Spectrogram of MT63-1K Modulation

MT63 is a digital radio modulation mode for transmission in high-noise situations. It was developed by Pawel Jalocha, call sign SP9VRC, primarily for keyboard-to-keyboard conversations on HF amateur radio bands.

Description

MT63 distributes the encoding of each character over a long time period, and over several tones. This code and symbol spreading implementation is key to its robustness under less than ideal conditions. The MT63 mode is very tolerant of mistuning; most software will handle 120 Hz tuning offsets under normal conditions.

Mode Symbol rate Typing speed Duty cycle Modulation Bandwidth ITU designation
MT63-500 5 baud 5.0 cps (50 wpm) 80% 64 × 2-PSK 500 Hz 500HJ2DEN
MT63-1000 10 baud 10.0 cps (100 wpm) 80% 64 × 2-PSK 1000 Hz 1K00J2DEN
MT63-2000 20 baud 20.0 cps (200 wpm) 80% 64 × 2-PSK 2000 Hz 2K00J2DEN

Latency

MT63 can use either a short or long interleaver. The long interleaver makes the mode more robust against interference, at the cost of increasing latency.

Mode ECC mode Latency (sec)
MT63 500 Hzshort12.8
MT63 1Kshort6.4
MT63 1Klong12.8
MT63 2Kshort3.2
MT63 2Klong6.4
PSK31-<1

Media

MT63 is seeing a resurgence in its popularity on shortwave with the VOA Radiogram,[1] but the software used to encode the text is not using the Varicode that MT63 used in its original design.

Modern software that supports MT63, such as Fldigi, uses base128,[2] essentially the same as ASCII.

MT63 has been promoted as a modulation format for time signal stations, but this system does not use Varicode.[3]

See also

References

  1. ↑ "VOA Radiogram".
  2. ↑ "MT63 Modes".
  3. ↑ "Wide Area Time Service with Extended Features".
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