Which mode? Characteristic Signalling Occupied bandwidth Channel slow fading tolerance Channel fast fading tolerance  Doppler shift Doppler distortion High sensitivity (dBr) Enhancements Robustness (error correction) Sequence length Special note Standardised use
FST4 Low frequency optimized mode with superior sensitivity for weak signal MF/LF bands. 4-tone Gaussian frequency shift keying (4-GFSK) with very narrow spacing. Varies by submode, from 67.7 Hz (15s) down to 0.36 Hz (1800s). Excellent. Designed for very slow, predictable fading on LF and MF. Poor. Narrow bandwidth makes it sensitive to rapid phase or frequency changes. Very low tolerance. Requires high frequency stability at transmitter and receiver. Sensitive to Doppler spreading; spread must be less than tone spacing. -21 Multi-symbol block detection and optional a priori (AP) decoding assistance. Robust 77-bit payload with LDPC forward error correction and 24-bit CRC. 15, 30, 60, 120, 300, 900, or 1800 seconds. Approaches theoretical limits for information throughput on LF and MF bands. Primary choice for 2200m and 630m band terrestrial communication.
FT4 Fast contesting mode designed for high throughput and quick signal exchanges. 4-tone continuous-phase frequency shift keying (4-CPFSK) with Gaussian shaping. 75 Hz. Uses Gaussian frequency shift keyed waveform for spectral efficiency. Better than FT8. Larger tone spacing provides improved performance during fading. Moderate. Employs FEC to overcome data loss within individual message words. Moderate tolerance. Synchronizes at start, middle, and end of sequences. Low tolerance for in-channel Doppler distortion compared to slower modes. -17.5 Optional a priori computation to predict information, improving threshold by 3dB. Robust LDPC forward error correction on a 77-bit message payload. 7.5 seconds, allowing for very rapid completion of basic QSOs. Time synchronized mode, twice as fast as the popular FT8 protocol. Primarily used for HF radio contesting and high-activity band conditions.
FT8 Most popular mode for general weak-signal DXing and multi-decode operation. 8-tone continuous-phase frequency shift keying (8-CPFSK) with Gaussian shaping. 50 Hz. Uses Gaussian frequency shift keyed waveform for spectral efficiency. Poor. Partial decodes often occur as signals fade during the sequence. Moderate. Employs FEC to overcome data loss within individual message words. Some tolerance of Doppler shift through synchronization at multiple points. Low tolerance for significant in-channel Doppler distortion or fast spreading. -21 Multi-pass decoding and optional a priori (AP) decoding for 3dB gain. Robust LDPC forward error correction on a 77-bit message payload. 15 seconds, providing a balance between speed and decoding sensitivity. Time synchronized mode; revolutionized HF weak-signal operating since its release. General HF DXing, 6m sporadic E, and wideband activity monitoring.
JT4 Legacy mode optimized for EME on microwave bands with high Doppler. 4-tone frequency shift keying (4-FSK) with various selectable tone spacings. Varies by submode A-G, ranging from 17.4 Hz to 312.5 Hz. Good. Designed for the relatively slow variations of the EME path. Moderate. Robust against the fading characteristics of microwave EME signals. High tolerance in wider submodes; includes automatic Doppler tracking features. Tolerant of Doppler distortion in microwave bands using wider submodes. -23 Automatic Doppler tracking and averaging over multiple receive sequences. Convolutional forward error correction with 72-bit message source encoding. 60 seconds, maintaining the classic WSJT-X standard timing sequence. Highly effective for EME on microwave bands up to 24 GHz. Microwave EME (10 GHz, 24 GHz) and terrestrial microwave weak-signal.
JT9 Narrowband mode optimized for MF/HF with higher sensitivity than JT65. 9-tone frequency shift keying (9-FSK) with eight data tones and sync. 15.6 Hz for standard 60s mode; narrower for longer sequences. Excellent. Very narrowband nature is well-suited for stable HF paths. Low. Fast fading or phase jitter can easily disrupt the narrow tones. Very low tolerance. Requires stability better than 1 Hz during transmission. Sensitive to Doppler distortion; requires very stable propagation and oscillators. -27 Averaging of multiple sequences and deepest decoding settings available. Strong convolutional code with constraint length K=32 and 72-bit payload. 1, 2, 5, 10, or 30 minutes; longer sequences improve sensitivity. Uses less than 10% of the bandwidth of the older JT65. LF, MF, and HF weak-signal DXing; occasionally used for EME.
JT65 High sensitivity legacy mode for EME and general HF QRP operation. 65-tone multiple frequency shift keying (MFSK) with sync and data tones. 177 Hz. Wide spacing compared to JT9 for better fading tolerance. Good. Designed to handle the slow variations of the EME channel. Low. Fading within the 60s sequence can prevent successful decoding. Low to moderate. Some tolerance for drift, but EME requires tracking. Moderate. Larger tone spacing than JT9 provides better tolerance of distortion. -25 Multi-decode capability and sophisticated Reed-Solomon error correction. Robust (63, 12) Reed-Solomon code over a 72-bit message payload. 60 seconds, which was the long-time standard for weak-signal digital. Historically the primary mode for EME before the introduction of Q65. VHF/UHF EME and worldwide QRP communication on the HF bands.
Q65 Modern 65-tone mode optimized for EME and fast-fading scatter paths. 65-tone frequency shift keying (65-FSK) with a dedicated synchronization tone. Varies widely by submode A-E and sequence length selection. Excellent. Handles slow fading well using advanced synchronization and averaging. High. Specifically designed to tolerate Rayleigh fading from libration or scatter. Excellent tolerance. Synchronization tone at the start of every message word. Highly tolerant of Doppler distortion and spreading in-channel (e.g., 10GHz EME). -27 A priori decoding assistance and automatic averaging of successive transmissions. 77-bit payload with robust forward error correction and high sync reliability. 15, 30, 60, 120, or 300 seconds; selectable for path requirements. Successor to JT65 for EME, offering significantly improved performance and flexibility. EME (VHF to Microwave), Troposcatter, Rain Scatter, and TEP paths.
Q65-15A Fast Q65 variant for terrestrial use with moderate sensitivity and bandwidth. 65-FSK with 0.15s symbols and 6.67 Hz tone spacing. 433 Hz. Provides a balance between speed and occupied channel space. Moderate. Best for relatively stable terrestrial paths with shorter duration openings. Moderate. Fast enough to catch short pings or brief signal enhancements. Moderate. Synchronization tone handles shifts typical of VHF/UHF terrestrial paths. Tolerant of typical terrestrial Doppler distortion but less than wider submodes. -22.2 A priori (AP) decoding assistance gives approximately 1.5 dB improvement. Robust 77-bit payload with LDPC forward error correction and CRC. 15 seconds, matching the sequence length of the popular FT8 mode. Optimized for quick terrestrial contacts on 6m and 2m bands. VHF/UHF terrestrial weak-signal, sporadic E, and tropospheric propagation.
Q65-15C Fast, wider-spaced Q65 submode for channels with significant Doppler spreading. 65-FSK with 0.15s symbols and 26.67 Hz tone spacing. 1733 Hz. High bandwidth allows for operation on unstable paths. Moderate. Wider spacing improves decode probability during deep signal fades. Good. Wide tone spacing resists errors from rapid channel variations. Very high tolerance. Designed for paths with rapid and significant frequency shifts. High tolerance for significant Doppler spreading, ideal for rain scatter. -22.2 A priori decoding assistance and multi-pass message recovery features. Robust 77-bit payload with LDPC forward error correction and CRC. 15 seconds, prioritizing speed for fleeting propagation openings. Occupies much of the audio passband, centered at 700 Hz. Rain scatter and other propagation with wide Doppler spreading.
Q65-30B Medium length Q65 submode optimized for EME paths with propagation delay. 65-FSK with 0.30s symbols and 6.67 Hz tone spacing. 433 Hz. Standardized for many VHF EME and terrestrial activities. Excellent. 30s sequence provides more integration time than 15s modes. High. Handles Rayleigh fading well with robust symbol synchronization. Good. Designed for paths where Doppler shift is predictable or tracked. High tolerance for moderate Doppler spreading typical of VHF EME. -24.8 A priori (AP) decoding assistance and automatic signal averaging features. Robust 77-bit payload with LDPC forward error correction and CRC. 30 seconds, providing a good trade-off between sensitivity and speed. Frequently used as the default for 6m EME and troposcatter. EME on 50 MHz and high-performance terrestrial scatter communication.
Q65-60B Standard EME submode for lower VHF/UHF bands with high sensitivity. 65-FSK with 0.60s symbols and 3.33 Hz tone spacing. 217 Hz. Optimized for EME paths where Doppler spreading is limited. Excellent. Handles slow EME signal variations and libration fading very effectively. High. Designed for the Rayleigh fading characteristics of the EME path. Good. Includes synchronisation tone to handle Doppler shift from Earth-Moon motion. High tolerance for Doppler distortion and moderate spreading in-channel. -27.6 Integrated a priori (AP) decoding for better performance on marginal signals. Robust forward error correction optimized for the 60-second transmission period. 60 seconds, providing high sensitivity while maintaining a reasonable QSO rate. Highly recommended for EME on 144 MHz and 432 MHz. Earth-Moon-Earth (EME) on 2m and 70cm amateur bands.
Q65-60C High sensitivity submode for EME on 1296 MHz and higher bands. 65-FSK with 0.60s symbols and 6.67 Hz tone spacing. 433 Hz. Wider spacing than 60B to handle increased microwave Doppler. Excellent. 60s integration time is ideal for extremely weak EME echoes. High. Robust against fast fading and phase jitter on microwave paths. Good. Built-in synchronization tone handles significant Doppler shifts from lunar motion. Very high tolerance for Doppler spreading found at 1.3 GHz and above. -27.6 Full support for a priori (AP) decoding and automatic averaging. Robust forward error correction with 77-bit payload and high sync reliability. 60 seconds, the standard duration for microwave EME operations. Standard choice for 1296 MHz EME due to its fading tolerance. EME on 23cm (1296 MHz) and other microwave bands.
Q65-120D Ultra-sensitive long-sequence mode for small-dish EME on microwave bands. 65-FSK with 1.33s symbols and 6.00 Hz tone spacing. 390 Hz. Narrow bandwidth and long integration for maximum sensitivity. Outstanding. 2-minute sequence allows decoding of exceptionally weak, steady signals. High. Large symbols are very robust against rapid phase variations. Moderate. Requires stable oscillators and accurate Doppler tracking at these lengths. High tolerance for Doppler spreading on microwave bands (e.g. 10 GHz). -30.8 Extensive use of a priori (AP) decoding and averaging over multiple transmissions. Highest level of robustness with long integration and forward error correction. 120 seconds (2 minutes), trading speed for extreme weak-signal performance. Enables EME contacts with very small antennas and low power. Microwave EME on 10 GHz and higher where sensitivity is paramount.
MSK144 Very fast mode designed for fleeting meteor scatter path pings. 2000 baud Minimum Shift Keying (MSK) for high-speed data bursts. 2400 Hz. Uses the full bandwidth of a standard SSB transceiver. N/A. Designed for "pings" lasting only a few milliseconds to seconds. Excellent. Rapid frame repetition overcomes fast signal loss and fading. Moderate. Handles frequency shifts up to several hundred Hz for scatter. High tolerance. Fast symbol rate and short frames resist channel distortion. -8 Repetitive frame transmission and coherent demodulation for optimal burst recovery. Robust (128, 80) LDPC forward error correction on 72-bit message frames. 15 second T/R sequences; individual message frames are only 72ms. Sends identical frames repeatedly to capture brief meteor trail reflections. Primary mode for Meteor Scatter and also used for Aircraft Scatter.
WSPR Beacon-style mode for probing propagation paths with extremely low power. 4-tone frequency shift keying (4-FSK) with very narrow tone spacing. 6 Hz. Extremely narrowband to allow many stations in 200Hz slots. Excellent. Designed to monitor long-term propagation trends and slow fading. Poor. Any rapid signal variation will prevent the narrow-band decode. Very low tolerance. Requires precise frequency stability over the 2-minute sequence. Extremely sensitive to any Doppler distortion or frequency spreading. -31 Extensive PSK Reporter integration for global propagation mapping and analysis. Convolutional forward error correction on a 50-bit WSPR-specific payload. 120 seconds (2 minutes) per transmission, synchronized to even minutes. Non-interactive mode; transmits callsign, grid, and power level in dBm. Global propagation reporting, antenna testing, and low-power beaconing.
FST4W Enhanced beacon mode for LF/MF, improving upon WSPR sensitivity. 4-tone Gaussian frequency shift keying (4-GFSK) for better spectral efficiency. Varies by sequence length, typically narrower than equivalent WSPR modes. Excellent. Optimized for the stable, low-noise environment of LF/MF bands. Poor. Narrow tones are susceptible to rapid phase or frequency jitter. Very low tolerance. Requires high stability transmitters for very long sequences. Very sensitive to Doppler; optimized for the minimal spreads of LF/MF. -45 Approaches the theoretical limit for information throughput on low frequencies. Robust 50-bit payload with LDPC forward error correction and 24-bit CRC. 120, 300, 900, or 1800 seconds; longer periods provide extreme sensitivity. Direct replacement for WSPR on LF and MF bands with better performance. Weak-signal propagation reporting on the 2200m and 630m bands.
Echo Specialized tool for detecting and measuring your own moon echoes. Single unmodulated tone transmitted for measurement and calibration. Narrowband pulse detection within the receiver's audio passband. N/A. Used for measuring path loss rather than communicating information. N/A. Designed to integrate signal power over the full Doppler spread. N/A. Compensates for computed EME Doppler shift to center the echo. N/A. Measures Doppler spreading caused by the lunar surface reflections. -15 State-of-the-art planetary ephemeris for precise Doppler and timing predictions. No data payload; relies on spectral integration and averaging for measurement. 6 seconds (2.3s pulse, 0.2s delay, 2.3s receive, 1.2s processing). Essential for verifying EME station performance and measuring lunar path loss. Earth-Moon-Earth (EME) station testing and lunar path characterization.