This tool calculates the physical dimensions of a 20 meter dipole antenna.
At 20 meters, the dipole length (L) is 31.2 feet. The length of each element of the dipole (l) is half of that at 15.6 feet.
The total length (L) of the dipole antenna is calculated as:
L = 468 / f
where f is the frequency in MHz.
f is calculated from the wavelength. For 20m the frequency is 15 MHz.
The length of each arm of the dipole
l = L/2