Dipole Antenna Calculator

Your details

The operating frequency of your antenna. Most amateur HF bands fall between 1.8 and 29.7 MHz.
A horizontal half-wave dipole is the standard design. An inverted vee is hung from a single central support with drooped legs and runs about 2-3% shorter to maintain resonance.
The classic 468/f formula already bakes in an approximate k. Enable this to compute k from your exact wire diameter for a more precise physical length.
Total dipole length (m)Thin wire (standard)
10.046m

End-to-end physical length of the dipole

Total dipole length (ft)32.96ft
Each leg length (m)5.023m
Each leg length (ft)16.48ft
Free-space wavelength (m)21.112m
Half wavelength (m)10.556m
Quarter wavelength (m)5.278m
Adjustment factor (k)0.9516
Feed impedance (approx.)73ohm
Total length (m)10.046
Each leg (m)5.023
Half wavelength (m)10.556
Quarter wavelength (m)5.278

Your horizontal half-wave dipole is 32.96 ft (10.046 m) end to end.

  • Cut each leg to 16.48 ft (5.023 m). Make them 2-3% longer than calculated, then trim while monitoring SWR.
  • The feedpoint impedance is about 73 ohm. A 4:1 balun steps this down to 50 ohm coax; a 1:1 current balun is also recommended to suppress common-mode current.
  • A horizontal dipole shows a figure-eight radiation pattern broadside to the wire, with nulls off each end. Mount it as high as possible (at least a quarter-wavelength above ground) for best low-angle radiation.
  • The 20 m band is the workhorse of HF DX and contests, often open around the clock.

Next stepAfter building, check SWR with an antenna analyser. A 2:1 or better SWR across your intended bandwidth means the antenna is resonant and feeding efficiently.

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