Communication Systems questions with answers part1

Q1. A signal of maximum frequency of 1 KHz is sampled at Nyquist Rate. The interval between two successive samples is:
(A) 50 micro seconds
(B) 100 micro seconds
(C) 500 micro seconds
(D) 1000 micro seconds

Q2. Which of the following is not a microwave generation source?
(A) Klystron
(B) Magnetron
(C) TWT
(D) Diode

Q3. The speed of BRI ISDN interface is
(A) 2B + D
(B) 2D + B
(C) 30B + D
(D) 30D + B

Q4. Digital transmission efficiency is given by
(A) information bits/total bits
(B) total bits/information bits
(C) redundant bits/information bits
(D) none of the above

Q5. The process of compressing the digital codes at the transmitter and then expanding them back to their original form at receiver is known as
(A) Quantizing
(B) companding
(C) step sizing
(D) modulation

Q6. Armstrong modulator generates
(A) Phase modulated signal
(B) Frequency modulated signal
(C) Both of these
(D) Pulse code modulated signal

Q7. In PCM system the SNR of the output signal increases
(A) Inversely with bandwidth
(B) Exponential with bandwidth
(C) With rate of sampling
(D) At low frequencies only

Q8. Companding is used
(A) To limit amplitude in PCM transmitters.
(B) In PWM for working it with TDM
(C) To protect small signals in PCM from quantizing distortion
(D) In PCM to reduce the SNR

Q9. To increase the Q factor of an induction, it wound with
(A) thicker wire
(B) thinner wire
(C) longer wire
(D) wire with heavy insulation

Q10. With 100% modulation, ratio of side band power to total power transmitted in an amplitude modulated wave is
(A) 1
(B) 01/03/20
(C) 01/02/20
(D) 01/04/20

Q11. An FM transmitter has maximum frequency deviation of 75 KHz and reproduces audio signal up to 15 KHz. Minimum channel width required, in KHz is
(A) 180
(B) 120
(C) 90
(D) 60

Q12. The audio frequency range lies between
(A) 20 to 20,000 Hz
(B) 20 to 20,000 KHz
(C) 400 to 8,000Hz
(D) 500 to 5,000 Hz

Q13. Which of the following pulse systems requires higher bandwidth
(A) PAM
(B) PDM
(C) PPM
(D) none of these

Q14. Which of the following pulse systems is preferred for communication in presence of noise?
(A) PAM
(B) PDM
(C) PPM
(D) none of above

Q15. In PPM, message resides in
(A) Pulse frequency
(B) Pulse Amplitude
(C) time location of pulse edges
(D) none of these

Q16. In FM, the noise can be further decreased by
(A) decreasing deviation
(B) increasing deviation
(C) keeping deviation constant
(D) none of these

Q17. The function of AM detector circuit is
(A) to rectify the input signal
(B) to discard the carrier
(C) to provide the audio signal
(D) All of the above

Q18. In an AM wave with 100% modulation, the carrier is suppressed. The percentage of power saving will be
(A) 100.00%
(B) 50.00%
(C) 25.00%
(D) 66.70%

Q19. The AGC voltage in a radio receiver is proportional to
(A) the amount of modulation
(B) the amplitude of audio signal
(C) the amplitude of IF carrier
(D) the amplitude of radio signal

Q20. Maximum undistorted power output of a transmitter is obtained when its modulation is:
(A) more than 100%
(B) 100.00%
(C) ess than 100%
(D) 50.00%