HP 54753A User Manual page 221

Improving Time Domain Network Measurements
Removing Measurement Errors
Figure 10-11
By adding a section of airline between the test port and the DUT, you can more clearly distinguish
primary and secondary reflections
After an adequate separation has been achieved, a time window can be selected
which does not include the undesirable secondary reflections. Figure 10-12
illustrates the removal of secondary reflections from the measurement data
using time windowing. The top waveform in Figure 10-12 contains a secondary
reflection visible at the right end of the baseline. Note that moving the time
window to the left (less delay after the trigger) removes the secondary reflection
10-15