FT4 / FT8 What's The Difference ?

FT8 and FT4 are two digital modes used in amateur radio communication. While both modes were developed by Joe Taylor (K1JT), they differ in several technical aspects, which we will discuss in this article.

Transmission time: One of the key differences between FT8 and FT4 is their transmission time. FT8 transmissions take about 13 seconds to complete, while FT4 transmissions take only 4.48 seconds. This means that FT4 transmissions are much faster, allowing for more QSOs (contacts) in a shorter period.

Bandwidth: Another significant difference between FT8 and FT4 is their bandwidth. FT8 uses a bandwidth of 50 Hz, while FT4 uses a bandwidth of 90 Hz. This means that FT4 transmissions are wider than FT8 transmissions, requiring more space on the radio spectrum.

Error correction: FT8 and FT4 use different error correction algorithms to ensure that the transmitted data is received accurately. FT8 uses a concatenated Reed-Solomon code with low-density parity-check (LDPC) code, while FT4 uses a Golay complementary code with a cyclic redundancy check (CRC). The FT8 error correction algorithm is more robust and can handle up to 15% of errors, while the FT4 algorithm can only handle up to 5% of errors.

Transmission timing: FT8 and FT4 use different transmission timing schemes. FT8 transmissions are sent in specific time slots, while FT4 uses a continuous transmission scheme. This means that FT8 transmissions are synchronized to a specific time, allowing for more precise communication.

Signal strength: FT4 is designed to be more tolerant to weaker signals than FT8. This is because FT4 uses a faster modulation scheme, which allows for better signal detection in weak-signal conditions.