Half Wave Dipole

The current distribution along a half-wave dipole is roughly sinusoidal. It falls to zero at the end and is at a maximum in the middle. Conversely the voltage is low at the middle and rises to a maximum at the ends. It is generally fed at the centre, at the point where the current is at a maximum and the voltage a minimum. This provides a low impedance feed point which is convenient to handle.

Half-Wave Dipole

To calculate the element length of a half-wave dipole the formula is Wavelength = Speed of Light / Frequency is used. However as electricity travels slower through copper than space, it must be reduced by the velocity factor Vf by about 0.951 before converting it into a 1/2 wavelength.

Here is a simple Java calculator.