Chapter 2 69
Instrument Functions: A - L
BW/Avg
Instrument Functions: A - L
2.3 BW/Avg
Activates the resolution bandwidth function, and displays the menu keys that control both
the bandwidth and averaging functions.
2.3.1 Res BW
Enables you to select the 3.01 dB resolution bandwidth (RBW) of the analyzer in 10% steps
from 1 Hz to 3 MHz, plus bandwidths of 4, 5, 6, or 8 MHz.
If an unavailable bandwidth is entered with the numeric keypad, the closest available
bandwidth is selected.
Sweep time is coupled to RBW. As the RBW changes, the sweep time (if set to
Auto) is
changed to maintain amplitude calibration.
Video bandwidth (VBW) is coupled to RBW. As the resolution bandwidth changes, the
video bandwidth (if set to
Auto) changes to maintain the ratio set by VBW/RBW.
When Res BW is set to
Auto, resolution bandwidth is autocoupled to span, except when
using the CISPR and MIL detectors (Quasi Peak, EMI Average EMI Peak and MIL Peak).
For these detectors, Auto RBW coupling is to the center frequency. The ratio of span to
RBW is set by
Span/RBW (described on page 78). The factory default for this ratio is
approximately 106:1 when auto coupled. When Res BW is set to
Man, bandwidths are
entered by the user, and these bandwidths are used regardless of other analyzer settings.
NOTE In zero span, the auto/manual function of this key is not applicable. When Res
BW (Auto)
is selected in non-zero span, any changes to Res BW while in zero
span will revert to the Auto value when you return to non-zero span. When
Res BW (Man) is selected in non-zero span, any changes to Res BW while in
zero span will be maintained when you return to non-zero span.
NOTE When the Quasi Peak or one of the EMI detectors are selected, the resolution
bandwidths available are restricted to the set defined in Table 2-2, “CISPR
Bandwidths with RBW Set to Auto,” on page 85. When the MIL Peak detector
is selected, the resolution bandwidths available are restricted to the set
defined in Table 2-4, “MIL Specifications for Bandwidth vs. Frequency with
RBW Set to Auto,” on page 88.
A # mark appears next to Res BW on the bottom of the analyzer display when it is not
coupled. To couple the resolution bandwidth, press
Res BW (Auto) or Auto All .
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