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TM 11-6625-2975-12
1-13. TEST SET OPERATION. (CONT)
Any time information displayed in RDL/DDM/MOD and AUDIO STATUS displays is changed from preset
condition or rf carrier frequency is slewed (increased or decreased) from selected rf carrier fre-
quency, and it is desired to return test set to a preset condition, a single entry using STD key returns
test set to preset condition for selected rf carrier frequency. The rf output level is not affected by STD
key and remains at last selected output level.
LOCALIZER MODE OPERATION
When a standard Iocalizer rf carrier frequency is selected (see table 2-11), test set automatically
switches to LOC mode preset condition. The rf output signal from test set simulates a Iocalizer ground
station signal with the following parameters:
SIGNAL
OUTPUT PARAMETER
CHARACTERISTIC
Localizer rf carrier frequency
Selected standard Iocalizer ground station frequency.
Rf carrier modulation
90 Hz/150 Hz AM composite audio signal.
Amplitude (%) modulation
20.0 percent per tone, on beam center.
0.000.
DDM
U/L (150 Hz) or D/R (90 Hz)
U/L (150 Hz).
status indicators
A 1020 Hz audio tone can be added to Iocalizer rf output signal at 30-percent modulation by keyboard
entry. Individual control of identification signal allows operator to add or remove the signal to test the
receiver audio circuits.
The difference in depth of modulation (DDM) is selectable in standard preset DDM steps of 0.000,
0.046, 0.093 0.155, and 0.200, or in 0.001 increments to 0.400 through keyboard
entry. DDM can be slewed in either direction in 0.001 increments. DDM adjustments are used to
check receiver operation and accuracy. Amplitude (%) modulation in the LOC mode is variable from
5.0 to 40.0 percent in 0.1 percent increments to check receiver response. Amplitude (%)
modulation can only be varied at beam center.
When test set produces an up or left signal, the 150 Hz portion of the composite signal is predominant
and when test set produces a down or right signal, the 90 Hz portion of the composite signal is
predominant. All DDM signals produced by the test set are up or left signals unless changed to a down
or right signal through keyboard entry. The 90 and 150 Hz signals are balanced at 0.000 DDM and
neither signal is predominant, however, test set provides a U/L (150 Hz) indication which indicates
the next DDM step will be in the up or left direction. The DDM cannot be changed to indicate D/R (90
Hz) at 0.000 DDM.
Either or both of the 90 and 150 Hz audio signals can be removed as required to perform receiver flag
checks.
1-12

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