Joe says, on wsprnet.org
"If you are on 160 meters, or perhaps on 472 or 137 kHz, you may be interested in a new mode called JT9, designed especially for making QSOs on these bands. JT9 uses the structured messages introduced in 2003 for the JT65 mode, now widely used for EME and for QRP operations at HF. JT9 can operate at signal levels as low as -27 dB (in a 2500 Hz reference bandwidth), with one-minute timed transmissions. It also offers slower transmissions of 2, 5, 10 and 30 minutes duration, and the slowest mode can decode signals as weak as -40 dB. With one-minute transmissions, submode JT9-1 has a total bandwidth of 15.6 Hz -- less than one-tenth the bandwidth of a JT65A signal. The other submodes are narrower still: a JT9-30 signal occupies about 0.4 Hz total bandwidth.
and an early version of WSJT-X can be downloaded from