OPERATION
3-1-20
Communication channel testing
ILS systems allow the provision of an emergency voice channel on localizer frequencies.
This channel can be tested by selecting the
[Ident/Comms]
key to produce a display similar to the
one shown in Fig. 3-1-14.
Fig. 3-1-14 Ident/Comms selected
In this mode a fixed 0% DDM signal is provided and an additional modulation signal can
be added using the
[AM2 Depth]
key. The source of this additional modulation can be set using
the
[Select Source]
key. If internal modulation is selected the source frequency can be modified
using the
[Source Freq.]
key. Selecting
[DDM]
will return the instrument to normal ILS mode.
Communication channel testing is normally only required on localizer frequencies and
consequently changing from localizer to glideslope using the
[LOC/GS Freq.]
key will result in
the
[Ident/Comms]
key disappearing. Additional modulation can be obtained on a glideslope
frequency by directly entering the glideslope frequency instead using the numeric keys.
RF
Level
AM2
Depth
Source
Freq. F4
AM2
ON/OFF
Select
Source
Carrier
Freq.
Avionics
Modes
DDM
SDM
LOCAL
Carrier :
Freq.
RF Level :
SDM:
ILS Rate : 30.0 Hz
dBm
ILS ZERO DDM
MHz
Int Std: 10 MHz
108.100 0000
- 144.0
40.0%
ON
C1126
AM2 :
Int F4 : 1.0000 kHz
ON
0.0%
LOC/GS
Freq.
Modulation ENABLED
