Anrtisu Cell Master MT8212B, User Manual, Page: 164 / 294

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 MT8212B includes a built-in preamplifier which provides the MT8212B with an addi-
tional 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
Accessories). This chapter provides an overview of preamplifier operation. A measurement
example is included.
Preamplifier Operation
To turn the preamplifier on or off:
Step 1. Reset the MT8212B to the factory default settings for the current mode by press-
ing the RECALL SETUP key on the data keypad. When the key is pressed, a
Recall 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
soft key.
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 MT8212B 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