# Analog Communication 4

Electronic Engineering MCQ Question Papers: ENTC, IT Interview Placement

Subject:  Analog Communication 4

Part 4: List for questions and answers of Analog Communication

Q1. For a FM signal v(t) = 15 cos ( 10 * 10^8t + 10 sin 1220t), calculate

1. Carrier frequency

2. Modulating frequency

a) 159.1MHz, 194.1Hz

b) 185.5MHz, 200.15Hz

c) 350.1MHz, 200.1Hz

d) 159.1Hz, 194.1Hz

Q2. Guard bands are provided in FM signal to

a) Prevent interference from adjacent channels

b) To increase the noise

c) To increase bandwidth

d) None of the above

Q3. Maximum frequency deviation and the maximum bandwidth allowed for commercial FM broadcast is

a) 80KHz, 160Khz

b) 75KHz, 200Khz

c) 60KHz, 170Khz

d) 75KHz, 250Khz

Q4. In frequency modulation,

a) Armstrong method is used for generation

b) Multiple side bands are generated

c) The FM signal has infinite bandwidth

d) All of the above

Q5. After passing the FM signal through mixer, what is the change in the frequency deviation Δ  when the modulating frequency is doubled?

a) Becomes 2 Δ

b) Becomes Δ  /2

c) Becomes Δ ^2

d) Remains unchanged

Q6. Calculate the modulation index in an FM signal when fm (modulating frequency) is 250Hz and  Δf   (frequency deviation) is 5KHz

a) 20

b) 35

c) 50

d) 75

Q7. What is the value of carrier frequency in the following equation for the FM signal?

v(t)= 5 cos(6600t+ 12sin2500t)

a) 1150 Hz

b) 6600 Hz

c) 2500 Hz

d) 1050 Hz

Q8. Calculate the dissipation in power across 20Ω resistor for the FM signal

v(t)= 20 cos(6600t+ 10sin2100t)

a) 5W

b) 20W

c) 10W

d) 400W

Q9. Calculate the maximum frequency deviation for the FM signal

v(t) = 10 cos (6000t+ 5sin2200t)

a) 2200 Hz

b) 6000 Hz

c) 1750 Hz

d) 11000 Hz

Q10. The equation v(t) = A cos [wt + kp f(t)] represents the signal as

a) Phase modulated signal

b) SSBSC signal

c) DSB SC signal

d) None of the above

Q11. The ratio of maximum peak frequency deviation and the maximum modulating signal frequency is termed as

a) Frequency deviation

b) Deviation ratio

c) Signal to noise ratio

d) Frequency spectrum

Q12. Carson’s rule is used to calculate

a) Bandwidth of FM signal

b) Signal to noise ratio

c) Modulation index

d) Noise figure

Q13. The increase or decrease in the frequency around the carrier frequency is termed as

a) Figure factor

b) Frequency deviation

c) Modulation index

d) Frequency pectrum

Q14. Phase-locked loop can be used as

a) FM demodulator

b) AM demodulator

Q15. Change in instantaneous phase of the carrier with change in amplitude of the modulating signal generates

a) Direct FM

b) Indirect FM

c) SSB-SC

d) DSB-SC

Q16. VCO is used to generate

a) Direct FM

b) Indirect FM

c) SSB-SC

d) DSB-SC

Q17. FM is advantageous over AM as

a) The amplitude of FM is constant. So transmitter power remains unchanged in FM but it changes in AM

b) The depth of modulation in FM can be changed to any value by changing the frequency deviation. So the signal is not distorted

c) There is less possibility of adjacent channel interference due to presence of guard bands

d) All of the above

Q18. The range of modulating frequency for Narrow Band FM is

a) 30 Hz to 15 KHz

b) 30 Hz to 30 KHz

c) 30 Hz to 3 KHz

d) 3 KHz to 30 KHz

Q19. The ratio of actual frequency deviation to the maximum allowable frequency deviation is called

a) Multi tone modulation

b) Percentage modulation

c) Phase deviation

d) Modulation index

Q20. What is the maximum modulating frequency allowed in commercial FM broadcastings?

a) 40 KHz

b) 75 KHz

c) 15 KHz

d) 120 KHz

Part 4: List for questions and answers of Analog Communication