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G-TOR Mode
G-TOR, short for Golay-TOR, is an innovation of Kantronics, G-TOR was implemented in the KAM
Plus and Enhancement Board for the KAM in early 1994 and establishes a completely now hybrid-
ARQ HF digital communications system for the amateur service. Golay error correction coding
forms the basis for G-TOR.
The benefits of G-TOR are exceptional compared to previous multi-mode HF digital modes: 1) sub-
stantially higher effective data rates (throughput), 2) apparent reduction in the effects of interfer-
ence and multi-path, and 3) low cost for error-correcting systems. The key features of G-TOR are a
typical: 1) extended Golay forward error correction coding, 2) full-frame interleaving, 3) on-de-
mand Huffman and run-length encoding, 4) link-quality-based baud rate: 300, 200, 100, 5) 2.4
second hybrid-ARQ cycle, 6) reduced data frame overhead, and 7) use of standard AFSK tone pairs
(mark and space).
G-TOR operates as a synchronous ARQ mode, like AMTOR and PACTOR. At 300, 200, or 100 baud,
G-TOR's ARQ cycle remains at 2.4 seconds, All data frames are 1.92 seconds in duration and con-
tain one control byte and two checksum bytes (CRC). Data frames contain 69, 45, and 21 data
bytes at 300, 200, and 100 baud respectively. Acknowledgments are 0.160 seconds in duration.
The effective performance of two stations linked in G-TOR relies on the combined use of forward
error correction, data interleaving, and its ARQ cycle with CRC checking. Operation in the G-TOR
mode is described in the following sections.
G-TOR activity, at present, is found on all the HF bands near AMTOR and RTTY. CW will typically be
found at the bottom of each band while AMTOR, RTTY, G-TOR, and PACTOR are higher up the
band in frequency. For example, on 20 meters, activity can generally be found as listed below.
Note that G-TOR, PACTOR, and AMTOR may tend to overlap.
CW 14.000 – 14.070 MHz
AMTOR, G-TOR, PACTOR 14.070 – 14.085 MHz
RTTY 14.080 – 14.095 MHz
PACKET 14.095 – 14.111 MHz
G-TOR Operation
The G-TOR protocol is a linked mode where two stations are communicating with each other.
Although the G-TOR Mode does not incorporate a broadcast mode, G-TOR uses AMTOR FEC for its
broadcasts (from G-TOR Standby), such as calling CQ. If you have the MONITOR command turned
on when you enter the G-TOR Mode, you will be able to monitor AMTOR FEC transmissions.
The following example illustrates G-TOR operation with your KAM Plus:
Turn the MONITOR command ON by typing MONITOR ON at the command prompt (cmd:) and
press return. This will enable you to copy CQ calls.
The G-TOR Mode will follow the setting of the SHIFT commands in your KAM Plus. For instance, if
shift is set to 170, 425 or 850, the mark frequency used for G-TOR will be 2125 Hz, and the space
will be above the mark by selected shift. If the SHIFT command is set to MODEM, G-TOR will use
the tones selected with the Mark and SPACE commands.
Next, place your KAM Plus in G-TOR Mode by typing GTOR at the cmd: prompt and pressing re-
turn. Your KAM Plus will respond with <GTOR STANDBY>. If you now tune your KAM Plus to a sta-
tion transmitting AMTOR FEC, you'll be able to copy that transmission. You'll also be ready to re-
ceive a link request from another station.
To call CQ, type [
Ctrl-C][T] (that's a control-c followed by the letter T). Your KAM Plus will enter
the AMTOR FEC transmit mode, key your radio, and start transmitting. Type your CQ message on
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