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Electrical

Quarter Wave Antenna Length Calculator

Estimate quarter-wave element length using frequency and an editable shortening factor.

Ideal component relationshipsUnits and assumptions explained below
Circuit workbench
Circuit workbench

Keep RMS, peak and DC values distinct.

See the method

Enter circuit values

Runs on your device

Your circuit result

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter frequency, velocity/shortening factor.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Length = c × factor /(4f), using c = 299,792,458 m/s.

A WORKED EXAMPLE

Using frequency = 145 MHz, velocity/shortening factor = 0.95, the result is 0.491039371 m. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

Starting estimate only; element diameter, surroundings, feedpoint and construction change resonance.

What to keep in mind

Starting estimate only; element diameter, surroundings, feedpoint and construction change resonance. Ideal-component calculation for study and estimation. It does not select safe wiring, protective devices or component ratings for an installation.

Common questions

How do I use this quarter wave antenna length calculator?

Estimate quarter-wave element length using frequency and an editable shortening factor. Enter frequency in MHz, velocity/shortening factor. The starting example is editable; use values for the same system or project.

Which assumptions affect this result?

Starting estimate only; element diameter, surroundings, feedpoint and construction change resonance.

Methodology maintained by ClarityKit. How these tools are built and checked.