Airborne System


Distance Measuring Equipment (DME)

Distance measuring equipment is a transponder based radio navigation technology that measures distance by timing the propagation delays 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 precise time delays (typically 50 microseconds). The time difference between interrogation and reply minus the 50ms ground transponder delay is measured by the interrogators timing circuitry and translated into a distance measurement in nautical miles which is then displayed in the cockpit.


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

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