What is TACAN?

A Tactical Air Navigation System (TACAN) was/is used to provide geographical navigation for military applications. This technology pre-dates GPS and has now more or less been replaced by GPS in most if not all applications. It was used by most US Military aircrafts post 1950. Hoffman Electronics Corp. (now NavCom Defense Electronics) was a leader in developing the present TACAN system in the US starting in the late 1950s.

This is a polar-coordinate type radio air navigation system that provided military aircrafts with distance information, from distance measuring equipment (DME), and bearing (azimuth) information from a ground or ship-borne station. TACAN was the military version of the VOR/DME system. It was more accurate version of the VHF omnidirectional range/distance measuring equipment (VOR/DME) system that used to provide bearing and range information for civil aviation.

TACAN stations had a range of up to 390 nautical miles and operate in the frequency band from 960-1215 MHz. he bearing unit of TACAN was more accurate than the standard VOR system since it made use of a two-frequency principle, with 15 Hz and 135 Hz components, and because UHF transmissions are less prone to signal bending than VHF.

Military Aircrafts were equipped with TACAN avionics and used this system for en-route navigation as well as non-precision approaches to landing fields. The space shuttle was another such vehicle that was designed to use TACAN navigation but later upgraded with GPS as a replacement. 

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