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Distance Measuring Equipment (DME)
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According to NTIA:
DME and TACAN are very similar in their functional performance. DME systems operate between the bands 962-1213 MHz and are usually co-located with a very high frequency (VHF) Omni-directional Range (VOR) operating in the band 108-118 MHz to provide the distance and azimuth from the aircraft to the DME transmitter. An important requirement is a frequency separation of 63 MHz between the interrogation and the reply frequency. This accommodates the pulse-pair shaping and signal processing bandwidth necessary to achieve individual system integrity. This procedure leaves only 126 possible frequency pairs throughout the band 962-1213 MHz. DME and VOR operate in paired channels so at any given location, both the VOR and DME proposed assignments must “pass” their channel planning criteria. This puts additional constraints on DME assignments.
DME allows aircraft to fly safe, accurate paths during the en-route, terminal, landing, missed approach and departure phases of flight. The system provides aircraft pilots with the slant range to a ground-based transponder station. The ground-based transponder system is air-initiated, with the airborne transmitter interrogating a transponder, and calculating range from the time difference between the initiation of the interrogation and receipt of the reply. The maximum range for high altitude service (18km) is 240 km and for low altitude, service (5.5 km) the distance is 74 km. The maximum range for the standard terminal service is 46 km for an altitude of 3.7 km.
TACAN is a tactical air navigation system for the military services used ashore, afloat, and airborne. TACAN is primarily collocated with the civil VOR stations (VORTAC facilities) to enable military aircraft to operate in the NAS and to provide DME information to civil users. The Navy, Coast Guard, and Military Sealift Command (MSC) operate several hundred sea-based TACAN stations.
The FAA operates approximately 60 VOR, 405 VOR/DME, and 590 VORTAC ground stations, as well as another 30 DMEs. Other Federal agencies, state and local governments, and private entities also own some of these facilities.
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Frequency Bands |
| Band | Use | Service11 | Table |
| 960 - 1215 MHz | Distance Measuring Equipment (DME) | Aeronautical Radionavigation | F |
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