Amtor/ pactor/ clover/ g-tor/ psk31, Slow scan tv/ facsimile – Kenwood TS-2000 User Manual
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11 SPECIALIZED COMMUNICATIONS
AMTOR/ PacTOR/ CLOVER/ G-TOR/ PSK31
Besides Packet and RTTY, digital modes which have
been used among hams include AMTOR, PacTOR,
CLOVER, G-TOR, and PSK31. This manual does not
describe much about these modes. For details,
consult reference books about Amateur Radio.
AMTOR (AMateur Teleprinting Over Radio) has
brought amateur HF digital communication into the
computer age. It is the first error-free HF digital mode
by which data bursts (not steady stream of data) are
transmitted.
PacTOR (Packet Teleprinting On Radio) has
combined the best features of both AMTOR and
Packet to improve the efficiency of HF digital
communications. Like Packet and AMTOR, PacTOR
sends error-free data using a handshaking method.
Of all the Amateur Radio HF digital modes, CLOVER
offers the best overall performance using a
complicated modulation technique, automatic power
adjustment and other advanced features. It may
allow communications to be maintained under the
worst conditions.
G-TOR (Golay-coded Teleprinting Over Radio) is a
relatively new Amateur Radio digital mode currently in
use. G-TOR
was developed specifically to handle the
adverse conditions of communicating, across the
solar system, with spacecraft during their missions.
PSK31 was developed by an RTTY enthusiast,
G3PLX, in the Great Britain. The operating technique
is very similar to the conventional Baudot-RTTY,
although more sensitive fine-tuning is required, as a
PSK31 signal requires a tuning accuracy of a few
Hertz. A special feature of PSK31 is that it allows the
entire ASCII character set, including the back space
character.
Your MCP should handle some or all of the above
modes. For available modes on your MCP, consult
the instruction manual for the MCP. For the cable
connections, see “MCP AND TNC” {page 95}.
On most HF bands, audio frequency shift keying
(AFSK) is used for the above modes. This method of
modulation uses audio tones therefore either LSB or
USB mode should be selected. Traditionally, LSB is
used, similar to RTTY, with the exception of AMTOR
which is normally operated in USB.
AMTOR activity can be found on or near 14075 and
3637.5 kHz. These are also good starting places
when searching for PacTOR, CLOVER, G-TOR, or
PSK31 stations.
Note: When using SSB mode for digital operation, use a fast AGC
setting and switch your Speech Processor OFF.
SLOW SCAN TV/ FACSIMILE
Slow-scan Television (SSTV) is a popular application
for transmitting still images over the air, from one
station to another. Instead of trying to describe your
station, simply showing it is much faster. Transmitting
images over the air requires a scan converter,
besides a transceiver. A scan converter transforms
images taken with a video camera into audio signals
that can be fed into your transceiver. The recipient’s
scan converter transforms audio signals back into
video images so that he or she can view them on a
TV set.
Nowadays instead of a scan converter, many hams
use a personal computer, a software application, and
an interface attached to the transceiver. This is much
cheaper, more flexible, and does not require a TV set.
In recent years, many low cost digital cameras have
become available. You can transfer images from
these cameras into your computer.
For further information, consult reference books about
Amateur Radio. The frequencies (measured in kHz)
commonly used for SSTV operation are listed below:
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—
Fax (facsimile) is one of the original image
transmission modes. Using this mode allows you to
exchange more detailed graphics than SSTV.
Amateur Radio fax functions much like old analog fax
systems. It scans paper and converts acquired
image data into a series of tones representing white
and black portions of the image. Because fax
requires longer transmission time, you should use it
only when band conditions are stable with strong
signals.
Popular fax frequencies include the following:
•
7245, 14245, 21345 (International Net), and
28945 kHz
Operating on SSTV or fax mainly involves learning
the functionality of your computer application or
accessory hardware that supports these modes.
Consult the instruction manual that comes with your
software or accessory equipment.
Note: When operating either SSTV or fax, use a fast AGC setting
and switch OFF your Speech Processor, for best results.