Question

A 107.6 MHz carrier signal is frequency modulated by a 7kHz sine wave . The resultant FM signal has a frequency deviation of 50 kHz. Determine the modulation index and the carrier swing of the FM wave
A. 7.143 and 100 kHz
B. 8.234 and 75 kHz
C. 6.289 and 150 kHz
D. 5.103 and 14 kHz

Answer 1

Correct Answer - A
Given `, f_(c)=107.6 MHz , f_(m)=7kHz and Deltaf=50kHz `
The modulation index of the FM wave canbe given as
` m_(f)=("Frequency deviation ")/("Modulating frequency ")`
`=(Deltaf)/( f_(m))=( 50 xx 10^(3))/( 7 xx 10^(3))=7.143`
Carrier swing ` = 2 xx Deltaf = 2 xx Delta f `
` = 2 xx 50 xx 10^(3) =100 kHz `