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Diagram
4-1.
The Measurement Ranges for the IF Synchronous
and
IF
Average Detectors
The Calibration Technigue
You may remember, that in the
TRFL
calibration procedure in
Chapter
I
you were instructed
to
adjust the input signal to specific
levels (0, -40, and -80 dBm
).
Note in Diagram
4-1
that each of the
specified levels is
within
the overlap (calibration) region between two RF
measurement ranges for the IF Synchronous detector. When you adjusted
the input signal to each of these levels the RECAL annunciator in the
display was lit and you were instructed to press the
CALIBRATE
key.
Range
I
When you pressed the
CALIBRATE
key to calibrate Range 1, the
flp
890244
measured the level of the input signal twice. Once using
its
RF Power
meter
circuitry
and once using the IF Synchronous detector and the
Range 1 arcuit configuration. By comparing the two measurements, the
HP
8902A
created a
TRFL
calibration factor for Range 1 that equated
the Range 1 measurement to the calibrated RF Power measurement. This
" L
calibration factor transferred the absolute accuracy of the RF Power
measurement to all Range
1
TRFL
measurements made at that frequency.
Remember
This double measurement technique makes it very important
that the level
of
the input signal remain stable throughout
the calibration process (while the
CALIBRATE
key is lit).
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