Question
How is direct binary FSK modulation generated?
Answer Options
- A) By keying an FM transmitter with a sub-audible tone
- B) By changing an oscillator’s frequency directly with a digital control signal
- C) By using a transceiver’s computer data interface protocol to change frequencies
- D) By reconfiguring the CW keying input to act as a tone generator
Correct Answer: B
Explanation
Frequency-Shift Keying (FSK) is a digital modulation method where the frequency of the carrier is shifted to represent the binary states (mark and space). Direct FSK means this shift happens at the carrier generation stage itself.
Direct binary FSK modulation is generated by changing an oscillator’s frequency directly with a digital control signal. This method ensures the two output frequencies (mark and space) are generated from a single oscillator, making the signal clean and highly stable, a requirement for traditional RTTY and some commercial data systems.
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