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Model 8902A
Operation
FUNCTIONS
FM, Special Function 2 (Audio Range)
DESCRIPTION
The Measuring Receiver can measure the FM deviation of the tuned input signal. (Special Function
2 enables the instrument to set limits on the range of FM deviation that can be measured.)
FM Measurements are specified for rates from 20
H z
t o 10 kHz for carrier frequencies 10 MHz and
below
(or
whenever the 455 kHz IF is used) and from 20 Hz to 200 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 0.2
Hz to 260 kHz for carriers from
10
to 1300 MHz (1.5 MHz I F only). Peak deviations up to
40
kHz
can be measured on carriers below 10 MHz, and peak deviations up to 400 kHz can be measured
on
carriers above 10 MHz.
The demodulated signal's frequency and distortion can also be measured. (Refer to A irdio Measore-
mcnts on page 3-225.)
PROCEDURE
To make an FM measurement, first tune the instrument to the input signal by selecting Automatic
Operation. Press the FM key.
Select an audio detector: PEAK+, PEAK-, PEAKzt/2, AVG, o r RMS. (The RMS detector, selected
by pressing the Blue Key and AVG key, is accurate in measuring FM, has a reduced bandwidth, and
is usually only used for less audio distortion measurements.)
3- 177
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