HP ESA-L1500A, User'S And Calibration Manual

Page: 73 / 326

72 Chapter 4
Front-Panel Key Reference
BW/Avg
BW/Avg
The
BW/Avg
key activates the resolution bandwidth function and
accesses the softkeys that control the bandwidth functions:
Resolution
BW Auto Man
,
Video BW Auto Man
, and
VBW/RBW Ratio
. It also accesses
Video Average On Off
.
Resolution BW
Auto Man
changes the spectrum analyzers 3 dB resolution bandwidth from 1 kHz
to 3 MHz in a 1, 3, 10 sequence using the step keys, and to 5 MHz using
the numeric keypad. As the resolution bandwidth is decreased, the
sweep time is increased to maintain amplitude calibration. Resolution
bandwidth is also related to span. As span is decreased, the resolution
bandwidth is decreased. A “#” mark appears next to
Res BW
on the
display when it is not coupled. To recouple the resolution bandwidth,
press
Resolution BW Auto Man
so that Auto is underlined (or press
Auto
Couple
). The resolution bandwidth can be changed using the step keys,
the knob, or the numeric keypad. Key Access:
BW/Avg
Video BW Auto
Man
changes the spectrum analyzer post-detection filter from 1 Hz to 3 MHz
in a 1, 3, 10 sequence using the step keys.
As the video bandwidth is decreased, the sweep time is increased to
maintain amplitude calibration. A “#” mark appears next to VBW on
the bottom of the spectrum analyzer display when it is not coupled. To
couple the video bandwidth, press
Video BW Auto Man
so that Auto is
underlined (or press
Auto Couple
).
NOTE
Auto-coupling the video bandwidth function also resets the VBW/RBW
ratio to 0.300 X. If you want to auto-couple the video bandwidth to a
nonstandard ratio, you must set the video bandwidth to auto-couple
before setting the video-bandwidth/resolution-bandwidth ratio.
The video bandwidth can be changed by using the step keys, knob, or
numeric keypad. Key Access:
BW/Avg
VBW/RBW Ratio
selects the ratio between the video and resolution bandwidths. If signal
responses near the noise level are visually masked by the noise, the
ratio can be set to less than 1 to lower the noise. The knob and step keys
change the ratio in a 1, 3, 10 sequence. Pressing
Preset
and
Auto Couple
sets the ratio to 0.300 X. The ratio can be changed using the step keys
or the knob. Front-Panel Key Access:
BW/Avg
Video Average On
Off
initiates a digital averaging routine that averages displayed signals
and noise by averaging a number of successive sweeps. The number of
sweeps (N) to average is the number that is set by this function. This
function does not affect the sweep time, bandwidth, or other analog
characteristics of the spectrum analyzer. Annotation on the left side of
the display indicates the current number of sweeps averaged. The