Power Systems & Interference Mitigation Flashcards
6 cards from real CMRT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Power Systems & Interference Mitigation flashcards as text
What is the primary method for mitigating conducted electromagnetic interference (EMI) entering a radar system through its power supply leads?
Answer: Installing EMI filters (line filters) on the power input leads to the radar unit
EMI line filters installed on the radar's power input leads block high-frequency interference currents from the ship's supply bus from entering the radar's sensitive circuits.
What is the function of a TR (Transmit/Receive) limiter or duplexer in a marine radar?
Answer: It protects the sensitive receiver from the high-power transmitted pulse by isolating the receiver during transmission
The TR limiter automatically disconnects or severely attenuates the receiver input during each transmitted pulse, preventing the high-power transmit energy from burning out the receiver's front-end components.
What causes 'indirect' or 'false echoes' to appear on a radar display in a harbor or near large structures?
Answer: Reflection of the radar beam off the ship's own superstructure or nearby large metal objects, creating echoes that appear at incorrect bearings or ranges
False echoes are produced when the radar beam reflects off the vessel's own structure or nearby objects before reaching a target, or when the reflected path from a large metal structure creates an apparent target at a false position.
Why is a proper RF ground bond between the radar scanner mast and the ship's ground plane essential?
Answer: It reduces static charge buildup and provides a low-impedance return path that minimizes radiated EMI and protects against lightning-induced transients
A solid RF ground bond dissipates static charges, reduces EMI radiation from the mast structure, and provides a safe discharge path for lightning energy, protecting both equipment and crew.
What effect does corrosion or moisture ingress in a waveguide have on radar transmission efficiency?
Answer: It raises waveguide insertion loss, reduces transmitted power reaching the antenna, and can cause arcing at high power levels
Corroded or wet waveguide surfaces increase RF losses, reduce the power delivered to the antenna, and at high power levels, moisture or contamination can cause destructive arcing inside the waveguide.
What is the purpose of a radar test reflector or built-in test target (BITE) in a marine radar system?
Answer: To generate a known, stable radar return at a fixed range and bearing, allowing technicians to verify receiver sensitivity and display calibration without requiring an external target
A built-in test target or BITE generates an internal reference echo at a known range, enabling quick verification of radar sensitivity, timing calibration, and overall system health without dependence on external reflectors.