What is the bandwidth of a 4,800-Hz frequency shift, 9,600-baud ASCII FM transmission?
Why For FSK the pool uses the approximation bandwidth = baud rate + (1.2 x frequency shift). Here that is 9,600 + (1.2 x 4,800) = 9,600 + 5,760 = 15,360 Hz, or 15.36 kHz. The shift term accounts for the spread between the mark and space frequencies, while the baud term accounts for the sidebands created by how fast the signal keys.
Watch out The choice of 5.76 kHz is just the 1.2 x shift portion and the choice of 9.6 kHz is just the baud rate; both leave out half the formula, and 4.8 kHz is simply the shift itself.
Bandwidth = baud + 1.2 x shift. Both terms, always. 9600 + 5760 = 15.36 kHz.