Firmware Update; Final Considerations - Comtec CDM-840 Installation And Operation Manual

CDM-840 Remote Router
Appendix M
comparing this value against the Up-converter's power limit value; if the calculated power is less
than or equal to this value, the requested rate is set. However, if the calculated power is greater
than this value, the requested rate will be limited to the set limit.
M.4

Firmware Update

The order of firmware update is important – Comtech EF Data recommends that you
first update the CDD-880, and then update the CDM-840.
Firmware update notes apply to systems running Firmware Versions 1.5.2.1 or lower that
require the DPC feature.
The DPC feature is designed not to affect any current operational settings during an update of
firmware. The parameter setting for power will remain the same until reference calibration in
the CDM-840 is applied, meaning that system will operate normally.
M.5

Final Considerations

DPC is not an accurate system or absolute solution. As fading varies with time, it is not possible
to keep up with changes as they occur quickly. This is particularly the case when scintillation is
occurring. Scintillation – when due to either low elevation troposphere effects or to the
ionosphere in tropical regions – sometimes involves changes of several dB per second. When
DPC is operated in combination with ACM, the system may reduce throughput during such quick
changes, but regains as the loop control catches up to resume normal operation.
M–25
MN-CDM840
Revision 3