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Operation Overview
3-16
OPERATION WITH BANDWIDTH/SWEEP TIME COUPLING:
To begin a measurement, the operator normally presses
. This ac-
couPLEa
RES
TO SPAN
sw HOLD
tivates
r�]
, deactivates
0
and sets the Frequency Span to 40 MHz. It
a lso sets the RBW and VBW to 30 kHz and the Sweep Time to 0 . 2 seconds.
These are the preferred or " optimum" settings for the full 40 MHz Span.
After connecting the signal source, the operator adjusts the Center Frequency
and Frequency Span (or Start and Stop Frequencies) to display the signals of in
terest. During this process, the Resolution Bandwidth is automatically narrow
ed as a function of Frequency Span to maintain a good aspect ratio and provide
an appropriate amount of frequency resolution . Since the Video Bandwidth is
coupled to Resolution Bandwidth, it changes along with the RBW to maintain
proportional display smoothing. The Sweep Time is mathematically calculated
according to the RBW, VBW and Frequency Span, and is automatically ad
justed to maintain the maximum-calibrated sweep rate or the analyzer's
minimum Sweep Time of 0 . 2 seconds.
Once the frequency parameters have been set, the operator can freely adjust
the RBW and/or VBW settings to obtain the required resolution, sensitivity and
display smoothing. With optimized Sweep Time coupling, the Sweep Time is
automatically adjusted to maintain the optimum sweep rate. If desired, the
Sweep Time can be increased from the optimum setting to minimize the effects
of sweep dynamics; or it can be decreased ( at the cost of calibration) to quickly
survey the spectrum of interest.
The coupling system is very flexible and will allow the operator to select any
available RBW, VBW, Sweep Time combination . It will then remember and,
where possible, maintain the relationships established by the operator. The op
timum settings can be restored by pressing the
key.
For applications such as horizontal expansion, it is desirable to maintain a
specific RBW setting and adjust the Frequency Span, while allowing the coupl
ing system to automatically adjust the Sweep Time. This can be done by ac-
"ES
tivating the
sw HOLD
function .
[DJ
If the operator does not wish to use the coupling system, it can be completely
COIRED
disabled by deactivating the
function . (The UNCAL indicator and PRESET
COUPLED
key are operative whether or not the
function is activated . )
Model 3585A