I definitely don't have enough experience with rf design to get anywhere near what I need so I'm here asking Y'all once again. What I need to build is a system that sends out a radio signal from device one and starts a stopwatch. When that signal is received by device two, it sends a complementary signal back to device one that when received stops the stopwatch. This way I can use time-of-flight analysis to determine the distance between the two devices. I can't use LIDAR because the line of sight is not guaranteed, and I haven't found an ultrasonic system that can handle the distance requirement (150m). I do comprehend that the MCU would need at least a 1ghz to get within a foot of accuracy which is all I need. But if anyone could even recommend an MCU or system that could meet that I can probably work out the rest. THANK YOU ALL SO MUCH!!