FSK441 was designed for meteor scatter. Where rocks burning through the atmosphere can be few and far inbetween at times.
FSK441 (or even a better description would be AFSK441) uses four-tone frequency shift keying at 441 baud. The frequencies of the audio tones are 882, 1323, 1764, and 2205 Hz. Each encoded character uses three tone intervals and therefore requires 3/441 seconds (approximately 2.3 ms) for transmission.
Detection bandwidth is around 1750hz wide.
The Lowest S/N would be around 1 DB due to the bandwidth and speed
In my experience FSK441 does very well for MS , It is designed to keep on sending the data out to hopefully have a chance to bounce off of a good rock coming through the atmosphere. The lower signal to noise ratio are not as important in situations like these to make the QSO Since you are looking for higher speeds to hopefully get the entire message thru on a short ping opportunities.
+ Good for Meteor scatter due to the speeds and repetitions
- can not ragchew in this mode in a traditional way
+used alot during meteor storms
-not used very much on HF bands
-learning the sequence of a QSO has a learning curve
Mode Audio Sample
FFT Window Screenshot