Operating instructions

University of Saskatchewan
Electrical Engineering Laboratory Equipment Manual
resolve two peaks in the display. However, if the frequency of the second signal
generator were reduced to 1.2 kHz, then you would only see one peak on the display—
the spectrum analyzer wouldn’t be able to resolve the two signals into two distinct
peaks.
The sweep time of the HP 3580A may be set by the operator, but newer
spectrum analyzers do not have this adjustment, as the sweep time is automatically set.
As you can well imagine, sweeping a BPF in frequency while keeping its bandwidth
constant is a difficult endeavour. However, the most important aspect is the signal
power (energy) that gets passed by the BPF. If the RBW is set very narrow, then not
much signal energy makes it through the BPF per unit time. Thus the displayed
spectrum may not be a true representation of the actual spectrum if the sweep time is
set too fast. There is, therefore, a tradeoff between the RBW setting and the sweep
time. A narrow RBW is desirable because it reveals the most detail in the spectrum, but
in order to maintain an accurate display, the sweep speed must be reduced to a very
slow value. Thus, in spectrum analysis, we frequently set the RBW only as narrow as is
necessary in order to facilitate a sweep speed that is as fast as possible.
HP 3580A Spectrum Analyzer
The controls on the front panel of the HP 3580A are well laid out and easy to
find. The sweep controls (highlighted above) govern the frequency sweep
characteristics of the instrument.
hp
LIN
10 dB
1 dB
LINEAR
LOG
dB / DIV
ON (AC)
OFF
ON (BAT)
CHARGE
CLEAR WRITE
BLANK STORE
STORE
(REDUCED RESOLUTION)
dBv / LIN
dBm
600

CAL
10 kHz
NORMAL
CAL
MAX
INPUT
OVERLOAD
UNCAL
VERNIER
(CASE GROUND)
ADJUST
DISPLAY SMOOTHING
MANUAL VERNIER
MAN STR CTR
OFF
INTENSITY
ADAPTIVE SWEEP
FOCUS
DISPLAY POWER AMPLITUDE MODE AMPLITUDE REF LEVEL INPUT SENSITIVITY INPUT
RESOLUTION BANDWIDTH FREQ SPAN/DIV
SWEEP TIME/DIV SWEEP MODE
FREQUENCY
3580A SPECTRUM ANALYZER
HEWLETT PACKARD