Operation & Service Manual
Section III
Model 1805B RF Control Unit
Theory & Operation
Note that with active devices such as spectrum analyzers, no absolute accuracy device or
system is used e.g. dc substitution, thermistors etc., so that uncalibrated power measurement
values can be quite arbitrary. The calibration factor can thus be up to several dB and have
either sign. A negative sign indicates a system that is reading a level lower than actual. A
positive sign indicates a system that is reading a level higher than actual. The true level is
given by:
PA = Pm - K1dB
Where PA is the actual power, and P
m
is the power level as registered by the device or system
under test, and both are in dBm.
3-15
