Cutler Naval Station

The VLF Transmitter Cutler is the United States Navy's very low frequency (VLF) shore radio station at Cutler, Maine. The station provides one-way communication to submarines in the Navy's Atlantic Fleet, both on the surface and submerged. It transmits with call sign NAA, at a frequency of 24 kHz and input power of up to 1.8 megawatts, and is one of the most powerful radio transmitters in the world.

The current Cutler Naval Station was built in 1960 and became operational on January 4, 1961. It has a transmission power of 2 megawatts. As with all VLF stations, the transmitter has a very small bandwidth, and so cannot transmit audio (speech) but only coded text messages, at a relatively low data rate. The transmission consists of a continuously encrypted minimum-shift keying (MSK) signal capable of multi channel operations. The transmitter operates on 24.0 kHz. In the past it operated on 17.8 kHz. The callsign of the station is NAA.

The extensive antenna system consists of two separate identical umbrella antenna arrays, designated the “north array” and the “south array”.

Each array consists of a ring of 13 tall metal masts connected at the top by a network of horizontal cables. The cables form six diamond-shaped "panels" radiating from the central tower in a hexagonal pattern shaped like a snowflake. The two arrays normally operate together as one antenna, but each is designed to function independently to allow maintenance on the other array. The central tower of each antenna system is 304 m (997.5 ft) tall. It is surrounded by six 266.7 m (875 ft) tall masts, placed on a ring with a radius of 556 m around the central tower. The remaining six towers of the array are 243.5 m (799 ft) tall and placed on a circle of 935.7 m (3070 ft) around the central tower.

Each element (“panel”) of the antenna is suspended between the central tower, two towers of the inner ring and one tower of the outer ring. The entire array is 6140 ft (1.871 km or 1.16 miles) in diameter.

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