# Frequency Modulation with same carrier and message signal of same frequency but different amplitude

How is frequency deviation calculated for a FM wave? Suppose we have a same carrier and a sinusoidal message signal of frequency 5Hz and maximum amplitude of 5V and another sinusoidal message signal of frequency 5Hz but amplitude of 10V will frequency deviation be different or same in both case?

Frequency deviation is proportional to the amplitude of the modulating signal. So the deviation produced by your 10 V signal will be twice that produced by the 5 V signal.

does that mean maximum frequency deviation of a carrier is proportional to the maximum value of amplitude of message signals the carrier can carry whatever maybe the frequency of message signals?

A practical system will have a maximum permitted frequency deviation and a maximum permitted frequency for the modulating (message) signal. Within those limits then yes.

• does that mean maximum frequency deviation of a carrier is proportional to the maximum value of amplitude of message signals the carrier can carry whatever maybe the frequency of message signals? Commented Nov 20, 2020 at 12:07