HP 3585A Service Manual page 48

Operation Overview
OPERATION WITH BANDWIDTH/SWEEP TIME COUPLING:
To beg i n a measurement, the operator normally presses ���J: . This ac-
tivates
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 connecti ng the signal source, the operator adjusts the Center Frequency
and Freq uency Span (or Start and Stop Freq uencies) to display the signals of in­
terest. During this process, the Resolution Bandwidth is automatically narrow­
ed as a function of Freq uency Span to maintain a good aspect ratio and provide
an appropriate amount of frequency resolution . Since the Video Bandwidth is
coupled to Resolutio n Bandwidth, it changes along with the RBW to maintain
proportional d isplay smoothing. The Sweep Time is mathematica lly calculated
according to the RBW, VBW and Frequency Span, and is automatically ad­
justed to maintai n the maximum-cali brated sweep rate or the a nalyzer'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 req uired 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 mini mize the effects
of sweep dynamics; or it can be decreased ( at the cost of calibration) to quickly
su rvey the spectrum of interest.
The coupling system is very flexible and will a l low 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
For a ppl ications such as horizontal expansion, it is desirable to maintai n a
specific RBW setting and adjust the Freq uency Span, while allowing the coupl­
ing system to automatically adjust the Sweep Time. This can be done by ac-
tivating the
If the operator does not wish to use the coupling system, it can be completely
disa bled by deactivating the
key are operative whether or not the
3-16
r�]
RES
couPLEa
sw HOLD
TO SPAN
, deactivates
0
" E S
sw HOLD function .
[DJ
COIRED
and sets the Frequency Span to 40 M H z . It
key.
function . (The U N CA L ind icator and PRESET
COUPLED
function is activated . )
Model 3585A