User manual

40
Subject to change without notice
Fig. 3.7: PEAK SEARCH function
3.4 Setting of the reference level
The reference level in spectrum analyzers is always the level of
the top graticule line. In order to realize the maximum dynamic
range in spectrum measurement, the level display range of the
spectrum analyzer should be fully used. This means that the
highest level in the actual spectrum should be as close to the
top graticule line (= reference level) as possible. The maximum
value of the level display (Y axis) of the measurement display is
determined by the reference level. However, take care that the
top graticule line is not exceeded as this would cause overdrive
of the spectrum analyzer input stage.
In order to prevent overdriving the input, the input attenuators
of the spectrum analyzer are independently selectable and
linked to the reference level. If the reference level in the ampli-
tude selection menu (key AMPL
4
) is increased by 20 dB (0 to
20 dBm), the input attenuator will be automatically switched to
30dBm.Thiswillcausetherstharmonicofthesignal(marker
2) to disappear in the noisefloor.
Fig. 3.8: Setting of the reference level
3.5 Operation in the receiver mode
For the measurement of levels of a signal frequency the HMS
series offers the receiver mode. The spectrum analyzer operates
like a receiver which is tuned to a frequency and measures the
level. The menu of the measurement functions will open by
pressing the key MEAS
11
, If the soft key CF > RX is activated,
the HMS will switch to the receiver mode and measures the level
of the center frequency set. The most important settings of the
measurement parameters are directly accessible in the main
menu of the receiver mode and can be activated by pressing
the appropriate keys.
Fig. 3.9: Receiver mode with a center frequency set
In the receiver mode the same bandwidths are available as in
the analyzer mode. Additionally, the bandwidths 200 Hz, 120 kHz,
and 1 MHz (–6 dB) for emi measurements according to CISPR
are provided. These can be chosen by pressing the key BANDW
and using the knob.
The HMS series receiver mode offers peak, average, rms and
quasi-peak detectors. The detector is selected in the main menu
of the receiver mode with the soft key DETECTOR.
The measuring time is the time during which the spectrum
analyzer collects measurement results and combines them
for a result, depending on the detector selected. With the knob
the measuring time may be varied, or it can be entered directly
via the keyboard.
If the quasi-peak detector is selected, the measu-
ring time should be >100 ms in order to measure
varying or pulsed signals correctly.
Q u i c k i n t r o d u c t i o n