many “8010” EFHWs show low SWR? — The dip often comes from transformer reactance and loss, not correct current distribution.
- Can capacitors make EFHWs work better? — They can force an SWR dip but frequently degrade the current pattern and efficiency.
- What turns ratio should I use? — It depends on height and geometry. 49:1 for high, horizontal installs; higher ratios (68–70:1) often suit inverted‑L/vertical EFHWs.
- Why does my EFHW change when I move it? — Because current nodes and feedpoint impedance depend on height, surroundings, and layout.
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