Here is a brief history of digital modes for the newer hams out there. It can be divided into four eras.

1.  First there was the original form of digital communication—CW, but it was not usually referred to as digital. The next form of digital mode was RTTY, using old surplus mechanical teletype machines (TTY) and a simple electronic interface know as a MCU (originally built with tubes.)  Next came SSTV with its complex self contained interfaces which often cost more than most hams wanted to invest.

2.  The TNC era was heralded by the introduction of Packet Radio by TAPR in 1982. TNCs (Terminal Node Controllers) allowed users to send information in a digital format using a communication protocol similar to those used in computer networks. To operate packet on VHF, a ham needed an FM radio, a dumb terminal and a TNC. The TNC created packets of information from the terminal, added addressing information and then sent a modulated tone and PTT (push to talk) to the radio’s microphone input jack. On the receiving end the radio fed the received modulated tones to another TNC. The TNC then reassembled the message by arranging individual packets of information. The TNC then sent information to the dumb terminals screen to read by receiving ham. The TNCs also had the ability to request resending of information for error free communication, forward messages to a remote TNC via a number of Nodes (individual repeating packet stations) and even act as a mailbox. These advanced characteristics brought hams electronic mail and mailboxes well before the Internet boom of late 90’s.

3.  The next advance was the addition of addition mode capabilities to the TNCs, now more properly described as Multimode Controllers. These additional modes included an easy non-mechanical way to send and receive RTTY. Also added were HF Packet, AMTOR, CW and even SSTV and FAX. For more information on these variety of digital modes visit the ARRL’s Digital Modes TIS. Commercial multimode controllers have been produced by Kantronics, MFJ, AEA, Tigertronics and others (as many fine units are no longer in production you may want to visit the reviews section of e-Ham for variety of units.) Most multimode were able to function using dumb terminals or terminal emulation programs on computer, this was often referred to as Terminal Mode operation. To take advantage of additional features special pieces of software were written work with computer. These proprietary softwares allowed  Host,  KISS  and other modes for operating multimode controllers .

4. Sound Card Era—As computers became cheaper, more powerful and most of them began to sport sound cards as standard equipment, the idea of moving the processing of signals from the multimode control into the computer became practical. Once the processing was moved to the computer, the ability to develop new modes blossomed since all that was needed was software programming. With sound card modes, only very simple generic interfaces between the computer and radio are required (mainly for the purpose of signal isolation, PTT function and audio level control.) The sound card era has not completely ended the Multimode Controller Era, as many users still prefer the features of multimode controls, some prefer the ability to use inexpensive laptops with no sound cards and some specialised modes still require multimode hardware interfaces.