CMRT Radar System Fundamentals 5

Question 1

What does the term 'antenna gain' mean in the context of a marine radar antenna?

Accepted Answer

The ratio of the antenna's radiated intensity in its principal direction to that of an isotropic radiator

Answer

Antenna gain (in dBi) expresses how much more power the antenna concentrates in its main beam direction compared to a hypothetical isotropic radiator; higher gain means a narrower, more focused beam.

Question 2

In a marine radar system, what is the purpose of the automatic frequency control (AFC) circuit?

Accepted Answer

Lock the local oscillator frequency to maintain a constant IF despite magnetron frequency drift

Answer

The magnetron's frequency can drift with temperature and aging; AFC continuously compares the IF to the desired value and adjusts the local oscillator to keep the difference (IF) constant.

Question 3

What is the 'radar equation' fundamental relationship between detection range and transmitter peak power?

Accepted Answer

Range is proportional to the fourth root of peak power (R ∝ P^0.25)

Answer

The radar range equation shows R_max ∝ (P_t)^(1/4); to double detection range, peak power must increase by a factor of 16, making power a relatively inefficient way to extend range.

Question 4

Which IMO regulation requires most SOLAS vessels to carry a marine radar capable of operating on the 9 GHz band?

Accepted Answer

SOLAS Chapter V (Safety of Navigation), Regulation 19

Answer

SOLAS Chapter V, Regulation 19 specifies navigational equipment requirements by vessel size and trade area, mandating radar (9 GHz X-band) for vessels above specified tonnage thresholds.

Question 5

What is 'target glint' and how does it affect radar measurements?

Accepted Answer

Rapid fluctuation of a target's echo amplitude and apparent position due to interference from multiple reflection points on the target

Answer

Glint occurs when a target with multiple scattering centers produces a composite echo whose amplitude and apparent angle of arrival fluctuate rapidly, introducing bearing and range measurement errors.

(CMRT) Certified Marine Radar Technician Practice Test

(CMRT) Certified Marine Radar Technician Practice Test

CMRT Radar System Fundamentals 5