Comtech EF Data CDM-625A Installation And Operation Manual page 624

CDM-625A Advanced Satellite Modem
Appendix F
F.3.2 Methods to Estimate PSD Ration
F.3.2.1 Use Downlink EIRP and Symbol Rate
Use Downlink EIRP and Symbol Rate to estimate the PSD Ratio from a link budget:
PSD Ratio Example:
Carrier
A to B
B to A
PSD Ratio (@ A) = -29.99 – (-31.74) = 1.75 dB
PSD Ratio (@ B) = -31.74 – (-29.99) = -1.75 dB
F.3.2.2 Use LST
PSD = Downlink EIRP – 10 * Log (Symbol Rate)
Downlink EIRP
27 dBW
24 dBW
Symbol Rate Power Spectral Density
500 ksps
375 ksps
F–18
MN-CDM625A
Revision 4
-29.99 dBW/Hz
-31.74 dBW/Hz