# Analog Communications Questions and Answers – Noise for SSB-SC

This set of Analog Communications online quiz focuses on “Noise for SSB-SC”.

1. The IF bandwidth of a radar receiver is inversely proportional to the __________
a) pulse repetition frequency
b) pulse width
c) pulse amplitude
d) pulse code

Explanation: The IF bandwidth of a radar receiver is inversely proportional to the pulse width.

2. Frequency components of an AM wave are?
a) Carrier frequency (ωc) with amplitude A
b) Lower side band (ωc + ωm) having amplitude mA4
c) Upper side band (ωc – ωm) having amplitude mA4
d) Carrier frequency (ωc) with amplitude A2

Explanation: Actually the frequency components of AM waves are – Carrier frequency (ωc) with amplitude A, Lower side band (ωc – ωm) having amplitude mA2 and Upper side band (ωc + ωm) having amplitude mA2 (where m represents modulation index).

3. Which of the following statement is true, if a return echo arrives after the allocated pulse interval?
a) it will interfere with the operation of a transmitter
c) overlap of signals
d) target will appear closer than it really is

Explanation: If a return echo arrives after the allocated pulse interval then the target will always appear closer than it really is.

4. Which of the following statement is true about the spectrum of frequency modulated wave?
a) carrier frequency starts decreasing at a faster rate when the modulation index is large
b) the amplitude of any sideband is totally depends on modulation index
c) total number of sidebands is completely depend on the modulation index
d) carrier frequency is amplified

Explanation: In frequency modulation, frequency of wave is modulated with respect to the wave being propagated. In frequency modulation, the amplitude of any side band depends on modulation index.

5. If a FM signal has modulation index m, then what will be its modulation index after passing through frequency tripler?
a) m3
b) m
c) 3m
d) 9m

Explanation: Frequency multiplier is an electronic circuit that generates an output signal whose output frequency is a multiple of its input frequency. So after passing through frequency tripler, new modulation index will be thrice the input which is 3m.
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6. A pre emphasis circuit provides extra noise immunity by __________
a) boosting the base frequencies
b) amplifying the higher audio frequencies
c) amplifying the whole audio band
d) converting the phase modulation to FM

Explanation: Pre emphasis is used to improve the quality of signal at the output of data transmission. A pre emphasis circuit provides extra noise immunity noise amplifying the higher audio frequencies.

7. Which one of the following is not an advantage of FM over AM?
a) Better noise immunity is provided
b) Higher bandwidth is required
c) Transmitting power is useful
d) Less modulating power is required

Explanation: Frequency Modulation has many advantages over amplitude modulation such as it has better noise immune, it requires less modulating power. But it requires higher bandwidth is not an advantage of FM when compared to AM.

8. Which of the following statement about Amplitude Limiter is not true?
a) The circuit is always biased in class C amplifier
b) When the input increases and becomes greater than the threshold of limiting, the gain starts decreasing
c) The output must be tuned
d) Leak-type bias must be used

Explanation: Amplitude Limiter removes the amplitude of output signals to the desired margin irrespective of variations in the input signal. It is always biased in class C amplifier by virtue of the leak-type bias. Amplitude limiter is present in FM receiver and not AM receiver.

9. The typical squelch circuit cuts off __________
a) An audio amplifier when the carrier is absent
b) RF interference when the signal is weak
c) An IF amplifier when Automatic Gain Control is maximum
d) An IF amplifier when Automatic Gain Control is minimum

Explanation: The use of squelch circuit is to suppress the audio or video output of a receiver in the absence of a sufficiently strong desired input signal.

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