Getting Started with Digital Modes
Setting Up for Digital Modes
If you're new to digital modes, here's what you need to know to get started.
The Basic Setup
Most digital modes use your computer to generate and decode audio, with your radio handling the RF side:
- Radio — set to USB (upper sideband) on all bands for digital modes (even below 10 MHz where voice uses LSB)
- Sound card interface — connects your computer's audio to the radio. Many modern radios have USB connections that handle audio and CAT control in one cable
- Software — WSJT-X (for FT8/FT4), fldigi (for PSK31, RTTY, etc.), or JS8Call
- Accurate clock — FT8 requires your computer clock to be accurate within ±1 second. Use internet time sync or GPS
Important convention: Digital modes use USB on ALL bands, even on 40m and 80m where voice uses LSB. This is because the software generates precise audio tones, and USB keeps the relationship between audio frequency and RF frequency consistent.
FT8 in Practice
FT8 (Franke-Taylor design, 8-FSK modulation) has become the most popular digital mode. Here's how it works operationally:
- Transmit/receive periods alternate every 15 seconds, synchronised to the clock
- Each message is exactly 77 bits, containing callsigns, grid square, and signal report
- A complete QSO (contact) takes about 75 seconds (5 exchanges)
- You can see dozens of stations simultaneously on the waterfall display
- Power: 20-50W is often plenty — FT8's sensitivity means you don't need a big signal
Common Digital Mode Frequencies
| Band | FT8 | FT4 | PSK31 | RTTY |
|---|---|---|---|---|
| 40m | 7.074 MHz | 7.047 MHz | 7.040 MHz | 7.040 MHz |
| 20m | 14.074 MHz | 14.080 MHz | 14.070 MHz | 14.080 MHz |
| 15m | 21.074 MHz | 21.140 MHz | 21.070 MHz | 21.080 MHz |
| 10m | 28.074 MHz | 28.180 MHz | 28.120 MHz | 28.080 MHz |
| 6m | 50.313 MHz | 50.318 MHz | 50.305 MHz | — |
APRS — Automatic Packet Reporting System
APRS is a real-time tactical communication system using packet radio:
- Transmits your GPS position, weather data, or short messages
- On 145.175 MHz in Australia (VK)
- Stations appear on maps (aprs.fi or similar)
- Useful for tracking during portable operations, SOTA (Summits On The Air), and emergencies
Exam tip: Know that digital modes conventionally use USB on all bands. Also know the basic FT8 timing (15-second periods) and that FT8 can decode at approximately −24 dB SNR — far below what you can hear by ear.