Round-Trip Echo Takes Two Trips - Electromagnetic Transmission Lines: Signal Propagation and Reflections Step by Step

An echo returns after two checked one-way delays. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A reflection must first reach the load

The one-way trip is 4 seconds before any load echo can start back.

t_{\text{one way}}=4\ \text{s}

The source sees the echo after two trips

Launch at 0 seconds plus a round trip of 8 seconds gives echo time 8 seconds.

0\ \text{s}+8\ \text{s}=8\ \text{s}