FT8 and FT4

FT8 and FT4 are digital communication modes used in amateur radio for transmitting weak signals and for DX (long distance) communications. They were developed by Joe Taylor (K1JT) and his team to provide reliable communications in difficult conditions. Both modes use special signal processing and error correction techniques to transmit information even with very weak signal levels.

 

FT8 (Franke-Taylor 8)

FT8 stands for 'Franke-Taylor 8', named after its developers Joe Taylor (K1JT) and Steven Franke (K9AN). It was introduced in 2017 and is best known for its ability to decode signals well below the noise floor.

 

Features of the FT8

  1. Short transmission cycles: FT8 uses 15 second transmission cycles. This means that a transmission lasts 15 seconds, followed by a 15-second pause for the receiver to respond.
  2. Weak signal efficiency: FT8 can decode signals up to -24 dB below noise, making it ideal for long distance, weak signal conditions.
  3. Error correction: FT8 uses Forward Error Correction (FEC) to correct transmission errors and ensure that the data received is accurate.
  4. Automated transmissions: The process is highly automated, allowing fast contact sequences and many connections in a short period of time.

 

Typical use
The FT8 is ideal for DX hunting and weak signal conditions on shortwave bands. Radio amateurs often use it to contact distant stations, especially in poor propagation conditions or at low power (QRP).

 

Radio Software
The most commonly used software for FT8 is WSJT-X, which is specifically designed for weak signal modes such as FT8. The software handles the sending and receiving of signals as well as the decoding of the received data.

 

FT4 (Franke-Taylor 4)

FT4 was developed after FT8 and is a further development for competitive conditions. It offers faster transmission cycles and is designed for higher speeds.

 

FT4 features

  1. Even faster transmission cycles:FT4 uses 7.5 second transmission cycles. This is twice as fast as FT8, which is useful for competitions or rapid succession of radio contacts.
  2. Weak signal efficiency:FT4 can decode signals up to -20 dB below noise, which is still very good for weak signals but slightly less sensitive than FT8.
  3. Error correction: Like FT8, FT4 uses error correction methods, but in a form optimised for faster transmissions.
  4. Optimised for competitions:FT4 has been designed to handle fast QSOs during contests or special radio activities.

 

Typical use
FT4 is often used in situations where it is important to process QSOs quickly, such as in contests or during certain radio activities where the aim is to make as many connections as possible in a short period of time.

 

Differences between FT8 and FT4

  • Transmission time: The FT8 has 15-second transmission cycles, while the FT4 uses 7.5-second cycles, making the FT4 twice as fast.
  • Sensitivity: FT8 is more sensitive to weak signals (-24 dB) while FT4 can decode up to -20 dB below noise level.
  • Application: FT8 is better for weak signals and DXing, while FT4 is optimised for fast QSOs and contests.

 

Similarities between FT8 and FT4

  • Both modes use frequency shift keying (FSK) and error correction to provide reliable communication in weak signal conditions.
  • They are highly automated, allowing efficient communication without manual intervention.
  • Both are implemented in the WSJT-X software and are widely used in amateur radio.

 

Conclusion
FT8 and FT4 are modern digital communication modes that enable radio amateurs to make reliable radio contacts even in difficult conditions and with weak signals. FT8 is particularly useful for DX hunting in difficult conditions, while FT4 is ideal for fast connections in contests or special activities.