Palomar Amateur Radio Club STEM Experimentation Lab

FT8 (Franke-Taylor design, 8-FSK)

FT8 is a digital protocol designed for making reliable contacts under weak-signal conditions. Franke-Taylor design, 8-FSK modulation, or FT8, is a radio protocol that is used to send short digital messages using low-power transmissions that can be received at distant stations. An FT-8 transmission operates on a 15 second cycle. This requires accurate time synchronization. The messages are limited to 77 bits which is just enough for 13 characters. It makes for a rapid means of getting QSOs. A typical QSO can be completed in 90 seconds or less. Since its introduction in 2017, it has become one of the most popular digital modes in amateur radio.

FT4 (Fast 4-FSK)

FT4 was developed specifically to facilitate high-speed contesting. While it uses the same weak-signal philosophy as FT8, it features a 6-second T/R cycle, making it 2.5 times faster than FT8 operating on a 7.5-second sequence. This increased speed allows for a higher QSO rate, making it ideal when competition conditions require quick exchanges. FT4 is more robust in some pile-up situations but is generally used when band conditions are slightly better than those required for the ultra-weak signal capabilities of FT8.

Digital modes like FT4 and FT8 use a structured, automated format to ensure high reliability. A standard contact typically includes:

• Station callsigns: - the unique identifiers of both stations.
• Grid Squares: The Maidenhead locator representing the station's geographic position
• Signal Reports: Usually a signal-to-noise ratio (dB) report (e.g., -12dB).
• Acknowledgements: Standard "Roger" or "73" (best regards) messages to conclude the exchange.

Anyone can use FT-8 using the (Free) WSJT-X or JDTX software on their computer connected to a radio or SDR. As well, PARC's OpenWebRX+ servers can decode both FT-8 and FT-4 transmissions.

References:

• FT8 Operating Guide
    📑 Weak signal HF DXing for technophiles