Coiled Into Compromise: The Truth About Shortened End-Fed Antennas
Last updated: August 22, 2025.
Coiled Into Compromise: The Truth About Shortened End-Fed Antennas
Shortened end-fed antennas with loading coils are everywhere — especially in portable and small-garden setups. They promise 80–10 m coverage with only 16–23 m of wire. But resonance isn’t efficiency. How far can you push coils before performance collapses?
Electrically Long, Physically Short
A full-size 40 m half-wave is ~20 m long. If you only have 16–23 m, you’re far short. Loading coils add inductance to force resonance at lower bands. But resonance ≠ efficiency.
The Compromise Behind the Coil
Loading coils shift current distribution. Radiation is driven by current — but a coil mid-wire creates a low-current point, starving the far end. Add coil losses (resistance, poor Q, heating) and efficiency collapses.
The “One Coil Wonder” Myth
Placing a single coil at ~60–70% of the wire can “force” a match. Reality:
- Efficiency collapses below ~0.15 λ physical length
- Impedance transition creates standing-wave distortion
- Much of the wire contributes little radiation
They may tune, but they’re more noise collectors than DX tools.
Why RF.Guru Doesn’t Coil EFHWs
We avoid loading coils in our EFHW designs. Here’s why:
- Efficiency: Coils add resistive loss — they’re heaters, not radiators.
- Bandwidth: Coil-loaded wires are narrow, requiring constant re-tuning.
- Impedance bumps: Coils add reactance, complicating matching.
- Durability: Coils fail outdoors (moisture, UV, corrosion).
- Pattern integrity: True EFHWs radiate cleanly; coil-shortened don’t.
- Simplicity: No mid-wire inductors → easier to install, predictable.
Better Alternatives
Instead of coils, we recommend:
- Skywave & Delta loops
- Short ground-mounted verticals
- Multi-element resonant verticals
- EFOC29 (80–10 m) — even extends to 160 m with a 40 m counterpoise
Case Study: Dual-Band EFHWs
Loading coils in 160/80 m or 80/40 m EFHWs distort the higher band:
- 80/160 EFHW: Coil ruins 80 m pattern, raising high-angle lobes and killing DX.
- 80/40 EFHW: Coil turns 40 m into NVIS-only, with distorted lobes.
Our solution: no coils, no compromise.
Conclusion
Loading coils can force resonance, but they can’t cheat physics. They narrow bandwidth, distort lobes, and waste power. That’s why RF.Guru designs antennas with full-length radiators and clean impedance — no coils, no compromises.
Mini-FAQ
- Do coils improve efficiency? — No. They add resistance and waste power as heat.
- Why do coil antennas seem to work? — They resonate and tune easily, but performance is weak compared to full-size designs.
- Are coils good for DX? — No. They often raise high-angle radiation, making them poor for DX.
- What’s better in small spaces? — Loops, short verticals, or compact OCFs perform far better than coil-shortened EFHWs.
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