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5-10
R f
Power
and
TRfL
4.
After the measurement has settled, press the
Blue
Shift key
and the SET REF (ZERO) key. This establishes the current
input level as the 0 dB reference for the TRFL measurement.
Note that the RECAL and UNCAL annunciators are now off.
5.
Press the LOG/LIN key if you wish to toggle between
%
and dB.
6. Begin stepping down the output level of the device under test by
increments of 10 dB or less. Press the CALIBRATE key each time the
RECAL annunciator is displayed.
7.
When you want to exit the relative measurement mode, key in 26.0
SPCL. Key in 26.1 SPCL if you wish to re-enter the relative measurement
mode and continue to use the previously established 0 dB reference.
Low-Level Signals
This procedure will enable you to measure low-level signals that can
not be adjusted to between 0 and -20 dBm (such as spurs) down to
-110 dBm; even in the presence of larger signals as close as 2 MHz.
This example also demonstrates how the Store and Recall functions
help you quickly repeat TRFL measurements at various frequencies.
1 .
Connect the HP 8902A to a signal generator and adjust its
output to
0
dBm at the frequency of the spurious
signal.
2. Manually tune the HP 8902A to the input signal and perform the
TRFL calibration. Performing TRFL calibration is actually optional.
If you do not perform the calibration, the HP 890214 will make
uncalibrated measurements with approximately f 1.5 dB accuracy.
to between 0 and -20 dBm.
3. When the TRFL calibration is complete, return the signal generator level
4.
Press the
Blue
Shift key, the STORE (7) key, and the 1 digit key. This
stores the current frequency setting and calibration data in register
1.
Repeat steps 1 through 3 at the frequency of each spur to be tested
(up to eight). (If you wish to check more than eight frequencies, use
an external controller and the 38.N special functions to create a TRFL
calibration factor data base and the 39.N special functions to re-enter
the calibration factors as they are needed to check each frequency.)
5.
Connect the HP 8902A to the spur source, and press the
Blue
Shift key,
the RECALL (8) key and the
1
digit key. This causes the instrument to
recall the frequency setting and TRFL calibration data stored in register 1.
The HP 8902A now automatically ranges to and displays the level of the
spur. Press the LOG/LIN key if you wish to toggle between Watts and
dBm units.
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