The LORAN-C transmitter Rantum is a transmission facility for LORAN-C on the German island Sylt near the village Rantum at 54.8083°N 8.2936°W. It was established in the 1960s, initially using a guyed steel framework mast with a triangular cross section, approximately 190 metres tall. In 1996 this mast was replaced by a 193-metre-high mast of the same type but of a better mechanical design. The new mast is, as its forerunner, insulated from ground and has a triangular cross section. The construction, weighing 65t, is guyed in four levels at,, and . The transmitter was shut down on Dec 31, 2015.