Hi, welcome to Digital Communication, a brief tutorial on digital modes found on the HF bands. This tutorial is spread out over a number of separate articles (or posts and bloggers would say).  Please explore them all.

In this article: Background, Equipment and Resources:


Over the past few years there has been a huge upswing in using digital modes on the High Frequency (HF) bands. This is due to the use of a computers sound card to create the digital encoding rather than the need for a dedicated external modem. This reduced the price to enter the HF digital world from $100 and up to practically nothing. (If you home-brew and have a pretty well stocked junk box).

Digital HF modems are still available, such as the TimeWave PK-232, but most have been replaced by software and your computers sound-card.

The sound-card digital era began with a new mode called PSK31 and has been booming ever since. It seems that a new mode or sub-mode is invented almost every month. Each has its advantages and disadvantages. Many are designed for a particular form of communication such as moon bounce. Regardless all are fun and can be enjoyed with a minimal investment.

Even the original digital mode1  RadioTeletype (RTTY) has had a resurgence. When PSK31 started to get popular the demise of RTTY was predicted. Well quite the opposite happened. RTTY moved from modem based into the realm of the sound-card and enjoys greater popularity than it ever did.


Here’s a list of what you need to get started on the HF digital modes:

  • A computer:
    • almost any computer will work. Anything from an old laptop to a modern multiprocessor beast will handle the new digital modes.
    • Sound-card. Most built in sound-cards will be acceptable.
    • RS-232 port. if not available then a USB port with a USB to Serial adapter will work just fine.
      • The RS-232 is used to ‘key’ the radio… switch it from receive to transmit.
      • Most commercial interfaces now can connect directly to a USB port, see the section below on interfaces.
  • Interface:
    • There needs to be hardware to connect the computer to the radio.
    • There are usually three interfce connections:
      1. Audio from the radio to the computer.
      2. Audio from the computer to the radio.
      3. PTT to key the radio.
    • You can build an interface or purchase one already to go. Your Elmer’s preference is to build and complete plans are included in the section on interfaces.
  • Software:
    • The final, and most important piece, of the puzzle is the software. They range from software designed for a single mode such s JT-65 to capable of operating dozens of modes. Most are free to download and use.
    • Details on some of the more popular packages will be covered in the Software section.


A simple internet search for digital modes will fill pages of your browser. Here are a few that you may find interesting:

Note 1: Actually CW was the first digital mode after all it is only on or off.