End-Fed Half-Wave
Calculate EFHW wire length for ham radio operation and review harmonic-band coverage.
End Fed Half Wave
A half-wave wire fed at one end, commonly through a 49:1 transformer. Popular for portable operation and simple single-wire deployments.
EFHW Formula
These are the sizing relationships used by this calculator.
Wavelength
lambda (m) = 299.792458 / f(MHz) * VFWire Length
Wire length = lambda / 2Harmonic Bands
Harmonic frequency = Design frequency * nFAQ
What transformer ratio does this EFHW calculator assume?
It assumes the common 49 to 1 transformer arrangement used for many end-fed half-wave antennas.
Will one EFHW work on multiple bands?
Often yes on harmonic bands, but practical matching still depends on the transformer, installation, counterpoise behavior, and tuner choice.