Wavecom W61PC V7.5.0 - Manual (Page 140)

130  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
Parameter Value
Frequency range HF
Operation modes Half-duplex ARQ
Modulation PSK2A, PSK4A, PSK8A, PSK16A, ASK2PSK8, ASK4PSK16, 2DPSK2A
8 tones
Symbol rate 8 x 62.5 Bd
AFC ±400 Hz, with max. single step ±15 Hz
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info ITA-5, Optional Mode
RS coding is utilized to correct transmission errors. Four coding levels (called RS Efficiency) are specified,
which allow for more or less error correction within a block. The percentages in the following list of coding
levels, relate the number of information symbols (user data) to the block length, a block comprises user
data and parity check symbols:
 ROBUST: 60%
 NORMAL: 75%
 FAST: 90%
 OFF: 100% (i.e. no error correction)
The level of RS Efficiency is automatically detected by the demodulator.
After successful synchronization, it may take up to a minute before any text is output in the GUI.
Using Options | CRC Table a certain CRC mask can be defined, see “ CRC Table ” on page 31.
The Options | Display Mode provides the options to display All Frames or Error free Frames, which
means frames with the correct CRC check.
CODAN-SELCAL
The mode was developed by the Australian CODAN PTY. and is very similar to GMDSS/DSC.
Parameter Value
Frequency range HF
Operation modes Digital Selcal
Modulation FSK
Symbol rate 100.0 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info ITU R M.493 alphabet
CODAN SELCAL operates with 100.0 Bd and can be started by selecting the mode.
A preamble of at least 100 dot reversals, which are 50 changes between "0" and "1" (low and high bit),
precedes the data block. This lead-in has duration of 2.0 seconds. Digital MARK "1" is represented by a
frequency of 1870 Hz and SPACE by 1700 Hz.
The dot pattern is followed by a word synchronization sequence called the "phasing preamble". The char-
acters no. 125 and no. 108 are alternately transmitted for 1.2 seconds.
This sequence is followed by the data block with different control characters and the message. Each data
byte consists of 7 data bits and 3 parity bits. Thus the duration of each character is 100 ms.