Passive Sweep - Deviser S7200 User Manual

Part II: Settings and Measurements
4-5

Passive Sweep

A stored passive sweep trace can be used as a reference. Up to 8 trace records can be saved to the S7200
for this purpose. This feature is primarily used when an active sweep reference generator is not in use at the
HE or hub. First, tap Save Ref to store a trace. Enter a filename using the data keypad and tap OK.
Once at least 1 reference trace has been saved, tap Load Ref to select the desired reference trace from
the hard drive. Then tap Start to compare it to a live trace being measured downstream. (When a saved
trace is no longer needed, tap Del Ref to erase it from the hard drive. Deleted files cannot be recovered.)
The following figure is a comparison of two traces, before and after passing through a 4-way splitter. The
amplitude shown by the marker is equal to the differentials of the two traces.
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Diagram of Passive Sweep
Like the example above, first connect the S7200 to the input
terminal of a splitter. Depending on the splitter used, we can
see that the differential value is equal to the splitter port loss
of an equal dB value. Begin a channel sweep measurement,
and store the trace measurement result as a reference. Then
switch the S7200 to the splitter's output port, and initiate a
second channel sweep.
Compare the live measurement with the saved trace.
We can see that the differential value is -7.1dB, which
indicates that the signal has been attenuated 7.1dB –
including 7dB attenuation for the splitter, connector
attenuation, and signal fluctuation.