HP 8901B Operation And Calibration Manual page 261

Operation Model 8901B
demodulator makes another FM measurement. (Both peak detectors are
used
and the average is
computed.)
The Modulation Analyzer compares the deviation (static measurements) with the demodulated
FM
(toggled measurements) and computes its accuracy error as follows:
x 100
Demodulated F M - Demodulated Residual F M
Computed F M
F M Calibration Factor (%) =
All segments of the calibration are carefully monitored. If any segment is out of limits, the calibration
is aborted and Error 08 is displayed.
r
10.1 MHz
VOLTAGE
CONTROL LED
OSCILLATOR
OUTPUT AM
BUFFER CALIBRATOR
I
OUTPUT
I
COUNTER
AN0 DISPLAY
BUFFER CONTROLLER
-
Simplified Block Diagram
of
the FM Calibrator
COMMENTS
Default Calibration Factor
If
the instrument's non-volatile memory is erased, 100.00% is used as the default calibration factor.
Updating the FM Calibration Factor
Whenever FM calibration is performed, the instrument updates the stored FM calibration factor.
Special Function Cancellation
Performing calibration cancels most Special finctions.
When Using the FM Calibrator to Calibrate Other Signal Analyzers
The modulation waveform of the FM Calibrator is a rounded trapezoid. An signal analyzer, which uses
it as a calibration standard, must have demodulation and audio processing circuits which preserve the
full
fidelity of the waveform.
Automatic FM Ranging
When used to calibrate an RF signal analyzer, Special Functions 12.1 and 12.2 set the FM deviation
range to that of 0 to
40
kHz
(Special Function 2.2). Upon exiting the FM Calibrator Special Function,
the audio ranging is not returned to automatic but remains fixed (thus leaving the SPCL light on).
Key in 2.0 SPCL to return the audio ranging to automatic.
3-158 FM Calibration