16. The main advantage of the pre-emphasis circuit in FM transmitter is
- To increase the carrier power
- To improve the signal to noise ratio at low audio frequencies
- To increase the bandwidth of side band
- To improve the signal to noise ratio at high audio frequencies
17. In phase modulation, phase deviation is proportional to
- Carrier amplitude
- Carrier phase
- Message signal
- Message signal frequencies
18. An indirect way of generating FM, is
- The Armstrong modulator
- The reactance FET modulator
- The varactor diode modulator
- The reactance bipolar transistor modulator
19. The de-emphasis filter in an FM receiver comes
- Before FM demodulator
- After FM demodulator and before baseband filter
- After baseband filter
- Before RF amplifier
20. Consider the following statements about FM
- Modulation index determines the number of significant sideband components.
- Theoretical bandwidth is infinite.
- Carrier suppression is not possible
- Sidebands are not symmetric about carrier
Which of these statements is/are correct?
- i, ii, iii and iv
- i and ii only
- iii only
- iii and iv only
21. If an FM wave is represented by the equation e = 10 sin (9 x 108t + 4 sin 1500t), then what is the carrier frequency?
- 127.32 MHz
- 150.00 MHz
- 143.31 MHz
- 208.00 MHz
22. Which one of the following factors is limited in case of F.M.?
- Maximum frequency deviation
- Maximum permissible modulation index
- Signal to noise voltage ratio
- Minimum permissible modulation index
23. An F.M. signal which is modulated by a 4 kHz sine wave reaches a maximum frequency of 100.01 MHz and minimum frequency of 99.97 MHz, then what is the one side frequency deviation of the signal?
- 6.67
- 5
- 10
- 20
24. An angle modulated signal is described by the equation
xc(t) = 10 cos[2πfct + 10 sin(4000πt) + 5 sin 2000πt]
What is the bandwidth of this modulated signal?
- 6 kHz
- 45 kHz
- 54 kHz
- 63 kHz
25. With the increase in the transmission bandwidth, received signal-power in AM and FM will respectively
- increase, increase
- remain same, increase
- increase, remain same
- remain same, remain same
26. What is the automatic frequency control voltage of the FM transmitter VCO?
- dc voltage
- Sine wave voltage
- Square wave voltage
- Ramp voltage
27. PLL demodulators are now used in commercial receivers because of which of the following
- PLL demodulators do not exhibit threshold in S/N performance.
- No requirement of pre-emphasis and de-emphasis.
- Cheap PLL ICs are available.
Select the correct answer using the code given below.
- i and ii
- ii and iii
- i, ii and iii
- i and iii
28. Which of the following are the advantages of FM broadcasting over AM broadcasting
- Better S/N ratio
- Not subject to signal fading
- Power efficiency is superior
- Demodulation is simpler
Select the correct answer from the code given below.
- i and ii
- ii and iii
- i, ii and iii
- i and iii
29. Which one of the following signals can be applied to a delta modulator whose step size is 0.1 V and sampling frequency is 20π kHz so that no slope overload occurs?
- 2 sin (1200πt)
- 1 sin (2600πt)
- 3 sin (1000πt)
- 4 sin (400πt)
30. Which of the following is not a component of PLL?
- Frequency multiplier
- Phase detector
- VCO
- Loop filter