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Hey Philip,

Good question. The Swept Spectrogram plot is showing you the RF power present at a particular frequency over the course of time. This is essentially the same information as the Real Time FFT, but it is presented in a different format and tracked over time. This plot measures all RF energy present at that frequency. Remember, spectrum analysis is layer 1, so it is looking only at raw RF energy, and is not delineating between RF energy that will or won't cause interference to 802.11 systems. That determination is your job based on the characteristics of the RF that you observe.

In the swept spectrogram plot, each horizontal line represents a sweep time, which is the interval of time it is measuring the energy. It then takes the energy measured by that sweep and matches it to a color, as indicated by your color scale settings. Different transmission types will yield unique color patterns in the spectrogram, which helps you to determine the type of device. For example, frequency hopping devices yield several dots all across the spectrum, whereas ERP-OFDM transmissions will be centered in a range of channels.

Also, I'm pretty sure the Fluke software (like the others used with the Cognio card) uses white to indicate that the power is stronger than your threshold.

I'm not yet familiar with the Fluke software, but it seems to me that the others have pretty decent help files that explain the different charts and plots.