The frequency deviation produced in a VHF carrier by a signal of 100 Hz is 50 kHZ. The frequency modulation index is

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VSSC ISRO Technical Assistant Electronics 8 Feb 2015 Official Paper
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  1. 100 radians
  2. 250 radians
  3. 500 radians
  4. 750 radians

Answer (Detailed Solution Below)

Option 3 : 500 radians
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Detailed Solution

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Concept:

In FM (Frequency Modulation), the modulation index is defined as the ratio of frequency deviation to the modulating frequency.

Mathematically, this is defined as:

mf = Modulation index

Δf = Frequency deviation

fm = Modulating frequency

Calculation:

Given Δf = 50 kHz

fm = 100 Hz

mf = 500 radians

A wave has 3 parameters Amplitude, Phase, and Frequency. Thus there are 3 types of modulation techniques.

Amplitude Modulation: The amplitude of the carrier is varied according to the amplitude of the message signal.

Frequency Modulation: The frequency of the carrier is varied according to the amplitude of the message signal.

Phase Modulation: The Phase of the carrier is varied according to the amplitude of the message signal.

 

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