This set of Analog Communications Interview Questions and Answers focuses on “Modulation Using Non-Linear Devices (Balanced Modulator)”.
1. The approximate aspect ratio for television is ________
a) 2 : 1
b) 3 : 2
c) 4 : 3
d) 3 : 4
Explanation: Aspect ratio is the ratio of width to the height of image (or screen). Most common videographic aspect ratio is 4:3.
2. Signal to Noise ratio for a hi-fi system is equal to ________
a) 50 dB
b) 100 dB
c) 75 dB
d) 10 dB
Explanation: Signal to Noise ratio compares signal power to noise power. It is generally expressed in decibels(dB). For a hi-fi system it should be equal to 50dB.
3. What is the use of SSB?
a) It halves the bandwidth
b) It increases the bandwidth
c) It decreases the bandwidth by 25%
d) It decreases the bandwidth by 37%
Explanation: The two sidebands in DSB-SC wave are exactly same, so in SSB-SC one sideband is removed which reduces its bandwidth to half.
4. Approximate how many times odd and even fields of television system are scanned?
a) 25 times each
b) 50 times each
c) 50 times each but alternately
d) 25 times each but alternately
Explanation: In television system in India, each of odd and even fields are scanned 25 times but alternately.
5. Any signal and its Hilbert transform have same energy density spectrum.
Explanation: A signal and its Hilbert transform have same amplitude spectrum i.e. they have same energy density spectrum and also correlation spectrum.
6. If the spectrum of a narrow band noise is symmetrical and it has a power density spectrum 4×10-6. Power density of quadrature component is ________
a) 2 x 10-6
b) 5 x 10-6
c) 3 x 10-6
d) 4 x 10-6
7. What is the capacitive reactance for DC signals?
b) very low
c) equal to one
Explanation: Frequency of DC signals is zero. For zero frequency, capacitive reactance XC is infinite.
8. If a FM signal having modulation index m_f is passed through a frequency tripler, then the modulation index of output of frequency tripler is ________
c) 1⁄3 mf
d) 1⁄9 mf
Explanation: When a FM signal is passed through a frequency tripler, it increases its modulation index 3 times. So the modulation index of output is 3mf.
9. What are the two major drawbacks of delta modulation?
a) Slope Overload and Granular noise
b) Slope Overload and Serration noise
c) Serration noise and Granular noise
d) Slope Overload and Channel Noise
Explanation: The two major drawbacks in delta modulation are slope overload and granular noise. When step size becomes too small to track the original waveform it generates an error whom we called as slope overload and Granularity occurs when step size is too large.
10. Beam width of antenna is expressed in ________
Explanation: Angular separation between the two half power points are called as beam width. It is usually expressed in metres.
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