On Jun 6, 4:00*pm, Joseph Gwinn wrote:

A pulse radar periodically transmits pulses, listens for echoes between
the transmits, and assumes that received echoes came from the
immediately preceding transmit. *Which isn't necessarily true. *A large
reflector can have a loud-enough echo from several transmit pulses ago,
making it look like there is a nearby target. *

This is called a "second time around" echo (even if its really third
time, et al).

The standard solution is to vary the period between transmit pulses. *
Real echoes will not change their apparent range, while N-time-around
echoes will move in predictable ways.

Joe Gwinn

Another solution is to not send a pulse, and when you do not get a
pulse back, you know how long it took for the pulse to not go out and
return. This was used on the Verlort radar to track targets at 1000
miles or so.

Dan