Wavecom W40PC, Manual

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WAVECOM Decoders v6.15 W40PC, W41PC, W51PC Transmission Modes
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which packets have been received free of errors. The large volume of available radio amateur
literature is recommended for further study of the packet radio system.
PACTOR
Parameter Value
Frequency range HF
System STANDARD, Simplex ARQ System
Baudrate(s) 100.0 or 200.0 Baud adaptive
Modulation SSB or DIRECT-FSK
Receiver settings CW, LSB or USB
Signal source(s) AF, HF or IF
Alphabet ITA-5 with block coding
PACTOR operates as a bit synchronous simplex system in a fixed timing cycle. The entire
cycle length is 1.25 seconds and the packet length 0.96 seconds. Consequently the correlation
amounts to 250 bits at 200 Baud. The change-over time and signal propagation delay limits the
system’s range to approximately 20'000 km.
The PACTOR data block consists of three sections: Header, data and control (status and 16 bit
CRC). At 100 Baud the data field is 64 bits and at 200 Baud it increases to 160 bits. Block
coding is performed according to the CCITT standard starting with the data section.
PACTOR operates adaptively so the baudrate can be either 100 or 200 Baud. During day time
200 Baud may be successfully used. In the evening, however, strong propagation distortion
occurs which necessitates a reduction of the baudrate to 100 Baud.
PACTOR includes HUFFMAN data compression by design. This scheme relies on the fact that
frequently occurring characters e.g. space, e, n or i, can be represented with shorter bit
combinations than characters which are rarely used. A compression factor of approximately
1.7 is achieved in comparison to uncompressed ASCII.
Looking purely at monitoring, the Huffmann code has the disadvantage that compression
synchronization may be lost during propagation disturbances and so the remaining text in the
data block is also lost.
PACTOR is a frequent visitor in the amateur radio bands. In addition, commercial users also
use this system. The data protocol was modified into several variants for this purpose. The
WAVECOM software automatically detects and decodes versions 1 to 8.
Detailed descriptions of the PACTOR protocols can be obtained in the radio amateur literature.
It must however be pointed out that real-world PACTOR implementations differs considerably
from these descriptions.
PACTOR-II
Parameter Value
Frequency range HF
Frequency Europe 7.035 MHz, 14.070 MHz
System SIMPLEX, ARQ System
Baudrate(s) 100.0 Baud
Carrier Modulation Two channel DBPSK, DQPSK, D8PSK, D16PSK
adaptive
Block length Short / long block, adaptive
Modulation SSB
Receiver settings CW, LSB or USB