GROL Marine Electronics and Radar Systems

Question 1

What is the primary frequency band used by marine radar systems?

Accepted Answer

X-band (9–10 GHz)

Answer

Marine radar primarily operates in the X-band (around 9–10 GHz) because this frequency provides good target resolution and is reflected well by water surfaces and vessels.

Question 2

What does ARPA stand for in marine radar terminology?

Accepted Answer

Automatic Radar Plotting Aid

Answer

ARPA stands for Automatic Radar Plotting Aid, a system that tracks targets and calculates their course, speed, and closest point of approach (CPA).

Question 3

Which type of radar display shows the ship's own position at the center with north always pointing up?

Accepted Answer

True motion display

Answer

A true motion display moves the own-ship symbol across the screen to reflect actual movement, with north fixed at the top and sea clutter stationary.

Question 4

What is the purpose of the sea clutter (STC) control on a marine radar?

Accepted Answer

To reduce echoes caused by wave returns close to the ship

Answer

The Sensitivity Time Control (STC) reduces the gain of the receiver for close-range returns, suppressing strong echoes from nearby sea waves that would otherwise obscure targets.

Question 5

What is the typical pulse repetition frequency (PRF) for a short-range marine radar setting?

Accepted Answer

1,500–4,000 Hz

Answer

Short-range marine radar settings use higher PRFs, typically 1,500–4,000 pulses per second, allowing more frequent updates at short ranges while keeping pulse width narrow.

(GROL) General Radiotelephone Operator License Practice Test

(GROL) General Radiotelephone Operator License Practice Test

GROL Marine Electronics and Radar Systems