Distance measuring equipment (DME) is a transponder-based radio navigation technology that measures distance by timing the propagation delay of UHF radio signals. The DME system is composed of a UHF transmitter/receiver (interrogator) in the aircraft and a UHF receiver/transmitter (transponder) on the ground. The aircraft interrogates the ground transponder with a series of pulse-pairs (interrogations) and the ground station replies with an identical sequence of reply pulse-pairs with a precise time delay (typically 50 microseconds). The time difference between interrogation and reply minus the 50 microsecond ground transponder delay is measured by the interrogator's timing circuitry and translated into a distance measurement in nautical miles which is then displayed in the cockpit.
Specifications
- Transmitter Frequency: 1025 to 1150MHz
- Receiver Frequency: 962 to 1213MHz
- Number of Channels: 252(Spacing 1 MHz)(X and Y Channels)
- Tx Power Output: (0.4 to 2.0)KW
- Rx Sensitivity: -12dB/W min
- Maximum Range: 740KM or 399.9NM
- Accuracy: 0.2 KM(0.1 NM)(0 to 20 KM range), 0.4KM(0.2 NM)(above 20 KM)
- Channeling: Manual from control unit and automatic by airborne computer
- Audio Output: 100mW minimum to 200-ohm load
- Weight: 12 Kg
- Dimension: 396(L)x128(W)x196(H)mm