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Model 8902A
Operation
27. hequency Offset Control.
U s e
this special function when making measurements on down-
converted input signals. (The Measuring Receiver can measure frequencies to
42
GHz when an external
mixer and LO are used to down-convert the input signal. Refer to Jkequency
offset
Control on page
3-255 for requirements of the local oscillator and mixer.) The F'requency Offset Control special function
allows the Measuring Receiver
to
keep track of the frequencies involved in the down-conversion.
27.0 Exit the Frequency Offset Mode.
27.1 Enter the F'requency Offset Mode.
27.2 Display the external LO frequency.
27.3 Prepare to enter and enable the
LO
frequency. h
r entering 27.3 SPCL, enter the frequency
of the
LO (in MHz). Frequencies from 0 to 40700 MHz can be entered.
29.0 SINAD Measurement.
Use this special function to
make
SINAD (Signal to
N o i s e
And
Distortion) measurements on either internally demodulated signals or externally applied audio
signals.
30.0
External Audio RMS Level Measurement.
Use this special function to measure the true rms
level of an audio signal applied to the Measuring Receiver's AUDIO
INPUT
connedor.
31. Tuned RF Level Noise Correction.
U s e
this special function in conjunction with the
IF
Average
Detector (Special h c t i o n s 4 . 4 through 4.7) when making Timed RF Level measurements on low-
level
signals.
The selection of Special Function 31 is maintained through instrument power down (the
Measuring Receiver being turned off and then on).
The Timed
RF
Level measurement calibrates three
RF
input attenuation ranges
to
achieve accurate
low-level measurements. (The Operating Information Pull-Out Curd illustrates these.) When Special
Function 31.1 is enabled, the normal h e d
RF
Level measurement procedure is followed (that is,
stepping down in level and pressing the CALIBRATE key whenever the R E A L annunciator
is
displayed). However, when the Measuring Receiver calibrates the third
RF
range, it causes the sensor
module to switch out the signal from the device-under-test momentarily (placing
5022
at the output).
Then the HP 8902A measures the noise between the
RF
input and the IF Average Detedor circuitry. In
subsequent measurements (in this third range), the Measuring Receiver subtracts the measured noise
from the t o t a l signal-plus-noise to display the measured signal level.
31.0
'Ihm
off noise correction.
31.1
b
on noise correction.
31.2 Display 0
if noise correction
is off
and display 1
if it
is
on.
This special function is not available with firmware date codes 234.1985 and below. (To display the firmware date code, select
42.0
SPCL.) To order
a
ROM
set that contains this s p e c 4 function, contact the nearest HP sales office.
rev.25JUL87
3-281
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