Packet-9600 - Wavecom W40PC Manual

The status field contains three fields with connection status information in addition to the call-
signs:
Frame types are indicated I, S or U.
Possible S-frame status messages, e.g. Receiver Ready (RR), Receiver Not Ready (RNR) or
Reject (REJ) are displayed.
In the third field the transmit and receive sequence number is displayed. This number ranges
from r0 to r7 or alternately s0 to s7. The sequence number indicates to the opposite station
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.

PACKET-9600

Parameter
Frequency range
System
Baudrate
Modulation
Receiver settings
Signal source
Alphabet
PACKET-9600 may be monitored in the amateur UHF and SHF bands. 2400 Baud
transmissions are more rare. Some digi-peaters support two modes, PACKET-1200 and
PACKET-9600.
To start PACKET-9600 select a baudrate. The correct shift may be set in the "Demodulator"
menu. The default value for the shift is 4800 Hz.
As PACKET-9600 uses direct FM modulation, the translation frequency pre-selection is equal
to the center frequency of the IF input. Some digi-peaters offset their transmit frequency up to
1.000 Hz from their normal frequency and this introduces many reception errors. The
frequency offset is compensated by changing the translation frequency.
The packet radio protocol is a derivative of the X.25 and HDLC computer network protocols.
Through the effort of American radio amateurs (TAPR) low cost equipment has become easily
available and packet radio has become very popular. Packet radio is a synchronous system, and
data is ASCII characters. Information is transferred in blocks (frames).
At the start and end of each block a control character or flag (01111110) is sent. The address
can consist of up to 80 characters but 16 or 24 addresses are most common when using direct
connections or a single repeater.
The packet protocol distinguishes between three frame types: I, S and U frames. Actual data
transfer takes place using the I (Information) frame and very seldom the U (Unnumbered)
frame. The S (Supervisory) and U frames are used for transmission control.
The data field can contain up to 256 characters in packet radio. All characters and character
combinations are permitted since transmission is transparent. A checksum is sent in the FCS
field.
The status field contains three fields with connection status information in addition to the call-
signs:
In the third field the transmit and receive sequence number is displayed. This number ranges
from r0 to r7 or alternately s0 to s7. The sequence number indicates to the opposite station
168 • Transmission Modes
Value
VHF/UHF
Amateur AX.25 System
2400, 4800 or 9600 Baud
DIRECT-FM
FM 15 kHz, narrow
HF
ITA-5 with block coding
•
Frame types are indicated I, S or U.
•
Possible S-frame status messages, e.g. Receiver Ready (RR),
Receiver Not Ready (RNR) or Reject (REJ) are displayed.
WAVECOM Decoders v6.15 W40PC, W41PC, W51PC