For reference - JORN in Australia publicly admits to 1,000 - 3,000 km for their OTHR system. Range would tend to be longer during the night and around dawn, but HF propagation is hard to predict.
Australia's Jindalee Operational Radar Network (JORN) comprises three Over-The-Horizon Radar (OTHR) systems and forms part of a layered surveillance network providing coverage of Australia's northern approaches.
JORN provides wide area surveillance of Australia's northern approaches at ranges of 1000 to 3000 km from the radar sites, and is used to conduct air and maritime surveillance in support of Australia's national surveillance effort.
JORN