Comtech EF Data SLM-5650A - Manual (Page 313)

SLM5650A_CDM625 Satellite Modem Revision 8
DoubleTalk Carrier-in-Carrier Option MN-SLM5650A
15–15
15.4.6 Carrier-in-Carrier Commissioning and Deployment
Prior to commissioning a Carrier-in-Carrier link, it is critical that the link is fully tested in non
Carrier-in-Carrier mode and all system issues including external interference, antenna pointing,
cabling, SSPA backoff are resolved. Only after the link is robust, should the user attempt turning
on Carrier-in-Carrier.
The following procedure is recommended for Carrier-in-Carrier commissioning and deployment:
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 Eb/No at Site ‘B’. Make sure there is sufficient margin to
account for CnC.
 Measure/record Receive Signal Level (RSL) at Site ‘B’.
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 Eb/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 PSD ratio at Site ‘A’ and Site ‘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 Eb/No at Site ‘A’ and ‘B’.
 Measure/record RSL at Site ‘A’ and ‘B’.
 Now compare Eb/No in presence of two over lapping carriers with CnC with
Eb/No when only one carrier was ON. Eb/No variation should be within spec
for that modulation, FEC and PSD ratio.
5 The test can be repeated for different PSD ratio and Eb/No.