How to Measure Power Power Measurement
Agilent 8163A/B, 8164A/B & 8166A/B Mainframes, Sixth Edition 89
When you press the [Dsp->Ref] softkey, the absolute power level, the 
power value in dBm or Watts, is stored as the reference, that is:
REF = P
measured
Where,
REF  is the reference, and
P
measured
  is the absolute power level (see “How to Set the Calibration Offset” 
on page 87).
The [Dsp->Ref] softkey is displayed if you move to a power measurement 
channel.
How to Reference Another Power Measurement Channel
You can use the reference mode, [Ref Mode], to reference another Power 
Meter’s current power level. If you choose this mode, the reference of the 
channel continuously updates to the current power value measured by the 
other channel.  
The following equations describe how the power in dB is calculated if you 
reference another channel:
P
display
(dB) = P
measuredA
 (dBm) − P
measuredB
 (dBm) − REF(dB)
or 
Where:
P
display
  is the displayed relative power,
P
measuredA
  is the absolute power level (see “How to Set the Calibration Offset” 
on page 87) measured by the current Power Meter, and
P
measuredB
  is the absolute power level (see “How to Set the Calibration Offset” 
on page 87) measured by the Power Meter you choose to reference, and
REF  is the reference level in decibels (dB).
You can only set the reference level, REF, in decibels (dB) when you 
reference Power Meter’s current power level. This reference level is stored 
in separate memory than the absolute reference level.
NOTE