MT63

It was developed by Pawel Jalocha, call sign SP9VRC, primarily for keyboard-to-keyboard conversations on HF amateur radio bands.

The MT63 mode is very tolerant of mistuning; most software will handle 120 Hz tuning offsets under normal conditions.

The long interleaver makes the mode more robust against interference, at the cost of increasing latency.

MT63 was used on shortwave by the VOA Radiogram until 2017,[1] but the software used to encode the text was not using the Varicode that MT63 used in its original design.

MT63 has been promoted as a modulation format for time signal stations, but this system does not use Varicode.