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Cubical Quad

Directional Antennas HF Directional 🔧 Buildable at home

A beam built from full-wave loops instead of straight elements.

Band
HF/VHF
Gain
~7-10 dBi (2-3 elements)
Polarization
Horizontal or vertical (feed dependent)

Photos

Real-world photo of a Cubical Quad in use
Real-world example. Source: Wikimedia Commons (Public domain; N8ppq).

Radiation / wave patterns

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

Radiation pattern of the Cubical Quad
Aimed like a Yagi: a forward lobe in the boom direction, with a bit more gain per boom length.

How & why it works

A cubical quad is the loop equivalent of a Yagi: a driven full-wave loop is paired with a reflector loop (and optional director loops) on a boom. The parasitic loops re-radiate with phasing that reinforces the signal forward and cancels it backward, producing directional gain. Compared with a Yagi of similar size, the quad often shows slightly more gain per boom length and a lower radiation angle, at the cost of a bulkier, three-dimensional structure.

Real-world uses

HF DX beams, contesting, and VHF point-to-point links.

Make one at home

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

See the finished antenna pictured above ↑.

A 2-element cubical quad is a loop beam — more involved because of the spreaders, but a great performer.

You’ll need

  • A spreader frame (fibreglass or wood ‘X’ arms) for each loop
  • Wire for the loops; a boom to hold the two loops

Dimensions (per loop, by band)

  • Driven loop ≈ 306 ÷ f(MHz) metres of wire (one wavelength)
  • Reflector loop ~3% longer
  • Loop-to-loop spacing ~0.15–0.2 λ along the boom.

Build & tune

  1. String each wire loop around its spreader ‘X’ to form a diamond.
  2. Feed the driven loop at the bottom corner (horizontal) via a 1:1 choke; the reflector loop is a closed loop (or has a tuning stub).
  3. Trim the driven loop for lowest SWR; the slightly larger reflector sets the front-to-back.

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.