Positively Identified Signal Measurement

Figure 7-18. The image suppress function displays only real signals

Note that both signal identification methods are used for identifying correct
frequencies only. You should not attempt to make amplitude measurements
while the signal identification function is turned on. Note that in both
Figures 7-17 and 7-18, an on-screen message alerts the user to this fact.
Once we have identified the real signal of interest, we turn off the signal
ID function and zoom in on it by reducing the span. We can then measure
the signal's amplitude and frequency. See Figure 7-19.

To make an accurate amplitude measurement, it is very important that you
first enter the calibration data for your external mixer. This data is normally
supplied by the mixer manufacturer, and is typically a table of mixer conversion
loss, in dB, at a number of frequency points across the band. This data is
entered into the ESA s amplitude correction table. This table is accessed by
pressing the [AMPLITUDE] ke y, then pressing the {More} , {Corrections} ,
{Other} and {Edit} softkeys. After entering the conversion loss values, apply
the corrections with the {Correction On} softkey. The spectrum analyzer
reference level is now calibrated for signals at the input to the external mixer.
If you have other loss or gain elements between the signal source and the
mixer, such as antennas, cables, or preamplifiers, the frequency responses of
these elements should be entered into the amplitude correction table as well.

Figure 7-19. Measurement of positively identified signal