Rohde and Schwarz FSH-K14 - Spectrogram Measurement Option for FSH

The spectrogram measurements application allows the R&S FSH to provide a history of the spectrum. As a result, intermittent faults or variations in frequency and level versus time can be analyzed. Specific evaluations can be made by replaying recorded data and setting timelines and markers.

The R&S FSH can record up to 999 hours. The recording interval is adjustable. A short recording interval results in an increasing capturing rate, which is suitable for capturing very short intermittent signals.

Recording can be initiated manually, with predefined start and stop date and time, or triggered by events. Using R&S InstrumentView, the compressed view on the left allows fast search of ambiguous signals and the spectrum display on the right bottom can be zoomed in for further analysis.

Time and frequency markers can be added during the post-analysis stage and for documentation. This long time recording spectrogram allows unmanned recording, collection of activities over a long period and facilitates post-analysis, which is useful for interference hunting and spectrum observation.

The spectrogram result display shows the spectral density of a signal in the frequency domain and over time simultaneously.

Like other result displays, the horizontal axis represents the frequency span. The vertical axis represents time. Time in the spectrogram runs chronologically from top to bottom. Therefore, the top of the diagram is the present. A third dimension shows the amplitude for each frequency by mapping different colors to every power level. The result is therefore a two dimensional diagram.

The color the R&S FSH assigns to a power level that was measured depends on:

• The color table you have selected
• The spectrogram reference level
• The spectrogram level range

The spectrogram consists of horizontal lines, each one pixel high, that are called frames. In the default state, a frame is added to the spectrogram after each sweep. This means that the amount of data in a frame depends on the sweep time. As the spectrogram in the R&S FSH runs from top to bottom, the outdated time line(s) move down one position, so that the present frame is always on top of the diagram. Therefore, the sequence of frames is chronological.

By default, the spectrogram result display consists of two windows. The upper window shows the measured spectrum as a trace line. The lower window shows the measurement results in a spectrogram. The chronological information in the spectrogram is restricted by the internal memory of the R&S FSH. The R&S FSH stores 1024 frames or spectrums that have been measured in its memory. As the height of the display is smaller, some of the data becomes invisible after a time.

For measurements with a GPS receiver, the R&S FSH saves the GPS coordinates at which each frame / spectrum that has been measured was recorded. This feature allows you to link spectral events to a certain location when you analyze the data after the measurement sequence is finished.