Question

1. Assuming that an oscilloscope displays a V_max of 5.22V and V_min of 1.33V. Calculate the percentage of modulation. (5 points)
2. Three (3) AM broadcast stations are spaced at 18 kHz, beginning at 73 kHz. Each station is allowed to transmit modulating up to 6 kHz. Compute for the upper and lower sidebands of each station and plot it in the frequency domain. (15 points)
3. Given a V_max of 7.45V and a modulation index of 0.691, calculate for V_min. (5 points)
4. A station is given a carrier frequency of 88 kHz. Having a modulating frequency of 12 kHz, compute for the upper and lower sidebands of the station. (5 points)

Answer 1

1)

$m=\frac{V_{max}-V_{min}}{V_{max}+V_{min}}=0.594.$

2)

$f_{min}=73-6=67~kHz,$

$f_{max}=73+18+18+6=115~kHz.$

3)

$m=\frac{V_{max}-V_{min}}{V_{max}+V_{min}},\implies$

$V_{min}=\frac{1-m}{1+m}V_{max}=1.36~V.$

4)

$f_{min}=88-12=76~kHz,$

$f_{max}=88+12=100~kHz.$