Reduction of ambiguities in HF radar results through a revised receiving antenna array and sounding pattern

The reconfiguration of both the receiver dipole array and the pulse set used by the National Oceanic and Atmospheric Administration (NOAA) HF radar enables all ambiguity in polarization to be removed. Further, it enables the aliasing of Doppler velocities to be reduced by a factor of 2, which allows more flexibility in the pulse repetition rate used and permits lower velocities to be detected above the noise. The revised four-dipole array is L-shaped, with a crossed dipole at the corner. The addition of two extra dipoles provides the facility for unambiguous “sky map” echo location.