Instructions

Page 19
4.3 Setting the Sweep Mode, Bandwidth (RBW / VBW) & Detector
This menu group controls the sweep, the resolution bandwidth filters and the detector mode.
This enables the resolution bandwidth of the sweep filter and the subsequent video filtering to
be controlled along with sweep time (normal or fast) and the type of sweep (repeat or single). It
also provides control of the detector, and options for changing the image rejection method
(sweep mode). If option U02 is fitted, sweep triggering can also be controlled.
4.3.1 RBW / VBW
controls the resolution bandwidth of the sweep filter prior to the detector (RBW) and
of the filter that follows the detector (VBW). A narrower RBW provides greater
frequency resolution and lower noise, but increases the sweep time. A narrower
VBW similarly reduces noise but increases sweep time Creates a set of bottom-row function
keys as follows:
causes the RBW to be automatically changed to suit the frequency span. The RBW
value is displayed at the top of the screen and is preceded by the word Auto.
cancels Auto mode and creates a pop-up menu from which a specific RBW value
can be selected. The range is 300Hz to 10MHz in a 1:3:10 sequence. The selected
value is displayed at the top of the screen.
causes the VBW to be automatically changed to track the RBW value subject to the
VBW offset. The VBW value is displayed at the top of the screen and is preceded
by the word Trk.
cancels Track mode and creates a pop-up menu from which a specific VBW value
can be selected. The range is 300Hz to 10MHz in a 1:3:10 sequence. The selected
value is displayed at the top of the screen.
sets the relationship between VBW and RBW for VBW Track mode. Positive
numbers set a VBW one or more steps higher while negative numbers set it one or
more steps lower. The default is zero
4.3.2 Sweep Time (and the Sweep Progress Indicator Line)
The normal sweep time and update rate is automatically set from the Span and the RBW and is
displayed within the lower annotation area. Narrower RBW settings create longer sweep times. For
each RBW, the normal sweep time is broadly proportional to the frequency span. The sweep time
can be manually reduced at the expense of amplitude accuracy.
enables the sweep to be speeded up at the expense of level accuracy. Creates a
set of bottom-row function keys as follows:
selects the normal sweep time and ensures the highest degree of level accuracy.
The sweep time is dependent upon the span and the RBW/VBW settings and is
displayed in seconds within the lower annotation area followed by [N].
RBW/
VBW
Sweep
Time
Sweep
Control
Sweep
Mode
Detector
Type
Sweep/
BW
RBW/
VBW
RBW
Auto
RBW
Set
Sweep
Time
VBW
Track
Auto
(Norm)
Track
Offset
Set
VBW