Wavecom W61PC V7.5.0 - Manual (Page 216)

206  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
If more than two identical digits are to be transmitted, the repetition tone is appended to the digit tone
(e.g. 22222 is transmitted as f2 fw f2 fw f2, where f2 is the tone for "2" and fw is the repetition tone).
In most systems the accuracy of the single frequencies has to be within +1/-1.5% of the nominal value.
For ZVEI modes having nominal tone durations of 70 ms, the duration of a single tone may vary ± 15 ms.
Decoding the selective calls is started by clicking on a system. If transmission and system selection con-
form, the call sign is displayed on the monitor. In the Options menu a Time stamp function can be ena-
bled to add date and time to each call.
Tone Allocation
Digit Hz Digit Hz
0 2400 8 2000
1 1060 9 2200
2 1160 A 970
3 1270 B 810
4 1400 C 2800
5 1530 D 885
6 1670 E 2600
7 1830 F 680
Tone duration: 70 ms
ROBUST-PACKET
Robust-Packet (RPR, Robust Packet Radio) is a data transmission mode devised from Special Communica-
tions Systems GmbH & Co. KG. It is optimized for the deployment in the short wave band. To accommo-
date the characteristics of this frequency range, for example fading and multipath propagation, a eight
carrier OFDM was used.
Parameter Value
Frequency range HF
System OFDM, FEC, CRC
Modulation OFDM with DQPSK and DBPSK
Center frequency 1500 Hz
Shift 420 Hz
Symbol rate 200 Bd and 600 Bd adaptive
Receiver settings Data, CW, LSB or USB
Input format(s) AF
Additional Info AX.25 data, APRS
Dependent on the speed level (r200 or r600) every carrier is DBPSK or DQPSK at a rate of 50 Bd modulat-
ed. Just like in PACKET-RADIO the AX.25-protocol comes into operation. The decoder module detects the
speed level and the size of the transmitted packet automatically and shows the result. The payload of one
packet can be up to 256 Byte. The real length of one data packed depends on the amount of data to be
send. There are 25 different packages. One for connect/disconnect and respectively 12 for the two speed
levels with their variable packet length.
To make the transmission as robust as possible, there are several modifications applied onto the AX.25-
data stream before the transmission. The call signs are compressed with a special algorithm, the data
stream is scrambled, redundancy is added and it is interleaved over the full frame length.