How Does HF Radio Work Over Long Distances?
Activity on the sun can have a wide-ranging effect on the earth. For example, radiation from the sun removes electrons from atoms in the upper regions of the earth’s atmosphere, forming the ionosphere. The existence of the ionosphere allows the use of High Frequency (HF) radio as a means of communication over long distances. An HF signal transmitted from the earth may travel some way through the ionosphere before being “bent” back down towards the ground. This occurs due to the interaction between the HF signal and electrically charged particles in the ionosphere. The signal can then “bounce” off the ground back into the ionosphere, return to the earth again, and so on. The distance a given HF signal will travel depends on the frequency, transmitter power, take-off angle relative to the ground and the state of the ionosphere through which it is traveling. For any given distance and time, there will be a certain range of HF frequencies that are most likely to provide successful communic
