Stage 'A' commenced in April 1974. It involved the construction of a prototype radar receiver at Mount Everard, (near Alice Springs), a transmitter (at Harts Range, 160 km away) and a beacon in Derby. When completed (in October 1976) the Stage A radar ran for two years, closing in December 1978. Stage A formally ended in February 1979, having achieved its mission of proving the feasibility of OTHR. The success of stage A resulted in the construction of a larger stage 'B' radar, drawing on the knowledge gained from stage A.