chapter  11
2 DME overview
Pages 1

The DME navigation aid contains a transponder

(receiver and transmitter) contained within a

single navigation aid, Figure 11.2(b). The aircraft

equipment radiates energy pulses to the DME

navigation aid; secondary signals are then

transmitted back to the aircraft. An on-board

interrogator measures the time taken for the

signals to be transmitted and received at the

aircraft. Since we know the speed of radio wave

propagation, the interrogator can calculate the

distance to the DME navigation aid. DME

navigation aids can either be self-contained

ground stations, or co-located with a VOR

navigation aid, Figure 11.2(c).