CMRT Power Systems & Interference Mitigation 1

Question 1

What is the typical magnetron anode voltage used in a commercial marine radar transmitter?

Accepted Answer

Several kilovolts DC (typically 2–25 kV depending on power class)

Answer

Marine radar magnetrons require several kilovolts of DC anode voltage (commonly 2–25 kV) to produce the high-power microwave pulses needed for long-range target detection.

Question 2

What is the purpose of STC (Sensitivity Time Control) in a marine radar receiver?

Accepted Answer

To reduce receiver gain for close-range returns immediately after each transmitted pulse, suppressing sea clutter near the vessel

Answer

STC automatically reduces receiver sensitivity for a brief period after each pulse transmission, attenuating the strong close-range sea clutter that would otherwise obscure nearby targets.

Question 3

What component in a radar power supply converts the AC mains supply to the high-voltage DC required by the magnetron?

Accepted Answer

A high-voltage transformer and rectifier assembly

Answer

A high-voltage transformer steps up the AC mains voltage, which is then rectified and filtered to produce the stable high-voltage DC needed to drive the magnetron.

Question 4

What effect do significant voltage fluctuations on the ship's supply bus have on radar performance?

Accepted Answer

They can cause erratic magnetron frequency, reduced output power, and false triggering of the modulator

Answer

Supply voltage variations can destabilize the magnetron's operating point, leading to frequency drift, reduced transmitted power, and unreliable pulse timing.

Question 5

What is the typical duty cycle of a marine radar transmitter operating in standard pulse mode?

Accepted Answer

Less than 0.1% — very short pulses relative to the pulse repetition interval

Answer

Marine radars transmit extremely short pulses with long listening periods between them, resulting in a duty cycle well below 0.1%, which limits average radiated power while maintaining high peak power.

(CMRT) Certified Marine Radar Technician Practice Test

(CMRT) Certified Marine Radar Technician Practice Test

CMRT Power Systems & Interference Mitigation 1