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Digital Primer
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.