
Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-30. INTERNAL MODULATION OSCILLATOR TEST (Cont'd)
PROCEDURE:
1. Connect equipment as shown in Figure 4-16 after setting Signal Generator's controls as follows:
AM ................................................................................................................ INT
AUDIO OUTPUT LEVEL ................................................................ 1V (Standard)
3V (Option 001)
MODULATION .......................................................................................... Full cw
MODULATION FREQUENCY ........................................................ 400 Hz (fixed)
FM ................................................................................................................OFF
2. The frequency counter should read 400 -±8 Hz. The voltmeter should read greater than 1 Vrms on a standard
instrument, 3 Vrms on an Option 001.
392_______408 Hz
Standard: 1.0 Vrms__________
Option 001: 3.0 Vrms_________
3. Set MODULATION FREQUENCY to 1 kHz (fixed). The frequency counter should read 1 kHz ± 20 Hz and the
voltmeter should read as specified above.
980_____________1020 Hz
Standard: 1.0 Vrms____________
Option 001: 3.0 Vrms___________
4. If testing an Option 001, set AUDIO OUTPUT LEVEL to 3V and slowly tune MODULATION FREQUENCY
through its variable range from 20 Hz to 600 kHz. The MODULATION FREQUENCY controls should read within
± 10% of the frequency counter reading at all frequencies.
Frequency:______________±10%
4-31. INTERNAL MODULATION OSCILLATOR DISTORTION TEST (Option 001)
SPECIFICATION:
Total Harmonic Distortion:
<0.25% 400 and 1 kHz fixed tones.
<0.5% 20 Hz to 2 kHz.
<1.0% 2 kHz to 600 kHz.
DESCRIPTION:
A distortion analyzer is used to measure distortion on the output of the variable internal modulation oscillator.
4-45
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