Specifications

R&S FSH Setting the Sweep
1145.5973.12 4.15 E-10
Setting the Sweep
If the span is > 0, the sweep time is the time the spectrum analyzer takes to traverse the displayed span
to measure the spectrum. Certain boundary conditions must be met if a spurious spectrum is not to be
displayed.
One boundary condition is the resolution bandwidth. If the resolution filter is to settle, the dwell time
within the filter bandwidth must have the right value. If the sweep time is too short, the resolution filter
does not settle and the displayed level is too low (see also “Setting the Bandwidth”).
The second boundary condition is the selected span. If the span is increased, the sweep time must be
increased proportionally.
The R&S FSH provides automatic sweep time coupling to help users set the sweep time by coupling it
to the resolution bandwidth and span that have been set. When automatic coupling (AUTO SWEEP
TIME) is selected, it always sets the shortest sweep time possible to ensure that sine signals in the
spectrum are displayed correctly. When you quit the auto sweep time mode (MANUAL SWPTIME is
activated instead), a small, red circle is placed in front of the SWT readout to indicate that the
uncoupled mode has been selected. If the sweep time is so short that level errors occur, the R&S FSH
informs the user by displaying a red circle on the right-hand side of the measurement diagram.
The R&S FSH requires a minimum sweep time of 20 ms per 600 MHz of span. If a larger span is set,
the R&S FSH automatically adapts the minimum sweep time in the coupled mode. For the maximum
span of 3 GHz in the R&S FSH3, a minimum sweep time of 100 ms is required. Analagously, for the
maximum span of 6 GHz in the R&S FSH6, a minimum sweep time of 200 ms is required.
If the span = 0 Hz, the R&S FSH displays video voltage versus time instead of a spectrum. The x axis
of the measurement diagram becomes the time axis, starting at 0 s and ending at the sweep time you
have selected.
The minimum sweep time when the span = 0 Hz is 1 ms, the maximum 1000 s.
Sweep time
¾ Press the SWEEP key.
The softkey menu for entering sweep parameters
opens. If the default settings have been selected,
automatic coupling (AUTO SWPTIME) is set. In this
mode, the sweep time is coupled to the resolution
bandwidth, the video bandwidth and the span.
¾ To enter the sweep time, press the MANUAL
SWPTIME softkey.
The SWEEP value entry box opens and indicates the
current sweep time setting.
¾ Enter a new sweep time with the number keys and
terminate the entry with one of the unit keys, or
¾ Change the sweep time with the rotary knob or the
cursor keys.
Whenever a change is made, the sweep time is immediately set to its new value. The value entry box is
closed by pressing the ENTER key. The sweep time that has been set is displayed in the top right-hand
corner of the screen in the SWT readout box.