Wavecom W61PC V7.5.0 - Manual (Page 121)

WAVECOM Decoder W61PC/LAN Manual V7.5 Transmission Modes  111
Voice codec IMBE (Rate 7.2 kbps)
The common air interface of the APCO-25 Phase 1 system is described in TIA-102.BAAA-A. The devices
may use both the C4FM and CQPSK modulation techniques which can be demodulated with a single de-
modulator. The system uses frequency channels of 12.5 kHz bandwidth to transmit 9600 bits per second.
Analog audio is digitized by using the full rate IMBE vocoder (7.2 kbps) before transmission (TIA-
102.BABA).
The system allows group and individual calls, where each device has its own ID as well as one or more
talk-group IDs. Each call is marked as a group or individual call with its source and destination addresses.
The decoded voice calls can be monitored live using the default sound card of the system and they are al-
so automatically saved under the default Data-Output directory as .wav files. Live sound streaming can be
disabled using the mute button on the upper pane.
The contents of the decoded data packets are printed out as raw data and are not further analyzed.
The Offset should be set to the center frequency of the channel to be decoded. The Polarity of the signal is
detected automatically.
ARQ6-90 and ARQ6-98
ARQ6-90 and ARQ6-98 systems transmit 6 characters of 7 bits each in every data block resulting in a total
of 42 bits. The SITOR alphabet with a mark-space ratio of 3:4 is used.
Parameter Value
Frequency range HF
Operating modes Simplex ARQ
Modulation FSK
Symbol rate 200 Bd, variable 30-650 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Both systems operate on the ARQ principle. Using the ARQ method, a data block of 42 bits is transmitted.
The SITOR alphabet is used to protect the transmitted data. After each transmission the direction of
transmission is reversed and the remote station acknowledges error-free data or requests a repetition of
data received in error.
The two systems only differ in the duration of the request cycle interval.
A complete cycle for ARQ6-90 has duration of 450 ms of which the data block is 210 ms an interval is 230
ms.
A complete cycle for ARQ6-98 has duration of 490 ms of which the data block is 210 ms an interval is 280
ms.
ARQ-E
The ARQ-E duplex systems operate at Symbol rates of 46.2, 48, 50, 64, 72, 86, 96, 144, 184.6, 192, and
288 Baud on the radio link.
Parameter Value
Frequency range HF
Operation modes Duplex ARQ
Modulation FSK
Symbol rate 46.2, 48, 50, 64, 72, 86, 96, 144, 184.6, 192, and 288 Bd, variable 30-
650 Bd