# Amplitde Modulation MCQ’s

This set of Electronic Devices & Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Amplitde Modulation”.

(Q.1-Q.3) An AM signal is represented by x(t) = (20 + 4sin(500πt)) cos(2πt x 105)V.

1. Total signal power is
a) 208 W
b) 204 W
c) 408 W
d) 416 W

2. Total sideband power is
a) 4 W
b) 8 W
c) 16 W
d) 2 W

3. The modulation index is
a) 20
b) 4
c) 0.2
d) 10

4. An AM broadcast station operates at its maximum allowed total output of 50 kW with 80% modulation. The power in the intelligence part is
a) 12.12 kW
b) 31.12 kW
c) 6.42 kW
d) none of the mentioned

5. A modulating signal is amplified by a 80% efficiency amplifier before being combined with a 20 kW carrier to generate an AM signal. The required DC input power to the amplifier, for the system to operate at 100% modulation, would be
a) 5 kW
b) 8.46 kW
c) 12.5 kW
d) 6.25 kW

6. A carrier is simultaneously modulated by two sine waves with modulation indices of 0.4 and 0.3. The resultant modulation index will be
a) 1.0
b) 0.7
c) 0.5
d) 0.35

7. The aerial current of an AM transmitter is 18 A when unmodulated but increases to 20 A when modulated.The modulation index is
a) 0.68
b) 0.73
c) 0.89
d) 0.95

8. A 2 MHz carrier is amplitude modulated by a 500 Hz modulating signal to a depth of 70%. If the unmodulated carrier power is 2 kW, the power of the modulated signal is
a) 2.23 kW
b) 2.36 Kw
c) 1.18 kW
d) 1.26 kW

9. In a DSB-SC system with 100% modulation, the power saving is
a) 100%
b) 55%
c) 75%
d) 100%

10. A 10 kW carrier is sinusoidally modulated by two carriers corresponding to a modulation index of 30% and 40% respectively. The total radiated power is
a) 11.25 kW
b) 12.5 kW
c) 15 kW
d) 17 kW