Acterna SPM-32A, Operating Manual

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4.2 Operation and features SPM-32A ... SPM-36A
4.2.5.2 Level difference (ABS-REF),
reference level (REF)
The level difference (ABS-REF) is the difference between
the measured absolute level and a reference level (REF).
The reference level can be entered as a constant. It is also
possible to store a result and use it as the reference level. If
the level mode is changed (dB/dBm) or the input impedance
is changed, the reference level is not adjusted accordingly.
The level difference can be measured when the following
key is pressed:
The reference level is shown in line D of the display.
Level difference (dB) = [measured absolute level (dB/dBm)]
- [stored reference level (dB/dBm)].
ABS-
REF
Example
:
Measured level
-16.3 dBm (ABS)
- Ref. level -26.0 dBm (REF)
Level difference + 9.7 dB (ABS-REF)