// Status=review

_WSJT-X_ is a computer program designed to facilitate basic amateur
radio communication using very weak signals. The first four letters in
the program name stand for “Weak Signal communication by K1JT,” while
the suffix “-X” indicates that _WSJT-X_ started as an extended (and
experimental) branch of the program _WSJT_.

_WSJT-X_ currently offers two protocols or “modes,” JT65 and JT9.
Both are designed for making reliable, confirmed QSOs under extreme
weak-signal conditions. They use nearly identical message structure
and source encoding.  JT65 was designed for EME (“moonbounce”) on the
VHF/UHF bands and has also proven very effective for worldwide QRP
communication on the HF bands.  JT9 is optimized for the LF, MF, and
lower HF bands.  It is about 2 dB more sensitive than JT65
while using less than 10% of the bandwidth. Both modes use one-minute
timed sequences of alternating transmission and reception, so a
minimal QSO takes four to six minutes — two or three transmissions by
each station, one sending in odd UTC minutes and the other even. On
the HF bands, world-wide QSOs are possible with power levels of a few
watts and compromise antennas.

_WSJT-X_ can display a passband as large as 5 kHz and provides
dual-mode reception of both JT65 and JT9 signals. If your receiver can
be configured with at least 4 kHz bandwidth in USB mode, you can set
the dial frequency to one of the standard JT65 frequencies — for
example, 14.076 MHz for the 20-meter band — and display the full JT65
and JT9 sub-bands simultaneously on the waterfall. You can then make
QSOs in both modes using nothing more than mouse clicks.

Plans for future program development call for _WSJT-X_ and _WSJT_ to
merge together. _WSJT-X_ will gradually acquire additional modes
such as JT4 that are now supported in _WSJT_. The entire
WSJT-related effort is an open-source project, released under the 
{gnu_gpl} (GPL). If you have programming or
documentation skills or would like to contribute to the project in
other ways, please make your interests known to the development team.
The project’s source-code repository can be found at {devsvn}, and
most communication among the developers takes place on the email
reflector {devmail}.  User-level questions and answers, and general
communication among users is found on the {wsjt_yahoo_group} email
reflector.