Propagation
Propagation Prediction
Australian Space Weather Agency (IPS)
Propagation Theory (unfinished)
Radio frequencies form a fragment of the entire electromagnetic spectrum. It is generally considered that radio frequencies are found between 10kHz and 300GHz. 10kHz is considered to be the lower end of the electromagnetic spectrum Below that range, ultrasound is found, whereas above, infrared is found.
Electromagnetic energy travels as waves that move at the speed of light (300 000km/s), normally in a straight line. Atmospheric conditions can affect radio transmissions, and are responsible for transmissions between ham radio stations that are not a "straight line" distance apart.
Electromagnetic waves have two components, electric and magnetic. These are at right angles to each other. Unlike sound waves, electromagnetic waves do not need a medium through which to pass. Hence radio transmissions to and from deep space are possible.