The minimum range is equal to half of which quantity?

• A. Pulse width
• B. Pulse repetition rate
• C. Receiver gain
• D. STC

Answer: (A)

Minimum range is set by how long the transmitted pulse lasts. A target at range R produces an echo that returns after 2R/c seconds, and you can only recognize that echo once the pulse has finished. If the pulse lasts T_p seconds, then the smallest range you can distinguish satisfies 2R/c = T_p, giving Rmin = c T_p / 2. In other words, the minimum range is half the distance the pulse travels during its own duration. Shorter pulses shrink the minimum range. Pulse repetition rate affects the maximum unambiguous range, while receiver gain and STC influence sensitivity and handling of strong echoes but do not determine the minimum range.