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End-Fed Half-Wave (EFHW)

Wire Antennas HF Portable 🔧 Buildable at home

A half-wave wire fed at its high-impedance end through a transformer.

Band
HF (multiband on harmonics)
Gain
~2 dBi
Polarization
Linear (depends on deployment)

Photos

Schematic drawing of the End-Fed Half-Wave (EFHW)
Schematic drawing of the End-Fed Half-Wave (EFHW) (original).

Radiation / wave patterns

New to these diagrams? How to read a radiation pattern →

Radiation pattern of the End-Fed Half-Wave (EFHW)
Like a dipole, the figure-eight lies in the plane of the wire: broadside is strongest, the ends are nulls.

How & why it works

Instead of feeding a half-wave wire at its low-impedance center, the EFHW feeds it at the end, where the impedance is very high (a few thousand ohms). A 49:1 (or 64:1) auto-transformer steps that down to about 50 ohms so coax can be used. Because a half-wave on the lowest band is also resonant on its harmonics, a single wire often works several bands, and end feeding makes it easy to deploy as a sloper or along a fence without a center support.

Real-world uses

Portable and POTA/SOTA operation, stealth home installations, and quick field setups.

Make one at home

A practical starting point — always trim and check SWR for your exact frequency.

See the finished antenna pictured above ↑.

An end-fed half-wave (EFHW) is a single wire fed at the end through a matching transformer — easy to deploy as a sloper.

You’ll need

  • A half-wave of wire: 143 ÷ f(MHz) metres for the lowest band
  • A 49:1 unun (a toroid transformer — buy one or wind it on an FT-240-43 core)
  • A short counterpoise wire (~0.05 λ) on the ground side

Build

  1. Connect the long wire to the high-impedance side of the 49:1 unun.
  2. Feed the unun with 50-ohm coax; add a common-mode choke a little way down the coax.
  3. Attach the short counterpoise to the ground terminal.

Tune

A half-wave on the lowest band is also resonant on its harmonics, so one wire often works several bands. Trim the wire end for lowest SWR.

Safety

  • Keep antennas well clear of power lines — never put one where it could fall onto or contact mains wiring.
  • Don’t transmit while anyone is close to the antenna; mind RF-exposure limits and your local licensing rules.
  • Ground masts and use coax surge protection where appropriate.
  • Cutting/soldering: eye protection and a ventilated space.