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Correct AnswerLosses can be kept reasonable at S-band frequencies and the installation cost is lower.
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A waveguide will not support the power density required for modern S-band RADAR transmitters.
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S-band waveguide flanges show too much leakage and are unsafe for use near personnel.
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Dimensions for S-band waveguide do not permit a rugged enough installation for use by ships at sea.
The S-band spans 2-4GHz and at those frequencies coaxial cable's losses might not be significant enough to incur the added cost and complexitiy of deploying a waveguide instead, so Answer A. is the right one.
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Not operating other devices when RADAR is in use.
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Correct AnswerProperly grounding, bonding, and shielding all units.
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Using a high pass filter on the power line.
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Using a link coupling.
Properly grounding, bonding, and shielding all RF equipment and associated power supplies is a MUST to reduce interference at the receiver from nearby RF sources, so Answer B. is the right one.
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They must be insulated to prevent electric shock.
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To prevent damage from shipboard personnel.
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To minimize reception of horizontally polarized returns.
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Correct AnswerTo prevent accumulation of condensation.
Water in a waveguide absorbs RF reducing the transmitted power reaching the antenna and the signal strength from the antenna received by the receiver.
A horizontal run allows any water or humidity entering the waveguide to accumulate while a sloping run will cause the water to drip out of a small hole at the lowest point of the waveguide.
Answer D. is the right one.
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Correct AnswerMoisture can accumulate in the waveguide.
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The waveguide can sag, causing loss of signal.
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Excessive standing waves can occur.
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The polarization of the signal might shift.
Water in a waveguide absorbs RF reducing the transmitted power reaching the antenna and the signal strength from the antenna received by the receiver.
A horizontal run allows any water or humidity entering the waveguide to accumulate while a sloping run will cause the water to drip out of a small hole at the lowest point of the waveguide.
Answer A. is the right one.
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Slightly bent for maximum gain.
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Correct AnswerAs straight as possible to reduce distortion.
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At 90 degree angles to improve resonance.
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As long as possible for system flexibility.
RADAR pulses have very short rise and fall times.
Pulse trains thus make-up a square wave.
Square waves have a very large number of harmonics.
The speed of an electromagnetic wave transiting a turn in a waveguide depends to a small extent on the frequency of the wave.
The fundamental and harmonic frequencies in a square wave will thus take a slightly different time to transit through each turn.
The slight changes in the transit time will cause the different frequencies making-up each pulse to arrive at slightly different times at the antenna from the transmitter and again at the receiver from the antenna.
These small time differences will blur the pulse edges in effect increasing the pulse rise and fall times.
Increased pulse rise and fall times will decrease the resolution of the RADAR.
Since turns in a waveguide distort the RF travelling through the waveguide, it is advisable to keep the waveguides as straight as possible.
Answer B. is the right answer.
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Allow the shortest cable/waveguide run.
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Maximum height for best long range operation.
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Correct AnswerThe antenna is in a location that is not shadowed by other structures.
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Easy access for maintenance.
The most important factor to consider in locating the antenna is that it should be in a location that is not shadowed by other structures.
When positioning the antenna for a radar or communication system, it is essential to ensure an unobstructed view of the surroundings. If the antenna is obstructed or shadowed by other structures, such as buildings, masts, or other equipment, it can lead to several issues:
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Reduced Coverage: Obstructed antennas may have limited coverage, resulting in blind spots or gaps in the radar or communication range. This can lead to missed targets or communication disruptions.
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Signal Attenuation: The presence of obstacles can cause signal reflections, diffraction, and attenuation. This can weaken the transmitted or received signals, affecting the system's performance and range.
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Multipath Interference: When signals bounce off nearby structures and arrive at the antenna from multiple paths, it can cause interference and signal distortion.
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Signal Blockage: Antenna shadowing can block the direct line of sight between the antenna and distant targets, hindering accurate target detection and ranging.
To ensure optimal performance and coverage, the antenna should be placed in a location that allows it to have a clear line of sight to the targets and the surrounding environment.
Mnemonic: "Unobstructed View"
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