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4-11
Interchangeably
If you plan to use two sensors interchangeably, a second storage
table is available in the HP 8902A's non-volatile memory. This table
is designed to be used in the instrument's Frequency Offset Mode.
(In this mode an external local oscillator (LO), a microwave down-
converter, and a mixer are typically used to extend the frequency
range of the HP 8902A. Refer to your HP 8902A Operation and
Calibration Manual for details on using the Frequency Offset Mode.)
By specifying an offset frequency of zero, the Frequency Offset table can
also be accessed for measurements when an external LO is not being
used. Simply key in 27.3 SPCL and then 0 MHr (the fOFS annunciator
will light in the display). The instrument is now ready to store the
calibration factors (up to 22) for the second Sensor Module in the
Frequency Offset table using the entry procedure shown in Appendix
B.
Once the cal factors have been stored, key in 27.0 SPCL when you wish to
exit the Frequency Offset Mode and use the first Sensor Module. To re-enter
the Frequency Offset Mode and use the second Sensor Module, key in
27.1 SPCL.
No Power Sensor
RF Level (uncalibrated)
To make an uncalibrated RF power measurement without a power
sensor, connect a 50R cable and Type-N connector from the HP 8902A's
INPUT port to the output of your signal source. Press the RF POWER
key. The HP 8902A will make an uncalibrated broadband power
measurement using its RF Peak detector. (Note that the HP 8902A
lights the SPCL key rather than the RF POWER key when it is using
the uncalibrated
RF
Peak detector to measure power.) Although the
accuracy of this measurement is significantly lower than a calibrated
power measurement made using a power sensor, it can be useful as
a means
of
determining if there is any input signal present at the
HP 8902A's input. If a Sensor Module is connected to the HP 8902A,
the RF Peak detector can be selected by keying in 35.0 SPCL.
Tuned Level (uncalibrated)
To make an uncalibrated Tuned Level measurement (either with a Sensor
Module connected to the HP 8902A or with a BNC cable and Type-N
connector connected at the INPUT port) tune the HP 8902A to the
frequency of the input signal and key in 36.0 SPCL. The HP 8902A will
make an uncalibrated Peak Tuned Level measurement. Although the
accuracy of this measurement is significantly lower than a calibrated TRFL
measurement, it can be useful for measuring input signals that are drifting.
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