Wavecom W74PC V8.7.0 - Manual (Page 169)

WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V8.7.0 Transmission Modes
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159
Digit Hz Digit Hz
1 697/1209 9 852/1477
2 697/1336 A 697/1633
3 697/1477 B 770/1633
4 770/1209 C 852/1633
5 770/1336 D 941/1633
6 770/1477 * 941/1209
7 852/1209 # 941/1477
Tone duration: 70 ms.
DUP-ARQ
DUP-ARQ is a semi-duplex system. The radio channel is used by a DUP-ARQ system in the same way as a
simplex system, both stations alternating in transmitting blocks of five characters and a Hamming check-
sum. If a transmission error occurs a repeat request is initiated and the last data block is re-transmitted.
Parameter Value
Frequency range HF
Operation modes Semi-duplex ARQ
Modulation FSK
Symbol rate 125 Bd, variable 30-650 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info ITA-2 with block coding
DUP-ARQ operates at a Symbol rate of 125 Bd on the radio link.
If only one station is sending data, the other station transmits an IDLE pattern and initiates RQ cycles in
case of transmission errors.
DUP-ARQ has automatic channel selection facilities. Before transmission starts, the best available short-
wave transmission channel is selected and its quality is continuously checked for the duration of the
transmission. Within a given frequency range the system may select one of 5 possible channels which are
spaced at 400 Hz intervals. Because of this channel selection mechanism, the two linked stations may
transmit at different frequencies.
The polarity of the bit stream (upper sideband (USB) or lower sideband (LSB)) cannot automatically be
derived from the signal. Polarity may be manually selected by using the Polarity menu field. Polarity in-
version does not cause a loss of signal synchronization.