IFKP
A newer keyboard text mode from the fldigi family, related to FSQ (and, more distantly, DominoEX).
What does it sound like?
A gentle, stepping sequence of tones.
12-second example. A clean example made with the free fldigi program; signals on the air usually sound noisier.
Who uses it?
Amateur radio experimenters.
Where and when can I hear it?
Various ham frequencies; rarely heard.
The science
IFKP uses 33 possible tones, and the information is carried by the step from one tone to the next (32 possible differences) rather than by the tone itself, with a small offset added each time so the same tone does not repeat. Its Varicode alphabet puts all lowercase letters and a few common symbols into a single tone step and everything else into two. fldigi offers three speeds, about 1.8, 3.65 and 5.3 steps per second, all about 386 Hz wide.
Why use it?
Like other incremental-keying modes, carrying data in tone differences makes IFKP tolerant of tuning error, and packing each lowercase letter into one slow symbol gives useful typing speed from a very slow, sensitive signal, with fldigi rating it around -14 to -17 dB signal-to-noise. Unlike FSQ, it uses no special protocol, so it behaves like an ordinary keyboard chat mode, and it can also send small images.
Lore
IFKP's alphabet was tuned to how hams actually type: fldigi notes that amateur text uses Q, X and Z far more than ordinary English because of Q-codes and callsigns. Its decoder also builds a "heard" list automatically whenever it sees a station identify itself.
Easily confused with
- Olivia, from the same family
- Contestia, from the same family
- MFSK (MFSK16/32), from the same family