This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Noise in Phase Modulation”.
1. In AM receiver, the oscillator frequency is always ________
a) lower than signal frequency
b) higher than signal frequency
c) equal to signal frequency
d) equal to 1000KHz
Explanation: The frequency of oscillator in amplitude modulated system is always higher than the frequency of signal.
2. What you understand by the term discone antenna?
a) combination of disc and cone
b) combination of disc and cone with a spacing of ʎ⁄4
c) combination of disc and cone with a spacing of ʎ⁄2
d) same as a simple antenna
Explanation: Discone antenna is a combination of disc and cone. It is usually vertically mounted, with disc at top and the cone beneath.
3. Which of the following receiver does not have amplitude limiter stage?
d) Both AM and FM
Explanation: Amplitude limiter removes the amplitude of output signal to a desired amplitude irrespective of variations in the input signal. Amplitude modulated system does not need amplitude limiter stage.
4. Most of the amplification of received signal is obtained in a superheterodyne receiver from ________ stage.
c) Power Amplifier
d) can be from IF or RF
Explanation: In superheterodyne receiver, most of the received signals gets amplified from intermediate frequency (IF).
5. Padder capacitor can be used to achieve three point tracking.
Explanation: To achieve three point tracking a capacitor is connected in series with local oscillator coil. This capacitor is called padder capacitor.
6. Any signal and its Hilbert transform are mutually orthogonal.
Explanation: Consider f(t) be any signal and fh(t) is its Hilbert transform. If we integrate both of them under proper boundary conditions, we get 0 which shows that both are mutually perpendicular i.e.
7. If the output power of radio receiver is doubled then the volume is increased by _________
a) 3 dB
b) 2 dB
c) -3 dB
d) -2 dB
Explanation: Volume of a radio receiver is increased by 3 dB if we double the output power of a radio receiver.
8. If selectivity is poor then the receiver has poor _________
b) diverse reception
d) transmission and reception
Explanation: By selectivity, receiver responds only to the radio signals, it is tuned to and reject the other signals. If a receiver has poor selectivity then obviously its blocking of unwanted signals is also poor.
9. In FM the carrier deviation is determined by ________
Explanation: In frequency modulated system, it is the modulation who is responsible for the deviation of carrier wave.
10. In systems, pre-emphasis is used to amplify ________
a) high frequency
b) low frequency
c) both high and low frequency
Explanation: Pre-emphasis is used in frequency modulated or phase modulated transmitters to equalize the drive power of transmitting signal in terms of deviation ratio. It is done at the transmitter. The modulating signal is passed through a simple network at the transmitter which amplifies the high frequency components.
Sanfoundry Global Education & Learning Series – Analog Communications.
To practice all areas of Analog Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.