HF-SSB radio systems are primarily used for long-range communications. HF (High Frequency) is that portion of the radio spectrum between 3 and 30 MHz. SSB (Single Side Band) is very energy efficient modulation technology for HF communication.

HF SSB radios for long ranges  use of the ionosphere – a layer of ionised gases that resides between 60 and 500 Kms above the earth’s surface, provides efficient, cost effective communications over short, medium and long distances – without the need for expensive re-transmission devices, such as the VHF or UHF repeaters and satellites, all of which have on going operational costs and a reliance on a physical infrastructure.

When HF/SSB radio waves are generated by the radio transceiver there are usually two components:

(i) The Ground or Surface Wave, which travels directly from the transmitting aerial to the receiving aerial following the contours of the land or surface of the sea.

(ii) The Sky Wave, which travels upward and at an angle from the aerial, until it reaches the ionosphere and is refracted back down to earth at a distance from the transmitting aerial dependant on the angle it is refracted by the ionosphere.