43

9 SPECIALIZED COMMUNICATIONS

AMTOR/ PacTOR/ CLOVER/ G-TOR/ PSK31

Besides RTTY, digital modes which have been used
among hams include AMTOR, PacTOR, CLOVER, G-
TOR, and PSK31. For details, consult reference
books about the digital mode communications of
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 United Kingdom. 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, refer to “MCP AND TNC” {page 78}.
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 kHz
and 3637.5 kHz. These are also good starting places
when searching for PacTOR, CLOVER, G-TOR, or
PSK31 stations.
The TS-480 transceiver has special DSP filters for
these digital modes. Refer to page 48 for details.
Note:
When using SSB mode for digital operation, use a fast AGC
setting and switch your Speech Processor OFF.

PACKET RADIO

Packet is a unit of data transmitted as a whole from
one computer to another, on a network. Packets can
be transmitted on radio waves as well as on
communications lines. Besides a transceiver and a
computer, all you need is a terminal node controller
(TNC) or Multimode Communications Processor
(MCP). One of the tasks of TNCs and MCPs is to
convert data packets to audio tones, and vice versa.
Connecting a TNC to this transceiver allows you to
use many packet applications.
A variety of packet applications developed by hams
include packet bulletin board systems (PBBSs).
PBBSs are created and maintained by volunteers
called System Operators (SysOp). You may access
one of your local PBBSs to send e-mail, download
files, or obtain various useful information. Thousands
of PBBSs, which have formed a worldwide network,
relay e-mail to their intended destinations around the
world.
When you access a local PBBS for the first time, you
often need to register as a new user. After you are
successfully registered, it will then be available as
your home PBBS. E-mail addressed to you will be
held under a directory, called a mailbox, on your
home PBBS.
For further information, consult reference books
which should be available at any store that handles
Amateur Radio equipment. Web pages relating to
Packet will also be helpful. On Internet search
engines, use “Packet Radio” as key words to find
those Web pages.
Note:
◆
Unlike a TNC, a Multimode Communications Processor (MCP)
serves as a communications interface in several digital modes
such as Packet, RTTY, and AMTOR. You can cause it to switch
among the modes by sending a single command from your
computer.
◆
If there is an amateur radio club in your area, consider becoming
a member. You can often learn more in an hour from
experienced hobbyists, than in a month of independent research.
Ask on the local repeaters or contact your national amateur radio
organization (the ARRL in the U.S.A.) for information on local
amateur radio clubs. You’ll be glad you did.
PBBS