Specifications

26 Chapter 3
Measuring a Low−Level Signal
Reducing Input Attenuation
Measuring a Low
−
Level Signal
Reducing Input Attenuation
The ability to measure a low-level signal is limited by internally
generated noise in the spectrum analyzer. The measurement setup can
be changed in several ways to improve the analyzer sensitivity.
The input attenuator affects the level of a signal passing through the
instrument. If a signal is very close to the noise floor, reducing input
attenuation can bring the signal out of the noise.
CAUTION Ensure that the total power of all input signals at the analyzer RF
input does not exceed +30 dBm (1 watt).
Step 1. Preset the analyzer:
Press Preset, Factory Preset (if present).
Step 2. Set the frequency of the signal source to 300 MHz. Set the source
amplitude to
−80 dBm. Connect the source RF OUTPUT to the analyzer
RF INPUT.
Step 3. Set the center frequency, span and reference level:
Press
FREQUENCY Channel, Center Freq, 300, MHz.
Press
SPAN X Scale, Span, 5, MHz.
Press
AMPLITUDE Y Scale, Ref Level, 40, −dBm.
Step 4. Move the desired peak (in this example, 300 MHz) to the center of the
display:
Press
Peak Search, Marker ➞, Mkr ➞ CF.
Step 5. Reduce the span to 1 MHz (as shown in Figure 3-1) and if necessary
re-center the peak:
Press
Span, 1, MHz.
Figure 3-1 Measuring a Low-Level Signal (ESA Display)