R&S FSH Spectrum Analyzer Mode
Configuring Spectrum Measurements
Operating Manual 1173.6275.12 - 30 122
The accuracy of the results therefore depends only on the accuracy of the internal
reference frequency (TCXO). The frequency counter has a resolution of 0.1 Hz and
therefore provides far more accurate results. Despite the accuracy, the measurement
is still fast (because of a special algorithm for the I/Q baseband signal).
The frequency counter only gives completely accurate readings for sine signals that
are at least 20 dB above the noise floor. If the S/N ratio is less, noise affects the
results.
► Press the MARKER key.
► Press the "Marker Function"
softkey.
► Select the "Frequency Count"
menu item
The R&S FSH displays the
counted marker. If the frequency
counter is on, the marker symbol
changes from M1 to C.
The resolution with which the frequency is measured depends on your selection.
► Select the desired frequency resolution with “Frequency Count Resolution” menu
item. “Low” has a resolution of 0.1 Hz, “High” a resolution of 0.1 mHz.
Precision Frequency Reference
For even more precise measurements with the frequency counter, you can use the
R&S FSH-Z114 Precision Frequency Reference (order no. 1304.5935.02).
For more information refer to the documentation available for the R&S FSH-Z114.
Measuring the Signal Bandwidth
The "n dB Down" marker function places two temporary markers to the left and to the
right of the reference marker and measures the bandwidth between the two temporary
markers. The function therefore is a good way to measure the bandwidth of a signal or
the bandwidth of a filter, for example. The temporary markers are represented as two
vertical lines.
The distance to the reference marker is by default 3 dB below the reference marker.
You can also adjust this value manually. Entering a positive value sets the temporary
markers below the reference marker. If it is, for any reason, not possible to calculate
the frequency spacing, dashes are displayed instead of a value.
Upon entering a negative value, the function turns into a n dB up function. You can use
a n dB up function, for example, for measurements on notch filters.
► Press the MARKER key.
► Press the "Marker Function" softkey.
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