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Model 8902A
Display
Resolution
(O/O)
Program
Code
Special
Function
Code
Detector
Selected
Modulation
Range
Peak2 (W)
Operation
AM
MODULATION
OUTPUT
Sensitivity
(Vat/% AM)
FUNCTIONS
Automatic Selection
1 4
RMS
1 4 0
Pk,
Avg
540
Pk,
Avg,
RMS
1100
Pk,
Avg,
RMS
AM, Special Function 2 (Audio Range)
2.0 SPCL
2.0SP
Automatic Selection
2.4 SPCL
2.4SP
0.001
0.1
2.4 SPCL
2.4SP
0.01
0.1
2.1 SPCL
2.1 SP
0.01
0.1
2.2 SPCL
2.2SP
2.3 SPCL
2.3SP
or
or
0.1
0.01
DESCRIPTION
Selecting AM enables the Measuring Receiver to measure the AM depth of the tuned R F input signal.
(Selecting Special Function 2 sets measurement limits on the range of AM depth at the same time a
specific display resolution is set.)
AM measurements are specified for rates from 20
H z
to 10 kHz for carrier frequencies 10 MHz and
below (or whenever the 455 kHz IF is used) and from 20 Hz to 100 kHz for carrier frequencies from
10
to 1300 MHz (1.5 MHz IF only). The corresponding 3 dB audio bandwidths are approximately
0.5
Hz
to 15
kHz for carriers 10 MHz and below (or with the 455 kHz IF) and approximately 0.5
H z
to 260 kHz for carriers from 10 to 1300 MHz (1.5 MHz IF only). (Special Function 6.1 will modify
the lower frequency.) Modulation depths to 99% can be measured.
The demodulated signal's frequency and distortion can also be measured. (Refer to A irdio Mcasirrc-
mcnfs section which starts o n page 3-225.)
PROCEDURE
To make an AM measurement, first tune the instrument to the input signal by selecting AUTO-
MATIC OPERATION. Select AM.
Select an audio detector: PEAKS, PEAK-, PEAK&/2, AVG, o r RMS. The RMS detector (Blue
Key, AVG) is less accurate than the other detectors
in
measuring AM, has a reduced bandwidth, and
is typically only used for audio distortion measurements.
The following table lists the different measurement range limits that can be selected with Special
Function
2:
Tq
filter the dernodiilated signal, select the desired filter. (Refer to I.'i//cm, A irdio for more information
about filters.)
3-161
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