Comtech EF Data SNM-1010L - Manual (Page 249)

SNM-1010L Data/Control Modem Revision 0
Specifications
MN/SNM1010L.OM
The minimum length is 48 bits (6 bytes). The maximum length is infinite from the
perspective of the base modem. However, operating as a MIDAS DAMA controller, the
maximum length is limited to 305 bits (38 bytes) of user data in order not to exceed a
55 millisecond burst window.
B.3.20.3 Transmit Postamble
When RTS transitions back to false, the modulator flushes the Encoder and sends the
End of Message pattern, turns Off the RF carrier and resets CTS back to false. The EOM
pattern is shown below.
6 symbols | 31 symbols | 31 symbols |
| | |
Flush | Unique Word’ | Unique Word’ |
Unique Word Prime I: 110 1100 1111 0100 1010 1110 0010 0000
Q: 110 1100 1111 0100 1010 1110 0010 0000
*Note: The Unique Word Prime is BPSK and uncoded.
B.3.21 Continuous Mode Modulator Specifications
The Continuous mode modulator is only used when the Data/Control Modem is
operating in Data mode.
B.3.21.1 Modulation and Encoding Types
B.3.21.1.1 BPSK Encoding
The modulator converts transmitted baseband data into a modulated BPSK carrier.
Using vector analysis of the constellation pattern, BPSK represents one symbol with the
carrier phase either at 0
° or 180°. The encoding characteristics for BPSK are provided in
the following table.
Code Rate Symbols/Bit Bps/Hz
1/1 1 2
1/2 2
0.5
5/16 3.2 0.3125
21/44 2.1 0.477
B.3.21.1.2 QPSK Encoding
B–7