3
rd
Generation Dual Channel
Compact RDMS
TM
Telemetry Receiver-Combiner
62
Quasonix, Inc.
Figure 80: Advanced PCMFM Settings Window, Modulation Persistence Not Checked
When modulation scale index is set, the Modulation Scaling option on the Configure screen is simultaneously
changed to Hold. The Hold notation includes the new index number that the operator has chosen.
If the held index number is to be retained following a power-off cycle of the rack, then turn on Modulation
Persistence by checking the Modulation Persistence box on the Advanced PCMFM Settings screen. Save the current
setup profile using the Save Presets option. Refer to section 5.5.1.
When the RDMS™ is powered on, the default setting is Acquire, unless the unit was powered off from a preset
condition. If the unit was powered off from an unmodified preset setting, then the default condition of Modulation
Scaling is as defined in the preset. When Tracking is set, the modulation scale index is actively being tracked.
Note:
The active setting is not saved when the receiver is powered off, unless the Modulation Persistence option was
set to On.
If there are two channels, and the Combiner is set to On, the Modulation Scaling is NOT linked. Modulation Scaling
for channel one and channel two functions independently.
When the RDMS™ has a good lock on the target transmitter, Modulation Scaling should be set to Hold.
Mod Scaling should be turned off when a new generation, digitally synthesized transmitter is the source. Digitally
synthesized transmitters do not have a variable deviation sensitivity adjustment, and as such are not subject to
inaccurate modulation index settings
Acquire mode has two states: Armed and Triggered. When Modulation Scaling is set to Acquire, the state is set to
Armed. In Armed state, modulation scaling operates continuously.
If the receiver is locked and the delta h (the change in modulation index) has settled below the delta h threshold for
the specified settling time, the state changes to Triggered and the eye pattern turns green. In Triggered mode, the
estimated h (modulation index) is monitored but the scale is not updated.
If delta h goes above the delta h threshold and settles again, the receiver is still locked, and the Eb/N0 at the settling
point is higher than the last settling point, the current scaling is updated with the new estimate.
There is no transition from Triggered back to Armed except for setting the mode to Acquire again.
5.4.12.3 Mod Scale Index
The Mod Scale Index option allows the operator to manually set the modulation scale index. This enables the
receiver to operate at the optimum range of modulation desired by the user.
To change the Modulation Scale Index, ensure that the Modulation Index Scaling Mode is set to Hold. If it isn’t, the
Modulation Scale Index field is set to
read only
, as shown in Figure 81. Use the steps in section 5.4.12.1 to set and
save the scaling mode. When the scaling mode is saved as Hold, the Mod Scale Index field changes to an editable