Operational Essentials; Power Reference - Comtec CDM-840 Installation And Operation Manual

CDM-840 Remote Router
Appendix M
much attenuation. This can possibly limit the terminal from reaching budgeted margin and/or
terminal maximum power.
Power Reference calibration returns an error if the modulator output level is >0 dBm. If this
happens, you are notified to reevaluate budget values or cable attenuation before Power
Reference power is complete. Although modulator minimum power (-40 dBm) is still important,
it is not as critical to overall performance. The best balance for nominal operation is somewhere
in the middle of the range, leaving headroom on the top and bottom. This range balance is
extremely important when operating the network in dSCPC, as the system varies symbol rate
and power.
For more information on CDM-840 commissioning and cabling considerations, see
Comtech EF Data Quick Reference Document QR-CDM840.
M.2.2.2

Operational Essentials

Three basic criteria apply to power control function: Power Reference, Rated Maximum Power,
and Terminal Maximum Power. Each plays an important role in constraining and maintaining
power adjustments on the fly, with range check parameters, Tx Power Margin, and Maximum
Data Rate providing power constraints.
M.2.2.2.1

Power Reference

Reference Calibration uses the listed operational essentials to take a unique approach in
determining a power reference. This approach allows setting the reference at any point during
dSCPC operation. However, to avoid the risk of improper entrance link balance, the operator
MUST calibrate at the time of antenna commissioning.
Figure M-1. DPC Power Scale
M–4
MN-CDM840
Revision 3