VHF NAVIGATION SYSTEM (Cont)
DISTANCE MEASURING EQUIPMENT (DME)
The DME-4000 is a remote mounted, three channel unit designed to provide position navigation information, including
distance. In the single DME configuration, channel 1 can be tuned by the pilot, channel 2 by the copilot. Channel 3 is used
by the FMS. In the optional dual DME configuration, each pilot has control over channel 1 of the onside DME,
while channels 2 and 3 of each DME are used by the onside FMS.
The DME measures line-of-sight distance between the aircraft and selected DME ground stations, calculating the rate of
closure and time to reach the selected station.
The DME information is displayed on the pilot’s PFD and the backup reversionary navigation display. The DME operates
in the frequency range of 962 to 1213 MHz. Most DME channel assignments are paired with VOR or ILS facilities and are
selected by inputting the associated VOR or ILS frequency to the DME. The frequency selection is done with the CDU or
the DCP in the frequency range of 108.00 to 117.95 MHz. DME frequencies not paired with VOR or ILS facilities
are arbitrarily associated with a group of frequencies (133 to 135 MHz in the VHF communications band.
STATION IDENTIFICATION
If a station identifier signal is received, the resulting audio signal is supplied to the audio control unit for selection to the
flight compartment speakers or the pilot’s and copilot’s headsets.
The distance indication is calculated by the DME transceiver and is sent for display to the pilot’s and copilot’s PFDs and
CDUs through the IAPS computer. The distance display is shown in a four-digit field followed by NM. When a no-com-
puted data condition occurs, the distance indication is replaced with dashes. The maximum DME tracking range is 300 NM.
Actual range under particular conditions will vary with altitude, terrain features and other factors.
DME HOLD FUNCTION
The DME hold function splits the paired tuning between DME and VHF navigation systems to enable independent opera-
tion. The DME hold function holds the DME transceiver to the current VHF navigation frequency and permits the VHF
navigation receiver to be independently tuned. When DME hold is on, which is indicated by the DME frequency suffixed
with an “H” below the NAV radio frequency on the radio menu or NAV CONTROL menu, turn the MENU knob to move
the selection box around the DME frequency. The DME hold function permits the VHF navigation receiver to be indepen-
dently tuned while the VHF navigation receiver is kept at the current frequency.
This function is selected when the DME H push button on the DCP is pressed. The paired VHF navigation
frequency display is activated. If the DME H push button is pressed again, the DME hold function is canceled. The paired
VHF navigation frequency display is also removed.
AUTOMATIC DIRECTION FINDER (ADF)
DESCRIPTION
The Automatic Direction Finder (ADF) System is a dual low-frequency radio system. The ADF system is used to indicate
the bearing to a selected ground station. The ADF system supplies station identification and voice signals to the
audio integrating system. The transmitting stations can be non directional beacons (NDBs) or standard broadcasting sta-
tions in the frequency range of 190 to 1799 kHz and maritime distress bands of 2088 to 2094 kHz. The bearing-to-station
data is shown on the pilot and copilots’ PFDs, and backup reversionary navigation display.
The unit receives unmodulated-voice / tone-modulated carrier or keyed carrier transmissions from Non-
Directional Beacons or AM stations, then calculates the station bearing, relative to the nose of the aircraft, as an output.
Using the beat frequency oscillator (BFO) function, the receiver produces a bearing to the station and also produces a 1020
Hz output tone when a carrier is present, in addition to the residual audio/noise from the detected carrier. A data-load option
may be included so that the BFO audio output will be “clean”, i.e., contain no noise, even under low signal
strength conditions.
Challenger Global 300 - Navigation
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