Naval Radio Transmitter Facility Aguada
Naval Radio Transmitter Facility Aguada is a tall guyed radio mast erected by the United States Navy. It is used as a facility of the US Navy for ashore and U.S. and NATO ships, planes, and submarines operating at sea in areas of broadcast coverage near Aguada, Puerto Rico at 18°23′55″N 67°10′38″W by using radio waves in the very low frequency range.
Source: Wikipedia — Naval Radio Transmitter Facility Aguada (CC BY-SA 4.0)