Refer to Measure Sweep Overview for an explanation of system sweep and the functioning of the sweep components. "Sweeping" detects many problems. Used efficiently, a sweep system can detect "suckouts" (sudden drops in frequency response) and other narrow frequency response irregularities.

FORWARD SWEEP
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Forward sweep uses a headend transceiver to measure carrier levels and, when necessary, to inject short sweep pulses. When stable carriers are present, they can be referenced to create a sweep response without injecting any sweep pulses. This minimizes any subscriber interference as a result of sweep testing.

In Forward Sweep the headend transceiver communicates with the field DSAM by telemetry transmitted on a forward frequency. The telemetry provides the sweep level results, as measured in the headend, downstream to the DSAM which compares the results to the local sweep results. The final display is the difference of the two measurements resulting in a delta graph. A reference file is captured typically at the node amp output before moving to the next amp. The following sweeps use the reference file to null out any differences that could not be corrected at the node. The ideal sweep results at the output of each amp will be a flat response graph centered at 0 dB delta reference, assuming the goal is zero gain across the entire distribution network.