Ionospheric mapping for HF communications and HF direction finding

High frequency (HF, 3-30 MHz) radio communications are still extremely popular in Africa. However, HF is also widely used by illegal broadcasters and criminal elements including drug traffickers. This in turn has created a continued demand for HF direction finding (HF-DF). This paper presents the current status of the various means available for ionospheric mapping in Southern Africa and its applications in HF radio communications and direction finding. The operation, merits and limitations of the following methods of ionospheric mapping are addressed: the statistical international reference ionosphere (IRI) model; ionograms as derived from the three digisonde radar stations in South Africa; and computerised ionospheric tomography (CIT) based on total electron content (TEC) in the ionosphere, derived from the signals received by the network of dual frequency GPS receivers in Southern Africa