214
Transmission Modes
WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
Parameter
Value
Operation modes
Simplex ARQ
Modulation
FSK
Symbol rate
100.0 and 200.0 Bd adaptive
Receiver settings
DATA, CW, LSB or USB
Input format(s)
AF, IF
Additional Info
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. For longer distances, a special longpath mode exits, which has longer breaks between frames
and thus allows for distances up to 40,000 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 ac-
cording to the CCITT standard starting with the data section.
PACTOR operates adaptively so the baud rate 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 necessi-
tates a reduction of the baud rate to 100 Bd.
PACTOR includes HUFFMAN data compression by design. This scheme relies on the fact that frequently oc-
curring 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 uncom-
pressed ASCII.
Looking purely at monitoring, the Huffman 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.
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 descrip-
tions.
This mode can also be used to decode connect frames for higher PACTOR levels, as well as frames of the
free signal protocol.
Options | CRC Recognition.
The detected CRC is displayed in the decoder status bar, see “
” on page 39.
Using
Options | CRC Table
a certain CRC mask can be defined, see “
” on page 39.
PACTOR-FEC
PACTOR-FEC is a bit synchronous simplex system and is based on PACTOR.
Parameter
Value
Frequency range
HF
Operation modes
Broacast, FEC
Modulation
FSK
Symbol rate
100 and 200 Bd
Shift
200 Hz
Receiver settings
DATA, CW, LSB or USB
Input format(s)
AF, IF
Additional Info
ITA-5 with block coding
