R&S FSH3 Setting the Span
Setting the Span
The span is the frequency range centered on the center frequency which a spectrum analyzer displays
on the screen. What span should be selected for a particular measurement depends on the signal to be
investigated. A rule of thumb is that it should be at least twice the bandwidth occupied by the signal.
For frequency domain measurement the R&S FSH3 has a minimum span of 10 kHz and a maximum
span of 3 GHz. Using the span 0 Hz measurement is performed in time domain.
Operating sequence:
¾ Press the SPAN key.
When the SPAN key is pressed, the R&S FSH3
automatically activates the MANUAL SPAN softkey
and indicates the current value so that a new span can
be entered immediately. If another function in the
SPAN menu has been used beforehand, press the
MANUAL SPAN softkey to enter the span.
¾ Enter a new span with the number keys and
terminate the entry with the appropriate unit (GHz,
MHz, kHz or Hz), or
¾ Change the span with the rotary knob or the cursor
keys. The span is set immediately after the change
is made.
¾ The value entry box can be cleared from the
screen with the CANCEL key.
Use the FULL SPAN softkey to select the full span from 0 Hz to 3 GHz with a single keystroke.
¾ Press the FULL SPAN key.
The R&S FSH3 displays the spectrum over the full span which extends to 3 GHz
(CENTER = 1.5 GHz, SPAN = 3 GHz).
The R&S FSH3 has a LAST SPAN softkey so that you can toggle between span settings with just one
keystroke.
¾ Press the LAST SPAN key.
The span that was set immediately before the current span is restored.
The ZERO SPAN softkey sets the span to 0 Hz. The R&S FSH3 measures the signal level only at the
center frequency that has been set. As a spectrum cannot be displayed when measurements are made
at a single frequency, the display mode switches to the time domain. The x axis of the measurement
diagram becomes the time axis and level is plotted against time. The display always starts at 0 s and
stops after the sweep time that has been set (set with the SWEEP key, see also "Setting the Sweep").
1145.5973.12 4.5 E-6
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