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Broadband HEX-beam calculator

How the broadband version differs from the classic

In the classic HEX-beam both the driven element and the reflector are bent into a W, which gives the reflector a high Q and leaves a useful bandwidth of about one percent. Steve Hunt, G3TXQ, opened the reflector out around the perimeter of the hexagon: the Q dropped, the bandwidth grew several times over, and the turning radius went up by only 15 %.

Rdriven elementreflector
The driven element stays W-shaped while the reflector runs round the perimeter — and that is what widens the band
Band
Frequency of peak F/B (MHz)
Element dimensions (half, centre to tip)
Driven element — half
Driven element — total wire length
Reflector — half
Reflector — total wire length
Gap between the element ends
Construction
Turning radius (spreader length)
Overall size, edge to edge
Reflector self-resonance
Driven element self-resonance
Characteristics
Gain
Front-to-back ratio
Input impedance
Reference model: Steve Hunt, G3TXQ, «A Broadband Hexbeam», antenneX no. 128, December 2007. Driven element 219″, reflector 207″, tip gap 24″, turning radius 130″ at the F/B peak of 14.184 MHz.

📐 How it is worked out​

HEX-beam dimensions scale linearly with wavelength, so the calculator scales G3TXQ’s reference 20 m model:

scale = 14.184 / f[MHz]

driven element (half) = 219″ × scale
reflector (half)      = 207″ × scale
gap between the ends  =  24″ × scale
turning radius        = 130″ × scale

What controls what (the conclusions of the original article):

  • the reflector sets where the antenna is tuned;
  • the driven element sets the feedpoint impedance;
  • the gap between the ends sets where the front-to-back peaks.

The driven element is longer than the reflector because the two have different shapes: what matters is not the lengths but the self-resonances. The driven element should resonate about 1.7 % above the reflector, and the F/B peak falls 0.7 % above the reflector’s resonance.

Where this calculator stops:
  • This is scaling of one proven model, not an independent calculation of the geometry
  • Element dimensions are given as in the original: half an element, from centre to tip
  • A multiband version also needs vertical spacing between the wires and a feed arrangement, and that is outside this calculator
  • Wire thickness barely affects the tuning (a quirk of this reflector shape), so there is no correction for it

🎯 In practice​

  • A directional antenna where a Yagi will not fit. The turning radius on 20 m is about 3.3 m.
  • Moving the design to another band. The same project for 15 or 10 m.
  • Checking a commercial kit. Compare the dimensions with what the maker offers.
Practical advice:
  1. To move the tuning, move the reflector. Touch the driven element only if the SWR is wrong.
  2. The scaled 24″ gap is a sensible compromise: a wider one gives pretty F/B figures in a narrow slot, at the cost of SWR.
  3. The spreaders must be the same length and evenly curved, or the geometry drifts.
  4. A ferrite choke on the feedline is not optional: the driven element is fed balanced.

© 2026 UR3PKI · CyberDev.Space · Content licensed under CC BY-NC-SA 4.0.

How to cite this calculator
UR3PKI. «Broadband HEX-beam calculator». CyberDev.Space. https://cyberdev.space/en/radio/calculators/antennas/hexbeam (licence CC BY-NC-SA 4.0).

The licence lets you use this material freely, including in teaching materials, but only with attribution to the author and a link to the source.

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