Comtech EF Data CDM-600 Installation And Operation Manual page 77

CDM-600 Satellite Modem
Front Panel Operation
CONFIG: RX: DECODER
DECODER = VIT NONE,VIT,SEQ,TCM,TPC,LDPC)
REED-SOLOMON = OFF (ON,OFF)
Select the parameter to edit using the [←] [→] arrow keys.
The Decoder options are shown in the parentheses. Select using the [↑] [↓] arrow keys,
then press ENTER. The choices are:
•
Viterbi
•
Sequential
•
Trellis Coded Modulation - 8-PSK Rate 2/3 only (FAST option)
•
TPC (Turbo) (Hardware option)
•
None (uncoded)
•
LDPC (Hardware option)
Select ON or OFF for Reed-Solomon using the [↑] [↓] arrow keys, then press ENTER. If
Reed-Solomon is ON, proceed to the next menu.
If NONE is selected, the bottom line of the display will change from the RS selection to
the Differential Encoding selection, as shown below:
DECODER = NONE (NONE,VIT,SEQ,TCM,TPC,LDPC)
DIFF-DECODER= OFF (ON,OFF)
IMPORTANT
Note: This option of decoding is only displayed if
the TPC/LDPC Codec is installed.
If the user selects Differential Decoding = OFF, there is no way for the
modem to resolve the phase ambiguities associated with PSK
modulations. For BPSK there is a 1 in 2 chance that the polarity of the
data will be correct. In QPSK there is a 1 in 4 chance that the data will
be correct.
6–15
Revision 7
MN/CDM600.IOM