Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-40. FM SENSITIVITY AND ACCURACY TEST (Cont'd)
AM ...............................................................................................................OFF
FM ...............................................................................................................OFF
PEAK DEVIATION ..................................................................................... 5 kHz
PEAK DEVIATION Vernier ....................................................................... Full cw
RANGE ......................................................................................... 256 - 512 MHz
FREQUENCY TUNE ............................................................................. 512 MHz
OUTPUT LEVEL ..................................................................................... -7 dBm
RF ON/OFF ...................................................................................................ON
2. Set reference signal generator for a 513 MHz, CW signal at +13 dBm.
3. Set spectrum analyzer's center frequency controls to 1 MHz, input attenuation to 20 dB, resolution bandwidth to 0.1
kHz, span width per division (scan width) to 1 kHz, and set display to 10 dB per division. Set reference level controls
to put peak of the signal at top (log reference) graticule line on the display.
4. To check external sensitivity, set test oscillator for a 0.7071 Vrms signal (read on DVM) at approximately 2.079 kHz.
Set test generator's FM switch to AC and fine tune test oscillator's frequency for the first carrier null on analyzer's display
(at least 50 dB below the top graticule line). With the frequency counter, measure frequency of modulating signal. It
should be 2.079 kHz +6% (i.e., 5 kHz +6% peak deviation).
1.954 2.204 kHz
5. Use the procedures given above to check the remaining bands by setting the test Signal Generator's RANGE switch
as shown below. As shown in steps 1 through 4, on each range set FM to OFF and tune the generators for a 1 MHz
difference. Set the reference on the analyzer, set FM to AC (with a 0.7071 Vrms modulating signal at approximately
2.079 kHz) and tune the modulating signal's frequency for the first carrier null. The signal's frequency should be as
shown.
RANGE
FREQUENCY
Reference Generator
Mod. Signal Frequency
(MHz)
TUNE
Frequency
(kHz)
128-256
256 MHz
257 MHz
1.954___________ 2.204
64-128
128 MHz
129 MHz
1.954___________ 2.204
32-64
64 MHz
65 MHz
1.954___________ 2.204
16-32
32 MHz
33 MHz
1.954___________ 2.204
8-16
16 MHz
17 MHz
1.954___________ 2.204
4-8
8 MHz
9 MHz
1.954___________ 2.204
2-4
4 MHz
5 MHz
1.954___________ 2.204
1-2
2 MHz
3 MHz
1.954___________ 2.204
4-66
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