NSS Annapolis

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The 3 remaining towers of the NSS Annapolis.

NSS Annapolis, officially known as Naval Communications Station Washington, D.C. Transmitter or NavCommStaWashingtonDC(T), was a Very Low Frequency (VLF) and High Frequency (HF) transmitter station operated by the United States Navy.

It was located at Greenbury Point, in Anne Arundel County, across the Severn River from Annapolis, Maryland at coordinates 38°58′40″N 76°27′12″W / 38.97778°N 76.45333°W / 38.97778; -76.45333. NSS Annapolis was used by the USN for submarine communication. The station consisted of an umbrella antenna supported by a 1,200-foot (365.76 m) high central mast, which was insulated against ground, 6 guyed masts of 800-foot (243.84 m) and 3 freestanding towers of the same height.

The huge towers were a local landmark, and served as a visual reporting point for aircraft landing at the nearby Baltimore-Washington International (BWI) airport. A golf course ran through the VLF antenna farm; special rules addressed hitting a tower with a ball (usually stroke and distance). The NSS HF receiver station, and the headquarters for NavCommStaWashingtonDC(T), was located at the Naval Communications Station in Cheltenham, Maryland until 1969. In late 1969, the receiver station at Cheltenham closed and a new receiver station was activated at Sugar Grove, West Virginia.

NSS began transmitting in September, 1918 using 500 kilowatt Poulson Arc transmitters. However, arc transmitters were significantly inferior to the then state-of-the-art Alexanderson alternator and the arc transmitters were replaced by more modern vacuum tube transmitters in 1931. VLF, or "longwave" radio was the standard at the time for long range radio transmission, later to be generally replaced by shortwave.

VLF later became essential for communicating with submerged submarines, a critically important capability as submarines became strategic missile platforms. The NSS transmitter fed one million watts of radio energy to its antenna, and during idle times, transmitted the string "W W W VVV VVV VVV DE NSS NSS NSS" in Morse code. The power was so high and the frequency so low, one could hear the signal on practically any kind of receiver anywhere in the Annapolis area (not to mention within some people's dental work). Actual messages were also sent in Morse code, but were either prearranged code signals or were encrypted.

Rendered obsolete by satellite technology and the end of the cold war, NSS ceased operation and most of all of the antennas and most of the towers were demolished in 1999. Only three of the smaller towers were preserved for historic reasons.

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