Comtech EF Data CDM-625A - Manual (Page 152)

CDM-625A Advanced Satellite Modem MN-CDM625A
Front Panel Operation Revision 3
6–26
CONFIG: Rx  FEC  Diff Encoder On
When you select Differential Decoding as OFF, there is no way for the modem to
resolve the phase ambiguities associated with PSK modulations. For BPSK there is a
50% chance that the polarity of the data will be correct. In QPSK there is a 25%
chance that the data will be correct.
Enc=None (None,Vit,Seq,TCM,TPC,LDPC,VFEC)
Diff Encoder=On (Off,On) ()
6.2.1.4.4 CONFIG: Rx  Demod (Demodulation)
Demod=QPSK (B,Q,OQ,8PSK,16QAM)
FEC Rate=1/2 (1/2,3/4,7/8) ()
Use the ◄ ► arrow keys to select Demod (top line) or FEC Rate (bottom line). Press ENTER.
Then, for either, use the ▲▼ arrow keys to select the setting. The Decoder type selected
dictates the FEC Rate selections:
Decoder Type Modulation Type FEC Rate Choice
No Encoder
BPSK Fixed at 1/1
QPSK, OQPSK Fixed at 1/1
Non-Turbo Encoder
BPSK Fixed at 1/2
TCM 8-PSK (FAST option) Fixed at 2/3
QPSK, OQPSK 1/2, 3/4, 7/8
16-QAM (Vit+RS only) 3/4, 7/8
TPC
(with TPC/LDPC hardware option
installed)
BPSK 5/16, 21/44
QPSK, OQPSK 1/2 (aka 21/44), 3/4, 7/8, 0.95
8-PSK (FAST option) 3/4, 7/8, 0.95
16-QAM (FAST option) 3/4, 7/8
LDPC
(with TPC/LDPC hardware option
installed)
BPSK Fixed at 1/2
QPSK, OQPSK 1/2, 2/3, 3/4
8-PSK, 8-QAM (FAST) 2/3, 3/4
16-QAM (FAST option) Fixed at 3/4
VFEC
BPSK Fixed at 0.488
QPSK 0.533, 0.631, 0.706, 0.803
8-QAM (FAST option) 0.576, 0.642, 0.711, 0.780
16-QAM (FAST option) 0.644, 0.731, 0.780, 0.829, 0.853
ULL
(VersaFEC Ultra-Low Latency)
BPSK Fixed at 0.493
QPSK 0.493, 0.654, 0.734
VF2L (VersaFEC-2 Long Block) or
VF2S (VersaFEC-2 Short Block)
BPSK Fixed at 0.489
QPSK
0.489, 0.537, 0.586, 0.611, 0.635,
0.660, 0.684, 0.733