|Radio Waves And The Electromagnetic Spectrum (http://www.satcom.co.uk/article.asp?article=16)|
|Radio Waves And The Electromagnetic Spectrum|
Above is a diagram of a wave. Any such wave can be described by either its wavelength, or its frequency. Its wavelength is the distance between identical points on two adjacent waves. Its frequency describes the number of waves that occur each second - the units of frequency are Hertz (Hz).
In free space, radio waves travel at the speed of light which is approximately 3 * 108 metres per second. The relationship between the frequency and wavelength of a radio wave is given by the following formula:
Wavelength = (3 * 108 / Frequency)
Radio waves are electromagnetic - they contain both electric and magnetic fields. The electric and magnetic fields are at right angles to each other and also at right angles to the direction of propagation as shown in the diagram below.
The electromagnetic spectrum refers to the entire range of possible frequencies. Different parts of the spectrum have different names, as shown in the diagram below.
The part of the spectrum useable for radio communications ranges from below 10kHz (104Hz) to over 100GHz (1011Hz).
The radio spectrum is divided into bands. Waves of different frequencies behave differently. This along with the amount of spectrum available in the band governs the use of that band.
Satellite communications from space to ground, and vice versa, are focused in the 3 - 30GHz band. Above 30GHz is used for inter satellite links.
Copyright 2002 Satcom Online (http://www.satcom.co.uk)