Si-Arq; Si-Fec - Wavecom W40PC Manual

In RUM-FEC mode the signal polarity (sideband) can be manually selected by toggling the
"Polarity" item in the "Demodulator" menu. If polarity changes during a transmission,
synchronization will not be lost.

SI-ARQ

Parameter
Frequency range
System
Baudrate(s)
Modulation
Receiver settings
Signal source(s)
Alphabet
SI-ARQ operates at speeds of 96, 192 or 200 Baud on the radio link.
SI-ARQ is a simplex system similar to for example SITOR. SI-ARQ therefore also sounds
similar to the well-known SITOR system. Because data and pause blocks are longer in
duration, the perception of a lower baud rate is created.
SI-ARQ uses the ITA-3 alphabet for data transmission and error detection. Data blocks usually
consist of 5 or 6 characters.
One transmission cycle is made up of twice the length of a character block. If the information
sending station (ISS) receives an acknowledgement character, the next data block is sent with
inverted phase or polarity. However, if the receiving station (IRS) requests a retransmission,
the repeated block is sent with unchanged polarity.
If the ISS does not receive the acknowledgement packet, it transmits a RQ block as is the case
with SITOR.
The software automatically detects SI-ARQ block lengths of four, five or six characters and
displays this information after phasing has been achieved. The polarity of the signal is
automatically detected.
Transmission Sequence of SI-ARQ at 96 Baud with Five Characters

SI-FEC

Parameter
Frequency range
System
Baudrate(s)
WAVECOM Decoders v6.15 W40PC, W41PC, W51PC
Value
HF
SIMPLEX
96.0, 192.0 and 200.0 Baud
SSB or DIRECT-FSK
CW, LSB or USB
AF, HF or IF
ITA-3
Value
HF
FEC
96.0 and 192.0 Baud
Transmission Modes • 183