📶 Weak Signal Communication Software

While not limited to HF frequencies, these programs are widely used in the HF bands for weak-signal digital communication and fast logging. They’re ideal for low-power setups, noisy environments, and long-distance contacts under challenging conditions.

🧰 Featured Software

• WSJT-X

The most popular suite for weak-signal modes like FT8, FT4, JT65, and more.

• Platforms: Windows, Linux, macOS

• Requires: SSB transceiver + computer with soundcard or equivalent

• WSJT

The predecessor to WSJT-X, still useful for legacy modes.

• Platforms: Windows, Linux

• MAP65

Designed for EME (Earth-Moon-Earth) and SDR-based reception.

• Platforms: Windows

• Supports: SDR-IQ, Perseus, SoftRock, FUNcube Dongle

• WSPR (Weak Signal Propagation Reporter)

Ideal for beacon-style transmissions and propagation studies.

• Platforms: Windows, Linux

• Supports: SDR hardware and traditional rigs

• SimJT

A utility for generating simulated signals—great for testing and training.

• Platform: Windows only

🆓 Licensing & Availability

All programs are open-source and distributed under the GNU General Public License. Installation packages are available free of charge from their respective project pages. For further details about source code and operating systems, see the Program Development page.

WSJT-X ("Weak Signal Communication, by K1JT") offers specific digital protocols optimized for EME (moon bounce), meteor scatter, and ionospheric scatter on VHF/UHF, as well as for LF, MF, and HF propagation. The program can decode fraction-of-a-second signals reflected from ionized meteor trails and steady signals more than 10 dB below the audible threshold. WSJT-X incorporates nearly all popular capabilities of programs WSJT and WSPR, while adding comprehensive rig control and many other features. Check the WSJT-X page and links therein for details about modes FT8, JT4, JT9, JT65, QRA64, ISCAT, MSK144, and WSPR.  

WSJT is the original program, first released in 2001. Version 10 implements modes JTMS, FSK441, FSK315, ISCAT, JT6M, JT65, and JT4.

MAP65 implements a wideband receiver for JT65 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 or FUNcube Dongle. The program decodes all JT65 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.  

WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter." This program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands. Users with internet access can watch results in real time at WSPRnet.org. Version 2.11 of WSPR includes FMT, a package of command-line utilities that can help you make highly accurate frequency measurements without expensive laboratory equipment. The WSPR mode is now included in program WSJT-X.

SimJT generates JT65 and CW test signals with user-specified signal-to-noise ratio. It is useful for testing the JT65 decoder and the relative capabilities of these two modes.