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Weak Signal Communication Software

WSJT-X implements communication protocols or "modes" called FST4, FST4W, FT4, FT8, JT4, JT9, JT65, MSK144, Q65, WSPR, and Echo. The first nine of these modes were designed for making reliable, confirmed QSOs using weak signals in a wide variety of propagation circumstances. WSPR is for probing potential propagation paths with low-power transmissions, and Echo mode is for detecting and measuring reflections of your own signals from the Moon.

JT4, JT9, and JT65 use nearly identical message structure and efficient compression of standard messages used in minimal QSOs. They use timed 60-second Transmit/Receive sequences synchronized with UTC. JT4 and JT65 were designed for EME ("moonbounce") on the VHF, UHF, and microwave bands. JT9 is optimized for the MF and HF bands. It is about 2 dB more sensitive than JT65 while using less than 10% of the bandwidth.

FT4 and FT8 are operationally similar but use T/R cycles only 7.5 and 15 s long, respectively. They have become extremely popular for world-wide DXing on the HF bands. MSK144 is designed for Meteor Scatter on the VHF bands. Q65 offers submodes with a range of T/R sequence lengths and tone spacings; it is highly recommended for EME, ionospheric scatter, and other weak signal work on VHF, UHF, and microwave bands. These modes offer enhanced message formats with support for nonstandard callsigns and popular contests.

FST4 and FST4W are designed particularly for the LF and MF bands. On these bands their fundamental sensitivities are better than other WSJT-X modes with the same sequence lengths, approaching the theoretical limits for their rates of information throughput. FST4 is optimized for two-way QSOs, while FST4W is for quasi-beacon transmissions of WSPR-style messages. FST4 and FST4W do not require the strict, independent time synchronization and phase locking of modes like EbNaut.

MAP65 implements a wideband receiver for JT65 and Q65 signals, optimized for EME on the VHF/UHF bands. It can be used together with Linrad (by SM5BSZ) or with direct input from a soundcard, FUNcube Dongle, or similar hardware. The program decodes all JT65 or Q65 signals in a passband up to 90 kHz wide, producing a sorted band map of decoded callsigns. In a dual-polarization system, MAP65 optimally matches the linear polarization angle of each signal, thereby eliminating problems with Faraday rotation and spatial polarization offsets.

QMAP is similar to MAP65 in providing wideband reception of signals over a full EME sub-band. It works cooperatively with WSJT-X, supporting the Q65 mode in both 30-second and 60-second submodes. The QMAP + WSJT-X combination provides full rig control and Earth-Moon-Earth Doppler compensation.