In 1957, the Naval Security Group (NSG) established the Communication Security (COMSEC) Mobile Support Unit 9 at Sasebo, Japan. In December of the same year, NSG established and commissioned the Naval Security Group Detachment (NSGD) Sasebo.
Initially the only mission for NSGD Sasebo was a high frequency direction finding (HFDF) operation with 11 personnel, including eight DF operators. The site operated as part of the NSG’s Western Pacific (WESTPAC) HFDF network controlled from U.S. Naval Communications Facility Kami Seya (A). Initially, it was considered a temporary site until the NSG Activity at Hakata assumed Sasebo’s HFDF mission.
The site was equipped with an AN/TRD-4 transportable DF station with a frequency range 540 kHz to 30 MHz. The antenna system consisted of two separate four element Adcock arrays, one of which had a range from 540 kHz to 10 MHZ and the other from 10 to 30 MHz. The DF receiver system included an R-390/URR HF radio communications receiver.