R&S FSH Spectrum Analyzer Mode
Configuring Spectrum Measurements
Operating Manual 1173.6275.12 - 30 121
3.2.6.8 Using Marker Functions
In addition to the frequency and level readout, the R&S FSH provides several, more
complex, marker functions in spectrum analyzer mode.
Deactivating marker functions
Selecting a marker function again while it is still active turns that marker function off.
Measuring the Noise Power Density
The marker noise function calculates the noise power density at the marker position in
dBm/Hz. The R&S FSH includes several variables in the calculation of the noise power
density, including the trace pixel values, the resolution bandwidth, the detector and the
level display mode (absolute or relative). To stabilize the noise power display, the
R&S FSH uses the pixel the marker is on and four pixels to the right and four pixels to
the left of the marker pixel.
Noise power density can provide useful information when you are measuring noise or
digitally modulated signals. However, you will get valid results only if the spectrum in
the vicinity of the marker has a flat frequency response. When measuring the noise
power density on discrete signals, results are not valid.
► Press the MARKER key.
► Press the "Marker Function"
softkey.
► Select the "Noise" menu item.
The R&S FSH shows the level at
the marker frequency in dBm/Hz. If
you are using a delta marker for
the measurement, the results have
the unit dBc/Hz with marker 1
being the reference.
Measuring the Frequency
The R&S FSH provides a frequency counter. The frequency counter accurately
measures the frequency at the marker position.
When calculating the horizontal position of the marker, the R&S FSH includes the
current span, center frequency and the frequency of the pixel the marker is on. As the
trace only has 631 pixels, the marker position is just an approximation, especially if the
span is very wide.
With the frequency counter, however, you can get a more accurate result of the
horizontal marker position. If the frequency counter is active, the R&S FSH stops the
measurement at the marker position for a short time and measures the frequency
using the internal reference frequency.
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