Free tool
Antenna Length Calculator
Work out the length of a dipole, vertical, 5/8 vertical or full-wave loop from the frequency you want to work.
Antenna length follows directly from wavelength, with a correction for the fact that a real antenna is not in free space. This calculator applies the standard formulae, shows the end effect correction, and gives you the practical length to cut plus the height that will make the antenna work well.
Inputs
0.95 is the usual starting value for a wire dipole. Lower it for thick wire.
Result
Total antenna length--m
Enter a frequency to calculate.
Length per leg-- m
Suggested height-- m
Feed point impedance-- ohm
Bandwidth estimate-- kHz
Bandwidth against band width--
Length = 143 / f (MHz) for a half-wave dipole, in metres, before the end effect correction.
Height = a half wavelength is ideal; a quarter wavelength is the practical minimum for distance work.
Cut the wire long and trim in small steps while watching an analyser.
Height = a half wavelength is ideal; a quarter wavelength is the practical minimum for distance work.
Cut the wire long and trim in small steps while watching an analyser.
What this calculator returns
Total lengthLength per legSuggested heightFeed point impedanceBandwidth estimate
These figures are calculated from standard formulae and typical published component data. They describe an ideal installation, not yours. Measure your own antenna before cutting wire, and confirm any figure against your equipment and local regulations before relying on it.