Quarter-Wave Vertical

Calculate quarter-wave vertical radiator and radial lengths for ham radio frequencies.

Quarter-Wave Vertical

A simple vertical radiator with a radial field or ground system. Performance depends as much on the radials as it does on the radiator itself.

Band

Frequency (MHz)

Length Factor (%) Accounts for the typical shortening of a resonant element. Actual length varies with conductor and installation.

Number of Radials

Quarter-Wave Vertical Formula

These are the sizing relationships used by this calculator.

Wavelength

lambda (m) = 299.792458 / f(MHz)

Vertical Element

Vertical element = lambda / 4 * (Length factor (%) / 100)

Radials

Each radial = lambda / 4 * (Length factor (%) / 100)

FAQ

Does this quarter-wave vertical calculator size the radials too?

Yes. It calculates both the radiator and radial length using the selected frequency and length factor.

How many radials should I use on a quarter-wave vertical?

Four is a practical minimum, but additional radials usually improve efficiency and reduce ground losses.

Antenna Calculators

Use these as starting dimensions

Real antennas still depend on environment, conductor diameter, insulation, feed method, and nearby structures. Expect to trim and retune.

Good field workflow

Cut slightly long when possible.
Measure with the feed system you will actually use.
Make small tuning changes and record each one.

Length factor note

This is a starting estimate for the shortening of a resonant element. Conductor size, insulation, mounting height, nearby structures, and feed arrangement can shift the final length.