RTTY Receiver
Radioteletype decoding
What it does
SimpleA long time ago, before the internet, people sent typed messages over the radio by switching between two musical notes — one note meant one thing, the other note meant another. Machines called teletypes printed the words onto paper.
This app listens to those two warbling notes and turns them back into typed words on your screen. Ham radio operators still use RTTY today, so you can catch real conversations happening in this vintage mode.
How it works
SimpleOne note stands for 'mark' and the other for 'space'. Groups of five marks-and-spaces make a code for each letter. Because five bits can't cover every letter, number and symbol, there's a special 'shift' code that flips between letters-mode and numbers-mode, like pressing Shift on a keyboard.
How to use it, step by step
Simple- Open the 'RTTY RX' app.
- Find a two-tone warbling signal on the ham bands.
- Let it set the speed automatically.
- Watch the typed words appear.
Examples
Decode an amateur RTTY conversation on the 20 m band, sometimes from far away.
During an RTTY contest, watch rapid-fire exchanges of callsigns and signal reports.
Try different shift settings to see how mistuning garbles the text, then dial it back in.
Tips & things to try
- Getting mark/space the right way round matters — if text is gibberish, try reversing the shift.
- 45.45 baud is the classic amateur speed; start there with auto-baud on.
- RTTY is loud and distinctive on a waterfall — two parallel lines that flicker between tones.