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Model
8902A
Operation
Sensitivity
vs.
Selectivity; Special Function 4
Tuned R F level measurements can be made with
one of
two internal detectors:
a
narrow-band,
tracking IF synchronous detector (4.0 SPCL) or a wider-band IF average detector
(4.4
SPCL).
The
IF synchronous detector is more sensitive (it measures to
-
127 dBm) than the average detector (it
measures to
-
113
dBm). Although the IF synchronous detector can track a drifting input signal over
a
A5 kHz range, it is less tolerant of signal drift and residual FM than the IF average detector. When
measuring noisy signals, use the IF average detector (4.4 SPCL). The I F synchronous detector (4.0
SPCL)
is automatically selected
on
power-up.
If the signal drifts too much even for the IF average detector, use track mode tuning with this detector
(not available with the IF synchronous detector). Refer to
Comments,
"Special Function
32.9;
Tuned
R F Level Measurements Using Track Mode Tuning" o n page 3-105.
Storing Calibration Factors for the Tuned RF Level Measurement
Calibration at every frequency of interest is time consuming.
So,
when making repetitive Tuned
RF Level measurements at many different frequencies, use the Store/Recall function to recall the
calibration factor for each frequency of interest. Eight storage registers are available. If more than
eight frequencies are to be measured, use Special Functions
38
and
39
to display and enter the
calibration factors for each frequency
of
interest.
A
procedure below explains how to use these
special fbnctions.
PROCEDURE
The following procedures are provided in this Procediire section:
1.
Calibration for Absolute Measurements
a. Using a Sensor Module3: Calibrating a Tuned R F Level Measurement.
b. Using a Power Sensor: Calibrating a Tuned R F Level Measurement.
2. Calibration for Relative Measurements.
3.
Using Special Function 4 To Select the IF Detector.
4.
Using Special Functions
38
and
39
to Display and Enter Tuned R F Level Calibration Factors.
a. Special Function
38;
Display Tuned R F Level Calibration Factors.
b. Special Function
39;
Enter Tuned RF Level Calibration Factors.
c. Considerations When Using Special Functions
38.
CALIBRATION FOR ABSOLUTE MEASUREMENTS
Before attempting one of these procedures, be sure that I ) the R F Power measurement is calibrated,
2) the input signal is within the range required by the power sensor but not greater than 0 dBm
(for example, 0 to -20 dBm for the HP
11722A).
and 3) the Measuring Receiver is properly tuned.
The following procedures enable the Measuring Receiver to obtain its calibration factors for the
frequency being measured.
Two procedures are provided. If a sensor module is used, use the first procedure. If a power sensor
only is used, use the second procedure.
A
sensor module contains
a
power scnsor
path and a
through
path
for RF
measurements
as
well
as
an RF
switch
to switch
between
the
two paths.
The
Mcasuring Reccivcr controls
the
switching
of the
input signal depending on
the
measurement
selcctcd. Examplcs
of
sensor
modules
arc
Ihc
HP 1
1722A
and
the
HP
1
1792A.
3-96
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