# Radio Wave Propagation frequency and wavelength Radio waves, transmitted by an antenna, travel out at the speed of light in all directions.

If you could physically look at a particular radio wave and then count how many crests would go past in one second, you’d be referring to the frequency of the transmission.

Frequency is measured in Hertz.  In one second there could be thousands of waves (kGz – kilohertz) or millions (mHz – megahertz).

The speed of light is 300,000,000 metres per second!  Broken down that’s 186,000 miles per second.

If we were to look at the distance from one wave to another, that would be the wavelength.

Wavelength and frequency are related.  When waves are long, fewer will go past each second, when waves are short, more will pass.

That means a low frequency will have a long wavelength and a high frequency will have a short wavelength.

Because the speed of light is constant, measurement is easy.

The formula is Frequency x Wavelength (in metres) = 300 000 000 [constant]

So, for example, we tune to a VHF frequency of 118.0 mHz we would have a wavelength of 300 / 118.1 which is 2.54 metres.