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Half-Wave Dipole

Wire Antennas Beginner HF 🔧 Buildable at home

The simplest resonant antenna: two straight conductors fed at the center.

Band
HF to UHF (scaled to band)
Gain
~2.15 dBi
Polarization
Linear (orientation of the elements)

Photos

Real-world photo of a Half-Wave Dipole in use
Real-world example. Source: Wikimedia Commons (CC BY-SA 4.0; 4shadoww).

Radiation / wave patterns

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

Radiation pattern of the Half-Wave Dipole
Antenna vertical. This is the side (elevation) view: a figure-eight with strongest radiation toward the horizon and deep nulls straight up and down. Seen from above it would be a circle (omnidirectional).

How & why it works

A half-wave dipole is a conductor cut to roughly half the wavelength of the signal, split in the middle where the feedline connects. At resonance the standing-wave current is maximum at the center and the voltage is maximum at the ends, giving a feedpoint impedance near 73 ohms that matches common coax reasonably well. It is the reference against which other antennas' gain is often measured (dBd).

Real-world uses

Amateur radio HF/VHF, FM broadcast receive, and as a building block for more complex arrays such as the Yagi-Uda.

Make one at home

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

See the finished antenna pictured above ↑.

A half-wave dipole is the classic first build — two wires and a feedpoint.

You’ll need

  • Insulated stranded wire (about 1.5 mm² / 14–16 AWG)
  • A centre insulator (or a plastic block) and two end insulators
  • 50-ohm coax + a connector; ideally a 1:1 current balun/choke
  • Rope to support the ends

Cut to length

Total length in metres ≈ 143 ÷ frequency (MHz); each leg is half that. For 7.1 MHz that’s ~20.1 m total, ~10.06 m per leg. Cut each leg a little long (a few %) so you can trim.

Build

  1. Attach a leg to each side of the centre insulator.
  2. Connect coax centre to one leg, braid to the other (via the balun/choke to keep RF off the feedline).
  3. Fix end insulators and hang it as high and flat as you can.

Tune

Measure SWR, find the lowest point, and trim both ends equally a few cm at a time to move it up in frequency (or add wire to go down).

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.