# Calculation of Modulation index in FM signal

## A 100MHz carrier is frequency modulated by 10 KHz wave. For a frequency deviation of 50 KHz, calculate the modulation index of the FM signal.

**Options:**

a) 100

b) 50

c) 70

d) 90

Correct Answer: b) 50

**Explanation:**

Carrier frequency f_{c}= 100MHz

Modulating frequency f_{m}= 10 KHz

Frequency deviation Δf = 500 KHz

Modulation index of FM signal is given by

m_{f} = Δf/f_{m}

= 500*10^{3}/ 10*10^{3}

= 50

#### Discussion

**RE: Calculation of Modulation index in FM signal -babur (01/19/19)**- i think by mistake anwer given is wrong , actual freq deviatiion is 50 KHz

mod index= freq deviaition / mod freq

freq deviation is 50 KHz, mod freq is 10 KHz

mod index = 50 KHz/ 10 KHz

mod index = 5 ( in my last post i mentioned KHz which is wrong)

**RE: Calculation of Modulation index in FM signal -babur (01/19/19)**- i think answer given is wrong by mistake and fol is probably the right soulution;

freq deviation is given 50 khz,

mod index= freq deviation / mod freq

= 50/10 khz

5 khz is answer **RE: Calculation of Modulation index in FM signal -MUHAMMAD HAMID (01/20/18)**- sir here in statement of MCQ f.d=5khz and calculation the f.d=5khz so this in correct.plz correct this one