Modulation Tests; Modulation Tests Requirements - Fluke 6080A Service Manual

MODULATION TESTS

The following tests use a modulation analyzer to verify modulation accuracy and
residual and incidental modulation of the UUT. The modulation distortion is verified
by measuring the demodulated output of the modulation analyzer with a distortion
analyzer. The internal modulation oscillator frequency is measured using a frequency
counter on the demodulated output of the modulation analyzer. The internal
modulation oscillator amplitude is measured using an RMS voltmeter. Table 4-4 lists
the requirements for the modulation tests.
REQUIREMENTS
PARAMETER
MOD FREQUENCY
AM ACCURACY
AM DISTORTION
RESIDUAL AM
INCIDENTAL FM
FM ACCURACY
FM DISTORTION
RESIDUAL FM
INCIDENTAL AM
REMARKS:
If the UUT fails these performance tests, calibration and/or repair of the associated
circuitry is indicated.
Where residual noise affects the accuracy of the modulation analyzer measurements,
apply correction methods provided by the manufacturer of the modulation analyzer.
The UUT settings in this procedure are chosen to provide strong confidence in the
modulation performance of the UUT throughout its range. If desired, however,
performance may also be checked at other instrument settings.
TEST EQUIPMENT:
Modulation analyzer
Distortion analyzer
Frequency counter
Low-frequency synthesized signal generator (LFSSG)
High-frequency synthesized signal generator (HFSSG)
DVM
RMS Voltmeter
Table 4-4. Modulation Tests Requirements
SPECIFICATION
< ± 0.1 Hz
< ± 7% AM (Amplitude less than 0 dBm)
< 5% at 50% depth at .1, 1 and 10 kHz rates
< 0.01% RMS (-80 dBc) in a 0.04- to 15-kHz bandwidth
< 200 Hz at 1 kHz rate, 50% AM
< ± (5% + 10 Hz) for 1 kHz rate
< 2% THD for deviation < 20 kHz, 1 kHz rate
< 5% for rates of .1, 5, and 50 kHz
RMS in a 0.3- to 3-kHz band: <4 Hz
RMS in a 0.05- to 15-kHz band: <8 Hz
< 1% AM at 1-kHz rate and for deviation < 100 kHz
PERFORMANCE TESTS
4-14.
4-17