Subelement D: Display & Control Systems - 10 Key Topics – 10 Exam Questions— Topic 32: Fixed Range Markers
Question 8-32D6
Element 8 (RADAR)What would be the frequency of a range ring marker oscillator generating range rings at intervals of 0.25 nautical miles?
Explanation
Radar range is determined by the time it takes for an electromagnetic wave to travel from the antenna to a target and back. The round-trip time for a signal to cover one nautical mile of range is approximately 12.36 microseconds.
To generate range rings at intervals of 0.25 nautical miles, the marker oscillator must produce a pulse for every 0.25 nautical miles of round-trip travel time.
1. **Calculate the time period:**
Time Period = 0.25 nm * 12.36 µs/nm = 3.09 microseconds.
2. **Calculate the frequency:**
Frequency ($f$) is the reciprocal of the time period ($T$):
$f = 1 / T = 1 / (3.09 \times 10^{-6} \text{ s}) \approx 323,624 \text{ Hz}$
This frequency is approximately 322 kHz. Options A, C, and D correspond to different range intervals (e.g., 161 kHz for 0.5 nm intervals).
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