FST4 / FST4W
Weak-signal modes related to FT8 and WSPR, with longer turns for very low frequencies and very weak paths.
ModeFST4 / FST4W
FamilyWeak-signal digital
Audio example12 s
What does it sound like?
Plate 19Weak-signal digital
Slow, faint tones over long turns, similar to WSPR.
0 Hz1,0002,0003,000 Hz
12-second example. A clean example made by our own signal generator; signals on the air usually sound noisier.
Field marks4 tonesPeriods from 15 seconds to 30 minutesBuilt for very weak paths
Who uses it?
Amateur radio operators, especially on the low-frequency bands (136 kHz and 475 kHz).
Where and when can I hear it?
Low and medium frequency ham bands, plus some HF.