Wavecom W40PC, Manual

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Transmission Modes WAVECOM Decoders v6.15 W40PC, W41PC, W51PC
Modulation SSB or DIRECT-FSK
Receiver settings CW, LSB or USB
Signal source(s) AF, HF or IF
Alphabet ITA-3
SI-FEC operates at speeds of 96 and 192 Baud on the radio link.
SI-ARQ stations can switch to FEC broadcasting operation in similarity to SITOR-ARQ
(Mode A) and SITOR-FEC (Mode B).
The SI-FEC sound is similar to the sound of SITOR-FEC. However, SI-FEC is used very
seldom and stations mostly switch to this mode only under extremely poor propagation
conditions.
The SI-FEC mode uses the ITA-3 alphabet for data protection. Each character is sent twice, but
with a time delay. The repeated character is transmitted with inverted polarity.
For a pair of characters which have been decoded and recognized as error-free one character is
displayed. If both characters are received in error the underscore (_) character is displayed.
SI-AUTO
Fully automatic tuning to signal center, shift and transmission modes SI-ARQ (Mode A) and
SI-FEC (Mode B) may be achieved by selecting “SI-AUTO” mode.
SITOR-ARQ
Parameter Value
Frequency range HF
System SIMPLEX
Baudrate(s) 100.0 Baud
Modulation SSB or DIRECT-FSK
Receiver settings CW, LSB or USB
Signal source(s) AF, HF or IF
Alphabet Sitor
Sitor systems almost exclusively operate at a speed of 100 Baud and with a shift of 170 Hz.
After the receiver has been correctly tuned, the SITOR mode may be started by selecting a
baud rate.
Fully automatic tuning to the signal center and shift may be achieved by selecting the “Auto”
button.
SITOR-ARQ is a simplex system where both stations transmit alternately on the same
frequency.
The CCIR recommendation 476-3 defines a cycle of 450 ms and the two stations are
designated as follows:
ISS - information sending station and IRS - information receiving station.
The WAVECOM software always decodes the information of the ISS station.
The SITOR 7 bit alphabet employs a 3:4 mark-space ratio. The ISS transmits blocks of 210 ms
duration each containing 21 bits. In turn the IRS transmits acknowledgement bursts with a
duration of 70 ms.
If the ISS does not receive an acknowledgement, a block containing the RQ character is sent.
In the case of blocks being received in error by the IRS, the last data block sent is repeated.