Creators : Con Wassilieff ZL2AFP and Murray Greenman ZL1BPU in 2004
Baud rate : 10.766
Speed : 40 wpm (by deleting the synchronization characters)
Modulation : IFK (Incremental Frequency Keying) 16 tones but with two tone sets (J1 and J2) in alternance so as to reduce the ISI (InterSymbol Interference) and to allow a quick synchronization.
The total number of tones being 16 separated by a frequency offset (FO) equal to the baud rate, each set has 8 interleaved tones separated by 2 DF:
O O ...J1
O O ...J2
Note : in fact, 18 tones (2 x 9) are used to limit the rotations.
A character is composed of 2 symbols of 3 bits each, each symbol being sent on a tone set (first symbol on J1 then second symbol on J2).
Reception mode : sensible to the side (USB or LSB), USB is recommended
Character set : 62 characters (lower case, numbers and some punctuation) + an error reset character (6 bits long characters) + a synchronization character
Shape of pulse : rectangular
Space between tones : 10.766 Hz
Bandwidth : 213 Hz,
Demodulation : non-coherent,
Synchronization : for the 3 bits symbols, using the signal. For the symbol order, thanks to a block of 4 synchronization characters sent after 12 characters standard.
Convolution code : no
Interleaving : no
Offset tolerance : 65 Hz. This is the big advantage of this IFK mode which can accomodate a mistuning inferior or equal to +/- 65 Hz.
Drift tolerance : 20 Hz/mn (depending on signal the signal-to-noise ratio)
Note : inside the band limited by the offset tolerance, the drift tolerance is superior to 200 Hz/mn
Pmean/Ppeak : 1
Lowest S/N : -12 dB.
Just another scheme to keep bandwidth down.
And speed up for given bandwidth