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 |
|
Receiver settings |
DATA, CW, LSB or USB |
|
Input format(s) |
AF, IF |
|
Additional Info |
ITA-2 with parity and identification bit |
ARQ-E synchronization may be started by the selection of a baud rate. An AUTO program start causes the automatic determination of the frequency shift and baud rate to be executed first. The signal polarity (USB or LSB sidebands) is automatically detected.
After synchronization to an ARQ-E system has been achieved, the detected repetition rate is displayed (4, 5 or 8 cycles). This parameter may give clues to the identity of the transmission.
If a continuously repeated character (often FFFF) is decoded whilst working in the ARQ-E mode, it is most likely an ARQ-E3 system being monitored. ARQ-E employs the ARQ-1A alphabet with parity checking which allows the detection of transmission errors.
Full-duplex systems transmit a RQ character after having detected an erroneous character or in the presence of excessive signal distortions. The remote station subsequently repeats the last three, four or seven characters preceded by the RQ character.
To maintain synchronization between the two stations both transmitters operate continuously and send the idle bit pattern if no traffic is transmitted.