Offline Tool
Antenna Length Calculator
This calculator returns half-wave and quarter-wave wire lengths from frequency so you can cut a dipole or end-fed before you climb the tree. Trim long; an analyzer or SWR meter finishes the job.
Calculate dipole, quarter-wave, and ⅝-wave antenna dimensions from frequency. Velocity factor adjustable. Works offline. Works offline after your first visit.
This calculator returns half-wave and quarter-wave wire lengths from frequency so you can cut a dipole or end-fed before you climb the tree. Trim long; an analyzer or SWR meter finishes the job.
A 40 m half-wave dipole is about 66 feet of wire, 33 feet per leg, hung low (10–20 feet) for NVIS into Tennessee and southwest Virginia. An 80 m NVIS dipole is roughly twice that and is the night emcomm workhorse. Velocity factor and insulator end effects mean you will trim; start 2–3% long.
Related: SWR, NVIS advisor, antenna reference.
See also: Coax electrical length
468 divided by frequency in MHz gives approximate total length in feet for a half-wave dipole.
Typically 1/10 to 1/4 wavelength high — not a DX skywave antenna.
It is the textbook starting point in feet for a half-wave dipole. Trees, height, and wire type move resonance; measure SWR and trim.
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