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FT4 is a digital mode developed by Steve Franke (K9AN) and Joe Taylor (K1JT) as a companion to FT8, released in 2019 as part of WSJT-X. Where FT8 was designed primarily for making contacts under difficult propagation, FT4 is optimised for speed — its 7.5-second transmit/receive cycles are twice as fast as FT8, making it better suited for contesting and rapid exchanges when conditions are reasonably good.
FT4 and FT8 share the same underlying philosophy — structured, automated exchanges with strong error correction — but differ in several key parameters:
| Parameter | FT8 | FT4 |
|---|---|---|
| Transmit period | 15 seconds | 7.5 seconds |
| Message duration | 12.64 seconds | 6.32 seconds |
| Modulation | 8-GFSK | 4-GFSK |
| Number of tones | 8 | 4 |
| Bandwidth | ~50 Hz | ~80 Hz |
| Minimum SNR for decode | −24 dB | −17.5 dB |
| Message payload | 77 bits | 77 bits |
The key trade-off is clear: FT4 gains speed at the cost of sensitivity. It requires signals to be about 6.5 dB stronger than FT8 for reliable decoding. In practice, this means FT4 works best when conditions are moderate to good — exactly the conditions where you want to move faster through contacts.
Both modes carry the same 77-bit message payload, so the information in each transmission is identical. The exchange sequence is the same as FT8.
Use FT4 when:
Use FT8 when:
Many operators switch between FT8 and FT4 depending on conditions and activity on each frequency.
FT4 uses the same software and hardware as FT8. In WSJT-X, simply select FT4 from the mode menu. The software handles all the timing and protocol differences automatically.
The same requirements for accurate time synchronisation apply — your clock must be within ±1 second of UTC. Because FT4's periods are shorter, timing errors are proportionally more impactful.
FT4 has its own standard dial frequencies, separate from FT8:
| Band | Dial frequency (MHz) |
|---|---|
| 80m | 3.575 |
| 40m | 7.047.5 |
| 30m | 10.140 |
| 20m | 14.080 |
| 17m | 18.104 |
| 15m | 21.140 |
| 12m | 24.919 |
| 10m | 28.180 |
| 6m | 50.318 |
Note: Some FT4 frequencies vary by region and may shift over time as usage patterns develop. Check current band plans for your region.
FT4 was specifically designed with contesting in mind. The 7.5-second periods allow a complete contact in about 45 seconds — roughly half the time of an FT8 contact. WSJT-X includes contest-specific message types for events like:
Contest mode is enabled through the WSJT-X settings. When active, the software adjusts message formats to include the required contest exchange instead of the standard grid locator.
Monitor both FT4 and FT8 — Some operators run two instances of WSJT-X (one for each mode) when their station setup allows, or switch between them based on where the activity is. During contests that support both modes, activity may be split.
Power and audio levels — The same advice applies as for FT8. Keep your ALC at zero, use only enough power for the conditions, and avoid overdriving.
Wider bandwidth awareness — FT4 signals are about 80 Hz wide (vs 50 Hz for FT8), so the waterfall will look slightly different. Ensure you are not transmitting on top of other signals.