This set of Aircraft Maintenance Multiple Choice Questions & Answers (MCQs) focuses on “Aviation Communication Systems – Radar-2”.
1. Which of the following is not a type of polarization used by RADARS?
Explanation: RADARS do not use diagonal polarization. They only use horizontal, vertical, linear, and circular polarization. It is used in order to detect different types of reflections.
2. Circular polarization technique is used to nullify the interference caused due to ________
Explanation: Circular polarization technique is used to nullify the interference caused due to rain. Random polarization technique is used for hard surfaces such as rocks, fractal surfaces or soil.
3. The linear polarization returns usually indicate concrete surfaces.
Explanation: False, the linear polarization returns usually indicate metal surfaces. The orientation of a linearly polarized EM wave is defined by the direction of the electric field vector.
4. A radar beam usually follows a _________ path in vacuum.
Explanation: A radar beam usually follows a linear path in vacuum. Although the beam follows a slightly curved path in the atmosphere, this change is due to the variation of the RI of air.
5. Reflected signals ______ rapidly as distance increases.
Explanation: The amount of reflected signals decline rapidly with an increase in the distance travelled by the signal. Further, the noise component brings in a radar range limitation, affecting the performance of the device.
6. What is the full form of SNR?
a) Shot to noise ratio
b) Signal to noise ratio
c) Sign to noise ratio
d) Side to noise ratio
Explanation: SNR refers to signal to noise ratio. It can be defined as the ratio of the signal power to the noise power within the desired signal. Higher the SNR, better is the system.
7. Which of the following is a measure of the noise produced by a receiver compared to an ideal receiver?
a) Noise to signal ratio
b) Signal to noise ratio
c) Noise figure
d) Noise number
Explanation: Noise figure is a measure of the noise produced by a receiver compared to an ideal receiver. It is a figure that needs to be minimized to improve performance.
8. The Doppler device separates any clutter from an aircraft by means of a ________ spectrum.
Explanation: The Doppler device separates any clutter from an aircraft by means of a frequency spectrum. The separation is done in such a manner that each individual signal can be separated by using various velocity differences.
9. Which of the following describes the time taken by a radar pulse to travel one nautical mile, reflect off a target, and then return to the radar antenna?
a) Radar distance
b) Unit radar
c) Radar mile
d) Radar return
Explanation: Radar mile is a term used to describe the amount of time a radar pulse takes in order to travel one nautical mile, then reflect off a target and again return back to the radar antenna. One nautical mile is defined as 1,852 m.
10. The frequency shift is inversely proportional to the distance travelled.
Explanation: False, the frequency shift in a radar instrument is directly proportional to distance travelled by the instrument. Also, the frequency shift increases with increased time delay in the instrument.
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