Analog Communications Questions and Answers – Noise in AM

This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Noise in AM”.

1. Why a helical antenna is used for satellite tracking?
a) because of its circular polarization
b) because of its broad bandwidth
c) because of its low bandwidth
d) because of rectangular polarization

Explanation: A helical antenna generally consists of a conducting wire which is wound in the form of a helix. It generally exhibits circular polarization due to which it is mostly used for satellite tracking.

2. Which one of the following noise becomes of great importance at high frequencies?
a) flicker noise
b) shot noise
c) impulse noise
d) transit-time noise

Explanation: If the time taken by electrons to travel from emitter to collector becomes comparable to the period of the signal which is amplified which is only possible at high frequencies called transit time. At transit time noise input admittance of the transmitter increases.

3. Which one of the following statement is false?
a) High Frequency mixers are generally noisier
b) Voltage of impulse noise is independent of bandwidth
c) Thermal noise is not dependent on frequency
d) Flicker noise occurs at low frequency

Explanation: Impulse noise includes unwanted noise which is almost instantaneous and has a sharp sound. High level of such noise may damage internal organs. It depends on bandwidth of the signal.

4. Which of broad classifications of noise are most difficult to treat?
a) noise generated in the receiver
b) noise generated in the transmitter
c) external noise
d) internal noise

Explanation: Noise which is generated inside the receiver is very much difficult to handle.

5. What points must be important to remember, when we deal with random noise calculations?
a) all calculations are based on peak to peak values
b) calculations are based on quantised values
c) calculations are based on average values
d) calculations are based on RMS values

Explanation: All calculations of any random signals are done by using their RMS (Root Mean Square) values.
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6. Which of the following statement is true?
a) Random noise power is inversely proportional to bandwidth
b) Flicker noise occurs at high frequency
c) Noise mixers are caused by inadequate image frequency rejection
d) A random voltage across a resistance cannot be calculated

Explanation: Image frequency rejection is the ratio of intermediate frequency (IF) produced by desired input frequency to that which is produced by the image frequency.

7. Which of the following statement is false?
a) Modulation is used to reduce the bandwidth
b) Modulation is used to separate different transmissions
c) Modulation is used to allow the use of practical antennas
d) Modulation is used to ensure that wave is transmitted over long distances

Explanation: Modulation is the process of varying one or more properties of a periodic waveform that contains the information to be transmitted. It is used to separate different transmission signal so they do not get mixed, it ensure that the wave travels a long distance. But it is not used to reduce bandwidth.

8. Which of the steps is not included in the process of reception?
a) encoding
b) decoding
c) demodulating
d) filtering

Explanation: Communication process is the set of some sequential steps which is involved in transferring messages as well as feedback. The steps included in process of reception are decode – to decode the message signal, interpretation – to interpret the message carefully, and storing – to store the message carefully so that it can use in future if needed.

Sanfoundry Global Education & Learning Series – Analog Communications.