Wavecom W74PC V8.7.0 - Manual (Page 127)

WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V8.7.0 Transmission Modes
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Transmission Modes
ACARS
Aircraft Communications Addressing and Reporting System (ACARS) is a carrier sensing, multiple access
packet radio system for aircraft communications. ACARS operates in the VHF band, mainly around 130
MHz, using 2400 bps NRZI coded coherent audio frequency MSK (Minimum Shift Keying - a particular form
of FSK) on AM to make use of standard aircraft AM communications equipment.
Parameter Value
Frequency range VHF
Operation modes CSMA/CD packet ARQ system
Modulation AM, SUB FSK
Symbol rate 2400 Bd
Center frequency 1800 Hz
Shift 1200 Hz
Receiver settings AM, BW = 3 kHz
Input format(s) AF, IF
Additional Info ITA-5 with parity and block coding
Frequencies Europe: 131.725, 131.525, 131.825 MHz
Frequencies USA: 131.550, 130.025, 129.125, 131.475, 130.450,
131.125, 136.700, 136.750, 136.800 MHz
Frequency Japan: 131.450 MHz
To receive ACARS an omni-directional 108-136 MHz antenna, a VHF AM receiver (scanner) with 13 kHz
channel bandwidth and a corresponding AF output is necessary. As the ACARS packets are very short, turn
the squelch of the receiver OFF.
Speed selection is not available for ACARS as only one speed is in use (2400 Baud).
Processing of ACARS Messages
It is possible to do some interpretation of ACARS messages. The following options are available:
Reassemble multipart messages
This setting enables the reassembling of bigger messages which are sent in several parts. Instead of
showing each part separately, the message is shown as one single message when the last part has been
received. The message header is still shown separately for each part.
Parse ADS-C messages
This setting enables the parsing of ADS-C messages (Automatic Dependent Surveillance - Contract). When
an ADS-C message is received, it is decoded and the additional information is shown in the output win-
dow.