Carrier-In-Carrier Commissioning And Deployment - Comtech EF Data CDM-750 Installation And Operation Manual

CDM-750 High Speed Trunking Modem
DoubleTalk Carrier-in-Carrier Option

8.4.7 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-CnC mode and all system issues – including external
interference, antenna pointing, cabling, and SSPA backoff – are resolved. Only
IMPORTANT after the link is robust should the user attempt turning on CnC.
The following procedure is recommended for CnC commissioning and deployment:
Step Procedure
1
Turn ON the carrier at Site A. Carrier from Site B is OFF. CnC function is OFF at
both sites.
2
Turn OFF the carrier at Site A. Turn ON the carrier at Site B. CnC function is OFF
at both sites.
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.
4
Now, without changing the transmit power levels, turn ON both the carriers (on the
same frequency) and turn CnC ON.
5
The test can be repeated for different SR ratios and modulation types.
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.
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.
Also verify that the RSL is within spec.
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.
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MN-CDM750