Mercury is an open source HF OFDM modulated data mode designed for data communications over amateur radio, specifically file sharing and email forwarding systems. Designed with dynamic parameters to adapt to changing band conditions during the link, and with multiple codecs built in, it is included in the HERMES Software suite and has been developed by Rhizomatica. The Mercury HF modem is compatible with Windows and Linux operating systems and most HF capable transceivers and is compatible with FCC regulations on HF data modes and ID requirements.

The mercury HF modem software currently does not have a user interface, and requires some familiarity with the terminal protocols and editing configuration files manually. The good news is that it is compatible with the VarAC program once installed and configured, and will act like any other modem.