PERCENT MODULATION ADJUSTMENT

TM 11-6625-2975-12

2-4. OPERATING PROCEDURES. (CONT)

1. Using DATA ENTRY keys, enter a marker beacon interference-type signal into test set.

2. Repeat step 1 using a different frequency interference -type signal (if required).

NOTE

In preset condition for each mode of operation, the percent modulation is automatically

set to the accepted standard. The percent modulation can be varied from standard in

both directions In 0.1-percent steps. Table 2-13 lists percent modulations for preset

conditions and variable range with respect to each mode of operation.

TABLE 2-13. PERCENT Modulation CHART

PERCENT MODULATION

MODE

VARIABLE RANGE

PRESET CONDITION

30.0

10.0 to 35.0

VOR

20.0

5.0 to 40.0

Localizer

10.0 to 80.0

40.0

Glide slope

95.0

90.0 to 97.0

Marker beacon

NOTE

In Iocalizer and glide slope modes of operation, DDM must be set to 0.000 before

percent modulation can be varied.

1020 Hz audio tone amplitude modulation is a fixed 30 percent in VOR and Iocalizer

modes. 1020 Hz tone Is not present in glide slope mode.

Enter selected rf carrier frequency from table 2-11 into test set (FREQUENCY/MODE

SELECTION, steps 1 through 6, page 2-16).

NOTE

In marker beacon mode, percent modulation is displayed in RDL/DDM/MOD display

upon selection of a marker beacon rf carrier frequency without pressing % MOD key.

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