In the early 1970s, AN/FPS-27 radar stations that had not been shut down received a modification (solid state receiver circuitry replacing vacuum tubes) that improved reliability and saved on maintenance costs.
Pada awal 1970-an, stasiun radar AN/FPS-27 yang belum ditutup menerima modifikasi (sirkuit solid state mengganti tabung vakum) yang meningkatkan keandalan dan menghemat biaya pemeliharaan.