What determines a radar's minimum range?

What determines a radar's minimum range?

• A. Transmitter power
• B. Antenna size
• C. Pulse Width (PW)
• D. Operating frequency

Answer: (C)

The minimum range is set by how long the radar is busy transmitting. While the pulse is being sent, the receiver can’t listen for echoes, so any target closer than the distance corresponding to that transmit time would have its echo buried in the transmitted pulse. The earliest detectable return occurs when the two-way travel time equals the pulse width. That gives the practical rule: minimum range ≈ (speed of light) × (pulse width) / 2. So a longer pulse width creates a larger blind zone, pushing the minimum detectable range farther out; a shorter pulse narrows that blind zone and allows detection closer to the radar. For context, transmitter power, antenna size, and operating frequency affect how far you can see overall, the beam shape, and the resolution, but they don’t set the closest range you can detect. The pulse width directly controls the earliest moment you can hear a return, making it the primary determinant of the minimum range.

The minimum range is set by how long the radar is busy transmitting. While the pulse is being sent, the receiver can’t listen for echoes, so any target closer than the distance corresponding to that transmit time would have its echo buried in the transmitted pulse. The earliest detectable return occurs when the two-way travel time equals the pulse width.

That gives the practical rule: minimum range ≈ (speed of light) × (pulse width) / 2. So a longer pulse width creates a larger blind zone, pushing the minimum detectable range farther out; a shorter pulse narrows that blind zone and allows detection closer to the radar.

For context, transmitter power, antenna size, and operating frequency affect how far you can see overall, the beam shape, and the resolution, but they don’t set the closest range you can detect. The pulse width directly controls the earliest moment you can hear a return, making it the primary determinant of the minimum range.