The mode that works below hearing, and what it cost
2026-04-08 · EA5IYR
In June 2017, Joe Taylor — a Nobel laureate in physics who happens to be a radio amateur — released a digital mode called FT8.
Within two years it was the most reported mode on the amateur bands. Not one of the most common. The most common. What it actually does
FT8 decodes signals at about −20 dB signal-to-noise in a 2.5 kHz bandwidth. In plain terms: it reliably reads transmissions that a human operator cannot hear at all, on a band that sounds empty.
It does that by knowing exactly what to expect. Transmissions are locked to 15-second slots on the wall clock, use a fixed message format, and carry heavy error correction. The receiver is not listening for speech in noise; it is testing a small number of possibilities against a rigid template.
That is why it works with a wire antenna and a few watts on a dead band. And what it costs
A complete contact is four slots — about a minute — and carries roughly thirteen characters: a callsign, a grid square, a signal report, an acknowledgement.
There is no room for a name. No weather, no rig, no how-are-you. The operator's job is to click on a decoded line and wait.
This is the whole argument, and both halves of it are true. It works when nothing else will, and it works by removing everything a contact used to be. Where it leaves the bands
Walk up 20 metres on a quiet afternoon and the voice segments can be empty while the FT8 frequency is packed. For some that is a band being used efficiently. For others it is a band whose conversation has moved into a piece of software.
The strongest version of the objection is not nostalgia. It is that a mode which needs no operator skill, no ear, and no ability to hold a conversation under fading has quietly become the thing most licence holders spend their time doing — and the skills it replaced are not being learned by anyone else.
The strongest version of the defence is equally hard to dismiss: FT8 has put people on the air from flats with an indoor antenna and a solar minimum, who would otherwise have heard nothing and given up. If you want to try it
You need WSJT-X, a computer connected to the radio's audio, and — this catches everybody — a clock accurate to within a second or two, because the slots are absolute. Then park on the FT8 frequency for the band and watch a screen full of decodes appear out of what sounds like nothing at all.
Whatever you conclude about it, that first moment is worth having. A band you would have sworn was dead turns out to be busy.
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Sources: Wikipedia — FT8, WSJT-X user guide, ARRL — weak signal modes, Signal Identification Wiki — FT8.