What happens if there is not enough time between pulses for an echo to return?

• A. Returning echoes are blocked by succeeding pulses
• B. Echo is duplicated
• C. Output power decreases
• D. Receiver saturates

Answer: (A)

Not enough time between pulses means the echo from one pulse hasn’t had a chance to return before the next pulse is sent. When the next pulse goes out while the previous echo is still in flight, the receiver can’t distinguish the return from the first pulse from the energy of the new pulse. The returning echo is effectively masked or overwritten by the succeeding pulse, so it can’t be measured. This creates a range ambiguity or blind zone for targets that would return after the next pulse, because their echoes are blocked by the following transmission. The other effects listed don’t describe this overlap mechanism—the phenomenon here is the masking of the echo by the next pulse.