The EFHW Below 20 Meters: Popular, Easy, and Mostly Useless

The End-Fed Half-Wave (EFHW) antenna is widely promoted as a multiband miracle. But when you strip away the marketing, only one type of EFHW truly holds up on bands longer than 20 meters:

The dual-band half-wave/full-wave EFHW.

Forget about gimmicks, traps, or capacitors. If you're not using a real half-wave or full-wave radiator, you're just playing impedance games.

What Actually Works on Bands Longer Than 20 m

160/80 m EFHW (Full-wave on 80m, Half-wave on 160m)

• ~80.4 m radiator in inverted-L layout provides half-wave resonance on 160m and full-wave on 80m.
• Requires a 68:1 transformer for proper impedance transformation.
• Needs a 1:1 current choke at 0.05 λ on the coax.
• Also requires a high-impedance path to ground to stabilize the system due to common-mode coupling. See: Why EFHW antennas are inherently unstable.

80/40 m EFHW (Full-wave on 40m, Half-wave on 80m)

• ~40.2 m radiator in inverted-L form is half-wave on 80m and full-wave on 40m.
• Requires a 70:1 transformer for optimal matching.
• Needs a 1:1 choke at 0.05 λ and a high-impedance path to ground to mitigate instability. See: Why EFHW antennas are inherently unstable.

40/20 m EFHW (Full-wave on 20m, Half-wave on 40m)

• ~20.1 m radiator is the classic dual-band EFHW.
• Uses a 49:1 transformer and a 1:1 current choke at 0.05 λ.
• Predictable low-angle radiation on 40m and multi-lobe pattern on 20m.

20 m Monoband EFHW (Half-wave Only)

• ~10.1 m radiator acts as a clean half-wave on 20m.
• Uses a 49:1 transformer and a 1:1 choke at 0.05 λ.
• Simple, efficient, and free of matching gimmicks.

Why Other Multiband EFHWs Fail on Bands Lower Than 20m

Commercial “all-band EFHWs” often add parallel capacitors or rely on transformer reactance to simulate resonance on higher bands. These are not true resonances—they are impedance artifacts. The result is poor efficiency and wasted RF power.

Yes, you can make contacts with them—any wire in the air will radiate something. But the question isn’t “does it work?” It’s “how much of your RF actually gets radiated?”

If you’re tuning an EFHW with a capacitor trick to fake resonance, you’ve already lost efficiency. At that point, you’d be better off with a real resonant radiator like a 1/4-wave or 5/8-wave vertical that delivers controlled current maxima and stable radiation.

The Bottom Line

Stick with EFHWs in dual-band form between 160–20 m where true λ/2 and λ resonances exist:

• Use 160/80 with a 68:1 (inverted L) + 1:1 choke + high-Z bleed
• Use 80/40 with a 70:1 (inverted L) + 1:1 choke + high-Z bleed
• Use 40/20 or monoband 20 m with a 49:1 + 1:1 choke

For 20–10 m, skip the EFHW mythology. Use an EFOC or any properly designed antenna that radiates efficiently instead of wasting power in a transformer.

Pretty SWR doesn’t mean real resonance.
Feed a resonant wire — not a reactive trick.

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