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OPTION 006 Avionics
Annex-A-27
Spectrum analyzer
Preset and calibrate
Reference frequency
108.1 MHz
Reference level
10 dBm
Span/div 50
Hz
Resolution bandwidth
10 Hz
(3)
The typical traces on the oscilloscope and the spectrum analyzer are shown in Figs. A-22 and
A-23. These traces are for the 90 Hz and the 150 Hz tones' having equal amplitudes (i.e. 0%
DDM).
C0526
Ch. 1
= 200.0 mVolts/div
Timebase = 5.00 ms/div
Fig. A-22 Oscilloscope trace for a 0% DDM waveform.
(4)
On the UUT reduce the SDM depth using the rotary control. This will cause a reduction in
the amplitude of the oscilloscope trace and the sidebands on the spectrum analyzer trace.
Reset the SDM to 40%.
C0528
10.0
Atten 50dB 50
Ω
TG off
Ext std 2382
MARCONI
A dBm
Calibrated
0.0
-10.0
-20.0
-30.0
-40.0
-50.0
-60.0
-70.0
-80.0
-90.0
Ref 108.100000MHz
A
50.0Hz/div
Res bw
10 Hz
Inc 50Hz
2 s /div
Vid bw
22Hz
Fig. A-23 Spectrum analyzer trace for a 0% DDM waveform.