Model 8640B TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-34. AM SENSITIVITY AND ACCURACY TEST (Cont'd)
FM ................................................................................................................OFF
RANGE.........................................................................................256 - 512 MHz
FREQUENCY TUNE..............................................................................512 MHz
OUTPUT LEVEL..............................................-27 dBm (switch 5 steps ccw from
full cw, vernier full cw)
RF ON/OFF ....................................................................................................ON
2. Set test oscillator for a 1 kHz, 636.39 mVrms signal as read on DVM (90% AM). Disconnect DVM from test
oscillator (leave oscillator connected to generator). Connect DVM to spectrum analyzer's vertical output. Set
calibrated step attenuator to 0 dB.
3. Set spectrum analyzer's resolution bandwidth to 300 kHz, input attenuation to 20 dB, frequency span per division
(scan width) to 20 kHz (tuning stabilizer on), scale to linear, and adjust center frequency and scale reference
level controls to center the 512 MHz signal on the display. Set frequency span per division to 0 Hz and display
smoothing (video filter) to 10 kHz. Peak the trace on the display with the center frequency controls; set the trace
to the center of the display with the reference controls.
NOTE
Step 4 measures the analyzer's dc offset (V
off
) and must be performed to ensure the accuracy of
this test. However if V
off
for the analyzer being used has recently been measured and noted, skip
step 4 and go on to step 5 (and eliminate the calibrated step attenuator from the test setup).
4. Measure analyzer's dc offset (V
off
) by performing steps "a" through "f".
a. Set generator's controls as follows:
Meter Function..........................................................................................LEVEL
AM................................................................................................................OFF
RANGE ................................................................................................2 - 4 MHz
FREQUENCY TUNE .................................................................................3 MHz
b. Set analyzer's center frequency controls to 3 MHz.
c. Adjust analyzer's reference level controls for -500 mVdc indicated on DVM (V
DET 1
)
d. Set step attenuator to 20 dB. Note DVM reading (V
DET 2
)'
e. Calculate V
off
where
V
DET
2- ∝V
DET
1
V
off
= -
1-∝
4-52
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