IMPORTANT!
Attenuation is normally a coupled function and is automatically
adjusted when the reference level changes. The reference level does not
change however, when the attenuator changes. The attenuator should be ad-
justed so that the maximum signal amplitude at the input mixer is –25 dBm or
less. For example, if the reference level is + 20 dBm, the attenuation should be
50 dB for an input signal of –25 dBm at the mixer (+20 – 45 = –25). This pre-
vents signal compression. The nominal gain of the preamplifier is +25 dB,
therefore always select attenuation values so that the input to the preamp does
not exceed –50 dBm.
NOTE: It is best to begin all measurements in AUTO attenuation mode.
Preamplifier
The S332D includes a built-in preamplifier which provides the S332D with an additional 20
dB of sensitivity. The preamplifier is a broadband preamplifier and thus the use of discrete
filters should be considered when using it. Four different bandpass filters have been added
to the list of optional accessories to accommodate this need (see Table 1-1, Optional Acces-
sories). This chapter provides an overview of preamplifier operation. A measurement exam-
ple is included.
Preamplifier Operation
To turn the preamplifier on or off:
Step 1.
Reset the S332D to the factory default settings for the current mode by pressing
the
RECALL SETUP
key on the data keypad. When the key is pressed, a Re-
call Setup selection box appears on the display. Select setup location 0 <De-
fault> to recall the factory preset state for the currently selected mode.
Step 2.
Press the
AMPLITUDE
function hard key.
Step 3.
Select the
Atten/Preamp
soft key, then the
Preamp Control Manual
softkey. Press
the
Preamp On/Off
soft key to turn the preamplifier on or off. When the
preamplifier is on, the word
AMP
will be displayed on the left side of the dis-
play.
NOTES: The preamplifier is a broadband amplifier. It can become saturated by
a signal outside of the defined frequency span.
The dynamic attenuation feature will automatically activate the preamplifier
when the S332D detects that the input signal level is below a certain level. This
condition could result in the preamplifier being automatically turned back on
even after it has been manually turned off.
When dynamic attenuation is on, Atten=Dynamic appears to the left of the dis-
play.
5-3
Chapter 5 Spectrum Analyzer Measurements