FT8 was released in 2017 by Joe Taylor, K1JT, and Steve Franke, K9AN, as part of the WSJT-X suite, and it has reshaped HF digital activity more than any mode before it. If you learned digital modes on PSK31 or RTTY, the structured 15-second exchange windows feel rigid at first — but that rigidity is exactly what makes it work so well at the edge of the noise floor.
How it actually works
FT8 encodes a 75-bit message using a strong low-density parity-check (LDPC) code, then modulates it as an 8-tone (8-FSK) signal across a roughly 50 Hz bandwidth. Transmissions are locked to even or odd 15-second slots referenced to UTC, which is why FT8 absolutely requires your computer clock to be accurate — even a couple seconds of drift will keep you from decoding or being decoded. WSJT-X can pull a valid decode out of signals around -20 dB relative to the noise floor, well below what’s readable by ear.
What this trades away
FT8 isn’t built for conversation. Exchanges are limited to callsigns, grid squares or signal reports, and a handful of fixed messages — there’s no room for ragchewing. That’s a deliberate design choice, not a limitation someone forgot to fix. For things like grid-square hunting, working marginal band openings, or testing antenna performance against a known baseline, that structure is a feature.
It’s not a replacement for ragchewing — it’s a different tool for a different job.
Getting started
WSJT-X is free and runs on Windows, macOS, and Linux. You’ll need a way to get audio between your radio and computer (a USB sound card interface or a radio with a built-in USB codec) and CAT control for automatic frequency/PTT handling. Standard FT8 frequencies on the most active bands: 1.840, 3.573, 7.074, 10.136, 14.074, 18.100, 21.074, 24.915, and 28.074 MHz.