CMRT Radar System Fundamentals 4

Question 1

What frequency band do most commercial marine navigation radars operate in for short-range coastal navigation?

Accepted Answer

X-band (8–12 GHz, typically 9.2–9.5 GHz)

Answer

X-band radars operating at approximately 9.3–9.5 GHz are the most common marine navigation radars because their shorter wavelength provides finer resolution and suits smaller antennas.

Question 2

What is the radar horizon, and what factor primarily determines it for a given installation?

Accepted Answer

The geometric line-of-sight distance to the sea surface; primarily determined by antenna height

Answer

The radar horizon is approximately 1.22 × √(antenna height in feet) nautical miles; since radar waves travel slightly beyond the geometric horizon due to refraction, antenna height is the dominant factor.

Question 3

Which parameter directly controls the range resolution of a pulsed radar?

Accepted Answer

Pulse width (pulse duration)

Answer

Range resolution equals c × τ / 2, where τ is the pulse width; shorter pulses resolve closely spaced targets at the same bearing more precisely.

Question 4

What is 'rain clutter' and which radar control primarily suppresses it?

Accepted Answer

Returns from precipitation; suppressed by the FTC (fast time constant) or differentiation circuit

Answer

Rain clutter consists of returns from precipitation filling large areas of the display; the FTC (rain clutter) control differentiates the video signal to enhance target edges and reduce the smeared clutter background.

Question 5

In a waveguide transmission line used in marine radar, what is the primary advantage over coaxial cable at microwave frequencies?

Accepted Answer

Waveguide has lower attenuation and higher power-handling capability at microwave frequencies

Answer

At X-band frequencies, coaxial cable has unacceptably high resistive losses; rectangular waveguide carries the signal as a guided wave in air with much lower attenuation and can handle the high peak powers of radar transmitters.

(CMRT) Certified Marine Radar Technician Practice Test

(CMRT) Certified Marine Radar Technician Practice Test

CMRT Radar System Fundamentals 4