Calculation of frequency deviation in Frequency Modulation

The audio signal having frequency 500Hz and voltage 2.6V, shows a deviation of 5.2KHz in a Frequency Modulation system. If the audio signal voltage changes to 8.6V, calculate the new deviation obtained.


17.2 KHz
19.6 KHz
25.6 KHz
14.6 KHz

Correct Answer: 17.2 KHz


Deviation in FM is given by Δf= kf * Am
Therefore, kf= Δf/ Am
= 5.2/2.6
= 2
When voltage changes to 8.6V= Am’
New frequency deviation Δf’ = kf * Am’
= 2* 8.6
= 17.2 KHz
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