What is the difference between direct FSK and audio FSK?
Direct FSK modulates the transmitter VFO✓Bonne réponse
Direct FSK occupies less bandwidth
Direct FSK can transmit higher baud rates
All these choices are correct
Explication
Direct FSK shifts the transmitter's own frequency-determining oscillator between mark and space, while audio FSK produces the same two tones at audio and lets an SSB transmitter translate them to RF. The transmitted signal is the same shift either way, so bandwidth and achievable baud rate are not what distinguishes them; direct FSK simply avoids the audio chain and its distortion and level problems.