Abstract :
HF skywave radars rely on the ionosphere to propagate radio signals to distant regions of the Earth´s surface and back. The ionosphere exhibits variability over a wide range of spatial and temporal scales, and these variations impose characteristic transformations on the incident radar signals. The author confines his attention to the changes in polarisation during skywave propagation, examining the two-way propagation characteristics that relate to the radar observation process, as well as the one-way characteristics of interest to HF communications. The investigation reported is based mainly on measurements carried out using the JINDALEE radar system in Central Australia, together with orthogonally-polarised repeaters which were located at a range of some 1250 km. In addition, mathematical modelling of propagation and scattering processes has been carried out to validate and extend the experimental results
