## What is a harmonic?

A harmonic of a particular frequency (the fundamental frequency **F**) is a frequency that is an integer multiple of the first one. For example:

if f = 125 MHz, the harmonics would be:

1st harmonic = 1f = 125 MHz

2nd harmonic = 2f = 250 MHz

3rd harmonic = 3f = 375 MHz

4th harmonic = 4f = 500 MHz

….. etc.

In the diagram below it can be seen that harmonics share common nodes.

Mathematically, the basic wave equation is:

<math> \mathit{v}=\mathit{f}\times \lambda </math>

*v* is the velocity of the wave in meters per second – a constant close to the speed of light for radio waves in the atmosphere.

*f* is the frequency of the wave – how many cycles pass a fixed point per second

<math> \lambda </math> is the wavelength of the wave in meters – the distance between two peaks of the wave.

So, as the frequency increases, the wavelength decreases – a doubling of frequency causes a halving of wavelength, etc.

simple but easy to understand