# Analog Communications Questions and Answers – Comparision of SSB Suppression Techniques

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This set of Analog Communications Interview Questions and Answers for Experienced people focuses on “Comparision of SSB Suppression Techniques”.

1. What is the expected modulation index in case of wide band FM?
a) less than 1
b) 1
c) 12
d) more than 1

Explanation: For producing Narrow band frequency modulated wave, modulation index should be less than or equal to1. For wideband frequency modulated wave, modulation index should be greater than 1.

2. What is the expected modulation index in case of narrow band FM?
a) less than or equal to 1
b) infinite
c) 1.5
d) more than 1

Explanation: For producing Narrow band frequency modulated wave, modulation index should be less than or equal to1. For wideband frequency modulated wave, modulation index should be greater than 1.

3. Which of the following statement is true about pulse position modulation system?
a) pulses have constant width but varying amplitude
b) pulses have constant amplitudes and constant widths
c) pulses have constant amplitude but varying widths
d) pulses have varying width and varying amplitude

Explanation: Pulse Position Modulation (PPM) is a type of modulation process in which position of the pulse of the carrier wave is varied with respect to the instantaneous position values of the message signal. In pulse modulation, pulses have constant amplitude and widths.

4. IF stage is a receiver employs ________
a) impedance coupling
b) capacitive coupling
c) single tuned transformer coupling
d) double tuned transformer coupling

Explanation: A frequency to which a carrier wave is shifted as an intermediate step is known as Intermediate Frequency. It employs double tuned transformer coupling.

5. A 1000 KHz carrier is modulated with 300 Hz, 8000 Hz and 2 KHz waves. Determine the frequencies whose chances of occurring in output is least?
a) 1000 KHz
b) 1002 KHz
c) 998 KHz
d) 999.2 KHz

Explanation: Frequencies present in output are of the form fc ± fm, fc ± 2fm, fc ± 3fm. And 1000 KHz is a multiple of none in the range. Whereas, rest options are one of the multiples in the range.

6. In higher power AM transmission, modulation is done at _________
a) Source stage
b) Transducer Stage
c) Oscillator stage
d) RF power stage

Explanation: RF power amplifier converts a low power radio frequency signal to high power. Modulation is done at RF power stage for high power AM transmission.

7. If modulation index of an AM was in changed from 0 to 1, then transmitted power ________
a) increases by 100%
b) increases by 50%
c) increases by 75%
d) increases by 25%

Explanation: Modulation index indicates amount of modulation in the carrier signal. If modulation index changes to 1 from 0, its transmitted power increases by 50%.

8. ________ microphones works on piezoelectric effect.
a) Crystal
b) Carbon
c) Moving coil
d) Condenser

Explanation: Piezoelectric effect seen in materials generate an electric charge when subjected to mechanical stress. Crystals producing piezoelectric effect generate voltages when deformed. Crystal microphones works on it only.

9. In PCM system, output S/N increases ________
a) parabolically with bandwidth
b) exponentially with bandwidth
c) inversely with bandwidth
d) linearly with bandwidth

Explanation: Pulse code modulation (PCM) is a digital form of communication. Pulse Code Modulation is a technique in which the amplitude of an analogue signal is converted to a binary value represented as a series of pulses. if we calculate the ratio of signal to noise ratio for different bandwidth then we observe that it increases exponentially with it.

10. Companding is used in PCM transmitters to overcome quantizing noise in PCM.
a) True
b) False 