The radar equipment developed in secret by the Camp Evans Signal Laboratory was in use on the morning on 7 December 1941 in Hawaii.
The photograph shows the Antenna Array of the SCR 270B Radar Installation installed at Opana, Oahu, Hawaii. This is the same radar that was used to detect and track the Japanese attack against targets on the Island of Oahu on 7 December 1941. Unfortunately, the warnings were ignored. The photograph was taken late in December of 1941.