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Antenna Calculator

Calculate wire lengths for common HF antennas. Pick a type and band — see dimensions, harmonic bands, and a diagram. Everything runs in your browser.

antenna

frequency

MHz

options

0.95

Accounts for wire thickness and insulation. Bare copper is typically 0.95. Insulated wire is lower (0.93–0.95). Thicker wire lowers the value slightly.

dimensions

total length —
each leg —
feed impedance —
SWR (50 ohm coax) —
description —

diagram

hf band coverage

Fundamental and harmonic bands for this antenna.

160m1.8–2.0
80m3.5–4.0
60m5.3–5.4
40m7.0–7.3
30m10.1–10.15
20m14.0–14.35
17m18.07–18.17
15m21.0–21.45
12m24.89–24.99
10m28.0–29.7

formulas

Standard wire antenna length formulas used by this calculator. The wire factor (velocity factor) accounts for the difference between the speed of light in free space and in a real conductor.

Half-wave dipole

Total length (ft) L = 468 × VF ÷ f
Total length (m) L = 142.65 × VF ÷ f
Each leg L ÷ 2

Where f = frequency in MHz, VF = wire velocity factor. The constant 468 is derived from the speed of light (983.6 ft/MHz) divided by 2, with a ~5% shortening factor for real-world end effects.

End-fed half-wave (EFHW)

Total length (ft) L = 468 × VF ÷ f
Total length (m) L = 142.65 × VF ÷ f

Same half-wavelength calculation as the dipole. The difference is the feed method — a 49:1 UNUN transformer at one end matches the high impedance (~2500 ohm) down to ~50 ohm for coax.

Quarter-wave vertical

Radiator height (ft) L = 234 × VF ÷ f
Radiator height (m) L = 71.32 × VF ÷ f
Each ground radial Same as radiator height

A quarter-wave vertical is half the length of a dipole. The constant 234 is simply 468 ÷ 2. Ground radials should be at least quarter-wavelength for effective performance.