The Spectrum Application
R&S
®
FPC
100User Manual 1178.4130.02 ─ 07
3. Enter the reference level.
When you change the reference level while a trace is already displayed, the
R&S FPC adjusts the position of the trace.
The current reference level is indicated in the status bar. A blue dot in front of the
"Ref:" label indicates a reference level offset is active.
Defining a reference offset
The reference level offset is an arithmetic level offset. It shifts the measured levels by a
certain amount and changes the scale of the y-axis accordingly.
Such an offset is useful, for example, if you insert an external attenuator or amplifier
between DUT and RF input. The R&S FPC automatically takes the loss or gain into
account when the level is displayed - no manual calculations are necessary. A loss
introduced at the RF input must be entered as a positive number, a gain as a negative
number.
Note, however, that the internal reference level (used to adjust the hardware to the
expected signal) ignores the reference offset. Thus, it is important to keep in mind the
actual power level that the R&S FPC must handle. Do not rely on the displayed refer-
ence level (internal reference level = displayed reference level - offset).
1. Press the "Ampt" key to open the amplitude menu.
2. Select the "Range / Ref Position" menu item to open the display range menu.
3. Select the "Reference Offset" menu item.
The R&S FPC opens an input field to define the reference offset.
4. Enter the required reference level offset.
The R&S FPC adjusts the position of the trace and scale of the y-axis as you apply
the changes.
A blue dot in front of the "Ref:" label in the status bar indicates that a level offset is
active.
Figure 14-7: Indicator of a reference level offset
Defining the position of the reference level
By default, the reference level the grid line at the top of the diagram represents the ref-
erence level. The current reference level position is indicated by a small grey triangle
on the y-axis.
Figure 14-8: Indicator of reference level position
Amplitude Configuration
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