TACAN

TACAN is a contraction of Tactical Air Navigation, which is a navigation system employed by the military of the United States. It is a more accurate version of the VHF omnidirectional range / Distance Measuring Equipment (VOR/DME) system that provides range and bearing information for civil aviation.

TACAN in general can be described as the military version of the VOR/DME system. It operates in the frequency band 960–1215 MHz. The bearing unit of TACAN is more accurate than a standard VOR since it makes use of a two frequency principle, with 15 Hz and 135 Hz components. Theoretically a TACAN should provide a nine-fold increase in accuracy compared to a VOR but operational use has shown only a 1.5 to 2 fold increase. The distance measurement component of TACAN operates with the same specifications as do civil DMEs. Therefore to reduce the number of required stations TACAN stations are frequently co-located with VOR facilities. These co-located stations are known as VORTACs. This is a station composed of a DME range measurement unit (for civil and military use), a VOR (for civil bearing information) and the bearing part of a TACAN (for military bearing information).