OPTION 006 Avionics
Annex-A-9
RF
Level
DDM
Fly
LT/RT
Presets
ON/OFF
Suppress
ON/OFF
Carrier
Freq.
DDM=
0.046
DDM=
0.093
DDM=
0.155
DDM=
0.200
DDM=
0.000
LOCAL
Carrier :
Freq.
RF Level:
SDM:
ILS Rate : 30.0 Hz
dBm
ILS Mode
MHz
Int Std: 10 MHz
108.100 0000
- 144.0
40.0%
ON
C1124
DDM :
LOC/GS
Freq.
90Hz Dominant FLY RT
ON COURSE
LOC 0
μ
A
Modulation ENABLED
0.00 %
Fig. A-6 DDM selection menu with presets
Five DDM preset values can be selected for either localizer or glideslope frequencies. The DDM
value can still be modified by the normal numeric entry, increment or rotary controls as well as the
preset mechanism. The DDM value is displayed in modulation index format when a preset value is
chosen. The equivalent glideslope DDM preset keys (0.000, 0.045, 0.092, 0.175, 0.400) are
displayed when a glideslope frequency is entered. The normal DDM selection menu is selected by
pressing the
[Presets ON/OFF]
key.
Localiser/glideslope frequency conversion
International agreements specify that localiser and glideslope frequencies are paired on any ILS
installation. The
[LOC/GS Freq.]
provides a convenient means of switching between the localiser
and glideslope frequencies. Provided the carrier frequency is set near to a recognised ILS
frequency, pressing
[LOC/GS Freq.]
will result in the carrier being changed to appropriate paired
frequencies.
Tone suppression
The 90 Hz or 150 Hz tone can be suppressed when either the SDM or DDM display box is
selected for data entry, using the
[Suppress ON/OFF]
key. This will result in the non-dominant
tone being suppressed without altering the SDM or DDM (% or index) as shown in Fig. A-7.
Selecting
[Suppress 90/150]
will change the tone to be suppressed. The modulation depth value
of the active tone is displayed under the SDM setting.
If the carrier frequency is not set precisely to the glideslope or localiser channel frequency and
[LOC/GS Freq.] is pressed twice, the frequency will be reset to the nominal localiser/glideslope
frequency.
The default SDM is 40% for localiser and 80% for glideslope, and pressing [LOC/GS Freq.]
will automatically reset the SDM to the default value.
When changing from localiser to glideslope the [Ident/Comms] key will disappear and then
reappear when changing back to localiser.