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Appendix L
CDM-760 Advanced High-Speed Trunking Modem
c. Turn DPD function OFF and compare the measured Es/No and BER, assuming the
demodulator is able to achieve lock.
6. Initiate service:
a. Turn DPD back to LOCAL.
b. Disable BER test mode.
L.4.1.2
Remote DPD Commissioning and Deployment
Comtech EF Data recommends the following procedure for remote DPD commissioning. In this
procedure, DPD is applied to the link originating from Site A. DPD training is conducted at Site B.
Since the bandwidth of the link originating from Site B is expected to be below 20 Msps, DPD
will not be applied to this carrier even though DPD will be 'enabled' at this site.
Do these steps:
1. Setup the transmit configuration at both sites.
a. Site A should use a modulation and coding (ModCod) scheme with slightly lower
spectral efficiency than expected to close the link.
b. Leave the DPD function OFF at both sites.
2. Turn ON the carrier at both sites. Leave the DPD function OFF at both sites.
a. Setup the receiver configuration at both sites.
b. Verify that the demodulators are locked at both sites.
c. Verify that the received signal level at both sites are within specifications.
d. Measure/record the Es/No at Site B.
3. Turn the DPD function to REMOTE at both sites.
a. After the demodulators have locked, wait 30 seconds to allow the predistorter to fully
converge to the current transponder conditions.
b. Measure/record the DPD compensation at Site A.
c. Measure/record the Es/No and compare to previous result without DPD. If the DPD
compensation level is low <1.0 dB, then the Es/No improvement may be small since the
transponder is not driven deep into compression yet.
d. Enable the BER test mode.
4. Follow the flow chart to maximize spectral efficiency and optimize the uplink power at Site A
only.
L–9
Revision 4
MN-CDM760
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