Safran RX-1 User Manual page 111


The best way to set the MS-FM demodulator when an analog transmitter is used is :

When the received signal is rather strong, put the modulation index in automatic

Let the demodulator track the index. It may require seconds.

When the index is stabilized, read the index value

Set this index value in manual mode

Use manual mode
7.8.3.2 Modulation Index impact on the BER using MS-FM demodulator.
The graphic hereafter shows the impact of the modulation index using the MS-FM demodulator:

The Eb/ N0 has been set so that the BER = 10-5 with a 0.7 pp index.

Looking at the blue curve, the MS-FM demodulator is in nominal mode, the transmitted modulation index
has been changed and the Eb/N0 has been increased till the BER is 10-5.
Between 0.67 to 0.73 modulation index, MS-FM remains efficient.
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But outside this interval, there is a degradation on the BER
-

Looking at the red curve, the MS-FM demodulator is in auto mode, the transmitted modulation index has
been changed and the Eb/N0 has been increased till the BER is 10-5.
Between 0.6 to 0.8 modulation index, MS-FM remains efficient.
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14
12
10
8
6
4
2
0
0,6
© Safran Data Systems – IMP000074 e14r1
RX-1 Compact Operational Receiver
User's Manual
0,65 0,7
Modulation index
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It cannot be duplicated or distributed without expressed written consent.
Ref. D104047
Is.Rev 08
Previous Ref.: -
Date: 21/06/2021
Nominal mode
Auto mode
0,75 0,8
Safran Data Systems
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Page 111