Digital Communication (An Introduction)
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Digital HF modems are still available, such as the TimeWave PK-232, but most have been replaced by software and your computers sound-card.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.
- There needs to be hardware to connect the computer to the radio.
- There are usually three interfce connections:
- Audio from the radio to the computer.
- Audio from the computer to the radio.
- 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.
- 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:
- KB9UKD Digital Modes Samples: an unbelievable list of digital modes, a brief description of each, links to more information and a short sound file so you can hear what the mode sounds like.
- WB8NUT’s web pages on Digital Modes: A little deeper explanation of popular digital modes. There is a good review of Digital mode software on and adjacent page (http://wb8nut.com/software/)
- G4UCJ’s page on digital modes: includes waterfall traces of each mode and some good Elmer information on some of the modes. There is a lot of good general ham information on this site too!
- W1HKJ’s Digital Modes – Sight and Sound: A great site that shows what most digital signals look like and sound like.
Note 1: Actually CW was the first digital mode after all it is only on or off.