Digital Modes – Basics

Digital Mode Overview

RTTY has long been the standard way to communicate via a keyboard, and could be considered the first “digital” mode. But today (2018), there are a whole bunch of different digital modes based on software that can be used to communicate via keyboard and computer screen. (We aren’t talking about the digital protocols used to control repeater networks, etc.)

Over the past few years, there have been a number of digital protocols available, and they have been improving over the years. Some of these modes include RTTY, PSK31, Olivia, JT-65, and the newest, FT8.

Basically, almost all of the digital modes encode a message (usually text based) into an audio signal that is generated by  software on a computer connected to the microphone and speaker signals of your transceiver, transmitted (normally over SSB) , and the received signal is then decoded by the software. Often, the associated software can also generate control signals for your transceiver (frequency, mode, PTT, etc.)

computer-rig-interface
Block Diagram of Computer/Transceiver Interface

Older rigs typically need extra hardware to interface the computer to the rig. These can be custom built (hey, hams build stuff, right?), or be a commercially available box.

SignaLink
SignaLink from Tigertronics.com is a good choice.

More modern transceivers have a digital connection built in and can connect directly to your computer via a standard USB cable for both the audio and control connections.

Current State of Digital Modes

Digital modes seem to come and go. In my opinion, at the beginning of 2018, there seems it seems to be down to 3 or 4 dominate modes, at least on the HF bands. (In my opinion…)

  • RTTY – the granddaddy of them all, now done digitally. Widely used for contesting as well as general chat type contacts.
  • PSK31 – this has been and continues to be a popular chat type contacts. The software ususally supports a more or less standard sequence of starting messages (QTH, Name, rig, etc.), and then allows hand typed chat.
  • FT8 – FT8 is a very new mode (first released in mid-2017) that seems to have totally eclipsed other modes such as JT-65 almost overnight. It uses a fixed 15second message exchange protocol, and can pack a whole bunch of different signals into the standard bandwidth of a USB (upper sideband) signal. The message protocol is fixed and automated. Simply clicking on a CQ message can result it a complete contact in a couple of minutes – no additional operator input needed. In addition, FT8 can make contacts for very weak signals, and does not require high transmitter power.
  • Olivia – Olivia also has its proponents. It is like a high performance, weak signal version of PSK31. Unlike FT8, it does not have a fixed message protocol, and allows chatting or even rag chewing. Olivia does not have as many supporting apps as the other digital modes.

There is an interesting article on the ARRL website about the impact of digital modes.

New Digital Modes Changing Complexion of Bands and Perhaps of Ham Radio

At least some of the other digital modes should continue to see some use as they are more optimized for different kinds of communication (moonbounce, scatter, etc.)

There are other articles on this WA7EWC site with more detail on digital mode software.