Today's amateur radio operator has several modes to chose from when operating. These modes include voice i.e. SSB, AM or FM and digital modes, i.e. CW, PACKET, PACTOR, PSK, MFSK, RTTY, SSTV and more. With the exception of CW, all digital modes require a control apparatus or interface between your radio and your computer.
There are also several software programs to chose from that allow you to operate in these modes. Some of the more popular ones that are in use are Airmail for PACKET and PACTOR and Mix-W for modes that make use of your computers sound card.
There is a system that is available to all amateurs that makes use of two of these digital modes. This is the Winlink 2000 system. (For more information go to www.winlink.org.) This system allows you to send and receive messages via standard email addressing and allowing you access to the Internet to forward these messages.
The Winlink 2000 system takes advantage of two of the more tried and tested digital modes, PACKET and PACTOR. THERE IS NO WINLINK DIGITAL MODE. Winlink 2000 requires access to the Internet for the forwarding or storage of all messages.
Stations that use the Winlink 2000 system normally use the client side software Airmail for preparing and sending messages. The stations that are Sysops (system operators) use proprietary software developed by the Winlink Development Team. Most of this software is in beta release, meaning that it may still have some problems that have yet to be resolved.
The essential parts of a digital station are the radio, the control/interface device and a computer capable of running the associate software. Most of the software for these digital modes are written for computers running Windows 98 or later. There is some software written for Linux-based computers and there may be a few programs for Mac computers but they are few and far between.
Digital modes used for formal messages, those that require a printed (hard) copy are PACKET and PACTOR. These modes allow for store-forwarding of messages between stations. Most other sound card modes don't have this capability.
PACKET and PACTOR modes require a Terminal Node Controller (TNC). There are some "Packet Engines" that can be used with your computer's sound card such as AGW, but they, in my opinion, leave something to be desired. PACTOR requires a TNC to transmit but some software like Mix-W has a PACTOR receive mode via your computers sound card. This allow for the reception of PACTOR 1 signals.
PACTOR today has 3 different speeds/modes referred to as PACTOR 1 (the original PACTOR mode), PACTOR 2 and PACTOR 3. PACTOR 2 and 3 require a SCS TNC/Modem and a proprietary license to use these modes. PACTOR 1 is available with the use of the AEA/Timewave PK-232 and several of the Kamtronics TNCs.
There are several TNC/Modems available for PACKET. Although PACKET is generally thought of as a VHF/UHF mode it may also be used on HF. The most common of the PACKET TNCs in use are the PK-88 by Timewave, the Kamtronics KPC-3+ and MFJ- 1278 (discontinued).
Digital operation can be lots of fun and a great asset to emergency communications when you are aware of its limitations. What it's NOT is the ONLY mode for EMCOMM. Digital is great for sending messages over long distances, depending on your stations capabilities but it will not deliver the message the last mile, this has to be done by a human operator.
The best way to learn digital, like any other mode, is through practice. Join local digital nets and participate in digital exercises to become proficient at operating in these modes and you will be ready when called on.
I hope this short primer will help to clarify the role of digital in amateur radio and will allow operators to know the difference between a mode and a system.