NSS Annapolis, officially known as Naval Communications Station Washington, D.C. Transmitter or NavCommStaWashingtonDC, was a Very Low Frequency and High Frequencytransmitter stationoperated by the United States Navy. It was located at Greenbury Point, in Anne Arundel County, across the Severn River from Annapolis, Maryland at coordinates. NSS Annapolis was used by the USN for submarine communication. The station consisted of an supported by a 1,200-foot high central mast, which was insulated against ground, 6 guyed masts of 800-foot and three 600 foot freestanding towers. As of 2020, these three 600 ft towers are the only remaining. The huge towers were a local landmark, and served as a visual reporting point for aircraft landing at the nearby Baltimore-Washington International airport. A golf course runs through the former HF antenna farm; special rules addressed hitting a tower with a ball. The NSS HF receiver station, and the headquarters for NavCommStaWashingtonDC, 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. using a pair of Federal Electric 500 kilowatt . However, arc transmitters were significantly inferior to the then state-of-the-art Alexanderson alternator and one of the arc transmitters was replaced by a more modern TAW 300 kilowatt vacuum tube transmitter in 1931. VLF, or "longwave" radio was the standard at the time for long rangeradio transmission, only to be replaced by shortwave in the early 1930s. 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. 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 all of the antennas and most of the towers were demolished in 1999. Three of the smaller 600 foot towers were preserved near the tip of Greenbury Point to serve as aids to navigation for boaters on the Chesapeake Bay.
