Question
Which of the following is characteristic of the FST4 mode?
Answer Options
- A) Four-tone Gaussian frequency shift keying
- B) Variable transmit/receive periods
- C) Seven different tone spacings
- D) All these choices are correct
Correct Answer: D
Explanation
FST4 is a weak-signal digital mode developed by K1JT that is optimized for slow-speed, extremely long-distance, and highly reliable communications, primarily on the LF and MF bands (137 kHz and 475 kHz, or 2200 and 630 meters) and sometimes EME. Its unique characteristics are necessary due to the narrow bandwidth and challenging noise floor of those lower frequencies.
FST4 uses a robust modulation scheme, Four-tone Gaussian frequency shift keying (4-GFSK). It is highly flexible, allowing for variable transmit/receive periods (e.g., 15, 30, 60, 120, 300, 900 seconds), and it can be configured with seven different tone spacings. These features allow operators to optimize the mode for specific band conditions and activity levels, meaning all these choices are correct.
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