Comtech EF Data DMD-2050E - Manual (Page 85)

DMD2050E Universal Satellite Modem Theory of Operation
MN-DMD2050E Revision 2 3–43
Step Procedure
1c Make sure CnC function is OFF at both sites.
1d Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site A.
1e Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site B.
1f Measure/record Eb/No at Site B. Make sure there is sufficient margin to account for CnC.
1g Measure/record Receive Signal Level (RSL) at Site B.
2a Turn OFF the carrier at Site A.
2b Turn ON the carrier at Site B.
2c Make sure CnC function is OFF at both sites.
2d Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site A.
2e Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site B.
2f Measure/record Eb/No at Site A. Make sure there is sufficient margin to account for CnC.
2g Measure/record RSL at Site B.
3a Using Co+No/No readings calculate PSD ratio at Site A and Site B
3b If it is not within specification, make necessary adjustments to bring it within specification and
repeat measurements in Steps 1 and 2.
3c Also verify that the RSL is within spec.
4a Now, do not change the transmit power levels and turn ON both the carriers (on the same
frequency).
4b Turn CnC ON.
4c Measure/record Eb/No at Site A and B.
4d Measure/record RSL at Site A and B.
4e Now compare Eb/No in presence of two overlapping carriers with CnC with Eb/No when only 1
carrier was ON. Eb/No variation should be within spec for that modulation, FEC and PSD ratio.