How can transient signals or ingress fail to be detected when using a spectrum analyzer?

Transient signals or ingress can fail to be detected when using a spectrum analyzer primarily because they might occur between the sweeps of the analyzer. Spectrum analyzers work by taking measurements at discrete points in time, scanning the frequency range of interest. If a transient event occurs during the time the analyzer is not actively taking measurements, it can be completely missed. This particularly affects short-lived signals, such as spikes or brief disturbances, which may not persist long enough to be captured in the data collected during the sweep.

The nature of spectrum analyzers—sampling at fixed intervals rather than continuously—means that any event occurring in the gap between sweeps is not recorded, leading to an oversight of those critical transient signals. Recognizing this limitation is essential for a technician, as it underlines the importance of using appropriate measurement techniques or equipment settings that can adequately capture transient events.