RADAR Principles
RADAR Principles
Distance and Time
A radio wave will travel a distance of three nautical miles in:
A radio wave will travel a distance of three nautical miles in approximately 18.51 microseconds.
The speed of light in a vacuum is approximately 299,792 kilometers per second (km/s) or 186,282 miles per second (mi/s). To convert this speed to nautical miles per microsecond, we use the following calculation:
Speed of light in nautical miles per microsecond = (Speed of light in miles per second) / (1.15078 nautical miles per mile) / (1,000,000 microseconds per second)
Speed of light in nautical miles per microsecond ≈ 186,282 mi/s / 1.15078 nm/mi / 1,000,000 µs/s ≈ 162.58 nm/µs
Now, to find the time it takes for a radio wave to travel a distance of three nautical miles, we use the formula:
Time (in microseconds) = Distance (in nautical miles) / Speed (in nautical miles per microsecond) Time (in microseconds) = 3 nm / 162.58 nm/µs ≈ 0.01851 µs ≈ 18.51 microseconds
Mnemonic: "Nautical Time"
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Each nautical mile traveled at the speed of light (161826 miles per second), takes approx 6 microseconds (1/161282). So a round trip takes approximately 12 microseconds to see the returned RADAR response
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RADAR range is measured by the constant:
The correct answer is the only one with metric units.
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If a target is 5 miles away, how long does it take for the RADAR echo to be received back at the antenna?
To get the answer we need to use the correct speed of light in a vacuum, which is approximately 299,792,458 meters per second.
Calculate the time it takes for the RADAR echo to be received back at the antenna when the target is 5 nautical miles away.
Step 1: Convert 5 nautical miles to meters: 5 nautical miles ≈ 5 * 1852 meters per nautical mile ≈ 9260 meters
Step 2: Calculate the time: Time = 2 * (Distance / Speed) Time = 2 * (9260 meters / 299,792,458 meters per second)
Time ≈ 2 * 0.000030873 seconds
Converting this time to microseconds (since 1 second = 1,000,000 microseconds):
Time ≈ 2 * 0.000030873 seconds * 1,000,000 microseconds per second Time ≈ 61.746 microseconds
The correct answer is approximately 61.746 microseconds for the RADAR echo to be received back at the antenna when the target is 5 nautical miles away.
Mnemonic: "RoundTripTime"
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How long would it take for a RADAR pulse to travel to a target 10 nautical miles away and return to the RADAR receiver?
To calculate the time it takes for a RADAR pulse to travel to a target 10 nautical miles away and return to the RADAR receiver, we'll use the speed of light in a vacuum, which is approximately 299,792,458 meters per second.
Step 1: Convert 10 nautical miles to meters: 10 nautical miles ≈ 10 * 1852 meters per nautical mile ≈ 18,520 meters
Step 2: Calculate the time: Time = 2 * (Distance / Speed) Time = 2 * (18,520 meters / 299,792,458 meters per second)
Time ≈ 2 * 0.000061760 seconds
Converting this time to microseconds (since 1 second = 1,000,000 microseconds):
Time ≈ 2 * 0.000061760 seconds * 1,000,000 microseconds per second Time ≈ 123.52 microseconds
The correct answer is approximately 123.52 microseconds for the RADAR pulse to travel to a target 10 nautical miles away and return to the RADAR receiver.
One-word mnemonic: "RoundTripTime"
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What is the distance in nautical miles to a target if it takes 308.5 microseconds for the RADAR pulse to travel from the RADAR antenna to the target and back.
There are 1852 meters in 1 nautical mile and it takes RADAR travels 150 meters in 1 microsecond. Thus, 150 meters/microsecond divided by 1862 meters/mile = ~0.081 miles/microsecond.
Multiply the 0.081 miles/microsecond by 308.5 microseconds to get ~25 nautical miles.
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