EFHW Verticals on 10m, 12m, and 15m
Why Feeding a Half-Wave from the Bottom is a Bad Idea
End-Fed Half-Wave (EFHW) antennas are popular for multiband use, but many hams try to deploy them vertically for the higher bands — 10 m, 12 m, 15 m — thinking they’ve built a compact DX powerhouse.
Unfortunately, what they’ve often built is a power-hungry radiator with serious inefficiencies.
Feedpoint Position: Voltage Maximum, Current Minimum
The end of an EFHW is a high-voltage, low-current point. Radiation is driven by current — not voltage. When you install the feedpoint at ground level, you’re placing the current minimum at the base, exactly where you want the opposite.
- Maximum current occurs ~¼λ up the wire (~2.5–3.5 m on these bands).
- This means most of the radiation occurs above the feedpoint.
- At ground level, this leads to poor ground clearance, ground losses, and reduced efficiency.
By contrast, a monoband 1/4-wave vertical with raised radials has its current maximum exactly at the feedpoint — delivering clean, efficient power transfer into the ground system.
Transformer Losses: Real and Measurable
To transform the EFHW's ~2.5–3.5 kΩ feedpoint impedance to 50 Ω, a 49:1 or 64:1 transformer is required. These introduce unavoidable ferrite losses, especially at higher HF.
| Band | Transformer Loss | Power Lost |
|---|---|---|
| 15 m | ~1.4 dB | ≈28% |
| 12 m | ~1.6 dB | ≈32% |
| 10 m | ~2.0 dB+ | ≈37%+ |
On 10 m, more than a third of your RF is lost as heat before it ever radiates. This is why EFHW verticals feel deceptively convenient but struggle in performance against simpler designs.
How High is “Efficient”?
Mounting higher helps, but here’s what you need to reach reasonable efficiency:
| Feedpoint Height | Estimated EFHW Efficiency |
|---|---|
| Ground-mounted | <40% |
| 2 m above ground | ~55% |
| 4–5 m above ground | ~70–75% |
| ≥8 m above ground | 80–90% (comparable to 1/4λ vertical) |
To match the efficiency of a basic 1/4-wave vertical with four raised radials, your EFHW would need:
- Feedpoint at least 8 m above ground
- A high-voltage choke to suppress common-mode currents
- A carefully engineered, low-loss transformer
At that point, you’ve built something far more complex than a quarter-wave vertical — but still not necessarily better.
A Real-World Comparison: 15 m Band
| Parameter | EFHW Vertical (3 m feed) | 1/4λ Vertical + 4 Raised Radials |
|---|---|---|
| Height to Max Current | ~2.7 m | At base |
| Transformer Loss | ~1.4 dB (28%) | None |
| Total Efficiency | ~55–60% | >90% |
| Radiation Angle | ~20° | ~20° |
| Pattern | Omni | Omni |
Verdict: The quarter-wave monoband vertical beats the EFHW vertical in every key metric — simpler feed, less loss, more radiated power.
Conclusion
EFHW verticals for 10 m, 12 m, and 15 m are:
- Easy to deploy,
- Usable for low-power, multiband portable setups,
- But inefficient for DX unless mounted very high (≥8 m feedpoint), with excellent choking and low-loss transformer design.
If your goal is maximum DX efficiency, a simple 1/4-wave vertical with raised radials outperforms every time — with less cost, less heat, and more signal.
Mini-FAQ
- Are EFHW verticals good for DX? — Not really. Unless mounted ≥8 m high with optimized transformers, they waste too much power.
- Why do they lose efficiency? — Because current maximum is not at the base, and the transformer burns significant RF as heat.
- What’s better on 10–15 m? — A 1/4λ monoband vertical with raised radials: simpler, more efficient, and far better for DX.
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