Packet Radio, Specialized Communications

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.

PBBS

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.