Question
What type of modulation is used by FT8?
Answer Options
- A) 8-tone frequency shift keying
- B) Vestigial sideband
- C) Amplitude compressed AM
- D) 8-bit direct sequence spread spectrum
Correct Answer: A
Explanation
FT8 is one of the most popular digital modes for weak-signal and long-distance HF communication. It is part of the family of Frequency Shift Keying (FSK) modes, which encode data by shifting the carrier frequency.
FT8 specifically uses 8-tone frequency shift keying (MFSK, where M=8). This means that at any given moment, the signal is transmitted on one of eight possible carrier frequencies, which are closely spaced and shift rapidly. The use of multiple tones, rather than just two (binary FSK), allows the mode to carry more information per transmission cycle.
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