Comtech EF Data CDM-760 - Manual (Page 392)

Appendix J Revision 2
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
J–14
J.4.7 Commissioning and Deploying Carrier-in-Carrier
Prior to commissioning a Carrier-in-Carrier link, it is critical that you fully test the link
in non-CnC mode and that you resolve all system issues – this includes external
interference, antenna pointing, cabling, and SSPA backoff. You should attempt to
turn on CnC only after you verify that the link is robust.
Comtech EF Data recommends that you do these steps to commission and deploy CnC:
Step Task
1 Turn ON the carrier at Site A. Carrier from Site B is OFF. CnC function is OFF at both sites.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site A.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site B.
 Measure/record Es/No at Site B. Make sure there is sufficient margin to account for CnC.
 Measure/record Receive Signal Level (RSL) at Site B, usually midrange.
2 Turn OFF the carrier at Site A. Turn ON the carrier at Site B. CnC function is OFF at both sites.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site A.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site B.
 Measure/record Es/No at Site A. Make sure there is sufficient margin to account for CnC.
 Measure/record RSL at Site B.
3 Using Co+No/No readings, calculate CnC ratio at Sites A and B. If it is not within specification, make
necessary adjustments to bring it within specification and repeat measurements in Steps 1 and 2.
 Also verify that the RSL is within spec.
4 Now, without changing the transmit power levels, turn ON both the carriers (on the same frequency) and
turn CnC ON.
 Measure/record Es/No at Sites A and B.
 Measure/record RSL at Sites A and B.
 Now, compare Es/No in the presence of two overlapping carriers with CnC with Es/No when
only one carrier was ON. Es/No variation should be within spec for that modulation and SR
ratio.
5 You may repeat the test for different SR ratios and modulation types.