Pcm-Fm Trellis : Modulation Index Mitigation - Safran CORTEX RTR NeXt Series User Manual

6.8.3

PCM-FM Trellis : modulation index mitigation

6.8.3.1 Index tracking setting.
Using the legacy FM demodulator, the demodulator can withstand non accurate modulation index. But,
using the MS-FM demodulator, the modulation index is a critical point.

Nominal index.
Selecting this mode, the MS-FM demodulates using the 0.7pp index. The nominal can be used when
the transmitter uses a digital modulator. With an analog transmitter, it is not advised to use this mode.

Manual mode.
Selecting this mode, the user defines the demodulator index. This mode is only used when the
transmitter uses a digital modulator.

Automatic mode.
Selecting this mode, the receiver analyses the received signal and tracks the modulation index.
This mode is advised when using an analog transmitter.
Note:

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.
© Safran Data Systems – IMP000074 e14r1
Radio Telemetry Receiver
User's Manual
The index box is grey
and cannot be modified
Index used by the MS-FM
demodulator.
The index set by the user.
Initial index set by the
user.
Current index used by the
demodulator
This document is the property of
It cannot be duplicated or distributed without expressed written consent.
Ref. D104004
Is.Rev 07
Previous Ref.: DTU000567
Date: 21/06/2021
Safran Data Systems
.
Page 71