I've worked with RF most of my life, so I have a question or two . . .

What transmitter and receiver hardware are you using?

On what radio frequency?

Since you mention a period of 4 ms, I assume you will modulate your carrier at 250 Hz, yes?

Are you using FSK (frequency-shift keying)?

What is the shortest time period (the smallest window) in which two of the 3 us pulses are likely to occur? Is it likely to be as short as 4 ms?

Is the entire information to be transmitted simply the fact that the 3 us pulse has occurred?

Russ