Soft Maximum - best free downloads
rtty

TrueTTY
... communications via a sound card. Supported modes are RTTY (Baudot code), ASCII (7 or 8 bits), PSK31 (BPSK and QPSK), BPSK63, ...

SeaTTY
... charts transmitted on longwave and shortwave bands in RTTY, NAVTEX and HF-FAX (WEFAX) modes. None additional hardware is required - ...

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