Wailupe Naval Station
"Radio Wailupe wasn't an ordinary naval radio station--it was an OP-20-G intercept site--located east of Honolulu, and well away from both Pearl Harbor and Wahiawa.
"Wailupe's staff was all OP-20-G people, who weren't supposed to mix with ordinary navy radio folk, and they weren't supposed to talk about what they were doing. The radiomen were specially trained in Washington to receive Japanese morse code and enough rudiments of the Japanese radio equivalent of brevity code get some sense of what they might be picking up."[1]