Radar/ARPA - RADAR AND AUTOMATIC RADAR PLOTTING AID |
VERIFIED EXAM QUESTIONS AND ANSWERS - LATEST VERSION
2026/2027
1. What does RADAR stand for? RAdio Detection And Ranging.
2. What is the basic principle of radar? Transmitting a radio pulse and
measuring the time delay of its echo.
3. What is the speed of radio waves (light)? Approximately 300,000
km per second or 162,000 nautical miles per second.
4. How is radar range calculated? Range = (Time delay × Speed of
light) / 2.
5. Why divide by 2 in the range equation? Because the wave travels to
the target and back.
6. What is a Pulse Repetition Frequency (PRF)? The number of pulses
transmitted per second.
7. What is Pulse Repetition Period (PRP)? The time between the start
of one pulse and the start of the next.
8. What is Pulse Length (Pulse Width)? The duration of the
transmitted pulse in microseconds.
9. What is Peak Power? The power contained within the individual
transmitted pulse.
10. What is Average Power? The power averaged over the Pulse
Repetition Period.
11. What determines minimum range? Pulse length + recovery
time of the receiver.
, 12. What determines maximum range? Peak power, PRF, and
target characteristics.
13. What is the "Blind Range"? A range where echoes from distant
targets return after the next pulse has been transmitted, going uns
detected.
14. What is a Radar Mile? The time it takes a radar pulse to travel
1 NM and return (12.36 microseconds).
15. What frequency bands are used for marine radar? X-band (9
GHz) and S-band (3 GHz).
16. What is the wavelength of X-band? Approximately 3 cm.
17. What is the wavelength of S-band? Approximately 10 cm.
18. Which band provides better target discrimination? X-band
(shorter pulse/wavelength).
19. Which band performs better in rain/clutter? S-band (less
attenuation by rain).
20. What is Beam Width? The angular width of the radar beam,
usually measured between half-power points.
21. What is Horizontal Beam Width (HBW)? The angular width of
the beam in the horizontal plane (typically 1-2 degrees).
22. What is Vertical Beam Width (VBW)? The angular width of the
beam in the vertical plane (typically 15-30 degrees).
23. Why is HBW narrow? To provide good bearing resolution.
24. Why is VBW wide? To detect targets despite ship roll and
pitch.
25. What is the relationship between antenna size and beam
width? Larger antenna = narrower beam width.
26. What is Radar Cross Section (RCS)? A measure of how
detectable an object is by radar.
27. What is the inverse square law? Signal strength decreases
proportionally to the square of the distance.
28. What does "Ranging" mean? Measuring the distance to a
target.
VERIFIED EXAM QUESTIONS AND ANSWERS - LATEST VERSION
2026/2027
1. What does RADAR stand for? RAdio Detection And Ranging.
2. What is the basic principle of radar? Transmitting a radio pulse and
measuring the time delay of its echo.
3. What is the speed of radio waves (light)? Approximately 300,000
km per second or 162,000 nautical miles per second.
4. How is radar range calculated? Range = (Time delay × Speed of
light) / 2.
5. Why divide by 2 in the range equation? Because the wave travels to
the target and back.
6. What is a Pulse Repetition Frequency (PRF)? The number of pulses
transmitted per second.
7. What is Pulse Repetition Period (PRP)? The time between the start
of one pulse and the start of the next.
8. What is Pulse Length (Pulse Width)? The duration of the
transmitted pulse in microseconds.
9. What is Peak Power? The power contained within the individual
transmitted pulse.
10. What is Average Power? The power averaged over the Pulse
Repetition Period.
11. What determines minimum range? Pulse length + recovery
time of the receiver.
, 12. What determines maximum range? Peak power, PRF, and
target characteristics.
13. What is the "Blind Range"? A range where echoes from distant
targets return after the next pulse has been transmitted, going uns
detected.
14. What is a Radar Mile? The time it takes a radar pulse to travel
1 NM and return (12.36 microseconds).
15. What frequency bands are used for marine radar? X-band (9
GHz) and S-band (3 GHz).
16. What is the wavelength of X-band? Approximately 3 cm.
17. What is the wavelength of S-band? Approximately 10 cm.
18. Which band provides better target discrimination? X-band
(shorter pulse/wavelength).
19. Which band performs better in rain/clutter? S-band (less
attenuation by rain).
20. What is Beam Width? The angular width of the radar beam,
usually measured between half-power points.
21. What is Horizontal Beam Width (HBW)? The angular width of
the beam in the horizontal plane (typically 1-2 degrees).
22. What is Vertical Beam Width (VBW)? The angular width of the
beam in the vertical plane (typically 15-30 degrees).
23. Why is HBW narrow? To provide good bearing resolution.
24. Why is VBW wide? To detect targets despite ship roll and
pitch.
25. What is the relationship between antenna size and beam
width? Larger antenna = narrower beam width.
26. What is Radar Cross Section (RCS)? A measure of how
detectable an object is by radar.
27. What is the inverse square law? Signal strength decreases
proportionally to the square of the distance.
28. What does "Ranging" mean? Measuring the distance to a
target.
