Measurements and Results
R&S
®
FSW
136
User Manual 1173.9411.02 ─ 43
Increasing the Frequency Resolution
The frequency resolution of the marker is determined by the resolution of the trace. A
trace consists of 1001 trace points, i.e. if the frequency span is 1
MHz, each trace point
represents a span of approximately 1
kHz. This corresponds to a maximum uncertainty
of +/-
0.5
kHz.
You can increase the resolution of the trace by reducing the frequency span.
Reducing the frequency span to 10 kHz
► Reduce the frequency span to
10
kHz
.
The resolution of the trace is now approximately 10
Hz (10
kHz span / 1001 trace
points), thus, the precision of the marker frequency display increases to approxi-
mately
±
5
Hz.
Setting the Reference Level
The reference level is the level at the upper limit of the diagram. To achieve the widest
dynamic range possible for a spectrum measurement, use the entire level span of the
R&S
FSW. In other words, the highest level that occurs in the signal should be located
at the top edge of the diagram ( = reference level) or immediately below it.
Low Reference Levels
If the selected reference level is lower than the highest signal that occurs in the spec-
trum, the signal path in the R&S
FSW is overloaded.
In this case, the message "IFOVL" is displayed in the error message field.
In the presettings, the value of the reference level is 0
dBm. If the input signal is
-30
dBm, the reference level can be reduced by 30
dB without causing the signal path
to be overloaded.
Reducing the reference level by 30 dB
► Set the reference level to
-30
dBm
.
The maximum of the trace is near the maximum of the measurement diagram. The
increase in the displayed noise is not substantial. Thus, the distance between the
signal maximum and the noise display (=dynamic range) has increased.
Setting the reference level with the help of a marker
You can also use a marker to shift the maximum value of the trace directly to the top
edge of the diagram. If the marker is located at the maximum level of the trace (as in
this example), the reference level can be moved to the marker level as follows:
1. Press the [MKR ->] key.
2. Select "Ref Lvl = Mkr Lvl".
The reference level is set to the current marker level.
Basic Measurements
